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Current File : /usr/share/doc/qemu-kvm/qemu-doc.txt
QEMU version 4.2.0 User Documentation
*************************************


1 Introduction
  1.1 Features
2 QEMU PC System emulator
  2.1 Introduction
  2.2 Quick Start
  2.3 Invocation
    2.3.1 Standard options
    2.3.2 Block device options
    2.3.3 USB options
    2.3.4 Display options
    2.3.5 i386 target only
    2.3.6 Network options
    2.3.7 Character device options
    2.3.8 Bluetooth(R) options
    2.3.9 TPM device options
    2.3.10 Linux/Multiboot boot specific
    2.3.11 Debug/Expert options
    2.3.12 Generic object creation
    2.3.13 Device URL Syntax
  2.4 Keys in the graphical frontends
  2.5 Keys in the character backend multiplexer
  2.6 QEMU Monitor
    2.6.1 Commands
    2.6.2 Integer expressions
  2.7 CPU models
    2.7.1 Recommendations for KVM CPU model configuration on x86 hosts
      2.7.1.1 Preferred CPU models for Intel x86 hosts
      2.7.1.2 Important CPU features for Intel x86 hosts
      2.7.1.3 Preferred CPU models for AMD x86 hosts
      2.7.1.4 Important CPU features for AMD x86 hosts
      2.7.1.5 Default x86 CPU models
      2.7.1.6 Other non-recommended x86 CPUs
    2.7.2 Supported CPU model configurations on MIPS hosts
      2.7.2.1 Supported CPU models for MIPS32 hosts
      2.7.2.2 Supported CPU models for MIPS64 hosts
      2.7.2.3 Supported CPU models for nanoMIPS hosts
      2.7.2.4 Preferred CPU models for MIPS hosts
    2.7.3 Syntax for configuring CPU models
      2.7.3.1 QEMU command line
      2.7.3.2 Libvirt guest XML
  2.8 Disk Images
    2.8.1 Quick start for disk image creation
    2.8.2 Snapshot mode
    2.8.3 VM snapshots
    2.8.4 ‘qemu-img’ Invocation
    2.8.5 ‘qemu-nbd’ Invocation
    2.8.6 Disk image file formats
      2.8.6.1 Read-only formats
    2.8.7 Using host drives
      2.8.7.1 Linux
      2.8.7.2 Windows
      2.8.7.3 Mac OS X
    2.8.8 Virtual FAT disk images
    2.8.9 NBD access
    2.8.10 Sheepdog disk images
    2.8.11 iSCSI LUNs
    2.8.12 GlusterFS disk images
    2.8.13 Secure Shell (ssh) disk images
    2.8.14 NVMe disk images
    2.8.15 Disk image file locking
  2.9 Network emulation
    2.9.1 Using TAP network interfaces
      2.9.1.1 Linux host
      2.9.1.2 Windows host
    2.9.2 Using the user mode network stack
    2.9.3 Hubs
    2.9.4 Connecting emulated networks between QEMU instances
  2.10 Other Devices
    2.10.1 Inter-VM Shared Memory device
      2.10.1.1 Migration with ivshmem
      2.10.1.2 ivshmem and hugepages
  2.11 Direct Linux Boot
  2.12 USB emulation
    2.12.1 Connecting USB devices
    2.12.2 Using host USB devices on a Linux host
  2.13 VNC security
    2.13.1 Without passwords
    2.13.2 With passwords
    2.13.3 With x509 certificates
    2.13.4 With x509 certificates and client verification
    2.13.5 With x509 certificates, client verification and passwords
    2.13.6 With SASL authentication
    2.13.7 With x509 certificates and SASL authentication
    2.13.8 Configuring SASL mechanisms
  2.14 TLS setup for network services
    2.14.1 Setup the Certificate Authority
    2.14.2 Issuing server certificates
    2.14.3 Issuing client certificates
    2.14.4 TLS x509 credential configuration
    2.14.5 TLS Pre-Shared Keys (PSK)
  2.15 GDB usage
  2.16 Target OS specific information
    2.16.1 Linux
    2.16.2 Windows
      2.16.2.1 SVGA graphic modes support
      2.16.2.2 CPU usage reduction
      2.16.2.3 Windows 2000 disk full problem
      2.16.2.4 Windows 2000 shutdown
      2.16.2.5 Share a directory between Unix and Windows
      2.16.2.6 Windows XP security problem
    2.16.3 MS-DOS and FreeDOS
      2.16.3.1 CPU usage reduction
3 QEMU System emulator for non PC targets
  3.1 PowerPC System emulator
  3.2 Sparc32 System emulator
  3.3 Sparc64 System emulator
  3.4 MIPS System emulator
    3.4.1 nanoMIPS System emulator
  3.5 ARM System emulator
  3.6 ColdFire System emulator
  3.7 Cris System emulator
  3.8 Microblaze System emulator
  3.9 SH4 System emulator
  3.10 Xtensa System emulator
4 QEMU User space emulator
  4.1 Supported Operating Systems
  4.2 Features
  4.3 Linux User space emulator
    4.3.1 Quick Start
    4.3.2 Wine launch
    4.3.3 Command line options
    4.3.4 Other binaries
  4.4 BSD User space emulator
    4.4.1 BSD Status
    4.4.2 Quick Start
    4.4.3 Command line options
5 System requirements
  5.1 KVM kernel module
6 Security
  6.1 Overview
  6.2 Security Requirements
    6.2.1 Virtualization Use Case
    6.2.2 Non-virtualization Use Case
  6.3 Architecture
    6.3.1 Guest Isolation
    6.3.2 Principle of Least Privilege
    6.3.3 Isolation mechanisms
  6.4 Sensitive configurations
    6.4.1 Monitor console (QMP and HMP)
Appendix A Implementation notes
  A.1 CPU emulation
    A.1.1 x86 and x86-64 emulation
    A.1.2 ARM emulation
    A.1.3 MIPS emulation
    A.1.4 PowerPC emulation
    A.1.5 Sparc32 and Sparc64 emulation
    A.1.6 Xtensa emulation
  A.2 Managed start up options
Appendix B Deprecated features
  B.1 System emulator command line arguments
    B.1.1 -machine enforce-config-section=on|off (since 3.1)
    B.1.2 -no-kvm (since 1.3.0)
    B.1.3 -usbdevice (since 2.10.0)
    B.1.4 -drive file=json:{...{’driver’:’file’}} (since 3.0)
    B.1.5 -net ...,name=NAME (since 3.1)
    B.1.6 -smp (invalid topologies) (since 3.1)
    B.1.7 -vnc acl (since 4.0.0)
    B.1.8 QEMU_AUDIO_ environment variables and -audio-help (since 4.0)
    B.1.9 Creating sound card devices and vnc without audiodev= property (since 4.2)
    B.1.10 -mon ...,control=readline,pretty=on|off (since 4.1)
    B.1.11 -realtime (since 4.1)
    B.1.12 -virtfs_synth (since 4.1)
    B.1.13 -numa node,mem=SIZE (since 4.1)
    B.1.14 -numa node (without memory specified) (since 4.1)
    B.1.15 -mem-path fallback to RAM (since 4.1)
    B.1.16 RISC-V -bios (since 4.1)
  B.2 QEMU Machine Protocol (QMP) commands
    B.2.1 change (since 2.5.0)
    B.2.2 migrate_set_downtime and migrate_set_speed (since 2.8.0)
    B.2.3 migrate-set-cache-size and query-migrate-cache-size (since 2.11.0)
    B.2.4 query-block result field dirty-bitmaps[i].status (since 4.0)
    B.2.5 query-block result field dirty-bitmaps (Since 4.2)
    B.2.6 query-cpus (since 2.12.0)
    B.2.7 query-cpus-fast "arch" output member (since 3.0.0)
    B.2.8 cpu-add (since 4.0)
    B.2.9 query-events (since 4.0)
    B.2.10 chardev client socket with ’wait’ option (since 4.0)
  B.3 Human Monitor Protocol (HMP) commands
    B.3.1 The hub_id parameter of ’hostfwd_add’ / ’hostfwd_remove’ (since 3.1)
    B.3.2 cpu-add (since 4.0)
    B.3.3 acl_show, acl_reset, acl_policy, acl_add, acl_remove (since 4.0.0)
  B.4 Guest Emulator ISAs
    B.4.1 RISC-V ISA privledge specification version 1.09.1 (since 4.1)
  B.5 System emulator CPUS
    B.5.1 RISC-V ISA CPUs (since 4.1)
    B.5.2 RISC-V ISA CPUs (since 4.1)
  B.6 System emulator devices
    B.6.1 bluetooth (since 3.1)
    B.6.2 ide-drive (since 4.2)
    B.6.3 scsi-disk (since 4.2)
  B.7 System emulator machines
    B.7.1 pc-0.12, pc-0.13, pc-0.14 and pc-0.15 (since 4.0)
    B.7.2 prep (PowerPC) (since 3.1)
    B.7.3 spike_v1.9.1 and spike_v1.10 (since 4.1)
  B.8 Device options
    B.8.1 Block device options
      B.8.1.1 "backing": "" (since 2.12.0)
      B.8.1.2 rbd keyvalue pair encoded filenames: "" (since 3.1.0)
  B.9 Related binaries
    B.9.1 qemu-nbd –partition (since 4.0.0)
    B.9.2 qemu-img convert -n -o (since 4.2.0)
  B.10 Build system
    B.10.1 Python 2 support (since 4.1.0)
  B.11 Backwards compatibility
    B.11.1 Runnability guarantee of CPU models (since 4.1.0)
Appendix C Recently removed features
  C.1 QEMU Machine Protocol (QMP) commands
    C.1.1 block-dirty-bitmap-add "autoload" parameter (since 4.2.0)
Appendix D Supported build platforms
  D.1 Linux OS
  D.2 Windows
  D.3 macOS
  D.4 FreeBSD
  D.5 NetBSD
  D.6 OpenBSD
Appendix E License
Appendix F Index
  F.1 Concept Index
  F.2 Function Index
  F.3 Keystroke Index
  F.4 Program Index
  F.5 Data Type Index
  F.6 Variable Index
1 Introduction
**************

1.1 Features
============

QEMU is a FAST! processor emulator using dynamic translation to achieve
good emulation speed.

QEMU has two operating modes:

   • Full system emulation.  In this mode, QEMU emulates a full system
     (for example a PC), including one or several processors and various
     peripherals.  It can be used to launch different Operating Systems
     without rebooting the PC or to debug system code.

   • User mode emulation.  In this mode, QEMU can launch processes
     compiled for one CPU on another CPU. It can be used to launch the
     Wine Windows API emulator (<https://www.winehq.org>) or to ease
     cross-compilation and cross-debugging.

QEMU has the following features:

   • QEMU can run without a host kernel driver and yet gives acceptable
     performance.  It uses dynamic translation to native code for
     reasonable speed, with support for self-modifying code and precise
     exceptions.

   • It is portable to several operating systems (GNU/Linux, *BSD, Mac
     OS X, Windows) and architectures.

   • It performs accurate software emulation of the FPU.

QEMU user mode emulation has the following features:
   • Generic Linux system call converter, including most ioctls.

   • clone() emulation using native CPU clone() to use Linux scheduler
     for threads.

   • Accurate signal handling by remapping host signals to target
     signals.

QEMU full system emulation has the following features:
   • QEMU uses a full software MMU for maximum portability.

   • QEMU can optionally use an in-kernel accelerator, like kvm.  The
     accelerators execute most of the guest code natively, while
     continuing to emulate the rest of the machine.

   • Various hardware devices can be emulated and in some cases, host
     devices (e.g.  serial and parallel ports, USB, drives) can be used
     transparently by the guest Operating System.  Host device
     passthrough can be used for talking to external physical
     peripherals (e.g.  a webcam, modem or tape drive).

   • Symmetric multiprocessing (SMP) support.  Currently, an in-kernel
     accelerator is required to use more than one host CPU for
     emulation.

2 QEMU PC System emulator
*************************

2.1 Introduction
================

The QEMU PC System emulator simulates the following peripherals:

   − i440FX host PCI bridge and PIIX3 PCI to ISA bridge
   − Cirrus CLGD 5446 PCI VGA card or dummy VGA card with Bochs VESA
     extensions (hardware level, including all non standard modes).
   − PS/2 mouse and keyboard
   − 2 PCI IDE interfaces with hard disk and CD-ROM support
   − Floppy disk
   − PCI and ISA network adapters
   − Serial ports
   − IPMI BMC, either and internal or external one
   − Creative SoundBlaster 16 sound card
   − ENSONIQ AudioPCI ES1370 sound card
   − Intel 82801AA AC97 Audio compatible sound card
   − Intel HD Audio Controller and HDA codec
   − Adlib (OPL2) - Yamaha YM3812 compatible chip
   − Gravis Ultrasound GF1 sound card
   − CS4231A compatible sound card
   − PCI UHCI, OHCI, EHCI or XHCI USB controller and a virtual USB-1.1
     hub.

SMP is supported with up to 255 CPUs.

QEMU uses the PC BIOS from the Seabios project and the Plex86/Bochs LGPL
VGA BIOS.

QEMU uses YM3812 emulation by Tatsuyuki Satoh.

QEMU uses GUS emulation (GUSEMU32 <http://www.deinmeister.de/gusemu/>)
by Tibor "TS" Schütz.

Note that, by default, GUS shares IRQ(7) with parallel ports and so QEMU
must be told to not have parallel ports to have working GUS.

     qemu-kvm dos.img -soundhw gus -parallel none

Alternatively:
     qemu-kvm dos.img -device gus,irq=5

Or some other unclaimed IRQ.

CS4231A is the chip used in Windows Sound System and GUSMAX products

2.2 Quick Start
===============

Download and uncompress a hard disk image with Linux installed (e.g.
‘linux.img’) and type:

     qemu-kvm linux.img

Linux should boot and give you a prompt.

2.3 Invocation
==============

     qemu-kvm [OPTIONS] [DISK_IMAGE]

DISK_IMAGE is a raw hard disk image for IDE hard disk 0.  Some targets
do not need a disk image.

2.3.1 Standard options
----------------------

‘-h’
     Display help and exit
‘-version’
     Display version information and exit
‘-machine [type=]NAME[,prop=VALUE[,...]]’
     Select the emulated machine by NAME.  Use ‘-machine help’ to list
     available machines.

     For architectures which aim to support live migration compatibility
     across releases, each release will introduce a new versioned
     machine type.  For example, the 2.8.0 release introduced machine
     types “pc-i440fx-2.8” and “pc-q35-2.8” for the x86_64/i686
     architectures.

     To allow live migration of guests from QEMU version 2.8.0, to QEMU
     version 2.9.0, the 2.9.0 version must support the “pc-i440fx-2.8”
     and “pc-q35-2.8” machines too.  To allow users live migrating VMs
     to skip multiple intermediate releases when upgrading, new releases
     of QEMU will support machine types from many previous versions.

     Supported machine properties are:
     ‘accel=ACCELS1[:ACCELS2[:...]]’
          This is used to enable an accelerator.  Depending on the
          target architecture, kvm, xen, hax, hvf, whpx or tcg can be
          available.  By default, tcg is used.  If there is more than
          one accelerator specified, the next one is used if the
          previous one fails to initialize.
     ‘kernel_irqchip=on|off’
          Controls in-kernel irqchip support for the chosen accelerator
          when available.
     ‘gfx_passthru=on|off’
          Enables IGD GFX passthrough support for the chosen machine
          when available.
     ‘vmport=on|off|auto’
          Enables emulation of VMWare IO port, for vmmouse etc.  auto
          says to select the value based on accel.  For accel=xen the
          default is off otherwise the default is on.
     ‘kvm_shadow_mem=size’
          Defines the size of the KVM shadow MMU.
     ‘dump-guest-core=on|off’
          Include guest memory in a core dump.  The default is on.
     ‘mem-merge=on|off’
          Enables or disables memory merge support.  This feature, when
          supported by the host, de-duplicates identical memory pages
          among VMs instances (enabled by default).
     ‘aes-key-wrap=on|off’
          Enables or disables AES key wrapping support on s390-ccw
          hosts.  This feature controls whether AES wrapping keys will
          be created to allow execution of AES cryptographic functions.
          The default is on.
     ‘dea-key-wrap=on|off’
          Enables or disables DEA key wrapping support on s390-ccw
          hosts.  This feature controls whether DEA wrapping keys will
          be created to allow execution of DEA cryptographic functions.
          The default is on.
     ‘nvdimm=on|off’
          Enables or disables NVDIMM support.  The default is off.
     ‘enforce-config-section=on|off’
          If ‘enforce-config-section’ is set to ON, force migration code
          to send configuration section even if the machine-type sets
          the ‘migration.send-configuration’ property to OFF.  NOTE:
          this parameter is deprecated.  Please use ‘-global’
          ‘migration.send-configuration’=ON|OFF instead.
     ‘memory-encryption=’
          Memory encryption object to use.  The default is none.
     ‘hmat=on|off’
          Enables or disables ACPI Heterogeneous Memory Attribute Table
          (HMAT) support.  The default is off.
‘-cpu MODEL’
     Select CPU model (‘-cpu help’ for list and additional feature
     selection)
‘-accel NAME[,prop=VALUE[,...]]’
     This is used to enable an accelerator.  Depending on the target
     architecture, kvm, xen, hax, hvf, whpx or tcg can be available.  By
     default, tcg is used.  If there is more than one accelerator
     specified, the next one is used if the previous one fails to
     initialize.
     ‘thread=single|multi’
          Controls number of TCG threads.  When the TCG is
          multi-threaded there will be one thread per vCPU therefor
          taking advantage of additional host cores.  The default is to
          enable multi-threading where both the back-end and front-ends
          support it and no incompatible TCG features have been enabled
          (e.g.  icount/replay).
‘-smp [cpus=]N[,cores=CORES][,threads=THREADS][,dies=dies][,sockets=SOCKETS][,maxcpus=MAXCPUS]’
     Simulate an SMP system with N CPUs.  On the PC target, up to 255
     CPUs are supported.  On Sparc32 target, Linux limits the number of
     usable CPUs to 4.  For the PC target, the number of CORES per die,
     the number of THREADS per cores, the number of DIES per packages
     and the total number of SOCKETS can be specified.  Missing values
     will be computed.  If any on the three values is given, the total
     number of CPUs N can be omitted.  MAXCPUS specifies the maximum
     number of hotpluggable CPUs.
‘-numa node[,mem=SIZE][,cpus=FIRSTCPU[-LASTCPU]][,nodeid=NODE][,initiator=INITIATOR]’
‘-numa node[,memdev=ID][,cpus=FIRSTCPU[-LASTCPU]][,nodeid=NODE][,initiator=INITIATOR]’
‘-numa dist,src=SOURCE,dst=DESTINATION,val=DISTANCE’
‘-numa cpu,node-id=NODE[,socket-id=X][,core-id=Y][,thread-id=Z]’
‘-numa hmat-lb,initiator=NODE,target=NODE,hierarchy=HIERARCHY,data-type=TPYE[,latency=LAT][,bandwidth=BW]’
‘-numa hmat-cache,node-id=NODE,size=SIZE,level=LEVEL[,associativity=STR][,policy=STR][,line=SIZE]’
     Define a NUMA node and assign RAM and VCPUs to it.  Set the NUMA
     distance from a source node to a destination node.  Set the ACPI
     Heterogeneous Memory Attributes for the given nodes.

     Legacy VCPU assignment uses ‘cpus’ option where FIRSTCPU and
     LASTCPU are CPU indexes.  Each ‘cpus’ option represent a contiguous
     range of CPU indexes (or a single VCPU if LASTCPU is omitted).  A
     non-contiguous set of VCPUs can be represented by providing
     multiple ‘cpus’ options.  If ‘cpus’ is omitted on all nodes, VCPUs
     are automatically split between them.

     For example, the following option assigns VCPUs 0, 1, 2 and 5 to a
     NUMA node:
          -numa node,cpus=0-2,cpus=5

     ‘cpu’ option is a new alternative to ‘cpus’ option which uses
     ‘socket-id|core-id|thread-id’ properties to assign CPU objects to a
     NODE using topology layout properties of CPU. The set of properties
     is machine specific, and depends on used machine type/‘smp’
     options.  It could be queried with ‘hotpluggable-cpus’ monitor
     command.  ‘node-id’ property specifies NODE to which CPU object
     will be assigned, it’s required for NODE to be declared with ‘node’
     option before it’s used with ‘cpu’ option.

     For example:
          -M pc \
          -smp 1,sockets=2,maxcpus=2 \
          -numa node,nodeid=0 -numa node,nodeid=1 \
          -numa cpu,node-id=0,socket-id=0 -numa cpu,node-id=1,socket-id=1

     ‘mem’ assigns a given RAM amount to a node.  ‘memdev’ assigns RAM
     from a given memory backend device to a node.  If ‘mem’ and
     ‘memdev’ are omitted in all nodes, RAM is split equally between
     them.

     ‘mem’ and ‘memdev’ are mutually exclusive.  Furthermore, if one
     node uses ‘memdev’, all of them have to use it.

     ‘initiator’ is an additional option that points to an INITIATOR
     NUMA node that has best performance (the lowest latency or largest
     bandwidth) to this NUMA NODE.  Note that this option can be set
     only when the machine property ’hmat’ is set to ’on’.

     Following example creates a machine with 2 NUMA nodes, node 0 has
     CPU. node 1 has only memory, and its initiator is node 0.  Note
     that because node 0 has CPU, by default the initiator of node 0 is
     itself and must be itself.
          -machine hmat=on \
          -m 2G,slots=2,maxmem=4G \
          -object memory-backend-ram,size=1G,id=m0 \
          -object memory-backend-ram,size=1G,id=m1 \
          -numa node,nodeid=0,memdev=m0 \
          -numa node,nodeid=1,memdev=m1,initiator=0 \
          -smp 2,sockets=2,maxcpus=2  \
          -numa cpu,node-id=0,socket-id=0 \
          -numa cpu,node-id=0,socket-id=1

     SOURCE and DESTINATION are NUMA node IDs.  DISTANCE is the NUMA
     distance from SOURCE to DESTINATION.  The distance from a node to
     itself is always 10.  If any pair of nodes is given a distance,
     then all pairs must be given distances.  Although, when distances
     are only given in one direction for each pair of nodes, then the
     distances in the opposite directions are assumed to be the same.
     If, however, an asymmetrical pair of distances is given for even
     one node pair, then all node pairs must be provided distance values
     for both directions, even when they are symmetrical.  When a node
     is unreachable from another node, set the pair’s distance to 255.

     Note that the -‘numa’ option doesn’t allocate any of the specified
     resources, it just assigns existing resources to NUMA nodes.  This
     means that one still has to use the ‘-m’, ‘-smp’ options to
     allocate RAM and VCPUs respectively.

     Use ‘hmat-lb’ to set System Locality Latency and Bandwidth
     Information between initiator and target NUMA nodes in ACPI
     Heterogeneous Attribute Memory Table (HMAT). Initiator NUMA node
     can create memory requests, usually it has one or more processors.
     Target NUMA node contains addressable memory.

     In ‘hmat-lb’ option, NODE are NUMA node IDs.  HIERARCHY is the
     memory hierarchy of the target NUMA node: if HIERARCHY is ’memory’,
     the structure represents the memory performance; if HIERARCHY is
     ’first-level|second-level|third-level’, this structure represents
     aggregated performance of memory side caches for each domain.  TYPE
     of ’data-type’ is type of data represented by this structure
     instance: if ’hierarchy’ is ’memory’, ’data-type’ is
     ’access|read|write’ latency or ’access|read|write’ bandwidth of the
     target memory; if ’hierarchy’ is
     ’first-level|second-level|third-level’, ’data-type’ is
     ’access|read|write’ hit latency or ’access|read|write’ hit
     bandwidth of the target memory side cache.

     LAT is latency value in nanoseconds.  BW is bandwidth value, the
     possible value and units are NUM[M|G|T], mean that the bandwidth
     value are NUM byte per second (or MB/s, GB/s or TB/s depending on
     used suffix).  Note that if latency or bandwidth value is 0, means
     the corresponding latency or bandwidth information is not provided.

     In ‘hmat-cache’ option, NODE-ID is the NUMA-id of the memory
     belongs.  SIZE is the size of memory side cache in bytes.  LEVEL is
     the cache level described in this structure, note that the cache
     level 0 should not be used with ‘hmat-cache’ option.  ASSOCIATIVITY
     is the cache associativity, the possible value is
     ’none/direct(direct-mapped)/complex(complex cache indexing)’.
     POLICY is the write policy.  LINE is the cache Line size in bytes.

     For example, the following options describe 2 NUMA nodes.  Node 0
     has 2 cpus and a ram, node 1 has only a ram.  The processors in
     node 0 access memory in node 0 with access-latency 5 nanoseconds,
     access-bandwidth is 200 MB/s; The processors in NUMA node 0 access
     memory in NUMA node 1 with access-latency 10 nanoseconds,
     access-bandwidth is 100 MB/s.  And for memory side cache
     information, NUMA node 0 and 1 both have 1 level memory cache, size
     is 10KB, policy is write-back, the cache Line size is 8 bytes:
          -machine hmat=on \
          -m 2G \
          -object memory-backend-ram,size=1G,id=m0 \
          -object memory-backend-ram,size=1G,id=m1 \
          -smp 2 \
          -numa node,nodeid=0,memdev=m0 \
          -numa node,nodeid=1,memdev=m1,initiator=0 \
          -numa cpu,node-id=0,socket-id=0 \
          -numa cpu,node-id=0,socket-id=1 \
          -numa hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-latency,latency=5 \
          -numa hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-bandwidth,bandwidth=200M \
          -numa hmat-lb,initiator=0,target=1,hierarchy=memory,data-type=access-latency,latency=10 \
          -numa hmat-lb,initiator=0,target=1,hierarchy=memory,data-type=access-bandwidth,bandwidth=100M \
          -numa hmat-cache,node-id=0,size=10K,level=1,associativity=direct,policy=write-back,line=8 \
          -numa hmat-cache,node-id=1,size=10K,level=1,associativity=direct,policy=write-back,line=8

‘-add-fd fd=FD,set=SET[,opaque=OPAQUE]’

     Add a file descriptor to an fd set.  Valid options are:

     ‘fd=FD’
          This option defines the file descriptor of which a duplicate
          is added to fd set.  The file descriptor cannot be stdin,
          stdout, or stderr.
     ‘set=SET’
          This option defines the ID of the fd set to add the file
          descriptor to.
     ‘opaque=OPAQUE’
          This option defines a free-form string that can be used to
          describe FD.

     You can open an image using pre-opened file descriptors from an fd
     set:
          qemu-kvm \
          -add-fd fd=3,set=2,opaque="rdwr:/path/to/file" \
          -add-fd fd=4,set=2,opaque="rdonly:/path/to/file" \
          -drive file=/dev/fdset/2,index=0,media=disk
‘-set GROUP.ID.ARG=VALUE’
     Set parameter ARG for item ID of type GROUP
‘-global DRIVER.PROP=VALUE’
‘-global driver=DRIVER,property=PROPERTY,value=VALUE’
     Set default value of DRIVER’s property PROP to VALUE, e.g.:

          qemu-kvm -global ide-hd.physical_block_size=4096 disk-image.img

     In particular, you can use this to set driver properties for
     devices which are created automatically by the machine model.  To
     create a device which is not created automatically and set
     properties on it, use -‘device’.

     -global DRIVER.PROP=VALUE is shorthand for -global
     driver=DRIVER,property=PROP,value=VALUE.  The longhand syntax works
     even when DRIVER contains a dot.
‘-boot [order=DRIVES][,once=DRIVES][,menu=on|off][,splash=SP_NAME][,splash-time=SP_TIME][,reboot-timeout=RB_TIMEOUT][,strict=on|off]’
     Specify boot order DRIVES as a string of drive letters.  Valid
     drive letters depend on the target architecture.  The x86 PC uses:
     a, b (floppy 1 and 2), c (first hard disk), d (first CD-ROM), n-p
     (Etherboot from network adapter 1-4), hard disk boot is the
     default.  To apply a particular boot order only on the first
     startup, specify it via ‘once’.  Note that the ‘order’ or ‘once’
     parameter should not be used together with the ‘bootindex’ property
     of devices, since the firmware implementations normally do not
     support both at the same time.

     Interactive boot menus/prompts can be enabled via ‘menu=on’ as far
     as firmware/BIOS supports them.  The default is non-interactive
     boot.

     A splash picture could be passed to bios, enabling user to show it
     as logo, when option splash=SP_NAME is given and menu=on, If
     firmware/BIOS supports them.  Currently Seabios for X86 system
     support it.  limitation: The splash file could be a jpeg file or a
     BMP file in 24 BPP format(true color).  The resolution should be
     supported by the SVGA mode, so the recommended is 320x240, 640x480,
     800x640.

     A timeout could be passed to bios, guest will pause for RB_TIMEOUT
     ms when boot failed, then reboot.  If ‘reboot-timeout’ is not set,
     guest will not reboot by default.  Currently Seabios for X86 system
     support it.

     Do strict boot via ‘strict=on’ as far as firmware/BIOS supports it.
     This only effects when boot priority is changed by bootindex
     options.  The default is non-strict boot.

          # try to boot from network first, then from hard disk
          qemu-kvm -boot order=nc
          # boot from CD-ROM first, switch back to default order after reboot
          qemu-kvm -boot once=d
          # boot with a splash picture for 5 seconds.
          qemu-kvm -boot menu=on,splash=/root/boot.bmp,splash-time=5000

     Note: The legacy format ’-boot DRIVES’ is still supported but its
     use is discouraged as it may be removed from future versions.
‘-m [size=]MEGS[,slots=n,maxmem=size]’
     Sets guest startup RAM size to MEGS megabytes.  Default is 128 MiB.
     Optionally, a suffix of “M” or “G” can be used to signify a value
     in megabytes or gigabytes respectively.  Optional pair SLOTS,
     MAXMEM could be used to set amount of hotpluggable memory slots and
     maximum amount of memory.  Note that MAXMEM must be aligned to the
     page size.

     For example, the following command-line sets the guest startup RAM
     size to 1GB, creates 3 slots to hotplug additional memory and sets
     the maximum memory the guest can reach to 4GB:

          qemu-kvm -m 1G,slots=3,maxmem=4G

     If SLOTS and MAXMEM are not specified, memory hotplug won’t be
     enabled and the guest startup RAM will never increase.
‘-mem-path PATH’
     Allocate guest RAM from a temporarily created file in PATH.
‘-mem-prealloc’
     Preallocate memory when using -mem-path.
‘-k LANGUAGE’
     Use keyboard layout LANGUAGE (for example ‘fr’ for French).  This
     option is only needed where it is not easy to get raw PC keycodes
     (e.g.  on Macs, with some X11 servers or with a VNC or curses
     display).  You don’t normally need to use it on PC/Linux or
     PC/Windows hosts.

     The available layouts are:
          ar  de-ch  es  fo     fr-ca  hu  ja  mk     no  pt-br  sv
          da  en-gb  et  fr     fr-ch  is  lt  nl     pl  ru     th
          de  en-us  fi  fr-be  hr     it  lv  nl-be  pt  sl     tr

     The default is ‘en-us’.
‘-audio-help’
     Will show the -audiodev equivalent of the currently specified
     (deprecated) environment variables.
‘-audiodev [driver=]DRIVER,id=ID[,PROP[=VALUE][,...]]’
     Adds a new audio backend DRIVER identified by ID.  There are global
     and driver specific properties.  Some values can be set differently
     for input and output, they’re marked with ‘in|out.’.  You can set
     the input’s property with ‘in.PROP’ and the output’s property with
     ‘out.PROP’.  For example:
          -audiodev alsa,id=example,in.frequency=44110,out.frequency=8000
          -audiodev alsa,id=example,out.channels=1 # leaves in.channels unspecified

     NOTE: parameter validation is known to be incomplete, in many cases
     specifying an invalid option causes QEMU to print an error message
     and continue emulation without sound.

     Valid global options are:

     ‘id=IDENTIFIER’
          Identifies the audio backend.

     ‘timer-period=PERIOD’
          Sets the timer PERIOD used by the audio subsystem in
          microseconds.  Default is 10000 (10 ms).

     ‘in|out.mixing-engine=on|off’
          Use QEMU’s mixing engine to mix all streams inside QEMU and
          convert audio formats when not supported by the backend.  When
          off, FIXED-SETTINGS must be off too.  Note that disabling this
          option means that the selected backend must support multiple
          streams and the audio formats used by the virtual cards,
          otherwise you’ll get no sound.  It’s not recommended to
          disable this option unless you want to use 5.1 or 7.1 audio,
          as mixing engine only supports mono and stereo audio.  Default
          is on.

     ‘in|out.fixed-settings=on|off’
          Use fixed settings for host audio.  When off, it will change
          based on how the guest opens the sound card.  In this case you
          must not specify FREQUENCY, CHANNELS or FORMAT.  Default is
          on.

     ‘in|out.frequency=FREQUENCY’
          Specify the FREQUENCY to use when using FIXED-SETTINGS.
          Default is 44100Hz.

     ‘in|out.channels=CHANNELS’
          Specify the number of CHANNELS to use when using
          FIXED-SETTINGS.  Default is 2 (stereo).

     ‘in|out.format=FORMAT’
          Specify the sample FORMAT to use when using FIXED-SETTINGS.
          Valid values are: ‘s8’, ‘s16’, ‘s32’, ‘u8’, ‘u16’, ‘u32’.
          Default is ‘s16’.

     ‘in|out.voices=VOICES’
          Specify the number of VOICES to use.  Default is 1.

     ‘in|out.buffer-length=USECS’
          Sets the size of the buffer in microseconds.

‘-audiodev none,id=ID[,PROP[=VALUE][,...]]’
     Creates a dummy backend that discards all outputs.  This backend
     has no backend specific properties.

‘-audiodev alsa,id=ID[,PROP[=VALUE][,...]]’
     Creates backend using the ALSA. This backend is only available on
     Linux.

     ALSA specific options are:

     ‘in|out.dev=DEVICE’
          Specify the ALSA DEVICE to use for input and/or output.
          Default is ‘default’.

     ‘in|out.period-length=USECS’
          Sets the period length in microseconds.

     ‘in|out.try-poll=on|off’
          Attempt to use poll mode with the device.  Default is on.

     ‘threshold=THRESHOLD’
          Threshold (in microseconds) when playback starts.  Default is
          0.

‘-audiodev coreaudio,id=ID[,PROP[=VALUE][,...]]’
     Creates a backend using Apple’s Core Audio.  This backend is only
     available on Mac OS and only supports playback.

     Core Audio specific options are:

     ‘in|out.buffer-count=COUNT’
          Sets the COUNT of the buffers.

‘-audiodev dsound,id=ID[,PROP[=VALUE][,...]]’
     Creates a backend using Microsoft’s DirectSound.  This backend is
     only available on Windows and only supports playback.

     DirectSound specific options are:

     ‘latency=USECS’
          Add extra USECS microseconds latency to playback.  Default is
          10000 (10 ms).

‘-audiodev oss,id=ID[,PROP[=VALUE][,...]]’
     Creates a backend using OSS. This backend is available on most
     Unix-like systems.

     OSS specific options are:

     ‘in|out.dev=DEVICE’
          Specify the file name of the OSS DEVICE to use.  Default is
          ‘/dev/dsp’.

     ‘in|out.buffer-count=COUNT’
          Sets the COUNT of the buffers.

     ‘in|out.try-poll=on|of’
          Attempt to use poll mode with the device.  Default is on.

     ‘try-mmap=on|off’
          Try using memory mapped device access.  Default is off.

     ‘exclusive=on|off’
          Open the device in exclusive mode (vmix won’t work in this
          case).  Default is off.

     ‘dsp-policy=POLICY’
          Sets the timing policy (between 0 and 10, where smaller number
          means smaller latency but higher CPU usage).  Use -1 to use
          buffer sizes specified by ‘buffer’ and ‘buffer-count’.  This
          option is ignored if you do not have OSS 4.  Default is 5.

‘-audiodev pa,id=ID[,PROP[=VALUE][,...]]’
     Creates a backend using PulseAudio.  This backend is available on
     most systems.

     PulseAudio specific options are:

     ‘server=SERVER’
          Sets the PulseAudio SERVER to connect to.

     ‘in|out.name=SINK’
          Use the specified source/sink for recording/playback.

     ‘in|out.latency=USECS’
          Desired latency in microseconds.  The PulseAudio server will
          try to honor this value but actual latencies may be lower or
          higher.

‘-audiodev sdl,id=ID[,PROP[=VALUE][,...]]’
     Creates a backend using SDL. This backend is available on most
     systems, but you should use your platform’s native backend if
     possible.  This backend has no backend specific properties.

‘-audiodev spice,id=ID[,PROP[=VALUE][,...]]’
     Creates a backend that sends audio through SPICE. This backend
     requires ‘-spice’ and automatically selected in that case, so
     usually you can ignore this option.  This backend has no backend
     specific properties.

‘-audiodev wav,id=ID[,PROP[=VALUE][,...]]’
     Creates a backend that writes audio to a WAV file.

     Backend specific options are:

     ‘path=PATH’
          Write recorded audio into the specified file.  Default is
          ‘qemu.wav’.

‘-soundhw CARD1[,CARD2,...] or -soundhw all’
     Enable audio and selected sound hardware.  Use ’help’ to print all
     available sound hardware.  For example:

          qemu-kvm -soundhw sb16,adlib disk.img
          qemu-kvm -soundhw es1370 disk.img
          qemu-kvm -soundhw ac97 disk.img
          qemu-kvm -soundhw hda disk.img
          qemu-kvm -soundhw all disk.img
          qemu-kvm -soundhw help

     Note that Linux’s i810_audio OSS kernel (for AC97) module might
     require manually specifying clocking.

          modprobe i810_audio clocking=48000
‘-device DRIVER[,PROP[=VALUE][,...]]’
     Add device DRIVER.  PROP=VALUE sets driver properties.  Valid
     properties depend on the driver.  To get help on possible drivers
     and properties, use ‘-device help’ and ‘-device DRIVER,help’.

     Some drivers are:
‘-device ipmi-bmc-sim,id=ID[,slave_addr=VAL][,sdrfile=FILE][,furareasize=VAL][,furdatafile=FILE][,guid=UUID]’

     Add an IPMI BMC. This is a simulation of a hardware management
     interface processor that normally sits on a system.  It provides a
     watchdog and the ability to reset and power control the system.
     You need to connect this to an IPMI interface to make it useful

     The IPMI slave address to use for the BMC. The default is 0x20.
     This address is the BMC’s address on the I2C network of management
     controllers.  If you don’t know what this means, it is safe to
     ignore it.

     ‘id=ID’
          The BMC id for interfaces to use this device.
     ‘slave_addr=VAL’
          Define slave address to use for the BMC. The default is 0x20.
     ‘sdrfile=FILE’
          file containing raw Sensor Data Records (SDR) data.  The
          default is none.
     ‘fruareasize=VAL’
          size of a Field Replaceable Unit (FRU) area.  The default is
          1024.
     ‘frudatafile=FILE’
          file containing raw Field Replaceable Unit (FRU) inventory
          data.  The default is none.
     ‘guid=UUID’
          value for the GUID for the BMC, in standard UUID format.  If
          this is set, get "Get GUID" command to the BMC will return it.
          Otherwise "Get GUID" will return an error.

‘-device ipmi-bmc-extern,id=ID,chardev=ID[,slave_addr=VAL]’

     Add a connection to an external IPMI BMC simulator.  Instead of
     locally emulating the BMC like the above item, instead connect to
     an external entity that provides the IPMI services.

     A connection is made to an external BMC simulator.  If you do this,
     it is strongly recommended that you use the "reconnect=" chardev
     option to reconnect to the simulator if the connection is lost.
     Note that if this is not used carefully, it can be a security
     issue, as the interface has the ability to send resets, NMIs, and
     power off the VM. It’s best if QEMU makes a connection to an
     external simulator running on a secure port on localhost, so
     neither the simulator nor QEMU is exposed to any outside network.

     See the "lanserv/README.vm" file in the OpenIPMI library for more
     details on the external interface.

‘-device isa-ipmi-kcs,bmc=ID[,ioport=VAL][,irq=VAL]’

     Add a KCS IPMI interafce on the ISA bus.  This also adds a
     corresponding ACPI and SMBIOS entries, if appropriate.

     ‘bmc=ID’
          The BMC to connect to, one of ipmi-bmc-sim or ipmi-bmc-extern
          above.
     ‘ioport=VAL’
          Define the I/O address of the interface.  The default is 0xca0
          for KCS.
     ‘irq=VAL’
          Define the interrupt to use.  The default is 5.  To disable
          interrupts, set this to 0.

‘-device isa-ipmi-bt,bmc=ID[,ioport=VAL][,irq=VAL]’

     Like the KCS interface, but defines a BT interface.  The default
     port is 0xe4 and the default interrupt is 5.

‘-name NAME’
     Sets the NAME of the guest.  This name will be displayed in the SDL
     window caption.  The NAME will also be used for the VNC server.
     Also optionally set the top visible process name in Linux.  Naming
     of individual threads can also be enabled on Linux to aid
     debugging.
‘-uuid UUID’
     Set system UUID.

2.3.2 Block device options
--------------------------

‘-fda FILE’
‘-fdb FILE’
     Use FILE as floppy disk 0/1 image (*note disk_images::).
‘-hda FILE’
‘-hdb FILE’
‘-hdc FILE’
‘-hdd FILE’
     Use FILE as hard disk 0, 1, 2 or 3 image (*note disk_images::).
‘-cdrom FILE’
     Use FILE as CD-ROM image (you cannot use ‘-hdc’ and ‘-cdrom’ at the
     same time).  You can use the host CD-ROM by using ‘/dev/cdrom’ as
     filename (*note host_drives::).
‘-blockdev OPTION[,OPTION[,OPTION[,...]]]’

     Define a new block driver node.  Some of the options apply to all
     block drivers, other options are only accepted for a specific block
     driver.  See below for a list of generic options and options for
     the most common block drivers.

     Options that expect a reference to another node (e.g.  ‘file’) can
     be given in two ways.  Either you specify the node name of an
     already existing node (file=NODE-NAME), or you define a new node
     inline, adding options for the referenced node after a dot
     (file.filename=PATH,file.aio=native).

     A block driver node created with ‘-blockdev’ can be used for a
     guest device by specifying its node name for the ‘drive’ property
     in a ‘-device’ argument that defines a block device.

     ‘Valid options for any block driver node:’

          ‘driver’
               Specifies the block driver to use for the given node.
          ‘node-name’
               This defines the name of the block driver node by which
               it will be referenced later.  The name must be unique,
               i.e.  it must not match the name of a different block
               driver node, or (if you use ‘-drive’ as well) the ID of a
               drive.

               If no node name is specified, it is automatically
               generated.  The generated node name is not intended to be
               predictable and changes between QEMU invocations.  For
               the top level, an explicit node name must be specified.
          ‘read-only’
               Open the node read-only.  Guest write attempts will fail.

               Note that some block drivers support only read-only
               access, either generally or in certain configurations.
               In this case, the default value ‘read-only=off’ does not
               work and the option must be specified explicitly.
          ‘auto-read-only’
               If ‘auto-read-only=on’ is set, QEMU may fall back to
               read-only usage even when ‘read-only=off’ is requested,
               or even switch between modes as needed, e.g.  depending
               on whether the image file is writable or whether a
               writing user is attached to the node.
          ‘force-share’
               Override the image locking system of QEMU by forcing the
               node to utilize weaker shared access for permissions
               where it would normally request exclusive access.  When
               there is the potential for multiple instances to have the
               same file open (whether this invocation of QEMU is the
               first or the second instance), both instances must permit
               shared access for the second instance to succeed at
               opening the file.

               Enabling ‘force-share=on’ requires ‘read-only=on’.
          ‘cache.direct’
               The host page cache can be avoided with
               ‘cache.direct=on’.  This will attempt to do disk IO
               directly to the guest’s memory.  QEMU may still perform
               an internal copy of the data.
          ‘cache.no-flush’
               In case you don’t care about data integrity over host
               failures, you can use ‘cache.no-flush=on’.  This option
               tells QEMU that it never needs to write any data to the
               disk but can instead keep things in cache.  If anything
               goes wrong, like your host losing power, the disk storage
               getting disconnected accidentally, etc.  your image will
               most probably be rendered unusable.
          ‘discard=DISCARD’
               DISCARD is one of "ignore" (or "off") or "unmap" (or
               "on") and controls whether ‘discard’ (also known as
               ‘trim’ or ‘unmap’) requests are ignored or passed to the
               filesystem.  Some machine types may not support discard
               requests.
          ‘detect-zeroes=DETECT-ZEROES’
               DETECT-ZEROES is "off", "on" or "unmap" and enables the
               automatic conversion of plain zero writes by the OS to
               driver specific optimized zero write commands.  You may
               even choose "unmap" if DISCARD is set to "unmap" to allow
               a zero write to be converted to an ‘unmap’ operation.

     ‘Driver-specific options for file’

          This is the protocol-level block driver for accessing regular
          files.

          ‘filename’
               The path to the image file in the local filesystem
          ‘aio’
               Specifies the AIO backend (threads/native, default:
               threads)
          ‘locking’
               Specifies whether the image file is protected with Linux
               OFD / POSIX locks.  The default is to use the Linux Open
               File Descriptor API if available, otherwise no lock is
               applied.  (auto/on/off, default: auto)
          Example:
               -blockdev driver=file,node-name=disk,filename=disk.img

     ‘Driver-specific options for raw’

          This is the image format block driver for raw images.  It is
          usually stacked on top of a protocol level block driver such
          as ‘file’.

          ‘file’
               Reference to or definition of the data source block
               driver node (e.g.  a ‘file’ driver node)
          Example 1:
               -blockdev driver=file,node-name=disk_file,filename=disk.img
               -blockdev driver=raw,node-name=disk,file=disk_file
          Example 2:
               -blockdev driver=raw,node-name=disk,file.driver=file,file.filename=disk.img

     ‘Driver-specific options for qcow2’

          This is the image format block driver for qcow2 images.  It is
          usually stacked on top of a protocol level block driver such
          as ‘file’.

          ‘file’
               Reference to or definition of the data source block
               driver node (e.g.  a ‘file’ driver node)

          ‘backing’
               Reference to or definition of the backing file block
               device (default is taken from the image file).  It is
               allowed to pass ‘null’ here in order to disable the
               default backing file.

          ‘lazy-refcounts’
               Whether to enable the lazy refcounts feature (on/off;
               default is taken from the image file)

          ‘cache-size’
               The maximum total size of the L2 table and refcount block
               caches in bytes (default: the sum of l2-cache-size and
               refcount-cache-size)

          ‘l2-cache-size’
               The maximum size of the L2 table cache in bytes (default:
               if cache-size is not specified - 32M on Linux platforms,
               and 8M on non-Linux platforms; otherwise, as large as
               possible within the cache-size, while permitting the
               requested or the minimal refcount cache size)

          ‘refcount-cache-size’
               The maximum size of the refcount block cache in bytes
               (default: 4 times the cluster size; or if cache-size is
               specified, the part of it which is not used for the L2
               cache)

          ‘cache-clean-interval’
               Clean unused entries in the L2 and refcount caches.  The
               interval is in seconds.  The default value is 600 on
               supporting platforms, and 0 on other platforms.  Setting
               it to 0 disables this feature.

          ‘pass-discard-request’
               Whether discard requests to the qcow2 device should be
               forwarded to the data source (on/off; default: on if
               discard=unmap is specified, off otherwise)

          ‘pass-discard-snapshot’
               Whether discard requests for the data source should be
               issued when a snapshot operation (e.g.  deleting a
               snapshot) frees clusters in the qcow2 file (on/off;
               default: on)

          ‘pass-discard-other’
               Whether discard requests for the data source should be
               issued on other occasions where a cluster gets freed
               (on/off; default: off)

          ‘overlap-check’
               Which overlap checks to perform for writes to the image
               (none/constant/cached/all; default: cached).  For details
               or finer granularity control refer to the QAPI
               documentation of ‘blockdev-add’.

          Example 1:
               -blockdev driver=file,node-name=my_file,filename=/tmp/disk.qcow2
               -blockdev driver=qcow2,node-name=hda,file=my_file,overlap-check=none,cache-size=16777216
          Example 2:
               -blockdev driver=qcow2,node-name=disk,file.driver=http,file.filename=http://example.com/image.qcow2

     ‘Driver-specific options for other drivers’
          Please refer to the QAPI documentation of the ‘blockdev-add’
          QMP command.

‘-drive OPTION[,OPTION[,OPTION[,...]]]’

     Define a new drive.  This includes creating a block driver node
     (the backend) as well as a guest device, and is mostly a shortcut
     for defining the corresponding ‘-blockdev’ and ‘-device’ options.

     ‘-drive’ accepts all options that are accepted by ‘-blockdev’.  In
     addition, it knows the following options:

     ‘file=FILE’
          This option defines which disk image (*note disk_images::) to
          use with this drive.  If the filename contains comma, you must
          double it (for instance, "file=my,,file" to use file
          "my,file").

          Special files such as iSCSI devices can be specified using
          protocol specific URLs.  See the section for "Device URL
          Syntax" for more information.
     ‘if=INTERFACE’
          This option defines on which type on interface the drive is
          connected.  Available types are: ide, scsi, sd, mtd, floppy,
          pflash, virtio, none.
     ‘bus=BUS,unit=UNIT’
          These options define where is connected the drive by defining
          the bus number and the unit id.
     ‘index=INDEX’
          This option defines where is connected the drive by using an
          index in the list of available connectors of a given interface
          type.
     ‘media=MEDIA’
          This option defines the type of the media: disk or cdrom.
     ‘snapshot=SNAPSHOT’
          SNAPSHOT is "on" or "off" and controls snapshot mode for the
          given drive (see ‘-snapshot’).
     ‘cache=CACHE’
          CACHE is "none", "writeback", "unsafe", "directsync" or
          "writethrough" and controls how the host cache is used to
          access block data.  This is a shortcut that sets the
          ‘cache.direct’ and ‘cache.no-flush’ options (as in
          ‘-blockdev’), and additionally ‘cache.writeback’, which
          provides a default for the ‘write-cache’ option of block guest
          devices (as in ‘-device’).  The modes correspond to the
          following settings:

                            │ cache.writeback   cache.direct   cache.no-flush
               ─────────────┼─────────────────────────────────────────────────
               writeback    │ on                off            off
               none         │ on                on             off
               writethrough │ off               off            off
               directsync   │ off               on             off
               unsafe       │ on                off            on

          The default mode is ‘cache=writeback’.

     ‘aio=AIO’
          AIO is "threads", or "native" and selects between pthread
          based disk I/O and native Linux AIO.
     ‘format=FORMAT’
          Specify which disk FORMAT will be used rather than detecting
          the format.  Can be used to specify format=raw to avoid
          interpreting an untrusted format header.
     ‘werror=ACTION,rerror=ACTION’
          Specify which ACTION to take on write and read errors.  Valid
          actions are: "ignore" (ignore the error and try to continue),
          "stop" (pause QEMU), "report" (report the error to the guest),
          "enospc" (pause QEMU only if the host disk is full; report the
          error to the guest otherwise).  The default setting is
          ‘werror=enospc’ and ‘rerror=report’.
     ‘copy-on-read=COPY-ON-READ’
          COPY-ON-READ is "on" or "off" and enables whether to copy read
          backing file sectors into the image file.
     ‘bps=B,bps_rd=R,bps_wr=W’
          Specify bandwidth throttling limits in bytes per second,
          either for all request types or for reads or writes only.
          Small values can lead to timeouts or hangs inside the guest.
          A safe minimum for disks is 2 MB/s.
     ‘bps_max=BM,bps_rd_max=RM,bps_wr_max=WM’
          Specify bursts in bytes per second, either for all request
          types or for reads or writes only.  Bursts allow the guest I/O
          to spike above the limit temporarily.
     ‘iops=I,iops_rd=R,iops_wr=W’
          Specify request rate limits in requests per second, either for
          all request types or for reads or writes only.
     ‘iops_max=BM,iops_rd_max=RM,iops_wr_max=WM’
          Specify bursts in requests per second, either for all request
          types or for reads or writes only.  Bursts allow the guest I/O
          to spike above the limit temporarily.
     ‘iops_size=IS’
          Let every IS bytes of a request count as a new request for
          iops throttling purposes.  Use this option to prevent guests
          from circumventing iops limits by sending fewer but larger
          requests.
     ‘group=G’
          Join a throttling quota group with given name G.  All drives
          that are members of the same group are accounted for together.
          Use this option to prevent guests from circumventing
          throttling limits by using many small disks instead of a
          single larger disk.

     By default, the ‘cache.writeback=on’ mode is used.  It will report
     data writes as completed as soon as the data is present in the host
     page cache.  This is safe as long as your guest OS makes sure to
     correctly flush disk caches where needed.  If your guest OS does
     not handle volatile disk write caches correctly and your host
     crashes or loses power, then the guest may experience data
     corruption.

     For such guests, you should consider using ‘cache.writeback=off’.
     This means that the host page cache will be used to read and write
     data, but write notification will be sent to the guest only after
     QEMU has made sure to flush each write to the disk.  Be aware that
     this has a major impact on performance.

     When using the ‘-snapshot’ option, unsafe caching is always used.

     Copy-on-read avoids accessing the same backing file sectors
     repeatedly and is useful when the backing file is over a slow
     network.  By default copy-on-read is off.

     Instead of ‘-cdrom’ you can use:
          qemu-kvm -drive file=file,index=2,media=cdrom

     Instead of ‘-hda’, ‘-hdb’, ‘-hdc’, ‘-hdd’, you can use:
          qemu-kvm -drive file=file,index=0,media=disk
          qemu-kvm -drive file=file,index=1,media=disk
          qemu-kvm -drive file=file,index=2,media=disk
          qemu-kvm -drive file=file,index=3,media=disk

     You can open an image using pre-opened file descriptors from an fd
     set:
          qemu-kvm \
          -add-fd fd=3,set=2,opaque="rdwr:/path/to/file" \
          -add-fd fd=4,set=2,opaque="rdonly:/path/to/file" \
          -drive file=/dev/fdset/2,index=0,media=disk

     You can connect a CDROM to the slave of ide0:
          qemu-kvm -drive file=file,if=ide,index=1,media=cdrom

     If you don’t specify the "file=" argument, you define an empty
     drive:
          qemu-kvm -drive if=ide,index=1,media=cdrom

     Instead of ‘-fda’, ‘-fdb’, you can use:
          qemu-kvm -drive file=file,index=0,if=floppy
          qemu-kvm -drive file=file,index=1,if=floppy

     By default, INTERFACE is "ide" and INDEX is automatically
     incremented:
          qemu-kvm -drive file=a -drive file=b"
     is interpreted like:
          qemu-kvm -hda a -hdb b
‘-mtdblock FILE’
     Use FILE as on-board Flash memory image.
‘-sd FILE’
     Use FILE as SecureDigital card image.
‘-pflash FILE’
     Use FILE as a parallel flash image.
‘-snapshot’
     Write to temporary files instead of disk image files.  In this
     case, the raw disk image you use is not written back.  You can
     however force the write back by pressing <C-a s> (*note
     disk_images::).

‘-fsdev local,id=ID,path=PATH,security_model=SECURITY_MODEL [,writeout=WRITEOUT][,readonly][,fmode=FMODE][,dmode=DMODE] [,throttling.OPTION=VALUE[,throttling.OPTION=VALUE[,...]]]’
‘-fsdev proxy,id=ID,socket=SOCKET[,writeout=WRITEOUT][,readonly]’
‘-fsdev proxy,id=ID,sock_fd=SOCK_FD[,writeout=WRITEOUT][,readonly]’
‘-fsdev synth,id=ID[,readonly]’
     Define a new file system device.  Valid options are:
     ‘local’
          Accesses to the filesystem are done by QEMU.
     ‘proxy’
          Accesses to the filesystem are done by virtfs-proxy-helper(1).
     ‘synth’
          Synthetic filesystem, only used by QTests.
     ‘id=ID’
          Specifies identifier for this device.
     ‘path=PATH’
          Specifies the export path for the file system device.  Files
          under this path will be available to the 9p client on the
          guest.
     ‘security_model=SECURITY_MODEL’
          Specifies the security model to be used for this export path.
          Supported security models are "passthrough", "mapped-xattr",
          "mapped-file" and "none".  In "passthrough" security model,
          files are stored using the same credentials as they are
          created on the guest.  This requires QEMU to run as root.  In
          "mapped-xattr" security model, some of the file attributes
          like uid, gid, mode bits and link target are stored as file
          attributes.  For "mapped-file" these attributes are stored in
          the hidden .virtfs_metadata directory.  Directories exported
          by this security model cannot interact with other unix tools.
          "none" security model is same as passthrough except the sever
          won’t report failures if it fails to set file attributes like
          ownership.  Security model is mandatory only for local
          fsdriver.  Other fsdrivers (like proxy) don’t take security
          model as a parameter.
     ‘writeout=WRITEOUT’
          This is an optional argument.  The only supported value is
          "immediate".  This means that host page cache will be used to
          read and write data but write notification will be sent to the
          guest only when the data has been reported as written by the
          storage subsystem.
     ‘readonly’
          Enables exporting 9p share as a readonly mount for guests.  By
          default read-write access is given.
     ‘socket=SOCKET’
          Enables proxy filesystem driver to use passed socket file for
          communicating with virtfs-proxy-helper(1).
     ‘sock_fd=SOCK_FD’
          Enables proxy filesystem driver to use passed socket
          descriptor for communicating with virtfs-proxy-helper(1).
          Usually a helper like libvirt will create socketpair and pass
          one of the fds as sock_fd.
     ‘fmode=FMODE’
          Specifies the default mode for newly created files on the
          host.  Works only with security models "mapped-xattr" and
          "mapped-file".
     ‘dmode=DMODE’
          Specifies the default mode for newly created directories on
          the host.  Works only with security models "mapped-xattr" and
          "mapped-file".
     ‘throttling.bps-total=B,throttling.bps-read=R,throttling.bps-write=W’
          Specify bandwidth throttling limits in bytes per second,
          either for all request types or for reads or writes only.
     ‘throttling.bps-total-max=BM,bps-read-max=RM,bps-write-max=WM’
          Specify bursts in bytes per second, either for all request
          types or for reads or writes only.  Bursts allow the guest I/O
          to spike above the limit temporarily.
     ‘throttling.iops-total=I,throttling.iops-read=R, throttling.iops-write=W’
          Specify request rate limits in requests per second, either for
          all request types or for reads or writes only.
     ‘throttling.iops-total-max=IM,throttling.iops-read-max=IRM, throttling.iops-write-max=IWM’
          Specify bursts in requests per second, either for all request
          types or for reads or writes only.  Bursts allow the guest I/O
          to spike above the limit temporarily.
     ‘throttling.iops-size=IS’
          Let every IS bytes of a request count as a new request for
          iops throttling purposes.

     -fsdev option is used along with -device driver "virtio-9p-...".
‘-device virtio-9p-TYPE,fsdev=ID,mount_tag=MOUNT_TAG’
     Options for virtio-9p-...  driver are:
     ‘TYPE’
          Specifies the variant to be used.  Supported values are "pci",
          "ccw" or "device", depending on the machine type.
     ‘fsdev=ID’
          Specifies the id value specified along with -fsdev option.
     ‘mount_tag=MOUNT_TAG’
          Specifies the tag name to be used by the guest to mount this
          export point.

‘-virtfs local,path=PATH,mount_tag=MOUNT_TAG ,security_model=SECURITY_MODEL[,writeout=WRITEOUT][,readonly] [,fmode=FMODE][,dmode=DMODE][,multidevs=MULTIDEVS]’
‘-virtfs proxy,socket=SOCKET,mount_tag=MOUNT_TAG [,writeout=WRITEOUT][,readonly]’
‘-virtfs proxy,sock_fd=SOCK_FD,mount_tag=MOUNT_TAG [,writeout=WRITEOUT][,readonly]’
‘-virtfs synth,mount_tag=MOUNT_TAG’

     Define a new filesystem device and expose it to the guest using a
     virtio-9p-device.  The general form of a Virtual File system
     pass-through options are:
     ‘local’
          Accesses to the filesystem are done by QEMU.
     ‘proxy’
          Accesses to the filesystem are done by virtfs-proxy-helper(1).
     ‘synth’
          Synthetic filesystem, only used by QTests.
     ‘id=ID’
          Specifies identifier for the filesystem device
     ‘path=PATH’
          Specifies the export path for the file system device.  Files
          under this path will be available to the 9p client on the
          guest.
     ‘security_model=SECURITY_MODEL’
          Specifies the security model to be used for this export path.
          Supported security models are "passthrough", "mapped-xattr",
          "mapped-file" and "none".  In "passthrough" security model,
          files are stored using the same credentials as they are
          created on the guest.  This requires QEMU to run as root.  In
          "mapped-xattr" security model, some of the file attributes
          like uid, gid, mode bits and link target are stored as file
          attributes.  For "mapped-file" these attributes are stored in
          the hidden .virtfs_metadata directory.  Directories exported
          by this security model cannot interact with other unix tools.
          "none" security model is same as passthrough except the sever
          won’t report failures if it fails to set file attributes like
          ownership.  Security model is mandatory only for local
          fsdriver.  Other fsdrivers (like proxy) don’t take security
          model as a parameter.
     ‘writeout=WRITEOUT’
          This is an optional argument.  The only supported value is
          "immediate".  This means that host page cache will be used to
          read and write data but write notification will be sent to the
          guest only when the data has been reported as written by the
          storage subsystem.
     ‘readonly’
          Enables exporting 9p share as a readonly mount for guests.  By
          default read-write access is given.
     ‘socket=SOCKET’
          Enables proxy filesystem driver to use passed socket file for
          communicating with virtfs-proxy-helper(1).  Usually a helper
          like libvirt will create socketpair and pass one of the fds as
          sock_fd.
     ‘sock_fd’
          Enables proxy filesystem driver to use passed ’sock_fd’ as the
          socket descriptor for interfacing with virtfs-proxy-helper(1).
     ‘fmode=FMODE’
          Specifies the default mode for newly created files on the
          host.  Works only with security models "mapped-xattr" and
          "mapped-file".
     ‘dmode=DMODE’
          Specifies the default mode for newly created directories on
          the host.  Works only with security models "mapped-xattr" and
          "mapped-file".
     ‘mount_tag=MOUNT_TAG’
          Specifies the tag name to be used by the guest to mount this
          export point.
     ‘multidevs=MULTIDEVS’
          Specifies how to deal with multiple devices being shared with
          a 9p export.  Supported behaviours are either "remap",
          "forbid" or "warn".  The latter is the default behaviour on
          which virtfs 9p expects only one device to be shared with the
          same export, and if more than one device is shared and
          accessed via the same 9p export then only a warning message is
          logged (once) by qemu on host side.  In order to avoid file ID
          collisions on guest you should either create a separate virtfs
          export for each device to be shared with guests (recommended
          way) or you might use "remap" instead which allows you to
          share multiple devices with only one export instead, which is
          achieved by remapping the original inode numbers from host to
          guest in a way that would prevent such collisions.  Remapping
          inodes in such use cases is required because the original
          device IDs from host are never passed and exposed on guest.
          Instead all files of an export shared with virtfs always share
          the same device id on guest.  So two files with identical
          inode numbers but from actually different devices on host
          would otherwise cause a file ID collision and hence potential
          misbehaviours on guest.  "forbid" on the other hand assumes
          like "warn" that only one device is shared by the same export,
          however it will not only log a warning message but also deny
          access to additional devices on guest.  Note though that
          "forbid" does currently not block all possible file access
          operations (e.g.  readdir() would still return entries from
          other devices).
‘-virtfs_synth’
     Create synthetic file system image.  Note that this option is now
     deprecated.  Please use ‘-fsdev synth’ and ‘-device virtio-9p-...’
     instead.
‘-iscsi’
     Configure iSCSI session parameters.

2.3.3 USB options
-----------------

‘-usb’
     Enable USB emulation on machine types with an on-board USB host
     controller (if not enabled by default).  Note that on-board USB
     host controllers may not support USB 3.0.  In this case ‘-device
     qemu-xhci’ can be used instead on machines with PCI.

‘-usbdevice DEVNAME’
     Add the USB device DEVNAME.  Note that this option is deprecated,
     please use ‘-device usb-...’ instead.  *Note usb_devices::.

     ‘mouse’
          Virtual Mouse.  This will override the PS/2 mouse emulation
          when activated.

     ‘tablet’
          Pointer device that uses absolute coordinates (like a
          touchscreen).  This means QEMU is able to report the mouse
          position without having to grab the mouse.  Also overrides the
          PS/2 mouse emulation when activated.

     ‘braille’
          Braille device.  This will use BrlAPI to display the braille
          output on a real or fake device.

2.3.4 Display options
---------------------

‘-display TYPE’
     Select type of display to use.  This option is a replacement for
     the old style -sdl/-curses/...  options.  Valid values for TYPE are
     ‘sdl’
          Display video output via SDL (usually in a separate graphics
          window; see the SDL documentation for other possibilities).
     ‘curses’
          Display video output via curses.  For graphics device models
          which support a text mode, QEMU can display this output using
          a curses/ncurses interface.  Nothing is displayed when the
          graphics device is in graphical mode or if the graphics device
          does not support a text mode.  Generally only the VGA device
          models support text mode.  The font charset used by the guest
          can be specified with the ‘charset’ option, for example
          ‘charset=CP850’ for IBM CP850 encoding.  The default is
          ‘CP437’.
     ‘none’
          Do not display video output.  The guest will still see an
          emulated graphics card, but its output will not be displayed
          to the QEMU user.  This option differs from the -nographic
          option in that it only affects what is done with video output;
          -nographic also changes the destination of the serial and
          parallel port data.
     ‘gtk’
          Display video output in a GTK window.  This interface provides
          drop-down menus and other UI elements to configure and control
          the VM during runtime.
     ‘vnc’
          Start a VNC server on display <arg>
     ‘egl-headless’
          Offload all OpenGL operations to a local DRI device.  For any
          graphical display, this display needs to be paired with either
          VNC or SPICE displays.
     ‘spice-app’
          Start QEMU as a Spice server and launch the default Spice
          client application.  The Spice server will redirect the serial
          consoles and QEMU monitors.  (Since 4.0)
‘-nographic’
     Normally, if QEMU is compiled with graphical window support, it
     displays output such as guest graphics, guest console, and the QEMU
     monitor in a window.  With this option, you can totally disable
     graphical output so that QEMU is a simple command line application.
     The emulated serial port is redirected on the console and muxed
     with the monitor (unless redirected elsewhere explicitly).
     Therefore, you can still use QEMU to debug a Linux kernel with a
     serial console.  Use <C-a h> for help on switching between the
     console and monitor.
‘-curses’
     Normally, if QEMU is compiled with graphical window support, it
     displays output such as guest graphics, guest console, and the QEMU
     monitor in a window.  With this option, QEMU can display the VGA
     output when in text mode using a curses/ncurses interface.  Nothing
     is displayed in graphical mode.
‘-alt-grab’
     Use Ctrl-Alt-Shift to grab mouse (instead of Ctrl-Alt).  Note that
     this also affects the special keys (for fullscreen, monitor-mode
     switching, etc).
‘-ctrl-grab’
     Use Right-Ctrl to grab mouse (instead of Ctrl-Alt).  Note that this
     also affects the special keys (for fullscreen, monitor-mode
     switching, etc).
‘-no-quit’
     Disable SDL window close capability.
‘-sdl’
     Enable SDL.
‘-spice OPTION[,OPTION[,...]]’
     Enable the spice remote desktop protocol.  Valid options are

     ‘port=<nr>’
          Set the TCP port spice is listening on for plaintext channels.

     ‘addr=<addr>’
          Set the IP address spice is listening on.  Default is any
          address.

     ‘ipv4’
     ‘ipv6’
     ‘unix’
          Force using the specified IP version.

     ‘password=<secret>’
          Set the password you need to authenticate.

     ‘sasl’
          Require that the client use SASL to authenticate with the
          spice.  The exact choice of authentication method used is
          controlled from the system / user’s SASL configuration file
          for the ’qemu’ service.  This is typically found in
          /etc/sasl2/qemu.conf.  If running QEMU as an unprivileged
          user, an environment variable SASL_CONF_PATH can be used to
          make it search alternate locations for the service config.
          While some SASL auth methods can also provide data encryption
          (eg GSSAPI), it is recommended that SASL always be combined
          with the ’tls’ and ’x509’ settings to enable use of SSL and
          server certificates.  This ensures a data encryption
          preventing compromise of authentication credentials.

     ‘disable-ticketing’
          Allow client connects without authentication.

     ‘disable-copy-paste’
          Disable copy paste between the client and the guest.

     ‘disable-agent-file-xfer’
          Disable spice-vdagent based file-xfer between the client and
          the guest.

     ‘tls-port=<nr>’
          Set the TCP port spice is listening on for encrypted channels.

     ‘x509-dir=<dir>’
          Set the x509 file directory.  Expects same filenames as -vnc
          $display,x509=$dir

     ‘x509-key-file=<file>’
     ‘x509-key-password=<file>’
     ‘x509-cert-file=<file>’
     ‘x509-cacert-file=<file>’
     ‘x509-dh-key-file=<file>’
          The x509 file names can also be configured individually.

     ‘tls-ciphers=<list>’
          Specify which ciphers to use.

     ‘tls-channel=[main|display|cursor|inputs|record|playback]’
     ‘plaintext-channel=[main|display|cursor|inputs|record|playback]’
          Force specific channel to be used with or without TLS
          encryption.  The options can be specified multiple times to
          configure multiple channels.  The special name "default" can
          be used to set the default mode.  For channels which are not
          explicitly forced into one mode the spice client is allowed to
          pick tls/plaintext as he pleases.

     ‘image-compression=[auto_glz|auto_lz|quic|glz|lz|off]’
          Configure image compression (lossless).  Default is auto_glz.

     ‘jpeg-wan-compression=[auto|never|always]’
     ‘zlib-glz-wan-compression=[auto|never|always]’
          Configure wan image compression (lossy for slow links).
          Default is auto.

     ‘streaming-video=[off|all|filter]’
          Configure video stream detection.  Default is off.

     ‘agent-mouse=[on|off]’
          Enable/disable passing mouse events via vdagent.  Default is
          on.

     ‘playback-compression=[on|off]’
          Enable/disable audio stream compression (using celt 0.5.1).
          Default is on.

     ‘seamless-migration=[on|off]’
          Enable/disable spice seamless migration.  Default is off.

     ‘gl=[on|off]’
          Enable/disable OpenGL context.  Default is off.

     ‘rendernode=<file>’
          DRM render node for OpenGL rendering.  If not specified, it
          will pick the first available.  (Since 2.9)

‘-portrait’
     Rotate graphical output 90 deg left (only PXA LCD).
‘-rotate DEG’
     Rotate graphical output some deg left (only PXA LCD).
‘-vga TYPE’
     Select type of VGA card to emulate.  Valid values for TYPE are
     ‘cirrus’
          Cirrus Logic GD5446 Video card.  All Windows versions starting
          from Windows 95 should recognize and use this graphic card.
          For optimal performances, use 16 bit color depth in the guest
          and the host OS. (This card was the default before QEMU 2.2)
     ‘std’
          Standard VGA card with Bochs VBE extensions.  If your guest OS
          supports the VESA 2.0 VBE extensions (e.g.  Windows XP) and if
          you want to use high resolution modes (>= 1280x1024x16) then
          you should use this option.  (This card is the default since
          QEMU 2.2)
     ‘vmware’
          VMWare SVGA-II compatible adapter.  Use it if you have
          sufficiently recent XFree86/XOrg server or Windows guest with
          a driver for this card.
     ‘qxl’
          QXL paravirtual graphic card.  It is VGA compatible (including
          VESA 2.0 VBE support).  Works best with qxl guest drivers
          installed though.  Recommended choice when using the spice
          protocol.
     ‘tcx’
          (sun4m only) Sun TCX framebuffer.  This is the default
          framebuffer for sun4m machines and offers both 8-bit and
          24-bit colour depths at a fixed resolution of 1024x768.
     ‘cg3’
          (sun4m only) Sun cgthree framebuffer.  This is a simple 8-bit
          framebuffer for sun4m machines available in both 1024x768
          (OpenBIOS) and 1152x900 (OBP) resolutions aimed at people
          wishing to run older Solaris versions.
     ‘virtio’
          Virtio VGA card.
     ‘none’
          Disable VGA card.
‘-full-screen’
     Start in full screen.
‘-g WIDTHxHEIGHT[xDEPTH]’
     Set the initial graphical resolution and depth (PPC, SPARC only).
‘-vnc DISPLAY[,OPTION[,OPTION[,...]]]’
     Normally, if QEMU is compiled with graphical window support, it
     displays output such as guest graphics, guest console, and the QEMU
     monitor in a window.  With this option, you can have QEMU listen on
     VNC display DISPLAY and redirect the VGA display over the VNC
     session.  It is very useful to enable the usb tablet device when
     using this option (option ‘-device usb-tablet’).  When using the
     VNC display, you must use the ‘-k’ parameter to set the keyboard
     layout if you are not using en-us.  Valid syntax for the DISPLAY is

     ‘to=L’

          With this option, QEMU will try next available VNC DISPLAYs,
          until the number L, if the origianlly defined "-vnc DISPLAY"
          is not available, e.g.  port 5900+DISPLAY is already used by
          another application.  By default, to=0.

     ‘HOST:D’

          TCP connections will only be allowed from HOST on display D.
          By convention the TCP port is 5900+D.  Optionally, HOST can be
          omitted in which case the server will accept connections from
          any host.

     ‘unix:PATH’

          Connections will be allowed over UNIX domain sockets where
          PATH is the location of a unix socket to listen for
          connections on.

     ‘none’

          VNC is initialized but not started.  The monitor ‘change’
          command can be used to later start the VNC server.

     Following the DISPLAY value there may be one or more OPTION flags
     separated by commas.  Valid options are

     ‘reverse’

          Connect to a listening VNC client via a “reverse” connection.
          The client is specified by the DISPLAY.  For reverse network
          connections (HOST:D,‘reverse’), the D argument is a TCP port
          number, not a display number.

     ‘websocket’

          Opens an additional TCP listening port dedicated to VNC
          Websocket connections.  If a bare WEBSOCKET option is given,
          the Websocket port is 5700+DISPLAY.  An alternative port can
          be specified with the syntax ‘websocket’=PORT.

          If HOST is specified connections will only be allowed from
          this host.  It is possible to control the websocket listen
          address independently, using the syntax ‘websocket’=HOST:PORT.

          If no TLS credentials are provided, the websocket connection
          runs in unencrypted mode.  If TLS credentials are provided,
          the websocket connection requires encrypted client
          connections.

     ‘password’

          Require that password based authentication is used for client
          connections.

          The password must be set separately using the ‘set_password’
          command in the *note pcsys_monitor::.  The syntax to change
          your password is: ‘set_password <protocol> <password>’ where
          <protocol> could be either "vnc" or "spice".

          If you would like to change <protocol> password expiration,
          you should use ‘expire_password <protocol> <expiration-time>’
          where expiration time could be one of the following options:
          now, never, +seconds or UNIX time of expiration, e.g.  +60 to
          make password expire in 60 seconds, or 1335196800 to make
          password expire on "Mon Apr 23 12:00:00 EDT 2012" (UNIX time
          for this date and time).

          You can also use keywords "now" or "never" for the expiration
          time to allow <protocol> password to expire immediately or
          never expire.

     ‘tls-creds=ID’

          Provides the ID of a set of TLS credentials to use to secure
          the VNC server.  They will apply to both the normal VNC server
          socket and the websocket socket (if enabled).  Setting TLS
          credentials will cause the VNC server socket to enable the
          VeNCrypt auth mechanism.  The credentials should have been
          previously created using the ‘-object tls-creds’ argument.

     ‘tls-authz=ID’

          Provides the ID of the QAuthZ authorization object against
          which the client’s x509 distinguished name will validated.
          This object is only resolved at time of use, so can be deleted
          and recreated on the fly while the VNC server is active.  If
          missing, it will default to denying access.

     ‘sasl’

          Require that the client use SASL to authenticate with the VNC
          server.  The exact choice of authentication method used is
          controlled from the system / user’s SASL configuration file
          for the ’qemu’ service.  This is typically found in
          /etc/sasl2/qemu.conf.  If running QEMU as an unprivileged
          user, an environment variable SASL_CONF_PATH can be used to
          make it search alternate locations for the service config.
          While some SASL auth methods can also provide data encryption
          (eg GSSAPI), it is recommended that SASL always be combined
          with the ’tls’ and ’x509’ settings to enable use of SSL and
          server certificates.  This ensures a data encryption
          preventing compromise of authentication credentials.  See the
          *note vnc_security:: section for details on using SASL
          authentication.

     ‘sasl-authz=ID’

          Provides the ID of the QAuthZ authorization object against
          which the client’s SASL username will validated.  This object
          is only resolved at time of use, so can be deleted and
          recreated on the fly while the VNC server is active.  If
          missing, it will default to denying access.

     ‘acl’

          Legacy method for enabling authorization of clients against
          the x509 distinguished name and SASL username.  It results in
          the creation of two ‘authz-list’ objects with IDs of
          ‘vnc.username’ and ‘vnc.x509dname’.  The rules for these
          objects must be configured with the HMP ACL commands.

          This option is deprecated and should no longer be used.  The
          new ‘sasl-authz’ and ‘tls-authz’ options are a replacement.

     ‘lossy’

          Enable lossy compression methods (gradient, JPEG, ...).  If
          this option is set, VNC client may receive lossy framebuffer
          updates depending on its encoding settings.  Enabling this
          option can save a lot of bandwidth at the expense of quality.

     ‘non-adaptive’

          Disable adaptive encodings.  Adaptive encodings are enabled by
          default.  An adaptive encoding will try to detect frequently
          updated screen regions, and send updates in these regions
          using a lossy encoding (like JPEG). This can be really helpful
          to save bandwidth when playing videos.  Disabling adaptive
          encodings restores the original static behavior of encodings
          like Tight.

     ‘share=[allow-exclusive|force-shared|ignore]’

          Set display sharing policy.  ’allow-exclusive’ allows clients
          to ask for exclusive access.  As suggested by the rfb spec
          this is implemented by dropping other connections.  Connecting
          multiple clients in parallel requires all clients asking for a
          shared session (vncviewer: -shared switch).  This is the
          default.  ’force-shared’ disables exclusive client access.
          Useful for shared desktop sessions, where you don’t want
          someone forgetting specify -shared disconnect everybody else.
          ’ignore’ completely ignores the shared flag and allows
          everybody connect unconditionally.  Doesn’t conform to the rfb
          spec but is traditional QEMU behavior.

     ‘key-delay-ms’

          Set keyboard delay, for key down and key up events, in
          milliseconds.  Default is 10.  Keyboards are low-bandwidth
          devices, so this slowdown can help the device and guest to
          keep up and not lose events in case events are arriving in
          bulk.  Possible causes for the latter are flaky network
          connections, or scripts for automated testing.

     ‘audiodev=AUDIODEV’

          Use the specified AUDIODEV when the VNC client requests audio
          transmission.  When not using an -audiodev argument, this
          option must be omitted, otherwise is must be present and
          specify a valid audiodev.

2.3.5 i386 target only
----------------------

‘-win2k-hack’
     Use it when installing Windows 2000 to avoid a disk full bug.
     After Windows 2000 is installed, you no longer need this option
     (this option slows down the IDE transfers).
‘-no-fd-bootchk’
     Disable boot signature checking for floppy disks in BIOS. May be
     needed to boot from old floppy disks.
‘-no-acpi’
     Disable ACPI (Advanced Configuration and Power Interface) support.
     Use it if your guest OS complains about ACPI problems (PC target
     machine only).
‘-acpitable [sig=STR][,rev=N][,oem_id=STR][,oem_table_id=STR][,oem_rev=N] [,asl_compiler_id=STR][,asl_compiler_rev=N][,data=FILE1[:FILE2]...]’
     Add ACPI table with specified header fields and context from
     specified files.  For file=, take whole ACPI table from the
     specified files, including all ACPI headers (possible overridden by
     other options).  For data=, only data portion of the table is used,
     all header information is specified in the command line.  If a SLIC
     table is supplied to QEMU, then the SLIC’s oem_id and oem_table_id
     fields will override the same in the RSDT and the FADT (a.k.a.
     FACP), in order to ensure the field matches required by the
     Microsoft SLIC spec and the ACPI spec.
‘-smbios file=BINARY’
     Load SMBIOS entry from binary file.

‘-smbios type=0[,vendor=STR][,version=STR][,date=STR][,release=%D.%D][,uefi=on|off]’
     Specify SMBIOS type 0 fields

‘-smbios type=1[,manufacturer=STR][,product=STR][,version=STR][,serial=STR][,uuid=UUID][,sku=STR][,family=STR]’
     Specify SMBIOS type 1 fields

‘-smbios type=2[,manufacturer=STR][,product=STR][,version=STR][,serial=STR][,asset=STR][,location=STR]’
     Specify SMBIOS type 2 fields

‘-smbios type=3[,manufacturer=STR][,version=STR][,serial=STR][,asset=STR][,sku=STR]’
     Specify SMBIOS type 3 fields

‘-smbios type=4[,sock_pfx=STR][,manufacturer=STR][,version=STR][,serial=STR][,asset=STR][,part=STR]’
     Specify SMBIOS type 4 fields

‘-smbios type=17[,loc_pfx=STR][,bank=STR][,manufacturer=STR][,serial=STR][,asset=STR][,part=STR][,speed=%D]’
     Specify SMBIOS type 17 fields

2.3.6 Network options
---------------------

‘-nic [tap|bridge|user|l2tpv3|vde|netmap|vhost-user|socket][,...][,mac=macaddr][,model=mn]’
     This option is a shortcut for configuring both the on-board
     (default) guest NIC hardware and the host network backend in one
     go.  The host backend options are the same as with the
     corresponding ‘-netdev’ options below.  The guest NIC model can be
     set with ‘model=MODELNAME’.  Use ‘model=help’ to list the available
     device types.  The hardware MAC address can be set with
     ‘mac=MACADDR’.

     The following two example do exactly the same, to show how ‘-nic’
     can be used to shorten the command line length (note that the e1000
     is the default on i386, so the ‘model=e1000’ parameter could even
     be omitted here, too):
          qemu-kvm -netdev user,id=n1,ipv6=off -device e1000,netdev=n1,mac=52:54:98:76:54:32
          qemu-kvm -nic user,ipv6=off,model=e1000,mac=52:54:98:76:54:32

‘-nic none’
     Indicate that no network devices should be configured.  It is used
     to override the default configuration (default NIC with “user” host
     network backend) which is activated if no other networking options
     are provided.

‘-netdev user,id=ID[,OPTION][,OPTION][,...]’
     Configure user mode host network backend which requires no
     administrator privilege to run.  Valid options are:

     ‘id=ID’
          Assign symbolic name for use in monitor commands.

     ‘ipv4=on|off and ipv6=on|off’
          Specify that either IPv4 or IPv6 must be enabled.  If neither
          is specified both protocols are enabled.

     ‘net=ADDR[/MASK]’
          Set IP network address the guest will see.  Optionally specify
          the netmask, either in the form a.b.c.d or as number of valid
          top-most bits.  Default is 10.0.2.0/24.

     ‘host=ADDR’
          Specify the guest-visible address of the host.  Default is the
          2nd IP in the guest network, i.e.  x.x.x.2.

     ‘ipv6-net=ADDR[/INT]’
          Set IPv6 network address the guest will see (default is
          fec0::/64).  The network prefix is given in the usual
          hexadecimal IPv6 address notation.  The prefix size is
          optional, and is given as the number of valid top-most bits
          (default is 64).

     ‘ipv6-host=ADDR’
          Specify the guest-visible IPv6 address of the host.  Default
          is the 2nd IPv6 in the guest network, i.e.  xxxx::2.

     ‘restrict=on|off’
          If this option is enabled, the guest will be isolated, i.e.
          it will not be able to contact the host and no guest IP
          packets will be routed over the host to the outside.  This
          option does not affect any explicitly set forwarding rules.

     ‘hostname=NAME’
          Specifies the client hostname reported by the built-in DHCP
          server.

     ‘dhcpstart=ADDR’
          Specify the first of the 16 IPs the built-in DHCP server can
          assign.  Default is the 15th to 31st IP in the guest network,
          i.e.  x.x.x.15 to x.x.x.31.

     ‘dns=ADDR’
          Specify the guest-visible address of the virtual nameserver.
          The address must be different from the host address.  Default
          is the 3rd IP in the guest network, i.e.  x.x.x.3.

     ‘ipv6-dns=ADDR’
          Specify the guest-visible address of the IPv6 virtual
          nameserver.  The address must be different from the host
          address.  Default is the 3rd IP in the guest network, i.e.
          xxxx::3.

     ‘dnssearch=DOMAIN’
          Provides an entry for the domain-search list sent by the
          built-in DHCP server.  More than one domain suffix can be
          transmitted by specifying this option multiple times.  If
          supported, this will cause the guest to automatically try to
          append the given domain suffix(es) in case a domain name can
          not be resolved.

          Example:
               qemu-kvm -nic user,dnssearch=mgmt.example.org,dnssearch=example.org

     ‘domainname=DOMAIN’
          Specifies the client domain name reported by the built-in DHCP
          server.

     ‘tftp=DIR’
          When using the user mode network stack, activate a built-in
          TFTP server.  The files in DIR will be exposed as the root of
          a TFTP server.  The TFTP client on the guest must be
          configured in binary mode (use the command ‘bin’ of the Unix
          TFTP client).

     ‘tftp-server-name=NAME’
          In BOOTP reply, broadcast NAME as the "TFTP server name"
          (RFC2132 option 66).  This can be used to advise the guest to
          load boot files or configurations from a different server than
          the host address.

     ‘bootfile=FILE’
          When using the user mode network stack, broadcast FILE as the
          BOOTP filename.  In conjunction with ‘tftp’, this can be used
          to network boot a guest from a local directory.

          Example (using pxelinux):
               qemu-kvm -hda linux.img -boot n -device e1000,netdev=n1 \
               -netdev user,id=n1,tftp=/path/to/tftp/files,bootfile=/pxelinux.0

     ‘smb=DIR[,smbserver=ADDR]’
          When using the user mode network stack, activate a built-in
          SMB server so that Windows OSes can access to the host files
          in ‘DIR’ transparently.  The IP address of the SMB server can
          be set to ADDR.  By default the 4th IP in the guest network is
          used, i.e.  x.x.x.4.

          In the guest Windows OS, the line:
               10.0.2.4 smbserver
          must be added in the file ‘C:\WINDOWS\LMHOSTS’ (for windows
          9x/Me) or ‘C:\WINNT\SYSTEM32\DRIVERS\ETC\LMHOSTS’ (Windows
          NT/2000).

          Then ‘DIR’ can be accessed in ‘\\smbserver\qemu’.

          Note that a SAMBA server must be installed on the host OS.

     ‘hostfwd=[tcp|udp]:[HOSTADDR]:HOSTPORT-[GUESTADDR]:GUESTPORT’
          Redirect incoming TCP or UDP connections to the host port
          HOSTPORT to the guest IP address GUESTADDR on guest port
          GUESTPORT.  If GUESTADDR is not specified, its value is
          x.x.x.15 (default first address given by the built-in DHCP
          server).  By specifying HOSTADDR, the rule can be bound to a
          specific host interface.  If no connection type is set, TCP is
          used.  This option can be given multiple times.

          For example, to redirect host X11 connection from screen 1 to
          guest screen 0, use the following:

               # on the host
               qemu-kvm -nic user,hostfwd=tcp:127.0.0.1:6001-:6000
               # this host xterm should open in the guest X11 server
               xterm -display :1

          To redirect telnet connections from host port 5555 to telnet
          port on the guest, use the following:

               # on the host
               qemu-kvm -nic user,hostfwd=tcp::5555-:23
               telnet localhost 5555

          Then when you use on the host ‘telnet localhost 5555’, you
          connect to the guest telnet server.

     ‘guestfwd=[tcp]:SERVER:PORT-DEV’
     ‘guestfwd=[tcp]:SERVER:PORT-CMD:COMMAND’
          Forward guest TCP connections to the IP address SERVER on port
          PORT to the character device DEV or to a program executed by
          CMD:COMMAND which gets spawned for each connection.  This
          option can be given multiple times.

          You can either use a chardev directly and have that one used
          throughout QEMU’s lifetime, like in the following example:

               # open 10.10.1.1:4321 on bootup, connect 10.0.2.100:1234 to it whenever
               # the guest accesses it
               qemu-kvm -nic user,guestfwd=tcp:10.0.2.100:1234-tcp:10.10.1.1:4321

          Or you can execute a command on every TCP connection
          established by the guest, so that QEMU behaves similar to an
          inetd process for that virtual server:

               # call "netcat 10.10.1.1 4321" on every TCP connection to 10.0.2.100:1234
               # and connect the TCP stream to its stdin/stdout
               qemu-kvm -nic  'user,id=n1,guestfwd=tcp:10.0.2.100:1234-cmd:netcat 10.10.1.1 4321'

‘-netdev tap,id=ID[,fd=H][,ifname=NAME][,script=FILE][,downscript=DFILE][,br=BRIDGE][,helper=HELPER]’
     Configure a host TAP network backend with ID ID.

     Use the network script FILE to configure it and the network script
     DFILE to deconfigure it.  If NAME is not provided, the OS
     automatically provides one.  The default network configure script
     is ‘/etc/qemu-ifup’ and the default network deconfigure script is
     ‘/etc/qemu-ifdown’.  Use ‘script=no’ or ‘downscript=no’ to disable
     script execution.

     If running QEMU as an unprivileged user, use the network helper
     HELPER to configure the TAP interface and attach it to the bridge.
     The default network helper executable is
     ‘/path/to/qemu-bridge-helper’ and the default bridge device is
     ‘br0’.

     ‘fd’=H can be used to specify the handle of an already opened host
     TAP interface.

     Examples:

          #launch a QEMU instance with the default network script
          qemu-kvm linux.img -nic tap

          #launch a QEMU instance with two NICs, each one connected
          #to a TAP device
          qemu-kvm linux.img \
          -netdev tap,id=nd0,ifname=tap0 -device e1000,netdev=nd0 \
          -netdev tap,id=nd1,ifname=tap1 -device rtl8139,netdev=nd1

          #launch a QEMU instance with the default network helper to
          #connect a TAP device to bridge br0
          qemu-kvm linux.img -device virtio-net-pci,netdev=n1 \
          -netdev tap,id=n1,"helper=/path/to/qemu-bridge-helper"

‘-netdev bridge,id=ID[,br=BRIDGE][,helper=HELPER]’
     Connect a host TAP network interface to a host bridge device.

     Use the network helper HELPER to configure the TAP interface and
     attach it to the bridge.  The default network helper executable is
     ‘/path/to/qemu-bridge-helper’ and the default bridge device is
     ‘br0’.

     Examples:

          #launch a QEMU instance with the default network helper to
          #connect a TAP device to bridge br0
          qemu-kvm linux.img -netdev bridge,id=n1 -device virtio-net,netdev=n1

          #launch a QEMU instance with the default network helper to
          #connect a TAP device to bridge qemubr0
          qemu-kvm linux.img -netdev bridge,br=qemubr0,id=n1 -device virtio-net,netdev=n1

‘-netdev socket,id=ID[,fd=H][,listen=[HOST]:PORT][,connect=HOST:PORT]’

     This host network backend can be used to connect the guest’s
     network to another QEMU virtual machine using a TCP socket
     connection.  If ‘listen’ is specified, QEMU waits for incoming
     connections on PORT (HOST is optional).  ‘connect’ is used to
     connect to another QEMU instance using the ‘listen’ option.  ‘fd’=H
     specifies an already opened TCP socket.

     Example:
          # launch a first QEMU instance
          qemu-kvm linux.img \
          -device e1000,netdev=n1,mac=52:54:00:12:34:56 \
          -netdev socket,id=n1,listen=:1234
          # connect the network of this instance to the network of the first instance
          qemu-kvm linux.img \
          -device e1000,netdev=n2,mac=52:54:00:12:34:57 \
          -netdev socket,id=n2,connect=127.0.0.1:1234

‘-netdev socket,id=ID[,fd=H][,mcast=MADDR:PORT[,localaddr=ADDR]]’

     Configure a socket host network backend to share the guest’s
     network traffic with another QEMU virtual machines using a UDP
     multicast socket, effectively making a bus for every QEMU with same
     multicast address MADDR and PORT.  NOTES:
       1. Several QEMU can be running on different hosts and share same
          bus (assuming correct multicast setup for these hosts).
       2. mcast support is compatible with User Mode Linux (argument
          ‘ethN=mcast’), see <http://user-mode-linux.sf.net>.
       3. Use ‘fd=h’ to specify an already opened UDP multicast socket.

     Example:
          # launch one QEMU instance
          qemu-kvm linux.img \
          -device e1000,netdev=n1,mac=52:54:00:12:34:56 \
          -netdev socket,id=n1,mcast=230.0.0.1:1234
          # launch another QEMU instance on same "bus"
          qemu-kvm linux.img \
          -device e1000,netdev=n2,mac=52:54:00:12:34:57 \
          -netdev socket,id=n2,mcast=230.0.0.1:1234
          # launch yet another QEMU instance on same "bus"
          qemu-kvm linux.img \
          -device e1000,netdev=n3,mac=52:54:00:12:34:58 \
          -netdev socket,id=n3,mcast=230.0.0.1:1234

     Example (User Mode Linux compat.):
          # launch QEMU instance (note mcast address selected is UML's default)
          qemu-kvm linux.img \
          -device e1000,netdev=n1,mac=52:54:00:12:34:56 \
          -netdev socket,id=n1,mcast=239.192.168.1:1102
          # launch UML
          /path/to/linux ubd0=/path/to/root_fs eth0=mcast

     Example (send packets from host’s 1.2.3.4):
          qemu-kvm linux.img \
          -device e1000,netdev=n1,mac=52:54:00:12:34:56 \
          -netdev socket,id=n1,mcast=239.192.168.1:1102,localaddr=1.2.3.4

‘-netdev l2tpv3,id=ID,src=SRCADDR,dst=DSTADDR[,srcport=SRCPORT][,dstport=DSTPORT],txsession=TXSESSION[,rxsession=RXSESSION][,ipv6][,udp][,cookie64][,counter][,pincounter][,txcookie=TXCOOKIE][,rxcookie=RXCOOKIE][,offset=OFFSET]’
     Configure a L2TPv3 pseudowire host network backend.  L2TPv3
     (RFC3391) is a popular protocol to transport Ethernet (and other
     Layer 2) data frames between two systems.  It is present in
     routers, firewalls and the Linux kernel (from version 3.3 onwards).

     This transport allows a VM to communicate to another VM, router or
     firewall directly.

     ‘src=SRCADDR’
          source address (mandatory)
     ‘dst=DSTADDR’
          destination address (mandatory)
     ‘udp’
          select udp encapsulation (default is ip).
     ‘srcport=SRCPORT’
          source udp port.
     ‘dstport=DSTPORT’
          destination udp port.
     ‘ipv6’
          force v6, otherwise defaults to v4.
     ‘rxcookie=RXCOOKIE’
     ‘txcookie=TXCOOKIE’
          Cookies are a weak form of security in the l2tpv3
          specification.  Their function is mostly to prevent
          misconfiguration.  By default they are 32 bit.
     ‘cookie64’
          Set cookie size to 64 bit instead of the default 32
     ‘counter=off’
          Force a ’cut-down’ L2TPv3 with no counter as in
          draft-mkonstan-l2tpext-keyed-ipv6-tunnel-00
     ‘pincounter=on’
          Work around broken counter handling in peer.  This may also
          help on networks which have packet reorder.
     ‘offset=OFFSET’
          Add an extra offset between header and data

     For example, to attach a VM running on host 4.3.2.1 via L2TPv3 to
     the bridge br-lan on the remote Linux host 1.2.3.4:
          # Setup tunnel on linux host using raw ip as encapsulation
          # on 1.2.3.4
          ip l2tp add tunnel remote 4.3.2.1 local 1.2.3.4 tunnel_id 1 peer_tunnel_id 1 \
          encap udp udp_sport 16384 udp_dport 16384
          ip l2tp add session tunnel_id 1 name vmtunnel0 session_id \
          0xFFFFFFFF peer_session_id 0xFFFFFFFF
          ifconfig vmtunnel0 mtu 1500
          ifconfig vmtunnel0 up
          brctl addif br-lan vmtunnel0


          # on 4.3.2.1
          # launch QEMU instance - if your network has reorder or is very lossy add ,pincounter

          qemu-kvm linux.img -device e1000,netdev=n1 \
          -netdev l2tpv3,id=n1,src=4.2.3.1,dst=1.2.3.4,udp,srcport=16384,dstport=16384,rxsession=0xffffffff,txsession=0xffffffff,counter


‘-netdev vde,id=ID[,sock=SOCKETPATH][,port=N][,group=GROUPNAME][,mode=OCTALMODE]’
     Configure VDE backend to connect to PORT N of a vde switch running
     on host and listening for incoming connections on SOCKETPATH.  Use
     GROUP GROUPNAME and MODE OCTALMODE to change default ownership and
     permissions for communication port.  This option is only available
     if QEMU has been compiled with vde support enabled.

     Example:
          # launch vde switch
          vde_switch -F -sock /tmp/myswitch
          # launch QEMU instance
          qemu-kvm linux.img -nic vde,sock=/tmp/myswitch

‘-netdev vhost-user,chardev=ID[,vhostforce=on|off][,queues=n]’

     Establish a vhost-user netdev, backed by a chardev ID.  The chardev
     should be a unix domain socket backed one.  The vhost-user uses a
     specifically defined protocol to pass vhost ioctl replacement
     messages to an application on the other end of the socket.  On
     non-MSIX guests, the feature can be forced with VHOSTFORCE.  Use
     ’queues=N’ to specify the number of queues to be created for
     multiqueue vhost-user.

     Example:
          qemu-kvm -m 512 -object memory-backend-file,id=mem,size=512M,mem-path=/hugetlbfs,share=on \
          -numa node,memdev=mem \
          -chardev socket,id=chr0,path=/path/to/socket \
          -netdev type=vhost-user,id=net0,chardev=chr0 \
          -device virtio-net-pci,netdev=net0

‘-netdev hubport,id=ID,hubid=HUBID[,netdev=ND]’

     Create a hub port on the emulated hub with ID HUBID.

     The hubport netdev lets you connect a NIC to a QEMU emulated hub
     instead of a single netdev.  Alternatively, you can also connect
     the hubport to another netdev with ID ND by using the ‘netdev=ND’
     option.

‘-net nic[,netdev=ND][,macaddr=MAC][,model=TYPE] [,name=NAME][,addr=ADDR][,vectors=V]’
     Legacy option to configure or create an on-board (or machine
     default) Network Interface Card(NIC) and connect it either to the
     emulated hub with ID 0 (i.e.  the default hub), or to the netdev
     ND.  The NIC is an e1000 by default on the PC target.  Optionally,
     the MAC address can be changed to MAC, the device address set to
     ADDR (PCI cards only), and a NAME can be assigned for use in
     monitor commands.  Optionally, for PCI cards, you can specify the
     number V of MSI-X vectors that the card should have; this option
     currently only affects virtio cards; set V = 0 to disable MSI-X. If
     no ‘-net’ option is specified, a single NIC is created.  QEMU can
     emulate several different models of network card.  Use ‘-net
     nic,model=help’ for a list of available devices for your target.

‘-net user|tap|bridge|socket|l2tpv3|vde[,...][,name=NAME]’
     Configure a host network backend (with the options corresponding to
     the same ‘-netdev’ option) and connect it to the emulated hub 0
     (the default hub).  Use NAME to specify the name of the hub port.

2.3.7 Character device options
------------------------------

The general form of a character device option is:
‘-chardev BACKEND,id=ID[,mux=on|off][,OPTIONS]’
     Backend is one of: ‘null’, ‘socket’, ‘udp’, ‘msmouse’, ‘vc’,
     ‘ringbuf’, ‘file’, ‘pipe’, ‘console’, ‘serial’, ‘pty’, ‘stdio’,
     ‘braille’, ‘tty’, ‘parallel’, ‘parport’, ‘spicevmc’, ‘spiceport’.
     The specific backend will determine the applicable options.

     Use ‘-chardev help’ to print all available chardev backend types.

     All devices must have an id, which can be any string up to 127
     characters long.  It is used to uniquely identify this device in
     other command line directives.

     A character device may be used in multiplexing mode by multiple
     front-ends.  Specify ‘mux=on’ to enable this mode.  A multiplexer
     is a "1:N" device, and here the "1" end is your specified chardev
     backend, and the "N" end is the various parts of QEMU that can talk
     to a chardev.  If you create a chardev with ‘id=myid’ and ‘mux=on’,
     QEMU will create a multiplexer with your specified ID, and you can
     then configure multiple front ends to use that chardev ID for their
     input/output.  Up to four different front ends can be connected to
     a single multiplexed chardev.  (Without multiplexing enabled, a
     chardev can only be used by a single front end.)  For instance you
     could use this to allow a single stdio chardev to be used by two
     serial ports and the QEMU monitor:

          -chardev stdio,mux=on,id=char0 \
          -mon chardev=char0,mode=readline \
          -serial chardev:char0 \
          -serial chardev:char0

     You can have more than one multiplexer in a system configuration;
     for instance you could have a TCP port multiplexed between UART 0
     and UART 1, and stdio multiplexed between the QEMU monitor and a
     parallel port:

          -chardev stdio,mux=on,id=char0 \
          -mon chardev=char0,mode=readline \
          -parallel chardev:char0 \
          -chardev tcp,...,mux=on,id=char1 \
          -serial chardev:char1 \
          -serial chardev:char1

     When you’re using a multiplexed character device, some escape
     sequences are interpreted in the input.  *Note Keys in the
     character backend multiplexer: mux_keys.

     Note that some other command line options may implicitly create
     multiplexed character backends; for instance ‘-serial mon:stdio’
     creates a multiplexed stdio backend connected to the serial port
     and the QEMU monitor, and ‘-nographic’ also multiplexes the console
     and the monitor to stdio.

     There is currently no support for multiplexing in the other
     direction (where a single QEMU front end takes input and output
     from multiple chardevs).

     Every backend supports the ‘logfile’ option, which supplies the
     path to a file to record all data transmitted via the backend.  The
     ‘logappend’ option controls whether the log file will be truncated
     or appended to when opened.

The available backends are:

‘-chardev null,id=ID’
     A void device.  This device will not emit any data, and will drop
     any data it receives.  The null backend does not take any options.

‘-chardev socket,id=ID[,TCP OPTIONS or UNIX OPTIONS][,server][,nowait][,telnet][,websocket][,reconnect=SECONDS][,tls-creds=ID][,tls-authz=ID]’

     Create a two-way stream socket, which can be either a TCP or a unix
     socket.  A unix socket will be created if ‘path’ is specified.
     Behaviour is undefined if TCP options are specified for a unix
     socket.

     ‘server’ specifies that the socket shall be a listening socket.

     ‘nowait’ specifies that QEMU should not block waiting for a client
     to connect to a listening socket.

     ‘telnet’ specifies that traffic on the socket should interpret
     telnet escape sequences.

     ‘websocket’ specifies that the socket uses WebSocket protocol for
     communication.

     ‘reconnect’ sets the timeout for reconnecting on non-server sockets
     when the remote end goes away.  qemu will delay this many seconds
     and then attempt to reconnect.  Zero disables reconnecting, and is
     the default.

     ‘tls-creds’ requests enablement of the TLS protocol for encryption,
     and specifies the id of the TLS credentials to use for the
     handshake.  The credentials must be previously created with the
     ‘-object tls-creds’ argument.

     ‘tls-auth’ provides the ID of the QAuthZ authorization object
     against which the client’s x509 distinguished name will be
     validated.  This object is only resolved at time of use, so can be
     deleted and recreated on the fly while the chardev server is
     active.  If missing, it will default to denying access.

     TCP and unix socket options are given below:

     ‘TCP options: port=PORT[,host=HOST][,to=TO][,ipv4][,ipv6][,nodelay]’

          ‘host’ for a listening socket specifies the local address to
          be bound.  For a connecting socket species the remote host to
          connect to.  ‘host’ is optional for listening sockets.  If not
          specified it defaults to ‘0.0.0.0’.

          ‘port’ for a listening socket specifies the local port to be
          bound.  For a connecting socket specifies the port on the
          remote host to connect to.  ‘port’ can be given as either a
          port number or a service name.  ‘port’ is required.

          ‘to’ is only relevant to listening sockets.  If it is
          specified, and ‘port’ cannot be bound, QEMU will attempt to
          bind to subsequent ports up to and including ‘to’ until it
          succeeds.  ‘to’ must be specified as a port number.

          ‘ipv4’ and ‘ipv6’ specify that either IPv4 or IPv6 must be
          used.  If neither is specified the socket may use either
          protocol.

          ‘nodelay’ disables the Nagle algorithm.

     ‘unix options: path=PATH’

          ‘path’ specifies the local path of the unix socket.  ‘path’ is
          required.

‘-chardev udp,id=ID[,host=HOST],port=PORT[,localaddr=LOCALADDR][,localport=LOCALPORT][,ipv4][,ipv6]’

     Sends all traffic from the guest to a remote host over UDP.

     ‘host’ specifies the remote host to connect to.  If not specified
     it defaults to ‘localhost’.

     ‘port’ specifies the port on the remote host to connect to.  ‘port’
     is required.

     ‘localaddr’ specifies the local address to bind to.  If not
     specified it defaults to ‘0.0.0.0’.

     ‘localport’ specifies the local port to bind to.  If not specified
     any available local port will be used.

     ‘ipv4’ and ‘ipv6’ specify that either IPv4 or IPv6 must be used.
     If neither is specified the device may use either protocol.

‘-chardev msmouse,id=ID’

     Forward QEMU’s emulated msmouse events to the guest.  ‘msmouse’
     does not take any options.

‘-chardev vc,id=ID[[,width=WIDTH][,height=HEIGHT]][[,cols=COLS][,rows=ROWS]]’

     Connect to a QEMU text console.  ‘vc’ may optionally be given a
     specific size.

     ‘width’ and ‘height’ specify the width and height respectively of
     the console, in pixels.

     ‘cols’ and ‘rows’ specify that the console be sized to fit a text
     console with the given dimensions.

‘-chardev ringbuf,id=ID[,size=SIZE]’

     Create a ring buffer with fixed size ‘size’.  SIZE must be a power
     of two and defaults to ‘64K’.

‘-chardev file,id=ID,path=PATH’

     Log all traffic received from the guest to a file.

     ‘path’ specifies the path of the file to be opened.  This file will
     be created if it does not already exist, and overwritten if it
     does.  ‘path’ is required.

‘-chardev pipe,id=ID,path=PATH’

     Create a two-way connection to the guest.  The behaviour differs
     slightly between Windows hosts and other hosts:

     On Windows, a single duplex pipe will be created at ‘\\.pipe\path’.

     On other hosts, 2 pipes will be created called ‘path.in’ and
     ‘path.out’.  Data written to ‘path.in’ will be received by the
     guest.  Data written by the guest can be read from ‘path.out’.
     QEMU will not create these fifos, and requires them to be present.

     ‘path’ forms part of the pipe path as described above.  ‘path’ is
     required.

‘-chardev console,id=ID’

     Send traffic from the guest to QEMU’s standard output.  ‘console’
     does not take any options.

     ‘console’ is only available on Windows hosts.

‘-chardev serial,id=ID,path=path’

     Send traffic from the guest to a serial device on the host.

     On Unix hosts serial will actually accept any tty device, not only
     serial lines.

     ‘path’ specifies the name of the serial device to open.

‘-chardev pty,id=ID’

     Create a new pseudo-terminal on the host and connect to it.  ‘pty’
     does not take any options.

     ‘pty’ is not available on Windows hosts.

‘-chardev stdio,id=ID[,signal=on|off]’
     Connect to standard input and standard output of the QEMU process.

     ‘signal’ controls if signals are enabled on the terminal, that
     includes exiting QEMU with the key sequence <Control-c>.  This
     option is enabled by default, use ‘signal=off’ to disable it.

‘-chardev braille,id=ID’

     Connect to a local BrlAPI server.  ‘braille’ does not take any
     options.

‘-chardev tty,id=ID,path=PATH’

     ‘tty’ is only available on Linux, Sun, FreeBSD, NetBSD, OpenBSD and
     DragonFlyBSD hosts.  It is an alias for ‘serial’.

     ‘path’ specifies the path to the tty.  ‘path’ is required.

‘-chardev parallel,id=ID,path=PATH’
‘-chardev parport,id=ID,path=PATH’

     ‘parallel’ is only available on Linux, FreeBSD and DragonFlyBSD
     hosts.

     Connect to a local parallel port.

     ‘path’ specifies the path to the parallel port device.  ‘path’ is
     required.

‘-chardev spicevmc,id=ID,debug=DEBUG,name=NAME’

     ‘spicevmc’ is only available when spice support is built in.

     ‘debug’ debug level for spicevmc

     ‘name’ name of spice channel to connect to

     Connect to a spice virtual machine channel, such as vdiport.

‘-chardev spiceport,id=ID,debug=DEBUG,name=NAME’

     ‘spiceport’ is only available when spice support is built in.

     ‘debug’ debug level for spicevmc

     ‘name’ name of spice port to connect to

     Connect to a spice port, allowing a Spice client to handle the
     traffic identified by a name (preferably a fqdn).

2.3.8 Bluetooth(R) options
--------------------------

‘-bt hci[...]’
     Defines the function of the corresponding Bluetooth HCI. -bt
     options are matched with the HCIs present in the chosen machine
     type.  For example when emulating a machine with only one HCI built
     into it, only the first ‘-bt hci[...]’ option is valid and defines
     the HCI’s logic.  The Transport Layer is decided by the machine
     type.  Currently the machines ‘n800’ and ‘n810’ have one HCI and
     all other machines have none.

     Note: This option and the whole bluetooth subsystem is considered
     as deprecated.  If you still use it, please send a mail to
     <qemu-devel@nongnu.org> where you describe your usecase.

     The following three types are recognized:

     ‘-bt hci,null’
          (default) The corresponding Bluetooth HCI assumes no internal
          logic and will not respond to any HCI commands or emit events.

     ‘-bt hci,host[:ID]’
          (‘bluez’ only) The corresponding HCI passes commands / events
          to / from the physical HCI identified by the name ID (default:
          ‘hci0’) on the computer running QEMU. Only available on
          ‘bluez’ capable systems like Linux.

     ‘-bt hci[,vlan=N]’
          Add a virtual, standard HCI that will participate in the
          Bluetooth scatternet N (default ‘0’).  Similarly to ‘-net’
          VLANs, devices inside a bluetooth network N can only
          communicate with other devices in the same network
          (scatternet).

‘-bt vhci[,vlan=N]’
     (Linux-host only) Create a HCI in scatternet N (default 0) attached
     to the host bluetooth stack instead of to the emulated target.
     This allows the host and target machines to participate in a common
     scatternet and communicate.  Requires the Linux ‘vhci’ driver
     installed.  Can be used as following:

          qemu-kvm [...OPTIONS...] -bt hci,vlan=5 -bt vhci,vlan=5

‘-bt device:DEV[,vlan=N]’
     Emulate a bluetooth device DEV and place it in network N (default
     ‘0’).  QEMU can only emulate one type of bluetooth devices
     currently:

     ‘keyboard’
          Virtual wireless keyboard implementing the HIDP bluetooth
          profile.

2.3.9 TPM device options
------------------------

The general form of a TPM device option is:

‘-tpmdev BACKEND,id=ID[,OPTIONS]’

     The specific backend type will determine the applicable options.
     The ‘-tpmdev’ option creates the TPM backend and requires a
     ‘-device’ option that specifies the TPM frontend interface model.

     Use ‘-tpmdev help’ to print all available TPM backend types.

The available backends are:

‘-tpmdev passthrough,id=ID,path=PATH,cancel-path=CANCEL-PATH’

     (Linux-host only) Enable access to the host’s TPM using the
     passthrough driver.

     ‘path’ specifies the path to the host’s TPM device, i.e., on a
     Linux host this would be ‘/dev/tpm0’.  ‘path’ is optional and by
     default ‘/dev/tpm0’ is used.

     ‘cancel-path’ specifies the path to the host TPM device’s sysfs
     entry allowing for cancellation of an ongoing TPM command.
     ‘cancel-path’ is optional and by default QEMU will search for the
     sysfs entry to use.

     Some notes about using the host’s TPM with the passthrough driver:

     The TPM device accessed by the passthrough driver must not be used
     by any other application on the host.

     Since the host’s firmware (BIOS/UEFI) has already initialized the
     TPM, the VM’s firmware (BIOS/UEFI) will not be able to initialize
     the TPM again and may therefore not show a TPM-specific menu that
     would otherwise allow the user to configure the TPM, e.g., allow
     the user to enable/disable or activate/deactivate the TPM. Further,
     if TPM ownership is released from within a VM then the host’s TPM
     will get disabled and deactivated.  To enable and activate the TPM
     again afterwards, the host has to be rebooted and the user is
     required to enter the firmware’s menu to enable and activate the
     TPM. If the TPM is left disabled and/or deactivated most TPM
     commands will fail.

     To create a passthrough TPM use the following two options:
          -tpmdev passthrough,id=tpm0 -device tpm-tis,tpmdev=tpm0
     Note that the ‘-tpmdev’ id is ‘tpm0’ and is referenced by
     ‘tpmdev=tpm0’ in the device option.

‘-tpmdev emulator,id=ID,chardev=DEV’

     (Linux-host only) Enable access to a TPM emulator using Unix domain
     socket based chardev backend.

     ‘chardev’ specifies the unique ID of a character device backend
     that provides connection to the software TPM server.

     To create a TPM emulator backend device with chardev socket
     backend:

          -chardev socket,id=chrtpm,path=/tmp/swtpm-sock -tpmdev emulator,id=tpm0,chardev=chrtpm -device tpm-tis,tpmdev=tpm0


2.3.10 Linux/Multiboot boot specific
------------------------------------

When using these options, you can use a given Linux or Multiboot kernel
without installing it in the disk image.  It can be useful for easier
testing of various kernels.

‘-kernel BZIMAGE’
     Use BZIMAGE as kernel image.  The kernel can be either a Linux
     kernel or in multiboot format.
‘-append CMDLINE’
     Use CMDLINE as kernel command line
‘-initrd FILE’
     Use FILE as initial ram disk.

‘-initrd "FILE1 arg=foo,FILE2"’

     This syntax is only available with multiboot.

     Use FILE1 and FILE2 as modules and pass arg=foo as parameter to the
     first module.
‘-dtb FILE’
     Use FILE as a device tree binary (dtb) image and pass it to the
     kernel on boot.

2.3.11 Debug/Expert options
---------------------------

‘-fw_cfg [name=]NAME,file=FILE’
     Add named fw_cfg entry with contents from file FILE.

‘-fw_cfg [name=]NAME,string=STR’
     Add named fw_cfg entry with contents from string STR.

     The terminating NUL character of the contents of STR will not be
     included as part of the fw_cfg item data.  To insert contents with
     embedded NUL characters, you have to use the FILE parameter.

     The fw_cfg entries are passed by QEMU through to the guest.

     Example:
          -fw_cfg name=opt/com.mycompany/blob,file=./my_blob.bin
     creates an fw_cfg entry named opt/com.mycompany/blob with contents
     from ./my_blob.bin.

‘-serial DEV’
     Redirect the virtual serial port to host character device DEV.  The
     default device is ‘vc’ in graphical mode and ‘stdio’ in non
     graphical mode.

     This option can be used several times to simulate up to 4 serial
     ports.

     Use ‘-serial none’ to disable all serial ports.

     Available character devices are:
     ‘vc[:WxH]’
          Virtual console.  Optionally, a width and height can be given
          in pixel with
               vc:800x600
          It is also possible to specify width or height in characters:
               vc:80Cx24C
     ‘pty’
          [Linux only] Pseudo TTY (a new PTY is automatically allocated)
     ‘none’
          No device is allocated.
     ‘null’
          void device
     ‘chardev:ID’
          Use a named character device defined with the ‘-chardev’
          option.
     ‘/dev/XXX’
          [Linux only] Use host tty, e.g.  ‘/dev/ttyS0’.  The host
          serial port parameters are set according to the emulated ones.
     ‘/dev/parportN’
          [Linux only, parallel port only] Use host parallel port N.
          Currently SPP and EPP parallel port features can be used.
     ‘file:FILENAME’
          Write output to FILENAME.  No character can be read.
     ‘stdio’
          [Unix only] standard input/output
     ‘pipe:FILENAME’
          name pipe FILENAME
     ‘COMN’
          [Windows only] Use host serial port N
     ‘udp:[REMOTE_HOST]:REMOTE_PORT[@[SRC_IP]:SRC_PORT]’
          This implements UDP Net Console.  When REMOTE_HOST or SRC_IP
          are not specified they default to ‘0.0.0.0’.  When not using a
          specified SRC_PORT a random port is automatically chosen.

          If you just want a simple readonly console you can use
          ‘netcat’ or ‘nc’, by starting QEMU with: ‘-serial udp::4555’
          and nc as: ‘nc -u -l -p 4555’.  Any time QEMU writes something
          to that port it will appear in the netconsole session.

          If you plan to send characters back via netconsole or you want
          to stop and start QEMU a lot of times, you should have QEMU
          use the same source port each time by using something like
          ‘-serial udp::4555@:4556’ to QEMU. Another approach is to use
          a patched version of netcat which can listen to a TCP port and
          send and receive characters via udp.  If you have a patched
          version of netcat which activates telnet remote echo and
          single char transfer, then you can use the following options
          to set up a netcat redirector to allow telnet on port 5555 to
          access the QEMU port.
          ‘QEMU Options:’
               -serial udp::4555@:4556
          ‘netcat options:’
               -u -P 4555 -L 0.0.0.0:4556 -t -p 5555 -I -T
          ‘telnet options:’
               localhost 5555

     ‘tcp:[HOST]:PORT[,SERVER][,nowait][,nodelay][,reconnect=SECONDS]’
          The TCP Net Console has two modes of operation.  It can send
          the serial I/O to a location or wait for a connection from a
          location.  By default the TCP Net Console is sent to HOST at
          the PORT.  If you use the SERVER option QEMU will wait for a
          client socket application to connect to the port before
          continuing, unless the ‘nowait’ option was specified.  The
          ‘nodelay’ option disables the Nagle buffering algorithm.  The
          ‘reconnect’ option only applies if NOSERVER is set, if the
          connection goes down it will attempt to reconnect at the given
          interval.  If HOST is omitted, 0.0.0.0 is assumed.  Only one
          TCP connection at a time is accepted.  You can use ‘telnet’ to
          connect to the corresponding character device.
          ‘Example to send tcp console to 192.168.0.2 port 4444’
               -serial tcp:192.168.0.2:4444
          ‘Example to listen and wait on port 4444 for connection’
               -serial tcp::4444,server
          ‘Example to not wait and listen on ip 192.168.0.100 port 4444’
               -serial tcp:192.168.0.100:4444,server,nowait

     ‘telnet:HOST:PORT[,server][,nowait][,nodelay]’
          The telnet protocol is used instead of raw tcp sockets.  The
          options work the same as if you had specified ‘-serial tcp’.
          The difference is that the port acts like a telnet server or
          client using telnet option negotiation.  This will also allow
          you to send the MAGIC_SYSRQ sequence if you use a telnet that
          supports sending the break sequence.  Typically in unix telnet
          you do it with Control-] and then type "send break" followed
          by pressing the enter key.

     ‘websocket:HOST:PORT,server[,nowait][,nodelay]’
          The WebSocket protocol is used instead of raw tcp socket.  The
          port acts as a WebSocket server.  Client mode is not
          supported.

     ‘unix:PATH[,server][,nowait][,reconnect=SECONDS]’
          A unix domain socket is used instead of a tcp socket.  The
          option works the same as if you had specified ‘-serial tcp’
          except the unix domain socket PATH is used for connections.

     ‘mon:DEV_STRING’
          This is a special option to allow the monitor to be
          multiplexed onto another serial port.  The monitor is accessed
          with key sequence of <Control-a> and then pressing <c>.
          DEV_STRING should be any one of the serial devices specified
          above.  An example to multiplex the monitor onto a telnet
          server listening on port 4444 would be:
          ‘-serial mon:telnet::4444,server,nowait’
          When the monitor is multiplexed to stdio in this way, Ctrl+C
          will not terminate QEMU any more but will be passed to the
          guest instead.

     ‘braille’
          Braille device.  This will use BrlAPI to display the braille
          output on a real or fake device.

     ‘msmouse’
          Three button serial mouse.  Configure the guest to use
          Microsoft protocol.
‘-parallel DEV’
     Redirect the virtual parallel port to host device DEV (same devices
     as the serial port).  On Linux hosts, ‘/dev/parportN’ can be used
     to use hardware devices connected on the corresponding host
     parallel port.

     This option can be used several times to simulate up to 3 parallel
     ports.

     Use ‘-parallel none’ to disable all parallel ports.
‘-monitor DEV’
     Redirect the monitor to host device DEV (same devices as the serial
     port).  The default device is ‘vc’ in graphical mode and ‘stdio’ in
     non graphical mode.  Use ‘-monitor none’ to disable the default
     monitor.
‘-qmp DEV’
     Like -monitor but opens in ’control’ mode.
‘-qmp-pretty DEV’
     Like -qmp but uses pretty JSON formatting.
‘-mon [chardev=]name[,mode=readline|control][,pretty[=on|off]]’
     Setup monitor on chardev NAME.  ‘pretty’ turns on JSON pretty
     printing easing human reading and debugging.
‘-debugcon DEV’
     Redirect the debug console to host device DEV (same devices as the
     serial port).  The debug console is an I/O port which is typically
     port 0xe9; writing to that I/O port sends output to this device.
     The default device is ‘vc’ in graphical mode and ‘stdio’ in non
     graphical mode.
‘-pidfile FILE’
     Store the QEMU process PID in FILE.  It is useful if you launch
     QEMU from a script.
‘-singlestep’
     Run the emulation in single step mode.
‘--preconfig’
     Pause QEMU for interactive configuration before the machine is
     created, which allows querying and configuring properties that will
     affect machine initialization.  Use QMP command ’x-exit-preconfig’
     to exit the preconfig state and move to the next state (i.e.  run
     guest if -S isn’t used or pause the second time if -S is used).
     This option is experimental.
‘-S’
     Do not start CPU at startup (you must type ’c’ in the monitor).
‘-realtime mlock=on|off’
     Run qemu-kvm with realtime features.  mlocking qemu-kvm and guest
     memory can be enabled via ‘mlock=on’ (enabled by default).
‘-overcommit mem-lock=on|off’
‘-overcommit cpu-pm=on|off’
     Run qemu with hints about host resource overcommit.  The default is
     to assume that host overcommits all resources.

     Locking qemu and guest memory can be enabled via ‘mem-lock=on’
     (disabled by default).  This works when host memory is not
     overcommitted and reduces the worst-case latency for guest.  This
     is equivalent to ‘realtime’.

     Guest ability to manage power state of host cpus (increasing
     latency for other processes on the same host cpu, but decreasing
     latency for guest) can be enabled via ‘cpu-pm=on’ (disabled by
     default).  This works best when host CPU is not overcommitted.
     When used, host estimates of CPU cycle and power utilization will
     be incorrect, not taking into account guest idle time.
‘-gdb DEV’
     Wait for gdb connection on device DEV (*note gdb_usage::).  Typical
     connections will likely be TCP-based, but also UDP, pseudo TTY, or
     even stdio are reasonable use case.  The latter is allowing to
     start QEMU from within gdb and establish the connection via a pipe:
          (gdb) target remote | exec qemu-kvm -gdb stdio ...
‘-s’
     Shorthand for -gdb tcp::1234, i.e.  open a gdbserver on TCP port
     1234 (*note gdb_usage::).
‘-d ITEM1[,...]’
     Enable logging of specified items.  Use ’-d help’ for a list of log
     items.
‘-D LOGFILE’
     Output log in LOGFILE instead of to stderr
‘-dfilter RANGE1[,...]’
     Filter debug output to that relevant to a range of target
     addresses.  The filter spec can be either START+SIZE, START-SIZE or
     START..END where START END and SIZE are the addresses and sizes
     required.  For example:
          -dfilter 0x8000..0x8fff,0xffffffc000080000+0x200,0xffffffc000060000-0x1000
     Will dump output for any code in the 0x1000 sized block starting at
     0x8000 and the 0x200 sized block starting at 0xffffffc000080000 and
     another 0x1000 sized block starting at 0xffffffc00005f000.
‘-seed NUMBER’
     Force the guest to use a deterministic pseudo-random number
     generator, seeded with NUMBER.  This does not affect crypto
     routines within the host.
‘-L PATH’
     Set the directory for the BIOS, VGA BIOS and keymaps.

     To list all the data directories, use ‘-L help’.
‘-bios FILE’
     Set the filename for the BIOS.
‘-enable-kvm’
     Enable KVM full virtualization support.  This option is only
     available if KVM support is enabled when compiling.
‘-xen-domid ID’
     Specify xen guest domain ID (XEN only).
‘-xen-attach’
     Attach to existing xen domain.  libxl will use this when starting
     QEMU (XEN only).  Restrict set of available xen operations to
     specified domain id (XEN only).
‘-no-reboot’
     Exit instead of rebooting.
‘-no-shutdown’
     Don’t exit QEMU on guest shutdown, but instead only stop the
     emulation.  This allows for instance switching to monitor to commit
     changes to the disk image.
‘-loadvm FILE’
     Start right away with a saved state (‘loadvm’ in monitor)
‘-daemonize’
     Daemonize the QEMU process after initialization.  QEMU will not
     detach from standard IO until it is ready to receive connections on
     any of its devices.  This option is a useful way for external
     programs to launch QEMU without having to cope with initialization
     race conditions.
‘-option-rom FILE’
     Load the contents of FILE as an option ROM. This option is useful
     to load things like EtherBoot.

‘-rtc [base=utc|localtime|DATETIME][,clock=host|rt|vm][,driftfix=none|slew]’
     Specify ‘base’ as ‘utc’ or ‘localtime’ to let the RTC start at the
     current UTC or local time, respectively.  ‘localtime’ is required
     for correct date in MS-DOS or Windows.  To start at a specific
     point in time, provide DATETIME in the format ‘2006-06-17T16:01:21’
     or ‘2006-06-17’.  The default base is UTC.

     By default the RTC is driven by the host system time.  This allows
     using of the RTC as accurate reference clock inside the guest,
     specifically if the host time is smoothly following an accurate
     external reference clock, e.g.  via NTP. If you want to isolate the
     guest time from the host, you can set ‘clock’ to ‘rt’ instead,
     which provides a host monotonic clock if host support it.  To even
     prevent the RTC from progressing during suspension, you can set
     ‘clock’ to ‘vm’ (virtual clock).  ‘clock=vm’ is recommended
     especially in icount mode in order to preserve determinism;
     however, note that in icount mode the speed of the virtual clock is
     variable and can in general differ from the host clock.

     Enable ‘driftfix’ (i386 targets only) if you experience time drift
     problems, specifically with Windows’ ACPI HAL. This option will try
     to figure out how many timer interrupts were not processed by the
     Windows guest and will re-inject them.
‘-icount [shift=N|auto][,rr=record|replay,rrfile=FILENAME,rrsnapshot=SNAPSHOT]’
     Enable virtual instruction counter.  The virtual cpu will execute
     one instruction every 2^N ns of virtual time.  If ‘auto’ is
     specified then the virtual cpu speed will be automatically adjusted
     to keep virtual time within a few seconds of real time.

     When the virtual cpu is sleeping, the virtual time will advance at
     default speed unless ‘sleep=on|off’ is specified.  With
     ‘sleep=on|off’, the virtual time will jump to the next timer
     deadline instantly whenever the virtual cpu goes to sleep mode and
     will not advance if no timer is enabled.  This behavior give
     deterministic execution times from the guest point of view.

     Note that while this option can give deterministic behavior, it
     does not provide cycle accurate emulation.  Modern CPUs contain
     superscalar out of order cores with complex cache hierarchies.  The
     number of instructions executed often has little or no correlation
     with actual performance.

     ‘align=on’ will activate the delay algorithm which will try to
     synchronise the host clock and the virtual clock.  The goal is to
     have a guest running at the real frequency imposed by the shift
     option.  Whenever the guest clock is behind the host clock and if
     ‘align=on’ is specified then we print a message to the user to
     inform about the delay.  Currently this option does not work when
     ‘shift’ is ‘auto’.  Note: The sync algorithm will work for those
     shift values for which the guest clock runs ahead of the host
     clock.  Typically this happens when the shift value is high (how
     high depends on the host machine).

     When ‘rr’ option is specified deterministic record/replay is
     enabled.  Replay log is written into FILENAME file in record mode
     and read from this file in replay mode.

     Option rrsnapshot is used to create new vm snapshot named SNAPSHOT
     at the start of execution recording.  In replay mode this option is
     used to load the initial VM state.
‘-watchdog MODEL’
     Create a virtual hardware watchdog device.  Once enabled (by a
     guest action), the watchdog must be periodically polled by an agent
     inside the guest or else the guest will be restarted.  Choose a
     model for which your guest has drivers.

     The MODEL is the model of hardware watchdog to emulate.  Use
     ‘-watchdog help’ to list available hardware models.  Only one
     watchdog can be enabled for a guest.

     The following models may be available:
     ‘ib700’
          iBASE 700 is a very simple ISA watchdog with a single timer.
     ‘i6300esb’
          Intel 6300ESB I/O controller hub is a much more featureful
          PCI-based dual-timer watchdog.
     ‘diag288’
          A virtual watchdog for s390x backed by the diagnose 288
          hypercall (currently KVM only).
‘-watchdog-action ACTION’

     The ACTION controls what QEMU will do when the watchdog timer
     expires.  The default is ‘reset’ (forcefully reset the guest).
     Other possible actions are: ‘shutdown’ (attempt to gracefully
     shutdown the guest), ‘poweroff’ (forcefully poweroff the guest),
     ‘inject-nmi’ (inject a NMI into the guest), ‘pause’ (pause the
     guest), ‘debug’ (print a debug message and continue), or ‘none’ (do
     nothing).

     Note that the ‘shutdown’ action requires that the guest responds to
     ACPI signals, which it may not be able to do in the sort of
     situations where the watchdog would have expired, and thus
     ‘-watchdog-action shutdown’ is not recommended for production use.

     Examples:

     ‘-watchdog i6300esb -watchdog-action pause’
     ‘-watchdog ib700’

‘-echr NUMERIC_ASCII_VALUE’
     Change the escape character used for switching to the monitor when
     using monitor and serial sharing.  The default is ‘0x01’ when using
     the ‘-nographic’ option.  ‘0x01’ is equal to pressing ‘Control-a’.
     You can select a different character from the ascii control keys
     where 1 through 26 map to Control-a through Control-z.  For
     instance you could use the either of the following to change the
     escape character to Control-t.
     ‘-echr 0x14’
     ‘-echr 20’
‘-show-cursor’
     Show cursor.
‘-tb-size N’
     Set TB size.
‘-incoming tcp:[HOST]:PORT[,to=MAXPORT][,ipv4][,ipv6]’
‘-incoming rdma:HOST:PORT[,ipv4][,ipv6]’
     Prepare for incoming migration, listen on a given tcp port.

‘-incoming unix:SOCKETPATH’
     Prepare for incoming migration, listen on a given unix socket.

‘-incoming fd:FD’
     Accept incoming migration from a given filedescriptor.

‘-incoming exec:CMDLINE’
     Accept incoming migration as an output from specified external
     command.

‘-incoming defer’
     Wait for the URI to be specified via migrate_incoming.  The monitor
     can be used to change settings (such as migration parameters) prior
     to issuing the migrate_incoming to allow the migration to begin.
‘-only-migratable’
     Only allow migratable devices.  Devices will not be allowed to
     enter an unmigratable state.
‘-nodefaults’
     Don’t create default devices.  Normally, QEMU sets the default
     devices like serial port, parallel port, virtual console, monitor
     device, VGA adapter, floppy and CD-ROM drive and others.  The
     ‘-nodefaults’ option will disable all those default devices.
‘-chroot DIR’
     Immediately before starting guest execution, chroot to the
     specified directory.  Especially useful in combination with -runas.
‘-runas USER’
     Immediately before starting guest execution, drop root privileges,
     switching to the specified user.
‘-prom-env VARIABLE=VALUE’
     Set OpenBIOS nvram VARIABLE to given VALUE (PPC, SPARC only).
‘-semihosting’
     Enable semihosting mode (ARM, M68K, Xtensa, MIPS, Nios II only).
‘-semihosting-config [enable=on|off][,target=native|gdb|auto][,chardev=id][,arg=str[,...]]’
     Enable and configure semihosting (ARM, M68K, Xtensa, MIPS, Nios II
     only).
     ‘target=native|gdb|auto’
          Defines where the semihosting calls will be addressed, to QEMU
          (‘native’) or to GDB (‘gdb’).  The default is ‘auto’, which
          means ‘gdb’ during debug sessions and ‘native’ otherwise.
     ‘chardev=STR1’
          Send the output to a chardev backend output for native or auto
          output when not in gdb
     ‘arg=STR1,arg=STR2,...’
          Allows the user to pass input arguments, and can be used
          multiple times to build up a list.  The old-style
          ‘-kernel’/‘-append’ method of passing a command line is still
          supported for backward compatibility.  If both the
          ‘--semihosting-config arg’ and the ‘-kernel’/‘-append’ are
          specified, the former is passed to semihosting as it always
          takes precedence.
‘-old-param’
     Old param mode (ARM only).
‘-sandbox ARG[,obsolete=STRING][,elevateprivileges=STRING][,spawn=STRING][,resourcecontrol=STRING]’
     Enable Seccomp mode 2 system call filter.  ’on’ will enable syscall
     filtering and ’off’ will disable it.  The default is ’off’.
     ‘obsolete=STRING’
          Enable Obsolete system calls
     ‘elevateprivileges=STRING’
          Disable set*uid|gid system calls
     ‘spawn=STRING’
          Disable *fork and execve
     ‘resourcecontrol=STRING’
          Disable process affinity and schedular priority
‘-readconfig FILE’
     Read device configuration from FILE.  This approach is useful when
     you want to spawn QEMU process with many command line options but
     you don’t want to exceed the command line character limit.
‘-writeconfig FILE’
     Write device configuration to FILE.  The FILE can be either
     filename to save command line and device configuration into file or
     dash ‘-’) character to print the output to stdout.  This can be
     later used as input file for ‘-readconfig’ option.
‘-no-user-config’
     The ‘-no-user-config’ option makes QEMU not load any of the
     user-provided config files on SYSCONFDIR.
‘-trace [[enable=]PATTERN][,events=FILE][,file=FILE]’
     Specify tracing options.

     ‘[enable=]PATTERN’
          Immediately enable events matching PATTERN (either event name
          or a globbing pattern).  This option is only available if QEMU
          has been compiled with the SIMPLE, LOG or FTRACE tracing
          backend.  To specify multiple events or patterns, specify the
          ‘-trace’ option multiple times.

          Use ‘-trace help’ to print a list of names of trace points.

     ‘events=FILE’
          Immediately enable events listed in FILE.  The file must
          contain one event name (as listed in the ‘trace-events-all’
          file) per line; globbing patterns are accepted too.  This
          option is only available if QEMU has been compiled with the
          SIMPLE, LOG or FTRACE tracing backend.

     ‘file=FILE’
          Log output traces to FILE.  This option is only available if
          QEMU has been compiled with the SIMPLE tracing backend.
‘-plugin file=FILE[,arg=STRING]’

     Load a plugin.

     ‘file=FILE’
          Load the given plugin from a shared library file.
     ‘arg=STRING’
          Argument string passed to the plugin.  (Can be given multiple
          times.)
‘-enable-fips’
     Enable FIPS 140-2 compliance mode.
‘-msg timestamp[=on|off]’
     prepend a timestamp to each log message.(default:on)
‘-dump-vmstate FILE’
     Dump json-encoded vmstate information for current machine type to
     file in FILE
‘-enable-sync-profile’
     Enable synchronization profiling.

2.3.12 Generic object creation
------------------------------

‘-object TYPENAME[,PROP1=VALUE1,...]’
     Create a new object of type TYPENAME setting properties in the
     order they are specified.  Note that the ’id’ property must be set.
     These objects are placed in the ’/objects’ path.

     ‘-object memory-backend-file,id=ID,size=SIZE,mem-path=DIR,share=ON|OFF,discard-data=ON|OFF,merge=ON|OFF,dump=ON|OFF,prealloc=ON|OFF,host-nodes=HOST-NODES,policy=DEFAULT|PREFERRED|BIND|INTERLEAVE,align=ALIGN’

          Creates a memory file backend object, which can be used to
          back the guest RAM with huge pages.

          The ‘id’ parameter is a unique ID that will be used to
          reference this memory region when configuring the ‘-numa’
          argument.

          The ‘size’ option provides the size of the memory region, and
          accepts common suffixes, eg ‘500M’.

          The ‘mem-path’ provides the path to either a shared memory or
          huge page filesystem mount.

          The ‘share’ boolean option determines whether the memory
          region is marked as private to QEMU, or shared.  The latter
          allows a co-operating external process to access the QEMU
          memory region.

          The ‘share’ is also required for pvrdma devices due to
          limitations in the RDMA API provided by Linux.

          Setting share=on might affect the ability to configure NUMA
          bindings for the memory backend under some circumstances, see
          Documentation/vm/numa_memory_policy.txt on the Linux kernel
          source tree for additional details.

          Setting the ‘discard-data’ boolean option to ON indicates that
          file contents can be destroyed when QEMU exits, to avoid
          unnecessarily flushing data to the backing file.  Note that
          ‘discard-data’ is only an optimization, and QEMU might not
          discard file contents if it aborts unexpectedly or is
          terminated using SIGKILL.

          The ‘merge’ boolean option enables memory merge, also known as
          MADV_MERGEABLE, so that Kernel Samepage Merging will consider
          the pages for memory deduplication.

          Setting the ‘dump’ boolean option to OFF excludes the memory
          from core dumps.  This feature is also known as MADV_DONTDUMP.

          The ‘prealloc’ boolean option enables memory preallocation.

          The ‘host-nodes’ option binds the memory range to a list of
          NUMA host nodes.

          The ‘policy’ option sets the NUMA policy to one of the
          following values:

          ‘DEFAULT’
               default host policy

          ‘PREFERRED’
               prefer the given host node list for allocation

          ‘BIND’
               restrict memory allocation to the given host node list

          ‘INTERLEAVE’
               interleave memory allocations across the given host node
               list

          The ‘align’ option specifies the base address alignment when
          QEMU mmap(2) ‘mem-path’, and accepts common suffixes, eg ‘2M’.
          Some backend store specified by ‘mem-path’ requires an
          alignment different than the default one used by QEMU, eg the
          device DAX /dev/dax0.0 requires 2M alignment rather than 4K.
          In such cases, users can specify the required alignment via
          this option.

          The ‘pmem’ option specifies whether the backing file specified
          by ‘mem-path’ is in host persistent memory that can be
          accessed using the SNIA NVM programming model (e.g.  Intel
          NVDIMM). If ‘pmem’ is set to ’on’, QEMU will take necessary
          operations to guarantee the persistence of its own writes to
          ‘mem-path’ (e.g.  in vNVDIMM label emulation and live
          migration).  Also, we will map the backend-file with MAP_SYNC
          flag, which ensures the file metadata is in sync for
          ‘mem-path’ in case of host crash or a power failure.  MAP_SYNC
          requires support from both the host kernel (since Linux kernel
          4.15) and the filesystem of ‘mem-path’ mounted with DAX
          option.

     ‘-object memory-backend-ram,id=ID,merge=ON|OFF,dump=ON|OFF,share=ON|OFF,prealloc=ON|OFF,size=SIZE,host-nodes=HOST-NODES,policy=DEFAULT|PREFERRED|BIND|INTERLEAVE’

          Creates a memory backend object, which can be used to back the
          guest RAM. Memory backend objects offer more control than the
          ‘-m’ option that is traditionally used to define guest RAM.
          Please refer to ‘memory-backend-file’ for a description of the
          options.

     ‘-object memory-backend-memfd,id=ID,merge=ON|OFF,dump=ON|OFF,share=ON|OFF,prealloc=ON|OFF,size=SIZE,host-nodes=HOST-NODES,policy=DEFAULT|PREFERRED|BIND|INTERLEAVE,seal=ON|OFF,hugetlb=ON|OFF,hugetlbsize=SIZE’

          Creates an anonymous memory file backend object, which allows
          QEMU to share the memory with an external process (e.g.  when
          using vhost-user).  The memory is allocated with memfd and
          optional sealing.  (Linux only)

          The ‘seal’ option creates a sealed-file, that will block
          further resizing the memory (’on’ by default).

          The ‘hugetlb’ option specify the file to be created resides in
          the hugetlbfs filesystem (since Linux 4.14).  Used in
          conjunction with the ‘hugetlb’ option, the ‘hugetlbsize’
          option specify the hugetlb page size on systems that support
          multiple hugetlb page sizes (it must be a power of 2 value
          supported by the system).

          In some versions of Linux, the ‘hugetlb’ option is
          incompatible with the ‘seal’ option (requires at least Linux
          4.16).

          Please refer to ‘memory-backend-file’ for a description of the
          other options.

          The ‘share’ boolean option is ON by default with memfd.

     ‘-object rng-builtin,id=ID’

          Creates a random number generator backend which obtains
          entropy from QEMU builtin functions.  The ‘id’ parameter is a
          unique ID that will be used to reference this entropy backend
          from the ‘virtio-rng’ device.  By default, the ‘virtio-rng’
          device uses this RNG backend.

     ‘-object rng-random,id=ID,filename=/DEV/RANDOM’

          Creates a random number generator backend which obtains
          entropy from a device on the host.  The ‘id’ parameter is a
          unique ID that will be used to reference this entropy backend
          from the ‘virtio-rng’ device.  The ‘filename’ parameter
          specifies which file to obtain entropy from and if omitted
          defaults to ‘/dev/urandom’.

     ‘-object rng-egd,id=ID,chardev=CHARDEVID’

          Creates a random number generator backend which obtains
          entropy from an external daemon running on the host.  The ‘id’
          parameter is a unique ID that will be used to reference this
          entropy backend from the ‘virtio-rng’ device.  The ‘chardev’
          parameter is the unique ID of a character device backend that
          provides the connection to the RNG daemon.

     ‘-object tls-creds-anon,id=ID,endpoint=ENDPOINT,dir=/PATH/TO/CRED/DIR,verify-peer=ON|OFF’

          Creates a TLS anonymous credentials object, which can be used
          to provide TLS support on network backends.  The ‘id’
          parameter is a unique ID which network backends will use to
          access the credentials.  The ‘endpoint’ is either ‘server’ or
          ‘client’ depending on whether the QEMU network backend that
          uses the credentials will be acting as a client or as a
          server.  If ‘verify-peer’ is enabled (the default) then once
          the handshake is completed, the peer credentials will be
          verified, though this is a no-op for anonymous credentials.

          The DIR parameter tells QEMU where to find the credential
          files.  For server endpoints, this directory may contain a
          file DH-PARAMS.PEM providing diffie-hellman parameters to use
          for the TLS server.  If the file is missing, QEMU will
          generate a set of DH parameters at startup.  This is a
          computationally expensive operation that consumes random pool
          entropy, so it is recommended that a persistent set of
          parameters be generated upfront and saved.

     ‘-object tls-creds-psk,id=ID,endpoint=ENDPOINT,dir=/PATH/TO/KEYS/DIR[,username=USERNAME]’

          Creates a TLS Pre-Shared Keys (PSK) credentials object, which
          can be used to provide TLS support on network backends.  The
          ‘id’ parameter is a unique ID which network backends will use
          to access the credentials.  The ‘endpoint’ is either ‘server’
          or ‘client’ depending on whether the QEMU network backend that
          uses the credentials will be acting as a client or as a
          server.  For clients only, ‘username’ is the username which
          will be sent to the server.  If omitted it defaults to “qemu”.

          The DIR parameter tells QEMU where to find the keys file.  It
          is called “DIR/keys.psk” and contains “username:key” pairs.
          This file can most easily be created using the GnuTLS
          ‘psktool’ program.

          For server endpoints, DIR may also contain a file
          DH-PARAMS.PEM providing diffie-hellman parameters to use for
          the TLS server.  If the file is missing, QEMU will generate a
          set of DH parameters at startup.  This is a computationally
          expensive operation that consumes random pool entropy, so it
          is recommended that a persistent set of parameters be
          generated up front and saved.

     ‘-object tls-creds-x509,id=ID,endpoint=ENDPOINT,dir=/PATH/TO/CRED/DIR,priority=PRIORITY,verify-peer=ON|OFF,passwordid=ID’

          Creates a TLS anonymous credentials object, which can be used
          to provide TLS support on network backends.  The ‘id’
          parameter is a unique ID which network backends will use to
          access the credentials.  The ‘endpoint’ is either ‘server’ or
          ‘client’ depending on whether the QEMU network backend that
          uses the credentials will be acting as a client or as a
          server.  If ‘verify-peer’ is enabled (the default) then once
          the handshake is completed, the peer credentials will be
          verified.  With x509 certificates, this implies that the
          clients must be provided with valid client certificates too.

          The DIR parameter tells QEMU where to find the credential
          files.  For server endpoints, this directory may contain a
          file DH-PARAMS.PEM providing diffie-hellman parameters to use
          for the TLS server.  If the file is missing, QEMU will
          generate a set of DH parameters at startup.  This is a
          computationally expensive operation that consumes random pool
          entropy, so it is recommended that a persistent set of
          parameters be generated upfront and saved.

          For x509 certificate credentials the directory will contain
          further files providing the x509 certificates.  The
          certificates must be stored in PEM format, in filenames
          CA-CERT.PEM, CA-CRL.PEM (optional), SERVER-CERT.PEM (only
          servers), SERVER-KEY.PEM (only servers), CLIENT-CERT.PEM (only
          clients), and CLIENT-KEY.PEM (only clients).

          For the SERVER-KEY.PEM and CLIENT-KEY.PEM files which contain
          sensitive private keys, it is possible to use an encrypted
          version by providing the PASSWORDID parameter.  This provides
          the ID of a previously created ‘secret’ object containing the
          password for decryption.

          The PRIORITY parameter allows to override the global default
          priority used by gnutls.  This can be useful if the system
          administrator needs to use a weaker set of crypto priorities
          for QEMU without potentially forcing the weakness onto all
          applications.  Or conversely if one wants wants a stronger
          default for QEMU than for all other applications, they can do
          this through this parameter.  Its format is a gnutls priority
          string as described at
          <https://gnutls.org/manual/html_node/Priority-Strings.html>.

     ‘-object filter-buffer,id=ID,netdev=NETDEVID,interval=T[,queue=ALL|RX|TX][,status=ON|OFF]’

          Interval T can’t be 0, this filter batches the packet
          delivery: all packets arriving in a given interval on netdev
          NETDEVID are delayed until the end of the interval.  Interval
          is in microseconds.  ‘status’ is optional that indicate
          whether the netfilter is on (enabled) or off (disabled), the
          default status for netfilter will be ’on’.

          queue ALL|RX|TX is an option that can be applied to any
          netfilter.

          ‘all’: the filter is attached both to the receive and the
          transmit queue of the netdev (default).

          ‘rx’: the filter is attached to the receive queue of the
          netdev, where it will receive packets sent to the netdev.

          ‘tx’: the filter is attached to the transmit queue of the
          netdev, where it will receive packets sent by the netdev.

     ‘-object filter-mirror,id=ID,netdev=NETDEVID,outdev=CHARDEVID,queue=ALL|RX|TX[,vnet_hdr_support]’

          filter-mirror on netdev NETDEVID,mirror net packet to
          chardevCHARDEVID, if it has the vnet_hdr_support flag,
          filter-mirror will mirror packet with vnet_hdr_len.

     ‘-object filter-redirector,id=ID,netdev=NETDEVID,indev=CHARDEVID,outdev=CHARDEVID,queue=ALL|RX|TX[,vnet_hdr_support]’

          filter-redirector on netdev NETDEVID,redirect filter’s net
          packet to chardev CHARDEVID,and redirect indev’s packet to
          filter.if it has the vnet_hdr_support flag, filter-redirector
          will redirect packet with vnet_hdr_len.  Create a
          filter-redirector we need to differ outdev id from indev id,
          id can not be the same.  we can just use indev or outdev, but
          at least one of indev or outdev need to be specified.

     ‘-object filter-rewriter,id=ID,netdev=NETDEVID,queue=ALL|RX|TX,[vnet_hdr_support]’

          Filter-rewriter is a part of COLO project.It will rewrite tcp
          packet to secondary from primary to keep secondary tcp
          connection,and rewrite tcp packet to primary from secondary
          make tcp packet can be handled by client.if it has the
          vnet_hdr_support flag, we can parse packet with vnet header.

          usage: colo secondary: -object
          filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0 -object
          filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1
          -object filter-rewriter,id=rew0,netdev=hn0,queue=all

     ‘-object filter-dump,id=ID,netdev=DEV[,file=FILENAME][,maxlen=LEN]’

          Dump the network traffic on netdev DEV to the file specified
          by FILENAME.  At most LEN bytes (64k by default) per packet
          are stored.  The file format is libpcap, so it can be analyzed
          with tools such as tcpdump or Wireshark.

     ‘-object colo-compare,id=ID,primary_in=CHARDEVID,secondary_in=CHARDEVID,outdev=CHARDEVID,iothread=ID[,vnet_hdr_support][,notify_dev=ID]’

          Colo-compare gets packet from primary_inCHARDEVID and
          secondary_inCHARDEVID, than compare primary packet with
          secondary packet.  If the packets are same, we will output
          primary packet to outdevCHARDEVID, else we will notify
          colo-frame do checkpoint and send primary packet to
          outdevCHARDEVID.  In order to improve efficiency, we need to
          put the task of comparison in another thread.  If it has the
          vnet_hdr_support flag, colo compare will send/recv packet with
          vnet_hdr_len.  If you want to use Xen COLO, will need the
          notify_dev to notify Xen colo-frame to do checkpoint.

          we must use it with the help of filter-mirror and
          filter-redirector.


               KVM COLO

               primary:
               -netdev tap,id=hn0,vhost=off,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown
               -device e1000,id=e0,netdev=hn0,mac=52:a4:00:12:78:66
               -chardev socket,id=mirror0,host=3.3.3.3,port=9003,server,nowait
               -chardev socket,id=compare1,host=3.3.3.3,port=9004,server,nowait
               -chardev socket,id=compare0,host=3.3.3.3,port=9001,server,nowait
               -chardev socket,id=compare0-0,host=3.3.3.3,port=9001
               -chardev socket,id=compare_out,host=3.3.3.3,port=9005,server,nowait
               -chardev socket,id=compare_out0,host=3.3.3.3,port=9005
               -object iothread,id=iothread1
               -object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0
               -object filter-redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out
               -object filter-redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0
               -object colo-compare,id=comp0,primary_in=compare0-0,secondary_in=compare1,outdev=compare_out0,iothread=iothread1

               secondary:
               -netdev tap,id=hn0,vhost=off,script=/etc/qemu-ifup,down script=/etc/qemu-ifdown
               -device e1000,netdev=hn0,mac=52:a4:00:12:78:66
               -chardev socket,id=red0,host=3.3.3.3,port=9003
               -chardev socket,id=red1,host=3.3.3.3,port=9004
               -object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0
               -object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1


               Xen COLO

               primary:
               -netdev tap,id=hn0,vhost=off,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown
               -device e1000,id=e0,netdev=hn0,mac=52:a4:00:12:78:66
               -chardev socket,id=mirror0,host=3.3.3.3,port=9003,server,nowait
               -chardev socket,id=compare1,host=3.3.3.3,port=9004,server,nowait
               -chardev socket,id=compare0,host=3.3.3.3,port=9001,server,nowait
               -chardev socket,id=compare0-0,host=3.3.3.3,port=9001
               -chardev socket,id=compare_out,host=3.3.3.3,port=9005,server,nowait
               -chardev socket,id=compare_out0,host=3.3.3.3,port=9005
               -chardev socket,id=notify_way,host=3.3.3.3,port=9009,server,nowait
               -object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0
               -object filter-redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out
               -object filter-redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0
               -object iothread,id=iothread1
               -object colo-compare,id=comp0,primary_in=compare0-0,secondary_in=compare1,outdev=compare_out0,notify_dev=nofity_way,iothread=iothread1

               secondary:
               -netdev tap,id=hn0,vhost=off,script=/etc/qemu-ifup,down script=/etc/qemu-ifdown
               -device e1000,netdev=hn0,mac=52:a4:00:12:78:66
               -chardev socket,id=red0,host=3.3.3.3,port=9003
               -chardev socket,id=red1,host=3.3.3.3,port=9004
               -object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0
               -object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1


          If you want to know the detail of above command line, you can
          read the colo-compare git log.

     ‘-object cryptodev-backend-builtin,id=ID[,queues=QUEUES]’

          Creates a cryptodev backend which executes crypto opreation
          from the QEMU cipher APIS. The ID parameter is a unique ID
          that will be used to reference this cryptodev backend from the
          ‘virtio-crypto’ device.  The QUEUES parameter is optional,
          which specify the queue number of cryptodev backend, the
          default of QUEUES is 1.


               # qemu-kvm \
               [...] \
               -object cryptodev-backend-builtin,id=cryptodev0 \
               -device virtio-crypto-pci,id=crypto0,cryptodev=cryptodev0 \
               [...]

     ‘-object cryptodev-vhost-user,id=ID,chardev=CHARDEVID[,queues=QUEUES]’

          Creates a vhost-user cryptodev backend, backed by a chardev
          CHARDEVID.  The ID parameter is a unique ID that will be used
          to reference this cryptodev backend from the ‘virtio-crypto’
          device.  The chardev should be a unix domain socket backed
          one.  The vhost-user uses a specifically defined protocol to
          pass vhost ioctl replacement messages to an application on the
          other end of the socket.  The QUEUES parameter is optional,
          which specify the queue number of cryptodev backend for
          multiqueue vhost-user, the default of QUEUES is 1.


               # qemu-kvm \
               [...] \
               -chardev socket,id=chardev0,path=/path/to/socket \
               -object cryptodev-vhost-user,id=cryptodev0,chardev=chardev0 \
               -device virtio-crypto-pci,id=crypto0,cryptodev=cryptodev0 \
               [...]

     ‘-object secret,id=ID,data=STRING,format=RAW|BASE64[,keyid=SECRETID,iv=STRING]’
     ‘-object secret,id=ID,file=FILENAME,format=RAW|BASE64[,keyid=SECRETID,iv=STRING]’

          Defines a secret to store a password, encryption key, or some
          other sensitive data.  The sensitive data can either be passed
          directly via the DATA parameter, or indirectly via the FILE
          parameter.  Using the DATA parameter is insecure unless the
          sensitive data is encrypted.

          The sensitive data can be provided in raw format (the
          default), or base64.  When encoded as JSON, the raw format
          only supports valid UTF-8 characters, so base64 is recommended
          for sending binary data.  QEMU will convert from which ever
          format is provided to the format it needs internally.  eg, an
          RBD password can be provided in raw format, even though it
          will be base64 encoded when passed onto the RBD sever.

          For added protection, it is possible to encrypt the data
          associated with a secret using the AES-256-CBC cipher.  Use of
          encryption is indicated by providing the KEYID and IV
          parameters.  The KEYID parameter provides the ID of a
          previously defined secret that contains the AES-256 decryption
          key.  This key should be 32-bytes long and be base64 encoded.
          The IV parameter provides the random initialization vector
          used for encryption of this particular secret and should be a
          base64 encrypted string of the 16-byte IV.

          The simplest (insecure) usage is to provide the secret inline


               # qemu-kvm -object secret,id=sec0,data=letmein,format=raw


          The simplest secure usage is to provide the secret via a file

          # printf "letmein" > mypasswd.txt # qemu-kvm -object
          secret,id=sec0,file=mypasswd.txt,format=raw

          For greater security, AES-256-CBC should be used.  To
          illustrate usage, consider the openssl command line tool which
          can encrypt the data.  Note that when encrypting, the
          plaintext must be padded to the cipher block size (32 bytes)
          using the standard PKCS#5/6 compatible padding algorithm.

          First a master key needs to be created in base64 encoding:

               # openssl rand -base64 32 > key.b64
               # KEY=$(base64 -d key.b64 | hexdump  -v -e '/1 "%02X"')

          Each secret to be encrypted needs to have a random
          initialization vector generated.  These do not need to be kept
          secret

               # openssl rand -base64 16 > iv.b64
               # IV=$(base64 -d iv.b64 | hexdump  -v -e '/1 "%02X"')

          The secret to be defined can now be encrypted, in this case
          we’re telling openssl to base64 encode the result, but it
          could be left as raw bytes if desired.

               # SECRET=$(printf "letmein" |
               openssl enc -aes-256-cbc -a -K $KEY -iv $IV)

          When launching QEMU, create a master secret pointing to
          ‘key.b64’ and specify that to be used to decrypt the user
          password.  Pass the contents of ‘iv.b64’ to the second secret

               # qemu-kvm \
               -object secret,id=secmaster0,format=base64,file=key.b64 \
               -object secret,id=sec0,keyid=secmaster0,format=base64,\
               data=$SECRET,iv=$(<iv.b64)

     ‘-object sev-guest,id=ID,cbitpos=CBITPOS,reduced-phys-bits=VAL,[sev-device=STRING,policy=POLICY,handle=HANDLE,dh-cert-file=FILE,session-file=FILE]’

          Create a Secure Encrypted Virtualization (SEV) guest object,
          which can be used to provide the guest memory encryption
          support on AMD processors.

          When memory encryption is enabled, one of the physical address
          bit (aka the C-bit) is utilized to mark if a memory page is
          protected.  The ‘cbitpos’ is used to provide the C-bit
          position.  The C-bit position is Host family dependent hence
          user must provide this value.  On EPYC, the value should be
          47.

          When memory encryption is enabled, we loose certain bits in
          physical address space.  The ‘reduced-phys-bits’ is used to
          provide the number of bits we loose in physical address space.
          Similar to C-bit, the value is Host family dependent.  On
          EPYC, the value should be 5.

          The ‘sev-device’ provides the device file to use for
          communicating with the SEV firmware running inside AMD Secure
          Processor.  The default device is ’/dev/sev’.  If hardware
          supports memory encryption then /dev/sev devices are created
          by CCP driver.

          The ‘policy’ provides the guest policy to be enforced by the
          SEV firmware and restrict what configuration and operational
          commands can be performed on this guest by the hypervisor.
          The policy should be provided by the guest owner and is bound
          to the guest and cannot be changed throughout the lifetime of
          the guest.  The default is 0.

          If guest ‘policy’ allows sharing the key with another SEV
          guest then ‘handle’ can be use to provide handle of the guest
          from which to share the key.

          The ‘dh-cert-file’ and ‘session-file’ provides the guest
          owner’s Public Diffie-Hillman key defined in SEV spec.  The
          PDH and session parameters are used for establishing a
          cryptographic session with the guest owner to negotiate keys
          used for attestation.  The file must be encoded in base64.

          e.g to launch a SEV guest
               # qemu-kvm \
               ......
               -object sev-guest,id=sev0,cbitpos=47,reduced-phys-bits=5 \
               -machine ...,memory-encryption=sev0
               .....


     ‘-object authz-simple,id=ID,identity=STRING’

          Create an authorization object that will control access to
          network services.

          The ‘identity’ parameter is identifies the user and its format
          depends on the network service that authorization object is
          associated with.  For authorizing based on TLS x509
          certificates, the identity must be the x509 distinguished
          name.  Note that care must be taken to escape any commas in
          the distinguished name.

          An example authorization object to validate a x509
          distinguished name would look like:
               # qemu-kvm \
               ...
               -object 'authz-simple,id=auth0,identity=CN=laptop.example.com,,O=Example Org,,L=London,,ST=London,,C=GB' \
               ...

          Note the use of quotes due to the x509 distinguished name
          containing whitespace, and escaping of ’,’.

     ‘-object authz-listfile,id=ID,filename=PATH,refresh=YES|NO’

          Create an authorization object that will control access to
          network services.

          The ‘filename’ parameter is the fully qualified path to a file
          containing the access control list rules in JSON format.

          An example set of rules that match against SASL usernames
          might look like:

               {
               "rules": [
               { "match": "fred", "policy": "allow", "format": "exact" },
               { "match": "bob", "policy": "allow", "format": "exact" },
               { "match": "danb", "policy": "deny", "format": "glob" },
               { "match": "dan*", "policy": "allow", "format": "exact" },
               ],
               "policy": "deny"
               }

          When checking access the object will iterate over all the
          rules and the first rule to match will have its ‘policy’ value
          returned as the result.  If no rules match, then the default
          ‘policy’ value is returned.

          The rules can either be an exact string match, or they can use
          the simple UNIX glob pattern matching to allow wildcards to be
          used.

          If ‘refresh’ is set to true the file will be monitored and
          automatically reloaded whenever its content changes.

          As with the ‘authz-simple’ object, the format of the identity
          strings being matched depends on the network service, but is
          usually a TLS x509 distinguished name, or a SASL username.

          An example authorization object to validate a SASL username
          would look like:
               # qemu-kvm \
               ...
               -object authz-simple,id=auth0,filename=/etc/qemu/vnc-sasl.acl,refresh=yes
               ...

     ‘-object authz-pam,id=ID,service=STRING’

          Create an authorization object that will control access to
          network services.

          The ‘service’ parameter provides the name of a PAM service to
          use for authorization.  It requires that a file
          ‘/etc/pam.d/SERVICE’ exist to provide the configuration for
          the ‘account’ subsystem.

          An example authorization object to validate a TLS x509
          distinguished name would look like:

               # qemu-kvm \
               ...
               -object authz-pam,id=auth0,service=qemu-vnc
               ...

          There would then be a corresponding config file for PAM at
          ‘/etc/pam.d/qemu-vnc’ that contains:

               account requisite  pam_listfile.so item=user sense=allow \
               file=/etc/qemu/vnc.allow

          Finally the ‘/etc/qemu/vnc.allow’ file would contain the list
          of x509 distingished names that are permitted access

               CN=laptop.example.com,O=Example Home,L=London,ST=London,C=GB

2.3.13 Device URL Syntax
------------------------

In addition to using normal file images for the emulated storage
devices, QEMU can also use networked resources such as iSCSI devices.
These are specified using a special URL syntax.

‘iSCSI’
     iSCSI support allows QEMU to access iSCSI resources directly and
     use as images for the guest storage.  Both disk and cdrom images
     are supported.

     Syntax for specifying iSCSI LUNs is
     “iscsi://<target-ip>[:<port>]/<target-iqn>/<lun>”

     By default qemu will use the iSCSI initiator-name
     ’iqn.2008-11.org.linux-kvm[:<name>]’ but this can also be set from
     the command line or a configuration file.

     Since version Qemu 2.4 it is possible to specify a iSCSI request
     timeout to detect stalled requests and force a reestablishment of
     the session.  The timeout is specified in seconds.  The default is
     0 which means no timeout.  Libiscsi 1.15.0 or greater is required
     for this feature.

     Example (without authentication):
          qemu-kvm -iscsi initiator-name=iqn.2001-04.com.example:my-initiator \
                           -cdrom iscsi://192.0.2.1/iqn.2001-04.com.example/2 \
                           -drive file=iscsi://192.0.2.1/iqn.2001-04.com.example/1

     Example (CHAP username/password via URL):
          qemu-kvm -drive file=iscsi://user%password@192.0.2.1/iqn.2001-04.com.example/1

     Example (CHAP username/password via environment variables):
          LIBISCSI_CHAP_USERNAME="user" \
          LIBISCSI_CHAP_PASSWORD="password" \
          qemu-kvm -drive file=iscsi://192.0.2.1/iqn.2001-04.com.example/1

‘NBD’
     QEMU supports NBD (Network Block Devices) both using TCP protocol
     as well as Unix Domain Sockets.  With TCP, the default port is
     10809.

     Syntax for specifying a NBD device using TCP, in preferred URI
     form: “nbd://<server-ip>[:<port>]/[<export>]”

     Syntax for specifying a NBD device using Unix Domain Sockets;
     remember that ’?’ is a shell glob character and may need quoting:
     “nbd+unix:///[<export>]?socket=<domain-socket>”

     Older syntax that is also recognized:
     “nbd:<server-ip>:<port>[:exportname=<export>]”

     Syntax for specifying a NBD device using Unix Domain Sockets
     “nbd:unix:<domain-socket>[:exportname=<export>]”

     Example for TCP
          qemu-kvm --drive file=nbd:192.0.2.1:30000

     Example for Unix Domain Sockets
          qemu-kvm --drive file=nbd:unix:/tmp/nbd-socket

‘SSH’
     QEMU supports SSH (Secure Shell) access to remote disks.

     Examples:
          qemu-kvm -drive file=ssh://user@host/path/to/disk.img
          qemu-kvm -drive file.driver=ssh,file.user=user,file.host=host,file.port=22,file.path=/path/to/disk.img

     Currently authentication must be done using ssh-agent.  Other
     authentication methods may be supported in future.

‘Sheepdog’
     Sheepdog is a distributed storage system for QEMU. QEMU supports
     using either local sheepdog devices or remote networked devices.

     Syntax for specifying a sheepdog device
          sheepdog[+tcp|+unix]://[host:port]/vdiname[?socket=path][#snapid|#tag]

     Example
          qemu-kvm --drive file=sheepdog://192.0.2.1:30000/MyVirtualMachine

     See also <https://sheepdog.github.io/sheepdog/>.

‘GlusterFS’
     GlusterFS is a user space distributed file system.  QEMU supports
     the use of GlusterFS volumes for hosting VM disk images using TCP,
     Unix Domain Sockets and RDMA transport protocols.

     Syntax for specifying a VM disk image on GlusterFS volume is

          URI:
          gluster[+type]://[host[:port]]/volume/path[?socket=...][,debug=N][,logfile=...]

          JSON:
          'json:{"driver":"qcow2","file":{"driver":"gluster","volume":"testvol","path":"a.img","debug":N,"logfile":"...",
                                           "server":[{"type":"tcp","host":"...","port":"..."},
                                                     {"type":"unix","socket":"..."}]}}'

     Example
          URI:
          qemu-kvm --drive file=gluster://192.0.2.1/testvol/a.img,
                                         file.debug=9,file.logfile=/var/log/qemu-gluster.log

          JSON:
          qemu-kvm 'json:{"driver":"qcow2",
                                    "file":{"driver":"gluster",
                                             "volume":"testvol","path":"a.img",
                                             "debug":9,"logfile":"/var/log/qemu-gluster.log",
                                             "server":[{"type":"tcp","host":"1.2.3.4","port":24007},
                                                       {"type":"unix","socket":"/var/run/glusterd.socket"}]}}'
          qemu-kvm -drive driver=qcow2,file.driver=gluster,file.volume=testvol,file.path=/path/a.img,
                                                file.debug=9,file.logfile=/var/log/qemu-gluster.log,
                                                file.server.0.type=tcp,file.server.0.host=1.2.3.4,file.server.0.port=24007,
                                                file.server.1.type=unix,file.server.1.socket=/var/run/glusterd.socket

     See also <http://www.gluster.org>.

‘HTTP/HTTPS/FTP/FTPS’
     QEMU supports read-only access to files accessed over http(s) and
     ftp(s).

     Syntax using a single filename:
          <protocol>://[<username>[:<password>]@]<host>/<path>

     where:
     ‘protocol’
          ’http’, ’https’, ’ftp’, or ’ftps’.

     ‘username’
          Optional username for authentication to the remote server.

     ‘password’
          Optional password for authentication to the remote server.

     ‘host’
          Address of the remote server.

     ‘path’
          Path on the remote server, including any query string.

     The following options are also supported:
     ‘url’
          The full URL when passing options to the driver explicitly.

     ‘readahead’
          The amount of data to read ahead with each range request to
          the remote server.  This value may optionally have the suffix
          ’T’, ’G’, ’M’, ’K’, ’k’ or ’b’.  If it does not have a suffix,
          it will be assumed to be in bytes.  The value must be a
          multiple of 512 bytes.  It defaults to 256k.

     ‘sslverify’
          Whether to verify the remote server’s certificate when
          connecting over SSL. It can have the value ’on’ or ’off’.  It
          defaults to ’on’.

     ‘cookie’
          Send this cookie (it can also be a list of cookies separated
          by ’;’) with each outgoing request.  Only supported when using
          protocols such as HTTP which support cookies, otherwise
          ignored.

     ‘timeout’
          Set the timeout in seconds of the CURL connection.  This
          timeout is the time that CURL waits for a response from the
          remote server to get the size of the image to be downloaded.
          If not set, the default timeout of 5 seconds is used.

     Note that when passing options to qemu explicitly, ‘driver’ is the
     value of <protocol>.

     Example: boot from a remote Fedora 20 live ISO image
          qemu-kvm --drive media=cdrom,file=https://archives.fedoraproject.org/pub/archive/fedora/linux/releases/20/Live/x86_64/Fedora-Live-Desktop-x86_64-20-1.iso,readonly

          qemu-kvm --drive media=cdrom,file.driver=http,file.url=http://archives.fedoraproject.org/pub/fedora/linux/releases/20/Live/x86_64/Fedora-Live-Desktop-x86_64-20-1.iso,readonly

     Example: boot from a remote Fedora 20 cloud image using a local
     overlay for writes, copy-on-read, and a readahead of 64k
          qemu-img create -f qcow2 -o backing_file='json:{"file.driver":"http",, "file.url":"http://archives.fedoraproject.org/pub/archive/fedora/linux/releases/20/Images/x86_64/Fedora-x86_64-20-20131211.1-sda.qcow2",, "file.readahead":"64k"}' /tmp/Fedora-x86_64-20-20131211.1-sda.qcow2

          qemu-kvm -drive file=/tmp/Fedora-x86_64-20-20131211.1-sda.qcow2,copy-on-read=on

     Example: boot from an image stored on a VMware vSphere server with
     a self-signed certificate using a local overlay for writes, a
     readahead of 64k and a timeout of 10 seconds.
          qemu-img create -f qcow2 -o backing_file='json:{"file.driver":"https",, "file.url":"https://user:password@vsphere.example.com/folder/test/test-flat.vmdk?dcPath=Datacenter&dsName=datastore1",, "file.sslverify":"off",, "file.readahead":"64k",, "file.timeout":10}' /tmp/test.qcow2

          qemu-kvm -drive file=/tmp/test.qcow2

2.4 Keys in the graphical frontends
===================================

During the graphical emulation, you can use special key combinations to
change modes.  The default key mappings are shown below, but if you use
‘-alt-grab’ then the modifier is Ctrl-Alt-Shift (instead of Ctrl-Alt)
and if you use ‘-ctrl-grab’ then the modifier is the right Ctrl key
(instead of Ctrl-Alt):

<Ctrl-Alt-f>
     Toggle full screen

<Ctrl-Alt-+>
     Enlarge the screen

<Ctrl-Alt-->
     Shrink the screen

<Ctrl-Alt-u>
     Restore the screen’s un-scaled dimensions

<Ctrl-Alt-n>
     Switch to virtual console ’n’.  Standard console mappings are:
     _1_
          Target system display
     _2_
          Monitor
     _3_
          Serial port

<Ctrl-Alt>
     Toggle mouse and keyboard grab.

In the virtual consoles, you can use <Ctrl-Up>, <Ctrl-Down>,
<Ctrl-PageUp> and <Ctrl-PageDown> to move in the back log.

2.5 Keys in the character backend multiplexer
=============================================

During emulation, if you are using a character backend multiplexer
(which is the default if you are using ‘-nographic’) then several
commands are available via an escape sequence.  These key sequences all
start with an escape character, which is <Ctrl-a> by default, but can be
changed with ‘-echr’.  The list below assumes you’re using the default.

<Ctrl-a h>
     Print this help
<Ctrl-a x>
     Exit emulator
<Ctrl-a s>
     Save disk data back to file (if -snapshot)
<Ctrl-a t>
     Toggle console timestamps
<Ctrl-a b>
     Send break (magic sysrq in Linux)
<Ctrl-a c>
     Rotate between the frontends connected to the multiplexer (usually
     this switches between the monitor and the console)
<Ctrl-a Ctrl-a>
     Send the escape character to the frontend

2.6 QEMU Monitor
================

The QEMU monitor is used to give complex commands to the QEMU emulator.
You can use it to:

   − Remove or insert removable media images (such as CD-ROM or
     floppies).

   − Freeze/unfreeze the Virtual Machine (VM) and save or restore its
     state from a disk file.

   − Inspect the VM state without an external debugger.

2.6.1 Commands
--------------

The following commands are available:

‘help or ? [CMD]’
     Show the help for all commands or just for command CMD.
‘commit’
     Commit changes to the disk images (if -snapshot is used) or backing
     files.  If the backing file is smaller than the snapshot, then the
     backing file will be resized to be the same size as the snapshot.
     If the snapshot is smaller than the backing file, the backing file
     will not be truncated.  If you want the backing file to match the
     size of the smaller snapshot, you can safely truncate it yourself
     once the commit operation successfully completes.
‘q or quit’
     Quit the emulator.
‘exit_preconfig’
     This command makes QEMU exit the preconfig state and proceed with
     VM initialization using configuration data provided on the command
     line and via the QMP monitor during the preconfig state.  The
     command is only available during the preconfig state (i.e.  when
     the –preconfig command line option was in use).
‘block_resize’
     Resize a block image while a guest is running.  Usually requires
     guest action to see the updated size.  Resize to a lower size is
     supported, but should be used with extreme caution.  Note that this
     command only resizes image files, it can not resize block devices
     like LVM volumes.
‘block_stream’
     Copy data from a backing file into a block device.
‘block_job_set_speed’
     Set maximum speed for a background block operation.
‘block_job_cancel’
     Stop an active background block operation (streaming, mirroring).
‘block_job_complete’
     Manually trigger completion of an active background block
     operation.  For mirroring, this will switch the device to the
     destination path.
‘block_job_pause’
     Pause an active block streaming operation.
‘block_job_resume’
     Resume a paused block streaming operation.
‘eject [-f] DEVICE’
     Eject a removable medium (use -f to force it).
‘drive_del DEVICE’
     Remove host block device.  The result is that guest generated IO is
     no longer submitted against the host device underlying the disk.
     Once a drive has been deleted, the QEMU Block layer returns -EIO
     which results in IO errors in the guest for applications that are
     reading/writing to the device.  These errors are always reported to
     the guest, regardless of the drive’s error actions (drive options
     rerror, werror).
‘change DEVICE SETTING’
     Change the configuration of a device.

     ‘change DISKDEVICE FILENAME [FORMAT [READ-ONLY-MODE]]’
          Change the medium for a removable disk device to point to
          FILENAME.  eg

               (qemu) change ide1-cd0 /path/to/some.iso

          FORMAT is optional.

          READ-ONLY-MODE may be used to change the read-only status of
          the device.  It accepts the following values:

          RETAIN
               Retains the current status; this is the default.

          READ-ONLY
               Makes the device read-only.

          READ-WRITE
               Makes the device writable.

     ‘change vnc DISPLAY,OPTIONS’
          Change the configuration of the VNC server.  The valid syntax
          for DISPLAY and OPTIONS are described at *note
          sec_invocation::.  eg

               (qemu) change vnc localhost:1

     ‘change vnc password [PASSWORD]’

          Change the password associated with the VNC server.  If the
          new password is not supplied, the monitor will prompt for it
          to be entered.  VNC passwords are only significant up to 8
          letters.  eg

               (qemu) change vnc password
               Password: ********

‘screendump FILENAME’
     Save screen into PPM image FILENAME.
‘logfile FILENAME’
     Output logs to FILENAME.
‘trace-event’
     changes status of a trace event
‘trace-file on|off|flush’
     Open, close, or flush the trace file.  If no argument is given, the
     status of the trace file is displayed.
‘log ITEM1[,...]’
     Activate logging of the specified items.
‘savevm TAG’
     Create a snapshot of the whole virtual machine.  If TAG is
     provided, it is used as human readable identifier.  If there is
     already a snapshot with the same tag, it is replaced.  More info at
     *note vm_snapshots::.

     Since 4.0, savevm stopped allowing the snapshot id to be set,
     accepting only TAG as parameter.
‘loadvm TAG’
     Set the whole virtual machine to the snapshot identified by the tag
     TAG.

     Since 4.0, loadvm stopped accepting snapshot id as parameter.
‘delvm TAG’
     Delete the snapshot identified by TAG.

     Since 4.0, delvm stopped deleting snapshots by snapshot id,
     accepting only TAG as parameter.
‘singlestep [off]’
     Run the emulation in single step mode.  If called with option off,
     the emulation returns to normal mode.
‘stop’
     Stop emulation.
‘c or cont’
     Resume emulation.
‘system_wakeup’
     Wakeup guest from suspend.
‘gdbserver [PORT]’
     Start gdbserver session (default PORT=1234)
‘x/fmt ADDR’
     Virtual memory dump starting at ADDR.
‘xp /FMT ADDR’
     Physical memory dump starting at ADDR.

     FMT is a format which tells the command how to format the data.
     Its syntax is: ‘/{count}{format}{size}’

     COUNT
          is the number of items to be dumped.

     FORMAT
          can be x (hex), d (signed decimal), u (unsigned decimal), o
          (octal), c (char) or i (asm instruction).

     SIZE
          can be b (8 bits), h (16 bits), w (32 bits) or g (64 bits).
          On x86, ‘h’ or ‘w’ can be specified with the ‘i’ format to
          respectively select 16 or 32 bit code instruction size.

     Examples:
        • Dump 10 instructions at the current instruction pointer:
               (qemu) x/10i $eip
               0x90107063:  ret
               0x90107064:  sti
               0x90107065:  lea    0x0(%esi,1),%esi
               0x90107069:  lea    0x0(%edi,1),%edi
               0x90107070:  ret
               0x90107071:  jmp    0x90107080
               0x90107073:  nop
               0x90107074:  nop
               0x90107075:  nop
               0x90107076:  nop

        • Dump 80 16 bit values at the start of the video memory.
               (qemu) xp/80hx 0xb8000
               0x000b8000: 0x0b50 0x0b6c 0x0b65 0x0b78 0x0b38 0x0b36 0x0b2f 0x0b42
               0x000b8010: 0x0b6f 0x0b63 0x0b68 0x0b73 0x0b20 0x0b56 0x0b47 0x0b41
               0x000b8020: 0x0b42 0x0b69 0x0b6f 0x0b73 0x0b20 0x0b63 0x0b75 0x0b72
               0x000b8030: 0x0b72 0x0b65 0x0b6e 0x0b74 0x0b2d 0x0b63 0x0b76 0x0b73
               0x000b8040: 0x0b20 0x0b30 0x0b35 0x0b20 0x0b4e 0x0b6f 0x0b76 0x0b20
               0x000b8050: 0x0b32 0x0b30 0x0b30 0x0b33 0x0720 0x0720 0x0720 0x0720
               0x000b8060: 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720
               0x000b8070: 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720
               0x000b8080: 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720
               0x000b8090: 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720
‘gpa2hva ADDR’
     Print the host virtual address at which the guest’s physical
     address ADDR is mapped.
‘gpa2hpa ADDR’
     Print the host physical address at which the guest’s physical
     address ADDR is mapped.
‘gva2gpa ADDR’
     Print the guest physical address at which the guest’s virtual
     address ADDR is mapped based on the mapping for the current CPU.
‘p or print/FMT EXPR’
     Print expression value.  Only the FORMAT part of FMT is used.
‘i/FMT ADDR [.INDEX]’
     Read I/O port.
‘o/FMT ADDR VAL’
     Write to I/O port.
‘sendkey KEYS’
     Send KEYS to the guest.  KEYS could be the name of the key or the
     raw value in hexadecimal format.  Use ‘-’ to press several keys
     simultaneously.  Example:
          sendkey ctrl-alt-f1

     This command is useful to send keys that your graphical user
     interface intercepts at low level, such as ‘ctrl-alt-f1’ in X
     Window.
‘sync-profile [on|off|reset]’
     Enable, disable or reset synchronization profiling.  With no
     arguments, prints whether profiling is on or off.
‘system_reset’
     Reset the system.
‘system_powerdown’
     Power down the system (if supported).
‘sum ADDR SIZE’
     Compute the checksum of a memory region.
‘device_add CONFIG’
     Add device.
‘device_del ID’
     Remove device ID.  ID may be a short ID or a QOM object path.
‘cpu INDEX’
     Set the default CPU.
‘mouse_move DX DY [DZ]’
     Move the active mouse to the specified coordinates DX DY with
     optional scroll axis DZ.
‘mouse_button VAL’
     Change the active mouse button state VAL (1=L, 2=M, 4=R).
‘mouse_set INDEX’
     Set which mouse device receives events at given INDEX, index can be
     obtained with
          info mice
‘wavcapture FILENAME AUDIODEV [FREQUENCY [BITS [CHANNELS]]]’
     Capture audio into FILENAME from AUDIODEV, using sample rate
     FREQUENCY bits per sample BITS and number of channels CHANNELS.

     Defaults:
        − Sample rate = 44100 Hz - CD quality
        − Bits = 16
        − Number of channels = 2 - Stereo
‘stopcapture INDEX’
     Stop capture with a given INDEX, index can be obtained with
          info capture
‘memsave ADDR SIZE FILE’
     save to disk virtual memory dump starting at ADDR of size SIZE.
‘pmemsave ADDR SIZE FILE’
     save to disk physical memory dump starting at ADDR of size SIZE.
‘boot_set BOOTDEVICELIST’
     Define new values for the boot device list.  Those values will
     override the values specified on the command line through the
     ‘-boot’ option.

     The values that can be specified here depend on the machine type,
     but are the same that can be specified in the ‘-boot’ command line
     option.
‘nmi CPU’
     Inject an NMI on the default CPU (x86/s390) or all CPUs (ppc64).

‘ringbuf_write DEVICE DATA’
     Write DATA to ring buffer character device DEVICE.  DATA must be a
     UTF-8 string.

‘ringbuf_read DEVICE’
     Read and print up to SIZE bytes from ring buffer character device
     DEVICE.  Certain non-printable characters are printed \uXXXX, where
     XXXX is the character code in hexadecimal.  Character \ is printed
     \\.  Bug: can screw up when the buffer contains invalid UTF-8
     sequences, NUL characters, after the ring buffer lost data, and
     when reading stops because the size limit is reached.

‘announce_self’
     Trigger a round of GARP/RARP broadcasts; this is useful for
     explicitly updating the network infrastructure after a
     reconfiguration or some forms of migration.  The timings of the
     round are set by the migration announce parameters.  An optional
     comma separated INTERFACES list restricts the announce to the named
     set of interfaces.  An optional ID can be used to start a separate
     announce timer and to change the parameters of it later.
‘migrate [-d] [-b] [-i] URI’
     Migrate to URI (using -d to not wait for completion).  -b for
     migration with full copy of disk -i for migration with incremental
     copy of disk (base image is shared)
‘migrate_cancel’
     Cancel the current VM migration.
‘migrate_continue STATE’
     Continue migration from the paused state STATE
‘migrate_incoming URI’
     Continue an incoming migration using the URI (that has the same
     syntax as the -incoming option).
‘migrate_recover URI’
     Continue a paused incoming postcopy migration using the URI.
‘migrate_pause’
     Pause an ongoing migration.  Currently it only supports postcopy.
‘migrate_set_cache_size VALUE’
     Set cache size to VALUE (in bytes) for xbzrle migrations.
‘migrate_set_speed VALUE’
     Set maximum speed to VALUE (in bytes) for migrations.
‘migrate_set_downtime SECOND’
     Set maximum tolerated downtime (in seconds) for migration.
‘migrate_set_capability CAPABILITY STATE’
     Enable/Disable the usage of a capability CAPABILITY for migration.
‘migrate_set_parameter PARAMETER VALUE’
     Set the parameter PARAMETER for migration.
‘migrate_start_postcopy’
     Switch in-progress migration to postcopy mode.  Ignored after the
     end of migration (or once already in postcopy).
‘x_colo_lost_heartbeat’
     Tell COLO that heartbeat is lost, a failover or takeover is needed.
‘client_migrate_info PROTOCOL HOSTNAME PORT TLS-PORT CERT-SUBJECT’
     Set migration information for remote display.  This makes the
     server ask the client to automatically reconnect using the new
     parameters once migration finished successfully.  Only implemented
     for SPICE.
‘dump-guest-memory [-p] FILENAME BEGIN LENGTH’
‘dump-guest-memory [-z|-l|-s|-w] FILENAME’
     Dump guest memory to PROTOCOL.  The file can be processed with
     crash or gdb.  Without -z|-l|-s|-w, the dump format is ELF. -p: do
     paging to get guest’s memory mapping.  -z: dump in kdump-compressed
     format, with zlib compression.  -l: dump in kdump-compressed
     format, with lzo compression.  -s: dump in kdump-compressed format,
     with snappy compression.  -w: dump in Windows crashdump format (can
     be used instead of ELF-dump converting), for Windows x64 guests
     with vmcoreinfo driver only filename: dump file name.  begin: the
     starting physical address.  It’s optional, and should be specified
     together with length.  length: the memory size, in bytes.  It’s
     optional, and should be specified together with begin.
‘dump-skeys FILENAME’
     Save guest storage keys to a file.
‘migration_mode MODE’
     Enables or disables migration mode.
‘snapshot_blkdev’
     Snapshot device, using snapshot file as target if provided
‘snapshot_blkdev_internal’
     Take an internal snapshot on device if it support
‘snapshot_delete_blkdev_internal’
     Delete an internal snapshot on device if it support
‘drive_mirror’
     Start mirroring a block device’s writes to a new destination, using
     the specified target.
‘drive_backup’
     Start a point-in-time copy of a block device to a specificed
     target.
‘drive_add’
     Add drive to PCI storage controller.
‘pcie_aer_inject_error’
     Inject PCIe AER error
‘netdev_add’
     Add host network device.
‘netdev_del’
     Remove host network device.
‘object_add’
     Create QOM object.
‘object_del’
     Destroy QOM object.
‘hostfwd_add’
     Redirect TCP or UDP connections from host to guest (requires -net
     user).
‘hostfwd_remove’
     Remove host-to-guest TCP or UDP redirection.
‘balloon VALUE’
     Request VM to change its memory allocation to VALUE (in MB).
‘set_link NAME [on|off]’
     Switch link NAME on (i.e.  up) or off (i.e.  down).
‘watchdog_action’
     Change watchdog action.
‘acl_show ACLNAME’
     List all the matching rules in the access control list, and the
     default policy.  There are currently two named access control
     lists, VNC.X509DNAME and VNC.USERNAME matching on the x509 client
     certificate distinguished name, and SASL username respectively.
‘acl_policy ACLNAME allow|deny’
     Set the default access control list policy, used in the event that
     none of the explicit rules match.  The default policy at startup is
     always ‘deny’.
‘acl_add ACLNAME MATCH allow|deny [INDEX]’
     Add a match rule to the access control list, allowing or denying
     access.  The match will normally be an exact username or x509
     distinguished name, but can optionally include wildcard globs.  eg
     ‘*@EXAMPLE.COM’ to allow all users in the ‘EXAMPLE.COM’ kerberos
     realm.  The match will normally be appended to the end of the ACL,
     but can be inserted earlier in the list if the optional INDEX
     parameter is supplied.
‘acl_remove ACLNAME MATCH’
     Remove the specified match rule from the access control list.
‘acl_reset ACLNAME’
     Remove all matches from the access control list, and set the
     default policy back to ‘deny’.
‘nbd_server_start HOST:PORT’
     Start an NBD server on the given host and/or port.  If the ‘-a’
     option is included, all of the virtual machine’s block devices that
     have an inserted media on them are automatically exported; in this
     case, the ‘-w’ option makes the devices writable too.
‘nbd_server_add DEVICE [ NAME ]’
     Export a block device through QEMU’s NBD server, which must be
     started beforehand with ‘nbd_server_start’.  The ‘-w’ option makes
     the exported device writable too.  The export name is controlled by
     NAME, defaulting to DEVICE.
‘nbd_server_remove [-f] NAME’
     Stop exporting a block device through QEMU’s NBD server, which was
     previously started with ‘nbd_server_add’.  The ‘-f’ option forces
     the server to drop the export immediately even if clients are
     connected; otherwise the command fails unless there are no clients.
‘nbd_server_stop’
     Stop the QEMU embedded NBD server.
‘mce CPU BANK STATUS MCGSTATUS ADDR MISC’
     Inject an MCE on the given CPU (x86 only).
‘getfd FDNAME’
     If a file descriptor is passed alongside this command using the
     SCM_RIGHTS mechanism on unix sockets, it is stored using the name
     FDNAME for later use by other monitor commands.
‘closefd FDNAME’
     Close the file descriptor previously assigned to FDNAME using the
     ‘getfd’ command.  This is only needed if the file descriptor was
     never used by another monitor command.
‘block_passwd DEVICE PASSWORD’
     Set the encrypted device DEVICE password to PASSWORD

     This command is now obsolete and will always return an error since
     2.10
‘block_set_io_throttle DEVICE BPS BPS_RD BPS_WR IOPS IOPS_RD IOPS_WR’
     Change I/O throttle limits for a block drive to BPS BPS_RD BPS_WR
     IOPS IOPS_RD IOPS_WR.  DEVICE can be a block device name, a qdev ID
     or a QOM path.
‘set_password [ vnc | spice ] password [ action-if-connected ]’
     Change spice/vnc password.  Use zero to make the password stay
     valid forever.  ACTION-IF-CONNECTED specifies what should happen in
     case a connection is established: FAIL makes the password change
     fail.  DISCONNECT changes the password and disconnects the client.
     KEEP changes the password and keeps the connection up.  KEEP is the
     default.
‘expire_password [ vnc | spice ] expire-time’
     Specify when a password for spice/vnc becomes invalid.  EXPIRE-TIME
     accepts:

     NOW
          Invalidate password instantly.

     NEVER
          Password stays valid forever.

     +NSEC
          Password stays valid for NSEC seconds starting now.

     NSEC
          Password is invalidated at the given time.  NSEC are the
          seconds passed since 1970, i.e.  unix epoch.

‘chardev-add args’
     chardev-add accepts the same parameters as the -chardev command
     line switch.

‘chardev-change args’
     chardev-change accepts existing chardev ID and then the same
     arguments as the -chardev command line switch (except for "id").

‘chardev-remove id’
     Removes the chardev ID.

‘chardev-send-break id’
     Send a break on the chardev ID.

‘qemu-io DEVICE COMMAND’
     Executes a qemu-io command on the given block device.

‘cpu-add ID’
     Add CPU with id ID.  This command is deprecated, please +use
     ‘device_add’ instead.  For details, refer to
     ’docs/cpu-hotplug.rst’.
‘qom-list [PATH]’
     Print QOM properties of object at location PATH
‘qom-set PATH PROPERTY VALUE’
     Set QOM property PROPERTY of object at location PATH to value VALUE

‘info SUBCOMMAND’
     Show various information about the system state.
     ‘info version’
          Show the version of QEMU.
     ‘info network’
          Show the network state.
     ‘info chardev’
          Show the character devices.
     ‘info block’
          Show info of one block device or all block devices.
     ‘info blockstats’
          Show block device statistics.
     ‘info block-jobs’
          Show progress of ongoing block device operations.
     ‘info registers’
          Show the cpu registers.
     ‘info lapic’
          Show local APIC state
     ‘info ioapic’
          Show io APIC state
     ‘info cpus’
          Show infos for each CPU.
     ‘info history’
          Show the command line history.
     ‘info irq’
          Show the interrupts statistics (if available).
     ‘info pic’
          Show PIC state.
     ‘info rdma’
          Show RDMA state.
     ‘info pci’
          Show PCI information.
     ‘info tlb’
          Show virtual to physical memory mappings.
     ‘info mem’
          Show the active virtual memory mappings.
     ‘info mtree’
          Show memory tree.
     ‘info jit’
          Show dynamic compiler info.
     ‘info opcount’
          Show dynamic compiler opcode counters
     ‘info sync-profile [-m|-n] [MAX]’
          Show synchronization profiling info, up to MAX entries
          (default: 10), sorted by total wait time.  -m: sort by mean
          wait time -n: do not coalesce objects with the same call site
          When different objects that share the same call site are
          coalesced, the "Object" field shows—enclosed in brackets—the
          number of objects being coalesced.
     ‘info kvm’
          Show KVM information.
     ‘info numa’
          Show NUMA information.
     ‘info usb’
          Show guest USB devices.
     ‘info usbhost’
          Show host USB devices.
     ‘info profile’
          Show profiling information.
     ‘info capture’
          Show capture information.
     ‘info snapshots’
          Show the currently saved VM snapshots.
     ‘info status’
          Show the current VM status (running|paused).
     ‘info mice’
          Show which guest mouse is receiving events.
     ‘info vnc’
          Show the vnc server status.
     ‘info spice’
          Show the spice server status.
     ‘info name’
          Show the current VM name.
     ‘info uuid’
          Show the current VM UUID.
     ‘info cpustats’
          Show CPU statistics.
     ‘info usernet’
          Show user network stack connection states.
     ‘info migrate’
          Show migration status.
     ‘info migrate_capabilities’
          Show current migration capabilities.
     ‘info migrate_parameters’
          Show current migration parameters.
     ‘info migrate_cache_size’
          Show current migration xbzrle cache size.
     ‘info balloon’
          Show balloon information.
     ‘info qtree’
          Show device tree.
     ‘info qdm’
          Show qdev device model list.
     ‘info qom-tree’
          Show QOM composition tree.
     ‘info roms’
          Show roms.
     ‘info trace-events’
          Show available trace-events & their state.
     ‘info tpm’
          Show the TPM device.
     ‘info memdev’
          Show memory backends
     ‘info memory-devices’
          Show memory devices.
     ‘info iothreads’
          Show iothread’s identifiers.
     ‘info rocker NAME’
          Show rocker switch.
     ‘info rocker-ports NAME-ports’
          Show rocker ports.
     ‘info rocker-of-dpa-flows NAME [TBL_ID]’
          Show rocker OF-DPA flow tables.
     ‘info rocker-of-dpa-groups NAME [TYPE]’
          Show rocker OF-DPA groups.
     ‘info skeys ADDRESS’
          Display the value of a storage key (s390 only)
     ‘info cmma ADDRESS’
          Display the values of the CMMA storage attributes for a range
          of pages (s390 only)
     ‘info dump’
          Display the latest dump status.
     ‘info ramblock’
          Dump all the ramblocks of the system.
     ‘info hotpluggable-cpus’
          Show information about hotpluggable CPUs
     ‘info vm-generation-id’
          Show Virtual Machine Generation ID
     ‘info memory_size_summary’
          Display the amount of initially allocated and present
          hotpluggable (if enabled) memory in bytes.
     ‘info sev’
          Show SEV information.

2.6.2 Integer expressions
-------------------------

The monitor understands integers expressions for every integer argument.
You can use register names to get the value of specifics CPU registers
by prefixing them with _$_.

2.7 CPU models
==============

QEMU / KVM CPU model configuration

QEMU / KVM virtualization supports two ways to configure CPU models

‘Host passthrough’

     This passes the host CPU model features, model, stepping, exactly
     to the guest.  Note that KVM may filter out some host CPU model
     features if they cannot be supported with virtualization.  Live
     migration is unsafe when this mode is used as libvirt / QEMU cannot
     guarantee a stable CPU is exposed to the guest across hosts.  This
     is the recommended CPU to use, provided live migration is not
     required.

‘Named model’

     QEMU comes with a number of predefined named CPU models, that
     typically refer to specific generations of hardware released by
     Intel and AMD. These allow the guest VMs to have a degree of
     isolation from the host CPU, allowing greater flexibility in live
     migrating between hosts with differing hardware.

In both cases, it is possible to optionally add or remove individual CPU
features, to alter what is presented to the guest by default.

Libvirt supports a third way to configure CPU models known as "Host
model".  This uses the QEMU "Named model" feature, automatically picking
a CPU model that is similar the host CPU, and then adding extra features
to approximate the host model as closely as possible.  This does not
guarantee the CPU family, stepping, etc will precisely match the host
CPU, as they would with "Host passthrough", but gives much of the
benefit of passthrough, while making live migration safe.

2.7.1 Recommendations for KVM CPU model configuration on x86 hosts
------------------------------------------------------------------

The information that follows provides recommendations for configuring
CPU models on x86 hosts.  The goals are to maximise performance, while
protecting guest OS against various CPU hardware flaws, and optionally
enabling live migration between hosts with heterogeneous CPU models.

2.7.1.1 Preferred CPU models for Intel x86 hosts
................................................

The following CPU models are preferred for use on Intel hosts.
Administrators / applications are recommended to use the CPU model that
matches the generation of the host CPUs in use.  In a deployment with a
mixture of host CPU models between machines, if live migration
compatibility is required, use the newest CPU model that is compatible
across all desired hosts.

‘Skylake-Server’
‘Skylake-Server-IBRS’

     Intel Xeon Processor (Skylake, 2016)

‘Skylake-Client’
‘Skylake-Client-IBRS’

     Intel Core Processor (Skylake, 2015)

‘Broadwell’
‘Broadwell-IBRS’
‘Broadwell-noTSX’
‘Broadwell-noTSX-IBRS’

     Intel Core Processor (Broadwell, 2014)

‘Haswell’
‘Haswell-IBRS’
‘Haswell-noTSX’
‘Haswell-noTSX-IBRS’

     Intel Core Processor (Haswell, 2013)

‘IvyBridge’
‘IvyBridge-IBRS’

     Intel Xeon E3-12xx v2 (Ivy Bridge, 2012)

‘SandyBridge’
‘SandyBridge-IBRS’

     Intel Xeon E312xx (Sandy Bridge, 2011)

‘Westmere’
‘Westmere-IBRS’

     Westmere E56xx/L56xx/X56xx (Nehalem-C, 2010)

‘Nehalem’
‘Nehalem-IBRS’

     Intel Core i7 9xx (Nehalem Class Core i7, 2008)

‘Penryn’

     Intel Core 2 Duo P9xxx (Penryn Class Core 2, 2007)

‘Conroe’

     Intel Celeron_4x0 (Conroe/Merom Class Core 2, 2006)

2.7.1.2 Important CPU features for Intel x86 hosts
..................................................

The following are important CPU features that should be used on Intel
x86 hosts, when available in the host CPU. Some of them require explicit
configuration to enable, as they are not included by default in some, or
all, of the named CPU models listed above.  In general all of these
features are included if using "Host passthrough" or "Host model".

‘pcid’

     Recommended to mitigate the cost of the Meltdown (CVE-2017-5754)
     fix

     Included by default in Haswell, Broadwell & Skylake Intel CPU
     models.

     Should be explicitly turned on for Westmere, SandyBridge, and
     IvyBridge Intel CPU models.  Note that some desktop/mobile Westmere
     CPUs cannot support this feature.

‘spec-ctrl’

     Required to enable the Spectre v2 (CVE-2017-5715) fix.

     Included by default in Intel CPU models with -IBRS suffix.

     Must be explicitly turned on for Intel CPU models without -IBRS
     suffix.

     Requires the host CPU microcode to support this feature before it
     can be used for guest CPUs.

‘stibp’

     Required to enable stronger Spectre v2 (CVE-2017-5715) fixes in
     some operating systems.

     Must be explicitly turned on for all Intel CPU models.

     Requires the host CPU microcode to support this feature before it
     can be used for guest CPUs.

‘ssbd’

     Required to enable the CVE-2018-3639 fix

     Not included by default in any Intel CPU model.

     Must be explicitly turned on for all Intel CPU models.

     Requires the host CPU microcode to support this feature before it
     can be used for guest CPUs.

‘pdpe1gb’

     Recommended to allow guest OS to use 1GB size pages

     Not included by default in any Intel CPU model.

     Should be explicitly turned on for all Intel CPU models.

     Note that not all CPU hardware will support this feature.

‘md-clear’

     Required to confirm the MDS (CVE-2018-12126, CVE-2018-12127,
     CVE-2018-12130, CVE-2019-11091) fixes.

     Not included by default in any Intel CPU model.

     Must be explicitly turned on for all Intel CPU models.

     Requires the host CPU microcode to support this feature before it
     can be used for guest CPUs.

2.7.1.3 Preferred CPU models for AMD x86 hosts
..............................................

The following CPU models are preferred for use on Intel hosts.
Administrators / applications are recommended to use the CPU model that
matches the generation of the host CPUs in use.  In a deployment with a
mixture of host CPU models between machines, if live migration
compatibility is required, use the newest CPU model that is compatible
across all desired hosts.

‘EPYC’
‘EPYC-IBPB’

     AMD EPYC Processor (2017)

‘Opteron_G5’

     AMD Opteron 63xx class CPU (2012)

‘Opteron_G4’

     AMD Opteron 62xx class CPU (2011)

‘Opteron_G3’

     AMD Opteron 23xx (Gen 3 Class Opteron, 2009)

‘Opteron_G2’

     AMD Opteron 22xx (Gen 2 Class Opteron, 2006)

‘Opteron_G1’

     AMD Opteron 240 (Gen 1 Class Opteron, 2004)

2.7.1.4 Important CPU features for AMD x86 hosts
................................................

The following are important CPU features that should be used on AMD x86
hosts, when available in the host CPU. Some of them require explicit
configuration to enable, as they are not included by default in some, or
all, of the named CPU models listed above.  In general all of these
features are included if using "Host passthrough" or "Host model".

‘ibpb’

     Required to enable the Spectre v2 (CVE-2017-5715) fix.

     Included by default in AMD CPU models with -IBPB suffix.

     Must be explicitly turned on for AMD CPU models without -IBPB
     suffix.

     Requires the host CPU microcode to support this feature before it
     can be used for guest CPUs.

‘stibp’

     Required to enable stronger Spectre v2 (CVE-2017-5715) fixes in
     some operating systems.

     Must be explicitly turned on for all AMD CPU models.

     Requires the host CPU microcode to support this feature before it
     can be used for guest CPUs.

‘virt-ssbd’

     Required to enable the CVE-2018-3639 fix

     Not included by default in any AMD CPU model.

     Must be explicitly turned on for all AMD CPU models.

     This should be provided to guests, even if amd-ssbd is also
     provided, for maximum guest compatibility.

     Note for some QEMU / libvirt versions, this must be force enabled
     when when using "Host model", because this is a virtual feature
     that doesn’t exist in the physical host CPUs.

‘amd-ssbd’

     Required to enable the CVE-2018-3639 fix

     Not included by default in any AMD CPU model.

     Must be explicitly turned on for all AMD CPU models.

     This provides higher performance than virt-ssbd so should be
     exposed to guests whenever available in the host.  virt-ssbd should
     none the less also be exposed for maximum guest compatibility as
     some kernels only know about virt-ssbd.

‘amd-no-ssb’

     Recommended to indicate the host is not vulnerable CVE-2018-3639

     Not included by default in any AMD CPU model.

     Future hardware generations of CPU will not be vulnerable to
     CVE-2018-3639, and thus the guest should be told not to enable its
     mitigations, by exposing amd-no-ssb.  This is mutually exclusive
     with virt-ssbd and amd-ssbd.

‘pdpe1gb’

     Recommended to allow guest OS to use 1GB size pages

     Not included by default in any AMD CPU model.

     Should be explicitly turned on for all AMD CPU models.

     Note that not all CPU hardware will support this feature.

2.7.1.5 Default x86 CPU models
..............................

The default QEMU CPU models are designed such that they can run on all
hosts.  If an application does not wish to do perform any host
compatibility checks before launching guests, the default is guaranteed
to work.

The default CPU models will, however, leave the guest OS vulnerable to
various CPU hardware flaws, so their use is strongly discouraged.
Applications should follow the earlier guidance to setup a better CPU
configuration, with host passthrough recommended if live migration is
not needed.

‘qemu32’
‘qemu64’

     QEMU Virtual CPU version 2.5+ (32 & 64 bit variants)

     qemu64 is used for x86_64 guests and qemu32 is used for i686
     guests, when no -cpu argument is given to QEMU, or no <cpu> is
     provided in libvirt XML.

2.7.1.6 Other non-recommended x86 CPUs
......................................

The following CPUs models are compatible with most AMD and Intel x86
hosts, but their usage is discouraged, as they expose a very limited
featureset, which prevents guests having optimal performance.

‘kvm32’
‘kvm64’

     Common KVM processor (32 & 64 bit variants)

     Legacy models just for historical compatibility with ancient QEMU
     versions.

‘486’
‘athlon’
‘phenom’
‘coreduo’
‘core2duo’
‘n270’
‘pentium’
‘pentium2’
‘pentium3’

     Various very old x86 CPU models, mostly predating the introduction
     of hardware assisted virtualization, that should thus not be
     required for running virtual machines.

2.7.2 Supported CPU model configurations on MIPS hosts
------------------------------------------------------

QEMU supports variety of MIPS CPU models:

2.7.2.1 Supported CPU models for MIPS32 hosts
.............................................

The following CPU models are supported for use on MIPS32 hosts.
Administrators / applications are recommended to use the CPU model that
matches the generation of the host CPUs in use.  In a deployment with a
mixture of host CPU models between machines, if live migration
compatibility is required, use the newest CPU model that is compatible
across all desired hosts.

‘mips32r6-generic’

     MIPS32 Processor (Release 6, 2015)

‘P5600’

     MIPS32 Processor (P5600, 2014)

‘M14K’
‘M14Kc’

     MIPS32 Processor (M14K, 2009)

‘74Kf’

     MIPS32 Processor (74K, 2007)

‘34Kf’

     MIPS32 Processor (34K, 2006)

‘24Kc’
‘24KEc’
‘24Kf’

     MIPS32 Processor (24K, 2003)

‘4Kc’
‘4Km’
‘4KEcR1’
‘4KEmR1’
‘4KEc’
‘4KEm’

     MIPS32 Processor (4K, 1999)

2.7.2.2 Supported CPU models for MIPS64 hosts
.............................................

The following CPU models are supported for use on MIPS64 hosts.
Administrators / applications are recommended to use the CPU model that
matches the generation of the host CPUs in use.  In a deployment with a
mixture of host CPU models between machines, if live migration
compatibility is required, use the newest CPU model that is compatible
across all desired hosts.

‘I6400’

     MIPS64 Processor (Release 6, 2014)

‘Loongson-2F’

     MIPS64 Processor (Loongson 2, 2008)

‘Loongson-2E’

     MIPS64 Processor (Loongson 2, 2006)

‘mips64dspr2’

     MIPS64 Processor (Release 2, 2006)

‘MIPS64R2-generic’
‘5KEc’
‘5KEf’

     MIPS64 Processor (Release 2, 2002)

‘20Kc’

     MIPS64 Processor (20K, 2000)

‘5Kc’
‘5Kf’

     MIPS64 Processor (5K, 1999)

‘VR5432’

     MIPS64 Processor (VR, 1998)

‘R4000’

     MIPS64 Processor (MIPS III, 1991)

2.7.2.3 Supported CPU models for nanoMIPS hosts
...............................................

The following CPU models are supported for use on nanoMIPS hosts.
Administrators / applications are recommended to use the CPU model that
matches the generation of the host CPUs in use.  In a deployment with a
mixture of host CPU models between machines, if live migration
compatibility is required, use the newest CPU model that is compatible
across all desired hosts.

‘I7200’

     MIPS I7200 (nanoMIPS, 2018)

2.7.2.4 Preferred CPU models for MIPS hosts
...........................................

The following CPU models are preferred for use on different MIPS hosts:

‘MIPS III’
     R4000

‘MIPS32R2’
     34Kf

‘MIPS64R6’
     I6400

‘nanoMIPS’
     I7200

2.7.3 Syntax for configuring CPU models
---------------------------------------

The example below illustrate the approach to configuring the various CPU
models / features in QEMU and libvirt

2.7.3.1 QEMU command line
.........................

‘Host passthrough’

             $ qemu-kvm -cpu host

     With feature customization:

             $ qemu-kvm -cpu host,-vmx,...

‘Named CPU models’

             $ qemu-kvm -cpu Westmere

     With feature customization:

             $ qemu-kvm -cpu Westmere,+pcid,...

2.7.3.2 Libvirt guest XML
.........................

‘Host passthrough’

             <cpu mode='host-passthrough'/>

     With feature customization:

             <cpu mode='host-passthrough'>
                 <feature name="vmx" policy="disable"/>
                 ...
             </cpu>

‘Host model’

             <cpu mode='host-model'/>

     With feature customization:

             <cpu mode='host-model'>
                 <feature name="vmx" policy="disable"/>
                 ...
             </cpu>

‘Named model’

             <cpu mode='custom'>
                 <model name="Westmere"/>
             </cpu>

     With feature customization:

             <cpu mode='custom'>
                 <model name="Westmere"/>
                 <feature name="pcid" policy="require"/>
                 ...
             </cpu>

2.8 Disk Images
===============

QEMU supports many disk image formats, including growable disk images
(their size increase as non empty sectors are written), compressed and
encrypted disk images.

2.8.1 Quick start for disk image creation
-----------------------------------------

You can create a disk image with the command:
     qemu-img create myimage.img mysize
where MYIMAGE.IMG is the disk image filename and MYSIZE is its size in
kilobytes.  You can add an ‘M’ suffix to give the size in megabytes and
a ‘G’ suffix for gigabytes.

See *note qemu_img_invocation:: for more information.

2.8.2 Snapshot mode
-------------------

If you use the option ‘-snapshot’, all disk images are considered as
read only.  When sectors in written, they are written in a temporary
file created in ‘/tmp’.  You can however force the write back to the raw
disk images by using the ‘commit’ monitor command (or <C-a s> in the
serial console).

2.8.3 VM snapshots
------------------

VM snapshots are snapshots of the complete virtual machine including CPU
state, RAM, device state and the content of all the writable disks.  In
order to use VM snapshots, you must have at least one non removable and
writable block device using the ‘qcow2’ disk image format.  Normally
this device is the first virtual hard drive.

Use the monitor command ‘savevm’ to create a new VM snapshot or replace
an existing one.  A human readable name can be assigned to each snapshot
in addition to its numerical ID.

Use ‘loadvm’ to restore a VM snapshot and ‘delvm’ to remove a VM
snapshot.  ‘info snapshots’ lists the available snapshots with their
associated information:

     (qemu) info snapshots
     Snapshot devices: hda
     Snapshot list (from hda):
     ID        TAG                 VM SIZE                DATE       VM CLOCK
     1         start                   41M 2006-08-06 12:38:02   00:00:14.954
     2                                 40M 2006-08-06 12:43:29   00:00:18.633
     3         msys                    40M 2006-08-06 12:44:04   00:00:23.514

A VM snapshot is made of a VM state info (its size is shown in ‘info
snapshots’) and a snapshot of every writable disk image.  The VM state
info is stored in the first ‘qcow2’ non removable and writable block
device.  The disk image snapshots are stored in every disk image.  The
size of a snapshot in a disk image is difficult to evaluate and is not
shown by ‘info snapshots’ because the associated disk sectors are shared
among all the snapshots to save disk space (otherwise each snapshot
would need a full copy of all the disk images).

When using the (unrelated) ‘-snapshot’ option (*note
disk_images_snapshot_mode::), you can always make VM snapshots, but they
are deleted as soon as you exit QEMU.

VM snapshots currently have the following known limitations:
   • They cannot cope with removable devices if they are removed or
     inserted after a snapshot is done.
   • A few device drivers still have incomplete snapshot support so
     their state is not saved or restored properly (in particular USB).

2.8.4 ‘qemu-img’ Invocation
---------------------------

     qemu-img [STANDARD OPTIONS] COMMAND [COMMAND OPTIONS]

qemu-img allows you to create, convert and modify images offline.  It
can handle all image formats supported by QEMU.

Warning: Never use qemu-img to modify images in use by a running virtual
machine or any other process; this may destroy the image.  Also, be
aware that querying an image that is being modified by another process
may encounter inconsistent state.

Standard options:
‘-h, --help’
     Display this help and exit
‘-V, --version’
     Display version information and exit
‘-T, --trace [[enable=]PATTERN][,events=FILE][,file=FILE]’
     Specify tracing options.

     ‘[enable=]PATTERN’
          Immediately enable events matching PATTERN (either event name
          or a globbing pattern).  This option is only available if QEMU
          has been compiled with the SIMPLE, LOG or FTRACE tracing
          backend.  To specify multiple events or patterns, specify the
          ‘-trace’ option multiple times.

          Use ‘-trace help’ to print a list of names of trace points.

     ‘events=FILE’
          Immediately enable events listed in FILE.  The file must
          contain one event name (as listed in the ‘trace-events-all’
          file) per line; globbing patterns are accepted too.  This
          option is only available if QEMU has been compiled with the
          SIMPLE, LOG or FTRACE tracing backend.

     ‘file=FILE’
          Log output traces to FILE.  This option is only available if
          QEMU has been compiled with the SIMPLE tracing backend.

The following commands are supported:

‘amend [--object OBJECTDEF] [--image-opts] [-p] [-q] [-f FMT] [-t CACHE] -o OPTIONS FILENAME’
‘bench [-c COUNT] [-d DEPTH] [-f FMT] [--flush-interval=FLUSH_INTERVAL] [-n] [--no-drain] [-o OFFSET] [--pattern=PATTERN] [-q] [-s BUFFER_SIZE] [-S STEP_SIZE] [-t CACHE] [-w] [-U] FILENAME’
     ..  option:: bitmap (–merge SOURCE | –add | –remove | –clear |
     –enable | –disable)...  [-b SOURCE_FILE [-F SOURCE_FMT]] [-g
     GRANULARITY] [–object OBJECTDEF] [–image-opts | -f FMT] FILENAME
     BITMAP
‘check [--object OBJECTDEF] [--image-opts] [-q] [-f FMT] [--output=OFMT] [-r [leaks | all]] [-T SRC_CACHE] [-U] FILENAME’
‘commit [--object OBJECTDEF] [--image-opts] [-q] [-f FMT] [-t CACHE] [-b BASE] [-d] [-p] FILENAME’
‘compare [--object OBJECTDEF] [--image-opts] [-f FMT] [-F FMT] [-T SRC_CACHE] [-p] [-q] [-s] [-U] FILENAME1 FILENAME2’
‘convert [--object OBJECTDEF] [--image-opts] [--target-image-opts] [--bitmaps] [-U] [-C] [-c] [-p] [-q] [-n] [-f FMT] [-t CACHE] [-T SRC_CACHE] [-O OUTPUT_FMT] [-B BACKING_FILE] [-o OPTIONS] [-l SNAPSHOT_PARAM] [-S SPARSE_SIZE] [-m NUM_COROUTINES] [-W] [--salvage] FILENAME [FILENAME2 [...]] OUTPUT_FILENAME’
‘create [--object OBJECTDEF] [-q] [-f FMT] [-b BACKING_FILE] [-F BACKING_FMT] [-u] [-o OPTIONS] FILENAME [SIZE]’
‘dd [--image-opts] [-U] [-f FMT] [-O OUTPUT_FMT] [bs=BLOCK_SIZE] [count=BLOCKS] [skip=BLOCKS] if=INPUT of=OUTPUT’
‘info [--object OBJECTDEF] [--image-opts] [-f FMT] [--output=OFMT] [--backing-chain] [-U] FILENAME’
‘map [--object OBJECTDEF] [--image-opts] [-f FMT] [--output=OFMT] [-U] FILENAME’
‘measure [--output=OFMT] [-O OUTPUT_FMT] [-o OPTIONS] [--size N | [--object OBJECTDEF] [--image-opts] [-f FMT] [-l SNAPSHOT_PARAM] FILENAME]’
‘snapshot [--object OBJECTDEF] [--image-opts] [-U] [-q] [-l | -a SNAPSHOT | -c SNAPSHOT | -d SNAPSHOT] FILENAME’
‘rebase [--object OBJECTDEF] [--image-opts] [-U] [-q] [-f FMT] [-t CACHE] [-T SRC_CACHE] [-p] [-u] -b BACKING_FILE [-F BACKING_FMT] FILENAME’
‘resize [--object OBJECTDEF] [--image-opts] [-f FMT] [--preallocation=PREALLOC] [-q] [--shrink] FILENAME [+ | -]SIZE’

Command parameters:

FILENAME
     is a disk image filename

FMT
     is the disk image format.  It is guessed automatically in most
     cases.  See below for a description of the supported disk formats.

SIZE
     is the disk image size in bytes.  Optional suffixes ‘k’ or ‘K’
     (kilobyte, 1024) ‘M’ (megabyte, 1024k) and ‘G’ (gigabyte, 1024M)
     and T (terabyte, 1024G) are supported.  ‘b’ is ignored.

OUTPUT_FILENAME
     is the destination disk image filename

OUTPUT_FMT
     is the destination format

OPTIONS
     is a comma separated list of format specific options in a
     name=value format.  Use ‘-o ?’ for an overview of the options
     supported by the used format or see the format descriptions below
     for details.

SNAPSHOT_PARAM
     is param used for internal snapshot, format is
     ’snapshot.id=[ID],snapshot.name=[NAME]’ or ’[ID_OR_NAME]’

‘--object OBJECTDEF’
     is a QEMU user creatable object definition.  See the ‘qemu(1)’
     manual page for a description of the object properties.  The most
     common object type is a ‘secret’, which is used to supply passwords
     and/or encryption keys.

‘--image-opts’
     Indicates that the source FILENAME parameter is to be interpreted
     as a full option string, not a plain filename.  This parameter is
     mutually exclusive with the -F parameter.

‘--target-image-opts’
     Indicates that the OUTPUT_FILENAME parameter(s) are to be
     interpreted as a full option string, not a plain filename.  This
     parameter is mutually exclusive with the -O parameters.  It is
     currently required to also use the -N parameter to skip image
     creation.  This restriction may be relaxed in a future release.

‘--force-share (-U)’
     If specified, ‘qemu-img’ will open the image in shared mode,
     allowing other QEMU processes to open it in write mode.  For
     example, this can be used to get the image information (with ’info’
     subcommand) when the image is used by a running guest.  Note that
     this could produce inconsistent results because of concurrent
     metadata changes, etc.  This option is only allowed when opening
     images in read-only mode.

‘--backing-chain’
     will enumerate information about backing files in a disk image
     chain.  Refer below for further description.

‘-c’
     indicates that target image must be compressed (qcow format only)

‘-h’
     with or without a command shows help and lists the supported
     formats

‘-p’
     display progress bar (compare, convert and rebase commands only).
     If the -P option is not used for a command that supports it, the
     progress is reported when the process receives a ‘SIGUSR1’ or
     ‘SIGINFO’ signal.

‘-q’
     Quiet mode - do not print any output (except errors).  There’s no
     progress bar in case both -Q and -P options are used.

‘-S SIZE’
     indicates the consecutive number of bytes that must contain only
     zeros for qemu-img to create a sparse image during conversion.
     This value is rounded down to the nearest 512 bytes.  You may use
     the common size suffixes like ‘k’ for kilobytes.

‘-t CACHE’
     specifies the cache mode that should be used with the (destination)
     file.  See the documentation of the emulator’s ‘-drive cache=...’
     option for allowed values.

‘-T SRC_CACHE’
     specifies the cache mode that should be used with the source
     file(s).  See the documentation of the emulator’s ‘-drive
     cache=...’ option for allowed values.

Parameters to snapshot subcommand:

‘snapshot’
     is the name of the snapshot to create, apply or delete
‘-a’
     applies a snapshot (revert disk to saved state)
‘-c’
     creates a snapshot
‘-d’
     deletes a snapshot
‘-l’
     lists all snapshots in the given image

Parameters to compare subcommand:

‘-f’
     First image format
‘-F’
     Second image format
‘-s’
     Strict mode - fail on different image size or sector allocation

Parameters to convert subcommand:

‘--bitmaps’
     Additionally copy all persistent bitmaps from the top layer of the
     source
‘-n’
     Skip the creation of the target volume
‘-m’
     Number of parallel coroutines for the convert process
‘-W’
     Allow out-of-order writes to the destination.  This option improves
     performance, but is only recommended for preallocated devices like
     host devices or other raw block devices.
‘-C’
     Try to use copy offloading to move data from source image to
     target.  This may improve performance if the data is remote, such
     as with NFS or iSCSI backends, but will not automatically sparsify
     zero sectors, and may result in a fully allocated target image
     depending on the host support for getting allocation information.
‘--salvage’
     Try to ignore I/O errors when reading.  Unless in quiet mode
     (‘-q’), errors will still be printed.  Areas that cannot be read
     from the source will be treated as containing only zeroes.

Parameters to dd subcommand:

‘bs=BLOCK_SIZE’
     defines the block size
‘count=BLOCKS’
     sets the number of input blocks to copy
‘if=INPUT’
     sets the input file
‘of=OUTPUT’
     sets the output file
‘skip=BLOCKS’
     sets the number of input blocks to skip

Command description:

‘amend [--object OBJECTDEF] [--image-opts] [-p] [-q] [-f FMT] [-t CACHE] -o OPTIONS FILENAME’

     Amends the image format specific OPTIONS for the image file
     FILENAME.  Not all file formats support this operation.

‘bench [-c COUNT] [-d DEPTH] [-f FMT] [--flush-interval=FLUSH_INTERVAL] [-n] [--no-drain] [-o OFFSET] [--pattern=PATTERN] [-q] [-s BUFFER_SIZE] [-S STEP_SIZE] [-t CACHE] [-w] [-U] FILENAME’

     Run a simple sequential I/O benchmark on the specified image.  If
     ‘-w’ is specified, a write test is performed, otherwise a read test
     is performed.

     A total number of COUNT I/O requests is performed, each BUFFER_SIZE
     bytes in size, and with DEPTH requests in parallel.  The first
     request starts at the position given by OFFSET, each following
     request increases the current position by STEP_SIZE.  If STEP_SIZE
     is not given, BUFFER_SIZE is used for its value.

     If FLUSH_INTERVAL is specified for a write test, the request queue
     is drained and a flush is issued before new writes are made
     whenever the number of remaining requests is a multiple of
     FLUSH_INTERVAL.  If additionally ‘--no-drain’ is specified, a flush
     is issued without draining the request queue first.

     If ‘-n’ is specified, the native AIO backend is used if possible.
     On Linux, this option only works if ‘-t none’ or ‘-t directsync’ is
     specified as well.

     For write tests, by default a buffer filled with zeros is written.
     This can be overridden with a pattern byte specified by PATTERN.

‘bitmap (--merge SOURCE | --add | --remove | --clear | --enable | --disable)... [-b SOURCE_FILE [-F SOURCE_FMT]] [-g GRANULARITY] [--object OBJECTDEF] [--image-opts | -f FMT] FILENAME BITMAP’

     Perform one or more modifications of the persistent bitmap BITMAP
     in the disk image FILENAME.  The various modifications are:

     ‘add’
          create BITMAP, enabled to record future edits.
     ‘remove’
          remove BITMAP.
     ‘clear’
          clear BITMAP.
     ‘enable’
          change BITMAP to start recording future edits.
     ‘disable’
          change BITMAP to stop recording future edits.
     ‘merge SOURCE’
          merge the contents of the SOURCE bitmap into BITMAP.

     Additional options include ‘-g’ which sets a non-default
     GRANULARITY for ‘--add’, and ‘-b’ and ‘-F’ which select an
     alternative source file for all SOURCE bitmaps used by ‘--merge’.

     To see what bitmaps are present in an image, use ‘qemu-img info’.

‘check [--object OBJECTDEF] [--image-opts] [-q] [-f FMT] [--output=OFMT] [-r [leaks | all]] [-T SRC_CACHE] [-U] FILENAME’

     Perform a consistency check on the disk image FILENAME.  The
     command can output in the format OFMT which is either ‘human’ or
     ‘json’.  The JSON output is an object of QAPI type ‘ImageCheck’.

     If ‘-r’ is specified, qemu-img tries to repair any inconsistencies
     found during the check.  ‘-r leaks’ repairs only cluster leaks,
     whereas ‘-r all’ fixes all kinds of errors, with a higher risk of
     choosing the wrong fix or hiding corruption that has already
     occurred.

     Only the formats ‘qcow2’, ‘qed’ and ‘vdi’ support consistency
     checks.

     In case the image does not have any inconsistencies, check exits
     with ‘0’.  Other exit codes indicate the kind of inconsistency
     found or if another error occurred.  The following table summarizes
     all exit codes of the check subcommand:

     ‘0’
          Check completed, the image is (now) consistent
     ‘1’
          Check not completed because of internal errors
     ‘2’
          Check completed, image is corrupted
     ‘3’
          Check completed, image has leaked clusters, but is not
          corrupted
     ‘63’
          Checks are not supported by the image format

     If ‘-r’ is specified, exit codes representing the image state refer
     to the state after (the attempt at) repairing it.  That is, a
     successful ‘-r all’ will yield the exit code 0, independently of
     the image state before.

‘commit [--object OBJECTDEF] [--image-opts] [-q] [-f FMT] [-t CACHE] [-b BASE] [-d] [-p] FILENAME’

     Commit the changes recorded in FILENAME in its base image or
     backing file.  If the backing file is smaller than the snapshot,
     then the backing file will be resized to be the same size as the
     snapshot.  If the snapshot is smaller than the backing file, the
     backing file will not be truncated.  If you want the backing file
     to match the size of the smaller snapshot, you can safely truncate
     it yourself once the commit operation successfully completes.

     The image FILENAME is emptied after the operation has succeeded.
     If you do not need FILENAME afterwards and intend to drop it, you
     may skip emptying FILENAME by specifying the ‘-d’ flag.

     If the backing chain of the given image file FILENAME has more than
     one layer, the backing file into which the changes will be
     committed may be specified as BASE (which has to be part of
     FILENAME’s backing chain).  If BASE is not specified, the immediate
     backing file of the top image (which is FILENAME) will be used.
     Note that after a commit operation all images between BASE and the
     top image will be invalid and may return garbage data when read.
     For this reason, ‘-b’ implies ‘-d’ (so that the top image stays
     valid).

‘compare [--object OBJECTDEF] [--image-opts] [-f FMT] [-F FMT] [-T SRC_CACHE] [-p] [-q] [-s] [-U] FILENAME1 FILENAME2’

     Check if two images have the same content.  You can compare images
     with different format or settings.

     The format is probed unless you specify it by -F (used for
     FILENAME1) and/or -F (used for FILENAME2) option.

     By default, images with different size are considered identical if
     the larger image contains only unallocated and/or zeroed sectors in
     the area after the end of the other image.  In addition, if any
     sector is not allocated in one image and contains only zero bytes
     in the second one, it is evaluated as equal.  You can use Strict
     mode by specifying the -S option.  When compare runs in Strict
     mode, it fails in case image size differs or a sector is allocated
     in one image and is not allocated in the second one.

     By default, compare prints out a result message.  This message
     displays information that both images are same or the position of
     the first different byte.  In addition, result message can report
     different image size in case Strict mode is used.

     Compare exits with ‘0’ in case the images are equal and with ‘1’ in
     case the images differ.  Other exit codes mean an error occurred
     during execution and standard error output should contain an error
     message.  The following table sumarizes all exit codes of the
     compare subcommand:

     ‘0’
          Images are identical
     ‘1’
          Images differ
     ‘2’
          Error on opening an image
     ‘3’
          Error on checking a sector allocation
     ‘4’
          Error on reading data

‘convert [--object OBJECTDEF] [--image-opts] [--target-image-opts] [--bitmaps] [-U] [-C] [-c] [-p] [-q] [-n] [-f FMT] [-t CACHE] [-T SRC_CACHE] [-O OUTPUT_FMT] [-B BACKING_FILE] [-o OPTIONS] [-l SNAPSHOT_PARAM] [-S SPARSE_SIZE] [-m NUM_COROUTINES] [-W] FILENAME [FILENAME2 [...]] OUTPUT_FILENAME’

     Convert the disk image FILENAME or a snapshot SNAPSHOT_PARAM to
     disk image OUTPUT_FILENAME using format OUTPUT_FMT.  It can be
     optionally compressed (‘-c’ option) or use any format specific
     options like encryption (‘-o’ option).

     Only the formats ‘qcow’ and ‘qcow2’ support compression.  The
     compression is read-only.  It means that if a compressed sector is
     rewritten, then it is rewritten as uncompressed data.

     Image conversion is also useful to get smaller image when using a
     growable format such as ‘qcow’: the empty sectors are detected and
     suppressed from the destination image.

     SPARSE_SIZE indicates the consecutive number of bytes (defaults to
     4k) that must contain only zeros for qemu-img to create a sparse
     image during conversion.  If SPARSE_SIZE is 0, the source will not
     be scanned for unallocated or zero sectors, and the destination
     image will always be fully allocated.

     You can use the BACKING_FILE option to force the output image to be
     created as a copy on write image of the specified base image; the
     BACKING_FILE should have the same content as the input’s base
     image, however the path, image format, etc may differ.

     If a relative path name is given, the backing file is looked up
     relative to the directory containing OUTPUT_FILENAME.

     If the ‘-n’ option is specified, the target volume creation will be
     skipped.  This is useful for formats such as ‘rbd’ if the target
     volume has already been created with site specific options that
     cannot be supplied through qemu-img.

     Out of order writes can be enabled with ‘-W’ to improve
     performance.  This is only recommended for preallocated devices
     like host devices or other raw block devices.  Out of order write
     does not work in combination with creating compressed images.

     NUM_COROUTINES specifies how many coroutines work in parallel
     during the convert process (defaults to 8).

‘create [--object OBJECTDEF] [-q] [-f FMT] [-b BACKING_FILE] [-F BACKING_FMT] [-u] [-o OPTIONS] FILENAME [SIZE]’

     Create the new disk image FILENAME of size SIZE and format FMT.
     Depending on the file format, you can add one or more OPTIONS that
     enable additional features of this format.

     If the option BACKING_FILE is specified, then the image will record
     only the differences from BACKING_FILE.  No size needs to be
     specified in this case.  BACKING_FILE will never be modified unless
     you use the ‘commit’ monitor command (or qemu-img commit).

     If a relative path name is given, the backing file is looked up
     relative to the directory containing FILENAME.

     Note that a given backing file will be opened to check that it is
     valid.  Use the ‘-u’ option to enable unsafe backing file mode,
     which means that the image will be created even if the associated
     backing file cannot be opened.  A matching backing file must be
     created or additional options be used to make the backing file
     specification valid when you want to use an image created this way.

     The size can also be specified using the SIZE option with ‘-o’, it
     doesn’t need to be specified separately in this case.

‘dd [--image-opts] [-U] [-f FMT] [-O OUTPUT_FMT] [bs=BLOCK_SIZE] [count=BLOCKS] [skip=BLOCKS] if=INPUT of=OUTPUT’

     Dd copies from INPUT file to OUTPUT file converting it from FMT
     format to OUTPUT_FMT format.

     The data is by default read and written using blocks of 512 bytes
     but can be modified by specifying BLOCK_SIZE.  If count=BLOCKS is
     specified dd will stop reading input after reading BLOCKS input
     blocks.

     The size syntax is similar to dd(1)’s size syntax.

‘info [--object OBJECTDEF] [--image-opts] [-f FMT] [--output=OFMT] [--backing-chain] [-U] FILENAME’

     Give information about the disk image FILENAME.  Use it in
     particular to know the size reserved on disk which can be different
     from the displayed size.  If VM snapshots are stored in the disk
     image, they are displayed too.

     If a disk image has a backing file chain, information about each
     disk image in the chain can be recursively enumerated by using the
     option ‘--backing-chain’.

     For instance, if you have an image chain like:

          base.qcow2 <- snap1.qcow2 <- snap2.qcow2

     To enumerate information about each disk image in the above chain,
     starting from top to base, do:

          qemu-img info --backing-chain snap2.qcow2

     The command can output in the format OFMT which is either ‘human’
     or ‘json’.  The JSON output is an object of QAPI type ‘ImageInfo’;
     with ‘--backing-chain’, it is an array of ‘ImageInfo’ objects.

     ‘--output=human’ reports the following information (for every image
     in the chain):
     IMAGE
          The image file name

     FILE FORMAT
          The image format

     VIRTUAL SIZE
          The size of the guest disk

     DISK SIZE
          How much space the image file occupies on the host file system
          (may be shown as 0 if this information is unavailable, e.g.
          because there is no file system)

     CLUSTER_SIZE
          Cluster size of the image format, if applicable

     ENCRYPTED
          Whether the image is encrypted (only present if so)

     CLEANLY SHUT DOWN
          This is shown as ‘no’ if the image is dirty and will have to
          be auto-repaired the next time it is opened in qemu.

     BACKING FILE
          The backing file name, if present

     BACKING FILE FORMAT
          The format of the backing file, if the image enforces it

     SNAPSHOT LIST
          A list of all internal snapshots

     FORMAT SPECIFIC INFORMATION
          Further information whose structure depends on the image
          format.  This section is a textual representation of the
          respective ‘ImageInfoSpecific*’ QAPI object (e.g.
          ‘ImageInfoSpecificQCow2’ for qcow2 images).

‘map [--object OBJECTDEF] [--image-opts] [-f FMT] [--output=OFMT] [-U] FILENAME’

     Dump the metadata of image FILENAME and its backing file chain.  In
     particular, this commands dumps the allocation state of every
     sector of FILENAME, together with the topmost file that allocates
     it in the backing file chain.

     Two option formats are possible.  The default format (‘human’) only
     dumps known-nonzero areas of the file.  Known-zero parts of the
     file are omitted altogether, and likewise for parts that are not
     allocated throughout the chain.  ‘qemu-img’ output will identify a
     file from where the data can be read, and the offset in the file.
     Each line will include four fields, the first three of which are
     hexadecimal numbers.  For example the first line of:
          Offset          Length          Mapped to       File
          0               0x20000         0x50000         /tmp/overlay.qcow2
          0x100000        0x10000         0x95380000      /tmp/backing.qcow2
     means that 0x20000 (131072) bytes starting at offset 0 in the image
     are available in /tmp/overlay.qcow2 (opened in ‘raw’ format)
     starting at offset 0x50000 (327680).  Data that is compressed,
     encrypted, or otherwise not available in raw format will cause an
     error if ‘human’ format is in use.  Note that file names can
     include newlines, thus it is not safe to parse this output format
     in scripts.

     The alternative format ‘json’ will return an array of dictionaries
     in JSON format.  It will include similar information in the
     ‘start’, ‘length’, ‘offset’ fields; it will also include other more
     specific information:
        − whether the sectors contain actual data or not (boolean field
          ‘data’; if false, the sectors are either unallocated or stored
          as optimized all-zero clusters);

        − whether the data is known to read as zero (boolean field
          ‘zero’);

        − in order to make the output shorter, the target file is
          expressed as a ‘depth’; for example, a depth of 2 refers to
          the backing file of the backing file of FILENAME.

     In JSON format, the ‘offset’ field is optional; it is absent in
     cases where ‘human’ format would omit the entry or exit with an
     error.  If ‘data’ is false and the ‘offset’ field is present, the
     corresponding sectors in the file are not yet in use, but they are
     preallocated.

     For more information, consult ‘include/block/block.h’ in QEMU’s
     source code.

‘measure [--output=OFMT] [-O OUTPUT_FMT] [-o OPTIONS] [--size N | [--object OBJECTDEF] [--image-opts] [-f FMT] [-l SNAPSHOT_PARAM] FILENAME]’

     Calculate the file size required for a new image.  This information
     can be used to size logical volumes or SAN LUNs appropriately for
     the image that will be placed in them.  The values reported are
     guaranteed to be large enough to fit the image.  The command can
     output in the format OFMT which is either ‘human’ or ‘json’.  The
     JSON output is an object of QAPI type ‘BlockMeasureInfo’.

     If the size N is given then act as if creating a new empty image
     file using ‘qemu-img create’.  If FILENAME is given then act as if
     converting an existing image file using ‘qemu-img convert’.  The
     format of the new file is given by OUTPUT_FMT while the format of
     an existing file is given by FMT.

     A snapshot in an existing image can be specified using
     SNAPSHOT_PARAM.

     The following fields are reported:
          required size: 524288
          fully allocated size: 1074069504
          bitmaps size: 0

     The ‘required size’ is the file size of the new image.  It may be
     smaller than the virtual disk size if the image format supports
     compact representation.

     The ‘fully allocated size’ is the file size of the new image once
     data has been written to all sectors.  This is the maximum size
     that the image file can occupy with the exception of internal
     snapshots, dirty bitmaps, vmstate data, and other advanced image
     format features.

     The ‘bitmaps size’ is the additional size required in order to copy
     bitmaps from a source image in addition to the guest-visible data;
     the line is omitted if either source or destination lacks bitmap
     support, or 0 if bitmaps are supported but there is nothing to
     copy.

‘snapshot [--object OBJECTDEF] [--image-opts] [-U] [-q] [-l | -a SNAPSHOT | -c SNAPSHOT | -d SNAPSHOT] FILENAME’

     List, apply, create or delete snapshots in image FILENAME.

‘rebase [--object OBJECTDEF] [--image-opts] [-U] [-q] [-f FMT] [-t CACHE] [-T SRC_CACHE] [-p] [-u] -b BACKING_FILE [-F BACKING_FMT] FILENAME’

     Changes the backing file of an image.  Only the formats ‘qcow2’ and
     ‘qed’ support changing the backing file.

     The backing file is changed to BACKING_FILE and (if the image
     format of FILENAME supports this) the backing file format is
     changed to BACKING_FMT.  If BACKING_FILE is specified as “” (the
     empty string), then the image is rebased onto no backing file (i.e.
     it will exist independently of any backing file).

     If a relative path name is given, the backing file is looked up
     relative to the directory containing FILENAME.

     CACHE specifies the cache mode to be used for FILENAME, whereas
     SRC_CACHE specifies the cache mode for reading backing files.

     There are two different modes in which ‘rebase’ can operate:
     ‘Safe mode’
          This is the default mode and performs a real rebase operation.
          The new backing file may differ from the old one and qemu-img
          rebase will take care of keeping the guest-visible content of
          FILENAME unchanged.

          In order to achieve this, any clusters that differ between
          BACKING_FILE and the old backing file of FILENAME are merged
          into FILENAME before actually changing the backing file.

          Note that the safe mode is an expensive operation, comparable
          to converting an image.  It only works if the old backing file
          still exists.

     ‘Unsafe mode’
          qemu-img uses the unsafe mode if ‘-u’ is specified.  In this
          mode, only the backing file name and format of FILENAME is
          changed without any checks on the file contents.  The user
          must take care of specifying the correct new backing file, or
          the guest-visible content of the image will be corrupted.

          This mode is useful for renaming or moving the backing file to
          somewhere else.  It can be used without an accessible old
          backing file, i.e.  you can use it to fix an image whose
          backing file has already been moved/renamed.

     You can use ‘rebase’ to perform a “diff” operation on two disk
     images.  This can be useful when you have copied or cloned a guest,
     and you want to get back to a thin image on top of a template or
     base image.

     Say that ‘base.img’ has been cloned as ‘modified.img’ by copying
     it, and that the ‘modified.img’ guest has run so there are now some
     changes compared to ‘base.img’.  To construct a thin image called
     ‘diff.qcow2’ that contains just the differences, do:

          qemu-img create -f qcow2 -b modified.img diff.qcow2
          qemu-img rebase -b base.img diff.qcow2

     At this point, ‘modified.img’ can be discarded, since ‘base.img +
     diff.qcow2’ contains the same information.

‘resize [--object OBJECTDEF] [--image-opts] [-f FMT] [--preallocation=PREALLOC] [-q] [--shrink] FILENAME [+ | -]SIZE’

     Change the disk image as if it had been created with SIZE.

     Before using this command to shrink a disk image, you MUST use file
     system and partitioning tools inside the VM to reduce allocated
     file systems and partition sizes accordingly.  Failure to do so
     will result in data loss!

     When shrinking images, the ‘--shrink’ option must be given.  This
     informs qemu-img that the user acknowledges all loss of data beyond
     the truncated image’s end.

     After using this command to grow a disk image, you must use file
     system and partitioning tools inside the VM to actually begin using
     the new space on the device.

     When growing an image, the ‘--preallocation’ option may be used to
     specify how the additional image area should be allocated on the
     host.  See the format description in the ‘NOTES’ section which
     values are allowed.  Using this option may result in slightly more
     data being allocated than necessary.

2.8.5 ‘qemu-nbd’ Invocation
---------------------------

     qemu-nbd [OPTION]... FILENAME

     qemu-nbd -L [OPTION]...

     qemu-nbd -d DEV

Export a QEMU disk image using the NBD protocol.

Other uses:
   • Bind a /dev/nbdX block device to a QEMU server (on Linux).
   • As a client to query exports of a remote NBD server.

FILENAME is a disk image filename, or a set of block driver options if
‘--image-opts’ is specified.

DEV is an NBD device.

‘--object type,id=ID,...props...’
     Define a new instance of the TYPE object class identified by ID.
     See the ‘qemu(1)’ manual page for full details of the properties
     supported.  The common object types that it makes sense to define
     are the ‘secret’ object, which is used to supply passwords and/or
     encryption keys, and the ‘tls-creds’ object, which is used to
     supply TLS credentials for the qemu-nbd server or client.
‘-p, --port=PORT’
     The TCP port to listen on as a server, or connect to as a client
     (default ‘10809’).
‘-o, --offset=OFFSET’
     The offset into the image.
‘-b, --bind=IFACE’
     The interface to bind to as a server, or connect to as a client
     (default ‘0.0.0.0’).
‘-k, --socket=PATH’
     Use a unix socket with path PATH.
‘--image-opts’
     Treat FILENAME as a set of image options, instead of a plain
     filename.  If this flag is specified, the -F flag should not be
     used, instead the ’‘format=’’ option should be set.
‘-f, --format=FMT’
     Force the use of the block driver for format FMT instead of
     auto-detecting.
‘-r, --read-only’
     Export the disk as read-only.
‘-P, --partition=NUM’
     Deprecated: Only expose MBR partition NUM.  Understands physical
     partitions 1-4 and logical partition 5.  New code should instead
     use ‘--image-opts’ with the raw driver wrapping a subset of the
     original image.
‘-B, --bitmap=NAME’
     If FILENAME has a qcow2 persistent bitmap NAME, expose that bitmap
     via the “qemu:dirty-bitmap:NAME” context accessible through
     NBD_OPT_SET_META_CONTEXT.
‘-s, --snapshot’
     Use FILENAME as an external snapshot, create a temporary file with
     backing_file=FILENAME, redirect the write to the temporary one.
‘-l, --load-snapshot=SNAPSHOT_PARAM’
     Load an internal snapshot inside FILENAME and export it as an
     read-only device, SNAPSHOT_PARAM format is
     ’snapshot.id=[ID],snapshot.name=[NAME]’ or ’[ID_OR_NAME]’
‘-n, --nocache’
‘--cache=CACHE’
     The cache mode to be used with the file.  See the documentation of
     the emulator’s ‘-drive cache=...’ option for allowed values.
‘--aio=AIO’
     Set the asynchronous I/O mode between ‘threads’ (the default) and
     ‘native’ (Linux only).
‘--discard=DISCARD’
     Control whether “discard” (also known as “trim” or “unmap”)
     requests are ignored or passed to the filesystem.  DISCARD is one
     of ‘ignore’ (or ‘off’), ‘unmap’ (or ‘on’).  The default is
     ‘ignore’.
‘--detect-zeroes=DETECT-ZEROES’
     Control the automatic conversion of plain zero writes by the OS to
     driver-specific optimized zero write commands.  DETECT-ZEROES is
     one of ‘off’, ‘on’ or ‘unmap’.  ‘unmap’ converts a zero write to an
     unmap operation and can only be used if DISCARD is set to ‘unmap’.
     The default is ‘off’.
‘-c, --connect=DEV’
     Connect FILENAME to NBD device DEV (Linux only).
‘-d, --disconnect’
     Disconnect the device DEV (Linux only).
‘-e, --shared=NUM’
     Allow up to NUM clients to share the device (default ‘1’).  Safe
     for readers, but for now, consistency is not guaranteed between
     multiple writers.
‘-t, --persistent’
     Don’t exit on the last connection.
‘-x, --export-name=NAME’
     Set the NBD volume export name (default of a zero-length string).
‘-D, --description=DESCRIPTION’
     Set the NBD volume export description, as a human-readable string.
‘-L, --list’
     Connect as a client and list all details about the exports exposed
     by a remote NBD server.  This enables list mode, and is
     incompatible with options that change behavior related to a
     specific export (such as ‘--export-name’, ‘--offset’, ...).
‘--tls-creds=ID’
     Enable mandatory TLS encryption for the server by setting the ID of
     the TLS credentials object previously created with the –object
     option; or provide the credentials needed for connecting as a
     client in list mode.
‘--fork’
     Fork off the server process and exit the parent once the server is
     running.
‘--pid-file=PATH’
     Store the server’s process ID in the given file.
‘--tls-authz=ID’
     Specify the ID of a qauthz object previously created with the
     –object option.  This will be used to authorize connecting users
     against their x509 distinguished name.
‘-v, --verbose’
     Display extra debugging information.
‘-h, --help’
     Display this help and exit.
‘-V, --version’
     Display version information and exit.
‘-T, --trace [[enable=]PATTERN][,events=FILE][,file=FILE]’
     Specify tracing options.

     ‘[enable=]PATTERN’
          Immediately enable events matching PATTERN (either event name
          or a globbing pattern).  This option is only available if QEMU
          has been compiled with the SIMPLE, LOG or FTRACE tracing
          backend.  To specify multiple events or patterns, specify the
          ‘-trace’ option multiple times.

          Use ‘-trace help’ to print a list of names of trace points.

     ‘events=FILE’
          Immediately enable events listed in FILE.  The file must
          contain one event name (as listed in the ‘trace-events-all’
          file) per line; globbing patterns are accepted too.  This
          option is only available if QEMU has been compiled with the
          SIMPLE, LOG or FTRACE tracing backend.

     ‘file=FILE’
          Log output traces to FILE.  This option is only available if
          QEMU has been compiled with the SIMPLE tracing backend.

Start a server listening on port 10809 that exposes only the
guest-visible contents of a qcow2 file, with no TLS encryption, and with
the default export name (an empty string).  The command is one-shot, and
will block until the first successful client disconnects:

     qemu-nbd -f qcow2 file.qcow2

Start a long-running server listening with encryption on port 10810, and
whitelist clients with a specific X.509 certificate to connect to a 1
megabyte subset of a raw file, using the export name ’subset’:

     qemu-nbd \
       --object tls-creds-x509,id=tls0,endpoint=server,dir=/path/to/qemutls \
       --object 'authz-simple,id=auth0,identity=CN=laptop.example.com,,\
                 O=Example Org,,L=London,,ST=London,,C=GB' \
       --tls-creds tls0 --tls-authz auth0 \
       -t -x subset -p 10810 \
       --image-opts driver=raw,offset=1M,size=1M,file.driver=file,file.filename=file.raw

Serve a read-only copy of just the first MBR partition of a guest image
over a Unix socket with as many as 5 simultaneous readers, with a
persistent process forked as a daemon:

     qemu-nbd --fork --persistent --shared=5 --socket=/path/to/sock \
       --partition=1 --read-only --format=qcow2 file.qcow2

Expose the guest-visible contents of a qcow2 file via a block device
/dev/nbd0 (and possibly creating /dev/nbd0p1 and friends for partitions
found within), then disconnect the device when done.  Access to bind
qemu-nbd to an /dev/nbd device generally requires root privileges, and
may also require the execution of ‘modprobe nbd’ to enable the kernel
NBD client module.  _CAUTION_: Do not use this method to mount
filesystems from an untrusted guest image - a malicious guest may have
prepared the image to attempt to trigger kernel bugs in partition
probing or file system mounting.

     qemu-nbd -c /dev/nbd0 -f qcow2 file.qcow2
     qemu-nbd -d /dev/nbd0

Query a remote server to see details about what export(s) it is serving
on port 10809, and authenticating via PSK:

     qemu-nbd \
       --object tls-creds-psk,id=tls0,dir=/tmp/keys,username=eblake,endpoint=client \
       --tls-creds tls0 -L -b remote.example.com

QEMU block driver reference manual

2.8.6 Disk image file formats
-----------------------------

QEMU supports many image file formats that can be used with VMs as well
as with any of the tools (like ‘qemu-img’).  This includes the preferred
formats raw and qcow2 as well as formats that are supported for
compatibility with older QEMU versions or other hypervisors.

Depending on the image format, different options can be passed to
‘qemu-img create’ and ‘qemu-img convert’ using the ‘-o’ option.  This
section describes each format and the options that are supported for it.

‘raw’

     Raw disk image format.  This format has the advantage of being
     simple and easily exportable to all other emulators.  If your file
     system supports _holes_ (for example in ext2 or ext3 on Linux or
     NTFS on Windows), then only the written sectors will reserve space.
     Use ‘qemu-img info’ to know the real size used by the image or ‘ls
     -ls’ on Unix/Linux.

     Supported options:
     ‘preallocation’
          Preallocation mode (allowed values: ‘off’, ‘falloc’, ‘full’).
          ‘falloc’ mode preallocates space for image by calling
          posix_fallocate().  ‘full’ mode preallocates space for image
          by writing data to underlying storage.  This data may or may
          not be zero, depending on the storage location.

‘qcow2’
     QEMU image format, the most versatile format.  Use it to have
     smaller images (useful if your filesystem does not supports holes,
     for example on Windows), zlib based compression and support of
     multiple VM snapshots.

     Supported options:
     ‘compat’
          Determines the qcow2 version to use.  ‘compat=0.10’ uses the
          traditional image format that can be read by any QEMU since
          0.10.  ‘compat=1.1’ enables image format extensions that only
          QEMU 1.1 and newer understand (this is the default).  Amongst
          others, this includes zero clusters, which allow efficient
          copy-on-read for sparse images.

     ‘backing_file’
          File name of a base image (see ‘create’ subcommand)
     ‘backing_fmt’
          Image format of the base image
     ‘encryption’
          This option is deprecated and equivalent to
          ‘encrypt.format=aes’

     ‘encrypt.format’

          If this is set to ‘luks’, it requests that the qcow2 payload
          (not qcow2 header) be encrypted using the LUKS format.  The
          passphrase to use to unlock the LUKS key slot is given by the
          ‘encrypt.key-secret’ parameter.  LUKS encryption parameters
          can be tuned with the other ‘encrypt.*’ parameters.

          If this is set to ‘aes’, the image is encrypted with 128-bit
          AES-CBC. The encryption key is given by the
          ‘encrypt.key-secret’ parameter.  This encryption format is
          considered to be flawed by modern cryptography standards,
          suffering from a number of design problems:

             − The AES-CBC cipher is used with predictable
               initialization vectors based on the sector number.  This
               makes it vulnerable to chosen plaintext attacks which can
               reveal the existence of encrypted data.
             − The user passphrase is directly used as the encryption
               key.  A poorly chosen or short passphrase will compromise
               the security of the encryption.
             − In the event of the passphrase being compromised there is
               no way to change the passphrase to protect data in any
               qcow images.  The files must be cloned, using a different
               encryption passphrase in the new file.  The original file
               must then be securely erased using a program like shred,
               though even this is ineffective with many modern storage
               technologies.

          The use of this is no longer supported in system emulators.
          Support only remains in the command line utilities, for the
          purposes of data liberation and interoperability with old
          versions of QEMU. The ‘luks’ format should be used instead.

     ‘encrypt.key-secret’

          Provides the ID of a ‘secret’ object that contains the
          passphrase (‘encrypt.format=luks’) or encryption key
          (‘encrypt.format=aes’).

     ‘encrypt.cipher-alg’

          Name of the cipher algorithm and key length.  Currently
          defaults to ‘aes-256’.  Only used when ‘encrypt.format=luks’.

     ‘encrypt.cipher-mode’

          Name of the encryption mode to use.  Currently defaults to
          ‘xts’.  Only used when ‘encrypt.format=luks’.

     ‘encrypt.ivgen-alg’

          Name of the initialization vector generator algorithm.
          Currently defaults to ‘plain64’.  Only used when
          ‘encrypt.format=luks’.

     ‘encrypt.ivgen-hash-alg’

          Name of the hash algorithm to use with the initialization
          vector generator (if required).  Defaults to ‘sha256’.  Only
          used when ‘encrypt.format=luks’.

     ‘encrypt.hash-alg’

          Name of the hash algorithm to use for PBKDF algorithm Defaults
          to ‘sha256’.  Only used when ‘encrypt.format=luks’.

     ‘encrypt.iter-time’

          Amount of time, in milliseconds, to use for PBKDF algorithm
          per key slot.  Defaults to ‘2000’.  Only used when
          ‘encrypt.format=luks’.

     ‘cluster_size’
          Changes the qcow2 cluster size (must be between 512 and 2M).
          Smaller cluster sizes can improve the image file size whereas
          larger cluster sizes generally provide better performance.

     ‘preallocation’
          Preallocation mode (allowed values: ‘off’, ‘metadata’,
          ‘falloc’, ‘full’).  An image with preallocated metadata is
          initially larger but can improve performance when the image
          needs to grow.  ‘falloc’ and ‘full’ preallocations are like
          the same options of ‘raw’ format, but sets up metadata also.

     ‘lazy_refcounts’
          If this option is set to ‘on’, reference count updates are
          postponed with the goal of avoiding metadata I/O and improving
          performance.  This is particularly interesting with
          ‘cache=writethrough’ which doesn’t batch metadata updates.
          The tradeoff is that after a host crash, the reference count
          tables must be rebuilt, i.e.  on the next open an (automatic)
          ‘qemu-img check -r all’ is required, which may take some time.

          This option can only be enabled if ‘compat=1.1’ is specified.

     ‘nocow’
          If this option is set to ‘on’, it will turn off COW of the
          file.  It’s only valid on btrfs, no effect on other file
          systems.

          Btrfs has low performance when hosting a VM image file, even
          more when the guest on the VM also using btrfs as file system.
          Turning off COW is a way to mitigate this bad performance.
          Generally there are two ways to turn off COW on btrfs: a)
          Disable it by mounting with nodatacow, then all newly created
          files will be NOCOW. b) For an empty file, add the NOCOW file
          attribute.  That’s what this option does.

          Note: this option is only valid to new or empty files.  If
          there is an existing file which is COW and has data blocks
          already, it couldn’t be changed to NOCOW by setting
          ‘nocow=on’.  One can issue ‘lsattr filename’ to check if the
          NOCOW flag is set or not (Capital ’C’ is NOCOW flag).

‘qed’
     Old QEMU image format with support for backing files and compact
     image files (when your filesystem or transport medium does not
     support holes).

     When converting QED images to qcow2, you might want to consider
     using the ‘lazy_refcounts=on’ option to get a more QED-like
     behaviour.

     Supported options:
     ‘backing_file’
          File name of a base image (see ‘create’ subcommand).
     ‘backing_fmt’
          Image file format of backing file (optional).  Useful if the
          format cannot be autodetected because it has no header, like
          some vhd/vpc files.
     ‘cluster_size’
          Changes the cluster size (must be power-of-2 between 4K and
          64K). Smaller cluster sizes can improve the image file size
          whereas larger cluster sizes generally provide better
          performance.
     ‘table_size’
          Changes the number of clusters per L1/L2 table (must be
          power-of-2 between 1 and 16).  There is normally no need to
          change this value but this option can be used for performance
          benchmarking.

‘qcow’
     Old QEMU image format with support for backing files, compact image
     files, encryption and compression.

     Supported options:
     ‘backing_file’
          File name of a base image (see ‘create’ subcommand)
     ‘encryption’
          This option is deprecated and equivalent to
          ‘encrypt.format=aes’

     ‘encrypt.format’
          If this is set to ‘aes’, the image is encrypted with 128-bit
          AES-CBC. The encryption key is given by the
          ‘encrypt.key-secret’ parameter.  This encryption format is
          considered to be flawed by modern cryptography standards,
          suffering from a number of design problems enumerated
          previously against the ‘qcow2’ image format.

          The use of this is no longer supported in system emulators.
          Support only remains in the command line utilities, for the
          purposes of data liberation and interoperability with old
          versions of QEMU.

          Users requiring native encryption should use the ‘qcow2’
          format instead with ‘encrypt.format=luks’.

     ‘encrypt.key-secret’

          Provides the ID of a ‘secret’ object that contains the
          encryption key (‘encrypt.format=aes’).

‘luks’

     LUKS v1 encryption format, compatible with Linux
     dm-crypt/cryptsetup

     Supported options:

     ‘key-secret’

          Provides the ID of a ‘secret’ object that contains the
          passphrase.

     ‘cipher-alg’

          Name of the cipher algorithm and key length.  Currently
          defaults to ‘aes-256’.

     ‘cipher-mode’

          Name of the encryption mode to use.  Currently defaults to
          ‘xts’.

     ‘ivgen-alg’

          Name of the initialization vector generator algorithm.
          Currently defaults to ‘plain64’.

     ‘ivgen-hash-alg’

          Name of the hash algorithm to use with the initialization
          vector generator (if required).  Defaults to ‘sha256’.

     ‘hash-alg’

          Name of the hash algorithm to use for PBKDF algorithm Defaults
          to ‘sha256’.

     ‘iter-time’

          Amount of time, in milliseconds, to use for PBKDF algorithm
          per key slot.  Defaults to ‘2000’.

‘vdi’
     VirtualBox 1.1 compatible image format.  Supported options:
     ‘static’
          If this option is set to ‘on’, the image is created with
          metadata preallocation.

‘vmdk’
     VMware 3 and 4 compatible image format.

     Supported options:
     ‘backing_file’
          File name of a base image (see ‘create’ subcommand).
     ‘compat6’
          Create a VMDK version 6 image (instead of version 4)
     ‘hwversion’
          Specify vmdk virtual hardware version.  Compat6 flag cannot be
          enabled if hwversion is specified.
     ‘subformat’
          Specifies which VMDK subformat to use.  Valid options are
          ‘monolithicSparse’ (default), ‘monolithicFlat’,
          ‘twoGbMaxExtentSparse’, ‘twoGbMaxExtentFlat’ and
          ‘streamOptimized’.

‘vpc’
     VirtualPC compatible image format (VHD). Supported options:
     ‘subformat’
          Specifies which VHD subformat to use.  Valid options are
          ‘dynamic’ (default) and ‘fixed’.

‘VHDX’
     Hyper-V compatible image format (VHDX). Supported options:
     ‘subformat’
          Specifies which VHDX subformat to use.  Valid options are
          ‘dynamic’ (default) and ‘fixed’.
     ‘block_state_zero’
          Force use of payload blocks of type ’ZERO’.  Can be set to
          ‘on’ (default) or ‘off’.  When set to ‘off’, new blocks will
          be created as ‘PAYLOAD_BLOCK_NOT_PRESENT’, which means parsers
          are free to return arbitrary data for those blocks.  Do not
          set to ‘off’ when using ‘qemu-img convert’ with
          ‘subformat=dynamic’.
     ‘block_size’
          Block size; min 1 MB, max 256 MB. 0 means auto-calculate based
          on image size.
     ‘log_size’
          Log size; min 1 MB.

2.8.6.1 Read-only formats
.........................

More disk image file formats are supported in a read-only mode.
‘bochs’
     Bochs images of ‘growing’ type.
‘cloop’
     Linux Compressed Loop image, useful only to reuse directly
     compressed CD-ROM images present for example in the Knoppix
     CD-ROMs.
‘dmg’
     Apple disk image.
‘parallels’
     Parallels disk image format.

2.8.7 Using host drives
-----------------------

In addition to disk image files, QEMU can directly access host devices.
We describe here the usage for QEMU version >= 0.8.3.

2.8.7.1 Linux
.............

On Linux, you can directly use the host device filename instead of a
disk image filename provided you have enough privileges to access it.
For example, use ‘/dev/cdrom’ to access to the CDROM.

‘CD’
     You can specify a CDROM device even if no CDROM is loaded.  QEMU
     has specific code to detect CDROM insertion or removal.  CDROM
     ejection by the guest OS is supported.  Currently only data CDs are
     supported.
‘Floppy’
     You can specify a floppy device even if no floppy is loaded.
     Floppy removal is currently not detected accurately (if you change
     floppy without doing floppy access while the floppy is not loaded,
     the guest OS will think that the same floppy is loaded).  Use of
     the host’s floppy device is deprecated, and support for it will be
     removed in a future release.
‘Hard disks’
     Hard disks can be used.  Normally you must specify the whole disk
     (‘/dev/hdb’ instead of ‘/dev/hdb1’) so that the guest OS can see it
     as a partitioned disk.  WARNING: unless you know what you do, it is
     better to only make READ-ONLY accesses to the hard disk otherwise
     you may corrupt your host data (use the ‘-snapshot’ command line
     option or modify the device permissions accordingly).

2.8.7.2 Windows
...............

‘CD’
     The preferred syntax is the drive letter (e.g.  ‘d:’).  The
     alternate syntax ‘\\.\d:’ is supported.  ‘/dev/cdrom’ is supported
     as an alias to the first CDROM drive.

     Currently there is no specific code to handle removable media, so
     it is better to use the ‘change’ or ‘eject’ monitor commands to
     change or eject media.
‘Hard disks’
     Hard disks can be used with the syntax: ‘\\.\PhysicalDriveN’ where
     N is the drive number (0 is the first hard disk).

     WARNING: unless you know what you do, it is better to only make
     READ-ONLY accesses to the hard disk otherwise you may corrupt your
     host data (use the ‘-snapshot’ command line so that the
     modifications are written in a temporary file).

2.8.7.3 Mac OS X
................

‘/dev/cdrom’ is an alias to the first CDROM.

Currently there is no specific code to handle removable media, so it is
better to use the ‘change’ or ‘eject’ monitor commands to change or
eject media.

2.8.8 Virtual FAT disk images
-----------------------------

QEMU can automatically create a virtual FAT disk image from a directory
tree.  In order to use it, just type:

     qemu-kvm linux.img -hdb fat:/my_directory

Then you access access to all the files in the ‘/my_directory’ directory
without having to copy them in a disk image or to export them via SAMBA
or NFS. The default access is _read-only_.

Floppies can be emulated with the ‘:floppy:’ option:

     qemu-kvm linux.img -fda fat:floppy:/my_directory

A read/write support is available for testing (beta stage) with the
‘:rw:’ option:

     qemu-kvm linux.img -fda fat:floppy:rw:/my_directory

What you should _never_ do:
   • use non-ASCII filenames ;
   • use "-snapshot" together with ":rw:" ;
   • expect it to work when loadvm’ing ;
   • write to the FAT directory on the host system while accessing it
     with the guest system.

2.8.9 NBD access
----------------

QEMU can access directly to block device exported using the Network
Block Device protocol.

     qemu-kvm linux.img -hdb nbd://my_nbd_server.mydomain.org:1024/

If the NBD server is located on the same host, you can use an unix
socket instead of an inet socket:

     qemu-kvm linux.img -hdb nbd+unix://?socket=/tmp/my_socket

In this case, the block device must be exported using qemu-nbd:

     qemu-nbd --socket=/tmp/my_socket my_disk.qcow2

The use of qemu-nbd allows sharing of a disk between several guests:
     qemu-nbd --socket=/tmp/my_socket --share=2 my_disk.qcow2

and then you can use it with two guests:
     qemu-kvm linux1.img -hdb nbd+unix://?socket=/tmp/my_socket
     qemu-kvm linux2.img -hdb nbd+unix://?socket=/tmp/my_socket

If the nbd-server uses named exports (supported since NBD 2.9.18, or
with QEMU’s own embedded NBD server), you must specify an export name in
the URI:
     qemu-kvm -cdrom nbd://localhost/debian-500-ppc-netinst
     qemu-kvm -cdrom nbd://localhost/openSUSE-11.1-ppc-netinst

The URI syntax for NBD is supported since QEMU 1.3.  An alternative
syntax is also available.  Here are some example of the older syntax:
     qemu-kvm linux.img -hdb nbd:my_nbd_server.mydomain.org:1024
     qemu-kvm linux2.img -hdb nbd:unix:/tmp/my_socket
     qemu-kvm -cdrom nbd:localhost:10809:exportname=debian-500-ppc-netinst

2.8.10 Sheepdog disk images
---------------------------

Sheepdog is a distributed storage system for QEMU. It provides highly
available block level storage volumes that can be attached to QEMU-based
virtual machines.

You can create a Sheepdog disk image with the command:
     qemu-img create sheepdog:///IMAGE SIZE
where IMAGE is the Sheepdog image name and SIZE is its size.

To import the existing FILENAME to Sheepdog, you can use a convert
command.
     qemu-img convert FILENAME sheepdog:///IMAGE

You can boot from the Sheepdog disk image with the command:
     qemu-kvm sheepdog:///IMAGE

You can also create a snapshot of the Sheepdog image like qcow2.
     qemu-img snapshot -c TAG sheepdog:///IMAGE
where TAG is a tag name of the newly created snapshot.

To boot from the Sheepdog snapshot, specify the tag name of the
snapshot.
     qemu-kvm sheepdog:///IMAGE#TAG

You can create a cloned image from the existing snapshot.
     qemu-img create -b sheepdog:///BASE#TAG sheepdog:///IMAGE
where BASE is an image name of the source snapshot and TAG is its tag
name.

You can use an unix socket instead of an inet socket:

     qemu-kvm sheepdog+unix:///IMAGE?socket=PATH

If the Sheepdog daemon doesn’t run on the local host, you need to
specify one of the Sheepdog servers to connect to.
     qemu-img create sheepdog://HOSTNAME:PORT/IMAGE SIZE
     qemu-kvm sheepdog://HOSTNAME:PORT/IMAGE

2.8.11 iSCSI LUNs
-----------------

iSCSI is a popular protocol used to access SCSI devices across a
computer network.

There are two different ways iSCSI devices can be used by QEMU.

The first method is to mount the iSCSI LUN on the host, and make it
appear as any other ordinary SCSI device on the host and then to access
this device as a /dev/sd device from QEMU. How to do this differs
between host OSes.

The second method involves using the iSCSI initiator that is built into
QEMU. This provides a mechanism that works the same way regardless of
which host OS you are running QEMU on.  This section will describe this
second method of using iSCSI together with QEMU.

In QEMU, iSCSI devices are described using special iSCSI URLs

     URL syntax:
     iscsi://[<username>[%<password>]@]<host>[:<port>]/<target-iqn-name>/<lun>

Username and password are optional and only used if your target is set
up using CHAP authentication for access control.  Alternatively the
username and password can also be set via environment variables to have
these not show up in the process list

     export LIBISCSI_CHAP_USERNAME=<username>
     export LIBISCSI_CHAP_PASSWORD=<password>
     iscsi://<host>/<target-iqn-name>/<lun>

Various session related parameters can be set via special options,
either in a configuration file provided via ’-readconfig’ or directly on
the command line.

If the initiator-name is not specified qemu will use a default name of
’iqn.2008-11.org.linux-kvm[:<uuid>’] where <uuid> is the UUID of the
virtual machine.  If the UUID is not specified qemu will use
’iqn.2008-11.org.linux-kvm[:<name>’] where <name> is the name of the
virtual machine.

     Setting a specific initiator name to use when logging in to the target
     -iscsi initiator-name=iqn.qemu.test:my-initiator

     Controlling which type of header digest to negotiate with the target
     -iscsi header-digest=CRC32C|CRC32C-NONE|NONE-CRC32C|NONE

These can also be set via a configuration file
     [iscsi]
       user = "CHAP username"
       password = "CHAP password"
       initiator-name = "iqn.qemu.test:my-initiator"
       # header digest is one of CRC32C|CRC32C-NONE|NONE-CRC32C|NONE
       header-digest = "CRC32C"

Setting the target name allows different options for different targets
     [iscsi "iqn.target.name"]
       user = "CHAP username"
       password = "CHAP password"
       initiator-name = "iqn.qemu.test:my-initiator"
       # header digest is one of CRC32C|CRC32C-NONE|NONE-CRC32C|NONE
       header-digest = "CRC32C"

Howto use a configuration file to set iSCSI configuration options:
     cat >iscsi.conf <<EOF
     [iscsi]
       user = "me"
       password = "my password"
       initiator-name = "iqn.qemu.test:my-initiator"
       header-digest = "CRC32C"
     EOF

     qemu-kvm -drive file=iscsi://127.0.0.1/iqn.qemu.test/1 \
         -readconfig iscsi.conf

How to set up a simple iSCSI target on loopback and access it via QEMU:
     This example shows how to set up an iSCSI target with one CDROM and one DISK
     using the Linux STGT software target. This target is available on Red Hat based
     systems as the package 'scsi-target-utils'.

     tgtd --iscsi portal=127.0.0.1:3260
     tgtadm --lld iscsi --op new --mode target --tid 1 -T iqn.qemu.test
     tgtadm --lld iscsi --mode logicalunit --op new --tid 1 --lun 1 \
         -b /IMAGES/disk.img --device-type=disk
     tgtadm --lld iscsi --mode logicalunit --op new --tid 1 --lun 2 \
         -b /IMAGES/cd.iso --device-type=cd
     tgtadm --lld iscsi --op bind --mode target --tid 1 -I ALL

     qemu-kvm -iscsi initiator-name=iqn.qemu.test:my-initiator \
         -boot d -drive file=iscsi://127.0.0.1/iqn.qemu.test/1 \
         -cdrom iscsi://127.0.0.1/iqn.qemu.test/2

2.8.12 GlusterFS disk images
----------------------------

GlusterFS is a user space distributed file system.

You can boot from the GlusterFS disk image with the command:
     URI:
     qemu-kvm -drive file=gluster[+TYPE]://[HOST[:PORT]]/VOLUME/PATH
                                    [?socket=...][,file.debug=9][,file.logfile=...]

     JSON:
     qemu-kvm 'json:{"driver":"qcow2",
                                "file":{"driver":"gluster",
                                         "volume":"testvol","path":"a.img","debug":9,"logfile":"...",
                                         "server":[{"type":"tcp","host":"...","port":"..."},
                                                   {"type":"unix","socket":"..."}]}}'

GLUSTER is the protocol.

TYPE specifies the transport type used to connect to gluster management
daemon (glusterd).  Valid transport types are tcp and unix.  In the URI
form, if a transport type isn’t specified, then tcp type is assumed.

HOST specifies the server where the volume file specification for the
given volume resides.  This can be either a hostname or an ipv4 address.
If transport type is unix, then HOST field should not be specified.
Instead SOCKET field needs to be populated with the path to unix domain
socket.

PORT is the port number on which glusterd is listening.  This is
optional and if not specified, it defaults to port 24007.  If the
transport type is unix, then PORT should not be specified.

VOLUME is the name of the gluster volume which contains the disk image.

PATH is the path to the actual disk image that resides on gluster
volume.

DEBUG is the logging level of the gluster protocol driver.  Debug levels
are 0-9, with 9 being the most verbose, and 0 representing no debugging
output.  The default level is 4.  The current logging levels defined in
the gluster source are 0 - None, 1 - Emergency, 2 - Alert, 3 - Critical,
4 - Error, 5 - Warning, 6 - Notice, 7 - Info, 8 - Debug, 9 - Trace

LOGFILE is a commandline option to mention log file path which helps in
logging to the specified file and also help in persisting the gfapi
logs.  The default is stderr.

You can create a GlusterFS disk image with the command:
     qemu-img create gluster://HOST/VOLUME/PATH SIZE

Examples
     qemu-kvm -drive file=gluster://1.2.3.4/testvol/a.img
     qemu-kvm -drive file=gluster+tcp://1.2.3.4/testvol/a.img
     qemu-kvm -drive file=gluster+tcp://1.2.3.4:24007/testvol/dir/a.img
     qemu-kvm -drive file=gluster+tcp://[1:2:3:4:5:6:7:8]/testvol/dir/a.img
     qemu-kvm -drive file=gluster+tcp://[1:2:3:4:5:6:7:8]:24007/testvol/dir/a.img
     qemu-kvm -drive file=gluster+tcp://server.domain.com:24007/testvol/dir/a.img
     qemu-kvm -drive file=gluster+unix:///testvol/dir/a.img?socket=/tmp/glusterd.socket
     qemu-kvm -drive file=gluster+rdma://1.2.3.4:24007/testvol/a.img
     qemu-kvm -drive file=gluster://1.2.3.4/testvol/a.img,file.debug=9,file.logfile=/var/log/qemu-gluster.log
     qemu-kvm 'json:{"driver":"qcow2",
                                "file":{"driver":"gluster",
                                         "volume":"testvol","path":"a.img",
                                         "debug":9,"logfile":"/var/log/qemu-gluster.log",
                                         "server":[{"type":"tcp","host":"1.2.3.4","port":24007},
                                                   {"type":"unix","socket":"/var/run/glusterd.socket"}]}}'
     qemu-kvm -drive driver=qcow2,file.driver=gluster,file.volume=testvol,file.path=/path/a.img,
                                            file.debug=9,file.logfile=/var/log/qemu-gluster.log,
                                            file.server.0.type=tcp,file.server.0.host=1.2.3.4,file.server.0.port=24007,
                                            file.server.1.type=unix,file.server.1.socket=/var/run/glusterd.socket

2.8.13 Secure Shell (ssh) disk images
-------------------------------------

You can access disk images located on a remote ssh server by using the
ssh protocol:

     qemu-kvm -drive file=ssh://[USER@]SERVER[:PORT]/PATH[?host_key_check=HOST_KEY_CHECK]

Alternative syntax using properties:

     qemu-kvm -drive file.driver=ssh[,file.user=USER],file.host=SERVER[,file.port=PORT],file.path=PATH[,file.host_key_check=HOST_KEY_CHECK]

SSH is the protocol.

USER is the remote user.  If not specified, then the local username is
tried.

SERVER specifies the remote ssh server.  Any ssh server can be used, but
it must implement the sftp-server protocol.  Most Unix/Linux systems
should work without requiring any extra configuration.

PORT is the port number on which sshd is listening.  By default the
standard ssh port (22) is used.

PATH is the path to the disk image.

The optional HOST_KEY_CHECK parameter controls how the remote host’s key
is checked.  The default is ‘yes’ which means to use the local
‘.ssh/known_hosts’ file.  Setting this to ‘no’ turns off known-hosts
checking.  Or you can check that the host key matches a specific
fingerprint:
‘host_key_check=md5:78:45:8e:14:57:4f:d5:45:83:0a:0e:f3:49:82:c9:c8’
(‘sha1:’ can also be used as a prefix, but note that OpenSSH tools only
use MD5 to print fingerprints).

Currently authentication must be done using ssh-agent.  Other
authentication methods may be supported in future.

Note: Many ssh servers do not support an ‘fsync’-style operation.  The
ssh driver cannot guarantee that disk flush requests are obeyed, and
this causes a risk of disk corruption if the remote server or network
goes down during writes.  The driver will print a warning when ‘fsync’
is not supported:

warning: ssh server ‘ssh.example.com:22’ does not support fsync

With sufficiently new versions of libssh and OpenSSH, ‘fsync’ is
supported.

2.8.14 NVMe disk images
-----------------------

NVM Express (NVMe) storage controllers can be accessed directly by a
userspace driver in QEMU. This bypasses the host kernel file system and
block layers while retaining QEMU block layer functionalities, such as
block jobs, I/O throttling, image formats, etc.  Disk I/O performance is
typically higher than with ‘-drive file=/dev/sda’ using either thread
pool or linux-aio.

The controller will be exclusively used by the QEMU process once
started.  To be able to share storage between multiple VMs and other
applications on the host, please use the file based protocols.

Before starting QEMU, bind the host NVMe controller to the host vfio-pci
driver.  For example:

     # modprobe vfio-pci
     # lspci -n -s 0000:06:0d.0
     06:0d.0 0401: 1102:0002 (rev 08)
     # echo 0000:06:0d.0 > /sys/bus/pci/devices/0000:06:0d.0/driver/unbind
     # echo 1102 0002 > /sys/bus/pci/drivers/vfio-pci/new_id

     # qemu-kvm -drive file=nvme://HOST:BUS:SLOT.FUNC/NAMESPACE

Alternative syntax using properties:

     qemu-kvm -drive file.driver=nvme,file.device=HOST:BUS:SLOT.FUNC,file.namespace=NAMESPACE

HOST:BUS:SLOT.FUNC is the NVMe controller’s PCI device address on the
host.

NAMESPACE is the NVMe namespace number, starting from 1.

2.8.15 Disk image file locking
------------------------------

By default, QEMU tries to protect image files from unexpected concurrent
access, as long as it’s supported by the block protocol driver and host
operating system.  If multiple QEMU processes (including QEMU emulators
and utilities) try to open the same image with conflicting accessing
modes, all but the first one will get an error.

This feature is currently supported by the file protocol on Linux with
the Open File Descriptor (OFD) locking API, and can be configured to
fall back to POSIX locking if the POSIX host doesn’t support Linux OFD
locking.

To explicitly enable image locking, specify "locking=on" in the file
protocol driver options.  If OFD locking is not possible, a warning will
be printed and the POSIX locking API will be used.  In this case there
is a risk that the lock will get silently lost when doing hot plugging
and block jobs, due to the shortcomings of the POSIX locking API.

QEMU transparently handles lock handover during shared storage
migration.  For shared virtual disk images between multiple VMs, the
"share-rw" device option should be used.

By default, the guest has exclusive write access to its disk image.  If
the guest can safely share the disk image with other writers the
‘-device ...,share-rw=on’ parameter can be used.  This is only safe if
the guest is running software, such as a cluster file system, that
coordinates disk accesses to avoid corruption.

Note that share-rw=on only declares the guest’s ability to share the
disk.  Some QEMU features, such as image file formats, require exclusive
write access to the disk image and this is unaffected by the share-rw=on
option.

Alternatively, locking can be fully disabled by "locking=off" block
device option.  In the command line, the option is usually in the form
of "file.locking=off" as the protocol driver is normally placed as a
"file" child under a format driver.  For example:

‘-blockdev
driver=qcow2,file.filename=/path/to/image,file.locking=off,file.driver=file’

To check if image locking is active, check the output of the "lslocks"
command on host and see if there are locks held by the QEMU process on
the image file.  More than one byte could be locked by the QEMU
instance, each byte of which reflects a particular permission that is
acquired or protected by the running block driver.

2.9 Network emulation
=====================

QEMU can simulate several network cards (e.g.  PCI or ISA cards on the
PC target) and can connect them to a network backend on the host or an
emulated hub.  The various host network backends can either be used to
connect the NIC of the guest to a real network (e.g.  by using a TAP
devices or the non-privileged user mode network stack), or to other
guest instances running in another QEMU process (e.g.  by using the
socket host network backend).

2.9.1 Using TAP network interfaces
----------------------------------

This is the standard way to connect QEMU to a real network.  QEMU adds a
virtual network device on your host (called ‘tapN’), and you can then
configure it as if it was a real ethernet card.

2.9.1.1 Linux host
..................

As an example, you can download the ‘linux-test-xxx.tar.gz’ archive and
copy the script ‘qemu-ifup’ in ‘/etc’ and configure properly ‘sudo’ so
that the command ‘ifconfig’ contained in ‘qemu-ifup’ can be executed as
root.  You must verify that your host kernel supports the TAP network
interfaces: the device ‘/dev/net/tun’ must be present.

See *note sec_invocation:: to have examples of command lines using the
TAP network interfaces.

2.9.1.2 Windows host
....................

There is a virtual ethernet driver for Windows 2000/XP systems, called
TAP-Win32.  But it is not included in standard QEMU for Windows, so you
will need to get it separately.  It is part of OpenVPN package, so
download OpenVPN from : <https://openvpn.net/>.

2.9.2 Using the user mode network stack
---------------------------------------

By using the option ‘-net user’ (default configuration if no ‘-net’
option is specified), QEMU uses a completely user mode network stack
(you don’t need root privilege to use the virtual network).  The virtual
network configuration is the following:


          guest (10.0.2.15)  <------>  Firewall/DHCP server <-----> Internet
                                |          (10.0.2.2)
                                |
                                ---->  DNS server (10.0.2.3)
                                |
                                ---->  SMB server (10.0.2.4)

The QEMU VM behaves as if it was behind a firewall which blocks all
incoming connections.  You can use a DHCP client to automatically
configure the network in the QEMU VM. The DHCP server assign addresses
to the hosts starting from 10.0.2.15.

In order to check that the user mode network is working, you can ping
the address 10.0.2.2 and verify that you got an address in the range
10.0.2.x from the QEMU virtual DHCP server.

Note that ICMP traffic in general does not work with user mode
networking.  ‘ping’, aka.  ICMP echo, to the local router (10.0.2.2)
shall work, however.  If you’re using QEMU on Linux >= 3.0, it can use
unprivileged ICMP ping sockets to allow ‘ping’ to the Internet.  The
host admin has to set the ping_group_range in order to grant access to
those sockets.  To allow ping for GID 100 (usually users group):

     echo 100 100 > /proc/sys/net/ipv4/ping_group_range

When using the built-in TFTP server, the router is also the TFTP server.

When using the ‘'-netdev user,hostfwd=...'’ option, TCP or UDP
connections can be redirected from the host to the guest.  It allows for
example to redirect X11, telnet or SSH connections.

2.9.3 Hubs
----------

QEMU can simulate several hubs.  A hub can be thought of as a virtual
connection between several network devices.  These devices can be for
example QEMU virtual ethernet cards or virtual Host ethernet devices
(TAP devices).  You can connect guest NICs or host network backends to
such a hub using the ‘-netdev hubport’ or ‘-nic hubport’ options.  The
legacy ‘-net’ option also connects the given device to the emulated hub
with ID 0 (i.e.  the default hub) unless you specify a netdev with ‘-net
nic,netdev=xxx’ here.

2.9.4 Connecting emulated networks between QEMU instances
---------------------------------------------------------

Using the ‘-netdev socket’ (or ‘-nic socket’ or ‘-net socket’) option,
it is possible to create emulated networks that span several QEMU
instances.  See the description of the ‘-netdev socket’ option in the
*note Invocation chapter: sec_invocation. to have a basic example.

2.10 Other Devices
==================

2.10.1 Inter-VM Shared Memory device
------------------------------------

On Linux hosts, a shared memory device is available.  The basic syntax
is:

     qemu-kvm -device ivshmem-plain,memdev=HOSTMEM

where HOSTMEM names a host memory backend.  For a POSIX shared memory
backend, use something like

     -object memory-backend-file,size=1M,share,mem-path=/dev/shm/ivshmem,id=HOSTMEM

If desired, interrupts can be sent between guest VMs accessing the same
shared memory region.  Interrupt support requires using a shared memory
server and using a chardev socket to connect to it.  The code for the
shared memory server is qemu.git/contrib/ivshmem-server.  An example
syntax when using the shared memory server is:

     # First start the ivshmem server once and for all
     ivshmem-server -p PIDFILE -S PATH -m SHM-NAME -l SHM-SIZE -n VECTORS

     # Then start your qemu instances with matching arguments
     qemu-kvm -device ivshmem-doorbell,vectors=VECTORS,chardev=ID
                      -chardev socket,path=PATH,id=ID

When using the server, the guest will be assigned a VM ID (>=0) that
allows guests using the same server to communicate via interrupts.
Guests can read their VM ID from a device register (see
ivshmem-spec.txt).

2.10.1.1 Migration with ivshmem
...............................

With device property ‘master=on’, the guest will copy the shared memory
on migration to the destination host.  With ‘master=off’, the guest will
not be able to migrate with the device attached.  In the latter case,
the device should be detached and then reattached after migration using
the PCI hotplug support.

At most one of the devices sharing the same memory can be master.  The
master must complete migration before you plug back the other devices.

2.10.1.2 ivshmem and hugepages
..............................

Instead of specifying the <shm size> using POSIX shm, you may specify a
memory backend that has hugepage support:

     qemu-kvm -object memory-backend-file,size=1G,mem-path=/dev/hugepages/my-shmem-file,share,id=mb1
                      -device ivshmem-plain,memdev=mb1

ivshmem-server also supports hugepages mount points with the ‘-m’ memory
path argument.

2.11 Direct Linux Boot
======================

This section explains how to launch a Linux kernel inside QEMU without
having to make a full bootable image.  It is very useful for fast Linux
kernel testing.

The syntax is:
     qemu-kvm -kernel bzImage -hda rootdisk.img -append "root=/dev/hda"

Use ‘-kernel’ to provide the Linux kernel image and ‘-append’ to give
the kernel command line arguments.  The ‘-initrd’ option can be used to
provide an INITRD image.

If you do not need graphical output, you can disable it and redirect the
virtual serial port and the QEMU monitor to the console with the
‘-nographic’ option.  The typical command line is:
     qemu-kvm -kernel bzImage -hda rootdisk.img \
                      -append "root=/dev/hda console=ttyS0" -nographic

Use <Ctrl-a c> to switch between the serial console and the monitor
(*note pcsys_keys::).

2.12 USB emulation
==================

QEMU can emulate a PCI UHCI, OHCI, EHCI or XHCI USB controller.  You can
plug virtual USB devices or real host USB devices (only works with
certain host operating systems).  QEMU will automatically create and
connect virtual USB hubs as necessary to connect multiple USB devices.

2.12.1 Connecting USB devices
-----------------------------

USB devices can be connected with the ‘-device usb-...’ command line
option or the ‘device_add’ monitor command.  Available devices are:

‘usb-mouse’
     Virtual Mouse.  This will override the PS/2 mouse emulation when
     activated.
‘usb-tablet’
     Pointer device that uses absolute coordinates (like a touchscreen).
     This means QEMU is able to report the mouse position without having
     to grab the mouse.  Also overrides the PS/2 mouse emulation when
     activated.
‘usb-storage,drive=DRIVE_ID’
     Mass storage device backed by DRIVE_ID (*note disk_images::)
‘usb-uas’
     USB attached SCSI device, see usb-storage.txt
     (https://git.qemu.org/?p=qemu.git;a=blob_plain;f=docs/usb-storage.txt)
     for details
‘usb-bot’
     Bulk-only transport storage device, see usb-storage.txt
     (https://git.qemu.org/?p=qemu.git;a=blob_plain;f=docs/usb-storage.txt)
     for details here, too
‘usb-mtp,rootdir=DIR’
     Media transfer protocol device, using DIR as root of the file tree
     that is presented to the guest.
‘usb-host,hostbus=BUS,hostaddr=ADDR’
     Pass through the host device identified by BUS and ADDR
‘usb-host,vendorid=VENDOR,productid=PRODUCT’
     Pass through the host device identified by VENDOR and PRODUCT ID
‘usb-wacom-tablet’
     Virtual Wacom PenPartner tablet.  This device is similar to the
     ‘tablet’ above but it can be used with the tslib library because in
     addition to touch coordinates it reports touch pressure.
‘usb-kbd’
     Standard USB keyboard.  Will override the PS/2 keyboard (if
     present).
‘usb-serial,chardev=ID’
     Serial converter.  This emulates an FTDI FT232BM chip connected to
     host character device ID.
‘usb-braille,chardev=ID’
     Braille device.  This will use BrlAPI to display the braille output
     on a real or fake device referenced by ID.
‘usb-net[,netdev=ID]’
     Network adapter that supports CDC ethernet and RNDIS protocols.  ID
     specifies a netdev defined with ‘-netdev ...,id=ID’.  For instance,
     user-mode networking can be used with
          qemu-kvm [...] -netdev user,id=net0 -device usb-net,netdev=net0
‘usb-ccid’
     Smartcard reader device
‘usb-audio’
     USB audio device
‘usb-bt-dongle’
     Bluetooth dongle for the transport layer of HCI. It is connected to
     HCI scatternet 0 by default (corresponds to ‘-bt hci,vlan=0’).
     Note that the syntax for the ‘-device usb-bt-dongle’ option is not
     as useful yet as it was with the legacy ‘-usbdevice’ option.  So to
     configure an USB bluetooth device, you might need to use
     "‘-usbdevice bt’[:HCI-TYPE]" instead.  This configures a bluetooth
     dongle whose type is specified in the same format as with the ‘-bt
     hci’ option, *note allowed HCI types: bt-hcis.  If no type is
     given, the HCI logic corresponds to ‘-bt hci,vlan=0’.  This USB
     device implements the USB Transport Layer of HCI. Example usage:
          qemu-kvm [...OPTIONS...] -usbdevice bt:hci,vlan=3 -bt device:keyboard,vlan=3

2.12.2 Using host USB devices on a Linux host
---------------------------------------------

WARNING: this is an experimental feature.  QEMU will slow down when
using it.  USB devices requiring real time streaming (i.e.  USB Video
Cameras) are not supported yet.

  1. If you use an early Linux 2.4 kernel, verify that no Linux driver
     is actually using the USB device.  A simple way to do that is
     simply to disable the corresponding kernel module by renaming it
     from ‘mydriver.o’ to ‘mydriver.o.disabled’.

  2. Verify that ‘/proc/bus/usb’ is working (most Linux distributions
     should enable it by default).  You should see something like that:
          ls /proc/bus/usb
          001  devices  drivers

  3. Since only root can access to the USB devices directly, you can
     either launch QEMU as root or change the permissions of the USB
     devices you want to use.  For testing, the following suffices:
          chown -R myuid /proc/bus/usb

  4. Launch QEMU and do in the monitor:
          info usbhost
            Device 1.2, speed 480 Mb/s
              Class 00: USB device 1234:5678, USB DISK
     You should see the list of the devices you can use (Never try to
     use hubs, it won’t work).

  5. Add the device in QEMU by using:
          device_add usb-host,vendorid=0x1234,productid=0x5678

     Normally the guest OS should report that a new USB device is
     plugged.  You can use the option ‘-device usb-host,...’ to do the
     same.

  6. Now you can try to use the host USB device in QEMU.

When relaunching QEMU, you may have to unplug and plug again the USB
device to make it work again (this is a bug).

2.13 VNC security
=================

The VNC server capability provides access to the graphical console of
the guest VM across the network.  This has a number of security
considerations depending on the deployment scenarios.

2.13.1 Without passwords
------------------------

The simplest VNC server setup does not include any form of
authentication.  For this setup it is recommended to restrict it to
listen on a UNIX domain socket only.  For example

     qemu-kvm [...OPTIONS...] -vnc unix:/home/joebloggs/.qemu-myvm-vnc

This ensures that only users on local box with read/write access to that
path can access the VNC server.  To securely access the VNC server from
a remote machine, a combination of netcat+ssh can be used to provide a
secure tunnel.

2.13.2 With passwords
---------------------

The VNC protocol has limited support for password based authentication.
Since the protocol limits passwords to 8 characters it should not be
considered to provide high security.  The password can be fairly easily
brute-forced by a client making repeat connections.  For this reason, a
VNC server using password authentication should be restricted to only
listen on the loopback interface or UNIX domain sockets.  Password
authentication is not supported when operating in FIPS 140-2 compliance
mode as it requires the use of the DES cipher.  Password authentication
is requested with the ‘password’ option, and then once QEMU is running
the password is set with the monitor.  Until the monitor is used to set
the password all clients will be rejected.

     qemu-kvm [...OPTIONS...] -vnc :1,password -monitor stdio
     (qemu) change vnc password
     Password: ********
     (qemu)

2.13.3 With x509 certificates
-----------------------------

The QEMU VNC server also implements the VeNCrypt extension allowing use
of TLS for encryption of the session, and x509 certificates for
authentication.  The use of x509 certificates is strongly recommended,
because TLS on its own is susceptible to man-in-the-middle attacks.
Basic x509 certificate support provides a secure session, but no
authentication.  This allows any client to connect, and provides an
encrypted session.

     qemu-kvm [...OPTIONS...] \
       -object tls-creds-x509,id=tls0,dir=/etc/pki/qemu,endpoint=server,verify-peer=no \
       -vnc :1,tls-creds=tls0 -monitor stdio

In the above example ‘/etc/pki/qemu’ should contain at least three
files, ‘ca-cert.pem’, ‘server-cert.pem’ and ‘server-key.pem’.
Unprivileged users will want to use a private directory, for example
‘$HOME/.pki/qemu’.  NB the ‘server-key.pem’ file should be protected
with file mode 0600 to only be readable by the user owning it.

2.13.4 With x509 certificates and client verification
-----------------------------------------------------

Certificates can also provide a means to authenticate the client
connecting.  The server will request that the client provide a
certificate, which it will then validate against the CA certificate.
This is a good choice if deploying in an environment with a private
internal certificate authority.  It uses the same syntax as previously,
but with ‘verify-peer’ set to ‘yes’ instead.

     qemu-kvm [...OPTIONS...] \
       -object tls-creds-x509,id=tls0,dir=/etc/pki/qemu,endpoint=server,verify-peer=yes \
       -vnc :1,tls-creds=tls0 -monitor stdio

2.13.5 With x509 certificates, client verification and passwords
----------------------------------------------------------------

Finally, the previous method can be combined with VNC password
authentication to provide two layers of authentication for clients.

     qemu-kvm [...OPTIONS...] \
       -object tls-creds-x509,id=tls0,dir=/etc/pki/qemu,endpoint=server,verify-peer=yes \
       -vnc :1,tls-creds=tls0,password -monitor stdio
     (qemu) change vnc password
     Password: ********
     (qemu)

2.13.6 With SASL authentication
-------------------------------

The SASL authentication method is a VNC extension, that provides an
easily extendable, pluggable authentication method.  This allows for
integration with a wide range of authentication mechanisms, such as PAM,
GSSAPI/Kerberos, LDAP, SQL databases, one-time keys and more.  The
strength of the authentication depends on the exact mechanism
configured.  If the chosen mechanism also provides a SSF layer, then it
will encrypt the datastream as well.

Refer to the later docs on how to choose the exact SASL mechanism used
for authentication, but assuming use of one supporting SSF, then QEMU
can be launched with:

     qemu-kvm [...OPTIONS...] -vnc :1,sasl -monitor stdio

2.13.7 With x509 certificates and SASL authentication
-----------------------------------------------------

If the desired SASL authentication mechanism does not supported SSF
layers, then it is strongly advised to run it in combination with TLS
and x509 certificates.  This provides securely encrypted data stream,
avoiding risk of compromising of the security credentials.  This can be
enabled, by combining the ’sasl’ option with the aforementioned TLS +
x509 options:

     qemu-kvm [...OPTIONS...] \
       -object tls-creds-x509,id=tls0,dir=/etc/pki/qemu,endpoint=server,verify-peer=yes \
       -vnc :1,tls-creds=tls0,sasl -monitor stdio

2.13.8 Configuring SASL mechanisms
----------------------------------

The following documentation assumes use of the Cyrus SASL implementation
on a Linux host, but the principles should apply to any other SASL
implementation or host.  When SASL is enabled, the mechanism
configuration will be loaded from system default SASL service config
/etc/sasl2/qemu.conf.  If running QEMU as an unprivileged user, an
environment variable SASL_CONF_PATH can be used to make it search
alternate locations for the service config file.

If the TLS option is enabled for VNC, then it will provide session
encryption, otherwise the SASL mechanism will have to provide
encryption.  In the latter case the list of possible plugins that can be
used is drastically reduced.  In fact only the GSSAPI SASL mechanism
provides an acceptable level of security by modern standards.  Previous
versions of QEMU referred to the DIGEST-MD5 mechanism, however, it has
multiple serious flaws described in detail in RFC 6331 and thus should
never be used any more.  The SCRAM-SHA-1 mechanism provides a simple
username/password auth facility similar to DIGEST-MD5, but does not
support session encryption, so can only be used in combination with TLS.

When not using TLS the recommended configuration is

     mech_list: gssapi
     keytab: /etc/qemu/krb5.tab

This says to use the ’GSSAPI’ mechanism with the Kerberos v5 protocol,
with the server principal stored in /etc/qemu/krb5.tab.  For this to
work the administrator of your KDC must generate a Kerberos principal
for the server, with a name of ’qemu/somehost.example.com@EXAMPLE.COM’
replacing ’somehost.example.com’ with the fully qualified host name of
the machine running QEMU, and ’EXAMPLE.COM’ with the Kerberos Realm.

When using TLS, if username+password authentication is desired, then a
reasonable configuration is

     mech_list: scram-sha-1
     sasldb_path: /etc/qemu/passwd.db

The ‘saslpasswd2’ program can be used to populate the ‘passwd.db’ file
with accounts.

Other SASL configurations will be left as an exercise for the reader.
Note that all mechanisms, except GSSAPI, should be combined with use of
TLS to ensure a secure data channel.

2.14 TLS setup for network services
===================================

Almost all network services in QEMU have the ability to use TLS for
session data encryption, along with x509 certificates for simple client
authentication.  What follows is a description of how to generate
certificates suitable for usage with QEMU, and applies to the VNC
server, character devices with the TCP backend, NBD server and client,
and migration server and client.

At a high level, QEMU requires certificates and private keys to be
provided in PEM format.  Aside from the core fields, the certificates
should include various extension data sets, including v3 basic
constraints data, key purpose, key usage and subject alt name.

The GnuTLS package includes a command called ‘certtool’ which can be
used to easily generate certificates and keys in the required format
with expected data present.  Alternatively a certificate management
service may be used.

At a minimum it is necessary to setup a certificate authority, and issue
certificates to each server.  If using x509 certificates for
authentication, then each client will also need to be issued a
certificate.

Assuming that the QEMU network services will only ever be exposed to
clients on a private intranet, there is no need to use a commercial
certificate authority to create certificates.  A self-signed CA is
sufficient, and in fact likely to be more secure since it removes the
ability of malicious 3rd parties to trick the CA into mis-issuing certs
for impersonating your services.  The only likely exception where a
commercial CA might be desirable is if enabling the VNC websockets
server and exposing it directly to remote browser clients.  In such a
case it might be useful to use a commercial CA to avoid needing to
install custom CA certs in the web browsers.

The recommendation is for the server to keep its certificates in either
‘/etc/pki/qemu’ or for unprivileged users in ‘$HOME/.pki/qemu’.

2.14.1 Setup the Certificate Authority
--------------------------------------

This step only needs to be performed once per organization /
organizational unit.  First the CA needs a private key.  This key must
be kept VERY secret and secure.  If this key is compromised the entire
trust chain of the certificates issued with it is lost.

     # certtool --generate-privkey > ca-key.pem

To generate a self-signed certificate requires one core piece of
information, the name of the organization.  A template file ‘ca.info’
should be populated with the desired data to avoid having to deal with
interactive prompts from certtool:
     # cat > ca.info <<EOF
     cn = Name of your organization
     ca
     cert_signing_key
     EOF
     # certtool --generate-self-signed \
                --load-privkey ca-key.pem
                --template ca.info \
                --outfile ca-cert.pem

The ‘ca’ keyword in the template sets the v3 basic constraints extension
to indicate this certificate is for a CA, while ‘cert_signing_key’ sets
the key usage extension to indicate this will be used for signing other
keys.  The generated ‘ca-cert.pem’ file should be copied to all servers
and clients wishing to utilize TLS support in the VNC server.  The
‘ca-key.pem’ must not be disclosed/copied anywhere except the host
responsible for issuing certificates.

2.14.2 Issuing server certificates
----------------------------------

Each server (or host) needs to be issued with a key and certificate.
When connecting the certificate is sent to the client which validates it
against the CA certificate.  The core pieces of information for a server
certificate are the hostnames and/or IP addresses that will be used by
clients when connecting.  The hostname / IP address that the client
specifies when connecting will be validated against the hostname(s) and
IP address(es) recorded in the server certificate, and if no match is
found the client will close the connection.

Thus it is recommended that the server certificate include both the
fully qualified and unqualified hostnames.  If the server will have
permanently assigned IP address(es), and clients are likely to use them
when connecting, they may also be included in the certificate.  Both
IPv4 and IPv6 addresses are supported.  Historically certificates only
included 1 hostname in the ‘CN’ field, however, usage of this field for
validation is now deprecated.  Instead modern TLS clients will validate
against the Subject Alt Name extension data, which allows for multiple
entries.  In the future usage of the ‘CN’ field may be discontinued
entirely, so providing SAN extension data is strongly recommended.

On the host holding the CA, create template files containing the
information for each server, and use it to issue server certificates.

     # cat > server-hostNNN.info <<EOF
     organization = Name  of your organization
     cn = hostNNN.foo.example.com
     dns_name = hostNNN
     dns_name = hostNNN.foo.example.com
     ip_address = 10.0.1.87
     ip_address = 192.8.0.92
     ip_address = 2620:0:cafe::87
     ip_address = 2001:24::92
     tls_www_server
     encryption_key
     signing_key
     EOF
     # certtool --generate-privkey > server-hostNNN-key.pem
     # certtool --generate-certificate \
                --load-ca-certificate ca-cert.pem \
                --load-ca-privkey ca-key.pem \
                --load-privkey server-hostNNN-key.pem \
                --template server-hostNNN.info \
                --outfile server-hostNNN-cert.pem

The ‘dns_name’ and ‘ip_address’ fields in the template are setting the
subject alt name extension data.  The ‘tls_www_server’ keyword is the
key purpose extension to indicate this certificate is intended for usage
in a web server.  Although QEMU network services are not in fact HTTP
servers (except for VNC websockets), setting this key purpose is still
recommended.  The ‘encryption_key’ and ‘signing_key’ keyword is the key
usage extension to indicate this certificate is intended for usage in
the data session.

The ‘server-hostNNN-key.pem’ and ‘server-hostNNN-cert.pem’ files should
now be securely copied to the server for which they were generated, and
renamed to ‘server-key.pem’ and ‘server-cert.pem’ when added to the
‘/etc/pki/qemu’ directory on the target host.  The ‘server-key.pem’ file
is security sensitive and should be kept protected with file mode 0600
to prevent disclosure.

2.14.3 Issuing client certificates
----------------------------------

The QEMU x509 TLS credential setup defaults to enabling client
verification using certificates, providing a simple authentication
mechanism.  If this default is used, each client also needs to be issued
a certificate.  The client certificate contains enough metadata to
uniquely identify the client with the scope of the certificate
authority.  The client certificate would typically include fields for
organization, state, city, building, etc.

Once again on the host holding the CA, create template files containing
the information for each client, and use it to issue client
certificates.

     # cat > client-hostNNN.info <<EOF
     country = GB
     state = London
     locality = City Of London
     organization = Name of your organization
     cn = hostNNN.foo.example.com
     tls_www_client
     encryption_key
     signing_key
     EOF
     # certtool --generate-privkey > client-hostNNN-key.pem
     # certtool --generate-certificate \
                --load-ca-certificate ca-cert.pem \
                --load-ca-privkey ca-key.pem \
                --load-privkey client-hostNNN-key.pem \
                --template client-hostNNN.info \
                --outfile client-hostNNN-cert.pem

The subject alt name extension data is not required for clients, so the
the ‘dns_name’ and ‘ip_address’ fields are not included.  The
‘tls_www_client’ keyword is the key purpose extension to indicate this
certificate is intended for usage in a web client.  Although QEMU
network clients are not in fact HTTP clients, setting this key purpose
is still recommended.  The ‘encryption_key’ and ‘signing_key’ keyword is
the key usage extension to indicate this certificate is intended for
usage in the data session.

The ‘client-hostNNN-key.pem’ and ‘client-hostNNN-cert.pem’ files should
now be securely copied to the client for which they were generated, and
renamed to ‘client-key.pem’ and ‘client-cert.pem’ when added to the
‘/etc/pki/qemu’ directory on the target host.  The ‘client-key.pem’ file
is security sensitive and should be kept protected with file mode 0600
to prevent disclosure.

If a single host is going to be using TLS in both a client and server
role, it is possible to create a single certificate to cover both roles.
This would be quite common for the migration and NBD services, where a
QEMU process will be started by accepting a TLS protected incoming
migration, and later itself be migrated out to another host.  To
generate a single certificate, simply include the template data from
both the client and server instructions in one.

     # cat > both-hostNNN.info <<EOF
     country = GB
     state = London
     locality = City Of London
     organization = Name of your organization
     cn = hostNNN.foo.example.com
     dns_name = hostNNN
     dns_name = hostNNN.foo.example.com
     ip_address = 10.0.1.87
     ip_address = 192.8.0.92
     ip_address = 2620:0:cafe::87
     ip_address = 2001:24::92
     tls_www_server
     tls_www_client
     encryption_key
     signing_key
     EOF
     # certtool --generate-privkey > both-hostNNN-key.pem
     # certtool --generate-certificate \
                --load-ca-certificate ca-cert.pem \
                --load-ca-privkey ca-key.pem \
                --load-privkey both-hostNNN-key.pem \
                --template both-hostNNN.info \
                --outfile both-hostNNN-cert.pem

When copying the PEM files to the target host, save them twice, once as
‘server-cert.pem’ and ‘server-key.pem’, and again as ‘client-cert.pem’
and ‘client-key.pem’.

2.14.4 TLS x509 credential configuration
----------------------------------------

QEMU has a standard mechanism for loading x509 credentials that will be
used for network services and clients.  It requires specifying the
‘tls-creds-x509’ class name to the ‘--object’ command line argument for
the system emulators.  Each set of credentials loaded should be given a
unique string identifier via the ‘id’ parameter.  A single set of TLS
credentials can be used for multiple network backends, so VNC,
migration, NBD, character devices can all share the same credentials.
Note, however, that credentials for use in a client endpoint must be
loaded separately from those used in a server endpoint.

When specifying the object, the ‘dir’ parameters specifies which
directory contains the credential files.  This directory is expected to
contain files with the names mentioned previously, ‘ca-cert.pem’,
‘server-key.pem’, ‘server-cert.pem’, ‘client-key.pem’ and
‘client-cert.pem’ as appropriate.  It is also possible to include a set
of pre-generated Diffie-Hellman (DH) parameters in a file
‘dh-params.pem’, which can be created using the ‘certtool
--generate-dh-params’ command.  If omitted, QEMU will dynamically
generate DH parameters when loading the credentials.

The ‘endpoint’ parameter indicates whether the credentials will be used
for a network client or server, and determines which PEM files are
loaded.

The ‘verify’ parameter determines whether x509 certificate validation
should be performed.  This defaults to enabled, meaning clients will
always validate the server hostname against the certificate subject alt
name fields and/or CN field.  It also means that servers will request
that clients provide a certificate and validate them.  Verification
should never be turned off for client endpoints, however, it may be
turned off for server endpoints if an alternative mechanism is used to
authenticate clients.  For example, the VNC server can use SASL to
authenticate clients instead.

To load server credentials with client certificate validation enabled

     qemu-kvm -object tls-creds-x509,id=tls0,dir=/etc/pki/qemu,endpoint=server

while to load client credentials use

     qemu-kvm -object tls-creds-x509,id=tls0,dir=/etc/pki/qemu,endpoint=client

Network services which support TLS will all have a ‘tls-creds’ parameter
which expects the ID of the TLS credentials object.  For example with
VNC:

     qemu-kvm -vnc 0.0.0.0:0,tls-creds=tls0

2.14.5 TLS Pre-Shared Keys (PSK)
--------------------------------

Instead of using certificates, you may also use TLS Pre-Shared Keys
(TLS-PSK). This can be simpler to set up than certificates but is less
scalable.

Use the GnuTLS ‘psktool’ program to generate a ‘keys.psk’ file
containing one or more usernames and random keys:

     mkdir -m 0700 /tmp/keys
     psktool -u rich -p /tmp/keys/keys.psk

TLS-enabled servers such as qemu-nbd can use this directory like so:

     qemu-nbd \
       -t -x / \
       --object tls-creds-psk,id=tls0,endpoint=server,dir=/tmp/keys \
       --tls-creds tls0 \
       image.qcow2

When connecting from a qemu-based client you must specify the directory
containing ‘keys.psk’ and an optional USERNAME (defaults to “qemu”):

     qemu-img info \
       --object tls-creds-psk,id=tls0,dir=/tmp/keys,username=rich,endpoint=client \
       --image-opts \
       file.driver=nbd,file.host=localhost,file.port=10809,file.tls-creds=tls0,file.export=/

2.15 GDB usage
==============

QEMU has a primitive support to work with gdb, so that you can do
’Ctrl-C’ while the virtual machine is running and inspect its state.

In order to use gdb, launch QEMU with the ’-s’ option.  It will wait for
a gdb connection:
     qemu-kvm -s -kernel bzImage -hda rootdisk.img -append "root=/dev/hda"
     Connected to host network interface: tun0
     Waiting gdb connection on port 1234

Then launch gdb on the ’vmlinux’ executable:
     > gdb vmlinux

In gdb, connect to QEMU:
     (gdb) target remote localhost:1234

Then you can use gdb normally.  For example, type ’c’ to launch the
kernel:
     (gdb) c

Here are some useful tips in order to use gdb on system code:

  1. Use ‘info reg’ to display all the CPU registers.
  2. Use ‘x/10i $eip’ to display the code at the PC position.
  3. Use ‘set architecture i8086’ to dump 16 bit code.  Then use ‘x/10i
     $cs*16+$eip’ to dump the code at the PC position.

Advanced debugging options:

The default single stepping behavior is step with the IRQs and timer
service routines off.  It is set this way because when gdb executes a
single step it expects to advance beyond the current instruction.  With
the IRQs and timer service routines on, a single step might jump into
the one of the interrupt or exception vectors instead of executing the
current instruction.  This means you may hit the same breakpoint a
number of times before executing the instruction gdb wants to have
executed.  Because there are rare circumstances where you want to single
step into an interrupt vector the behavior can be controlled from GDB.
There are three commands you can query and set the single step behavior:
‘maintenance packet qqemu.sstepbits’

     This will display the MASK bits used to control the single stepping
     IE:
          (gdb) maintenance packet qqemu.sstepbits
          sending: "qqemu.sstepbits"
          received: "ENABLE=1,NOIRQ=2,NOTIMER=4"
‘maintenance packet qqemu.sstep’

     This will display the current value of the mask used when single
     stepping IE:
          (gdb) maintenance packet qqemu.sstep
          sending: "qqemu.sstep"
          received: "0x7"
‘maintenance packet Qqemu.sstep=HEX_VALUE’

     This will change the single step mask, so if wanted to enable IRQs
     on the single step, but not timers, you would use:
          (gdb) maintenance packet Qqemu.sstep=0x5
          sending: "qemu.sstep=0x5"
          received: "OK"

2.16 Target OS specific information
===================================

2.16.1 Linux
------------

To have access to SVGA graphic modes under X11, use the ‘vesa’ or the
‘cirrus’ X11 driver.  For optimal performances, use 16 bit color depth
in the guest and the host OS.

When using a 2.6 guest Linux kernel, you should add the option
‘clock=pit’ on the kernel command line because the 2.6 Linux kernels
make very strict real time clock checks by default that QEMU cannot
simulate exactly.

When using a 2.6 guest Linux kernel, verify that the 4G/4G patch is not
activated because QEMU is slower with this patch.  The QEMU Accelerator
Module is also much slower in this case.  Earlier Fedora Core 3 Linux
kernel (< 2.6.9-1.724_FC3) were known to incorporate this patch by
default.  Newer kernels don’t have it.

2.16.2 Windows
--------------

If you have a slow host, using Windows 95 is better as it gives the best
speed.  Windows 2000 is also a good choice.

2.16.2.1 SVGA graphic modes support
...................................

QEMU emulates a Cirrus Logic GD5446 Video card.  All Windows versions
starting from Windows 95 should recognize and use this graphic card.
For optimal performances, use 16 bit color depth in the guest and the
host OS.

If you are using Windows XP as guest OS and if you want to use high
resolution modes which the Cirrus Logic BIOS does not support (i.e.  >=
1280x1024x16), then you should use the VESA VBE virtual graphic card
(option ‘-std-vga’).

2.16.2.2 CPU usage reduction
............................

Windows 9x does not correctly use the CPU HLT instruction.  The result
is that it takes host CPU cycles even when idle.  You can install the
utility from
<https://web.archive.org/web/20060212132151/http://www.user.cityline.ru/~maxamn/amnhltm.zip>
to solve this problem.  Note that no such tool is needed for NT, 2000 or
XP.

2.16.2.3 Windows 2000 disk full problem
.......................................

Windows 2000 has a bug which gives a disk full problem during its
installation.  When installing it, use the ‘-win2k-hack’ QEMU option to
enable a specific workaround.  After Windows 2000 is installed, you no
longer need this option (this option slows down the IDE transfers).

2.16.2.4 Windows 2000 shutdown
..............................

Windows 2000 cannot automatically shutdown in QEMU although Windows 98
can.  It comes from the fact that Windows 2000 does not automatically
use the APM driver provided by the BIOS.

In order to correct that, do the following (thanks to Struan Bartlett):
go to the Control Panel => Add/Remove Hardware & Next =>
Add/Troubleshoot a device => Add a new device & Next => No, select the
hardware from a list & Next => NT Apm/Legacy Support & Next => Next
(again) a few times.  Now the driver is installed and Windows 2000 now
correctly instructs QEMU to shutdown at the appropriate moment.

2.16.2.5 Share a directory between Unix and Windows
...................................................

See *note sec_invocation:: about the help of the option ‘'-netdev
user,smb=...'’.

2.16.2.6 Windows XP security problem
....................................

Some releases of Windows XP install correctly but give a security error
when booting:
     A problem is preventing Windows from accurately checking the
     license for this computer. Error code: 0x800703e6.

The workaround is to install a service pack for XP after a boot in safe
mode.  Then reboot, and the problem should go away.  Since there is no
network while in safe mode, its recommended to download the full
installation of SP1 or SP2 and transfer that via an ISO or using the
vvfat block device ("-hdb fat:directory_which_holds_the_SP").

2.16.3 MS-DOS and FreeDOS
-------------------------

2.16.3.1 CPU usage reduction
............................

DOS does not correctly use the CPU HLT instruction.  The result is that
it takes host CPU cycles even when idle.  You can install the utility
from
<https://web.archive.org/web/20051222085335/http://www.vmware.com/software/dosidle210.zip>
to solve this problem.

3 QEMU System emulator for non PC targets
*****************************************

QEMU is a generic emulator and it emulates many non PC machines.  Most
of the options are similar to the PC emulator.  The differences are
mentioned in the following sections.

3.1 PowerPC System emulator
===========================

Use the executable ‘qemu-system-ppc’ to simulate a complete PREP or
PowerMac PowerPC system.

QEMU emulates the following PowerMac peripherals:

   − UniNorth or Grackle PCI Bridge
   − PCI VGA compatible card with VESA Bochs Extensions
   − 2 PMAC IDE interfaces with hard disk and CD-ROM support
   − NE2000 PCI adapters
   − Non Volatile RAM
   − VIA-CUDA with ADB keyboard and mouse.

QEMU emulates the following PREP peripherals:

   − PCI Bridge
   − PCI VGA compatible card with VESA Bochs Extensions
   − 2 IDE interfaces with hard disk and CD-ROM support
   − Floppy disk
   − NE2000 network adapters
   − Serial port
   − PREP Non Volatile RAM
   − PC compatible keyboard and mouse.

QEMU uses the Open Hack’Ware Open Firmware Compatible BIOS available at
<http://perso.magic.fr/l_indien/OpenHackWare/index.htm>.

Since version 0.9.1, QEMU uses OpenBIOS <https://www.openbios.org/> for
the g3beige and mac99 PowerMac machines.  OpenBIOS is a free (GPL v2)
portable firmware implementation.  The goal is to implement a 100% IEEE
1275-1994 (referred to as Open Firmware) compliant firmware.

The following options are specific to the PowerPC emulation:

‘-g WxH[xDEPTH]’

     Set the initial VGA graphic mode.  The default is 800x600x32.

‘-prom-env STRING’

     Set OpenBIOS variables in NVRAM, for example:

          qemu-kvm -prom-env 'auto-boot?=false' \
           -prom-env 'boot-device=hd:2,\yaboot' \
           -prom-env 'boot-args=conf=hd:2,\yaboot.conf'

     These variables are not used by Open Hack’Ware.

More information is available at
<http://perso.magic.fr/l_indien/qemu-ppc/>.

3.2 Sparc32 System emulator
===========================

Use the executable ‘qemu-system-sparc’ to simulate the following Sun4m
architecture machines:
   − SPARCstation 4
   − SPARCstation 5
   − SPARCstation 10
   − SPARCstation 20
   − SPARCserver 600MP
   − SPARCstation LX
   − SPARCstation Voyager
   − SPARCclassic
   − SPARCbook

The emulation is somewhat complete.  SMP up to 16 CPUs is supported, but
Linux limits the number of usable CPUs to 4.

QEMU emulates the following sun4m peripherals:

   − IOMMU
   − TCX or cgthree Frame buffer
   − Lance (Am7990) Ethernet
   − Non Volatile RAM M48T02/M48T08
   − Slave I/O: timers, interrupt controllers, Zilog serial ports,
     keyboard and power/reset logic
   − ESP SCSI controller with hard disk and CD-ROM support
   − Floppy drive (not on SS-600MP)
   − CS4231 sound device (only on SS-5, not working yet)

The number of peripherals is fixed in the architecture.  Maximum memory
size depends on the machine type, for SS-5 it is 256MB and for others
2047MB.

Since version 0.8.2, QEMU uses OpenBIOS <https://www.openbios.org/>.
OpenBIOS is a free (GPL v2) portable firmware implementation.  The goal
is to implement a 100% IEEE 1275-1994 (referred to as Open Firmware)
compliant firmware.

A sample Linux 2.6 series kernel and ram disk image are available on the
QEMU web site.  There are still issues with NetBSD and OpenBSD, but most
kernel versions work.  Please note that currently older Solaris kernels
don’t work probably due to interface issues between OpenBIOS and
Solaris.

The following options are specific to the Sparc32 emulation:

‘-g WxHx[xDEPTH]’

     Set the initial graphics mode.  For TCX, the default is 1024x768x8
     with the option of 1024x768x24.  For cgthree, the default is
     1024x768x8 with the option of 1152x900x8 for people who wish to use
     OBP.

‘-prom-env STRING’

     Set OpenBIOS variables in NVRAM, for example:

          qemu-system-sparc -prom-env 'auto-boot?=false' \
           -prom-env 'boot-device=sd(0,2,0):d' -prom-env 'boot-args=linux single'

‘-M [SS-4|SS-5|SS-10|SS-20|SS-600MP|LX|Voyager|SPARCClassic] [|SPARCbook]’

     Set the emulated machine type.  Default is SS-5.

3.3 Sparc64 System emulator
===========================

Use the executable ‘qemu-system-sparc64’ to simulate a Sun4u (UltraSPARC
PC-like machine), Sun4v (T1 PC-like machine), or generic Niagara (T1)
machine.  The Sun4u emulator is mostly complete, being able to run
Linux, NetBSD and OpenBSD in headless (-nographic) mode.  The Sun4v
emulator is still a work in progress.

The Niagara T1 emulator makes use of firmware and OS binaries supplied
in the S10image/ directory of the OpenSPARC T1 project
<http://download.oracle.com/technetwork/systems/opensparc/OpenSPARCT1_Arch.1.5.tar.bz2>
and is able to boot the disk.s10hw2 Solaris image.
     qemu-system-sparc64 -M niagara -L /path-to/S10image/ \
                         -nographic -m 256 \
                         -drive if=pflash,readonly=on,file=/S10image/disk.s10hw2

QEMU emulates the following peripherals:

   − UltraSparc IIi APB PCI Bridge
   − PCI VGA compatible card with VESA Bochs Extensions
   − PS/2 mouse and keyboard
   − Non Volatile RAM M48T59
   − PC-compatible serial ports
   − 2 PCI IDE interfaces with hard disk and CD-ROM support
   − Floppy disk

The following options are specific to the Sparc64 emulation:

‘-prom-env STRING’

     Set OpenBIOS variables in NVRAM, for example:

          qemu-system-sparc64 -prom-env 'auto-boot?=false'

‘-M [sun4u|sun4v|niagara]’

     Set the emulated machine type.  The default is sun4u.

3.4 MIPS System emulator
========================

Four executables cover simulation of 32 and 64-bit MIPS systems in both
endian options, ‘qemu-system-mips’, ‘qemu-system-mipsel’
‘qemu-system-mips64’ and ‘qemu-system-mips64el’.  Five different machine
types are emulated:

   − A generic ISA PC-like machine "mips"
   − The MIPS Malta prototype board "malta"
   − An ACER Pica "pica61".  This machine needs the 64-bit emulator.
   − MIPS emulator pseudo board "mipssim"
   − A MIPS Magnum R4000 machine "magnum".  This machine needs the
     64-bit emulator.

The generic emulation is supported by Debian ’Etch’ and is able to
install Debian into a virtual disk image.  The following devices are
emulated:

   − A range of MIPS CPUs, default is the 24Kf
   − PC style serial port
   − PC style IDE disk
   − NE2000 network card

The Malta emulation supports the following devices:

   − Core board with MIPS 24Kf CPU and Galileo system controller
   − PIIX4 PCI/USB/SMbus controller
   − The Multi-I/O chip’s serial device
   − PCI network cards (PCnet32 and others)
   − Malta FPGA serial device
   − Cirrus (default) or any other PCI VGA graphics card

The Boston board emulation supports the following devices:

   − Xilinx FPGA, which includes a PCIe root port and an UART
   − Intel EG20T PCH connects the I/O peripherals, but only the SATA bus
     is emulated

The ACER Pica emulation supports:

   − MIPS R4000 CPU
   − PC-style IRQ and DMA controllers
   − PC Keyboard
   − IDE controller

The MIPS Magnum R4000 emulation supports:

   − MIPS R4000 CPU
   − PC-style IRQ controller
   − PC Keyboard
   − SCSI controller
   − G364 framebuffer

The Fulong 2E emulation supports:

   − Loongson 2E CPU
   − Bonito64 system controller as North Bridge
   − VT82C686 chipset as South Bridge
   − RTL8139D as a network card chipset

The mipssim pseudo board emulation provides an environment similar to
what the proprietary MIPS emulator uses for running Linux.  It supports:

   − A range of MIPS CPUs, default is the 24Kf
   − PC style serial port
   − MIPSnet network emulation

3.4.1 nanoMIPS System emulator
------------------------------

Executable ‘qemu-system-mipsel’ also covers simulation of 32-bit
nanoMIPS system in little endian mode:

   − nanoMIPS I7200 CPU

Example of ‘qemu-system-mipsel’ usage for nanoMIPS is shown below:

Download ‘<disk_image_file>’ from
<https://mipsdistros.mips.com/LinuxDistro/nanomips/buildroot/index.html>.

Download ‘<kernel_image_file>’ from
<https://mipsdistros.mips.com/LinuxDistro/nanomips/kernels/v4.15.18-432-gb2eb9a8b07a1-20180627102142/index.html>.

Start system emulation of Malta board with nanoMIPS I7200 CPU:
     qemu-system-mipsel -cpu I7200 -kernel <kernel_image_file> \
         -M malta -serial stdio -m <memory_size> -hda <disk_image_file> \
         -append "mem=256m@0x0 rw console=ttyS0 vga=cirrus vesa=0x111 root=/dev/sda"

3.5 ARM System emulator
=======================

Use the executable ‘qemu-system-arm’ to simulate a ARM machine.  The ARM
Integrator/CP board is emulated with the following devices:

   − ARM926E, ARM1026E, ARM946E, ARM1136 or Cortex-A8 CPU
   − Two PL011 UARTs
   − SMC 91c111 Ethernet adapter
   − PL110 LCD controller
   − PL050 KMI with PS/2 keyboard and mouse.
   − PL181 MultiMedia Card Interface with SD card.

The ARM Versatile baseboard is emulated with the following devices:

   − ARM926E, ARM1136 or Cortex-A8 CPU
   − PL190 Vectored Interrupt Controller
   − Four PL011 UARTs
   − SMC 91c111 Ethernet adapter
   − PL110 LCD controller
   − PL050 KMI with PS/2 keyboard and mouse.
   − PCI host bridge.  Note the emulated PCI bridge only provides access
     to PCI memory space.  It does not provide access to PCI IO space.
     This means some devices (eg.  ne2k_pci NIC) are not usable, and
     others (eg.  rtl8139 NIC) are only usable when the guest drivers
     use the memory mapped control registers.
   − PCI OHCI USB controller.
   − LSI53C895A PCI SCSI Host Bus Adapter with hard disk and CD-ROM
     devices.
   − PL181 MultiMedia Card Interface with SD card.

Several variants of the ARM RealView baseboard are emulated, including
the EB, PB-A8 and PBX-A9.  Due to interactions with the bootloader, only
certain Linux kernel configurations work out of the box on these boards.

Kernels for the PB-A8 board should have CONFIG_REALVIEW_HIGH_PHYS_OFFSET
enabled in the kernel, and expect 512M RAM. Kernels for The PBX-A9 board
should have CONFIG_SPARSEMEM enabled, CONFIG_REALVIEW_HIGH_PHYS_OFFSET
disabled and expect 1024M RAM.

The following devices are emulated:

   − ARM926E, ARM1136, ARM11MPCore, Cortex-A8 or Cortex-A9 MPCore CPU
   − ARM AMBA Generic/Distributed Interrupt Controller
   − Four PL011 UARTs
   − SMC 91c111 or SMSC LAN9118 Ethernet adapter
   − PL110 LCD controller
   − PL050 KMI with PS/2 keyboard and mouse
   − PCI host bridge
   − PCI OHCI USB controller
   − LSI53C895A PCI SCSI Host Bus Adapter with hard disk and CD-ROM
     devices
   − PL181 MultiMedia Card Interface with SD card.

The XScale-based clamshell PDA models ("Spitz", "Akita", "Borzoi" and
"Terrier") emulation includes the following peripherals:

   − Intel PXA270 System-on-chip (ARM V5TE core)
   − NAND Flash memory
   − IBM/Hitachi DSCM microdrive in a PXA PCMCIA slot - not in "Akita"
   − On-chip OHCI USB controller
   − On-chip LCD controller
   − On-chip Real Time Clock
   − TI ADS7846 touchscreen controller on SSP bus
   − Maxim MAX1111 analog-digital converter on I^2C bus
   − GPIO-connected keyboard controller and LEDs
   − Secure Digital card connected to PXA MMC/SD host
   − Three on-chip UARTs
   − WM8750 audio CODEC on I^2C and I^2S busses

The Palm Tungsten|E PDA (codename "Cheetah") emulation includes the
following elements:

   − Texas Instruments OMAP310 System-on-chip (ARM 925T core)
   − ROM and RAM memories (ROM firmware image can be loaded with
     -option-rom)
   − On-chip LCD controller
   − On-chip Real Time Clock
   − TI TSC2102i touchscreen controller / analog-digital converter /
     Audio CODEC, connected through MicroWire and I^2S busses
   − GPIO-connected matrix keypad
   − Secure Digital card connected to OMAP MMC/SD host
   − Three on-chip UARTs

Nokia N800 and N810 internet tablets (known also as RX-34 and RX-44 /
48) emulation supports the following elements:

   − Texas Instruments OMAP2420 System-on-chip (ARM 1136 core)
   − RAM and non-volatile OneNAND Flash memories
   − Display connected to EPSON remote framebuffer chip and OMAP on-chip
     display controller and a LS041y3 MIPI DBI-C controller
   − TI TSC2301 (in N800) and TI TSC2005 (in N810) touchscreen
     controllers driven through SPI bus
   − National Semiconductor LM8323-controlled qwerty keyboard driven
     through I^2C bus
   − Secure Digital card connected to OMAP MMC/SD host
   − Three OMAP on-chip UARTs and on-chip STI debugging console
   − A Bluetooth(R) transceiver and HCI connected to an UART
   − Mentor Graphics "Inventra" dual-role USB controller embedded in a
     TI TUSB6010 chip - only USB host mode is supported
   − TI TMP105 temperature sensor driven through I^2C bus
   − TI TWL92230C power management companion with an RTC on I^2C bus
   − Nokia RETU and TAHVO multi-purpose chips with an RTC, connected
     through CBUS

The Luminary Micro Stellaris LM3S811EVB emulation includes the following
devices:

   − Cortex-M3 CPU core.
   − 64k Flash and 8k SRAM.
   − Timers, UARTs, ADC and I^2C interface.
   − OSRAM Pictiva 96x16 OLED with SSD0303 controller on I^2C bus.

The Luminary Micro Stellaris LM3S6965EVB emulation includes the
following devices:

   − Cortex-M3 CPU core.
   − 256k Flash and 64k SRAM.
   − Timers, UARTs, ADC, I^2C and SSI interfaces.
   − OSRAM Pictiva 128x64 OLED with SSD0323 controller connected via
     SSI.

The Freecom MusicPal internet radio emulation includes the following
elements:

   − Marvell MV88W8618 ARM core.
   − 32 MB RAM, 256 KB SRAM, 8 MB flash.
   − Up to 2 16550 UARTs
   − MV88W8xx8 Ethernet controller
   − MV88W8618 audio controller, WM8750 CODEC and mixer
   − 128×64 display with brightness control
   − 2 buttons, 2 navigation wheels with button function

The Siemens SX1 models v1 and v2 (default) basic emulation.  The
emulation includes the following elements:

   − Texas Instruments OMAP310 System-on-chip (ARM 925T core)
   − ROM and RAM memories (ROM firmware image can be loaded with
     -pflash) V1 1 Flash of 16MB and 1 Flash of 8MB V2 1 Flash of 32MB
   − On-chip LCD controller
   − On-chip Real Time Clock
   − Secure Digital card connected to OMAP MMC/SD host
   − Three on-chip UARTs

A Linux 2.6 test image is available on the QEMU web site.  More
information is available in the QEMU mailing-list archive.

The following options are specific to the ARM emulation:

‘-semihosting’
     Enable semihosting syscall emulation.

     On ARM this implements the "Angel" interface.

     Note that this allows guest direct access to the host filesystem,
     so should only be used with trusted guest OS.

3.6 ColdFire System emulator
============================

Use the executable ‘qemu-system-m68k’ to simulate a ColdFire machine.
The emulator is able to boot a uClinux kernel.

The M5208EVB emulation includes the following devices:

   − MCF5208 ColdFire V2 Microprocessor (ISA A+ with EMAC).
   − Three Two on-chip UARTs.
   − Fast Ethernet Controller (FEC)

The AN5206 emulation includes the following devices:

   − MCF5206 ColdFire V2 Microprocessor.
   − Two on-chip UARTs.

The following options are specific to the ColdFire emulation:

‘-semihosting’
     Enable semihosting syscall emulation.

     On M68K this implements the "ColdFire GDB" interface used by
     libgloss.

     Note that this allows guest direct access to the host filesystem,
     so should only be used with trusted guest OS.

3.7 Cris System emulator
========================

TODO

3.8 Microblaze System emulator
==============================

TODO

3.9 SH4 System emulator
=======================

TODO

3.10 Xtensa System emulator
===========================

Two executables cover simulation of both Xtensa endian options,
‘qemu-system-xtensa’ and ‘qemu-system-xtensaeb’.  Two different machine
types are emulated:

   − Xtensa emulator pseudo board "sim"
   − Avnet LX60/LX110/LX200 board

The sim pseudo board emulation provides an environment similar to one
provided by the proprietary Tensilica ISS. It supports:

   − A range of Xtensa CPUs, default is the DC232B
   − Console and filesystem access via semihosting calls

The Avnet LX60/LX110/LX200 emulation supports:

   − A range of Xtensa CPUs, default is the DC232B
   − 16550 UART
   − OpenCores 10/100 Mbps Ethernet MAC

The following options are specific to the Xtensa emulation:

‘-semihosting’
     Enable semihosting syscall emulation.

     Xtensa semihosting provides basic file IO calls, such as
     open/read/write/seek/select.  Tensilica baremetal libc for ISS and
     linux platform "sim" use this interface.

     Note that this allows guest direct access to the host filesystem,
     so should only be used with trusted guest OS.

4 QEMU User space emulator
**************************

4.1 Supported Operating Systems
===============================

The following OS are supported in user space emulation:

   − Linux (referred as qemu-linux-user)
   − BSD (referred as qemu-bsd-user)

4.2 Features
============

QEMU user space emulation has the following notable features:

*System call translation:*
     QEMU includes a generic system call translator.  This means that
     the parameters of the system calls can be converted to fix
     endianness and 32/64-bit mismatches between hosts and targets.
     IOCTLs can be converted too.

*POSIX signal handling:*
     QEMU can redirect to the running program all signals coming from
     the host (such as ‘SIGALRM’), as well as synthesize signals from
     virtual CPU exceptions (for example ‘SIGFPE’ when the program
     executes a division by zero).

     QEMU relies on the host kernel to emulate most signal system calls,
     for example to emulate the signal mask.  On Linux, QEMU supports
     both normal and real-time signals.

*Threading:*
     On Linux, QEMU can emulate the ‘clone’ syscall and create a real
     host thread (with a separate virtual CPU) for each emulated thread.
     Note that not all targets currently emulate atomic operations
     correctly.  x86 and ARM use a global lock in order to preserve
     their semantics.

QEMU was conceived so that ultimately it can emulate itself.  Although
it is not very useful, it is an important test to show the power of the
emulator.

4.3 Linux User space emulator
=============================

4.3.1 Quick Start
-----------------

In order to launch a Linux process, QEMU needs the process executable
itself and all the target (x86) dynamic libraries used by it.

   • On x86, you can just try to launch any process by using the native
     libraries:

          qemu-i386 -L / /bin/ls

     ‘-L /’ tells that the x86 dynamic linker must be searched with a
     ‘/’ prefix.

   • Since QEMU is also a linux process, you can launch QEMU with QEMU
     (NOTE: you can only do that if you compiled QEMU from the sources):

          qemu-i386 -L / qemu-i386 -L / /bin/ls

   • On non x86 CPUs, you need first to download at least an x86 glibc
     (‘qemu-runtime-i386-XXX-.tar.gz’ on the QEMU web page).  Ensure
     that ‘LD_LIBRARY_PATH’ is not set:

          unset LD_LIBRARY_PATH

     Then you can launch the precompiled ‘ls’ x86 executable:

          qemu-i386 tests/i386/ls
     You can look at ‘scripts/qemu-binfmt-conf.sh’ so that QEMU is
     automatically launched by the Linux kernel when you try to launch
     x86 executables.  It requires the ‘binfmt_misc’ module in the Linux
     kernel.

   • The x86 version of QEMU is also included.  You can try weird things
     such as:
          qemu-i386 /usr/local/qemu-i386/bin/qemu-i386 \
                    /usr/local/qemu-i386/bin/ls-i386

4.3.2 Wine launch
-----------------

   • Ensure that you have a working QEMU with the x86 glibc distribution
     (see previous section).  In order to verify it, you must be able to
     do:

          qemu-i386 /usr/local/qemu-i386/bin/ls-i386

   • Download the binary x86 Wine install (‘qemu-XXX-i386-wine.tar.gz’
     on the QEMU web page).

   • Configure Wine on your account.  Look at the provided script
     ‘/usr/local/qemu-i386/bin/wine-conf.sh’.  Your previous
     ‘${HOME}/.wine’ directory is saved to ‘${HOME}/.wine.org’.

   • Then you can try the example ‘putty.exe’:

          qemu-i386 /usr/local/qemu-i386/wine/bin/wine \
                    /usr/local/qemu-i386/wine/c/Program\ Files/putty.exe

4.3.3 Command line options
--------------------------

     qemu-i386 [-h] [-d] [-L PATH] [-s SIZE] [-cpu MODEL] [-g PORT] [-B OFFSET] [-R SIZE] PROGRAM [ARGUMENTS...]

‘-h’
     Print the help
‘-L path’
     Set the x86 elf interpreter prefix (default=/usr/local/qemu-i386)
‘-s size’
     Set the x86 stack size in bytes (default=524288)
‘-cpu model’
     Select CPU model (-cpu help for list and additional feature
     selection)
‘-E VAR=VALUE’
     Set environment VAR to VALUE.
‘-U VAR’
     Remove VAR from the environment.
‘-B offset’
     Offset guest address by the specified number of bytes.  This is
     useful when the address region required by guest applications is
     reserved on the host.  This option is currently only supported on
     some hosts.
‘-R size’
     Pre-allocate a guest virtual address space of the given size (in
     bytes).  "G", "M", and "k" suffixes may be used when specifying the
     size.

Debug options:

‘-d item1,...’
     Activate logging of the specified items (use ’-d help’ for a list
     of log items)
‘-p pagesize’
     Act as if the host page size was ’pagesize’ bytes
‘-g port’
     Wait gdb connection to port
‘-singlestep’
     Run the emulation in single step mode.

Environment variables:

‘QEMU_STRACE’
     Print system calls and arguments similar to the ’strace’ program
     (NOTE: the actual ’strace’ program will not work because the user
     space emulator hasn’t implemented ptrace).  At the moment this is
     incomplete.  All system calls that don’t have a specific argument
     format are printed with information for six arguments.  Many
     flag-style arguments don’t have decoders and will show up as
     numbers.

4.3.4 Other binaries
--------------------

‘qemu-alpha’ TODO.

‘qemu-armeb’ TODO.

‘qemu-arm’ is also capable of running ARM "Angel" semihosted ELF
binaries (as implemented by the arm-elf and arm-eabi Newlib/GDB
configurations), and arm-uclinux bFLT format binaries.

‘qemu-m68k’ is capable of running semihosted binaries using the BDM
(m5xxx-ram-hosted.ld) or m68k-sim (sim.ld) syscall interfaces, and
coldfire uClinux bFLT format binaries.

The binary format is detected automatically.

‘qemu-cris’ TODO.

‘qemu-i386’ TODO. ‘qemu-x86_64’ TODO.

‘qemu-microblaze’ TODO.

‘qemu-mips’ executes 32-bit big endian MIPS binaries (MIPS O32 ABI).

‘qemu-mipsel’ executes 32-bit little endian MIPS binaries (MIPS O32
ABI).

‘qemu-mips64’ executes 64-bit big endian MIPS binaries (MIPS N64 ABI).

‘qemu-mips64el’ executes 64-bit little endian MIPS binaries (MIPS N64
ABI).

‘qemu-mipsn32’ executes 32-bit big endian MIPS binaries (MIPS N32 ABI).

‘qemu-mipsn32el’ executes 32-bit little endian MIPS binaries (MIPS N32
ABI).

‘qemu-nios2’ TODO.

‘qemu-ppc64abi32’ TODO. ‘qemu-ppc64’ TODO. ‘qemu-ppc’ TODO.

‘qemu-sh4eb’ TODO. ‘qemu-sh4’ TODO.

‘qemu-sparc’ can execute Sparc32 binaries (Sparc32 CPU, 32 bit ABI).

‘qemu-sparc32plus’ can execute Sparc32 and SPARC32PLUS binaries (Sparc64
CPU, 32 bit ABI).

‘qemu-sparc64’ can execute some Sparc64 (Sparc64 CPU, 64 bit ABI) and
SPARC32PLUS binaries (Sparc64 CPU, 32 bit ABI).

4.4 BSD User space emulator
===========================

4.4.1 BSD Status
----------------

   − target Sparc64 on Sparc64: Some trivial programs work.

4.4.2 Quick Start
-----------------

In order to launch a BSD process, QEMU needs the process executable
itself and all the target dynamic libraries used by it.

   • On Sparc64, you can just try to launch any process by using the
     native libraries:

          qemu-sparc64 /bin/ls

4.4.3 Command line options
--------------------------

     qemu-sparc64 [-h] [-d] [-L PATH] [-s SIZE] [-bsd TYPE] PROGRAM [ARGUMENTS...]

‘-h’
     Print the help
‘-L path’
     Set the library root path (default=/)
‘-s size’
     Set the stack size in bytes (default=524288)
‘-ignore-environment’
     Start with an empty environment.  Without this option, the initial
     environment is a copy of the caller’s environment.
‘-E VAR=VALUE’
     Set environment VAR to VALUE.
‘-U VAR’
     Remove VAR from the environment.
‘-bsd type’
     Set the type of the emulated BSD Operating system.  Valid values
     are FreeBSD, NetBSD and OpenBSD (default).

Debug options:

‘-d item1,...’
     Activate logging of the specified items (use ’-d help’ for a list
     of log items)
‘-p pagesize’
     Act as if the host page size was ’pagesize’ bytes
‘-singlestep’
     Run the emulation in single step mode.

5 System requirements
*********************

5.1 KVM kernel module
=====================

On x86_64 hosts, the default set of CPU features enabled by the KVM
accelerator require the host to be running Linux v4.5 or newer.

The OpteronG[345] CPU models require KVM support for RDTSCP, which was
added with Linux 4.5 which is supported by the major distros.  And even
if RHEL7 has kernel 3.10, KVM there has the required functionality there
to make it close to a 4.5 or newer kernel.

6 Security
**********

6.1 Overview
============

This chapter explains the security requirements that QEMU is designed to
meet and principles for securely deploying QEMU.

6.2 Security Requirements
=========================

QEMU supports many different use cases, some of which have stricter
security requirements than others.  The community has agreed on the
overall security requirements that users may depend on.  These
requirements define what is considered supported from a security
perspective.

6.2.1 Virtualization Use Case
-----------------------------

The virtualization use case covers cloud and virtual private server
(VPS) hosting, as well as traditional data center and desktop
virtualization.  These use cases rely on hardware virtualization
extensions to execute guest code safely on the physical CPU at
close-to-native speed.

The following entities are untrusted, meaning that they may be buggy or
malicious:

   • Guest
   • User-facing interfaces (e.g.  VNC, SPICE, WebSocket)
   • Network protocols (e.g.  NBD, live migration)
   • User-supplied files (e.g.  disk images, kernels, device trees)
   • Passthrough devices (e.g.  PCI, USB)

Bugs affecting these entities are evaluated on whether they can cause
damage in real-world use cases and treated as security bugs if this is
the case.

6.2.2 Non-virtualization Use Case
---------------------------------

The non-virtualization use case covers emulation using the Tiny Code
Generator (TCG). In principle the TCG and device emulation code used in
conjunction with the non-virtualization use case should meet the same
security requirements as the virtualization use case.  However, for
historical reasons much of the non-virtualization use case code was not
written with these security requirements in mind.

Bugs affecting the non-virtualization use case are not considered
security bugs at this time.  Users with non-virtualization use cases
must not rely on QEMU to provide guest isolation or any security
guarantees.

6.3 Architecture
================

This section describes the design principles that ensure the security
requirements are met.

6.3.1 Guest Isolation
---------------------

Guest isolation is the confinement of guest code to the virtual machine.
When guest code gains control of execution on the host this is called
escaping the virtual machine.  Isolation also includes resource limits
such as throttling of CPU, memory, disk, or network.  Guests must be
unable to exceed their resource limits.

QEMU presents an attack surface to the guest in the form of emulated
devices.  The guest must not be able to gain control of QEMU. Bugs in
emulated devices could allow malicious guests to gain code execution in
QEMU. At this point the guest has escaped the virtual machine and is
able to act in the context of the QEMU process on the host.

Guests often interact with other guests and share resources with them.
A malicious guest must not gain control of other guests or access their
data.  Disk image files and network traffic must be protected from other
guests unless explicitly shared between them by the user.

6.3.2 Principle of Least Privilege
----------------------------------

The principle of least privilege states that each component only has
access to the privileges necessary for its function.  In the case of
QEMU this means that each process only has access to resources belonging
to the guest.

The QEMU process should not have access to any resources that are
inaccessible to the guest.  This way the guest does not gain anything by
escaping into the QEMU process since it already has access to those same
resources from within the guest.

Following the principle of least privilege immediately fulfills guest
isolation requirements.  For example, guest A only has access to its own
disk image file ‘a.img’ and not guest B’s disk image file ‘b.img’.

In reality certain resources are inaccessible to the guest but must be
available to QEMU to perform its function.  For example, host system
calls are necessary for QEMU but are not exposed to guests.  A guest
that escapes into the QEMU process can then begin invoking host system
calls.

New features must be designed to follow the principle of least
privilege.  Should this not be possible for technical reasons, the
security risk must be clearly documented so users are aware of the
trade-off of enabling the feature.

6.3.3 Isolation mechanisms
--------------------------

Several isolation mechanisms are available to realize this architecture
of guest isolation and the principle of least privilege.  With the
exception of Linux seccomp, these mechanisms are all deployed by
management tools that launch QEMU, such as libvirt.  They are also
platform-specific so they are only described briefly for Linux here.

The fundamental isolation mechanism is that QEMU processes must run as
unprivileged users.  Sometimes it seems more convenient to launch QEMU
as root to give it access to host devices (e.g.  ‘/dev/net/tun’) but
this poses a huge security risk.  File descriptor passing can be used to
give an otherwise unprivileged QEMU process access to host devices
without running QEMU as root.  It is also possible to launch QEMU as a
non-root user and configure UNIX groups for access to ‘/dev/kvm’,
‘/dev/net/tun’, and other device nodes.  Some Linux distros already ship
with UNIX groups for these devices by default.

   • SELinux and AppArmor make it possible to confine processes beyond
     the traditional UNIX process and file permissions model.  They
     restrict the QEMU process from accessing processes and files on the
     host system that are not needed by QEMU.

   • Resource limits and cgroup controllers provide throughput and
     utilization limits on key resources such as CPU time, memory, and
     I/O bandwidth.

   • Linux namespaces can be used to make process, file system, and
     other system resources unavailable to QEMU. A namespaced QEMU
     process is restricted to only those resources that were granted to
     it.

   • Linux seccomp is available via the QEMU ‘--sandbox’ option.  It
     disables system calls that are not needed by QEMU, thereby reducing
     the host kernel attack surface.

6.4 Sensitive configurations
============================

There are aspects of QEMU that can have security implications which
users & management applications must be aware of.

6.4.1 Monitor console (QMP and HMP)
-----------------------------------

The monitor console (whether used with QMP or HMP) provides an interface
to dynamically control many aspects of QEMU’s runtime operation.  Many
of the commands exposed will instruct QEMU to access content on the host
file system and/or trigger spawning of external processes.

For example, the ‘migrate’ command allows for the spawning of arbitrary
processes for the purpose of tunnelling the migration data stream.  The
‘blockdev-add’ command instructs QEMU to open arbitrary files, exposing
their content to the guest as a virtual disk.

Unless QEMU is otherwise confined using technologies such as SELinux,
AppArmor, or Linux namespaces, the monitor console should be considered
to have privileges equivalent to those of the user account QEMU is
running under.

It is further important to consider the security of the character device
backend over which the monitor console is exposed.  It needs to have
protection against malicious third parties which might try to make
unauthorized connections, or perform man-in-the-middle attacks.  Many of
the character device backends do not satisfy this requirement and so
must not be used for the monitor console.

The general recommendation is that the monitor console should be exposed
over a UNIX domain socket backend to the local host only.  Use of the
TCP based character device backend is inappropriate unless configured to
use both TLS encryption and authorization control policy on client
connections.

In summary, the monitor console is considered a privileged control
interface to QEMU and as such should only be made accessible to a
trusted management application or user.

Appendix A Implementation notes
*******************************

A.1 CPU emulation
=================

A.1.1 x86 and x86-64 emulation
------------------------------

QEMU x86 target features:

   • The virtual x86 CPU supports 16 bit and 32 bit addressing with
     segmentation.  LDT/GDT and IDT are emulated.  VM86 mode is also
     supported to run DOSEMU. There is some support for MMX/3DNow!, SSE,
     SSE2, SSE3, SSSE3, and SSE4 as well as x86-64 SVM.

   • Support of host page sizes bigger than 4KB in user mode emulation.

   • QEMU can emulate itself on x86.

   • An extensive Linux x86 CPU test program is included
     ‘tests/test-i386’.  It can be used to test other x86 virtual CPUs.

Current QEMU limitations:

   • Limited x86-64 support.

   • IPC syscalls are missing.

   • The x86 segment limits and access rights are not tested at every
     memory access (yet).  Hopefully, very few OSes seem to rely on that
     for normal use.

A.1.2 ARM emulation
-------------------

   • Full ARM 7 user emulation.

   • NWFPE FPU support included in user Linux emulation.

   • Can run most ARM Linux binaries.

A.1.3 MIPS emulation
--------------------

   • The system emulation allows full MIPS32/MIPS64 Release 2 emulation,
     including privileged instructions, FPU and MMU, in both little and
     big endian modes.

   • The Linux userland emulation can run many 32 bit MIPS Linux
     binaries.

Current QEMU limitations:

   • Self-modifying code is not always handled correctly.

   • 64 bit userland emulation is not implemented.

   • The system emulation is not complete enough to run real firmware.

   • The watchpoint debug facility is not implemented.

A.1.4 PowerPC emulation
-----------------------

   • Full PowerPC 32 bit emulation, including privileged instructions,
     FPU and MMU.

   • Can run most PowerPC Linux binaries.

A.1.5 Sparc32 and Sparc64 emulation
-----------------------------------

   • Full SPARC V8 emulation, including privileged instructions, FPU and
     MMU. SPARC V9 emulation includes most privileged and VIS
     instructions, FPU and I/D MMU. Alignment is fully enforced.

   • Can run most 32-bit SPARC Linux binaries, SPARC32PLUS Linux
     binaries and some 64-bit SPARC Linux binaries.

Current QEMU limitations:

   • IPC syscalls are missing.

   • Floating point exception support is buggy.

   • Atomic instructions are not correctly implemented.

   • There are still some problems with Sparc64 emulators.

A.1.6 Xtensa emulation
----------------------

   • Core Xtensa ISA emulation, including most options: code density,
     loop, extended L32R, 16- and 32-bit multiplication, 32-bit
     division, MAC16, miscellaneous operations, boolean, FP coprocessor,
     coprocessor context, debug, multiprocessor synchronization,
     conditional store, exceptions, relocatable vectors, unaligned
     exception, interrupts (including high priority and timer), hardware
     alignment, region protection, region translation, MMU, windowed
     registers, thread pointer, processor ID.

   • Not implemented options: data/instruction cache (including cache
     prefetch and locking), XLMI, processor interface.  Also options not
     covered by the core ISA (e.g.  FLIX, wide branches) are not
     implemented.

   • Can run most Xtensa Linux binaries.

   • New core configuration that requires no additional instructions may
     be created from overlay with minimal amount of hand-written code.

A.2 Managed start up options
============================

In system mode emulation, it’s possible to create a VM in a paused state
using the -S command line option.  In this state the machine is
completely initialized according to command line options and ready to
execute VM code but VCPU threads are not executing any code.  The VM
state in this paused state depends on the way QEMU was started.  It
could be in:
initial state (after reset/power on state)
with direct kernel loading, the initial state could be amended to execute
     code loaded by QEMU in the VM’s RAM and with incoming migration
with incoming migration, initial state will by amended with the migrated
     machine state after migration completes.

This paused state is typically used by users to query machine state
and/or additionally configure the machine (by hotplugging devices) in
runtime before allowing VM code to run.

However, at the -S pause point, it’s impossible to configure options
that affect initial VM creation (like: -smp/-m/-numa ...)  or cold plug
devices.  The experimental –preconfig command line option allows pausing
QEMU before the initial VM creation, in a “preconfig” state, where
additional queries and configuration can be performed via QMP before
moving on to the resulting configuration startup.  In the preconfig
state, QEMU only allows a limited set of commands over the QMP monitor,
where the commands do not depend on an initialized machine, including
but not limited to:
qmp_capabilities
query-qmp-schema
query-commands
query-status
x-exit-preconfig

Appendix B Deprecated features
******************************

In general features are intended to be supported indefinitely once
introduced into QEMU. In the event that a feature needs to be removed,
it will be listed in this appendix.  The feature will remain functional
for 2 releases prior to actual removal.  Deprecated features may also
generate warnings on the console when QEMU starts up, or if activated
via a monitor command, however, this is not a mandatory requirement.

Prior to the 2.10.0 release there was no official policy on how long
features would be deprecated prior to their removal, nor any documented
list of which features were deprecated.  Thus any features deprecated
prior to 2.10.0 will be treated as if they were first deprecated in the
2.10.0 release.

What follows is a list of all features currently marked as deprecated.

B.1 System emulator command line arguments
==========================================

B.1.1 -machine enforce-config-section=on|off (since 3.1)
--------------------------------------------------------

The ‘enforce-config-section’ parameter is replaced by the ‘-global
migration.send-configuration=ON|OFF’ option.

B.1.2 -no-kvm (since 1.3.0)
---------------------------

The “-no-kvm” argument is now a synonym for setting “-accel tcg”.

B.1.3 -usbdevice (since 2.10.0)
-------------------------------

The “-usbdevice DEV” argument is now a synonym for setting the “-device
usb-DEV” argument instead.  The deprecated syntax would automatically
enable USB support on the machine type.  If using the new syntax, USB
support must be explicitly enabled via the “-machine usb=on” argument.

B.1.4 -drive file=json:{...{’driver’:’file’}} (since 3.0)
---------------------------------------------------------

The ’file’ driver for drives is no longer appropriate for character or
host devices and will only accept regular files (S_IFREG). The correct
driver for these file types is ’host_cdrom’ or ’host_device’ as
appropriate.

B.1.5 -net ...,name=NAME (since 3.1)
------------------------------------

The ‘name’ parameter of the ‘-net’ option is a synonym for the ‘id’
parameter, which should now be used instead.

B.1.6 -smp (invalid topologies) (since 3.1)
-------------------------------------------

CPU topology properties should describe whole machine topology including
possible CPUs.

However, historically it was possible to start QEMU with an incorrect
topology where N <= SOCKETS * CORES * THREADS < MAXCPUS, which could
lead to an incorrect topology enumeration by the guest.  Support for
invalid topologies will be removed, the user must ensure topologies
described with -smp include all possible cpus, i.e.  SOCKETS * CORES *
THREADS = MAXCPUS.

B.1.7 -vnc acl (since 4.0.0)
----------------------------

The ‘acl’ option to the ‘-vnc’ argument has been replaced by the
‘tls-authz’ and ‘sasl-authz’ options.

B.1.8 QEMU_AUDIO_ environment variables and -audio-help (since 4.0)
-------------------------------------------------------------------

The “-audiodev” argument is now the preferred way to specify audio
backend settings instead of environment variables.  To ease migration to
the new format, the “-audiodev-help” option can be used to convert the
current values of the environment variables to “-audiodev” options.

B.1.9 Creating sound card devices and vnc without audiodev= property (since 4.2)
--------------------------------------------------------------------------------

When not using the deprecated legacy audio config, each sound card
should specify an ‘audiodev=’ property.  Additionally, when using vnc,
you should specify an ‘audiodev=’ propery if you plan to transmit audio
through the VNC protocol.

B.1.10 -mon ...,control=readline,pretty=on|off (since 4.1)
----------------------------------------------------------

The ‘pretty=on|off’ switch has no effect for HMP monitors, but is
silently ignored.  Using the switch with HMP monitors will become an
error in the future.

B.1.11 -realtime (since 4.1)
----------------------------

The ‘-realtime mlock=on|off’ argument has been replaced by the
‘-overcommit mem-lock=on|off’ argument.

B.1.12 -virtfs_synth (since 4.1)
--------------------------------

The “-virtfs_synth” argument is now deprecated.  Please use “-fsdev
synth” and “-device virtio-9p-...” instead.

B.1.13 -numa node,mem=SIZE (since 4.1)
--------------------------------------

The parameter ‘mem’ of ‘-numa node’ is used to assign a part of guest
RAM to a NUMA node.  But when using it, it’s impossible to manage
specified RAM chunk on the host side (like bind it to a host node,
setting bind policy, ...), so guest end-ups with the fake NUMA
configuration with suboptiomal performance.  However since 2014 there is
an alternative way to assign RAM to a NUMA node using parameter
‘memdev’, which does the same as ‘mem’ and adds means to actualy manage
node RAM on the host side.  Use parameter ‘memdev’ with
MEMORY-BACKEND-RAM backend as an replacement for parameter ‘mem’ to
achieve the same fake NUMA effect or a properly configured
MEMORY-BACKEND-FILE backend to actually benefit from NUMA configuration.
In future new machine versions will not accept the option but it will
still work with old machine types.  User can check QAPI schema to see if
the legacy option is supported by looking at
MachineInfo::numa-mem-supported property.

B.1.14 -numa node (without memory specified) (since 4.1)
--------------------------------------------------------

Splitting RAM by default between NUMA nodes has the same issues as ‘mem’
parameter described above with the difference that the role of the user
plays QEMU using implicit generic or board specific splitting rule.  Use
‘memdev’ with MEMORY-BACKEND-RAM backend or ‘mem’ (if it’s supported by
used machine type) to define mapping explictly instead.

B.1.15 -mem-path fallback to RAM (since 4.1)
--------------------------------------------

Currently if guest RAM allocation from file pointed by ‘mem-path’ fails,
QEMU falls back to allocating from RAM, which might result in
unpredictable behavior since the backing file specified by the user is
ignored.  In the future, users will be responsible for making sure the
backing storage specified with ‘-mem-path’ can actually provide the
guest RAM configured with ‘-m’ and QEMU will fail to start up if RAM
allocation is unsuccessful.

B.1.16 RISC-V -bios (since 4.1)
-------------------------------

QEMU 4.1 introduced support for the -bios option in QEMU for RISC-V for
the RISC-V virt machine and sifive_u machine.

QEMU 4.1 has no changes to the default behaviour to avoid breakages.
This default will change in a future QEMU release, so please prepare
now.  All users of the virt or sifive_u machine must change their
command line usage.

QEMU 4.1 has three options, please migrate to one of these three: 1.
“-bios none“ - This is the current default behavior if no -bios option
is included.  QEMU will not automatically load any firmware.  It is up
to the user to load all the images they need.  2.  “-bios default“ - In
a future QEMU release this will become the default behaviour if no -bios
option is specified.  This option will load the default OpenSBI firmware
automatically.  The firmware is included with the QEMU release and no
user interaction is required.  All a user needs to do is specify the
kernel they want to boot with the -kernel option 3.  “-bios <file>“ -
Tells QEMU to load the specified file as the firmwrae.

B.2 QEMU Machine Protocol (QMP) commands
========================================

B.2.1 change (since 2.5.0)
--------------------------

Use “blockdev-change-medium” or “change-vnc-password” instead.

B.2.2 migrate_set_downtime and migrate_set_speed (since 2.8.0)
--------------------------------------------------------------

Use “migrate-set-parameters” instead.

B.2.3 migrate-set-cache-size and query-migrate-cache-size (since 2.11.0)
------------------------------------------------------------------------

Use “migrate-set-parameters” and “query-migrate-parameters” instead.

B.2.4 query-block result field dirty-bitmaps[i].status (since 4.0)
------------------------------------------------------------------

The “status” field of the “BlockDirtyInfo” structure, returned by the
query-block command is deprecated.  Two new boolean fields, “recording”
and “busy” effectively replace it.

B.2.5 query-block result field dirty-bitmaps (Since 4.2)
--------------------------------------------------------

The “dirty-bitmaps“ field of the “BlockInfo“ structure, returned by the
query-block command is itself now deprecated.  The “dirty-bitmaps“ field
of the “BlockDeviceInfo“ struct should be used instead, which is the
type of the “inserted“ field in query-block replies, as well as the type
of array items in query-named-block-nodes.

Since the “dirty-bitmaps“ field is optionally present in both the old
and new locations, clients must use introspection to learn where to
anticipate the field if/when it does appear in command output.

B.2.6 query-cpus (since 2.12.0)
-------------------------------

The “query-cpus” command is replaced by the “query-cpus-fast” command.

B.2.7 query-cpus-fast "arch" output member (since 3.0.0)
--------------------------------------------------------

The “arch” output member of the “query-cpus-fast” command is replaced by
the “target” output member.

B.2.8 cpu-add (since 4.0)
-------------------------

Use “device_add” for hotplugging vCPUs instead of “cpu-add”.  See
documentation of “query-hotpluggable-cpus” for additional details.

B.2.9 query-events (since 4.0)
------------------------------

The “query-events” command has been superseded by the more powerful and
accurate “query-qmp-schema” command.

B.2.10 chardev client socket with ’wait’ option (since 4.0)
-----------------------------------------------------------

Character devices creating sockets in client mode should not specify the
’wait’ field, which is only applicable to sockets in server mode

B.3 Human Monitor Protocol (HMP) commands
=========================================

B.3.1 The hub_id parameter of ’hostfwd_add’ / ’hostfwd_remove’ (since 3.1)
--------------------------------------------------------------------------

The ‘[hub_id name]’ parameter tuple of the ’hostfwd_add’ and
’hostfwd_remove’ HMP commands has been replaced by ‘netdev_id’.

B.3.2 cpu-add (since 4.0)
-------------------------

Use “device_add” for hotplugging vCPUs instead of “cpu-add”.  See
documentation of “query-hotpluggable-cpus” for additional details.

B.3.3 acl_show, acl_reset, acl_policy, acl_add, acl_remove (since 4.0.0)
------------------------------------------------------------------------

The “acl_show”, “acl_reset”, “acl_policy”, “acl_add”, and “acl_remove”
commands are deprecated with no replacement.  Authorization for VNC
should be performed using the pluggable QAuthZ objects.

B.4 Guest Emulator ISAs
=======================

B.4.1 RISC-V ISA privledge specification version 1.09.1 (since 4.1)
-------------------------------------------------------------------

The RISC-V ISA privledge specification version 1.09.1 has been
deprecated.  QEMU supports both the newer version 1.10.0 and the
ratified version 1.11.0, these should be used instead of the 1.09.1
version.

B.5 System emulator CPUS
========================

B.5.1 RISC-V ISA CPUs (since 4.1)
---------------------------------

The RISC-V cpus with the ISA version in the CPU name have been
depcreated.  The four CPUs are: “rv32gcsu-v1.9.1“, “rv32gcsu-v1.10.0“,
“rv64gcsu-v1.9.1“ and “rv64gcsu-v1.10.0“.  Instead the version can be
specified via the CPU “priv_spec“ option when using the “rv32“ or “rv64“
CPUs.

B.5.2 RISC-V ISA CPUs (since 4.1)
---------------------------------

The RISC-V no MMU cpus have been depcreated.  The two CPUs:
“rv32imacu-nommu“ and “rv64imacu-nommu“ should no longer be used.
Instead the MMU status can be specified via the CPU “mmu“ option when
using the “rv32“ or “rv64“ CPUs.

B.6 System emulator devices
===========================

B.6.1 bluetooth (since 3.1)
---------------------------

The bluetooth subsystem is unmaintained since many years and likely
bitrotten quite a bit.  It will be removed without replacement unless
some users speaks up at the <qemu-devel@nongnu.org> mailing list with
information about their usecases.

B.6.2 ide-drive (since 4.2)
---------------------------

The ’ide-drive’ device is deprecated.  Users should use ’ide-hd’ or
’ide-cd’ as appropriate to get an IDE hard disk or CD-ROM as needed.

B.6.3 scsi-disk (since 4.2)
---------------------------

The ’scsi-disk’ device is deprecated.  Users should use ’scsi-hd’ or
’scsi-cd’ as appropriate to get a SCSI hard disk or CD-ROM as needed.

B.7 System emulator machines
============================

B.7.1 pc-0.12, pc-0.13, pc-0.14 and pc-0.15 (since 4.0)
-------------------------------------------------------

These machine types are very old and likely can not be used for live
migration from old QEMU versions anymore.  A newer machine type should
be used instead.

B.7.2 prep (PowerPC) (since 3.1)
--------------------------------

This machine type uses an unmaintained firmware, broken in lots of ways,
and unable to start post-2004 operating systems.  40p machine type
should be used instead.

B.7.3 spike_v1.9.1 and spike_v1.10 (since 4.1)
----------------------------------------------

The version specific Spike machines have been deprecated in favour of
the generic “spike“ machine.  If you need to specify an older version of
the RISC-V spec you can use the “-cpu rv64gcsu,priv_spec=v1.9.1“ command
line argument.

B.8 Device options
==================

B.8.1 Block device options
--------------------------

B.8.1.1 "backing": "" (since 2.12.0)
....................................

In order to prevent QEMU from automatically opening an image’s backing
chain, use “"backing": null” instead.

B.8.1.2 rbd keyvalue pair encoded filenames: "" (since 3.1.0)
.............................................................

Options for “rbd” should be specified according to its runtime options,
like other block drivers.  Legacy parsing of keyvalue pair encoded
filenames is useful to open images with the old format for backing
files; These image files should be updated to use the current format.

Example of legacy encoding:

‘json:{"file.driver":"rbd", "file.filename":"rbd:rbd/name"}’

The above, converted to the current supported format:

‘json:{"file.driver":"rbd", "file.pool":"rbd", "file.image":"name"}’

B.9 Related binaries
====================

B.9.1 qemu-nbd –partition (since 4.0.0)
---------------------------------------

The “qemu-nbd –partition $digit” code (also spelled ‘-P’) can only
handle MBR partitions, and has never correctly handled logical
partitions beyond partition 5.  If you know the offset and length of the
partition (perhaps by using ‘sfdisk’ within the guest), you can achieve
the effect of exporting just that subset of the disk by use of the
‘--image-opts’ option with a raw blockdev using the ‘offset’ and ‘size’
parameters layered on top of any other existing blockdev.  For example,
if partition 1 is 100MiB long starting at 1MiB, the old command:

‘qemu-nbd -t -P 1 -f qcow2 file.qcow2’

can be rewritten as:

‘qemu-nbd -t --image-opts
driver=raw,offset=1M,size=100M,file.driver=qcow2,file.backing.driver=file,file.backing.filename=file.qcow2’

Alternatively, the ‘nbdkit’ project provides a more powerful partition
filter on top of its nbd plugin, which can be used to select an
arbitrary MBR or GPT partition on top of any other full-image NBD
export.  Using this to rewrite the above example results in:

‘qemu-nbd -t -k /tmp/sock -f qcow2 file.qcow2 &’ ‘nbdkit -f
--filter=partition nbd socket=/tmp/sock partition=1’

Note that if you are exposing the export via /dev/nbd0, it is easier to
just export the entire image and then mount only /dev/nbd0p1 than it is
to reinvoke ‘qemu-nbd -c /dev/nbd0’ limited to just a subset of the
image.

B.9.2 qemu-img convert -n -o (since 4.2.0)
------------------------------------------

All options specified in ‘-o’ are image creation options, so they have
no effect when used with ‘-n’ to skip image creation.  Silently ignored
options can be confusing, so this combination of options will be made an
error in future versions.

B.10 Build system
=================

B.10.1 Python 2 support (since 4.1.0)
-------------------------------------

In the future, QEMU will require Python 3 to be available at build time.
Support for Python 2 in scripts shipped with QEMU is deprecated.

B.11 Backwards compatibility
============================

B.11.1 Runnability guarantee of CPU models (since 4.1.0)
--------------------------------------------------------

Previous versions of QEMU never changed existing CPU models in ways that
introduced additional host software or hardware requirements to the VM.
This allowed management software to safely change the machine type of an
existing VM without introducing new requirements ("runnability
guarantee").  This prevented CPU models from being updated to include
CPU vulnerability mitigations, leaving guests vulnerable in the default
configuration.

The CPU model runnability guarantee won’t apply anymore to existing CPU
models.  Management software that needs runnability guarantees must
resolve the CPU model aliases using te “alias-of” field returned by the
“query-cpu-definitions” QMP command.

While those guarantees are kept, the return value of
“query-cpu-definitions” will have existing CPU model aliases point to a
version that doesn’t break runnability guarantees (specifically, version
1 of those CPU models).  In future QEMU versions, aliases will point to
newer CPU model versions depending on the machine type, so management
software must resolve CPU model aliases before starting a virtual
machine.

Appendix C Recently removed features
************************************

What follows is a record of recently removed, formerly deprecated
features that serves as a record for users who have encountered trouble
after a recent upgrade.

C.1 QEMU Machine Protocol (QMP) commands
========================================

C.1.1 block-dirty-bitmap-add "autoload" parameter (since 4.2.0)
---------------------------------------------------------------

The "autoload" parameter has been ignored since 2.12.0.  All bitmaps are
automatically loaded from qcow2 images.

Appendix D Supported build platforms
************************************

QEMU aims to support building and executing on multiple host OS
platforms.  This appendix outlines which platforms are the major build
targets.  These platforms are used as the basis for deciding upon the
minimum required versions of 3rd party software QEMU depends on.  The
supported platforms are the targets for automated testing performed by
the project when patches are submitted for review, and tested before and
after merge.

If a platform is not listed here, it does not imply that QEMU won’t
work.  If an unlisted platform has comparable software versions to a
listed platform, there is every expectation that it will work.  Bug
reports are welcome for problems encountered on unlisted platforms
unless they are clearly older vintage than what is described here.

Note that when considering software versions shipped in distros as
support targets, QEMU considers only the version number, and assumes the
features in that distro match the upstream release with the same
version.  In other words, if a distro backports extra features to the
software in their distro, QEMU upstream code will not add explicit
support for those backports, unless the feature is auto-detectable in a
manner that works for the upstream releases too.

The Repology site <https://repology.org> is a useful resource to
identify currently shipped versions of software in various operating
systems, though it does not cover all distros listed below.

D.1 Linux OS
============

For distributions with frequent, short-lifetime releases, the project
will aim to support all versions that are not end of life by their
respective vendors.  For the purposes of identifying supported software
versions, the project will look at Fedora, Ubuntu, and openSUSE distros.
Other short- lifetime distros will be assumed to ship similar software
versions.

For distributions with long-lifetime releases, the project will aim to
support the most recent major version at all times.  Support for the
previous major version will be dropped 2 years after the new major
version is released.  For the purposes of identifying supported software
versions, the project will look at RHEL, Debian, Ubuntu LTS, and SLES
distros.  Other long-lifetime distros will be assumed to ship similar
software versions.

D.2 Windows
===========

The project supports building with current versions of the MinGW
toolchain, hosted on Linux.

D.3 macOS
=========

The project supports building with the two most recent versions of
macOS, with the current homebrew package set available.

D.4 FreeBSD
===========

The project aims to support the all the versions which are not end of
life.

D.5 NetBSD
==========

The project aims to support the most recent major version at all times.
Support for the previous major version will be dropped 2 years after the
new major version is released.

D.6 OpenBSD
===========

The project aims to support the all the versions which are not end of
life.

Appendix E License
******************

QEMU is a trademark of Fabrice Bellard.

QEMU is released under the GNU General Public License
(https://www.gnu.org/licenses/gpl-2.0.txt), version 2.  Parts of QEMU
have specific licenses, see file LICENSE
(https://git.qemu.org/?p=qemu.git;a=blob_plain;f=LICENSE).

Appendix F Index
****************

F.1 Concept Index
=================

This is the main index.  Should we combine all keywords in one index?
TODO

* Menu:

* operating modes:                       intro_features.     (line  236)
* QEMU monitor:                          pcsys_monitor.      (line 4187)
* quick start:                           pcsys_quickstart.   (line  338)
* system emulation:                      intro_features.     (line  238)
* system emulation (ARM):                ARM System emulator.
                                                             (line 8278)
* system emulation (ColdFire):           ColdFire System emulator.
                                                             (line 8435)
* system emulation (Cris):               Cris System emulator.
                                                             (line 8463)
* system emulation (M68K):               ColdFire System emulator.
                                                             (line 8435)
* system emulation (Microblaze):         Microblaze System emulator.
                                                             (line 8468)
* system emulation (MIPS):               MIPS System emulator.
                                                             (line 8189)
* system emulation (nanoMIPS):           nanoMIPS System emulator.
                                                             (line 8257)
* system emulation (PC):                 QEMU PC System emulator.
                                                             (line  289)
* system emulation (PowerPC):            PowerPC System emulator.
                                                             (line 8032)
* system emulation (SH4):                SH4 System emulator.
                                                             (line 8473)
* system emulation (Sparc32):            Sparc32 System emulator.
                                                             (line 8085)
* system emulation (Sparc64):            Sparc64 System emulator.
                                                             (line 8150)
* system emulation (Xtensa):             Xtensa System emulator.
                                                             (line 8478)
* user mode (Alpha):                     Other binaries.     (line 8668)
* user mode (ARM):                       Other binaries.     (line 8670)
* user mode (ARM) <1>:                   Other binaries.     (line 8672)
* user mode (ColdFire):                  Other binaries.     (line 8676)
* user mode (Cris):                      Other binaries.     (line 8682)
* user mode (i386):                      Other binaries.     (line 8684)
* user mode (M68K):                      Other binaries.     (line 8676)
* user mode (Microblaze):                Other binaries.     (line 8686)
* user mode (MIPS):                      Other binaries.     (line 8688)
* user mode (NiosII):                    Other binaries.     (line 8703)
* user mode (PowerPC):                   Other binaries.     (line 8705)
* user mode (SH4):                       Other binaries.     (line 8707)
* user mode (SPARC):                     Other binaries.     (line 8709)
* user mode emulation:                   intro_features.     (line  243)

F.2 Function Index
==================

This index could be used for command line options and monitor functions.

* Menu:

* --preconfig:                           sec_invocation.     (line 2988)
* --trace:                               qemu_img_invocation.
                                                             (line 5441)
* --trace <1>:                           qemu_nbd_invocation.
                                                             (line 6231)
* -accel:                                sec_invocation.     (line  428)
* -acpitable:                            sec_invocation.     (line 1952)
* -add-fd:                               sec_invocation.     (line  586)
* -alt-grab:                             sec_invocation.     (line 1603)
* -append:                               sec_invocation.     (line 2794)
* -audio-help:                           sec_invocation.     (line  697)
* -audiodev:                             sec_invocation.     (line  700)
* -bios:                                 sec_invocation.     (line 3047)
* -blockdev:                             sec_invocation.     (line  980)
* -boot:                                 sec_invocation.     (line  623)
* -bt:                                   sec_invocation.     (line 2669)
* -cdrom:                                sec_invocation.     (line  976)
* -chardev:                              sec_invocation.     (line 2398)
* -chroot:                               sec_invocation.     (line 3215)
* -cpu:                                  sec_invocation.     (line  425)
* -ctrl-grab:                            sec_invocation.     (line 1607)
* -curses:                               sec_invocation.     (line 1597)
* -d:                                    sec_invocation.     (line 3025)
* -D:                                    sec_invocation.     (line 3028)
* -daemonize:                            sec_invocation.     (line 3066)
* -debugcon:                             sec_invocation.     (line 2977)
* -device:                               sec_invocation.     (line  882)
* -dfilter:                              sec_invocation.     (line 3030)
* -display:                              sec_invocation.     (line 1550)
* -drive:                                sec_invocation.     (line 1171)
* -dtb:                                  sec_invocation.     (line 2805)
* -dump-vmstate:                         sec_invocation.     (line 3303)
* -echr:                                 sec_invocation.     (line 3175)
* -enable-fips:                          sec_invocation.     (line 3299)
* -enable-kvm:                           sec_invocation.     (line 3049)
* -enable-sync-profile:                  sec_invocation.     (line 3306)
* -fda:                                  sec_invocation.     (line  969)
* -fdb:                                  sec_invocation.     (line  969)
* -fsdev:                                sec_invocation.     (line 1337)
* -full-screen:                          sec_invocation.     (line 1751)
* -fw_cfg:                               sec_invocation.     (line 2812)
* -g:                                    sec_invocation.     (line 1753)
* -gdb:                                  sec_invocation.     (line 3016)
* -global:                               sec_invocation.     (line  610)
* -h:                                    sec_invocation.     (line  357)
* -hda:                                  sec_invocation.     (line  974)
* -hdb:                                  sec_invocation.     (line  974)
* -hdc:                                  sec_invocation.     (line  974)
* -hdd:                                  sec_invocation.     (line  974)
* -icount:                               sec_invocation.     (line 3099)
* -incoming:                             sec_invocation.     (line 3190)
* -initrd:                               sec_invocation.     (line 2796)
* -iscsi:                                sec_invocation.     (line 1517)
* -k:                                    sec_invocation.     (line  684)
* -kernel:                               sec_invocation.     (line 2791)
* -L:                                    sec_invocation.     (line 3043)
* -loadvm:                               sec_invocation.     (line 3064)
* -m:                                    sec_invocation.     (line  664)
* -machine:                              sec_invocation.     (line  361)
* -mem-path:                             sec_invocation.     (line  680)
* -mem-prealloc:                         sec_invocation.     (line  682)
* -mon:                                  sec_invocation.     (line 2974)
* -monitor:                              sec_invocation.     (line 2965)
* -msg:                                  sec_invocation.     (line 3301)
* -mtdblock:                             sec_invocation.     (line 1322)
* -name:                                 sec_invocation.     (line  956)
* -net:                                  sec_invocation.     (line 2375)
* -netdev:                               sec_invocation.     (line 2008)
* -nic:                                  sec_invocation.     (line 1986)
* -no-acpi:                              sec_invocation.     (line 1948)
* -no-fd-bootchk:                        sec_invocation.     (line 1945)
* -no-quit:                              sec_invocation.     (line 1611)
* -no-reboot:                            sec_invocation.     (line 3058)
* -no-shutdown:                          sec_invocation.     (line 3060)
* -no-user-config:                       sec_invocation.     (line 3265)
* -nodefaults:                           sec_invocation.     (line 3210)
* -nographic:                            sec_invocation.     (line 1587)
* -numa:                                 sec_invocation.     (line  455)
* -object:                               sec_invocation.     (line 3312)
* -old-param (ARM):                      sec_invocation.     (line 3243)
* -only-migratable:                      sec_invocation.     (line 3207)
* -option-rom:                           sec_invocation.     (line 3072)
* -overcommit:                           sec_invocation.     (line 3001)
* -parallel:                             sec_invocation.     (line 2955)
* -pflash:                               sec_invocation.     (line 1326)
* -pidfile:                              sec_invocation.     (line 2983)
* -plugin:                               sec_invocation.     (line 3290)
* -portrait:                             sec_invocation.     (line 1712)
* -prom-env:                             sec_invocation.     (line 3221)
* -qmp:                                  sec_invocation.     (line 2970)
* -qmp-pretty:                           sec_invocation.     (line 2972)
* -readconfig:                           sec_invocation.     (line 3256)
* -realtime:                             sec_invocation.     (line 2997)
* -rotate:                               sec_invocation.     (line 1714)
* -rtc:                                  sec_invocation.     (line 3076)
* -runas:                                sec_invocation.     (line 3218)
* -S:                                    sec_invocation.     (line 2995)
* -s:                                    sec_invocation.     (line 3022)
* -sandbox:                              sec_invocation.     (line 3245)
* -sd:                                   sec_invocation.     (line 1324)
* -sdl:                                  sec_invocation.     (line 1613)
* -seed:                                 sec_invocation.     (line 3039)
* -semihosting:                          sec_invocation.     (line 3223)
* -semihosting-config:                   sec_invocation.     (line 3225)
* -serial:                               sec_invocation.     (line 2829)
* -set:                                  sec_invocation.     (line  607)
* -show-cursor:                          sec_invocation.     (line 3185)
* -singlestep:                           sec_invocation.     (line 2986)
* -smbios:                               sec_invocation.     (line 1962)
* -smp:                                  sec_invocation.     (line  441)
* -snapshot:                             sec_invocation.     (line 1328)
* -soundhw:                              sec_invocation.     (line  867)
* -spice:                                sec_invocation.     (line 1615)
* -tb-size:                              sec_invocation.     (line 3187)
* -tpmdev:                               sec_invocation.     (line 2724)
* -trace:                                sec_invocation.     (line 3268)
* -usb:                                  sec_invocation.     (line 1523)
* -usbdevice:                            sec_invocation.     (line 1529)
* -uuid:                                 sec_invocation.     (line  962)
* -version:                              sec_invocation.     (line  359)
* -vga:                                  sec_invocation.     (line 1716)
* -virtfs:                               sec_invocation.     (line 1425)
* -virtfs_synth:                         sec_invocation.     (line 1513)
* -vnc:                                  sec_invocation.     (line 1755)
* -watchdog:                             sec_invocation.     (line 3136)
* -watchdog-action:                      sec_invocation.     (line 3155)
* -win2k-hack:                           sec_invocation.     (line 1941)
* -writeconfig:                          sec_invocation.     (line 3260)
* -xen-attach:                           sec_invocation.     (line 3054)
* -xen-domid:                            sec_invocation.     (line 3052)
* -xen-domid-restrict:                   sec_invocation.     (line 3055)
* acl_add:                               pcsys_monitor.      (line 4568)
* acl_policy:                            pcsys_monitor.      (line 4564)
* acl_remove:                            pcsys_monitor.      (line 4576)
* acl_reset:                             pcsys_monitor.      (line 4578)
* acl_show:                              pcsys_monitor.      (line 4559)
* announce_self:                         pcsys_monitor.      (line 4464)
* balloon:                               pcsys_monitor.      (line 4553)
* block_job_cancel:                      pcsys_monitor.      (line 4232)
* block_job_complete:                    pcsys_monitor.      (line 4234)
* block_job_pause:                       pcsys_monitor.      (line 4238)
* block_job_resume:                      pcsys_monitor.      (line 4240)
* block_job_set_speed:                   pcsys_monitor.      (line 4230)
* block_passwd:                          pcsys_monitor.      (line 4608)
* block_resize:                          pcsys_monitor.      (line 4222)
* block_set_io_throttle:                 pcsys_monitor.      (line 4613)
* block_stream:                          pcsys_monitor.      (line 4228)
* boot_set:                              pcsys_monitor.      (line 4441)
* change:                                pcsys_monitor.      (line 4252)
* chardev-add:                           pcsys_monitor.      (line 4641)
* chardev-change:                        pcsys_monitor.      (line 4645)
* chardev-remove:                        pcsys_monitor.      (line 4649)
* chardev-send-break:                    pcsys_monitor.      (line 4652)
* client_migrate_info:                   pcsys_monitor.      (line 4502)
* closefd:                               pcsys_monitor.      (line 4604)
* commit:                                pcsys_monitor.      (line 4206)
* cont:                                  pcsys_monitor.      (line 4326)
* cpu:                                   pcsys_monitor.      (line 4415)
* cpu-add:                               pcsys_monitor.      (line 4658)
* delvm:                                 pcsys_monitor.      (line 4316)
* device_add:                            pcsys_monitor.      (line 4411)
* device_del:                            pcsys_monitor.      (line 4413)
* drive_add:                             pcsys_monitor.      (line 4536)
* drive_backup:                          pcsys_monitor.      (line 4533)
* drive_del:                             pcsys_monitor.      (line 4244)
* drive_mirror:                          pcsys_monitor.      (line 4530)
* dump-guest-memory:                     pcsys_monitor.      (line 4508)
* dump-skeys:                            pcsys_monitor.      (line 4520)
* eject:                                 pcsys_monitor.      (line 4242)
* exit_preconfig:                        pcsys_monitor.      (line 4216)
* expire_password:                       pcsys_monitor.      (line 4624)
* gdbserver:                             pcsys_monitor.      (line 4330)
* getfd:                                 pcsys_monitor.      (line 4600)
* gpa2hpa:                               pcsys_monitor.      (line 4381)
* gpa2hva:                               pcsys_monitor.      (line 4378)
* gva2gpa:                               pcsys_monitor.      (line 4384)
* help:                                  pcsys_monitor.      (line 4204)
* hostfwd_add:                           pcsys_monitor.      (line 4548)
* hostfwd_remove:                        pcsys_monitor.      (line 4551)
* i:                                     pcsys_monitor.      (line 4389)
* info:                                  pcsys_monitor.      (line 4667)
* info balloon:                          pcsys_monitor.      (line 4754)
* info block:                            pcsys_monitor.      (line 4675)
* info block-jobs:                       pcsys_monitor.      (line 4679)
* info blockstats:                       pcsys_monitor.      (line 4677)
* info capture:                          pcsys_monitor.      (line 4726)
* info chardev:                          pcsys_monitor.      (line 4673)
* info cmma:                             pcsys_monitor.      (line 4784)
* info cpus:                             pcsys_monitor.      (line 4687)
* info cpustats:                         pcsys_monitor.      (line 4742)
* info dump:                             pcsys_monitor.      (line 4787)
* info history:                          pcsys_monitor.      (line 4689)
* info hotpluggable-cpus:                pcsys_monitor.      (line 4791)
* info ioapic:                           pcsys_monitor.      (line 4685)
* info iothreads:                        pcsys_monitor.      (line 4772)
* info irq:                              pcsys_monitor.      (line 4691)
* info jit:                              pcsys_monitor.      (line 4705)
* info kvm:                              pcsys_monitor.      (line 4716)
* info lapic:                            pcsys_monitor.      (line 4683)
* info mem:                              pcsys_monitor.      (line 4701)
* info memdev:                           pcsys_monitor.      (line 4768)
* info memory-devices:                   pcsys_monitor.      (line 4770)
* info memory_size_summary:              pcsys_monitor.      (line 4795)
* info mice:                             pcsys_monitor.      (line 4732)
* info migrate:                          pcsys_monitor.      (line 4746)
* info migrate_cache_size:               pcsys_monitor.      (line 4752)
* info migrate_capabilities:             pcsys_monitor.      (line 4748)
* info migrate_parameters:               pcsys_monitor.      (line 4750)
* info mtree:                            pcsys_monitor.      (line 4703)
* info name:                             pcsys_monitor.      (line 4738)
* info network:                          pcsys_monitor.      (line 4671)
* info numa:                             pcsys_monitor.      (line 4718)
* info opcount:                          pcsys_monitor.      (line 4707)
* info pci:                              pcsys_monitor.      (line 4697)
* info pic:                              pcsys_monitor.      (line 4693)
* info profile:                          pcsys_monitor.      (line 4724)
* info qdm:                              pcsys_monitor.      (line 4758)
* info qom-tree:                         pcsys_monitor.      (line 4760)
* info qtree:                            pcsys_monitor.      (line 4756)
* info ramblock:                         pcsys_monitor.      (line 4789)
* info rdma:                             pcsys_monitor.      (line 4695)
* info registers:                        pcsys_monitor.      (line 4681)
* info rocker:                           pcsys_monitor.      (line 4774)
* info rocker-of-dpa-flows:              pcsys_monitor.      (line 4778)
* info rocker-of-dpa-groups:             pcsys_monitor.      (line 4780)
* info rocker-ports:                     pcsys_monitor.      (line 4776)
* info roms:                             pcsys_monitor.      (line 4762)
* info sev:                              pcsys_monitor.      (line 4798)
* info skeys:                            pcsys_monitor.      (line 4782)
* info snapshots:                        pcsys_monitor.      (line 4728)
* info spice:                            pcsys_monitor.      (line 4736)
* info status:                           pcsys_monitor.      (line 4730)
* info sync-profile:                     pcsys_monitor.      (line 4709)
* info tlb:                              pcsys_monitor.      (line 4699)
* info tpm:                              pcsys_monitor.      (line 4766)
* info trace-events:                     pcsys_monitor.      (line 4764)
* info usb:                              pcsys_monitor.      (line 4720)
* info usbhost:                          pcsys_monitor.      (line 4722)
* info usernet:                          pcsys_monitor.      (line 4744)
* info uuid:                             pcsys_monitor.      (line 4740)
* info version:                          pcsys_monitor.      (line 4669)
* info vm-generation-id:                 pcsys_monitor.      (line 4793)
* info vnc:                              pcsys_monitor.      (line 4734)
* loadvm:                                pcsys_monitor.      (line 4311)
* log:                                   pcsys_monitor.      (line 4301)
* logfile:                               pcsys_monitor.      (line 4294)
* mce (x86):                             pcsys_monitor.      (line 4598)
* memsave:                               pcsys_monitor.      (line 4437)
* migrate:                               pcsys_monitor.      (line 4472)
* migrate_cancel:                        pcsys_monitor.      (line 4476)
* migrate_continue:                      pcsys_monitor.      (line 4478)
* migrate_incoming:                      pcsys_monitor.      (line 4480)
* migrate_pause:                         pcsys_monitor.      (line 4485)
* migrate_recover:                       pcsys_monitor.      (line 4483)
* migrate_set_cache_size:                pcsys_monitor.      (line 4487)
* migrate_set_capability:                pcsys_monitor.      (line 4493)
* migrate_set_downtime:                  pcsys_monitor.      (line 4491)
* migrate_set_parameter:                 pcsys_monitor.      (line 4495)
* migrate_set_speed:                     pcsys_monitor.      (line 4489)
* migrate_start_postcopy:                pcsys_monitor.      (line 4497)
* migration_mode:                        pcsys_monitor.      (line 4522)
* mouse_button:                          pcsys_monitor.      (line 4420)
* mouse_move:                            pcsys_monitor.      (line 4417)
* mouse_set:                             pcsys_monitor.      (line 4422)
* nbd_server_add:                        pcsys_monitor.      (line 4586)
* nbd_server_remove:                     pcsys_monitor.      (line 4591)
* nbd_server_start:                      pcsys_monitor.      (line 4581)
* nbd_server_stop:                       pcsys_monitor.      (line 4596)
* netdev_add:                            pcsys_monitor.      (line 4540)
* netdev_del:                            pcsys_monitor.      (line 4542)
* nmi:                                   pcsys_monitor.      (line 4449)
* o:                                     pcsys_monitor.      (line 4391)
* object_add:                            pcsys_monitor.      (line 4544)
* object_del:                            pcsys_monitor.      (line 4546)
* pcie_aer_inject_error:                 pcsys_monitor.      (line 4538)
* pmemsave:                              pcsys_monitor.      (line 4439)
* print:                                 pcsys_monitor.      (line 4387)
* qemu-io:                               pcsys_monitor.      (line 4655)
* quit:                                  pcsys_monitor.      (line 4214)
* ringbuf_read:                          pcsys_monitor.      (line 4456)
* ringbuf_write:                         pcsys_monitor.      (line 4452)
* savevm:                                pcsys_monitor.      (line 4303)
* screendump:                            pcsys_monitor.      (line 4292)
* sendkey:                               pcsys_monitor.      (line 4393)
* set_link:                              pcsys_monitor.      (line 4555)
* set_password:                          pcsys_monitor.      (line 4617)
* singlestep:                            pcsys_monitor.      (line 4321)
* snapshot_blkdev:                       pcsys_monitor.      (line 4524)
* snapshot_blkdev_internal:              pcsys_monitor.      (line 4526)
* snapshot_delete_blkdev_internal:       pcsys_monitor.      (line 4528)
* stop:                                  pcsys_monitor.      (line 4324)
* stopcapture:                           pcsys_monitor.      (line 4434)
* sum:                                   pcsys_monitor.      (line 4409)
* sync-profile:                          pcsys_monitor.      (line 4402)
* system_powerdown:                      pcsys_monitor.      (line 4407)
* system_reset:                          pcsys_monitor.      (line 4405)
* system_wakeup:                         pcsys_monitor.      (line 4328)
* trace-event:                           pcsys_monitor.      (line 4296)
* trace-file:                            pcsys_monitor.      (line 4298)
* watchdog_action:                       pcsys_monitor.      (line 4557)
* wavcapture:                            pcsys_monitor.      (line 4426)
* x:                                     pcsys_monitor.      (line 4332)
* xp:                                    pcsys_monitor.      (line 4334)
* x_colo_lost_heartbeat:                 pcsys_monitor.      (line 4500)

F.3 Keystroke Index
===================

This is a list of all keystrokes which have a special function in system
emulation.

* Menu:

* Ctrl-a b:                              mux_keys.           (line 4177)
* Ctrl-a c:                              mux_keys.           (line 4179)
* Ctrl-a Ctrl-a:                         mux_keys.           (line 4182)
* Ctrl-a h:                              mux_keys.           (line 4169)
* Ctrl-a s:                              mux_keys.           (line 4173)
* Ctrl-a t:                              mux_keys.           (line 4175)
* Ctrl-a x:                              mux_keys.           (line 4171)
* Ctrl-Alt:                              pcsys_keys.         (line 4154)
* Ctrl-Alt-+:                            pcsys_keys.         (line 4136)
* Ctrl-Alt--:                            pcsys_keys.         (line 4139)
* Ctrl-Alt-f:                            pcsys_keys.         (line 4133)
* Ctrl-Alt-n:                            pcsys_keys.         (line 4145)
* Ctrl-Alt-u:                            pcsys_keys.         (line 4142)
* Ctrl-Down:                             pcsys_keys.         (line 4156)
* Ctrl-PageDown:                         pcsys_keys.         (line 4156)
* Ctrl-PageUp:                           pcsys_keys.         (line 4156)
* Ctrl-Up:                               pcsys_keys.         (line 4156)

F.4 Program Index
=================

F.5 Data Type Index
===================

This index could be used for qdev device names and options.

F.6 Variable Index
==================

Youez - 2016 - github.com/yon3zu
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