bdrv_create options specified with -o have no effect when skipping image creation with -n, so this doesn't make sense. Warn against the misuse and deprecate the combination so we can make it a hard error later. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Reviewed-by: John Snow <jsnow@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com>
341 lines
14 KiB
Plaintext
341 lines
14 KiB
Plaintext
@node Deprecated features
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@appendix Deprecated features
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In general features are intended to be supported indefinitely once
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introduced into QEMU. In the event that a feature needs to be removed,
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it will be listed in this appendix. The feature will remain functional
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for 2 releases prior to actual removal. Deprecated features may also
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generate warnings on the console when QEMU starts up, or if activated
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via a monitor command, however, this is not a mandatory requirement.
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Prior to the 2.10.0 release there was no official policy on how
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long features would be deprecated prior to their removal, nor
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any documented list of which features were deprecated. Thus
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any features deprecated prior to 2.10.0 will be treated as if
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they were first deprecated in the 2.10.0 release.
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What follows is a list of all features currently marked as
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deprecated.
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@section System emulator command line arguments
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@subsection -machine enforce-config-section=on|off (since 3.1)
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The @option{enforce-config-section} parameter is replaced by the
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@option{-global migration.send-configuration=@var{on|off}} option.
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@subsection -no-kvm (since 1.3.0)
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The ``-no-kvm'' argument is now a synonym for setting
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``-machine accel=tcg''.
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@subsection -usbdevice (since 2.10.0)
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The ``-usbdevice DEV'' argument is now a synonym for setting
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the ``-device usb-DEV'' argument instead. The deprecated syntax
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would automatically enable USB support on the machine type.
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If using the new syntax, USB support must be explicitly
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enabled via the ``-machine usb=on'' argument.
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@subsection -drive file=json:@{...@{'driver':'file'@}@} (since 3.0)
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The 'file' driver for drives is no longer appropriate for character or host
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devices and will only accept regular files (S_IFREG). The correct driver
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for these file types is 'host_cdrom' or 'host_device' as appropriate.
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@subsection -net ...,name=@var{name} (since 3.1)
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The @option{name} parameter of the @option{-net} option is a synonym
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for the @option{id} parameter, which should now be used instead.
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@subsection -smp (invalid topologies) (since 3.1)
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CPU topology properties should describe whole machine topology including
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possible CPUs.
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However, historically it was possible to start QEMU with an incorrect topology
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where @math{@var{n} <= @var{sockets} * @var{cores} * @var{threads} < @var{maxcpus}},
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which could lead to an incorrect topology enumeration by the guest.
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Support for invalid topologies will be removed, the user must ensure
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topologies described with -smp include all possible cpus, i.e.
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@math{@var{sockets} * @var{cores} * @var{threads} = @var{maxcpus}}.
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@subsection -vnc acl (since 4.0.0)
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The @code{acl} option to the @code{-vnc} argument has been replaced
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by the @code{tls-authz} and @code{sasl-authz} options.
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@subsection QEMU_AUDIO_ environment variables and -audio-help (since 4.0)
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The ``-audiodev'' argument is now the preferred way to specify audio
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backend settings instead of environment variables. To ease migration to
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the new format, the ``-audiodev-help'' option can be used to convert
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the current values of the environment variables to ``-audiodev'' options.
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@subsection -mon ...,control=readline,pretty=on|off (since 4.1)
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The @code{pretty=on|off} switch has no effect for HMP monitors, but is
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silently ignored. Using the switch with HMP monitors will become an
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error in the future.
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@subsection -realtime (since 4.1)
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The @code{-realtime mlock=on|off} argument has been replaced by the
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@code{-overcommit mem-lock=on|off} argument.
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@subsection -virtfs_synth (since 4.1)
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The ``-virtfs_synth'' argument is now deprecated. Please use ``-fsdev synth''
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and ``-device virtio-9p-...'' instead.
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@subsection -numa node,mem=@var{size} (since 4.1)
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The parameter @option{mem} of @option{-numa node} is used to assign a part of
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guest RAM to a NUMA node. But when using it, it's impossible to manage specified
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RAM chunk on the host side (like bind it to a host node, setting bind policy, ...),
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so guest end-ups with the fake NUMA configuration with suboptiomal performance.
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However since 2014 there is an alternative way to assign RAM to a NUMA node
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using parameter @option{memdev}, which does the same as @option{mem} and adds
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means to actualy manage node RAM on the host side. Use parameter @option{memdev}
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with @var{memory-backend-ram} backend as an replacement for parameter @option{mem}
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to achieve the same fake NUMA effect or a properly configured
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@var{memory-backend-file} backend to actually benefit from NUMA configuration.
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In future new machine versions will not accept the option but it will still
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work with old machine types. User can check QAPI schema to see if the legacy
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option is supported by looking at MachineInfo::numa-mem-supported property.
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@subsection -numa node (without memory specified) (since 4.1)
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Splitting RAM by default between NUMA nodes has the same issues as @option{mem}
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parameter described above with the difference that the role of the user plays
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QEMU using implicit generic or board specific splitting rule.
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Use @option{memdev} with @var{memory-backend-ram} backend or @option{mem} (if
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it's supported by used machine type) to define mapping explictly instead.
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@subsection -mem-path fallback to RAM (since 4.1)
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Currently if guest RAM allocation from file pointed by @option{mem-path}
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fails, QEMU falls back to allocating from RAM, which might result
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in unpredictable behavior since the backing file specified by the user
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is ignored. In the future, users will be responsible for making sure
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the backing storage specified with @option{-mem-path} can actually provide
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the guest RAM configured with @option{-m} and QEMU will fail to start up if
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RAM allocation is unsuccessful.
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@subsection RISC-V -bios (since 4.1)
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QEMU 4.1 introduced support for the -bios option in QEMU for RISC-V for the
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RISC-V virt machine and sifive_u machine.
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QEMU 4.1 has no changes to the default behaviour to avoid breakages. This
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default will change in a future QEMU release, so please prepare now. All users
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of the virt or sifive_u machine must change their command line usage.
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QEMU 4.1 has three options, please migrate to one of these three:
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1. ``-bios none`` - This is the current default behavior if no -bios option
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is included. QEMU will not automatically load any firmware. It is up
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to the user to load all the images they need.
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2. ``-bios default`` - In a future QEMU release this will become the default
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behaviour if no -bios option is specified. This option will load the
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default OpenSBI firmware automatically. The firmware is included with
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the QEMU release and no user interaction is required. All a user needs
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to do is specify the kernel they want to boot with the -kernel option
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3. ``-bios <file>`` - Tells QEMU to load the specified file as the firmwrae.
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@section QEMU Machine Protocol (QMP) commands
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@subsection block-dirty-bitmap-add "autoload" parameter (since 2.12.0)
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"autoload" parameter is now ignored. All bitmaps are automatically loaded
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from qcow2 images.
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@subsection query-block result field dirty-bitmaps[i].status (since 4.0)
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The ``status'' field of the ``BlockDirtyInfo'' structure, returned by
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the query-block command is deprecated. Two new boolean fields,
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``recording'' and ``busy'' effectively replace it.
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@subsection query-cpus (since 2.12.0)
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The ``query-cpus'' command is replaced by the ``query-cpus-fast'' command.
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@subsection query-cpus-fast "arch" output member (since 3.0.0)
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The ``arch'' output member of the ``query-cpus-fast'' command is
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replaced by the ``target'' output member.
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@subsection cpu-add (since 4.0)
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Use ``device_add'' for hotplugging vCPUs instead of ``cpu-add''. See
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documentation of ``query-hotpluggable-cpus'' for additional
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details.
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@subsection query-events (since 4.0)
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The ``query-events'' command has been superseded by the more powerful
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and accurate ``query-qmp-schema'' command.
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@subsection chardev client socket with 'wait' option (since 4.0)
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Character devices creating sockets in client mode should not specify
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the 'wait' field, which is only applicable to sockets in server mode
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@section Human Monitor Protocol (HMP) commands
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@subsection The hub_id parameter of 'hostfwd_add' / 'hostfwd_remove' (since 3.1)
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The @option{[hub_id name]} parameter tuple of the 'hostfwd_add' and
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'hostfwd_remove' HMP commands has been replaced by @option{netdev_id}.
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@subsection cpu-add (since 4.0)
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Use ``device_add'' for hotplugging vCPUs instead of ``cpu-add''. See
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documentation of ``query-hotpluggable-cpus'' for additional details.
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@subsection acl_show, acl_reset, acl_policy, acl_add, acl_remove (since 4.0.0)
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The ``acl_show'', ``acl_reset'', ``acl_policy'', ``acl_add'', and
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``acl_remove'' commands are deprecated with no replacement. Authorization
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for VNC should be performed using the pluggable QAuthZ objects.
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@section Guest Emulator ISAs
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@subsection RISC-V ISA privledge specification version 1.09.1 (since 4.1)
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The RISC-V ISA privledge specification version 1.09.1 has been deprecated.
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QEMU supports both the newer version 1.10.0 and the ratified version 1.11.0, these
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should be used instead of the 1.09.1 version.
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@section System emulator CPUS
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@subsection RISC-V ISA CPUs (since 4.1)
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The RISC-V cpus with the ISA version in the CPU name have been depcreated. The
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four CPUs are: ``rv32gcsu-v1.9.1``, ``rv32gcsu-v1.10.0``, ``rv64gcsu-v1.9.1`` and
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``rv64gcsu-v1.10.0``. Instead the version can be specified via the CPU ``priv_spec``
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option when using the ``rv32`` or ``rv64`` CPUs.
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@subsection RISC-V ISA CPUs (since 4.1)
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The RISC-V no MMU cpus have been depcreated. The two CPUs: ``rv32imacu-nommu`` and
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``rv64imacu-nommu`` should no longer be used. Instead the MMU status can be specified
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via the CPU ``mmu`` option when using the ``rv32`` or ``rv64`` CPUs.
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@section System emulator devices
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@subsection bluetooth (since 3.1)
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The bluetooth subsystem is unmaintained since many years and likely bitrotten
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quite a bit. It will be removed without replacement unless some users speaks
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up at the @email{qemu-devel@@nongnu.org} mailing list with information about
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their usecases.
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@section System emulator machines
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@subsection pc-0.12, pc-0.13, pc-0.14 and pc-0.15 (since 4.0)
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These machine types are very old and likely can not be used for live migration
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from old QEMU versions anymore. A newer machine type should be used instead.
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@subsection prep (PowerPC) (since 3.1)
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This machine type uses an unmaintained firmware, broken in lots of ways,
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and unable to start post-2004 operating systems. 40p machine type should be
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used instead.
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@subsection spike_v1.9.1 and spike_v1.10 (since 4.1)
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The version specific Spike machines have been deprecated in favour of the
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generic ``spike`` machine. If you need to specify an older version of the RISC-V
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spec you can use the ``-cpu rv64gcsu,priv_spec=v1.9.1`` command line argument.
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@section Device options
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@subsection Block device options
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@subsubsection "backing": "" (since 2.12.0)
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In order to prevent QEMU from automatically opening an image's backing
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chain, use ``"backing": null'' instead.
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@subsubsection rbd keyvalue pair encoded filenames: "" (since 3.1.0)
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Options for ``rbd'' should be specified according to its runtime options,
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like other block drivers. Legacy parsing of keyvalue pair encoded
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filenames is useful to open images with the old format for backing files;
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These image files should be updated to use the current format.
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Example of legacy encoding:
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@code{json:@{"file.driver":"rbd", "file.filename":"rbd:rbd/name"@}}
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The above, converted to the current supported format:
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@code{json:@{"file.driver":"rbd", "file.pool":"rbd", "file.image":"name"@}}
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@section Related binaries
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@subsection qemu-nbd --partition (since 4.0.0)
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The ``qemu-nbd --partition $digit'' code (also spelled @option{-P})
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can only handle MBR partitions, and has never correctly handled
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logical partitions beyond partition 5. If you know the offset and
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length of the partition (perhaps by using @code{sfdisk} within the
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guest), you can achieve the effect of exporting just that subset of
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the disk by use of the @option{--image-opts} option with a raw
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blockdev using the @code{offset} and @code{size} parameters layered on
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top of any other existing blockdev. For example, if partition 1 is
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100MiB long starting at 1MiB, the old command:
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@code{qemu-nbd -t -P 1 -f qcow2 file.qcow2}
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can be rewritten as:
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@code{qemu-nbd -t --image-opts driver=raw,offset=1M,size=100M,file.driver=qcow2,file.backing.driver=file,file.backing.filename=file.qcow2}
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Alternatively, the @code{nbdkit} project provides a more powerful
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partition filter on top of its nbd plugin, which can be used to select
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an arbitrary MBR or GPT partition on top of any other full-image NBD
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export. Using this to rewrite the above example results in:
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@code{qemu-nbd -t -k /tmp/sock -f qcow2 file.qcow2 &}
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@code{nbdkit -f --filter=partition nbd socket=/tmp/sock partition=1}
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Note that if you are exposing the export via /dev/nbd0, it is easier
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to just export the entire image and then mount only /dev/nbd0p1 than
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it is to reinvoke @command{qemu-nbd -c /dev/nbd0} limited to just a
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subset of the image.
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@subsection qemu-img convert -n -o (since 4.2.0)
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All options specified in @option{-o} are image creation options, so
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they have no effect when used with @option{-n} to skip image creation.
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Silently ignored options can be confusing, so this combination of
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options will be made an error in future versions.
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@section Build system
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@subsection Python 2 support (since 4.1.0)
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In the future, QEMU will require Python 3 to be available at
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build time. Support for Python 2 in scripts shipped with QEMU
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is deprecated.
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@section Backwards compatibility
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@subsection Runnability guarantee of CPU models (since 4.1.0)
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Previous versions of QEMU never changed existing CPU models in
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ways that introduced additional host software or hardware
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requirements to the VM. This allowed management software to
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safely change the machine type of an existing VM without
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introducing new requirements ("runnability guarantee"). This
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prevented CPU models from being updated to include CPU
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vulnerability mitigations, leaving guests vulnerable in the
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default configuration.
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The CPU model runnability guarantee won't apply anymore to
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existing CPU models. Management software that needs runnability
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guarantees must resolve the CPU model aliases using te
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``alias-of'' field returned by the ``query-cpu-definitions'' QMP
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command.
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