docs/about/deprecated.rst - qemu - Git at Google

 .. _Deprecated features:

 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 section. The feature will remain functional for the
 release in which it was deprecated and one further release. After these two
 releases, the feature is liable to be removed. 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.

 System emulator command line arguments
 --------------------------------------

 ``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.

 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=`` property if you plan to
 transmit audio through the VNC protocol.

 Creating sound card devices using ``-soundhw`` (since 5.1)
 ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

 Sound card devices should be created using ``-device`` instead.  The
 names are the same for most devices.  The exceptions are ``hda`` which
 needs two devices (``-device intel-hda -device hda-duplex``) and
 ``pcspk`` which can be activated using ``-machine
 pcspk-audiodev=<name>``.

 ``-chardev`` backend aliases ``tty`` and ``parport`` (since 6.0)
 ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

 ``tty`` and ``parport`` are aliases that will be removed. Instead, the
 actual backend names ``serial`` and ``parallel`` should be used.

 Short-form boolean options (since 6.0)
 ''''''''''''''''''''''''''''''''''''''

 Boolean options such as ``share=on``/``share=off`` could be written
 in short form as ``share`` and ``noshare``.  This is now deprecated
 and will cause a warning.

 ``delay`` option for socket character devices (since 6.0)
 '''''''''''''''''''''''''''''''''''''''''''''''''''''''''

 The replacement for the ``nodelay`` short-form boolean option is ``nodelay=on``
 rather than ``delay=off``.

 ``--enable-fips`` (since 6.0)
 '''''''''''''''''''''''''''''

 This option restricts usage of certain cryptographic algorithms when
 the host is operating in FIPS mode.

 If FIPS compliance is required, QEMU should be built with the ``libgcrypt``
 library enabled as a cryptography provider.

 Neither the ``nettle`` library, or the built-in cryptography provider are
 supported on FIPS enabled hosts.

 ``-writeconfig`` (since 6.0)
 '''''''''''''''''''''''''''''

 The ``-writeconfig`` option is not able to serialize the entire contents
 of the QEMU command line.  It is thus considered a failed experiment
 and deprecated, with no current replacement.

 Userspace local APIC with KVM (x86, since 6.0)
 ''''''''''''''''''''''''''''''''''''''''''''''

 Using ``-M kernel-irqchip=off`` with x86 machine types that include a local
 APIC is deprecated.  The ``split`` setting is supported, as is using
 ``-M kernel-irqchip=off`` with the ISA PC machine type.

 hexadecimal sizes with scaling multipliers (since 6.0)
 ''''''''''''''''''''''''''''''''''''''''''''''''''''''

 Input parameters that take a size value should only use a size suffix
 (such as 'k' or 'M') when the base is written in decimal, and not when
 the value is hexadecimal.  That is, '0x20M' is deprecated, and should
 be written either as '32M' or as '0x2000000'.

 ``-spice password=string`` (since 6.0)
 ''''''''''''''''''''''''''''''''''''''

 This option is insecure because the SPICE password remains visible in
 the process listing. This is replaced by the new ``password-secret``
 option which lets the password be securely provided on the command
 line using a ``secret`` object instance.

 ``opened`` property of ``rng-*`` objects (since 6.0)
 ''''''''''''''''''''''''''''''''''''''''''''''''''''

 The only effect of specifying ``opened=on`` in the command line or QMP
 ``object-add`` is that the device is opened immediately, possibly before all
 other options have been processed.  This will either have no effect (if
 ``opened`` was the last option) or cause errors.  The property is therefore
 useless and should not be specified.

 ``loaded`` property of ``secret`` and ``secret_keyring`` objects (since 6.0)
 ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

 The only effect of specifying ``loaded=on`` in the command line or QMP
 ``object-add`` is that the secret is loaded immediately, possibly before all
 other options have been processed.  This will either have no effect (if
 ``loaded`` was the last option) or cause options to be effectively ignored as
 if they were not given.  The property is therefore useless and should not be
 specified.

 ``-display sdl,window_close=...`` (since 6.1)
 '''''''''''''''''''''''''''''''''''''''''''''

 Use ``-display sdl,window-close=...`` instead (i.e. with a minus instead of
 an underscore between "window" and "close").

 ``-no-quit`` (since 6.1)
 ''''''''''''''''''''''''

 The ``-no-quit`` is a synonym for ``-display ...,window-close=off`` which
 should be used instead.

 ``-alt-grab`` and ``-display sdl,alt_grab=on`` (since 6.2)
 ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

 Use ``-display sdl,grab-mod=lshift-lctrl-lalt`` instead.

 ``-ctrl-grab`` and ``-display sdl,ctrl_grab=on`` (since 6.2)
 ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

 Use ``-display sdl,grab-mod=rctrl`` instead.

 ``-sdl`` (since 6.2)
 ''''''''''''''''''''

 Use ``-display sdl`` instead.

 ``-curses`` (since 6.2)
 '''''''''''''''''''''''

 Use ``-display curses`` instead.


 Plugin argument passing through ``arg=<string>`` (since 6.1)
 ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

 Passing TCG plugins arguments through ``arg=`` is redundant is makes the
 command-line less readable, especially when the argument itself consist of a
 name and a value, e.g. ``-plugin plugin_name,arg="arg_name=arg_value"``.
 Therefore, the usage of ``arg`` is redundant. Single-word arguments are treated
 as short-form boolean values, and passed to plugins as ``arg_name=on``.
 However, short-form booleans are deprecated and full explicit ``arg_name=on``
 form is preferred.


 QEMU Machine Protocol (QMP) commands
 ------------------------------------

 ``blockdev-open-tray``, ``blockdev-close-tray`` argument ``device`` (since 2.8)
 '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

 Use argument ``id`` instead.

 ``eject`` argument ``device`` (since 2.8)
 '''''''''''''''''''''''''''''''''''''''''

 Use argument ``id`` instead.

 ``blockdev-change-medium`` argument ``device`` (since 2.8)
 ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

 Use argument ``id`` instead.

 ``block_set_io_throttle`` argument ``device`` (since 2.8)
 '''''''''''''''''''''''''''''''''''''''''''''''''''''''''

 Use argument ``id`` instead.

 ``blockdev-add`` empty string argument ``backing`` (since 2.10)
 '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

 Use argument value ``null`` instead.

 ``block-commit`` arguments ``base`` and ``top`` (since 3.1)
 '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

 Use arguments ``base-node`` and ``top-node`` instead.

 ``nbd-server-add`` and ``nbd-server-remove`` (since 5.2)
 ''''''''''''''''''''''''''''''''''''''''''''''''''''''''

 Use the more generic commands ``block-export-add`` and ``block-export-del``
 instead.  As part of this deprecation, where ``nbd-server-add`` used a
 single ``bitmap``, the new ``block-export-add`` uses a list of ``bitmaps``.

 System accelerators
 -------------------

 MIPS ``Trap-and-Emul`` KVM support (since 6.0)
 ''''''''''''''''''''''''''''''''''''''''''''''

 The MIPS ``Trap-and-Emul`` KVM host and guest support has been removed
 from Linux upstream kernel, declare it deprecated.

 System emulator CPUS
 --------------------

 ``Icelake-Client`` CPU Model (since 5.2)
 ''''''''''''''''''''''''''''''''''''''''

 ``Icelake-Client`` CPU Models are deprecated. Use ``Icelake-Server`` CPU
 Models instead.

 MIPS ``I7200`` CPU Model (since 5.2)
 ''''''''''''''''''''''''''''''''''''

 The ``I7200`` guest CPU relies on the nanoMIPS ISA, which is deprecated
 (the ISA has never been upstreamed to a compiler toolchain). Therefore
 this CPU is also deprecated.

 System emulator machines
 ------------------------

 Aspeed ``swift-bmc`` machine (since 6.1)
 ''''''''''''''''''''''''''''''''''''''''

 This machine is deprecated because we have enough AST2500 based OpenPOWER
 machines. It can be easily replaced by the ``witherspoon-bmc`` or the
 ``romulus-bmc`` machines.

 Backend options
 ---------------

 Using non-persistent backing file with pmem=on (since 6.1)
 ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

 This option is used when ``memory-backend-file`` is consumed by emulated NVDIMM
 device. However enabling ``memory-backend-file.pmem`` option, when backing file
 is (a) not DAX capable or (b) not on a filesystem that support direct mapping
 of persistent memory, is not safe and may lead to data loss or corruption in case
 of host crash.
 Options are:

     - modify VM configuration to set ``pmem=off`` to continue using fake NVDIMM
       (without persistence guaranties) with backing file on non DAX storage
     - move backing file to NVDIMM storage and keep ``pmem=on``
       (to have NVDIMM with persistence guaranties).

 Device options
 --------------

 Emulated device options
 '''''''''''''''''''''''

 ``-device virtio-blk,scsi=on|off`` (since 5.0)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

 The virtio-blk SCSI passthrough feature is a legacy VIRTIO feature.  VIRTIO 1.0
 and later do not support it because the virtio-scsi device was introduced for
 full SCSI support.  Use virtio-scsi instead when SCSI passthrough is required.

 Note this also applies to ``-device virtio-blk-pci,scsi=on|off``, which is an
 alias.

 Block device options
 ''''''''''''''''''''

 ``"backing": ""`` (since 2.12)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

 In order to prevent QEMU from automatically opening an image's backing
 chain, use ``"backing": null`` instead.

 ``rbd`` keyvalue pair encoded filenames: ``""`` (since 3.1)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

 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"}

 linux-user mode CPUs
 --------------------

 ``ppc64abi32`` CPUs (since 5.2)
 '''''''''''''''''''''''''''''''

 The ``ppc64abi32`` architecture has a number of issues which regularly
 trip up our CI testing and is suspected to be quite broken. For that
 reason the maintainers strongly suspect no one actually uses it.

 MIPS ``I7200`` CPU (since 5.2)
 ''''''''''''''''''''''''''''''

 The ``I7200`` guest CPU relies on the nanoMIPS ISA, which is deprecated
 (the ISA has never been upstreamed to a compiler toolchain). Therefore
 this CPU is also deprecated.

 Related binaries
 ----------------

 Backwards compatibility
 -----------------------

 Runnability guarantee of CPU models (since 4.1)
 '''''''''''''''''''''''''''''''''''''''''''''''

 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 the
 ``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.

 Guest Emulator ISAs
 -------------------

 nanoMIPS ISA
 ''''''''''''

 The ``nanoMIPS`` ISA has never been upstreamed to any compiler toolchain.
 As it is hard to generate binaries for it, declare it deprecated.
	.. _Deprecated features:

	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 section. The feature will remain functional for the
	release in which it was deprecated and one further release. After these two
	releases, the feature is liable to be removed. 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.

	System emulator command line arguments
	--------------------------------------

	``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.

	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=`` property if you plan to
	transmit audio through the VNC protocol.

	Creating sound card devices using ``-soundhw`` (since 5.1)
	''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

	Sound card devices should be created using ``-device`` instead. The
	names are the same for most devices. The exceptions are ``hda`` which
	needs two devices (``-device intel-hda -device hda-duplex``) and
	``pcspk`` which can be activated using ``-machine
	pcspk-audiodev=<name>``.

	``-chardev`` backend aliases ``tty`` and ``parport`` (since 6.0)
	''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

	``tty`` and ``parport`` are aliases that will be removed. Instead, the
	actual backend names ``serial`` and ``parallel`` should be used.

	Short-form boolean options (since 6.0)
	''''''''''''''''''''''''''''''''''''''

	Boolean options such as ``share=on``/``share=off`` could be written
	in short form as ``share`` and ``noshare``. This is now deprecated
	and will cause a warning.

	``delay`` option for socket character devices (since 6.0)
	'''''''''''''''''''''''''''''''''''''''''''''''''''''''''

	The replacement for the ``nodelay`` short-form boolean option is ``nodelay=on``
	rather than ``delay=off``.

	``--enable-fips`` (since 6.0)
	'''''''''''''''''''''''''''''

	This option restricts usage of certain cryptographic algorithms when
	the host is operating in FIPS mode.

	If FIPS compliance is required, QEMU should be built with the ``libgcrypt``
	library enabled as a cryptography provider.

	Neither the ``nettle`` library, or the built-in cryptography provider are
	supported on FIPS enabled hosts.

	``-writeconfig`` (since 6.0)
	'''''''''''''''''''''''''''''

	The ``-writeconfig`` option is not able to serialize the entire contents
	of the QEMU command line. It is thus considered a failed experiment
	and deprecated, with no current replacement.

	Userspace local APIC with KVM (x86, since 6.0)
	''''''''''''''''''''''''''''''''''''''''''''''

	Using ``-M kernel-irqchip=off`` with x86 machine types that include a local
	APIC is deprecated. The ``split`` setting is supported, as is using
	``-M kernel-irqchip=off`` with the ISA PC machine type.

	hexadecimal sizes with scaling multipliers (since 6.0)
	''''''''''''''''''''''''''''''''''''''''''''''''''''''

	Input parameters that take a size value should only use a size suffix
	(such as 'k' or 'M') when the base is written in decimal, and not when
	the value is hexadecimal. That is, '0x20M' is deprecated, and should
	be written either as '32M' or as '0x2000000'.

	``-spice password=string`` (since 6.0)
	''''''''''''''''''''''''''''''''''''''

	This option is insecure because the SPICE password remains visible in
	the process listing. This is replaced by the new ``password-secret``
	option which lets the password be securely provided on the command
	line using a ``secret`` object instance.

	``opened`` property of ``rng-*`` objects (since 6.0)
	''''''''''''''''''''''''''''''''''''''''''''''''''''

	The only effect of specifying ``opened=on`` in the command line or QMP
	``object-add`` is that the device is opened immediately, possibly before all
	other options have been processed. This will either have no effect (if
	``opened`` was the last option) or cause errors. The property is therefore
	useless and should not be specified.

	``loaded`` property of ``secret`` and ``secret_keyring`` objects (since 6.0)
	''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

	The only effect of specifying ``loaded=on`` in the command line or QMP
	``object-add`` is that the secret is loaded immediately, possibly before all
	other options have been processed. This will either have no effect (if
	``loaded`` was the last option) or cause options to be effectively ignored as
	if they were not given. The property is therefore useless and should not be
	specified.

	``-display sdl,window_close=...`` (since 6.1)
	'''''''''''''''''''''''''''''''''''''''''''''

	Use ``-display sdl,window-close=...`` instead (i.e. with a minus instead of
	an underscore between "window" and "close").

	``-no-quit`` (since 6.1)
	''''''''''''''''''''''''

	The ``-no-quit`` is a synonym for ``-display ...,window-close=off`` which
	should be used instead.

	``-alt-grab`` and ``-display sdl,alt_grab=on`` (since 6.2)
	''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

	Use ``-display sdl,grab-mod=lshift-lctrl-lalt`` instead.

	``-ctrl-grab`` and ``-display sdl,ctrl_grab=on`` (since 6.2)
	''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

	Use ``-display sdl,grab-mod=rctrl`` instead.

	``-sdl`` (since 6.2)
	''''''''''''''''''''

	Use ``-display sdl`` instead.

	``-curses`` (since 6.2)
	'''''''''''''''''''''''

	Use ``-display curses`` instead.


	Plugin argument passing through ``arg=<string>`` (since 6.1)
	''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

	Passing TCG plugins arguments through ``arg=`` is redundant is makes the
	command-line less readable, especially when the argument itself consist of a
	name and a value, e.g. ``-plugin plugin_name,arg="arg_name=arg_value"``.
	Therefore, the usage of ``arg`` is redundant. Single-word arguments are treated
	as short-form boolean values, and passed to plugins as ``arg_name=on``.
	However, short-form booleans are deprecated and full explicit ``arg_name=on``
	form is preferred.


	QEMU Machine Protocol (QMP) commands
	------------------------------------

	``blockdev-open-tray``, ``blockdev-close-tray`` argument ``device`` (since 2.8)
	'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

	Use argument ``id`` instead.

	``eject`` argument ``device`` (since 2.8)
	'''''''''''''''''''''''''''''''''''''''''

	Use argument ``id`` instead.

	``blockdev-change-medium`` argument ``device`` (since 2.8)
	''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

	Use argument ``id`` instead.

	``block_set_io_throttle`` argument ``device`` (since 2.8)
	'''''''''''''''''''''''''''''''''''''''''''''''''''''''''

	Use argument ``id`` instead.

	``blockdev-add`` empty string argument ``backing`` (since 2.10)
	'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

	Use argument value ``null`` instead.

	``block-commit`` arguments ``base`` and ``top`` (since 3.1)
	'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

	Use arguments ``base-node`` and ``top-node`` instead.

	``nbd-server-add`` and ``nbd-server-remove`` (since 5.2)
	''''''''''''''''''''''''''''''''''''''''''''''''''''''''

	Use the more generic commands ``block-export-add`` and ``block-export-del``
	instead. As part of this deprecation, where ``nbd-server-add`` used a
	single ``bitmap``, the new ``block-export-add`` uses a list of ``bitmaps``.

	System accelerators
	-------------------

	MIPS ``Trap-and-Emul`` KVM support (since 6.0)
	''''''''''''''''''''''''''''''''''''''''''''''

	The MIPS ``Trap-and-Emul`` KVM host and guest support has been removed
	from Linux upstream kernel, declare it deprecated.

	System emulator CPUS
	--------------------

	``Icelake-Client`` CPU Model (since 5.2)
	''''''''''''''''''''''''''''''''''''''''

	``Icelake-Client`` CPU Models are deprecated. Use ``Icelake-Server`` CPU
	Models instead.

	MIPS ``I7200`` CPU Model (since 5.2)
	''''''''''''''''''''''''''''''''''''

	The ``I7200`` guest CPU relies on the nanoMIPS ISA, which is deprecated
	(the ISA has never been upstreamed to a compiler toolchain). Therefore
	this CPU is also deprecated.

	System emulator machines
	------------------------

	Aspeed ``swift-bmc`` machine (since 6.1)
	''''''''''''''''''''''''''''''''''''''''

	This machine is deprecated because we have enough AST2500 based OpenPOWER
	machines. It can be easily replaced by the ``witherspoon-bmc`` or the
	``romulus-bmc`` machines.

	Backend options
	---------------

	Using non-persistent backing file with pmem=on (since 6.1)
	''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

	This option is used when ``memory-backend-file`` is consumed by emulated NVDIMM
	device. However enabling ``memory-backend-file.pmem`` option, when backing file
	is (a) not DAX capable or (b) not on a filesystem that support direct mapping
	of persistent memory, is not safe and may lead to data loss or corruption in case
	of host crash.
	Options are:

	- modify VM configuration to set ``pmem=off`` to continue using fake NVDIMM
	(without persistence guaranties) with backing file on non DAX storage
	- move backing file to NVDIMM storage and keep ``pmem=on``
	(to have NVDIMM with persistence guaranties).

	Device options
	--------------

	Emulated device options
	'''''''''''''''''''''''

	``-device virtio-blk,scsi=on\|off`` (since 5.0)
	^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

	The virtio-blk SCSI passthrough feature is a legacy VIRTIO feature. VIRTIO 1.0
	and later do not support it because the virtio-scsi device was introduced for
	full SCSI support. Use virtio-scsi instead when SCSI passthrough is required.

	Note this also applies to ``-device virtio-blk-pci,scsi=on\|off``, which is an
	alias.

	Block device options
	''''''''''''''''''''

	``"backing": ""`` (since 2.12)
	^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

	In order to prevent QEMU from automatically opening an image's backing
	chain, use ``"backing": null`` instead.

	``rbd`` keyvalue pair encoded filenames: ``""`` (since 3.1)
	^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

	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"}

	linux-user mode CPUs
	--------------------

	``ppc64abi32`` CPUs (since 5.2)
	'''''''''''''''''''''''''''''''

	The ``ppc64abi32`` architecture has a number of issues which regularly
	trip up our CI testing and is suspected to be quite broken. For that
	reason the maintainers strongly suspect no one actually uses it.

	MIPS ``I7200`` CPU (since 5.2)
	''''''''''''''''''''''''''''''

	The ``I7200`` guest CPU relies on the nanoMIPS ISA, which is deprecated
	(the ISA has never been upstreamed to a compiler toolchain). Therefore
	this CPU is also deprecated.

	Related binaries
	----------------

	Backwards compatibility
	-----------------------

	Runnability guarantee of CPU models (since 4.1)
	'''''''''''''''''''''''''''''''''''''''''''''''

	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 the
	``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.

	Guest Emulator ISAs
	-------------------

	nanoMIPS ISA
	''''''''''''

	The ``nanoMIPS`` ISA has never been upstreamed to any compiler toolchain.
	As it is hard to generate binaries for it, declare it deprecated.