docs/system/removed-features.rst - qemu - Git at Google


 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.

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

 ``-net ...,name=``\ *name* (removed in 5.1)
 '''''''''''''''''''''''''''''''''''''''''''

 The ``name`` parameter of the ``-net`` option was a synonym
 for the ``id`` parameter, which should now be used instead.

 ``-no-kvm`` (removed in 5.2)
 ''''''''''''''''''''''''''''

 The ``-no-kvm`` argument was a synonym for setting ``-machine accel=tcg``.

 ``-realtime`` (removed in 6.0)
 ''''''''''''''''''''''''''''''

 The ``-realtime mlock=on|off`` argument has been replaced by the
 ``-overcommit mem-lock=on|off`` argument.

 ``-show-cursor`` option (since 5.0)
 '''''''''''''''''''''''''''''''''''

 Use ``-display sdl,show-cursor=on``, ``-display gtk,show-cursor=on``
 or ``-display default,show-cursor=on`` instead.

 ``-tb-size`` option (removed in 6.0)
 ''''''''''''''''''''''''''''''''''''

 QEMU 5.0 introduced an alternative syntax to specify the size of the translation
 block cache, ``-accel tcg,tb-size=``.

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

 ``block-dirty-bitmap-add`` "autoload" parameter (removed in 4.2.0)
 ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

 The "autoload" parameter has been ignored since 2.12.0. All bitmaps
 are automatically loaded from qcow2 images.

 ``cpu-add`` (removed in 5.2)
 ''''''''''''''''''''''''''''

 Use ``device_add`` for hotplugging vCPUs instead of ``cpu-add``.  See
 documentation of ``query-hotpluggable-cpus`` for additional details.

 Human Monitor Protocol (HMP) commands
 -------------------------------------

 The ``hub_id`` parameter of ``hostfwd_add`` / ``hostfwd_remove`` (removed in 5.0)
 '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

 The ``[hub_id name]`` parameter tuple of the 'hostfwd_add' and
 'hostfwd_remove' HMP commands has been replaced by ``netdev_id``.

 ``cpu-add`` (removed in 5.2)
 ''''''''''''''''''''''''''''

 Use ``device_add`` for hotplugging vCPUs instead of ``cpu-add``.  See
 documentation of ``query-hotpluggable-cpus`` for additional details.

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

 RISC-V ISA privilege specification version 1.09.1 (removed in 5.1)
 ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

 The RISC-V ISA privilege specification version 1.09.1 has been removed.
 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.

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

 KVM guest support on 32-bit Arm hosts (removed in 5.2)
 ''''''''''''''''''''''''''''''''''''''''''''''''''''''

 The Linux kernel has dropped support for allowing 32-bit Arm systems
 to host KVM guests as of the 5.7 kernel. Accordingly, QEMU is deprecating
 its support for this configuration and will remove it in a future version.
 Running 32-bit guests on a 64-bit Arm host remains supported.

 RISC-V ISA Specific CPUs (removed in 5.1)
 '''''''''''''''''''''''''''''''''''''''''

 The RISC-V cpus with the ISA version in the CPU name have been removed. 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.

 RISC-V no MMU CPUs (removed in 5.1)
 '''''''''''''''''''''''''''''''''''

 The RISC-V no MMU cpus have been removed. The two CPUs: ``rv32imacu-nommu`` and
 ``rv64imacu-nommu`` can no longer be used. Instead the MMU status can be specified
 via the CPU ``mmu`` option when using the ``rv32`` or ``rv64`` CPUs.

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

 ``spike_v1.9.1`` and ``spike_v1.10`` (removed in 5.1)
 '''''''''''''''''''''''''''''''''''''''''''''''''''''

 The version specific Spike machines have been removed 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=v1.10.0`` command line argument.

 mips ``r4k`` platform (removed in 5.2)
 ''''''''''''''''''''''''''''''''''''''

 This machine type was very old and unmaintained. Users should use the ``malta``
 machine type instead.

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

 ``qemu-nbd --partition`` (removed in 5.0)
 '''''''''''''''''''''''''''''''''''''''''

 The ``qemu-nbd --partition $digit`` code (also spelled ``-P``)
 could only handle MBR partitions, and never correctly handled logical
 partitions beyond partition 5.  Exporting a partition can still be
 done by utilizing 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.file.driver=file,file.file.filename=file.qcow2

 ``qemu-img convert -n -o`` (removed in 5.1)
 '''''''''''''''''''''''''''''''''''''''''''

 All options specified in ``-o`` are image creation options, so
 they are now rejected when used with ``-n`` to skip image creation.


 ``qemu-img create -b bad file $size`` (removed in 5.1)
 ''''''''''''''''''''''''''''''''''''''''''''''''''''''

 When creating an image with a backing file that could not be opened,
 ``qemu-img create`` used to issue a warning about the failure but
 proceed with the image creation if an explicit size was provided.
 However, as the ``-u`` option exists for this purpose, it is safer to
 enforce that any failure to open the backing image (including if the
 backing file is missing or an incorrect format was specified) is an
 error when ``-u`` is not used.

 Command line options
 --------------------

 ``-smp`` (invalid topologies) (removed 5.2)
 '''''''''''''''''''''''''''''''''''''''''''

 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 is removed, the user must ensure
 topologies described with -smp include all possible cpus, i.e.
 *sockets* * *cores* * *threads* = *maxcpus*.

 ``-numa`` node (without memory specified) (removed 5.2)
 '''''''''''''''''''''''''''''''''''''''''''''''''''''''

 Splitting RAM by default between NUMA nodes had the same issues as ``mem``
 parameter 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 explicitly instead.
 Users of existing VMs, wishing to preserve the same RAM distribution, should
 configure it explicitly using ``-numa node,memdev`` options. Current RAM
 distribution can be retrieved using HMP command ``info numa`` and if separate
 memory devices (pc|nv-dimm) are present use ``info memory-device`` and subtract
 device memory from output of ``info numa``.

 ``-numa node,mem=``\ *size* (removed in 5.1)
 ''''''''''''''''''''''''''''''''''''''''''''

 The parameter ``mem`` of ``-numa node`` was used to assign a part of
 guest RAM to a NUMA node. But when using it, it's impossible to manage a specified
 RAM chunk on the host side (like bind it to a host node, setting bind policy, ...),
 so the guest ends up 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 actually manage node RAM on the host side. Use parameter ``memdev``
 with *memory-backend-ram* backend as 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.
 New machine versions (since 5.1) will not accept the option but it will still
 work with old machine types. User can check the QAPI schema to see if the legacy
 option is supported by looking at MachineInfo::numa-mem-supported property.

 ``-mem-path`` fallback to RAM (removed in 5.0)
 ''''''''''''''''''''''''''''''''''''''''''''''

 If guest RAM allocation from file pointed by ``mem-path`` failed,
 QEMU was falling back to allocating from RAM, which might have resulted
 in unpredictable behavior since the backing file specified by the user
 as ignored. Currently, users are responsible for making sure the backing storage
 specified with ``-mem-path`` can actually provide the guest RAM configured with
 ``-m`` and QEMU fails to start up if RAM allocation is unsuccessful.

 ``-smp`` (invalid topologies) (removed 5.2)
 '''''''''''''''''''''''''''''''''''''''''''

 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 is removed, the user must ensure
 topologies described with -smp include all possible cpus, i.e.
 *sockets* * *cores* * *threads* = *maxcpus*.

 ``-machine enforce-config-section=on|off`` (removed 5.2)
 ''''''''''''''''''''''''''''''''''''''''''''''''''''''''

 The ``enforce-config-section`` property was replaced by the
 ``-global migration.send-configuration={on|off}`` option.

 Block devices
 -------------

 VXHS backend (removed in 5.1)
 '''''''''''''''''''''''''''''

 The VXHS code did not compile since v2.12.0. It was removed in 5.1.

	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.

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

	``-net ...,name=``\ name (removed in 5.1)
	'''''''''''''''''''''''''''''''''''''''''''

	The ``name`` parameter of the ``-net`` option was a synonym
	for the ``id`` parameter, which should now be used instead.

	``-no-kvm`` (removed in 5.2)
	''''''''''''''''''''''''''''

	The ``-no-kvm`` argument was a synonym for setting ``-machine accel=tcg``.

	``-realtime`` (removed in 6.0)
	''''''''''''''''''''''''''''''

	The ``-realtime mlock=on\|off`` argument has been replaced by the
	``-overcommit mem-lock=on\|off`` argument.

	``-show-cursor`` option (since 5.0)
	'''''''''''''''''''''''''''''''''''

	Use ``-display sdl,show-cursor=on``, ``-display gtk,show-cursor=on``
	or ``-display default,show-cursor=on`` instead.

	``-tb-size`` option (removed in 6.0)
	''''''''''''''''''''''''''''''''''''

	QEMU 5.0 introduced an alternative syntax to specify the size of the translation
	block cache, ``-accel tcg,tb-size=``.

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

	``block-dirty-bitmap-add`` "autoload" parameter (removed in 4.2.0)
	''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

	The "autoload" parameter has been ignored since 2.12.0. All bitmaps
	are automatically loaded from qcow2 images.

	``cpu-add`` (removed in 5.2)
	''''''''''''''''''''''''''''

	Use ``device_add`` for hotplugging vCPUs instead of ``cpu-add``. See
	documentation of ``query-hotpluggable-cpus`` for additional details.

	Human Monitor Protocol (HMP) commands
	-------------------------------------

	The ``hub_id`` parameter of ``hostfwd_add`` / ``hostfwd_remove`` (removed in 5.0)
	'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

	The ``[hub_id name]`` parameter tuple of the 'hostfwd_add' and
	'hostfwd_remove' HMP commands has been replaced by ``netdev_id``.

	``cpu-add`` (removed in 5.2)
	''''''''''''''''''''''''''''

	Use ``device_add`` for hotplugging vCPUs instead of ``cpu-add``. See
	documentation of ``query-hotpluggable-cpus`` for additional details.

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

	RISC-V ISA privilege specification version 1.09.1 (removed in 5.1)
	''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

	The RISC-V ISA privilege specification version 1.09.1 has been removed.
	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.

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

	KVM guest support on 32-bit Arm hosts (removed in 5.2)
	''''''''''''''''''''''''''''''''''''''''''''''''''''''

	The Linux kernel has dropped support for allowing 32-bit Arm systems
	to host KVM guests as of the 5.7 kernel. Accordingly, QEMU is deprecating
	its support for this configuration and will remove it in a future version.
	Running 32-bit guests on a 64-bit Arm host remains supported.

	RISC-V ISA Specific CPUs (removed in 5.1)
	'''''''''''''''''''''''''''''''''''''''''

	The RISC-V cpus with the ISA version in the CPU name have been removed. 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.

	RISC-V no MMU CPUs (removed in 5.1)
	'''''''''''''''''''''''''''''''''''

	The RISC-V no MMU cpus have been removed. The two CPUs: ``rv32imacu-nommu`` and
	``rv64imacu-nommu`` can no longer be used. Instead the MMU status can be specified
	via the CPU ``mmu`` option when using the ``rv32`` or ``rv64`` CPUs.

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

	``spike_v1.9.1`` and ``spike_v1.10`` (removed in 5.1)
	'''''''''''''''''''''''''''''''''''''''''''''''''''''

	The version specific Spike machines have been removed 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=v1.10.0`` command line argument.

	mips ``r4k`` platform (removed in 5.2)
	''''''''''''''''''''''''''''''''''''''

	This machine type was very old and unmaintained. Users should use the ``malta``
	machine type instead.

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

	``qemu-nbd --partition`` (removed in 5.0)
	'''''''''''''''''''''''''''''''''''''''''

	The ``qemu-nbd --partition $digit`` code (also spelled ``-P``)
	could only handle MBR partitions, and never correctly handled logical
	partitions beyond partition 5. Exporting a partition can still be
	done by utilizing 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.file.driver=file,file.file.filename=file.qcow2

	``qemu-img convert -n -o`` (removed in 5.1)
	'''''''''''''''''''''''''''''''''''''''''''

	All options specified in ``-o`` are image creation options, so
	they are now rejected when used with ``-n`` to skip image creation.


	``qemu-img create -b bad file $size`` (removed in 5.1)
	''''''''''''''''''''''''''''''''''''''''''''''''''''''

	When creating an image with a backing file that could not be opened,
	``qemu-img create`` used to issue a warning about the failure but
	proceed with the image creation if an explicit size was provided.
	However, as the ``-u`` option exists for this purpose, it is safer to
	enforce that any failure to open the backing image (including if the
	backing file is missing or an incorrect format was specified) is an
	error when ``-u`` is not used.

	Command line options
	--------------------

	``-smp`` (invalid topologies) (removed 5.2)
	'''''''''''''''''''''''''''''''''''''''''''

	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 is removed, the user must ensure
	topologies described with -smp include all possible cpus, i.e.
	sockets * cores * threads = maxcpus.

	``-numa`` node (without memory specified) (removed 5.2)
	'''''''''''''''''''''''''''''''''''''''''''''''''''''''

	Splitting RAM by default between NUMA nodes had the same issues as ``mem``
	parameter 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 explicitly instead.
	Users of existing VMs, wishing to preserve the same RAM distribution, should
	configure it explicitly using ``-numa node,memdev`` options. Current RAM
	distribution can be retrieved using HMP command ``info numa`` and if separate
	memory devices (pc\|nv-dimm) are present use ``info memory-device`` and subtract
	device memory from output of ``info numa``.

	``-numa node,mem=``\ size (removed in 5.1)
	''''''''''''''''''''''''''''''''''''''''''''

	The parameter ``mem`` of ``-numa node`` was used to assign a part of
	guest RAM to a NUMA node. But when using it, it's impossible to manage a specified
	RAM chunk on the host side (like bind it to a host node, setting bind policy, ...),
	so the guest ends up 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 actually manage node RAM on the host side. Use parameter ``memdev``
	with memory-backend-ram backend as 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.
	New machine versions (since 5.1) will not accept the option but it will still
	work with old machine types. User can check the QAPI schema to see if the legacy
	option is supported by looking at MachineInfo::numa-mem-supported property.

	``-mem-path`` fallback to RAM (removed in 5.0)
	''''''''''''''''''''''''''''''''''''''''''''''

	If guest RAM allocation from file pointed by ``mem-path`` failed,
	QEMU was falling back to allocating from RAM, which might have resulted
	in unpredictable behavior since the backing file specified by the user
	as ignored. Currently, users are responsible for making sure the backing storage
	specified with ``-mem-path`` can actually provide the guest RAM configured with
	``-m`` and QEMU fails to start up if RAM allocation is unsuccessful.

	``-smp`` (invalid topologies) (removed 5.2)
	'''''''''''''''''''''''''''''''''''''''''''

	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 is removed, the user must ensure
	topologies described with -smp include all possible cpus, i.e.
	sockets * cores * threads = maxcpus.

	``-machine enforce-config-section=on\|off`` (removed 5.2)
	''''''''''''''''''''''''''''''''''''''''''''''''''''''''

	The ``enforce-config-section`` property was replaced by the
	``-global migration.send-configuration={on\|off}`` option.

	Block devices
	-------------

	VXHS backend (removed in 5.1)
	'''''''''''''''''''''''''''''

	The VXHS code did not compile since v2.12.0. It was removed in 5.1.