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The -realtime mlock=on|off argument has been replaced by the -overcommit mem-lock=on|off argument.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 (removed in 6.0)

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=.

-usbdevice audio (removed in 6.0)

This option lacked the possibility to specify an audio backend device. Use -device usb-audio now instead (and specify a corresponding USB host controller or -usb if necessary).

-vnc acl (removed in 6.0)

The acl option to the -vnc argument has been replaced by the tls-authz and sasl-authz options.

-mon ...,control=readline,pretty=on|off (removed in 6.0)

The pretty=on|off switch has no effect for HMP monitors and its use is rejected.

-drive file=json:{...{'driver':'file'}} (removed 6.0)

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.

Floppy controllers’ drive properties (removed in 6.0)

Use -device floppy,... instead. When configuring onboard floppy controllers

-global isa-fdc.driveA=...
-global sysbus-fdc.driveA=...
-global SUNW,fdtwo.drive=...

become

-device floppy,unit=0,drive=...

and

-global isa-fdc.driveB=...
-global sysbus-fdc.driveB=...

become

-device floppy,unit=1,drive=...

When plugging in a floppy controller

-device isa-fdc,...,driveA=...

becomes

-device isa-fdc,...
-device floppy,unit=0,drive=...

and

-device isa-fdc,...,driveB=...

becomes

-device isa-fdc,...
-device floppy,unit=1,drive=...

-drive with bogus interface type (removed in 6.0)

Drives with interface types other than if=none are for onboard devices. Drives the board doesn’t pick up can no longer be used with -device. Use if=none instead.

-usbdevice ccid (removed in 6.0)

This option was undocumented and not used in the field. Use -device usb-ccid` instead.

RISC-V firmware not booted by default (removed in 5.1)

QEMU 5.1 changes the default behaviour from -bios none to -bios default for the RISC-V virt machine and sifive_u machine.

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.

change (removed in 6.0)

Use blockdev-change-medium or change-vnc-password instead.

query-events (removed in 6.0)

The query-events command has been superseded by the more powerful and accurate query-qmp-schema command.

migrate_set_cache_size and query-migrate-cache-size (removed in 6.0)

Use migrate_set_parameter and info migrate_parameters instead.

migrate_set_downtime and migrate_set_speed (removed in 6.0)

Use migrate_set_parameter instead.

query-cpus (removed in 6.0)

The query-cpus command is replaced by the query-cpus-fast command.

query-cpus-fast arch output member (removed in 6.0)

The arch output member of the query-cpus-fast command is replaced by the target output member.

chardev client socket with wait option (removed in 6.0)

Character devices creating sockets in client mode should not specify the ‘wait’ field, which is only applicable to sockets in server mode

query-named-block-nodes result encryption_key_missing (removed in 6.0)

Removed with no replacement.

query-block result inserted.encryption_key_missing (removed in 6.0)

Removed with no replacement.

query-named-block-nodes and query-block result dirty-bitmaps[i].status (removed in 6.0)

The status field of the BlockDirtyInfo structure, returned by these commands is removed. Two new boolean fields, recording and busy effectively replace it.

query-block result field dirty-bitmaps (removed in 6.0)

The dirty-bitmaps field of the BlockInfo structure, returned by the query-block command is itself now removed. 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.

object-add option props (removed in 6.0)

Specify the properties for the object as top-level arguments instead.

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.

change vnc TARGET (removed in 6.0)

No replacement. The change vnc password and change DEVICE MEDIUM commands are not affected.

acl_show, acl_reset, acl_policy, acl_add, acl_remove (removed in 6.0)

The acl_show, acl_reset, acl_policy, acl_add, and acl_remove commands were removed with no replacement. Authorization for VNC should be performed using the pluggable QAuthZ objects.

migrate-set-cache-size and info migrate-cache-size (removed in 6.0)

Use migrate-set-parameters and info migrate-parameters instead.

migrate_set_downtime and migrate_set_speed (removed in 6.0)

Use migrate-set-parameters instead.

info cpustats (removed in 6.1)

This command didn’t produce any output already. Removed with no replacement.

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.

compat property of server class POWER CPUs (removed in 6.0)

The max-cpu-compat property of the pseries machine type should be used instead.

moxie CPU (removed in 6.1)

Nobody was using this CPU emulation in QEMU, and there were no test images available to make sure that the code is still working, so it has been removed without replacement.

lm32 CPUs (removed in 6.1.0)

The only public user of this architecture was the milkymist project, which has been dead for years; there was never an upstream Linux port. Removed without replacement.

unicore32 CPUs (since 6.1.0)

Support for this CPU was removed from the upstream Linux kernel, and there is no available upstream toolchain to build binaries for it. Removed without replacement.

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.

mips fulong2e machine alias (removed in 6.0)

This machine has been renamed fuloong2e.

pc-1.0, pc-1.1, pc-1.2 and pc-1.3 (removed in 6.0)

These machine types were very old and likely could not be used for live migration from old QEMU versions anymore. Use a newer machine type instead.

linux-user mode CPUs

tilegx CPUs (removed in 6.0)

The tilegx guest CPU support has been removed without replacement. It was only implemented in linux-user mode, but support for this CPU was removed from the upstream Linux kernel in 2018, and it has also been dropped from glibc, so there is no new Linux development taking place with this architecture. For running the old binaries, you can use older versions of QEMU.

System emulator devices

ide-drive (removed in 6.0)

The ‘ide-drive’ device has been removed. Users should use ‘ide-hd’ or ‘ide-cd’ as appropriate to get an IDE hard disk or CD-ROM as needed.

scsi-disk (removed in 6.0)

The ‘scsi-disk’ device has been removed. Users should use ‘scsi-hd’ or ‘scsi-cd’ as appropriate to get a SCSI hard disk or CD-ROM as needed.

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.

qemu-img amend to adjust backing file (removed in 6.1)

The use of qemu-img amend to modify the name or format of a qcow2 backing image was never fully documented or tested, and interferes with other amend operations that need access to the original backing image (such as deciding whether a v3 zero cluster may be left unallocated when converting to a v2 image). Any changes to the backing chain should be performed with qemu-img rebase -u either before or after the remaining changes being performed by amend, as appropriate.

qemu-img backing file without format (removed in 6.1)

The use of qemu-img create, qemu-img rebase, or qemu-img convert to create or modify an image that depends on a backing file now requires that an explicit backing format be provided. This is for safety: if QEMU probes a different format than what you thought, the data presented to the guest will be corrupt; similarly, presenting a raw image to a guest allows a potential security exploit if a future probe sees a non-raw image based on guest writes.

To avoid creating unsafe backing chains, you must pass -o backing_fmt= (or the shorthand -F during create) to specify the intended backing format. You may use qemu-img rebase -u to retroactively add a backing format to an existing image. However, be aware that there are already potential security risks to blindly using qemu-img info to probe the format of an untrusted backing image, when deciding what format to add into an existing image.

Block devices

VXHS backend (removed in 5.1)

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

sheepdog driver (removed in 6.0)

The corresponding upstream server project is no longer maintained. Users are recommended to switch to an alternative distributed block device driver such as RBD.