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The -realtime mlock=on|off argument has been replaced by the -overcommit mem-lock=on|off argument.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

change (removed in 6.0)

Use blockdev-change-medium or change-vnc-password 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The [hub_id name] parameter tuple of the ‘hostfwd_add’ and ‘hostfwd_remove’ HMP commands has been replaced by netdev_id.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.

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.

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.

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.