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.
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.
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.
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>
.
tty
and parport
are aliases that will be removed. Instead, the actual backend names serial
and parallel
should be used.
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.
The replacement for the nodelay
short-form boolean option is nodelay=on
rather than delay=off
.
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.
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.
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.
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'.
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.
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.
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.
Use -display sdl,window-close=...
instead (i.e. with a minus instead of an underscore between "window" and "close").
The -no-quit
is a synonym for -display ...,window-close=off
which should be used instead.
Use -display sdl,grab-mod=lshift-lctrl-lalt
instead.
Use -display sdl,grab-mod=rctrl
instead.
Use -display sdl
instead.
Use -display curses
instead.
Use -device
instead.
Specified CPU topology parameters must be greater than zero.
In the SMP configuration, users should either provide a CPU topology parameter with a reasonable value (greater than zero) or just omit it and QEMU will compute the missing value.
However, historically it was implicitly allowed for users to provide a parameter with zero value, which is meaningless and could also possibly cause unexpected results in the -smp parsing. So support for this kind of configurations (e.g. -smp 8,sockets=0) is deprecated since 6.2 and will be removed in the near future, users have to ensure that all the topology members described with -smp are greater than zero.
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.
Use argument id
instead.
Use argument id
instead.
Use argument id
instead.
Use argument id
instead.
Use argument value null
instead.
Use arguments base-node
and top-node
instead.
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
.
Member values
in return value elements with meta-type enum
is deprecated. Use members
instead.
Use blockdev-backup
in combination with blockdev-add
instead. This change primarily separates the creation/opening process of the backup target with explicit, separate steps. blockdev-backup
uses mostly the same arguments as drive-backup
, except the format
and mode
options are removed in favor of using explicit blockdev-create
and blockdev-add
calls. See /interop/live-block-operations
for details.
Due to shortcomings in the internal implementation of device_add
, QEMU incorrectly accepts certain invalid arguments: Any object or list arguments are silently ignored. Other argument types are not checked, but an implicit conversion happens, so that e.g. string values can be assigned to integer device properties or vice versa.
This is a bug in QEMU that will be fixed in the future so that previously accepted incorrect commands will return an error. Users should make sure that all arguments passed to device_add
are consistent with the documented property types.
The MIPS Trap-and-Emul
KVM host and guest support has been removed from Linux upstream kernel, declare it deprecated.
Icelake-Client
CPU Models are deprecated. Use Icelake-Server
CPU Models instead.
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.
Use the more generic event DEVICE_UNPLUG_GUEST_ERROR
instead.
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.
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).
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.
The sga
device loads an option ROM for x86 targets which enables SeaBIOS to send messages to the serial console. SeaBIOS 1.11.0 onwards contains native support for this feature and thus use of the option ROM approach is obsolete. The native SeaBIOS support can be activated by using -machine graphics=off
.
In order to prevent QEMU from automatically opening an image's backing chain, use "backing": null
instead.
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"}
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.
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.
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.
The nanoMIPS
ISA has never been upstreamed to any compiler toolchain. As it is hard to generate binaries for it, declare it deprecated.