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 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
.
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.
The Raspberry Pi machines come in various models (A, A+, B, B+). To be able to distinguish which model QEMU is implementing, the raspi2
and raspi3
machines have been renamed raspi2b
and raspi3b
.
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.
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.