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 -usbdevice DEV argument is now a synonym for setting the -device usb-DEV argument instead. The deprecated syntax would automatically enable USB support on the machine type. If using the new syntax, USB support must be explicitly enabled via the -machine usb=on argument.
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.
The acl option to the -vnc argument has been replaced by the tls-authz and sasl-authz options.
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>.
The pretty=on|off switch has no effect for HMP monitors, but is silently ignored. Using the switch with HMP monitors will become an error in the future.
QEMU 4.1 introduced support for the -bios option in QEMU for RISC-V for the RISC-V virt machine and sifive_u machine. QEMU 4.1 had no changes to the default behaviour to avoid breakages.
QEMU 5.1 changes the default behaviour from -bios none to -bios default.
- QEMU 5.1 has three options:
-bios default- This is the current default behavior if no -bios optionis included. This option will load the default OpenSBI firmware automatically. The firmware is included with the QEMU release and no user interaction is required. All a user needs to do is specify the kernel they want to boot with the -kernel option
-bios none- QEMU will not automatically load any firmware. It is upto the user to load all the images they need.
-bios <file>- Tells QEMU to load the specified file as the firmwrae.
Configuring floppies with-global''''''''''''''''''''''''''''''''''''''' Use-device floppy,...instead: :: -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=...-drivewith bogus interface type '''''''''''''''''''''''''''''''''''' Drives with interface types other thanif=noneare for onboard devices. It is possible to use drives the board doesn't pick up with -device. This usage is now deprecated. Useif=noneinstead. Short-form boolean options (since 6.0) '''''''''''''''''''''''''''''''''''''' Boolean options such asshare=on/share=offcould be written in short form asshareandnoshare. This is now deprecated and will cause a warning.delayoption for socket character devices (since 6.0) ''''''''''''''''''''''''''''''''''''''''''''''''''''''''' The replacement for thenodelayshort-form boolean option isnodelay=onrather thandelay=off.--enable-fips(since 6.0) ''''''''''''''''''''''''''''' 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 thelibgcryptlibrary enabled as a cryptography provider. Neither thenettlelibrary, or the built-in cryptography provider are supported on FIPS enabled hosts.-writeconfig(since 6.0) ''''''''''''''''''''''''''''' The-writeconfigoption 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. Userspace local APIC with KVM (x86, since 6.0) '''''''''''''''''''''''''''''''''''''''''''''' Using-M kernel-irqchip=offwith x86 machine types that include a local APIC is deprecated. Thesplitsetting is supported, as is using-M kernel-irqchip=offwith the ISA PC machine type. hexadecimal sizes with scaling multipliers (since 6.0) '''''''''''''''''''''''''''''''''''''''''''''''''''''' 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'. QEMU Machine Protocol (QMP) commands ------------------------------------blockdev-open-tray,blockdev-close-trayargumentdevice(since 2.8.0) ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' Use argumentidinstead.ejectargumentdevice(since 2.8.0) ''''''''''''''''''''''''''''''''''''''''''' Use argumentidinstead.blockdev-change-mediumargumentdevice(since 2.8.0) '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' Use argumentidinstead.block_set_io_throttleargumentdevice(since 2.8.0) ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' Use argumentidinstead.migrate_set_downtimeandmigrate_set_speed(since 2.8.0) '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' Usemigrate-set-parametersinstead.query-named-block-nodesresultencryption_key_missing(since 2.10.0) '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' Always false.query-blockresultinserted.encryption_key_missing(since 2.10.0) ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' Always false.blockdev-addempty string argumentbacking(since 2.10.0) ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' Use argument valuenullinstead.migrate-set-cache-sizeandquery-migrate-cache-size(since 2.11.0) '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' Usemigrate-set-parametersandquery-migrate-parametersinstead.block-commitargumentsbaseandtop(since 3.1.0) ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' Use argumentsbase-nodeandtop-nodeinstead.query-named-block-nodesandquery-blockresult dirty-bitmaps[i].status (since 4.0) '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' Thestatusfield of theBlockDirtyInfostructure, returned by these commands is deprecated. Two new boolean fields,recordingandbusyeffectively replace it.query-blockresult fielddirty-bitmaps(Since 4.2) '''''''''''''''''''''''''''''''''''''''''''''''''''''''''' Thedirty-bitmapsfield of theBlockInfostructure, returned by the query-block command is itself now deprecated. Thedirty-bitmapsfield of theBlockDeviceInfostruct should be used instead, which is the type of theinsertedfield in query-block replies, as well as the type of array items in query-named-block-nodes. Since thedirty-bitmapsfield is optionally present in both the old and new locations, clients must use introspection to learn where to anticipate the field if/when it does appear in command output.query-cpus(since 2.12.0) ''''''''''''''''''''''''''''' Thequery-cpuscommand is replaced by thequery-cpus-fastcommand.query-cpus-fastarchoutput member (since 3.0.0) '''''''''''''''''''''''''''''''''''''''''''''''''''''''' Thearchoutput member of thequery-cpus-fastcommand is replaced by thetargetoutput member.query-events(since 4.0) '''''''''''''''''''''''''''' Thequery-eventscommand has been superseded by the more powerful and accuratequery-qmp-schemacommand. chardev client socket withwaitoption (since 4.0) '''''''''''''''''''''''''''''''''''''''''''''''''''''' Character devices creating sockets in client mode should not specify the 'wait' field, which is only applicable to sockets in server modenbd-server-addandnbd-server-remove(since 5.2) '''''''''''''''''''''''''''''''''''''''''''''''''''''''' Use the more generic commandsblock-export-addandblock-export-delinstead. As part of this deprecation, wherenbd-server-addused a singlebitmap, the newblock-export-adduses a list ofbitmaps. Human Monitor Protocol (HMP) commands -------------------------------------acl_show,acl_reset,acl_policy,acl_add,acl_remove(since 4.0.0) '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' Theacl_show,acl_reset,acl_policy,acl_add, andacl_removecommands are deprecated with no replacement. Authorization for VNC should be performed using the pluggable QAuthZ objects. System emulator CPUS --------------------moxieCPU (since 5.2.0) ''''''''''''''''''''''''''' Themoxieguest CPU support is deprecated and will be removed in a future version of QEMU. It's unclear whether anybody is still using CPU emulation in QEMU, and there are no test images available to make sure that the code is still working.lm32CPUs (since 5.2.0) ''''''''''''''''''''''''''' Thelm32guest CPU support is deprecated and will be removed in a future version of QEMU. The only public user of this architecture was the milkymist project, which has been dead for years; there was never an upstream Linux port.unicore32CPUs (since 5.2.0) '''''''''''''''''''''''''''''''' Theunicore32guest CPU support is deprecated and will be removed in a future version of QEMU. Support for this CPU was removed from the upstream Linux kernel, and there is no available upstream toolchain to build binaries for it.Icelake-ClientCPU Model (since 5.2.0) ''''''''''''''''''''''''''''''''''''''''''Icelake-ClientCPU Models are deprecated. UseIcelake-ServerCPU Models instead. MIPSI7200CPU Model (since 5.2) '''''''''''''''''''''''''''''''''''' TheI7200guest 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. System emulator devices -----------------------ide-drive(since 4.2) ''''''''''''''''''''''''' The 'ide-drive' device is deprecated. Users should use 'ide-hd' or 'ide-cd' as appropriate to get an IDE hard disk or CD-ROM as needed.scsi-disk(since 4.2) ''''''''''''''''''''''''' The 'scsi-disk' device is deprecated. Users should use 'scsi-hd' or 'scsi-cd' as appropriate to get a SCSI hard disk or CD-ROM as needed. System emulator machines ------------------------ Raspberry Piraspi2andraspi3machines (since 5.2) ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' The Raspberry Pi machines come in various models (A, A+, B, B+). To be able to distinguish which model QEMU is implementing, theraspi2andraspi3machines have been renamedraspi2bandraspi3b. Device options -------------- Emulated device options '''''''''''''''''''''''-device virtio-blk,scsi=onoff, which is an alias. Block device options ''''''''''''''''''''"backing": ""(since 2.12.0) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ In order to prevent QEMU from automatically opening an image's backing chain, use"backing": nullinstead.rbdkeyvalue pair encoded filenames:""(since 3.1.0) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Options forrbdshould 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"}sheepdogdriver (since 5.2.0) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Thesheepdogblock device driver is deprecated. The corresponding upstream server project is no longer actively maintained. Users are recommended to switch to an alternative distributed block device driver such as RBD. Theqemu-img convertcommand can be used to liberate existing data by moving it out of sheepdog volumes into an alternative storage backend. linux-user mode CPUs --------------------ppc64abi32CPUs (since 5.2.0) ''''''''''''''''''''''''''''''''' Theppc64abi32architecture 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. MIPSI7200CPU (since 5.2) '''''''''''''''''''''''''''''' TheI7200guest 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. Related binaries ---------------- qemu-img amend to adjust backing file (since 5.1) ''''''''''''''''''''''''''''''''''''''''''''''''' The use ofqemu-img amendto modify the name or format of a qcow2 backing image is deprecated; this functionality 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). Rather, any changes to the backing chain should be performed withqemu-img rebase -ueither before or after the remaining changes being performed by amend, as appropriate. qemu-img backing file without format (since 5.1) '''''''''''''''''''''''''''''''''''''''''''''''' The use ofqemu-img create,qemu-img rebase, orqemu-img convertto create or modify an image that depends on a backing file now recommends 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 the warning message, or even future refusal to create an unsafe image, you must pass-o backing_fmt=(or the shorthand-Fduring create) to specify the intended backing format. You may useqemu-img rebase -uto retroactively add a backing format to an existing image. However, be aware that there are already potential security risks to blindly usingqemu-img infoto probe the format of an untrusted backing image, when deciding what format to add into an existing image. Backwards compatibility ----------------------- Runnability guarantee of CPU models (since 4.1.0) ''''''''''''''''''''''''''''''''''''''''''''''''' 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 thealias-offield returned by thequery-cpu-definitionsQMP command. While those guarantees are kept, the return value ofquery-cpu-definitionswill 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. Guest Emulator ISAs ------------------- nanoMIPS ISA '''''''''''' ThenanoMIPS`` ISA has never been upstreamed to any compiler toolchain. As it is hard to generate binaries for it, declare it deprecated.