1.. _Deprecated features: 2 3Deprecated features 4=================== 5 6In general features are intended to be supported indefinitely once 7introduced into QEMU. In the event that a feature needs to be removed, 8it will be listed in this section. The feature will remain functional for the 9release in which it was deprecated and one further release. After these two 10releases, the feature is liable to be removed. Deprecated features may also 11generate warnings on the console when QEMU starts up, or if activated via a 12monitor command, however, this is not a mandatory requirement. 13 14Prior to the 2.10.0 release there was no official policy on how 15long features would be deprecated prior to their removal, nor 16any documented list of which features were deprecated. Thus 17any features deprecated prior to 2.10.0 will be treated as if 18they were first deprecated in the 2.10.0 release. 19 20What follows is a list of all features currently marked as 21deprecated. 22 23System emulator command line arguments 24-------------------------------------- 25 26``QEMU_AUDIO_`` environment variables and ``-audio-help`` (since 4.0) 27''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 28 29The ``-audiodev`` argument is now the preferred way to specify audio 30backend settings instead of environment variables. To ease migration to 31the new format, the ``-audiodev-help`` option can be used to convert 32the current values of the environment variables to ``-audiodev`` options. 33 34Creating sound card devices and vnc without ``audiodev=`` property (since 4.2) 35'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 36 37When not using the deprecated legacy audio config, each sound card 38should specify an ``audiodev=`` property. Additionally, when using 39vnc, you should specify an ``audiodev=`` property if you plan to 40transmit audio through the VNC protocol. 41 42Short-form boolean options (since 6.0) 43'''''''''''''''''''''''''''''''''''''' 44 45Boolean options such as ``share=on``/``share=off`` could be written 46in short form as ``share`` and ``noshare``. This is now deprecated 47and will cause a warning. 48 49``delay`` option for socket character devices (since 6.0) 50''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 51 52The replacement for the ``nodelay`` short-form boolean option is ``nodelay=on`` 53rather than ``delay=off``. 54 55``-spice password=string`` (since 6.0) 56'''''''''''''''''''''''''''''''''''''' 57 58This option is insecure because the SPICE password remains visible in 59the process listing. This is replaced by the new ``password-secret`` 60option which lets the password be securely provided on the command 61line using a ``secret`` object instance. 62 63``-smp`` ("parameter=0" SMP configurations) (since 6.2) 64''''''''''''''''''''''''''''''''''''''''''''''''''''''' 65 66Specified CPU topology parameters must be greater than zero. 67 68In the SMP configuration, users should either provide a CPU topology 69parameter with a reasonable value (greater than zero) or just omit it 70and QEMU will compute the missing value. 71 72However, historically it was implicitly allowed for users to provide 73a parameter with zero value, which is meaningless and could also possibly 74cause unexpected results in the -smp parsing. So support for this kind of 75configurations (e.g. -smp 8,sockets=0) is deprecated since 6.2 and will 76be removed in the near future, users have to ensure that all the topology 77members described with -smp are greater than zero. 78 79Plugin argument passing through ``arg=<string>`` (since 6.1) 80'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 81 82Passing TCG plugins arguments through ``arg=`` is redundant is makes the 83command-line less readable, especially when the argument itself consist of a 84name and a value, e.g. ``-plugin plugin_name,arg="arg_name=arg_value"``. 85Therefore, the usage of ``arg`` is redundant. Single-word arguments are treated 86as short-form boolean values, and passed to plugins as ``arg_name=on``. 87However, short-form booleans are deprecated and full explicit ``arg_name=on`` 88form is preferred. 89 90``-no-hpet`` (since 8.0) 91'''''''''''''''''''''''' 92 93The HPET setting has been turned into a machine property. 94Use ``-machine hpet=off`` instead. 95 96``-accel hax`` (since 8.0) 97'''''''''''''''''''''''''' 98 99The HAXM project has been retired (see https://github.com/intel/haxm#status). 100Use "whpx" (on Windows) or "hvf" (on macOS) instead. 101 102 103QEMU Machine Protocol (QMP) commands 104------------------------------------ 105 106``blockdev-open-tray``, ``blockdev-close-tray`` argument ``device`` (since 2.8) 107''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 108 109Use argument ``id`` instead. 110 111``eject`` argument ``device`` (since 2.8) 112''''''''''''''''''''''''''''''''''''''''' 113 114Use argument ``id`` instead. 115 116``blockdev-change-medium`` argument ``device`` (since 2.8) 117'''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 118 119Use argument ``id`` instead. 120 121``block_set_io_throttle`` argument ``device`` (since 2.8) 122''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 123 124Use argument ``id`` instead. 125 126``blockdev-add`` empty string argument ``backing`` (since 2.10) 127''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 128 129Use argument value ``null`` instead. 130 131``block-commit`` arguments ``base`` and ``top`` (since 3.1) 132''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 133 134Use arguments ``base-node`` and ``top-node`` instead. 135 136``nbd-server-add`` and ``nbd-server-remove`` (since 5.2) 137'''''''''''''''''''''''''''''''''''''''''''''''''''''''' 138 139Use the more generic commands ``block-export-add`` and ``block-export-del`` 140instead. As part of this deprecation, where ``nbd-server-add`` used a 141single ``bitmap``, the new ``block-export-add`` uses a list of ``bitmaps``. 142 143``query-qmp-schema`` return value member ``values`` (since 6.2) 144''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 145 146Member ``values`` in return value elements with meta-type ``enum`` is 147deprecated. Use ``members`` instead. 148 149``drive-backup`` (since 6.2) 150'''''''''''''''''''''''''''' 151 152Use ``blockdev-backup`` in combination with ``blockdev-add`` instead. 153This change primarily separates the creation/opening process of the backup 154target with explicit, separate steps. ``blockdev-backup`` uses mostly the 155same arguments as ``drive-backup``, except the ``format`` and ``mode`` 156options are removed in favor of using explicit ``blockdev-create`` and 157``blockdev-add`` calls. See :doc:`/interop/live-block-operations` for 158details. 159 160Incorrectly typed ``device_add`` arguments (since 6.2) 161'''''''''''''''''''''''''''''''''''''''''''''''''''''' 162 163Due to shortcomings in the internal implementation of ``device_add``, QEMU 164incorrectly accepts certain invalid arguments: Any object or list arguments are 165silently ignored. Other argument types are not checked, but an implicit 166conversion happens, so that e.g. string values can be assigned to integer 167device properties or vice versa. 168 169This is a bug in QEMU that will be fixed in the future so that previously 170accepted incorrect commands will return an error. Users should make sure that 171all arguments passed to ``device_add`` are consistent with the documented 172property types. 173 174Host Architectures 175------------------ 176 177BE MIPS (since 7.2) 178''''''''''''''''''' 179 180As Debian 10 ("Buster") moved into LTS the big endian 32 bit version of 181MIPS moved out of support making it hard to maintain our 182cross-compilation CI tests of the architecture. As we no longer have 183CI coverage support may bitrot away before the deprecation process 184completes. The little endian variants of MIPS (both 32 and 64 bit) are 185still a supported host architecture. 186 187QEMU API (QAPI) events 188---------------------- 189 190``MEM_UNPLUG_ERROR`` (since 6.2) 191'''''''''''''''''''''''''''''''''''''''''''''''''''''''' 192 193Use the more generic event ``DEVICE_UNPLUG_GUEST_ERROR`` instead. 194 195 196System emulator machines 197------------------------ 198 199Arm ``virt`` machine ``dtb-kaslr-seed`` property 200'''''''''''''''''''''''''''''''''''''''''''''''' 201 202The ``dtb-kaslr-seed`` property on the ``virt`` board has been 203deprecated; use the new name ``dtb-randomness`` instead. The new name 204better reflects the way this property affects all random data within 205the device tree blob, not just the ``kaslr-seed`` node. 206 207``pc-i440fx-1.4`` up to ``pc-i440fx-1.7`` (since 7.0) 208''''''''''''''''''''''''''''''''''''''''''''''''''''' 209 210These old machine types are quite neglected nowadays and thus might have 211various pitfalls with regards to live migration. Use a newer machine type 212instead. 213 214 215Backend options 216--------------- 217 218Using non-persistent backing file with pmem=on (since 6.1) 219'''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 220 221This option is used when ``memory-backend-file`` is consumed by emulated NVDIMM 222device. However enabling ``memory-backend-file.pmem`` option, when backing file 223is (a) not DAX capable or (b) not on a filesystem that support direct mapping 224of persistent memory, is not safe and may lead to data loss or corruption in case 225of host crash. 226Options are: 227 228 - modify VM configuration to set ``pmem=off`` to continue using fake NVDIMM 229 (without persistence guaranties) with backing file on non DAX storage 230 - move backing file to NVDIMM storage and keep ``pmem=on`` 231 (to have NVDIMM with persistence guaranties). 232 233Device options 234-------------- 235 236Emulated device options 237''''''''''''''''''''''' 238 239``-device virtio-blk,scsi=on|off`` (since 5.0) 240^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 241 242The virtio-blk SCSI passthrough feature is a legacy VIRTIO feature. VIRTIO 1.0 243and later do not support it because the virtio-scsi device was introduced for 244full SCSI support. Use virtio-scsi instead when SCSI passthrough is required. 245 246Note this also applies to ``-device virtio-blk-pci,scsi=on|off``, which is an 247alias. 248 249``-device sga`` (since 6.2) 250^^^^^^^^^^^^^^^^^^^^^^^^^^^ 251 252The ``sga`` device loads an option ROM for x86 targets which enables 253SeaBIOS to send messages to the serial console. SeaBIOS 1.11.0 onwards 254contains native support for this feature and thus use of the option 255ROM approach is obsolete. The native SeaBIOS support can be activated 256by using ``-machine graphics=off``. 257 258``-device nvme-ns,eui64-default=on|off`` (since 7.1) 259^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 260 261In QEMU versions 6.1, 6.2 and 7.0, the ``nvme-ns`` generates an EUI-64 262identifier that is not globally unique. If an EUI-64 identifier is required, the 263user must set it explicitly using the ``nvme-ns`` device parameter ``eui64``. 264 265``-device nvme,use-intel-id=on|off`` (since 7.1) 266^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 267 268The ``nvme`` device originally used a PCI Vendor/Device Identifier combination 269from Intel that was not properly allocated. Since version 5.2, the controller 270has used a properly allocated identifier. Deprecate the ``use-intel-id`` 271machine compatibility parameter. 272 273 274Block device options 275'''''''''''''''''''' 276 277``"backing": ""`` (since 2.12) 278^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 279 280In order to prevent QEMU from automatically opening an image's backing 281chain, use ``"backing": null`` instead. 282 283``rbd`` keyvalue pair encoded filenames: ``""`` (since 3.1) 284^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 285 286Options for ``rbd`` should be specified according to its runtime options, 287like other block drivers. Legacy parsing of keyvalue pair encoded 288filenames is useful to open images with the old format for backing files; 289These image files should be updated to use the current format. 290 291Example of legacy encoding:: 292 293 json:{"file.driver":"rbd", "file.filename":"rbd:rbd/name"} 294 295The above, converted to the current supported format:: 296 297 json:{"file.driver":"rbd", "file.pool":"rbd", "file.image":"name"} 298 299Backwards compatibility 300----------------------- 301 302Runnability guarantee of CPU models (since 4.1) 303''''''''''''''''''''''''''''''''''''''''''''''' 304 305Previous versions of QEMU never changed existing CPU models in 306ways that introduced additional host software or hardware 307requirements to the VM. This allowed management software to 308safely change the machine type of an existing VM without 309introducing new requirements ("runnability guarantee"). This 310prevented CPU models from being updated to include CPU 311vulnerability mitigations, leaving guests vulnerable in the 312default configuration. 313 314The CPU model runnability guarantee won't apply anymore to 315existing CPU models. Management software that needs runnability 316guarantees must resolve the CPU model aliases using the 317``alias-of`` field returned by the ``query-cpu-definitions`` QMP 318command. 319 320While those guarantees are kept, the return value of 321``query-cpu-definitions`` will have existing CPU model aliases 322point to a version that doesn't break runnability guarantees 323(specifically, version 1 of those CPU models). In future QEMU 324versions, aliases will point to newer CPU model versions 325depending on the machine type, so management software must 326resolve CPU model aliases before starting a virtual machine. 327 328Tools 329----- 330 331virtiofsd 332''''''''' 333 334There is a new Rust implementation of ``virtiofsd`` at 335``https://gitlab.com/virtio-fs/virtiofsd``; 336since this is now marked stable, new development should be done on that 337rather than the existing C version in the QEMU tree. 338The C version will still accept fixes and patches that 339are already in development for the moment, but will eventually 340be deleted from this tree. 341New deployments should use the Rust version, and existing systems 342should consider moving to it. The command line and feature set 343is very close and moving should be simple. 344 345 346QEMU guest agent 347---------------- 348 349``--blacklist`` command line option (since 7.2) 350''''''''''''''''''''''''''''''''''''''''''''''' 351 352``--blacklist`` has been replaced by ``--block-rpcs`` (which is a better 353wording for what this option does). The short form ``-b`` still stays 354the same and thus is the preferred way for scripts that should run with 355both, older and future versions of QEMU. 356 357``blacklist`` config file option (since 7.2) 358'''''''''''''''''''''''''''''''''''''''''''' 359 360The ``blacklist`` config file option has been renamed to ``block-rpcs`` 361(to be in sync with the renaming of the corresponding command line 362option). 363