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 42Creating sound card devices using ``-soundhw`` (since 5.1) 43'''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 44 45Sound card devices should be created using ``-device`` instead. The 46names are the same for most devices. The exceptions are ``hda`` which 47needs two devices (``-device intel-hda -device hda-duplex``) and 48``pcspk`` which can be activated using ``-machine 49pcspk-audiodev=<name>``. 50 51``-chardev`` backend aliases ``tty`` and ``parport`` (since 6.0) 52'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 53 54``tty`` and ``parport`` are aliases that will be removed. Instead, the 55actual backend names ``serial`` and ``parallel`` should be used. 56 57Short-form boolean options (since 6.0) 58'''''''''''''''''''''''''''''''''''''' 59 60Boolean options such as ``share=on``/``share=off`` could be written 61in short form as ``share`` and ``noshare``. This is now deprecated 62and will cause a warning. 63 64``delay`` option for socket character devices (since 6.0) 65''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 66 67The replacement for the ``nodelay`` short-form boolean option is ``nodelay=on`` 68rather than ``delay=off``. 69 70``--enable-fips`` (since 6.0) 71''''''''''''''''''''''''''''' 72 73This option restricts usage of certain cryptographic algorithms when 74the host is operating in FIPS mode. 75 76If FIPS compliance is required, QEMU should be built with the ``libgcrypt`` 77library enabled as a cryptography provider. 78 79Neither the ``nettle`` library, or the built-in cryptography provider are 80supported on FIPS enabled hosts. 81 82``-writeconfig`` (since 6.0) 83''''''''''''''''''''''''''''' 84 85The ``-writeconfig`` option is not able to serialize the entire contents 86of the QEMU command line. It is thus considered a failed experiment 87and deprecated, with no current replacement. 88 89Userspace local APIC with KVM (x86, since 6.0) 90'''''''''''''''''''''''''''''''''''''''''''''' 91 92Using ``-M kernel-irqchip=off`` with x86 machine types that include a local 93APIC is deprecated. The ``split`` setting is supported, as is using 94``-M kernel-irqchip=off`` with the ISA PC machine type. 95 96hexadecimal sizes with scaling multipliers (since 6.0) 97'''''''''''''''''''''''''''''''''''''''''''''''''''''' 98 99Input parameters that take a size value should only use a size suffix 100(such as 'k' or 'M') when the base is written in decimal, and not when 101the value is hexadecimal. That is, '0x20M' is deprecated, and should 102be written either as '32M' or as '0x2000000'. 103 104``-spice password=string`` (since 6.0) 105'''''''''''''''''''''''''''''''''''''' 106 107This option is insecure because the SPICE password remains visible in 108the process listing. This is replaced by the new ``password-secret`` 109option which lets the password be securely provided on the command 110line using a ``secret`` object instance. 111 112``opened`` property of ``rng-*`` objects (since 6.0) 113'''''''''''''''''''''''''''''''''''''''''''''''''''' 114 115The only effect of specifying ``opened=on`` in the command line or QMP 116``object-add`` is that the device is opened immediately, possibly before all 117other options have been processed. This will either have no effect (if 118``opened`` was the last option) or cause errors. The property is therefore 119useless and should not be specified. 120 121``loaded`` property of ``secret`` and ``secret_keyring`` objects (since 6.0) 122'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 123 124The only effect of specifying ``loaded=on`` in the command line or QMP 125``object-add`` is that the secret is loaded immediately, possibly before all 126other options have been processed. This will either have no effect (if 127``loaded`` was the last option) or cause options to be effectively ignored as 128if they were not given. The property is therefore useless and should not be 129specified. 130 131``-display sdl,window_close=...`` (since 6.1) 132''''''''''''''''''''''''''''''''''''''''''''' 133 134Use ``-display sdl,window-close=...`` instead (i.e. with a minus instead of 135an underscore between "window" and "close"). 136 137``-no-quit`` (since 6.1) 138'''''''''''''''''''''''' 139 140The ``-no-quit`` is a synonym for ``-display ...,window-close=off`` which 141should be used instead. 142 143``-alt-grab`` and ``-display sdl,alt_grab=on`` (since 6.2) 144'''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 145 146Use ``-display sdl,grab-mod=lshift-lctrl-lalt`` instead. 147 148``-ctrl-grab`` and ``-display sdl,ctrl_grab=on`` (since 6.2) 149'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 150 151Use ``-display sdl,grab-mod=rctrl`` instead. 152 153``-sdl`` (since 6.2) 154'''''''''''''''''''' 155 156Use ``-display sdl`` instead. 157 158``-curses`` (since 6.2) 159''''''''''''''''''''''' 160 161Use ``-display curses`` instead. 162 163``-watchdog`` (since 6.2) 164''''''''''''''''''''''''' 165 166Use ``-device`` instead. 167 168``-smp`` ("parameter=0" SMP configurations) (since 6.2) 169''''''''''''''''''''''''''''''''''''''''''''''''''''''' 170 171Specified CPU topology parameters must be greater than zero. 172 173In the SMP configuration, users should either provide a CPU topology 174parameter with a reasonable value (greater than zero) or just omit it 175and QEMU will compute the missing value. 176 177However, historically it was implicitly allowed for users to provide 178a parameter with zero value, which is meaningless and could also possibly 179cause unexpected results in the -smp parsing. So support for this kind of 180configurations (e.g. -smp 8,sockets=0) is deprecated since 6.2 and will 181be removed in the near future, users have to ensure that all the topology 182members described with -smp are greater than zero. 183 184Plugin argument passing through ``arg=<string>`` (since 6.1) 185'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 186 187Passing TCG plugins arguments through ``arg=`` is redundant is makes the 188command-line less readable, especially when the argument itself consist of a 189name and a value, e.g. ``-plugin plugin_name,arg="arg_name=arg_value"``. 190Therefore, the usage of ``arg`` is redundant. Single-word arguments are treated 191as short-form boolean values, and passed to plugins as ``arg_name=on``. 192However, short-form booleans are deprecated and full explicit ``arg_name=on`` 193form is preferred. 194 195 196QEMU Machine Protocol (QMP) commands 197------------------------------------ 198 199``blockdev-open-tray``, ``blockdev-close-tray`` argument ``device`` (since 2.8) 200''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 201 202Use argument ``id`` instead. 203 204``eject`` argument ``device`` (since 2.8) 205''''''''''''''''''''''''''''''''''''''''' 206 207Use argument ``id`` instead. 208 209``blockdev-change-medium`` argument ``device`` (since 2.8) 210'''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 211 212Use argument ``id`` instead. 213 214``block_set_io_throttle`` argument ``device`` (since 2.8) 215''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 216 217Use argument ``id`` instead. 218 219``blockdev-add`` empty string argument ``backing`` (since 2.10) 220''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 221 222Use argument value ``null`` instead. 223 224``block-commit`` arguments ``base`` and ``top`` (since 3.1) 225''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 226 227Use arguments ``base-node`` and ``top-node`` instead. 228 229``nbd-server-add`` and ``nbd-server-remove`` (since 5.2) 230'''''''''''''''''''''''''''''''''''''''''''''''''''''''' 231 232Use the more generic commands ``block-export-add`` and ``block-export-del`` 233instead. As part of this deprecation, where ``nbd-server-add`` used a 234single ``bitmap``, the new ``block-export-add`` uses a list of ``bitmaps``. 235 236``query-qmp-schema`` return value member ``values`` (since 6.2) 237''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 238 239Member ``values`` in return value elements with meta-type ``enum`` is 240deprecated. Use ``members`` instead. 241 242System accelerators 243------------------- 244 245MIPS ``Trap-and-Emul`` KVM support (since 6.0) 246'''''''''''''''''''''''''''''''''''''''''''''' 247 248The MIPS ``Trap-and-Emul`` KVM host and guest support has been removed 249from Linux upstream kernel, declare it deprecated. 250 251System emulator CPUS 252-------------------- 253 254``Icelake-Client`` CPU Model (since 5.2) 255'''''''''''''''''''''''''''''''''''''''' 256 257``Icelake-Client`` CPU Models are deprecated. Use ``Icelake-Server`` CPU 258Models instead. 259 260MIPS ``I7200`` CPU Model (since 5.2) 261'''''''''''''''''''''''''''''''''''' 262 263The ``I7200`` guest CPU relies on the nanoMIPS ISA, which is deprecated 264(the ISA has never been upstreamed to a compiler toolchain). Therefore 265this CPU is also deprecated. 266 267 268QEMU API (QAPI) events 269---------------------- 270 271``MEM_UNPLUG_ERROR`` (since 6.2) 272'''''''''''''''''''''''''''''''''''''''''''''''''''''''' 273 274Use the more generic event ``DEVICE_UNPLUG_GUEST_ERROR`` instead. 275 276 277System emulator machines 278------------------------ 279 280Aspeed ``swift-bmc`` machine (since 6.1) 281'''''''''''''''''''''''''''''''''''''''' 282 283This machine is deprecated because we have enough AST2500 based OpenPOWER 284machines. It can be easily replaced by the ``witherspoon-bmc`` or the 285``romulus-bmc`` machines. 286 287Backend options 288--------------- 289 290Using non-persistent backing file with pmem=on (since 6.1) 291'''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 292 293This option is used when ``memory-backend-file`` is consumed by emulated NVDIMM 294device. However enabling ``memory-backend-file.pmem`` option, when backing file 295is (a) not DAX capable or (b) not on a filesystem that support direct mapping 296of persistent memory, is not safe and may lead to data loss or corruption in case 297of host crash. 298Options are: 299 300 - modify VM configuration to set ``pmem=off`` to continue using fake NVDIMM 301 (without persistence guaranties) with backing file on non DAX storage 302 - move backing file to NVDIMM storage and keep ``pmem=on`` 303 (to have NVDIMM with persistence guaranties). 304 305Device options 306-------------- 307 308Emulated device options 309''''''''''''''''''''''' 310 311``-device virtio-blk,scsi=on|off`` (since 5.0) 312^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 313 314The virtio-blk SCSI passthrough feature is a legacy VIRTIO feature. VIRTIO 1.0 315and later do not support it because the virtio-scsi device was introduced for 316full SCSI support. Use virtio-scsi instead when SCSI passthrough is required. 317 318Note this also applies to ``-device virtio-blk-pci,scsi=on|off``, which is an 319alias. 320 321``-device sga`` (since 6.2) 322^^^^^^^^^^^^^^^^^^^^^^^^^^^ 323 324The ``sga`` device loads an option ROM for x86 targets which enables 325SeaBIOS to send messages to the serial console. SeaBIOS 1.11.0 onwards 326contains native support for this feature and thus use of the option 327ROM approach is obsolete. The native SeaBIOS support can be activated 328by using ``-machine graphics=off``. 329 330 331Block device options 332'''''''''''''''''''' 333 334``"backing": ""`` (since 2.12) 335^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 336 337In order to prevent QEMU from automatically opening an image's backing 338chain, use ``"backing": null`` instead. 339 340``rbd`` keyvalue pair encoded filenames: ``""`` (since 3.1) 341^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 342 343Options for ``rbd`` should be specified according to its runtime options, 344like other block drivers. Legacy parsing of keyvalue pair encoded 345filenames is useful to open images with the old format for backing files; 346These image files should be updated to use the current format. 347 348Example of legacy encoding:: 349 350 json:{"file.driver":"rbd", "file.filename":"rbd:rbd/name"} 351 352The above, converted to the current supported format:: 353 354 json:{"file.driver":"rbd", "file.pool":"rbd", "file.image":"name"} 355 356linux-user mode CPUs 357-------------------- 358 359``ppc64abi32`` CPUs (since 5.2) 360''''''''''''''''''''''''''''''' 361 362The ``ppc64abi32`` architecture has a number of issues which regularly 363trip up our CI testing and is suspected to be quite broken. For that 364reason the maintainers strongly suspect no one actually uses it. 365 366MIPS ``I7200`` CPU (since 5.2) 367'''''''''''''''''''''''''''''' 368 369The ``I7200`` guest CPU relies on the nanoMIPS ISA, which is deprecated 370(the ISA has never been upstreamed to a compiler toolchain). Therefore 371this CPU is also deprecated. 372 373Backwards compatibility 374----------------------- 375 376Runnability guarantee of CPU models (since 4.1) 377''''''''''''''''''''''''''''''''''''''''''''''' 378 379Previous versions of QEMU never changed existing CPU models in 380ways that introduced additional host software or hardware 381requirements to the VM. This allowed management software to 382safely change the machine type of an existing VM without 383introducing new requirements ("runnability guarantee"). This 384prevented CPU models from being updated to include CPU 385vulnerability mitigations, leaving guests vulnerable in the 386default configuration. 387 388The CPU model runnability guarantee won't apply anymore to 389existing CPU models. Management software that needs runnability 390guarantees must resolve the CPU model aliases using the 391``alias-of`` field returned by the ``query-cpu-definitions`` QMP 392command. 393 394While those guarantees are kept, the return value of 395``query-cpu-definitions`` will have existing CPU model aliases 396point to a version that doesn't break runnability guarantees 397(specifically, version 1 of those CPU models). In future QEMU 398versions, aliases will point to newer CPU model versions 399depending on the machine type, so management software must 400resolve CPU model aliases before starting a virtual machine. 401 402Guest Emulator ISAs 403------------------- 404 405nanoMIPS ISA 406'''''''''''' 407 408The ``nanoMIPS`` ISA has never been upstreamed to any compiler toolchain. 409As it is hard to generate binaries for it, declare it deprecated. 410