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``-alt-grab`` and ``-display sdl,alt_grab=on`` (since 6.2) 138'''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 139 140Use ``-display sdl,grab-mod=lshift-lctrl-lalt`` instead. 141 142``-ctrl-grab`` and ``-display sdl,ctrl_grab=on`` (since 6.2) 143'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 144 145Use ``-display sdl,grab-mod=rctrl`` instead. 146 147``-sdl`` (since 6.2) 148'''''''''''''''''''' 149 150Use ``-display sdl`` instead. 151 152``-curses`` (since 6.2) 153''''''''''''''''''''''' 154 155Use ``-display curses`` instead. 156 157``-watchdog`` (since 6.2) 158''''''''''''''''''''''''' 159 160Use ``-device`` instead. 161 162``-smp`` ("parameter=0" SMP configurations) (since 6.2) 163''''''''''''''''''''''''''''''''''''''''''''''''''''''' 164 165Specified CPU topology parameters must be greater than zero. 166 167In the SMP configuration, users should either provide a CPU topology 168parameter with a reasonable value (greater than zero) or just omit it 169and QEMU will compute the missing value. 170 171However, historically it was implicitly allowed for users to provide 172a parameter with zero value, which is meaningless and could also possibly 173cause unexpected results in the -smp parsing. So support for this kind of 174configurations (e.g. -smp 8,sockets=0) is deprecated since 6.2 and will 175be removed in the near future, users have to ensure that all the topology 176members described with -smp are greater than zero. 177 178Plugin argument passing through ``arg=<string>`` (since 6.1) 179'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 180 181Passing TCG plugins arguments through ``arg=`` is redundant is makes the 182command-line less readable, especially when the argument itself consist of a 183name and a value, e.g. ``-plugin plugin_name,arg="arg_name=arg_value"``. 184Therefore, the usage of ``arg`` is redundant. Single-word arguments are treated 185as short-form boolean values, and passed to plugins as ``arg_name=on``. 186However, short-form booleans are deprecated and full explicit ``arg_name=on`` 187form is preferred. 188 189``-drive if=none`` for the sifive_u OTP device (since 6.2) 190'''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 191 192Using ``-drive if=none`` to configure the OTP device of the sifive_u 193RISC-V machine is deprecated. Use ``-drive if=pflash`` instead. 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. 241 242``drive-backup`` (since 6.2) 243'''''''''''''''''''''''''''' 244 245Use ``blockdev-backup`` in combination with ``blockdev-add`` instead. 246This change primarily separates the creation/opening process of the backup 247target with explicit, separate steps. ``blockdev-backup`` uses mostly the 248same arguments as ``drive-backup``, except the ``format`` and ``mode`` 249options are removed in favor of using explicit ``blockdev-create`` and 250``blockdev-add`` calls. See :doc:`/interop/live-block-operations` for 251details. 252 253Incorrectly typed ``device_add`` arguments (since 6.2) 254'''''''''''''''''''''''''''''''''''''''''''''''''''''' 255 256Due to shortcomings in the internal implementation of ``device_add``, QEMU 257incorrectly accepts certain invalid arguments: Any object or list arguments are 258silently ignored. Other argument types are not checked, but an implicit 259conversion happens, so that e.g. string values can be assigned to integer 260device properties or vice versa. 261 262This is a bug in QEMU that will be fixed in the future so that previously 263accepted incorrect commands will return an error. Users should make sure that 264all arguments passed to ``device_add`` are consistent with the documented 265property types. 266 267System accelerators 268------------------- 269 270MIPS ``Trap-and-Emul`` KVM support (since 6.0) 271'''''''''''''''''''''''''''''''''''''''''''''' 272 273The MIPS ``Trap-and-Emul`` KVM host and guest support has been removed 274from Linux upstream kernel, declare it deprecated. 275 276System emulator CPUS 277-------------------- 278 279``Icelake-Client`` CPU Model (since 5.2) 280'''''''''''''''''''''''''''''''''''''''' 281 282``Icelake-Client`` CPU Models are deprecated. Use ``Icelake-Server`` CPU 283Models instead. 284 285MIPS ``I7200`` CPU Model (since 5.2) 286'''''''''''''''''''''''''''''''''''' 287 288The ``I7200`` guest CPU relies on the nanoMIPS ISA, which is deprecated 289(the ISA has never been upstreamed to a compiler toolchain). Therefore 290this CPU is also deprecated. 291 292 293QEMU API (QAPI) events 294---------------------- 295 296``MEM_UNPLUG_ERROR`` (since 6.2) 297'''''''''''''''''''''''''''''''''''''''''''''''''''''''' 298 299Use the more generic event ``DEVICE_UNPLUG_GUEST_ERROR`` instead. 300 301 302System emulator machines 303------------------------ 304 305Aspeed ``swift-bmc`` machine (since 6.1) 306'''''''''''''''''''''''''''''''''''''''' 307 308This machine is deprecated because we have enough AST2500 based OpenPOWER 309machines. It can be easily replaced by the ``witherspoon-bmc`` or the 310``romulus-bmc`` machines. 311 312PPC 405 ``taihu`` machine (since 7.0) 313''''''''''''''''''''''''''''''''''''' 314 315The PPC 405 CPU is a system-on-a-chip, so all 405 machines are very similar, 316except for some external periphery. However, the periphery of the ``taihu`` 317machine is hardly emulated at all (e.g. neither the LCD nor the USB part had 318been implemented), so there is not much value added by this board. Use the 319``ref405ep`` machine instead. 320 321Backend options 322--------------- 323 324Using non-persistent backing file with pmem=on (since 6.1) 325'''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 326 327This option is used when ``memory-backend-file`` is consumed by emulated NVDIMM 328device. However enabling ``memory-backend-file.pmem`` option, when backing file 329is (a) not DAX capable or (b) not on a filesystem that support direct mapping 330of persistent memory, is not safe and may lead to data loss or corruption in case 331of host crash. 332Options are: 333 334 - modify VM configuration to set ``pmem=off`` to continue using fake NVDIMM 335 (without persistence guaranties) with backing file on non DAX storage 336 - move backing file to NVDIMM storage and keep ``pmem=on`` 337 (to have NVDIMM with persistence guaranties). 338 339Device options 340-------------- 341 342Emulated device options 343''''''''''''''''''''''' 344 345``-device virtio-blk,scsi=on|off`` (since 5.0) 346^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 347 348The virtio-blk SCSI passthrough feature is a legacy VIRTIO feature. VIRTIO 1.0 349and later do not support it because the virtio-scsi device was introduced for 350full SCSI support. Use virtio-scsi instead when SCSI passthrough is required. 351 352Note this also applies to ``-device virtio-blk-pci,scsi=on|off``, which is an 353alias. 354 355``-device sga`` (since 6.2) 356^^^^^^^^^^^^^^^^^^^^^^^^^^^ 357 358The ``sga`` device loads an option ROM for x86 targets which enables 359SeaBIOS to send messages to the serial console. SeaBIOS 1.11.0 onwards 360contains native support for this feature and thus use of the option 361ROM approach is obsolete. The native SeaBIOS support can be activated 362by using ``-machine graphics=off``. 363 364 365Block device options 366'''''''''''''''''''' 367 368``"backing": ""`` (since 2.12) 369^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 370 371In order to prevent QEMU from automatically opening an image's backing 372chain, use ``"backing": null`` instead. 373 374``rbd`` keyvalue pair encoded filenames: ``""`` (since 3.1) 375^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 376 377Options for ``rbd`` should be specified according to its runtime options, 378like other block drivers. Legacy parsing of keyvalue pair encoded 379filenames is useful to open images with the old format for backing files; 380These image files should be updated to use the current format. 381 382Example of legacy encoding:: 383 384 json:{"file.driver":"rbd", "file.filename":"rbd:rbd/name"} 385 386The above, converted to the current supported format:: 387 388 json:{"file.driver":"rbd", "file.pool":"rbd", "file.image":"name"} 389 390linux-user mode CPUs 391-------------------- 392 393``ppc64abi32`` CPUs (since 5.2) 394''''''''''''''''''''''''''''''' 395 396The ``ppc64abi32`` architecture has a number of issues which regularly 397trip up our CI testing and is suspected to be quite broken. For that 398reason the maintainers strongly suspect no one actually uses it. 399 400MIPS ``I7200`` CPU (since 5.2) 401'''''''''''''''''''''''''''''' 402 403The ``I7200`` guest CPU relies on the nanoMIPS ISA, which is deprecated 404(the ISA has never been upstreamed to a compiler toolchain). Therefore 405this CPU is also deprecated. 406 407Backwards compatibility 408----------------------- 409 410Runnability guarantee of CPU models (since 4.1) 411''''''''''''''''''''''''''''''''''''''''''''''' 412 413Previous versions of QEMU never changed existing CPU models in 414ways that introduced additional host software or hardware 415requirements to the VM. This allowed management software to 416safely change the machine type of an existing VM without 417introducing new requirements ("runnability guarantee"). This 418prevented CPU models from being updated to include CPU 419vulnerability mitigations, leaving guests vulnerable in the 420default configuration. 421 422The CPU model runnability guarantee won't apply anymore to 423existing CPU models. Management software that needs runnability 424guarantees must resolve the CPU model aliases using the 425``alias-of`` field returned by the ``query-cpu-definitions`` QMP 426command. 427 428While those guarantees are kept, the return value of 429``query-cpu-definitions`` will have existing CPU model aliases 430point to a version that doesn't break runnability guarantees 431(specifically, version 1 of those CPU models). In future QEMU 432versions, aliases will point to newer CPU model versions 433depending on the machine type, so management software must 434resolve CPU model aliases before starting a virtual machine. 435 436Guest Emulator ISAs 437------------------- 438 439nanoMIPS ISA 440'''''''''''' 441 442The ``nanoMIPS`` ISA has never been upstreamed to any compiler toolchain. 443As it is hard to generate binaries for it, declare it deprecated. 444