| 1 | .. _Deprecated features: |
| 2 | |
| 3 | Deprecated features |
| 4 | =================== |
| 5 | |
| 6 | In general features are intended to be supported indefinitely once |
| 7 | introduced into QEMU. In the event that a feature needs to be removed, |
| 8 | it will be listed in this section. The feature will remain functional for the |
| 9 | release in which it was deprecated and one further release. After these two |
| 10 | releases, the feature is liable to be removed. Deprecated features may also |
| 11 | generate warnings on the console when QEMU starts up, or if activated via a |
| 12 | monitor command, however, this is not a mandatory requirement. |
| 13 | |
| 14 | As a special exception to this general timeframe, rather than have an |
| 15 | indefinite lifetime, versioned machine types are only intended to be |
| 16 | supported for a period of 6 years, equivalent to 18 QEMU releases. All |
| 17 | versioned machine types will be automatically marked deprecated after an |
| 18 | initial 3 years (9 QEMU releases) has passed, and will then be deleted after |
| 19 | a further 3 year period has passed. It is recommended that a deprecated |
| 20 | machine type is only used for incoming migrations and restore of saved state, |
| 21 | for pre-existing VM deployments. They should be scheduled for updating to a |
| 22 | newer machine type during an appropriate service window. Newly deployed VMs |
| 23 | should exclusively use a non-deprecated machine type, with use of the most |
| 24 | recent version highly recommended. Non-versioned machine types follow the |
| 25 | general feature deprecation policy. |
| 26 | |
| 27 | What follows is a list of all features currently marked as |
| 28 | deprecated. |
| 29 | |
| 30 | System emulator command line arguments |
| 31 | -------------------------------------- |
| 32 | |
| 33 | Short-form boolean options (since 6.0) |
| 34 | '''''''''''''''''''''''''''''''''''''' |
| 35 | |
| 36 | Boolean options such as ``share=on``/``share=off`` could be written |
| 37 | in short form as ``share`` and ``noshare``. This is now deprecated |
| 38 | and will cause a warning. |
| 39 | |
| 40 | ``delay`` option for socket character devices (since 6.0) |
| 41 | ''''''''''''''''''''''''''''''''''''''''''''''''''''''''' |
| 42 | |
| 43 | The replacement for the ``nodelay`` short-form boolean option is ``nodelay=on`` |
| 44 | rather than ``delay=off``. |
| 45 | |
| 46 | Plugin argument passing through ``arg=<string>`` (since 6.1) |
| 47 | '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' |
| 48 | |
| 49 | Passing TCG plugins arguments through ``arg=`` is redundant is makes the |
| 50 | command-line less readable, especially when the argument itself consist of a |
| 51 | name and a value, e.g. ``-plugin plugin_name,arg="arg_name=arg_value"``. |
| 52 | Therefore, the usage of ``arg`` is redundant. Single-word arguments are treated |
| 53 | as short-form boolean values, and passed to plugins as ``arg_name=on``. |
| 54 | However, short-form booleans are deprecated and full explicit ``arg_name=on`` |
| 55 | form is preferred. |
| 56 | |
| 57 | ``debug-threads`` option for ``-name`` (since 11.0) |
| 58 | ''''''''''''''''''''''''''''''''''''''''''''''''''' |
| 59 | |
| 60 | The ``debug-threads`` option of the ``-name`` argument is now |
| 61 | ignored. Thread naming is unconditionally enabled for all platforms |
| 62 | where it is supported. |
| 63 | |
| 64 | ``-mon`` option (since 11.1) |
| 65 | '''''''''''''''''''''''''''' |
| 66 | |
| 67 | The ``-mon`` option was the generic mechanism for creating monitor |
| 68 | objects if the convenience ``-qmp`` or ``-monitor`` options were not |
| 69 | flexible enough. The monitor objects have been converted to QOM, so |
| 70 | ``-mon mode=readline`` is replaced by ``-object monitor-hmp`` and |
| 71 | ``-mon mode=control`` is replaced by ``-object monitor-qmp``. The |
| 72 | short convenience options are not deprecated, only ``-mon``. |
| 73 | |
| 74 | QEMU Machine Protocol (QMP) commands |
| 75 | ------------------------------------ |
| 76 | |
| 77 | ``blockdev-open-tray``, ``blockdev-close-tray`` argument ``device`` (since 2.8) |
| 78 | ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' |
| 79 | |
| 80 | Use argument ``id`` instead. |
| 81 | |
| 82 | ``eject`` argument ``device`` (since 2.8) |
| 83 | ''''''''''''''''''''''''''''''''''''''''' |
| 84 | |
| 85 | Use argument ``id`` instead. |
| 86 | |
| 87 | ``blockdev-change-medium`` argument ``device`` (since 2.8) |
| 88 | '''''''''''''''''''''''''''''''''''''''''''''''''''''''''' |
| 89 | |
| 90 | Use argument ``id`` instead. |
| 91 | |
| 92 | ``block_set_io_throttle`` argument ``device`` (since 2.8) |
| 93 | ''''''''''''''''''''''''''''''''''''''''''''''''''''''''' |
| 94 | |
| 95 | Use argument ``id`` instead. |
| 96 | |
| 97 | ``blockdev-add`` empty string argument ``backing`` (since 2.10) |
| 98 | ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' |
| 99 | |
| 100 | Use argument value ``null`` instead. |
| 101 | |
| 102 | ``block-commit`` arguments ``base`` and ``top`` (since 3.1) |
| 103 | ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' |
| 104 | |
| 105 | Use arguments ``base-node`` and ``top-node`` instead. |
| 106 | |
| 107 | ``nbd-server-add`` and ``nbd-server-remove`` (since 5.2) |
| 108 | '''''''''''''''''''''''''''''''''''''''''''''''''''''''' |
| 109 | |
| 110 | Use the more generic commands ``block-export-add`` and ``block-export-del`` |
| 111 | instead. As part of this deprecation, where ``nbd-server-add`` used a |
| 112 | single ``bitmap``, the new ``block-export-add`` uses a list of ``bitmaps``. |
| 113 | |
| 114 | ``query-qmp-schema`` return value member ``values`` (since 6.2) |
| 115 | ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' |
| 116 | |
| 117 | Member ``values`` in return value elements with meta-type ``enum`` is |
| 118 | deprecated. Use ``members`` instead. |
| 119 | |
| 120 | ``drive-backup`` (since 6.2) |
| 121 | '''''''''''''''''''''''''''' |
| 122 | |
| 123 | Use ``blockdev-backup`` in combination with ``blockdev-add`` instead. |
| 124 | This change primarily separates the creation/opening process of the backup |
| 125 | target with explicit, separate steps. ``blockdev-backup`` uses mostly the |
| 126 | same arguments as ``drive-backup``, except the ``format`` and ``mode`` |
| 127 | options are removed in favor of using explicit ``blockdev-create`` and |
| 128 | ``blockdev-add`` calls. See :doc:`/interop/live-block-operations` for |
| 129 | details. |
| 130 | |
| 131 | ``block-job-pause`` (since 10.1) |
| 132 | '''''''''''''''''''''''''''''''' |
| 133 | |
| 134 | Use ``job-pause`` instead. The only difference is that ``job-pause`` |
| 135 | always reports GenericError on failure when ``block-job-pause`` reports |
| 136 | DeviceNotActive when block-job is not found. |
| 137 | |
| 138 | ``block-job-resume`` (since 10.1) |
| 139 | ''''''''''''''''''''''''''''''''' |
| 140 | |
| 141 | Use ``job-resume`` instead. The only difference is that ``job-resume`` |
| 142 | always reports GenericError on failure when ``block-job-resume`` reports |
| 143 | DeviceNotActive when block-job is not found. |
| 144 | |
| 145 | ``block-job-complete`` (since 10.1) |
| 146 | ''''''''''''''''''''''''''''''''''' |
| 147 | |
| 148 | Use ``job-complete`` instead. The only difference is that ``job-complete`` |
| 149 | always reports GenericError on failure when ``block-job-complete`` reports |
| 150 | DeviceNotActive when block-job is not found. |
| 151 | |
| 152 | ``block-job-dismiss`` (since 10.1) |
| 153 | '''''''''''''''''''''''''''''''''' |
| 154 | |
| 155 | Use ``job-dismiss`` instead. |
| 156 | |
| 157 | ``block-job-finalize`` (since 10.1) |
| 158 | ''''''''''''''''''''''''''''''''''' |
| 159 | |
| 160 | Use ``job-finalize`` instead. |
| 161 | |
| 162 | ``query-kvm`` (since 11.0) |
| 163 | '''''''''''''''''''''''''' |
| 164 | |
| 165 | Use ``query-accelerators`` instead. |
| 166 | |
| 167 | Human Machine Protocol (HMP) commands |
| 168 | ------------------------------------- |
| 169 | |
| 170 | ``wavcapture`` (since 10.2) |
| 171 | '''''''''''''''''''''''''''' |
| 172 | |
| 173 | The ``wavcapture`` command is deprecated and will be removed in a future release. |
| 174 | |
| 175 | Use ``-audiodev wav`` or your host audio system to capture audio. |
| 176 | |
| 177 | ``stopcapture`` (since 10.2) |
| 178 | '''''''''''''''''''''''''''' |
| 179 | |
| 180 | The ``stopcapture`` command is deprecated and will be removed in a future release. |
| 181 | |
| 182 | ``info`` argument ``capture`` (since 10.2) |
| 183 | '''''''''''''''''''''''''''''''''''''''''' |
| 184 | |
| 185 | The ``info capture`` command is deprecated and will be removed in a future release. |
| 186 | |
| 187 | Host Architectures |
| 188 | ------------------ |
| 189 | |
| 190 | TCG Plugin support not enabled by default with TCI (since 9.2) |
| 191 | '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' |
| 192 | |
| 193 | While the TCG interpreter can interpret the TCG ops used by plugins it |
| 194 | is going to be so much slower it wouldn't make sense for any serious |
| 195 | instrumentation. Due to implementation differences there will also be |
| 196 | anomalies in things like memory instrumentation. |
| 197 | |
| 198 | System emulator CPUs |
| 199 | -------------------- |
| 200 | |
| 201 | ``power5+`` and ``power7+`` CPU names (since 9.0) |
| 202 | ''''''''''''''''''''''''''''''''''''''''''''''''' |
| 203 | |
| 204 | The character "+" in device (and thus also CPU) names is not allowed |
| 205 | in the QEMU object model anymore. ``power5+``, ``power5+_v2.1``, |
| 206 | ``power7+`` and ``power7+_v2.1`` are currently still supported via |
| 207 | an alias, but for consistency these will get removed in a future |
| 208 | release, too. Use ``power5p_v2.1`` and ``power7p_v2.1`` instead. |
| 209 | |
| 210 | ``Sun-UltraSparc-IIIi+`` and ``Sun-UltraSparc-IV+`` CPU names (since 9.1) |
| 211 | ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' |
| 212 | |
| 213 | The character "+" in device (and thus also CPU) names is not allowed |
| 214 | in the QEMU object model anymore. ``Sun-UltraSparc-IIIi+`` and |
| 215 | ``Sun-UltraSparc-IV+`` are currently still supported via a workaround, |
| 216 | but for consistency these will get removed in a future release, too. |
| 217 | Use ``Sun-UltraSparc-IIIi-plus`` and ``Sun-UltraSparc-IV-plus`` instead. |
| 218 | |
| 219 | System emulator machines |
| 220 | ------------------------ |
| 221 | |
| 222 | Versioned machine types (aarch64, arm, i386, m68k, ppc64, s390x, x86_64) |
| 223 | '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' |
| 224 | |
| 225 | In accordance with our versioned machine type deprecation policy, all machine |
| 226 | types with version |VER_MACHINE_DEPRECATION_VERSION|, or older, have been |
| 227 | deprecated. |
| 228 | |
| 229 | Arm ``virt`` machine ``dtb-kaslr-seed`` property (since 7.1) |
| 230 | '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' |
| 231 | |
| 232 | The ``dtb-kaslr-seed`` property on the ``virt`` board has been |
| 233 | deprecated; use the new name ``dtb-randomness`` instead. The new name |
| 234 | better reflects the way this property affects all random data within |
| 235 | the device tree blob, not just the ``kaslr-seed`` node. |
| 236 | |
| 237 | RISC-V Shakti machine (since 11.1) |
| 238 | '''''''''''''''''''''''''''''''''' |
| 239 | |
| 240 | The RISC-V ``shakti_c`` machine hasn't had meaningful contributions since 2021 |
| 241 | and is currently unmaintained. The machine is scheduled to be removed as it |
| 242 | appears to have no users. |
| 243 | |
| 244 | ``memory-encryption`` machine property (since 11.1) |
| 245 | ''''''''''''''''''''''''''''''''''''''''''''''''''' |
| 246 | |
| 247 | Use ``confidential-guest-support`` instead. The ``memory-encryption`` object |
| 248 | was an early implementation of memory encryption support in QEMU, but it has |
| 249 | been superseded by the more comprehensive ``confidential-guest-support`` |
| 250 | object. |
| 251 | |
| 252 | Backend options |
| 253 | --------------- |
| 254 | |
| 255 | Using non-persistent backing file with pmem=on (since 6.1) |
| 256 | '''''''''''''''''''''''''''''''''''''''''''''''''''''''''' |
| 257 | |
| 258 | This option is used when ``memory-backend-file`` is consumed by emulated NVDIMM |
| 259 | device. However enabling ``memory-backend-file.pmem`` option, when backing file |
| 260 | is (a) not DAX capable or (b) not on a filesystem that support direct mapping |
| 261 | of persistent memory, is not safe and may lead to data loss or corruption in case |
| 262 | of host crash. |
| 263 | Options are: |
| 264 | |
| 265 | - modify VM configuration to set ``pmem=off`` to continue using fake NVDIMM |
| 266 | (without persistence guaranties) with backing file on non DAX storage |
| 267 | - move backing file to NVDIMM storage and keep ``pmem=on`` |
| 268 | (to have NVDIMM with persistence guaranties). |
| 269 | |
| 270 | Using an external DH (Diffie-Hellman) parameters file (since 10.2) |
| 271 | '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' |
| 272 | |
| 273 | Loading of external Diffie-Hellman parameters from a 'dh-params.pem' |
| 274 | file is deprecated and will be removed with no replacement in a |
| 275 | future release. Where no 'dh-params.pem' file is provided, the DH |
| 276 | parameters will be automatically negotiated in accordance with |
| 277 | RFC7919. |
| 278 | |
| 279 | Devices |
| 280 | ------- |
| 281 | |
| 282 | ``virtio-crypto`` and cryptodev backends (since 11.2) |
| 283 | ''''''''''''''''''''''''''''''''''''''''''''''''''''' |
| 284 | |
| 285 | The ``virtio-crypto`` device emulation is quite complex code with a |
| 286 | number of known flaws. It has never been migratable, so it is |
| 287 | unlikely to be used in any serious virtualization setting. Modern |
| 288 | ISAs provide on-CPU cryptography instructions (e.g. AES-NI/VAES, |
| 289 | armv8 crypto extensions), and the Linux kernel deprecated AF_ALG |
| 290 | and dropped its off-CPU accelerator support in Linux 7.2, removing |
| 291 | the primary userspace path for off-CPU crypto acceleration. The |
| 292 | time for this sort of off-load has passed. |
| 293 | |
| 294 | As this is the only device that uses the cryptodev backends these will |
| 295 | be removed at the same time the ``virtio-crypto`` device is. |
| 296 | |
| 297 | Device options |
| 298 | -------------- |
| 299 | |
| 300 | Emulated device options |
| 301 | ''''''''''''''''''''''' |
| 302 | |
| 303 | ``-device nvme-ns,eui64-default=on|off`` (since 7.1) |
| 304 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| 305 | |
| 306 | In QEMU versions 6.1, 6.2 and 7.0, the ``nvme-ns`` generates an EUI-64 |
| 307 | identifier that is not globally unique. If an EUI-64 identifier is required, the |
| 308 | user must set it explicitly using the ``nvme-ns`` device parameter ``eui64``. |
| 309 | |
| 310 | ``-device nvme,use-intel-id=on|off`` (since 7.1) |
| 311 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| 312 | |
| 313 | The ``nvme`` device originally used a PCI Vendor/Device Identifier combination |
| 314 | from Intel that was not properly allocated. Since version 5.2, the controller |
| 315 | has used a properly allocated identifier. Deprecate the ``use-intel-id`` |
| 316 | machine compatibility parameter. |
| 317 | |
| 318 | ``-device cxl-type3,memdev=xxxx`` (since 8.0) |
| 319 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| 320 | |
| 321 | The ``cxl-type3`` device initially only used a single memory backend. With |
| 322 | the addition of volatile memory support, it is now necessary to distinguish |
| 323 | between persistent and volatile memory backends. As such, memdev is deprecated |
| 324 | in favor of persistent-memdev. |
| 325 | |
| 326 | |
| 327 | RISC-V CPU properties which start with capital 'Z' (since 8.2) |
| 328 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| 329 | |
| 330 | All RISC-V CPU properties which start with capital 'Z' are being deprecated |
| 331 | starting in 8.2. The reason is that they were wrongly added with capital 'Z' |
| 332 | in the past. CPU properties were later added with lower-case names, which |
| 333 | is the format we want to use from now on. |
| 334 | |
| 335 | Users which try to use these deprecated properties will receive a warning |
| 336 | recommending to switch to their stable counterparts: |
| 337 | |
| 338 | - "Zifencei" should be replaced with "zifencei" |
| 339 | - "Zicsr" should be replaced with "zicsr" |
| 340 | - "Zihintntl" should be replaced with "zihintntl" |
| 341 | - "Zihintpause" should be replaced with "zihintpause" |
| 342 | - "Zawrs" should be replaced with "zawrs" |
| 343 | - "Zfa" should be replaced with "zfa" |
| 344 | - "Zfh" should be replaced with "zfh" |
| 345 | - "Zfhmin" should be replaced with "zfhmin" |
| 346 | - "Zve32f" should be replaced with "zve32f" |
| 347 | - "Zve64f" should be replaced with "zve64f" |
| 348 | - "Zve64d" should be replaced with "zve64d" |
| 349 | |
| 350 | Block device options |
| 351 | '''''''''''''''''''' |
| 352 | |
| 353 | ``"backing": ""`` (since 2.12) |
| 354 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| 355 | |
| 356 | In order to prevent QEMU from automatically opening an image's backing |
| 357 | chain, use ``"backing": null`` instead. |
| 358 | |
| 359 | ``rbd`` keyvalue pair encoded filenames: ``""`` (since 3.1) |
| 360 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| 361 | |
| 362 | Options for ``rbd`` should be specified according to its runtime options, |
| 363 | like other block drivers. Legacy parsing of keyvalue pair encoded |
| 364 | filenames is useful to open images with the old format for backing files; |
| 365 | These image files should be updated to use the current format. |
| 366 | |
| 367 | Example of legacy encoding:: |
| 368 | |
| 369 | json:{"file.driver":"rbd", "file.filename":"rbd:rbd/name"} |
| 370 | |
| 371 | The above, converted to the current supported format:: |
| 372 | |
| 373 | json:{"file.driver":"rbd", "file.pool":"rbd", "file.image":"name"} |
| 374 | |
| 375 | ``iscsi,password=xxx`` (since 8.0) |
| 376 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| 377 | |
| 378 | Specifying the iSCSI password in plain text on the command line using the |
| 379 | ``password`` option is insecure. The ``password-secret`` option should be |
| 380 | used instead, to refer to a ``--object secret...`` instance that provides |
| 381 | a password via a file, or encrypted. |
| 382 | |
| 383 | |
| 384 | Character device options |
| 385 | '''''''''''''''''''''''' |
| 386 | |
| 387 | Backend ``memory`` (since 9.0) |
| 388 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| 389 | |
| 390 | ``memory`` is a deprecated synonym for ``ringbuf``. |
| 391 | |
| 392 | |
| 393 | CPU device properties |
| 394 | ''''''''''''''''''''' |
| 395 | |
| 396 | ``pmu-num=n`` on RISC-V CPUs (since 8.2) |
| 397 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| 398 | |
| 399 | In order to support more flexible counter configurations this has been replaced |
| 400 | by a ``pmu-mask`` property. If set of counters is continuous then the mask can |
| 401 | be calculated with ``((2 ^ n) - 1) << 3``. The least significant three bits |
| 402 | must be left clear. |
| 403 | |
| 404 | |
| 405 | ``pcommit`` on x86 (since 9.1) |
| 406 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| 407 | |
| 408 | The PCOMMIT instruction was never included in any physical processor. |
| 409 | It was implemented as a no-op instruction in TCG up to QEMU 9.0, but |
| 410 | only with ``-cpu max`` (which does not guarantee migration compatibility |
| 411 | across versions). |
| 412 | |
| 413 | linux-user mode CPUs |
| 414 | -------------------- |
| 415 | |
| 416 | OABI and NWFPE support for Arm CPUs |
| 417 | ''''''''''''''''''''''''''''''''''' |
| 418 | |
| 419 | Linux for 32-bit Arm has had two major ABIs: the original OABI and the |
| 420 | more modern EABI. OABI support was marked as obsolete in GCC 4.7 and |
| 421 | dropped in GCC 4.8 (released in 2013). In the Linux kernel, |
| 422 | compatibility handling for OABI (OABI_COMPAT) is not generally enabled |
| 423 | by default and is not compatible with building a Thumb2 |
| 424 | kernel. Distros dropped OABI support fifteen years or more ago. |
| 425 | |
| 426 | The original floating-point coprocessor for 32-bit Arm was the |
| 427 | FPA11. This was not present in many CPUs but did get baked into the |
| 428 | OABI for how to pass floating point arguments, and so the Linux kernel |
| 429 | has support for emulating it via the config option FPE_NWFPE; QEMU |
| 430 | follows that. FPA11 support was also removed from GCC in GCC 4.8. |
| 431 | |
| 432 | QEMU's NWFPE code is old and untested and not thread-safe; the OABI |
| 433 | ABI is long-obsolete. We are therefore deprecating both OABI support |
| 434 | and NWFPE emulation, and they will be removed in a future QEMU |
| 435 | release. |
| 436 | |
| 437 | |
| 438 | Backwards compatibility |
| 439 | ----------------------- |
| 440 | |
| 441 | Runnability guarantee of CPU models (since 4.1) |
| 442 | ''''''''''''''''''''''''''''''''''''''''''''''' |
| 443 | |
| 444 | Previous versions of QEMU never changed existing CPU models in |
| 445 | ways that introduced additional host software or hardware |
| 446 | requirements to the VM. This allowed management software to |
| 447 | safely change the machine type of an existing VM without |
| 448 | introducing new requirements ("runnability guarantee"). This |
| 449 | prevented CPU models from being updated to include CPU |
| 450 | vulnerability mitigations, leaving guests vulnerable in the |
| 451 | default configuration. |
| 452 | |
| 453 | The CPU model runnability guarantee won't apply anymore to |
| 454 | existing CPU models. Management software that needs runnability |
| 455 | guarantees must resolve the CPU model aliases using the |
| 456 | ``alias-of`` field returned by the ``query-cpu-definitions`` QMP |
| 457 | command. |
| 458 | |
| 459 | While those guarantees are kept, the return value of |
| 460 | ``query-cpu-definitions`` will have existing CPU model aliases |
| 461 | point to a version that doesn't break runnability guarantees |
| 462 | (specifically, version 1 of those CPU models). In future QEMU |
| 463 | versions, aliases will point to newer CPU model versions |
| 464 | depending on the machine type, so management software must |
| 465 | resolve CPU model aliases before starting a virtual machine. |
| 466 | |
| 467 | x86 "isapc" board use of modern x86 CPUs (since 10.2) |
| 468 | ''''''''''''''''''''''''''''''''''''''''''''''''''''' |
| 469 | |
| 470 | The "isapc" board represents a historical x86 ISA PC and is intended for |
| 471 | older 32-bit x86 CPU models, defaulting to a 486 CPU model. Previously it |
| 472 | was possible (but non-sensical) to specify a more modern x86 CPU, including |
| 473 | ``-cpu host`` or ``-cpu max`` even if the features were incompatible with many |
| 474 | of the intended guest OSs. |
| 475 | |
| 476 | If the user requests a modern x86 CPU model (i.e. not one of ``486``, |
| 477 | ``athlon``, ``kvm32``, ``pentium``, ``pentium2``, ``pentium3``or ``qemu32``) |
| 478 | a warning will be displayed until a future QEMU version when such CPUs will |
| 479 | be rejected. |