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``-smp`` ("parameter=0" SMP configurations) (since 6.2) 164''''''''''''''''''''''''''''''''''''''''''''''''''''''' 165 166Specified CPU topology parameters must be greater than zero. 167 168In the SMP configuration, users should either provide a CPU topology 169parameter with a reasonable value (greater than zero) or just omit it 170and QEMU will compute the missing value. 171 172However, historically it was implicitly allowed for users to provide 173a parameter with zero value, which is meaningless and could also possibly 174cause unexpected results in the -smp parsing. So support for this kind of 175configurations (e.g. -smp 8,sockets=0) is deprecated since 6.2 and will 176be removed in the near future, users have to ensure that all the topology 177members described with -smp are greater than zero. 178 179Plugin argument passing through ``arg=<string>`` (since 6.1) 180'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 181 182Passing TCG plugins arguments through ``arg=`` is redundant is makes the 183command-line less readable, especially when the argument itself consist of a 184name and a value, e.g. ``-plugin plugin_name,arg="arg_name=arg_value"``. 185Therefore, the usage of ``arg`` is redundant. Single-word arguments are treated 186as short-form boolean values, and passed to plugins as ``arg_name=on``. 187However, short-form booleans are deprecated and full explicit ``arg_name=on`` 188form is preferred. 189 190 191QEMU Machine Protocol (QMP) commands 192------------------------------------ 193 194``blockdev-open-tray``, ``blockdev-close-tray`` argument ``device`` (since 2.8) 195''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 196 197Use argument ``id`` instead. 198 199``eject`` argument ``device`` (since 2.8) 200''''''''''''''''''''''''''''''''''''''''' 201 202Use argument ``id`` instead. 203 204``blockdev-change-medium`` argument ``device`` (since 2.8) 205'''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 206 207Use argument ``id`` instead. 208 209``block_set_io_throttle`` argument ``device`` (since 2.8) 210''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 211 212Use argument ``id`` instead. 213 214``blockdev-add`` empty string argument ``backing`` (since 2.10) 215''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 216 217Use argument value ``null`` instead. 218 219``block-commit`` arguments ``base`` and ``top`` (since 3.1) 220''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 221 222Use arguments ``base-node`` and ``top-node`` instead. 223 224``nbd-server-add`` and ``nbd-server-remove`` (since 5.2) 225'''''''''''''''''''''''''''''''''''''''''''''''''''''''' 226 227Use the more generic commands ``block-export-add`` and ``block-export-del`` 228instead. As part of this deprecation, where ``nbd-server-add`` used a 229single ``bitmap``, the new ``block-export-add`` uses a list of ``bitmaps``. 230 231System accelerators 232------------------- 233 234MIPS ``Trap-and-Emul`` KVM support (since 6.0) 235'''''''''''''''''''''''''''''''''''''''''''''' 236 237The MIPS ``Trap-and-Emul`` KVM host and guest support has been removed 238from Linux upstream kernel, declare it deprecated. 239 240System emulator CPUS 241-------------------- 242 243``Icelake-Client`` CPU Model (since 5.2) 244'''''''''''''''''''''''''''''''''''''''' 245 246``Icelake-Client`` CPU Models are deprecated. Use ``Icelake-Server`` CPU 247Models instead. 248 249MIPS ``I7200`` CPU Model (since 5.2) 250'''''''''''''''''''''''''''''''''''' 251 252The ``I7200`` guest CPU relies on the nanoMIPS ISA, which is deprecated 253(the ISA has never been upstreamed to a compiler toolchain). Therefore 254this CPU is also deprecated. 255 256 257QEMU API (QAPI) events 258---------------------- 259 260``MEM_UNPLUG_ERROR`` (since 6.2) 261'''''''''''''''''''''''''''''''''''''''''''''''''''''''' 262 263Use the more generic event ``DEVICE_UNPLUG_GUEST_ERROR`` instead. 264 265 266System emulator machines 267------------------------ 268 269Aspeed ``swift-bmc`` machine (since 6.1) 270'''''''''''''''''''''''''''''''''''''''' 271 272This machine is deprecated because we have enough AST2500 based OpenPOWER 273machines. It can be easily replaced by the ``witherspoon-bmc`` or the 274``romulus-bmc`` machines. 275 276Backend options 277--------------- 278 279Using non-persistent backing file with pmem=on (since 6.1) 280'''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 281 282This option is used when ``memory-backend-file`` is consumed by emulated NVDIMM 283device. However enabling ``memory-backend-file.pmem`` option, when backing file 284is (a) not DAX capable or (b) not on a filesystem that support direct mapping 285of persistent memory, is not safe and may lead to data loss or corruption in case 286of host crash. 287Options are: 288 289 - modify VM configuration to set ``pmem=off`` to continue using fake NVDIMM 290 (without persistence guaranties) with backing file on non DAX storage 291 - move backing file to NVDIMM storage and keep ``pmem=on`` 292 (to have NVDIMM with persistence guaranties). 293 294Device options 295-------------- 296 297Emulated device options 298''''''''''''''''''''''' 299 300``-device virtio-blk,scsi=on|off`` (since 5.0) 301^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 302 303The virtio-blk SCSI passthrough feature is a legacy VIRTIO feature. VIRTIO 1.0 304and later do not support it because the virtio-scsi device was introduced for 305full SCSI support. Use virtio-scsi instead when SCSI passthrough is required. 306 307Note this also applies to ``-device virtio-blk-pci,scsi=on|off``, which is an 308alias. 309 310Block device options 311'''''''''''''''''''' 312 313``"backing": ""`` (since 2.12) 314^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 315 316In order to prevent QEMU from automatically opening an image's backing 317chain, use ``"backing": null`` instead. 318 319``rbd`` keyvalue pair encoded filenames: ``""`` (since 3.1) 320^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 321 322Options for ``rbd`` should be specified according to its runtime options, 323like other block drivers. Legacy parsing of keyvalue pair encoded 324filenames is useful to open images with the old format for backing files; 325These image files should be updated to use the current format. 326 327Example of legacy encoding:: 328 329 json:{"file.driver":"rbd", "file.filename":"rbd:rbd/name"} 330 331The above, converted to the current supported format:: 332 333 json:{"file.driver":"rbd", "file.pool":"rbd", "file.image":"name"} 334 335linux-user mode CPUs 336-------------------- 337 338``ppc64abi32`` CPUs (since 5.2) 339''''''''''''''''''''''''''''''' 340 341The ``ppc64abi32`` architecture has a number of issues which regularly 342trip up our CI testing and is suspected to be quite broken. For that 343reason the maintainers strongly suspect no one actually uses it. 344 345MIPS ``I7200`` CPU (since 5.2) 346'''''''''''''''''''''''''''''' 347 348The ``I7200`` guest CPU relies on the nanoMIPS ISA, which is deprecated 349(the ISA has never been upstreamed to a compiler toolchain). Therefore 350this CPU is also deprecated. 351 352Related binaries 353---------------- 354 355Backwards compatibility 356----------------------- 357 358Runnability guarantee of CPU models (since 4.1) 359''''''''''''''''''''''''''''''''''''''''''''''' 360 361Previous versions of QEMU never changed existing CPU models in 362ways that introduced additional host software or hardware 363requirements to the VM. This allowed management software to 364safely change the machine type of an existing VM without 365introducing new requirements ("runnability guarantee"). This 366prevented CPU models from being updated to include CPU 367vulnerability mitigations, leaving guests vulnerable in the 368default configuration. 369 370The CPU model runnability guarantee won't apply anymore to 371existing CPU models. Management software that needs runnability 372guarantees must resolve the CPU model aliases using the 373``alias-of`` field returned by the ``query-cpu-definitions`` QMP 374command. 375 376While those guarantees are kept, the return value of 377``query-cpu-definitions`` will have existing CPU model aliases 378point to a version that doesn't break runnability guarantees 379(specifically, version 1 of those CPU models). In future QEMU 380versions, aliases will point to newer CPU model versions 381depending on the machine type, so management software must 382resolve CPU model aliases before starting a virtual machine. 383 384Guest Emulator ISAs 385------------------- 386 387nanoMIPS ISA 388'''''''''''' 389 390The ``nanoMIPS`` ISA has never been upstreamed to any compiler toolchain. 391As it is hard to generate binaries for it, declare it deprecated. 392