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