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 23Build options 24------------- 25 26``gprof`` builds (since 8.0) 27'''''''''''''''''''''''''''' 28 29The ``--enable-gprof`` configure setting relies on compiler 30instrumentation to gather its data which can distort the generated 31profile. As other non-instrumenting tools are available that give a 32more holistic view of the system with non-instrumented binaries we are 33deprecating the build option and no longer defend it in CI. The 34``--enable-gcov`` build option remains for analysis test case 35coverage. 36 37System emulator command line arguments 38-------------------------------------- 39 40``QEMU_AUDIO_`` environment variables and ``-audio-help`` (since 4.0) 41''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 42 43The ``-audiodev`` argument is now the preferred way to specify audio 44backend settings instead of environment variables. To ease migration to 45the new format, the ``-audiodev-help`` option can be used to convert 46the current values of the environment variables to ``-audiodev`` options. 47 48Creating sound card devices and vnc without ``audiodev=`` property (since 4.2) 49'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 50 51When not using the deprecated legacy audio config, each sound card 52should specify an ``audiodev=`` property. Additionally, when using 53vnc, you should specify an ``audiodev=`` property if you plan to 54transmit audio through the VNC protocol. 55 56Short-form boolean options (since 6.0) 57'''''''''''''''''''''''''''''''''''''' 58 59Boolean options such as ``share=on``/``share=off`` could be written 60in short form as ``share`` and ``noshare``. This is now deprecated 61and will cause a warning. 62 63``delay`` option for socket character devices (since 6.0) 64''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 65 66The replacement for the ``nodelay`` short-form boolean option is ``nodelay=on`` 67rather than ``delay=off``. 68 69``-smp`` ("parameter=0" SMP configurations) (since 6.2) 70''''''''''''''''''''''''''''''''''''''''''''''''''''''' 71 72Specified CPU topology parameters must be greater than zero. 73 74In the SMP configuration, users should either provide a CPU topology 75parameter with a reasonable value (greater than zero) or just omit it 76and QEMU will compute the missing value. 77 78However, historically it was implicitly allowed for users to provide 79a parameter with zero value, which is meaningless and could also possibly 80cause unexpected results in the -smp parsing. So support for this kind of 81configurations (e.g. -smp 8,sockets=0) is deprecated since 6.2 and will 82be removed in the near future, users have to ensure that all the topology 83members described with -smp are greater than zero. 84 85Plugin argument passing through ``arg=<string>`` (since 6.1) 86'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 87 88Passing TCG plugins arguments through ``arg=`` is redundant is makes the 89command-line less readable, especially when the argument itself consist of a 90name and a value, e.g. ``-plugin plugin_name,arg="arg_name=arg_value"``. 91Therefore, the usage of ``arg`` is redundant. Single-word arguments are treated 92as short-form boolean values, and passed to plugins as ``arg_name=on``. 93However, short-form booleans are deprecated and full explicit ``arg_name=on`` 94form is preferred. 95 96``-no-hpet`` (since 8.0) 97'''''''''''''''''''''''' 98 99The HPET setting has been turned into a machine property. 100Use ``-machine hpet=off`` instead. 101 102``-no-acpi`` (since 8.0) 103'''''''''''''''''''''''' 104 105The ``-no-acpi`` setting has been turned into a machine property. 106Use ``-machine acpi=off`` instead. 107 108``-accel hax`` (since 8.0) 109'''''''''''''''''''''''''' 110 111The HAXM project has been retired (see https://github.com/intel/haxm#status). 112Use "whpx" (on Windows) or "hvf" (on macOS) instead. 113 114``-singlestep`` (since 8.1) 115''''''''''''''''''''''''''' 116 117The ``-singlestep`` option has been turned into an accelerator property, 118and given a name that better reflects what it actually does. 119Use ``-accel tcg,one-insn-per-tb=on`` instead. 120 121User-mode emulator command line arguments 122----------------------------------------- 123 124``-singlestep`` (since 8.1) 125''''''''''''''''''''''''''' 126 127The ``-singlestep`` option has been given a name that better reflects 128what it actually does. For both linux-user and bsd-user, use the 129new ``-one-insn-per-tb`` option instead. 130 131QEMU Machine Protocol (QMP) commands 132------------------------------------ 133 134``blockdev-open-tray``, ``blockdev-close-tray`` argument ``device`` (since 2.8) 135''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 136 137Use argument ``id`` instead. 138 139``eject`` argument ``device`` (since 2.8) 140''''''''''''''''''''''''''''''''''''''''' 141 142Use argument ``id`` instead. 143 144``blockdev-change-medium`` argument ``device`` (since 2.8) 145'''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 146 147Use argument ``id`` instead. 148 149``block_set_io_throttle`` argument ``device`` (since 2.8) 150''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 151 152Use argument ``id`` instead. 153 154``blockdev-add`` empty string argument ``backing`` (since 2.10) 155''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 156 157Use argument value ``null`` instead. 158 159``block-commit`` arguments ``base`` and ``top`` (since 3.1) 160''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 161 162Use arguments ``base-node`` and ``top-node`` instead. 163 164``nbd-server-add`` and ``nbd-server-remove`` (since 5.2) 165'''''''''''''''''''''''''''''''''''''''''''''''''''''''' 166 167Use the more generic commands ``block-export-add`` and ``block-export-del`` 168instead. As part of this deprecation, where ``nbd-server-add`` used a 169single ``bitmap``, the new ``block-export-add`` uses a list of ``bitmaps``. 170 171``query-qmp-schema`` return value member ``values`` (since 6.2) 172''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 173 174Member ``values`` in return value elements with meta-type ``enum`` is 175deprecated. Use ``members`` instead. 176 177``drive-backup`` (since 6.2) 178'''''''''''''''''''''''''''' 179 180Use ``blockdev-backup`` in combination with ``blockdev-add`` instead. 181This change primarily separates the creation/opening process of the backup 182target with explicit, separate steps. ``blockdev-backup`` uses mostly the 183same arguments as ``drive-backup``, except the ``format`` and ``mode`` 184options are removed in favor of using explicit ``blockdev-create`` and 185``blockdev-add`` calls. See :doc:`/interop/live-block-operations` for 186details. 187 188Incorrectly typed ``device_add`` arguments (since 6.2) 189'''''''''''''''''''''''''''''''''''''''''''''''''''''' 190 191Due to shortcomings in the internal implementation of ``device_add``, QEMU 192incorrectly accepts certain invalid arguments: Any object or list arguments are 193silently ignored. Other argument types are not checked, but an implicit 194conversion happens, so that e.g. string values can be assigned to integer 195device properties or vice versa. 196 197This is a bug in QEMU that will be fixed in the future so that previously 198accepted incorrect commands will return an error. Users should make sure that 199all arguments passed to ``device_add`` are consistent with the documented 200property types. 201 202Host Architectures 203------------------ 204 205BE MIPS (since 7.2) 206''''''''''''''''''' 207 208As Debian 10 ("Buster") moved into LTS the big endian 32 bit version of 209MIPS moved out of support making it hard to maintain our 210cross-compilation CI tests of the architecture. As we no longer have 211CI coverage support may bitrot away before the deprecation process 212completes. The little endian variants of MIPS (both 32 and 64 bit) are 213still a supported host architecture. 214 215System emulation on 32-bit x86 hosts (since 8.0) 216'''''''''''''''''''''''''''''''''''''''''''''''' 217 218Support for 32-bit x86 host deployments is increasingly uncommon in mainstream 219OS distributions given the widespread availability of 64-bit x86 hardware. 220The QEMU project no longer considers 32-bit x86 support for system emulation to 221be an effective use of its limited resources, and thus intends to discontinue 222it. Since all recent x86 hardware from the past >10 years is capable of the 22364-bit x86 extensions, a corresponding 64-bit OS should be used instead. 224 225 226QEMU API (QAPI) events 227---------------------- 228 229``MEM_UNPLUG_ERROR`` (since 6.2) 230'''''''''''''''''''''''''''''''''''''''''''''''''''''''' 231 232Use the more generic event ``DEVICE_UNPLUG_GUEST_ERROR`` instead. 233 234 235System emulator machines 236------------------------ 237 238Arm ``virt`` machine ``dtb-kaslr-seed`` property 239'''''''''''''''''''''''''''''''''''''''''''''''' 240 241The ``dtb-kaslr-seed`` property on the ``virt`` board has been 242deprecated; use the new name ``dtb-randomness`` instead. The new name 243better reflects the way this property affects all random data within 244the device tree blob, not just the ``kaslr-seed`` node. 245 246``pc-i440fx-1.4`` up to ``pc-i440fx-1.7`` (since 7.0) 247''''''''''''''''''''''''''''''''''''''''''''''''''''' 248 249These old machine types are quite neglected nowadays and thus might have 250various pitfalls with regards to live migration. Use a newer machine type 251instead. 252 253 254Backend options 255--------------- 256 257Using non-persistent backing file with pmem=on (since 6.1) 258'''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 259 260This option is used when ``memory-backend-file`` is consumed by emulated NVDIMM 261device. However enabling ``memory-backend-file.pmem`` option, when backing file 262is (a) not DAX capable or (b) not on a filesystem that support direct mapping 263of persistent memory, is not safe and may lead to data loss or corruption in case 264of host crash. 265Options are: 266 267 - modify VM configuration to set ``pmem=off`` to continue using fake NVDIMM 268 (without persistence guaranties) with backing file on non DAX storage 269 - move backing file to NVDIMM storage and keep ``pmem=on`` 270 (to have NVDIMM with persistence guaranties). 271 272Device options 273-------------- 274 275Emulated device options 276''''''''''''''''''''''' 277 278``-device virtio-blk,scsi=on|off`` (since 5.0) 279^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 280 281The virtio-blk SCSI passthrough feature is a legacy VIRTIO feature. VIRTIO 1.0 282and later do not support it because the virtio-scsi device was introduced for 283full SCSI support. Use virtio-scsi instead when SCSI passthrough is required. 284 285Note this also applies to ``-device virtio-blk-pci,scsi=on|off``, which is an 286alias. 287 288``-device nvme-ns,eui64-default=on|off`` (since 7.1) 289^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 290 291In QEMU versions 6.1, 6.2 and 7.0, the ``nvme-ns`` generates an EUI-64 292identifier that is not globally unique. If an EUI-64 identifier is required, the 293user must set it explicitly using the ``nvme-ns`` device parameter ``eui64``. 294 295``-device nvme,use-intel-id=on|off`` (since 7.1) 296^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 297 298The ``nvme`` device originally used a PCI Vendor/Device Identifier combination 299from Intel that was not properly allocated. Since version 5.2, the controller 300has used a properly allocated identifier. Deprecate the ``use-intel-id`` 301machine compatibility parameter. 302 303 304Block device options 305'''''''''''''''''''' 306 307``"backing": ""`` (since 2.12) 308^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 309 310In order to prevent QEMU from automatically opening an image's backing 311chain, use ``"backing": null`` instead. 312 313``rbd`` keyvalue pair encoded filenames: ``""`` (since 3.1) 314^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 315 316Options for ``rbd`` should be specified according to its runtime options, 317like other block drivers. Legacy parsing of keyvalue pair encoded 318filenames is useful to open images with the old format for backing files; 319These image files should be updated to use the current format. 320 321Example of legacy encoding:: 322 323 json:{"file.driver":"rbd", "file.filename":"rbd:rbd/name"} 324 325The above, converted to the current supported format:: 326 327 json:{"file.driver":"rbd", "file.pool":"rbd", "file.image":"name"} 328 329``iscsi,password=xxx`` (since 8.0) 330^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 331 332Specifying the iSCSI password in plain text on the command line using the 333``password`` option is insecure. The ``password-secret`` option should be 334used instead, to refer to a ``--object secret...`` instance that provides 335a password via a file, or encrypted. 336 337Backwards compatibility 338----------------------- 339 340Runnability guarantee of CPU models (since 4.1) 341''''''''''''''''''''''''''''''''''''''''''''''' 342 343Previous versions of QEMU never changed existing CPU models in 344ways that introduced additional host software or hardware 345requirements to the VM. This allowed management software to 346safely change the machine type of an existing VM without 347introducing new requirements ("runnability guarantee"). This 348prevented CPU models from being updated to include CPU 349vulnerability mitigations, leaving guests vulnerable in the 350default configuration. 351 352The CPU model runnability guarantee won't apply anymore to 353existing CPU models. Management software that needs runnability 354guarantees must resolve the CPU model aliases using the 355``alias-of`` field returned by the ``query-cpu-definitions`` QMP 356command. 357 358While those guarantees are kept, the return value of 359``query-cpu-definitions`` will have existing CPU model aliases 360point to a version that doesn't break runnability guarantees 361(specifically, version 1 of those CPU models). In future QEMU 362versions, aliases will point to newer CPU model versions 363depending on the machine type, so management software must 364resolve CPU model aliases before starting a virtual machine. 365 366QEMU guest agent 367---------------- 368 369``--blacklist`` command line option (since 7.2) 370''''''''''''''''''''''''''''''''''''''''''''''' 371 372``--blacklist`` has been replaced by ``--block-rpcs`` (which is a better 373wording for what this option does). The short form ``-b`` still stays 374the same and thus is the preferred way for scripts that should run with 375both, older and future versions of QEMU. 376 377``blacklist`` config file option (since 7.2) 378'''''''''''''''''''''''''''''''''''''''''''' 379 380The ``blacklist`` config file option has been renamed to ``block-rpcs`` 381(to be in sync with the renaming of the corresponding command line 382option). 383