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 202Human Monitor Protocol (HMP) commands 203------------------------------------- 204 205``singlestep`` (since 8.1) 206'''''''''''''''''''''''''' 207 208The ``singlestep`` command has been replaced by the ``one-insn-per-tb`` 209command, which has the same behaviour but a less misleading name. 210 211Host Architectures 212------------------ 213 214BE MIPS (since 7.2) 215''''''''''''''''''' 216 217As Debian 10 ("Buster") moved into LTS the big endian 32 bit version of 218MIPS moved out of support making it hard to maintain our 219cross-compilation CI tests of the architecture. As we no longer have 220CI coverage support may bitrot away before the deprecation process 221completes. The little endian variants of MIPS (both 32 and 64 bit) are 222still a supported host architecture. 223 224System emulation on 32-bit x86 hosts (since 8.0) 225'''''''''''''''''''''''''''''''''''''''''''''''' 226 227Support for 32-bit x86 host deployments is increasingly uncommon in mainstream 228OS distributions given the widespread availability of 64-bit x86 hardware. 229The QEMU project no longer considers 32-bit x86 support for system emulation to 230be an effective use of its limited resources, and thus intends to discontinue 231it. Since all recent x86 hardware from the past >10 years is capable of the 23264-bit x86 extensions, a corresponding 64-bit OS should be used instead. 233 234 235QEMU API (QAPI) events 236---------------------- 237 238``MEM_UNPLUG_ERROR`` (since 6.2) 239'''''''''''''''''''''''''''''''''''''''''''''''''''''''' 240 241Use the more generic event ``DEVICE_UNPLUG_GUEST_ERROR`` instead. 242 243 244System emulator machines 245------------------------ 246 247Arm ``virt`` machine ``dtb-kaslr-seed`` property 248'''''''''''''''''''''''''''''''''''''''''''''''' 249 250The ``dtb-kaslr-seed`` property on the ``virt`` board has been 251deprecated; use the new name ``dtb-randomness`` instead. The new name 252better reflects the way this property affects all random data within 253the device tree blob, not just the ``kaslr-seed`` node. 254 255``pc-i440fx-1.4`` up to ``pc-i440fx-1.7`` (since 7.0) 256''''''''''''''''''''''''''''''''''''''''''''''''''''' 257 258These old machine types are quite neglected nowadays and thus might have 259various pitfalls with regards to live migration. Use a newer machine type 260instead. 261 262 263Backend options 264--------------- 265 266Using non-persistent backing file with pmem=on (since 6.1) 267'''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 268 269This option is used when ``memory-backend-file`` is consumed by emulated NVDIMM 270device. However enabling ``memory-backend-file.pmem`` option, when backing file 271is (a) not DAX capable or (b) not on a filesystem that support direct mapping 272of persistent memory, is not safe and may lead to data loss or corruption in case 273of host crash. 274Options are: 275 276 - modify VM configuration to set ``pmem=off`` to continue using fake NVDIMM 277 (without persistence guaranties) with backing file on non DAX storage 278 - move backing file to NVDIMM storage and keep ``pmem=on`` 279 (to have NVDIMM with persistence guaranties). 280 281Device options 282-------------- 283 284Emulated device options 285''''''''''''''''''''''' 286 287``-device virtio-blk,scsi=on|off`` (since 5.0) 288^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 289 290The virtio-blk SCSI passthrough feature is a legacy VIRTIO feature. VIRTIO 1.0 291and later do not support it because the virtio-scsi device was introduced for 292full SCSI support. Use virtio-scsi instead when SCSI passthrough is required. 293 294Note this also applies to ``-device virtio-blk-pci,scsi=on|off``, which is an 295alias. 296 297``-device nvme-ns,eui64-default=on|off`` (since 7.1) 298^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 299 300In QEMU versions 6.1, 6.2 and 7.0, the ``nvme-ns`` generates an EUI-64 301identifier that is not globally unique. If an EUI-64 identifier is required, the 302user must set it explicitly using the ``nvme-ns`` device parameter ``eui64``. 303 304``-device nvme,use-intel-id=on|off`` (since 7.1) 305^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 306 307The ``nvme`` device originally used a PCI Vendor/Device Identifier combination 308from Intel that was not properly allocated. Since version 5.2, the controller 309has used a properly allocated identifier. Deprecate the ``use-intel-id`` 310machine compatibility parameter. 311 312 313Block device options 314'''''''''''''''''''' 315 316``"backing": ""`` (since 2.12) 317^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 318 319In order to prevent QEMU from automatically opening an image's backing 320chain, use ``"backing": null`` instead. 321 322``rbd`` keyvalue pair encoded filenames: ``""`` (since 3.1) 323^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 324 325Options for ``rbd`` should be specified according to its runtime options, 326like other block drivers. Legacy parsing of keyvalue pair encoded 327filenames is useful to open images with the old format for backing files; 328These image files should be updated to use the current format. 329 330Example of legacy encoding:: 331 332 json:{"file.driver":"rbd", "file.filename":"rbd:rbd/name"} 333 334The above, converted to the current supported format:: 335 336 json:{"file.driver":"rbd", "file.pool":"rbd", "file.image":"name"} 337 338``iscsi,password=xxx`` (since 8.0) 339^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 340 341Specifying the iSCSI password in plain text on the command line using the 342``password`` option is insecure. The ``password-secret`` option should be 343used instead, to refer to a ``--object secret...`` instance that provides 344a password via a file, or encrypted. 345 346Backwards compatibility 347----------------------- 348 349Runnability guarantee of CPU models (since 4.1) 350''''''''''''''''''''''''''''''''''''''''''''''' 351 352Previous versions of QEMU never changed existing CPU models in 353ways that introduced additional host software or hardware 354requirements to the VM. This allowed management software to 355safely change the machine type of an existing VM without 356introducing new requirements ("runnability guarantee"). This 357prevented CPU models from being updated to include CPU 358vulnerability mitigations, leaving guests vulnerable in the 359default configuration. 360 361The CPU model runnability guarantee won't apply anymore to 362existing CPU models. Management software that needs runnability 363guarantees must resolve the CPU model aliases using the 364``alias-of`` field returned by the ``query-cpu-definitions`` QMP 365command. 366 367While those guarantees are kept, the return value of 368``query-cpu-definitions`` will have existing CPU model aliases 369point to a version that doesn't break runnability guarantees 370(specifically, version 1 of those CPU models). In future QEMU 371versions, aliases will point to newer CPU model versions 372depending on the machine type, so management software must 373resolve CPU model aliases before starting a virtual machine. 374 375QEMU guest agent 376---------------- 377 378``--blacklist`` command line option (since 7.2) 379''''''''''''''''''''''''''''''''''''''''''''''' 380 381``--blacklist`` has been replaced by ``--block-rpcs`` (which is a better 382wording for what this option does). The short form ``-b`` still stays 383the same and thus is the preferred way for scripts that should run with 384both, older and future versions of QEMU. 385 386``blacklist`` config file option (since 7.2) 387'''''''''''''''''''''''''''''''''''''''''''' 388 389The ``blacklist`` config file option has been renamed to ``block-rpcs`` 390(to be in sync with the renaming of the corresponding command line 391option). 392