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 115QEMU Machine Protocol (QMP) commands 116------------------------------------ 117 118``blockdev-open-tray``, ``blockdev-close-tray`` argument ``device`` (since 2.8) 119''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 120 121Use argument ``id`` instead. 122 123``eject`` argument ``device`` (since 2.8) 124''''''''''''''''''''''''''''''''''''''''' 125 126Use argument ``id`` instead. 127 128``blockdev-change-medium`` argument ``device`` (since 2.8) 129'''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 130 131Use argument ``id`` instead. 132 133``block_set_io_throttle`` argument ``device`` (since 2.8) 134''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 135 136Use argument ``id`` instead. 137 138``blockdev-add`` empty string argument ``backing`` (since 2.10) 139''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 140 141Use argument value ``null`` instead. 142 143``block-commit`` arguments ``base`` and ``top`` (since 3.1) 144''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 145 146Use arguments ``base-node`` and ``top-node`` instead. 147 148``nbd-server-add`` and ``nbd-server-remove`` (since 5.2) 149'''''''''''''''''''''''''''''''''''''''''''''''''''''''' 150 151Use the more generic commands ``block-export-add`` and ``block-export-del`` 152instead. As part of this deprecation, where ``nbd-server-add`` used a 153single ``bitmap``, the new ``block-export-add`` uses a list of ``bitmaps``. 154 155``query-qmp-schema`` return value member ``values`` (since 6.2) 156''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 157 158Member ``values`` in return value elements with meta-type ``enum`` is 159deprecated. Use ``members`` instead. 160 161``drive-backup`` (since 6.2) 162'''''''''''''''''''''''''''' 163 164Use ``blockdev-backup`` in combination with ``blockdev-add`` instead. 165This change primarily separates the creation/opening process of the backup 166target with explicit, separate steps. ``blockdev-backup`` uses mostly the 167same arguments as ``drive-backup``, except the ``format`` and ``mode`` 168options are removed in favor of using explicit ``blockdev-create`` and 169``blockdev-add`` calls. See :doc:`/interop/live-block-operations` for 170details. 171 172Incorrectly typed ``device_add`` arguments (since 6.2) 173'''''''''''''''''''''''''''''''''''''''''''''''''''''' 174 175Due to shortcomings in the internal implementation of ``device_add``, QEMU 176incorrectly accepts certain invalid arguments: Any object or list arguments are 177silently ignored. Other argument types are not checked, but an implicit 178conversion happens, so that e.g. string values can be assigned to integer 179device properties or vice versa. 180 181This is a bug in QEMU that will be fixed in the future so that previously 182accepted incorrect commands will return an error. Users should make sure that 183all arguments passed to ``device_add`` are consistent with the documented 184property types. 185 186Host Architectures 187------------------ 188 189BE MIPS (since 7.2) 190''''''''''''''''''' 191 192As Debian 10 ("Buster") moved into LTS the big endian 32 bit version of 193MIPS moved out of support making it hard to maintain our 194cross-compilation CI tests of the architecture. As we no longer have 195CI coverage support may bitrot away before the deprecation process 196completes. The little endian variants of MIPS (both 32 and 64 bit) are 197still a supported host architecture. 198 199System emulation on 32-bit x86 hosts (since 8.0) 200'''''''''''''''''''''''''''''''''''''''''''''''' 201 202Support for 32-bit x86 host deployments is increasingly uncommon in mainstream 203OS distributions given the widespread availability of 64-bit x86 hardware. 204The QEMU project no longer considers 32-bit x86 support for system emulation to 205be an effective use of its limited resources, and thus intends to discontinue 206it. Since all recent x86 hardware from the past >10 years is capable of the 20764-bit x86 extensions, a corresponding 64-bit OS should be used instead. 208 209 210QEMU API (QAPI) events 211---------------------- 212 213``MEM_UNPLUG_ERROR`` (since 6.2) 214'''''''''''''''''''''''''''''''''''''''''''''''''''''''' 215 216Use the more generic event ``DEVICE_UNPLUG_GUEST_ERROR`` instead. 217 218 219System emulator machines 220------------------------ 221 222Arm ``virt`` machine ``dtb-kaslr-seed`` property 223'''''''''''''''''''''''''''''''''''''''''''''''' 224 225The ``dtb-kaslr-seed`` property on the ``virt`` board has been 226deprecated; use the new name ``dtb-randomness`` instead. The new name 227better reflects the way this property affects all random data within 228the device tree blob, not just the ``kaslr-seed`` node. 229 230``pc-i440fx-1.4`` up to ``pc-i440fx-1.7`` (since 7.0) 231''''''''''''''''''''''''''''''''''''''''''''''''''''' 232 233These old machine types are quite neglected nowadays and thus might have 234various pitfalls with regards to live migration. Use a newer machine type 235instead. 236 237 238Backend options 239--------------- 240 241Using non-persistent backing file with pmem=on (since 6.1) 242'''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 243 244This option is used when ``memory-backend-file`` is consumed by emulated NVDIMM 245device. However enabling ``memory-backend-file.pmem`` option, when backing file 246is (a) not DAX capable or (b) not on a filesystem that support direct mapping 247of persistent memory, is not safe and may lead to data loss or corruption in case 248of host crash. 249Options are: 250 251 - modify VM configuration to set ``pmem=off`` to continue using fake NVDIMM 252 (without persistence guaranties) with backing file on non DAX storage 253 - move backing file to NVDIMM storage and keep ``pmem=on`` 254 (to have NVDIMM with persistence guaranties). 255 256Device options 257-------------- 258 259Emulated device options 260''''''''''''''''''''''' 261 262``-device virtio-blk,scsi=on|off`` (since 5.0) 263^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 264 265The virtio-blk SCSI passthrough feature is a legacy VIRTIO feature. VIRTIO 1.0 266and later do not support it because the virtio-scsi device was introduced for 267full SCSI support. Use virtio-scsi instead when SCSI passthrough is required. 268 269Note this also applies to ``-device virtio-blk-pci,scsi=on|off``, which is an 270alias. 271 272``-device nvme-ns,eui64-default=on|off`` (since 7.1) 273^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 274 275In QEMU versions 6.1, 6.2 and 7.0, the ``nvme-ns`` generates an EUI-64 276identifier that is not globally unique. If an EUI-64 identifier is required, the 277user must set it explicitly using the ``nvme-ns`` device parameter ``eui64``. 278 279``-device nvme,use-intel-id=on|off`` (since 7.1) 280^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 281 282The ``nvme`` device originally used a PCI Vendor/Device Identifier combination 283from Intel that was not properly allocated. Since version 5.2, the controller 284has used a properly allocated identifier. Deprecate the ``use-intel-id`` 285machine compatibility parameter. 286 287 288Block device options 289'''''''''''''''''''' 290 291``"backing": ""`` (since 2.12) 292^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 293 294In order to prevent QEMU from automatically opening an image's backing 295chain, use ``"backing": null`` instead. 296 297``rbd`` keyvalue pair encoded filenames: ``""`` (since 3.1) 298^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 299 300Options for ``rbd`` should be specified according to its runtime options, 301like other block drivers. Legacy parsing of keyvalue pair encoded 302filenames is useful to open images with the old format for backing files; 303These image files should be updated to use the current format. 304 305Example of legacy encoding:: 306 307 json:{"file.driver":"rbd", "file.filename":"rbd:rbd/name"} 308 309The above, converted to the current supported format:: 310 311 json:{"file.driver":"rbd", "file.pool":"rbd", "file.image":"name"} 312 313``iscsi,password=xxx`` (since 8.0) 314^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 315 316Specifying the iSCSI password in plain text on the command line using the 317``password`` option is insecure. The ``password-secret`` option should be 318used instead, to refer to a ``--object secret...`` instance that provides 319a password via a file, or encrypted. 320 321Backwards compatibility 322----------------------- 323 324Runnability guarantee of CPU models (since 4.1) 325''''''''''''''''''''''''''''''''''''''''''''''' 326 327Previous versions of QEMU never changed existing CPU models in 328ways that introduced additional host software or hardware 329requirements to the VM. This allowed management software to 330safely change the machine type of an existing VM without 331introducing new requirements ("runnability guarantee"). This 332prevented CPU models from being updated to include CPU 333vulnerability mitigations, leaving guests vulnerable in the 334default configuration. 335 336The CPU model runnability guarantee won't apply anymore to 337existing CPU models. Management software that needs runnability 338guarantees must resolve the CPU model aliases using the 339``alias-of`` field returned by the ``query-cpu-definitions`` QMP 340command. 341 342While those guarantees are kept, the return value of 343``query-cpu-definitions`` will have existing CPU model aliases 344point to a version that doesn't break runnability guarantees 345(specifically, version 1 of those CPU models). In future QEMU 346versions, aliases will point to newer CPU model versions 347depending on the machine type, so management software must 348resolve CPU model aliases before starting a virtual machine. 349 350QEMU guest agent 351---------------- 352 353``--blacklist`` command line option (since 7.2) 354''''''''''''''''''''''''''''''''''''''''''''''' 355 356``--blacklist`` has been replaced by ``--block-rpcs`` (which is a better 357wording for what this option does). The short form ``-b`` still stays 358the same and thus is the preferred way for scripts that should run with 359both, older and future versions of QEMU. 360 361``blacklist`` config file option (since 7.2) 362'''''''''''''''''''''''''''''''''''''''''''' 363 364The ``blacklist`` config file option has been renamed to ``block-rpcs`` 365(to be in sync with the renaming of the corresponding command line 366option). 367