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 199QEMU API (QAPI) events 200---------------------- 201 202``MEM_UNPLUG_ERROR`` (since 6.2) 203'''''''''''''''''''''''''''''''''''''''''''''''''''''''' 204 205Use the more generic event ``DEVICE_UNPLUG_GUEST_ERROR`` instead. 206 207 208System emulator machines 209------------------------ 210 211Arm ``virt`` machine ``dtb-kaslr-seed`` property 212'''''''''''''''''''''''''''''''''''''''''''''''' 213 214The ``dtb-kaslr-seed`` property on the ``virt`` board has been 215deprecated; use the new name ``dtb-randomness`` instead. The new name 216better reflects the way this property affects all random data within 217the device tree blob, not just the ``kaslr-seed`` node. 218 219``pc-i440fx-1.4`` up to ``pc-i440fx-1.7`` (since 7.0) 220''''''''''''''''''''''''''''''''''''''''''''''''''''' 221 222These old machine types are quite neglected nowadays and thus might have 223various pitfalls with regards to live migration. Use a newer machine type 224instead. 225 226 227Backend options 228--------------- 229 230Using non-persistent backing file with pmem=on (since 6.1) 231'''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 232 233This option is used when ``memory-backend-file`` is consumed by emulated NVDIMM 234device. However enabling ``memory-backend-file.pmem`` option, when backing file 235is (a) not DAX capable or (b) not on a filesystem that support direct mapping 236of persistent memory, is not safe and may lead to data loss or corruption in case 237of host crash. 238Options are: 239 240 - modify VM configuration to set ``pmem=off`` to continue using fake NVDIMM 241 (without persistence guaranties) with backing file on non DAX storage 242 - move backing file to NVDIMM storage and keep ``pmem=on`` 243 (to have NVDIMM with persistence guaranties). 244 245Device options 246-------------- 247 248Emulated device options 249''''''''''''''''''''''' 250 251``-device virtio-blk,scsi=on|off`` (since 5.0) 252^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 253 254The virtio-blk SCSI passthrough feature is a legacy VIRTIO feature. VIRTIO 1.0 255and later do not support it because the virtio-scsi device was introduced for 256full SCSI support. Use virtio-scsi instead when SCSI passthrough is required. 257 258Note this also applies to ``-device virtio-blk-pci,scsi=on|off``, which is an 259alias. 260 261``-device nvme-ns,eui64-default=on|off`` (since 7.1) 262^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 263 264In QEMU versions 6.1, 6.2 and 7.0, the ``nvme-ns`` generates an EUI-64 265identifier that is not globally unique. If an EUI-64 identifier is required, the 266user must set it explicitly using the ``nvme-ns`` device parameter ``eui64``. 267 268``-device nvme,use-intel-id=on|off`` (since 7.1) 269^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 270 271The ``nvme`` device originally used a PCI Vendor/Device Identifier combination 272from Intel that was not properly allocated. Since version 5.2, the controller 273has used a properly allocated identifier. Deprecate the ``use-intel-id`` 274machine compatibility parameter. 275 276 277Block device options 278'''''''''''''''''''' 279 280``"backing": ""`` (since 2.12) 281^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 282 283In order to prevent QEMU from automatically opening an image's backing 284chain, use ``"backing": null`` instead. 285 286``rbd`` keyvalue pair encoded filenames: ``""`` (since 3.1) 287^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 288 289Options for ``rbd`` should be specified according to its runtime options, 290like other block drivers. Legacy parsing of keyvalue pair encoded 291filenames is useful to open images with the old format for backing files; 292These image files should be updated to use the current format. 293 294Example of legacy encoding:: 295 296 json:{"file.driver":"rbd", "file.filename":"rbd:rbd/name"} 297 298The above, converted to the current supported format:: 299 300 json:{"file.driver":"rbd", "file.pool":"rbd", "file.image":"name"} 301 302``iscsi,password=xxx`` (since 8.0) 303^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 304 305Specifying the iSCSI password in plain text on the command line using the 306``password`` option is insecure. The ``password-secret`` option should be 307used instead, to refer to a ``--object secret...`` instance that provides 308a password via a file, or encrypted. 309 310Backwards compatibility 311----------------------- 312 313Runnability guarantee of CPU models (since 4.1) 314''''''''''''''''''''''''''''''''''''''''''''''' 315 316Previous versions of QEMU never changed existing CPU models in 317ways that introduced additional host software or hardware 318requirements to the VM. This allowed management software to 319safely change the machine type of an existing VM without 320introducing new requirements ("runnability guarantee"). This 321prevented CPU models from being updated to include CPU 322vulnerability mitigations, leaving guests vulnerable in the 323default configuration. 324 325The CPU model runnability guarantee won't apply anymore to 326existing CPU models. Management software that needs runnability 327guarantees must resolve the CPU model aliases using the 328``alias-of`` field returned by the ``query-cpu-definitions`` QMP 329command. 330 331While those guarantees are kept, the return value of 332``query-cpu-definitions`` will have existing CPU model aliases 333point to a version that doesn't break runnability guarantees 334(specifically, version 1 of those CPU models). In future QEMU 335versions, aliases will point to newer CPU model versions 336depending on the machine type, so management software must 337resolve CPU model aliases before starting a virtual machine. 338 339QEMU guest agent 340---------------- 341 342``--blacklist`` command line option (since 7.2) 343''''''''''''''''''''''''''''''''''''''''''''''' 344 345``--blacklist`` has been replaced by ``--block-rpcs`` (which is a better 346wording for what this option does). The short form ``-b`` still stays 347the same and thus is the preferred way for scripts that should run with 348both, older and future versions of QEMU. 349 350``blacklist`` config file option (since 7.2) 351'''''''''''''''''''''''''''''''''''''''''''' 352 353The ``blacklist`` config file option has been renamed to ``block-rpcs`` 354(to be in sync with the renaming of the corresponding command line 355option). 356