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 42Short-form boolean options (since 6.0) 43'''''''''''''''''''''''''''''''''''''' 44 45Boolean options such as ``share=on``/``share=off`` could be written 46in short form as ``share`` and ``noshare``. This is now deprecated 47and will cause a warning. 48 49``delay`` option for socket character devices (since 6.0) 50''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 51 52The replacement for the ``nodelay`` short-form boolean option is ``nodelay=on`` 53rather than ``delay=off``. 54 55``-spice password=string`` (since 6.0) 56'''''''''''''''''''''''''''''''''''''' 57 58This option is insecure because the SPICE password remains visible in 59the process listing. This is replaced by the new ``password-secret`` 60option which lets the password be securely provided on the command 61line using a ``secret`` object instance. 62 63``-smp`` ("parameter=0" SMP configurations) (since 6.2) 64''''''''''''''''''''''''''''''''''''''''''''''''''''''' 65 66Specified CPU topology parameters must be greater than zero. 67 68In the SMP configuration, users should either provide a CPU topology 69parameter with a reasonable value (greater than zero) or just omit it 70and QEMU will compute the missing value. 71 72However, historically it was implicitly allowed for users to provide 73a parameter with zero value, which is meaningless and could also possibly 74cause unexpected results in the -smp parsing. So support for this kind of 75configurations (e.g. -smp 8,sockets=0) is deprecated since 6.2 and will 76be removed in the near future, users have to ensure that all the topology 77members described with -smp are greater than zero. 78 79Plugin argument passing through ``arg=<string>`` (since 6.1) 80'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 81 82Passing TCG plugins arguments through ``arg=`` is redundant is makes the 83command-line less readable, especially when the argument itself consist of a 84name and a value, e.g. ``-plugin plugin_name,arg="arg_name=arg_value"``. 85Therefore, the usage of ``arg`` is redundant. Single-word arguments are treated 86as short-form boolean values, and passed to plugins as ``arg_name=on``. 87However, short-form booleans are deprecated and full explicit ``arg_name=on`` 88form is preferred. 89 90``-drive if=none`` for the sifive_u OTP device (since 6.2) 91'''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 92 93Using ``-drive if=none`` to configure the OTP device of the sifive_u 94RISC-V machine is deprecated. Use ``-drive if=pflash`` instead. 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 103QEMU Machine Protocol (QMP) commands 104------------------------------------ 105 106``blockdev-open-tray``, ``blockdev-close-tray`` argument ``device`` (since 2.8) 107''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 108 109Use argument ``id`` instead. 110 111``eject`` argument ``device`` (since 2.8) 112''''''''''''''''''''''''''''''''''''''''' 113 114Use argument ``id`` instead. 115 116``blockdev-change-medium`` argument ``device`` (since 2.8) 117'''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 118 119Use argument ``id`` instead. 120 121``block_set_io_throttle`` argument ``device`` (since 2.8) 122''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 123 124Use argument ``id`` instead. 125 126``blockdev-add`` empty string argument ``backing`` (since 2.10) 127''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 128 129Use argument value ``null`` instead. 130 131``block-commit`` arguments ``base`` and ``top`` (since 3.1) 132''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 133 134Use arguments ``base-node`` and ``top-node`` instead. 135 136``nbd-server-add`` and ``nbd-server-remove`` (since 5.2) 137'''''''''''''''''''''''''''''''''''''''''''''''''''''''' 138 139Use the more generic commands ``block-export-add`` and ``block-export-del`` 140instead. As part of this deprecation, where ``nbd-server-add`` used a 141single ``bitmap``, the new ``block-export-add`` uses a list of ``bitmaps``. 142 143``query-qmp-schema`` return value member ``values`` (since 6.2) 144''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 145 146Member ``values`` in return value elements with meta-type ``enum`` is 147deprecated. Use ``members`` instead. 148 149``drive-backup`` (since 6.2) 150'''''''''''''''''''''''''''' 151 152Use ``blockdev-backup`` in combination with ``blockdev-add`` instead. 153This change primarily separates the creation/opening process of the backup 154target with explicit, separate steps. ``blockdev-backup`` uses mostly the 155same arguments as ``drive-backup``, except the ``format`` and ``mode`` 156options are removed in favor of using explicit ``blockdev-create`` and 157``blockdev-add`` calls. See :doc:`/interop/live-block-operations` for 158details. 159 160Incorrectly typed ``device_add`` arguments (since 6.2) 161'''''''''''''''''''''''''''''''''''''''''''''''''''''' 162 163Due to shortcomings in the internal implementation of ``device_add``, QEMU 164incorrectly accepts certain invalid arguments: Any object or list arguments are 165silently ignored. Other argument types are not checked, but an implicit 166conversion happens, so that e.g. string values can be assigned to integer 167device properties or vice versa. 168 169This is a bug in QEMU that will be fixed in the future so that previously 170accepted incorrect commands will return an error. Users should make sure that 171all arguments passed to ``device_add`` are consistent with the documented 172property types. 173 174System accelerators 175------------------- 176 177MIPS ``Trap-and-Emul`` KVM support (since 6.0) 178'''''''''''''''''''''''''''''''''''''''''''''' 179 180The MIPS ``Trap-and-Emul`` KVM host and guest support has been removed 181from Linux upstream kernel, declare it deprecated. 182 183Host Architectures 184------------------ 185 186BE MIPS (since 7.2) 187''''''''''''''''''' 188 189As Debian 10 ("Buster") moved into LTS the big endian 32 bit version of 190MIPS moved out of support making it hard to maintain our 191cross-compilation CI tests of the architecture. As we no longer have 192CI coverage support may bitrot away before the deprecation process 193completes. The little endian variants of MIPS (both 32 and 64 bit) are 194still a supported host architecture. 195 196QEMU API (QAPI) events 197---------------------- 198 199``MEM_UNPLUG_ERROR`` (since 6.2) 200'''''''''''''''''''''''''''''''''''''''''''''''''''''''' 201 202Use the more generic event ``DEVICE_UNPLUG_GUEST_ERROR`` instead. 203 204 205System emulator machines 206------------------------ 207 208Arm ``virt`` machine ``dtb-kaslr-seed`` property 209'''''''''''''''''''''''''''''''''''''''''''''''' 210 211The ``dtb-kaslr-seed`` property on the ``virt`` board has been 212deprecated; use the new name ``dtb-randomness`` instead. The new name 213better reflects the way this property affects all random data within 214the device tree blob, not just the ``kaslr-seed`` node. 215 216``pc-i440fx-1.4`` up to ``pc-i440fx-1.7`` (since 7.0) 217''''''''''''''''''''''''''''''''''''''''''''''''''''' 218 219These old machine types are quite neglected nowadays and thus might have 220various pitfalls with regards to live migration. Use a newer machine type 221instead. 222 223 224Backend options 225--------------- 226 227Using non-persistent backing file with pmem=on (since 6.1) 228'''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 229 230This option is used when ``memory-backend-file`` is consumed by emulated NVDIMM 231device. However enabling ``memory-backend-file.pmem`` option, when backing file 232is (a) not DAX capable or (b) not on a filesystem that support direct mapping 233of persistent memory, is not safe and may lead to data loss or corruption in case 234of host crash. 235Options are: 236 237 - modify VM configuration to set ``pmem=off`` to continue using fake NVDIMM 238 (without persistence guaranties) with backing file on non DAX storage 239 - move backing file to NVDIMM storage and keep ``pmem=on`` 240 (to have NVDIMM with persistence guaranties). 241 242Device options 243-------------- 244 245Emulated device options 246''''''''''''''''''''''' 247 248``-device virtio-blk,scsi=on|off`` (since 5.0) 249^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 250 251The virtio-blk SCSI passthrough feature is a legacy VIRTIO feature. VIRTIO 1.0 252and later do not support it because the virtio-scsi device was introduced for 253full SCSI support. Use virtio-scsi instead when SCSI passthrough is required. 254 255Note this also applies to ``-device virtio-blk-pci,scsi=on|off``, which is an 256alias. 257 258``-device sga`` (since 6.2) 259^^^^^^^^^^^^^^^^^^^^^^^^^^^ 260 261The ``sga`` device loads an option ROM for x86 targets which enables 262SeaBIOS to send messages to the serial console. SeaBIOS 1.11.0 onwards 263contains native support for this feature and thus use of the option 264ROM approach is obsolete. The native SeaBIOS support can be activated 265by using ``-machine graphics=off``. 266 267``-device nvme-ns,eui64-default=on|off`` (since 7.1) 268^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 269 270In QEMU versions 6.1, 6.2 and 7.0, the ``nvme-ns`` generates an EUI-64 271identifier that is not globally unique. If an EUI-64 identifier is required, the 272user must set it explicitly using the ``nvme-ns`` device parameter ``eui64``. 273 274``-device nvme,use-intel-id=on|off`` (since 7.1) 275^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 276 277The ``nvme`` device originally used a PCI Vendor/Device Identifier combination 278from Intel that was not properly allocated. Since version 5.2, the controller 279has used a properly allocated identifier. Deprecate the ``use-intel-id`` 280machine compatibility parameter. 281 282 283Block device options 284'''''''''''''''''''' 285 286``"backing": ""`` (since 2.12) 287^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 288 289In order to prevent QEMU from automatically opening an image's backing 290chain, use ``"backing": null`` instead. 291 292``rbd`` keyvalue pair encoded filenames: ``""`` (since 3.1) 293^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 294 295Options for ``rbd`` should be specified according to its runtime options, 296like other block drivers. Legacy parsing of keyvalue pair encoded 297filenames is useful to open images with the old format for backing files; 298These image files should be updated to use the current format. 299 300Example of legacy encoding:: 301 302 json:{"file.driver":"rbd", "file.filename":"rbd:rbd/name"} 303 304The above, converted to the current supported format:: 305 306 json:{"file.driver":"rbd", "file.pool":"rbd", "file.image":"name"} 307 308Backwards compatibility 309----------------------- 310 311Runnability guarantee of CPU models (since 4.1) 312''''''''''''''''''''''''''''''''''''''''''''''' 313 314Previous versions of QEMU never changed existing CPU models in 315ways that introduced additional host software or hardware 316requirements to the VM. This allowed management software to 317safely change the machine type of an existing VM without 318introducing new requirements ("runnability guarantee"). This 319prevented CPU models from being updated to include CPU 320vulnerability mitigations, leaving guests vulnerable in the 321default configuration. 322 323The CPU model runnability guarantee won't apply anymore to 324existing CPU models. Management software that needs runnability 325guarantees must resolve the CPU model aliases using the 326``alias-of`` field returned by the ``query-cpu-definitions`` QMP 327command. 328 329While those guarantees are kept, the return value of 330``query-cpu-definitions`` will have existing CPU model aliases 331point to a version that doesn't break runnability guarantees 332(specifically, version 1 of those CPU models). In future QEMU 333versions, aliases will point to newer CPU model versions 334depending on the machine type, so management software must 335resolve CPU model aliases before starting a virtual machine. 336 337Tools 338----- 339 340virtiofsd 341''''''''' 342 343There is a new Rust implementation of ``virtiofsd`` at 344``https://gitlab.com/virtio-fs/virtiofsd``; 345since this is now marked stable, new development should be done on that 346rather than the existing C version in the QEMU tree. 347The C version will still accept fixes and patches that 348are already in development for the moment, but will eventually 349be deleted from this tree. 350New deployments should use the Rust version, and existing systems 351should consider moving to it. The command line and feature set 352is very close and moving should be simple. 353 354 355QEMU guest agent 356---------------- 357 358``--blacklist`` command line option (since 7.2) 359''''''''''''''''''''''''''''''''''''''''''''''' 360 361``--blacklist`` has been replaced by ``--block-rpcs`` (which is a better 362wording for what this option does). The short form ``-b`` still stays 363the same and thus is the preferred way for scripts that should run with 364both, older and future versions of QEMU. 365 366``blacklist`` config file option (since 7.2) 367'''''''''''''''''''''''''''''''''''''''''''' 368 369The ``blacklist`` config file option has been renamed to ``block-rpcs`` 370(to be in sync with the renaming of the corresponding command line 371option). 372