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 42``-chardev`` backend aliases ``tty`` and ``parport`` (since 6.0) 43'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 44 45``tty`` and ``parport`` are aliases that will be removed. Instead, the 46actual backend names ``serial`` and ``parallel`` should be used. 47 48Short-form boolean options (since 6.0) 49'''''''''''''''''''''''''''''''''''''' 50 51Boolean options such as ``share=on``/``share=off`` could be written 52in short form as ``share`` and ``noshare``. This is now deprecated 53and will cause a warning. 54 55``delay`` option for socket character devices (since 6.0) 56''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 57 58The replacement for the ``nodelay`` short-form boolean option is ``nodelay=on`` 59rather than ``delay=off``. 60 61Userspace local APIC with KVM (x86, since 6.0) 62'''''''''''''''''''''''''''''''''''''''''''''' 63 64Using ``-M kernel-irqchip=off`` with x86 machine types that include a local 65APIC is deprecated. The ``split`` setting is supported, as is using 66``-M kernel-irqchip=off`` with the ISA PC machine type. 67 68hexadecimal sizes with scaling multipliers (since 6.0) 69'''''''''''''''''''''''''''''''''''''''''''''''''''''' 70 71Input parameters that take a size value should only use a size suffix 72(such as 'k' or 'M') when the base is written in decimal, and not when 73the value is hexadecimal. That is, '0x20M' is deprecated, and should 74be written either as '32M' or as '0x2000000'. 75 76``-spice password=string`` (since 6.0) 77'''''''''''''''''''''''''''''''''''''' 78 79This option is insecure because the SPICE password remains visible in 80the process listing. This is replaced by the new ``password-secret`` 81option which lets the password be securely provided on the command 82line using a ``secret`` object instance. 83 84``-watchdog`` (since 6.2) 85''''''''''''''''''''''''' 86 87Use ``-device`` instead. 88 89``-smp`` ("parameter=0" SMP configurations) (since 6.2) 90''''''''''''''''''''''''''''''''''''''''''''''''''''''' 91 92Specified CPU topology parameters must be greater than zero. 93 94In the SMP configuration, users should either provide a CPU topology 95parameter with a reasonable value (greater than zero) or just omit it 96and QEMU will compute the missing value. 97 98However, historically it was implicitly allowed for users to provide 99a parameter with zero value, which is meaningless and could also possibly 100cause unexpected results in the -smp parsing. So support for this kind of 101configurations (e.g. -smp 8,sockets=0) is deprecated since 6.2 and will 102be removed in the near future, users have to ensure that all the topology 103members described with -smp are greater than zero. 104 105Plugin argument passing through ``arg=<string>`` (since 6.1) 106'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 107 108Passing TCG plugins arguments through ``arg=`` is redundant is makes the 109command-line less readable, especially when the argument itself consist of a 110name and a value, e.g. ``-plugin plugin_name,arg="arg_name=arg_value"``. 111Therefore, the usage of ``arg`` is redundant. Single-word arguments are treated 112as short-form boolean values, and passed to plugins as ``arg_name=on``. 113However, short-form booleans are deprecated and full explicit ``arg_name=on`` 114form is preferred. 115 116``-drive if=none`` for the sifive_u OTP device (since 6.2) 117'''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 118 119Using ``-drive if=none`` to configure the OTP device of the sifive_u 120RISC-V machine is deprecated. Use ``-drive if=pflash`` instead. 121 122 123QEMU Machine Protocol (QMP) commands 124------------------------------------ 125 126``blockdev-open-tray``, ``blockdev-close-tray`` argument ``device`` (since 2.8) 127''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 128 129Use argument ``id`` instead. 130 131``eject`` argument ``device`` (since 2.8) 132''''''''''''''''''''''''''''''''''''''''' 133 134Use argument ``id`` instead. 135 136``blockdev-change-medium`` argument ``device`` (since 2.8) 137'''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 138 139Use argument ``id`` instead. 140 141``block_set_io_throttle`` argument ``device`` (since 2.8) 142''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 143 144Use argument ``id`` instead. 145 146``blockdev-add`` empty string argument ``backing`` (since 2.10) 147''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 148 149Use argument value ``null`` instead. 150 151``block-commit`` arguments ``base`` and ``top`` (since 3.1) 152''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 153 154Use arguments ``base-node`` and ``top-node`` instead. 155 156``nbd-server-add`` and ``nbd-server-remove`` (since 5.2) 157'''''''''''''''''''''''''''''''''''''''''''''''''''''''' 158 159Use the more generic commands ``block-export-add`` and ``block-export-del`` 160instead. As part of this deprecation, where ``nbd-server-add`` used a 161single ``bitmap``, the new ``block-export-add`` uses a list of ``bitmaps``. 162 163``query-qmp-schema`` return value member ``values`` (since 6.2) 164''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 165 166Member ``values`` in return value elements with meta-type ``enum`` is 167deprecated. Use ``members`` instead. 168 169``drive-backup`` (since 6.2) 170'''''''''''''''''''''''''''' 171 172Use ``blockdev-backup`` in combination with ``blockdev-add`` instead. 173This change primarily separates the creation/opening process of the backup 174target with explicit, separate steps. ``blockdev-backup`` uses mostly the 175same arguments as ``drive-backup``, except the ``format`` and ``mode`` 176options are removed in favor of using explicit ``blockdev-create`` and 177``blockdev-add`` calls. See :doc:`/interop/live-block-operations` for 178details. 179 180Incorrectly typed ``device_add`` arguments (since 6.2) 181'''''''''''''''''''''''''''''''''''''''''''''''''''''' 182 183Due to shortcomings in the internal implementation of ``device_add``, QEMU 184incorrectly accepts certain invalid arguments: Any object or list arguments are 185silently ignored. Other argument types are not checked, but an implicit 186conversion happens, so that e.g. string values can be assigned to integer 187device properties or vice versa. 188 189This is a bug in QEMU that will be fixed in the future so that previously 190accepted incorrect commands will return an error. Users should make sure that 191all arguments passed to ``device_add`` are consistent with the documented 192property types. 193 194``query-sgx`` return value member ``section-size`` (since 7.0) 195'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 196 197Member ``section-size`` in return value elements with meta-type ``uint64`` is 198deprecated. Use ``sections`` instead. 199 200 201``query-sgx-capabilities`` return value member ``section-size`` (since 7.0) 202''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 203 204Member ``section-size`` in return value elements with meta-type ``uint64`` is 205deprecated. Use ``sections`` instead. 206 207System accelerators 208------------------- 209 210MIPS ``Trap-and-Emul`` KVM support (since 6.0) 211'''''''''''''''''''''''''''''''''''''''''''''' 212 213The MIPS ``Trap-and-Emul`` KVM host and guest support has been removed 214from Linux upstream kernel, declare it deprecated. 215 216QEMU API (QAPI) events 217---------------------- 218 219``MEM_UNPLUG_ERROR`` (since 6.2) 220'''''''''''''''''''''''''''''''''''''''''''''''''''''''' 221 222Use the more generic event ``DEVICE_UNPLUG_GUEST_ERROR`` instead. 223 224 225System emulator machines 226------------------------ 227 228Arm ``virt`` machine ``dtb-kaslr-seed`` property 229'''''''''''''''''''''''''''''''''''''''''''''''' 230 231The ``dtb-kaslr-seed`` property on the ``virt`` board has been 232deprecated; use the new name ``dtb-randomness`` instead. The new name 233better reflects the way this property affects all random data within 234the device tree blob, not just the ``kaslr-seed`` node. 235 236``pc-i440fx-1.4`` up to ``pc-i440fx-1.7`` (since 7.0) 237''''''''''''''''''''''''''''''''''''''''''''''''''''' 238 239These old machine types are quite neglected nowadays and thus might have 240various pitfalls with regards to live migration. Use a newer machine type 241instead. 242 243 244Backend options 245--------------- 246 247Using non-persistent backing file with pmem=on (since 6.1) 248'''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 249 250This option is used when ``memory-backend-file`` is consumed by emulated NVDIMM 251device. However enabling ``memory-backend-file.pmem`` option, when backing file 252is (a) not DAX capable or (b) not on a filesystem that support direct mapping 253of persistent memory, is not safe and may lead to data loss or corruption in case 254of host crash. 255Options are: 256 257 - modify VM configuration to set ``pmem=off`` to continue using fake NVDIMM 258 (without persistence guaranties) with backing file on non DAX storage 259 - move backing file to NVDIMM storage and keep ``pmem=on`` 260 (to have NVDIMM with persistence guaranties). 261 262Device options 263-------------- 264 265Emulated device options 266''''''''''''''''''''''' 267 268``-device virtio-blk,scsi=on|off`` (since 5.0) 269^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 270 271The virtio-blk SCSI passthrough feature is a legacy VIRTIO feature. VIRTIO 1.0 272and later do not support it because the virtio-scsi device was introduced for 273full SCSI support. Use virtio-scsi instead when SCSI passthrough is required. 274 275Note this also applies to ``-device virtio-blk-pci,scsi=on|off``, which is an 276alias. 277 278``-device sga`` (since 6.2) 279^^^^^^^^^^^^^^^^^^^^^^^^^^^ 280 281The ``sga`` device loads an option ROM for x86 targets which enables 282SeaBIOS to send messages to the serial console. SeaBIOS 1.11.0 onwards 283contains native support for this feature and thus use of the option 284ROM approach is obsolete. The native SeaBIOS support can be activated 285by using ``-machine graphics=off``. 286 287``-device nvme-ns,eui64-default=on|off`` (since 7.1) 288^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 289 290In QEMU versions 6.1, 6.2 and 7.0, the ``nvme-ns`` generates an EUI-64 291identifier that is not globally unique. If an EUI-64 identifier is required, the 292user must set it explicitly using the ``nvme-ns`` device parameter ``eui64``. 293 294``-device nvme,use-intel-id=on|off`` (since 7.1) 295^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 296 297The ``nvme`` device originally used a PCI Vendor/Device Identifier combination 298from Intel that was not properly allocated. Since version 5.2, the controller 299has used a properly allocated identifier. Deprecate the ``use-intel-id`` 300machine compatibility parameter. 301 302 303Block device options 304'''''''''''''''''''' 305 306``"backing": ""`` (since 2.12) 307^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 308 309In order to prevent QEMU from automatically opening an image's backing 310chain, use ``"backing": null`` instead. 311 312``rbd`` keyvalue pair encoded filenames: ``""`` (since 3.1) 313^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 314 315Options for ``rbd`` should be specified according to its runtime options, 316like other block drivers. Legacy parsing of keyvalue pair encoded 317filenames is useful to open images with the old format for backing files; 318These image files should be updated to use the current format. 319 320Example of legacy encoding:: 321 322 json:{"file.driver":"rbd", "file.filename":"rbd:rbd/name"} 323 324The above, converted to the current supported format:: 325 326 json:{"file.driver":"rbd", "file.pool":"rbd", "file.image":"name"} 327 328Backwards compatibility 329----------------------- 330 331Runnability guarantee of CPU models (since 4.1) 332''''''''''''''''''''''''''''''''''''''''''''''' 333 334Previous versions of QEMU never changed existing CPU models in 335ways that introduced additional host software or hardware 336requirements to the VM. This allowed management software to 337safely change the machine type of an existing VM without 338introducing new requirements ("runnability guarantee"). This 339prevented CPU models from being updated to include CPU 340vulnerability mitigations, leaving guests vulnerable in the 341default configuration. 342 343The CPU model runnability guarantee won't apply anymore to 344existing CPU models. Management software that needs runnability 345guarantees must resolve the CPU model aliases using the 346``alias-of`` field returned by the ``query-cpu-definitions`` QMP 347command. 348 349While those guarantees are kept, the return value of 350``query-cpu-definitions`` will have existing CPU model aliases 351point to a version that doesn't break runnability guarantees 352(specifically, version 1 of those CPU models). In future QEMU 353versions, aliases will point to newer CPU model versions 354depending on the machine type, so management software must 355resolve CPU model aliases before starting a virtual machine. 356 357Tools 358----- 359 360virtiofsd 361''''''''' 362 363There is a new Rust implementation of ``virtiofsd`` at 364``https://gitlab.com/virtio-fs/virtiofsd``; 365since this is now marked stable, new development should be done on that 366rather than the existing C version in the QEMU tree. 367The C version will still accept fixes and patches that 368are already in development for the moment, but will eventually 369be deleted from this tree. 370New deployments should use the Rust version, and existing systems 371should consider moving to it. The command line and feature set 372is very close and moving should be simple. 373