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Diffstat (limited to 'docs/about/deprecated.rst')
| -rw-r--r-- | docs/about/deprecated.rst | 340 |
1 files changed, 221 insertions, 119 deletions
diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst index 88f0f03..4203713 100644 --- a/docs/about/deprecated.rst +++ b/docs/about/deprecated.rst @@ -24,12 +24,6 @@ should exclusively use a non-deprecated machine type, with use of the most recent version highly recommended. Non-versioned machine types follow the general feature deprecation policy. -Prior to the 2.10.0 release there was no official policy on how -long features would be deprecated prior to their removal, nor -any documented list of which features were deprecated. Thus -any features deprecated prior to 2.10.0 will be treated as if -they were first deprecated in the 2.10.0 release. - What follows is a list of all features currently marked as deprecated. @@ -74,11 +68,18 @@ configurations (e.g. -smp drawers=1,books=1,clusters=1 for x86 PC machine) is marked deprecated since 9.0, users have to ensure that all the topology members described with -smp are supported by the target machine. -``-runas`` (since 9.1) ----------------------- - -Use ``-run-with user=..`` instead. +``-old-param`` option for booting Arm kernels via param_struct (since 10.0) +''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' +The ``-old-param`` command line option is specific to Arm targets: +it is used when directly booting a guest kernel to pass it the +command line and other information via the old ``param_struct`` ABI, +rather than the newer ATAGS or DTB mechanisms. This option was only +ever needed to support ancient kernels on some old board types +like the ``akita`` or ``terrier``; it has been deprecated in the +kernel since 2001. None of the board types QEMU supports need +``param_struct`` support, so this option has been deprecated and will +be removed in a future QEMU version. User-mode emulator command line arguments ----------------------------------------- @@ -147,32 +148,66 @@ options are removed in favor of using explicit ``blockdev-create`` and ``blockdev-add`` calls. See :doc:`/interop/live-block-operations` for details. -Incorrectly typed ``device_add`` arguments (since 6.2) -'''''''''''''''''''''''''''''''''''''''''''''''''''''' +``query-migrationthreads`` (since 9.2) +'''''''''''''''''''''''''''''''''''''' + +To be removed with no replacement, as it reports only a limited set of +threads (for example, it only reports source side of multifd threads, +without reporting any destination threads, or non-multifd source threads). +For debugging purpose, please use ``-name $VM,debug-threads=on`` instead. + +``block-job-pause`` (since 10.1) +'''''''''''''''''''''''''''''''' + +Use ``job-pause`` instead. The only difference is that ``job-pause`` +always reports GenericError on failure when ``block-job-pause`` reports +DeviceNotActive when block-job is not found. + +``block-job-resume`` (since 10.1) +''''''''''''''''''''''''''''''''' + +Use ``job-resume`` instead. The only difference is that ``job-resume`` +always reports GenericError on failure when ``block-job-resume`` reports +DeviceNotActive when block-job is not found. + +``block-job-complete`` (since 10.1) +''''''''''''''''''''''''''''''''''' -Due to shortcomings in the internal implementation of ``device_add``, QEMU -incorrectly accepts certain invalid arguments: Any object or list arguments are -silently ignored. Other argument types are not checked, but an implicit -conversion happens, so that e.g. string values can be assigned to integer -device properties or vice versa. +Use ``job-complete`` instead. The only difference is that ``job-complete`` +always reports GenericError on failure when ``block-job-complete`` reports +DeviceNotActive when block-job is not found. -This is a bug in QEMU that will be fixed in the future so that previously -accepted incorrect commands will return an error. Users should make sure that -all arguments passed to ``device_add`` are consistent with the documented -property types. +``block-job-dismiss`` (since 10.1) +'''''''''''''''''''''''''''''''''' + +Use ``job-dismiss`` instead. + +``block-job-finalize`` (since 10.1) +''''''''''''''''''''''''''''''''''' + +Use ``job-finalize`` instead. + +``migrate`` argument ``detach`` (since 10.1) +'''''''''''''''''''''''''''''''''''''''''''' + +This argument has always been ignored. Host Architectures ------------------ -BE MIPS (since 7.2) -''''''''''''''''''' +Big endian MIPS since 7.2; 32-bit little endian MIPS since 9.2 +'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' As Debian 10 ("Buster") moved into LTS the big endian 32 bit version of MIPS moved out of support making it hard to maintain our cross-compilation CI tests of the architecture. As we no longer have CI coverage support may bitrot away before the deprecation process -completes. The little endian variants of MIPS (both 32 and 64 bit) are -still a supported host architecture. +completes. + +Likewise, the little endian variant of 32 bit MIPS is not supported by +Debian 13 ("Trixie") and newer. + +64 bit little endian MIPS is still a supported host architecture. System emulation on 32-bit x86 hosts (since 8.0) '''''''''''''''''''''''''''''''''''''''''''''''' @@ -184,6 +219,53 @@ be an effective use of its limited resources, and thus intends to discontinue it. Since all recent x86 hardware from the past >10 years is capable of the 64-bit x86 extensions, a corresponding 64-bit OS should be used instead. +TCG Plugin support not enabled by default on 32-bit hosts (since 9.2) +''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' + +While it is still possible to enable TCG plugin support for 32-bit +hosts there are a number of potential pitfalls when instrumenting +64-bit guests. The plugin APIs typically pass most addresses as +uint64_t but practices like encoding that address in a host pointer +for passing as user-data will lose data. As most software analysis +benefits from having plenty of host memory it seems reasonable to +encourage users to use 64 bit builds of QEMU for analysis work +whatever targets they are instrumenting. + +TCG Plugin support not enabled by default with TCI (since 9.2) +'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' + +While the TCG interpreter can interpret the TCG ops used by plugins it +is going to be so much slower it wouldn't make sense for any serious +instrumentation. Due to implementation differences there will also be +anomalies in things like memory instrumentation. + +32-bit host operating systems (since 10.0) +'''''''''''''''''''''''''''''''''''''''''' + +Keeping 32-bit host support alive is a substantial burden for the +QEMU project. Thus QEMU will in future drop the support for all +32-bit host systems. + +linux-user mode CPUs +-------------------- + +iwMMXt emulation and the ``pxa`` CPUs (since 10.0) +'''''''''''''''''''''''''''''''''''''''''''''''''' + +The ``pxa`` CPU family (``pxa250``, ``pxa255``, ``pxa260``, +``pxa261``, ``pxa262``, ``pxa270-a0``, ``pxa270-a1``, ``pxa270``, +``pxa270-b0``, ``pxa270-b1``, ``pxa270-c0``, ``pxa270-c5``) are no +longer used in system emulation, because all the machine types which +used these CPUs were removed in the QEMU 9.2 release. These CPUs can +now only be used in linux-user mode, and to do that you would have to +explicitly select one of these CPUs with the ``-cpu`` command line +option or the ``QEMU_CPU`` environment variable. + +We don't believe that anybody is using the iwMMXt emulation, and we do +not have any tests to validate it or any real hardware or similar +known-good implementation to test against. GCC is in the process of +dropping their support for iwMMXt codegen. These CPU types are +therefore deprecated in QEMU, and will be removed in a future release. System emulator CPUs -------------------- @@ -206,17 +288,25 @@ in the QEMU object model anymore. ``Sun-UltraSparc-IIIi+`` and but for consistency these will get removed in a future release, too. Use ``Sun-UltraSparc-IIIi-plus`` and ``Sun-UltraSparc-IV-plus`` instead. -CRIS CPU architecture (since 9.0) -''''''''''''''''''''''''''''''''' +PPC 405 CPUs (since 10.0) +''''''''''''''''''''''''' -The CRIS architecture was pulled from Linux in 4.17 and the compiler -is no longer packaged in any distro making it harder to run the -``check-tcg`` tests. Unless we can improve the testing situation there -is a chance the code will bitrot without anyone noticing. +The PPC 405 CPU has no known users and the ``ref405ep`` machine was +removed in QEMU 10.0. Since the IBM POWER [8-11] processors uses an +embedded 405 for power management (OCC) and other internal tasks, it +is theoretically possible to use QEMU to model them. Let's keep the +CPU implementation for a while before removing all support. System emulator machines ------------------------ +Versioned machine types (aarch64, arm, i386, m68k, ppc64, s390x, x86_64) +'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' + +In accordance with our versioned machine type deprecation policy, all machine +types with version |VER_MACHINE_DEPRECATION_VERSION|, or older, have been +deprecated. + Arm ``virt`` machine ``dtb-kaslr-seed`` property (since 7.1) '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' @@ -225,57 +315,48 @@ deprecated; use the new name ``dtb-randomness`` instead. The new name better reflects the way this property affects all random data within the device tree blob, not just the ``kaslr-seed`` node. -``pc-i440fx-2.4`` up to ``pc-i440fx-2.12`` (since 9.1) -'''''''''''''''''''''''''''''''''''''''''''''''''''''' +Mips ``mipssim`` machine (since 10.0) +''''''''''''''''''''''''''''''''''''' -These old machine types are quite neglected nowadays and thus might have -various pitfalls with regards to live migration. Use a newer machine type +Linux dropped support for this virtual machine type in kernel v3.7, and +there does not seem to be anybody around who is still using this board +in QEMU: Most former MIPS-related people are working on other architectures +in their everyday job nowadays, and we are also not aware of anybody still +using old binaries with this board (i.e. there is also no binary available +online to check that this board did not completely bitrot yet). It is +recommended to use another MIPS machine for future MIPS code development instead. -``shix`` (since 9.0) -'''''''''''''''''''' +RISC-V default machine option (since 10.0) +'''''''''''''''''''''''''''''''''''''''''' -The machine is no longer in existence and has been long unmaintained -in QEMU. This also holds for the TC51828 16MiB flash that it uses. +RISC-V defines ``spike`` as the default machine if no machine option is +given in the command line. This happens because ``spike`` is the first +RISC-V machine implemented in QEMU and setting it as default was +convenient at that time. Now we have 7 riscv64 and 6 riscv32 machines +and having ``spike`` as a default is no longer justified. This default +will also promote situations where users think they're running ``virt`` +(the most used RISC-V machine type in 10.0) when in fact they're +running ``spike``. -``pseries-2.1`` up to ``pseries-2.12`` (since 9.0) -'''''''''''''''''''''''''''''''''''''''''''''''''' +Removing the default machine option forces users to always set the machine +they want to use and avoids confusion. Existing users of the ``spike`` +machine must ensure that they're setting the ``spike`` machine in the +command line (``-M spike``). + + +System emulator binaries +------------------------ + +``qemu-system-microblazeel`` (since 10.1) +''''''''''''''''''''''''''''''''''''''''' + +The ``qemu-system-microblaze`` binary can emulate little-endian machines +now, too, so the separate binary ``qemu-system-microblazeel`` (with the +``el`` suffix) for little-endian targets is not required anymore. The +``petalogix-s3adsp1800`` machine can now be switched to little endian by +setting its ``endianness`` property to ``little``. -Older pseries machines before version 3.0 have undergone many changes -to correct issues, mostly regarding migration compatibility. These are -no longer maintained and removing them will make the code easier to -read and maintain. Use versions 3.0 and above as a replacement. - -Arm machines ``akita``, ``borzoi``, ``cheetah``, ``connex``, ``mainstone``, ``n800``, ``n810``, ``spitz``, ``terrier``, ``tosa``, ``verdex``, ``z2`` (since 9.0) -'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' - -QEMU includes models of some machine types where the QEMU code that -emulates their SoCs is very old and unmaintained. This code is now -blocking our ability to move forward with various changes across -the codebase, and over many years nobody has been interested in -trying to modernise it. We don't expect any of these machines to have -a large number of users, because they're all modelling hardware that -has now passed away into history. We are therefore dropping support -for all machine types using the PXA2xx and OMAP2 SoCs. We are also -dropping the ``cheetah`` OMAP1 board, because we don't have any -test images for it and don't know of anybody who does; the ``sx1`` -and ``sx1-v1`` OMAP1 machines remain supported for now. - -PPC 405 ``ref405ep`` machine (since 9.1) -'''''''''''''''''''''''''''''''''''''''' - -The ``ref405ep`` machine and PPC 405 CPU have no known users, firmware -images are not available, OpenWRT dropped support in 2019, U-Boot in -2017, Linux also is dropping support in 2024. It is time to let go of -this ancient hardware and focus on newer CPUs and platforms. - -Arm ``tacoma-bmc`` machine (since 9.1) -'''''''''''''''''''''''''''''''''''''''' - -The ``tacoma-bmc`` machine was a board including an AST2600 SoC based -BMC and a witherspoon like OpenPOWER system. It was used for bring up -of the AST2600 SoC in labs. It can be easily replaced by the -``rainier-bmc`` machine which is a real product. Backend options --------------- @@ -324,41 +405,6 @@ the addition of volatile memory support, it is now necessary to distinguish between persistent and volatile memory backends. As such, memdev is deprecated in favor of persistent-memdev. -``-fsdev proxy`` and ``-virtfs proxy`` (since 8.1) -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ - -The 9p ``proxy`` filesystem backend driver has been deprecated and will be -removed (along with its proxy helper daemon) in a future version of QEMU. Please -use ``-fsdev local`` or ``-virtfs local`` for using the 9p ``local`` filesystem -backend, or alternatively consider deploying virtiofsd instead. - -The 9p ``proxy`` backend was originally developed as an alternative to the 9p -``local`` backend. The idea was to enhance security by dispatching actual low -level filesystem operations from 9p server (QEMU process) over to a separate -process (the virtfs-proxy-helper binary). However this alternative never gained -momentum. The proxy backend is much slower than the local backend, hasn't seen -any development in years, and showed to be less secure, especially due to the -fact that its helper daemon must be run as root, whereas with the local backend -QEMU is typically run as unprivileged user and allows to tighten behaviour by -mapping permissions et al by using its 'mapped' security model option. - -Nowadays it would make sense to reimplement the ``proxy`` backend by using -QEMU's ``vhost`` feature, which would eliminate the high latency costs under -which the 9p ``proxy`` backend currently suffers. However as of to date nobody -has indicated plans for such kind of reimplementation unfortunately. - -RISC-V 'any' CPU type ``-cpu any`` (since 8.2) -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ - -The 'any' CPU type was introduced back in 2018 and has been around since the -initial RISC-V QEMU port. Its usage has always been unclear: users don't know -what to expect from a CPU called 'any', and in fact the CPU does not do anything -special that isn't already done by the default CPUs rv32/rv64. - -After the introduction of the 'max' CPU type, RISC-V now has a good coverage -of generic CPUs: rv32 and rv64 as default CPUs and 'max' as a feature complete -CPU for both 32 and 64 bit builds. Users are then discouraged to use the 'any' -CPU type starting in 8.2. RISC-V CPU properties which start with capital 'Z' (since 8.2) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -422,6 +468,15 @@ Specifying the iSCSI password in plain text on the command line using the used instead, to refer to a ``--object secret...`` instance that provides a password via a file, or encrypted. +``gluster`` backend (since 9.2) +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +According to https://marc.info/?l=fedora-devel-list&m=171934833215726 +the GlusterFS development effectively ended. Unless the development +gains momentum again, the QEMU project will remove the gluster backend +in a future release. + + Character device options '''''''''''''''''''''''' @@ -430,16 +485,49 @@ Backend ``memory`` (since 9.0) ``memory`` is a deprecated synonym for ``ringbuf``. -CPU device properties -''''''''''''''''''''' +``reconnect`` (since 9.2) +^^^^^^^^^^^^^^^^^^^^^^^^^ -``pcommit`` on x86 (since 9.1) -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +The ``reconnect`` option only allows specifying second granularity timeouts, +which is not enough for all types of use cases, use ``reconnect-ms`` instead. -The PCOMMIT instruction was never included in any physical processor. -It was implemented as a no-op instruction in TCG up to QEMU 9.0, but -only with ``-cpu max`` (which does not guarantee migration compatibility -across versions). + +Net device options +'''''''''''''''''' + +Stream ``reconnect`` (since 9.2) +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The ``reconnect`` option only allows specifying second granularity timeouts, +which is not enough for all types of use cases, use ``reconnect-ms`` instead. + +VFIO device options +''''''''''''''''''' + +``-device vfio-calxeda-xgmac`` (since 10.0) +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +The vfio-calxeda-xgmac device allows to assign a host Calxeda Highbank +10Gb XGMAC Ethernet controller device ("calxeda,hb-xgmac" compatibility +string) to a guest. Calxeda HW has been ewasted now and there is no point +keeping that device. + +``-device vfio-amd-xgbe`` (since 10.0) +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +The vfio-amd-xgbe device allows to assign a host AMD 10GbE controller +to a guest ("amd,xgbe-seattle-v1a" compatibility string). AMD "Seattle" +is not supported anymore and there is no point keeping that device. + +``-device vfio-platform`` (since 10.0) +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +The vfio-platform device allows to assign a host platform device +to a guest in a generic manner. Integrating a new device into +the vfio-platform infrastructure requires some adaptation at +both kernel and qemu level. No such attempt has been done for years +and the conclusion is that vfio-platform has not got any traction. +PCIe passthrough shall be the mainline solution. + +CPU device properties +''''''''''''''''''''' ``pmu-num=n`` on RISC-V CPUs (since 8.2) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -450,6 +538,14 @@ be calculated with ``((2 ^ n) - 1) << 3``. The least significant three bits must be left clear. +``pcommit`` on x86 (since 9.1) +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The PCOMMIT instruction was never included in any physical processor. +It was implemented as a no-op instruction in TCG up to QEMU 9.0, but +only with ``-cpu max`` (which does not guarantee migration compatibility +across versions). + Backwards compatibility ----------------------- @@ -503,3 +599,9 @@ usage of providing a file descriptor to a plain file has been deprecated in favor of explicitly using the ``file:`` URI with the file descriptor being passed as an ``fdset``. Refer to the ``add-fd`` command documentation for details on the ``fdset`` usage. + +``zero-blocks`` capability (since 9.2) +'''''''''''''''''''''''''''''''''''''' + +The ``zero-blocks`` capability was part of the block migration which +doesn't exist anymore since it was removed in QEMU v9.1. |