ChangeLog/9.0: Difference between revisions

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(Created page with "== System emulation == === Removed features and incompatible changes === Consult the [https://qemu-project.gitlab.io/qemu/about/removed-features.html 'Removed features'] page for details of suggested replacement functionality. * Running QEMU with KVM requires Linux 4.4 or newer. A future version of QEMU will increase the minimum requirement for Arm hosts to Linux 4.19 (also when running KVM); if this is too restrictive for your use case, please contact us at qemu-deve...")
 
(added note about SBSA-ref 1GHz timer frequency)
 
(64 intermediate revisions by 16 users not shown)
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Release schedule: [[Planning/9.0]].
== System emulation ==
== System emulation ==


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* Running QEMU with KVM requires Linux 4.4 or newer. A future version of QEMU will increase the minimum requirement for Arm hosts to Linux 4.19 (also when running KVM); if this is too restrictive for your use case, please contact us at qemu-devel@nongnu.org.
* Running QEMU with KVM requires Linux 4.4 or newer. A future version of QEMU will increase the minimum requirement for Arm hosts to Linux 4.19 (also when running KVM); if this is too restrictive for your use case, please contact us at qemu-devel@nongnu.org.
* The behaviour of the '-serial none' option when used together with other '-serial' options has been corrected. Previously when '-serial none' was followed by '-serial something' the '-serial none' was effectively ignored. Now it controls the existence of the first serial port, and the following '-serial' option controls the behaviour of the second serial port; this brings it in to line with how all other cases of multiple '-serial' options work. If you have a command line that was accidentally relying on the old behaviour, you can simply delete the unnecessary '-serial none'.


=== New deprecated options and features ===
=== New deprecated options and features ===


Consult the [https://qemu-project.gitlab.io/qemu/about/deprecated.html "Deprecated Features"] chapter of the QEMU System Emulation User's Guide for further details of the deprecations and their suggested replacements.
Consult the [https://qemu-project.gitlab.io/qemu/about/deprecated.html "Deprecated Features"] chapter of the QEMU System Emulation User's Guide for further details of the deprecations and their suggested replacements.
* The CRIS architecture has been marked deprecated
* Arm boards akita, borzoi, cheetah, connex, mainstone, n800, n810, spitz, terrier, tosa, verdex, z2 have been deprecated


=== 68k ===
=== 68k ===
* Fixed exception frame format for 68010
* Add nubus-virtio-mmio device to allow the q800 machine to access virtio devices


=== Alpha ===
=== Alpha ===


=== Arm ===
=== Arm ===
* Some board types modelling old Arm hardware using the PXA2xx and OMAP2 SoCs have been deprecated and are scheduled for removal in a future QEMU release: akita, borzoi, cheetah, connex, mainstone, n800, n810, spitz, terrier, tosa, verdex, z2. The code implementing these boards was very old and unmaintained, and we don't believe that any of them have a large number of users.
* New architectural features now emulated:
** FEAT_ECV (Enhanced Counter Virtualization)
** FEAT_NV (Nested Virtualization)
** FEAT_NV2 (Enhanced nested virtualization support)
* New board types:
** b-l475e-iot01a : the B-L475E-IOT01A board (currently minimal support only)
** mps3-an536 : a Cortex-R52 board modelling the AN536 firmware image for the MPS3 development board
** raspi4b : the Raspberry Pi 4 Model B. Note that QEMU does not yet model PCI or ethernet; we hope to implement those devices for the next QEMU release.
* Changes to existing board types:
** The Freescale i.MX6 now models the cache controller and the PCIe controller
** The Allwinner R40 and Bananapi boards now model the USB controllers, the AHCI/SATA controller and the watchdog timer
** Raspberry Pi boards now support the SPI controller and the BSC i2c controller
** The npcm7xx based boards now support the ethernet controllers
** SBSA Reference Platform uses 1GHz timer frequency. If you see time going too fast then update firmware.
** The virt board now wires up non-secure EL2 virtual timer IRQ when EL2 emulation is enabled with 'virtualization=on'.
Note that when the virt board uses the non-secure EL2 virtual timer IRQ, this will trip a bug in older versions of the EDK2 guest firmware, which causes EDK2 to assert on bootup with "ASSERT [ArmTimerDxe] /home/kraxel/projects/qemu/roms/edk2/ArmVirtPkg/Library/ArmVirtTimerFdtClientLib/ArmVirtTimerFdtClientLib.c(72): PropSize == 36 || PropSize == 48". If you see that assertion you should do one of:
* update your EDK2 binaries to edk2-stable202311 or newer
* use the 'virt-8.2' versioned machine type
* not use 'virtualization=on'


=== AVR ===
=== AVR ===
Line 22: Line 57:


=== HPPA ===
=== HPPA ===
* SeaBIOS-hppa version 16
* SeaBIOS now provided as 64-bit and 32-bit binary
* Fixed 32-bit HP-UX crashes on B160L (32-bit) machine
* Fixed random SCSI slowdowns and script aborts on HP-UX 10.20, Linux and NetBSD
* Fixed NetBSD boot failure due to power button in page zero
* Fixed NetBSD FPU detection failure
* Fixed NetBSD networking with tulip driver
* Fixed OpenBSD 7.4 boot failure
* Allows up to 3840 MB of memory (instead of 3.0 GB)
* Supports the qemu ''--nodefaults'' option
* Added qemu-specific opcodes for "HALT QEMU", "RESET QEMU" and "RESTORE SHR" (restore shadow registers).
* Does not abort on access failure in Astro/Elroy registers


=== LoongArch ===
=== LoongArch ===


==== ISA and Extensions ====
==== ISA and Extensions ====
* Add loongarch kvm accel support
* KVM: Enable LSX/LASX extension
* Fix tlb huge page loading issue
* Set vector registers call clobbered
* Set cpuid CSR register only once with kvm mode


==== Machines ====
==== Machines ====
* Change the UEFI loading mode to loongarch
* Add dynamic cpu number support for loongarch_extioi
* Fix qtest test-hmp error when KVM-only build
* Fix qemu-system-loongarch64 assert failed with the option '-d int'
* Fix interrupt routing update


=== Microblaze ===
=== Microblaze ===
Line 34: Line 91:


=== Nios2 ===
=== Nios2 ===
* A bug was fixed in nios2-linux-user that meant async work was being skipped


=== OpenRISC ===
=== OpenRISC ===
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=== Renesas SH ===
=== Renesas SH ===
==== ISA and Extensions ====
* Fix mac.w memory load operand size
* Fix mac.w behavior in saturation arithmetic mode
* Fix mac.l behavior in saturation arithmetic mode
* Fix delay slot restrictions for PC-relative mov.w, mov.l, mova


=== RISC-V ===
=== RISC-V ===


==== ISA and Extensions ====
==== ISA and Extensions ====
* Add support for Zacas extension
* Add amocas.[w,d,q] instructions
* RVA22 profiles support
* Add RVV CSRs to KVM
* Add support for 'B' extension
* Implement optional CSR mcontext of debug Sdtrig extension
* Add support for Zaamo and Zalrsc
* Enable xtheadsync under user mode
* Add Ztso extension
* Use 'zfa' instead of 'Zfa'
* move ratified/frozen exts to non-experimental


==== Machines ====
==== Machines ====
* ACPI: Enable AIA, PLIC and update RHCT
* Fix the interrupts-extended property format of PLIC
* Document acpi parameter of virt machine
* Remove group setting of KVM AIA if the machine only has 1 socket
* sifive_u: Update S-mode U-Boot image build instructions
* Support vlenb and vregs[] in KVM
* Support new isa extension detection devicetree properties
* SMBIOS support for RISC-V virt machine
* Add rv32i,rv32e and rv64e CPUs
* Enable SPCR for SCPI virt machine
* Add SRAT and SLIT ACPI tables
* Update KVM exts to Linux 6.8


==== Fixes and Misc ====
==== Fixes and Misc ====
* Fix th.dcache.cval1 priviledge check
* Don't allow write mstatus_vs without RVV
* Fix machine IDs QOM getters
* Fix KVM reg id sizes
* Upgrade OpenSBI from v1.3.1 to v1.4
* pmp: Ignore writes when RW=01 and MML=0
* Don't adjust vscause for exceptions
* Ensure mideleg is set correctly on reset
* Check for 'A' extension on all atomic instructions
* Allow large kernels to boot by moving the initrd further away in RAM
* FIX xATP_MODE validation
* Ensure mcountinhibit, mcounteren, scounteren, hcounteren are 32-bit
* Fix vector shift count overflow
* Fix setipnum_le write emulation for APLIC MSI-mode
* Fix in_clrip[x] read emulation
* Fix privilege mode of G-stage translation for debugging
* Fix ACPI MCFG table for virt machine
* A range of Vector fixes
* Update APLIC IDC after claiming iforce register
* Fix timebase-frequency when using KVM acceleration


=== s390x ===
=== s390x ===
* Fix access register handling in the emulation of the LOAD ADDRESS EXTENDED (LAE) instruction
* Add emulation of CVDG, CVB, CVBY and CVBG instructions


=== SPARC ===
=== SPARC ===
* Fix ASI_USERTXT access which caused the Solaris kernel to panic when using mdb/gdb/adb within the guest


=== Tricore ===
=== Tricore ===
Line 74: Line 187:


==== Block devices ====
==== Block devices ====
* The 'virtio-blk' device has gained true multiqueue support where different queues of a single disk can be processed by different I/O threads. This can improve scalability in cases where the guest submitted enough I/O to saturate the host CPU running a single I/O thread processing the virtio-blk requests. Multiple I/O threads can be configured using the new 'iothread-vq-mapping' property.
* 'usb-storage' doesn't ignore the properties 'backend_defaults', 'logical_block_size', 'physical_block_size', 'min_io_size', 'opt_io_size' and 'discard_granularity' any more.
* Fixed 'vhost-vdpa-device' to be compatible with VDUSE block exports again (this was broken in QEMU 8.2.0)


==== Graphics ====
==== Graphics ====
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==== SCSI ====
==== SCSI ====
* The ESP SCSI (am53c974/dc390) device has been substantially rewritten, fixing several long-standing bugs and making it easier to maintain in future.


==== SD card ====
==== SD card ====
Line 108: Line 227:


==== VFIO ====
==== VFIO ====
* Introduced an IOMMU interface backend for VFIO devices
* Introduced a new IOMMUFD backend for ARM, x86_64 and s390x platforms
* Better error reporting
* Allowed cpr-reboot for VFIO devices
* Misc fixes


==== virtio ====
==== virtio ====
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=== Character devices ===
=== Character devices ===
* Fix potential crash if connection is dropped while the TLS handshake is still in progress
* Fix I/O on TLS channels when chardev frontend is not ready to consume data
* QEMU is more likely to process pending incoming data before processing EOF/HUP


=== Crypto subsystem ===
=== Crypto subsystem ===
* The 'sm4' cipher algorithm is now supported and can be used with the 'luks' block driver
* The cipher test suite will automatically skip testing algorithms that have been disabled in the underlying OS crypto library at build time.


=== Authorization subsystem ===
=== Authorization subsystem ===
Line 134: Line 265:


=== GDBStub ===
=== GDBStub ===
* the gdbstub now supports catching syscalls in user-mode
* the gdbstub now supports fork-follow modes
* the gsbstub now supports siginfo:read


=== TCG Plugins ===
=== TCG Plugins ===
* vcpu_init callback will now always be in the vcpu context
* A new API for accessing register values is now available (and used by execlog)
* The inline API has been replaced with a thread safe scoreboard indexed by vcpu_index


=== Host support ===
=== Host support ===


=== Memory backends ===
=== Memory backends ===
* Memory backends specified on the QEMU commandline can now be preallocated concurrently/asynchronously in some configurations, to speedup QEMU startup with preallocation on multiple memory backends: one requirement is that memory backends that are getting preallocated have a "thread-context" set.
* QEMU 8.2 accidentally allowed for creation of memory backends with sizes that are not aligned to the (huge) page size. This has been fixed.


=== Migration ===
=== Migration ===
* Fixed migration for SUSPENDED VM, where we used to ignore the SUSPENDED state and kick off the VM even if it was suspended before the migration.
* New capability called "mapped-ram". It allows efficient VM snapshots save/load by providing both (1) constant size of ultimate VM image rather than unlimited, and (2) multi-threading support so that save/load of snapshots can be faster.
* Zero page detection offloading for multifd, so that idle guest migration should get a major boost when multifd is enabled.
* New parameter called "zero-page-detection", allow the user to choose the policy for detecting zero pages.
* Enhancement to CPR-reboot mode, added VFIO supports (requires guest suspensions), new documents.
* Fixed a rare postcopy hang with preempt mode since 8.2


=== Monitor ===
=== Monitor ===


==== QMP ====
==== QMP ====
* Fixed a race condition where monitor commands could be executed unexpectedly in the middle of another operation and caused crashes


==== HMP ====
==== HMP ====
Line 152: Line 301:


=== Block device backends and tools ===
=== Block device backends and tools ===
* The block layer is now thread safe and multiple I/O threads can send I/O requests to the same disk image. virtio-blk can be configured to make use of this and improve scalability (see above).
* The 'luks' block driver now supports creation and usage of detached LUKS header files
* The 'stream' and 'commit' block jobs have a new flag 'backing-mask-protocol'. If it is enabled and the base backing file uses a protocol driver (like 'file') directly, 'raw' is stored as the backing file format in the overlay instead of the protocol name.
* In 'blklogwrites', potential log corruption bugs were fixed related to concurrent requests and to write zeroes operations
* Fixed I/O errors in the libblkio based block drivers caused by incorrect memory alignment of bounce buffers
* Fixed deadlocks that could hang the whole QEMU process in the mirror block job and the NBD export


=== Tracing ===
=== Tracing ===
Line 158: Line 314:


=== Miscellaneous ===
=== Miscellaneous ===
* During startup QEMU system emulators will raise the max file descriptors soft limit to match the hard limit
* Seccomp filters will now return EPERM rather than killing QEMU if code attempts to spawn a child process. Fixes compatibility with some NVIDIA libraries which try to run modprobe.
* Thread-local coroutine pools have been mostly replaced by a global pool, which reduces the number of inactive coroutines (and therefore memory mappings) and is limited to a maximum size depending on ''vm.max_map_count'' on Linux. This fixes the "failed to set up stack guard page" error that has been reported on Linux hosts where the QEMU coroutine pool exceeded the ''vm.max_map_count'' limit.


== User-mode emulation ==
== User-mode emulation ==
Line 177: Line 337:
=== x86 ===
=== x86 ===


== TCG backends ==
== TCG ==
 
=== Record/Replay===
 
* fixed record/replay to avoid problems with partial chardev drains
* updated replay-dump.py for current ABI


=== RISC-V ===
=== RISC-V ===


== Guest agent ==
== Guest agent ==
* Fix build on Solaris
* Improve help for --allow-rpcs and --block-rpcs command line options
* Fix guest-get-fsinfo when a volume has more than one disk (Windows only)
* Add support of Windows Server 2025 in guest-get-osinfo command (Windows only)


== Build Information ==
== Build Information ==
Line 187: Line 357:
=== Build Dependencies ===
=== Build Dependencies ===


=== Docker Tweaks ===
=== Build hardening ===
 
* QEMU build will include '-fzero-call-used-regs' to attempt to reduce exploitable ROP gadgets
* QEMU build will include '-ftrivial-auto-var-init=zero' to reduce the chance of uninitialized stack variables causing security issues


=== Windows ===
=== Windows ===
* 32-bit Windows is no longer supported as a host OS; use a 64-bit Windows host instead.


=== Testing and CI ===
=== Testing and CI ===
* The timeout for TCG tests was raised to 120s (for the benefit of TCI)
* The OpenBSD VM was updated to 7.4


== Known issues ==
== Known issues ==


* See https://gitlab.com/qemu-project/qemu/-/milestones/11
* See https://gitlab.com/qemu-project/qemu/-/milestones/11

Latest revision as of 06:46, 10 June 2024

Release schedule: Planning/9.0.

System emulation

Removed features and incompatible changes

Consult the 'Removed features' page for details of suggested replacement functionality.

  • Running QEMU with KVM requires Linux 4.4 or newer. A future version of QEMU will increase the minimum requirement for Arm hosts to Linux 4.19 (also when running KVM); if this is too restrictive for your use case, please contact us at qemu-devel@nongnu.org.
  • The behaviour of the '-serial none' option when used together with other '-serial' options has been corrected. Previously when '-serial none' was followed by '-serial something' the '-serial none' was effectively ignored. Now it controls the existence of the first serial port, and the following '-serial' option controls the behaviour of the second serial port; this brings it in to line with how all other cases of multiple '-serial' options work. If you have a command line that was accidentally relying on the old behaviour, you can simply delete the unnecessary '-serial none'.

New deprecated options and features

Consult the "Deprecated Features" chapter of the QEMU System Emulation User's Guide for further details of the deprecations and their suggested replacements.

  • The CRIS architecture has been marked deprecated
  • Arm boards akita, borzoi, cheetah, connex, mainstone, n800, n810, spitz, terrier, tosa, verdex, z2 have been deprecated

68k

  • Fixed exception frame format for 68010
  • Add nubus-virtio-mmio device to allow the q800 machine to access virtio devices

Alpha

Arm

  • Some board types modelling old Arm hardware using the PXA2xx and OMAP2 SoCs have been deprecated and are scheduled for removal in a future QEMU release: akita, borzoi, cheetah, connex, mainstone, n800, n810, spitz, terrier, tosa, verdex, z2. The code implementing these boards was very old and unmaintained, and we don't believe that any of them have a large number of users.
  • New architectural features now emulated:
    • FEAT_ECV (Enhanced Counter Virtualization)
    • FEAT_NV (Nested Virtualization)
    • FEAT_NV2 (Enhanced nested virtualization support)
  • New board types:
    • b-l475e-iot01a : the B-L475E-IOT01A board (currently minimal support only)
    • mps3-an536 : a Cortex-R52 board modelling the AN536 firmware image for the MPS3 development board
    • raspi4b : the Raspberry Pi 4 Model B. Note that QEMU does not yet model PCI or ethernet; we hope to implement those devices for the next QEMU release.
  • Changes to existing board types:
    • The Freescale i.MX6 now models the cache controller and the PCIe controller
    • The Allwinner R40 and Bananapi boards now model the USB controllers, the AHCI/SATA controller and the watchdog timer
    • Raspberry Pi boards now support the SPI controller and the BSC i2c controller
    • The npcm7xx based boards now support the ethernet controllers
    • SBSA Reference Platform uses 1GHz timer frequency. If you see time going too fast then update firmware.
    • The virt board now wires up non-secure EL2 virtual timer IRQ when EL2 emulation is enabled with 'virtualization=on'.

Note that when the virt board uses the non-secure EL2 virtual timer IRQ, this will trip a bug in older versions of the EDK2 guest firmware, which causes EDK2 to assert on bootup with "ASSERT [ArmTimerDxe] /home/kraxel/projects/qemu/roms/edk2/ArmVirtPkg/Library/ArmVirtTimerFdtClientLib/ArmVirtTimerFdtClientLib.c(72): PropSize == 36 || PropSize == 48". If you see that assertion you should do one of:

  • update your EDK2 binaries to edk2-stable202311 or newer
  • use the 'virt-8.2' versioned machine type
  • not use 'virtualization=on'

AVR

Hexagon

HPPA

  • SeaBIOS-hppa version 16
  • SeaBIOS now provided as 64-bit and 32-bit binary
  • Fixed 32-bit HP-UX crashes on B160L (32-bit) machine
  • Fixed random SCSI slowdowns and script aborts on HP-UX 10.20, Linux and NetBSD
  • Fixed NetBSD boot failure due to power button in page zero
  • Fixed NetBSD FPU detection failure
  • Fixed NetBSD networking with tulip driver
  • Fixed OpenBSD 7.4 boot failure
  • Allows up to 3840 MB of memory (instead of 3.0 GB)
  • Supports the qemu --nodefaults option
  • Added qemu-specific opcodes for "HALT QEMU", "RESET QEMU" and "RESTORE SHR" (restore shadow registers).
  • Does not abort on access failure in Astro/Elroy registers

LoongArch

ISA and Extensions

  • Add loongarch kvm accel support
  • KVM: Enable LSX/LASX extension
  • Fix tlb huge page loading issue
  • Set vector registers call clobbered
  • Set cpuid CSR register only once with kvm mode

Machines

  • Change the UEFI loading mode to loongarch
  • Add dynamic cpu number support for loongarch_extioi
  • Fix qtest test-hmp error when KVM-only build
  • Fix qemu-system-loongarch64 assert failed with the option '-d int'
  • Fix interrupt routing update

Microblaze

MIPS

Nios2

  • A bug was fixed in nios2-linux-user that meant async work was being skipped

OpenRISC

PowerPC

Renesas RX

Renesas SH

ISA and Extensions

  • Fix mac.w memory load operand size
  • Fix mac.w behavior in saturation arithmetic mode
  • Fix mac.l behavior in saturation arithmetic mode
  • Fix delay slot restrictions for PC-relative mov.w, mov.l, mova

RISC-V

ISA and Extensions

  • Add support for Zacas extension
  • Add amocas.[w,d,q] instructions
  • RVA22 profiles support
  • Add RVV CSRs to KVM
  • Add support for 'B' extension
  • Implement optional CSR mcontext of debug Sdtrig extension
  • Add support for Zaamo and Zalrsc
  • Enable xtheadsync under user mode
  • Add Ztso extension
  • Use 'zfa' instead of 'Zfa'
  • move ratified/frozen exts to non-experimental

Machines

  • ACPI: Enable AIA, PLIC and update RHCT
  • Fix the interrupts-extended property format of PLIC
  • Document acpi parameter of virt machine
  • Remove group setting of KVM AIA if the machine only has 1 socket
  • sifive_u: Update S-mode U-Boot image build instructions
  • Support vlenb and vregs[] in KVM
  • Support new isa extension detection devicetree properties
  • SMBIOS support for RISC-V virt machine
  • Add rv32i,rv32e and rv64e CPUs
  • Enable SPCR for SCPI virt machine
  • Add SRAT and SLIT ACPI tables
  • Update KVM exts to Linux 6.8

Fixes and Misc

  • Fix th.dcache.cval1 priviledge check
  • Don't allow write mstatus_vs without RVV
  • Fix machine IDs QOM getters
  • Fix KVM reg id sizes
  • Upgrade OpenSBI from v1.3.1 to v1.4
  • pmp: Ignore writes when RW=01 and MML=0
  • Don't adjust vscause for exceptions
  • Ensure mideleg is set correctly on reset
  • Check for 'A' extension on all atomic instructions
  • Allow large kernels to boot by moving the initrd further away in RAM
  • FIX xATP_MODE validation
  • Ensure mcountinhibit, mcounteren, scounteren, hcounteren are 32-bit
  • Fix vector shift count overflow
  • Fix setipnum_le write emulation for APLIC MSI-mode
  • Fix in_clrip[x] read emulation
  • Fix privilege mode of G-stage translation for debugging
  • Fix ACPI MCFG table for virt machine
  • A range of Vector fixes
  • Update APLIC IDC after claiming iforce register
  • Fix timebase-frequency when using KVM acceleration

s390x

  • Fix access register handling in the emulation of the LOAD ADDRESS EXTENDED (LAE) instruction
  • Add emulation of CVDG, CVB, CVBY and CVBG instructions

SPARC

  • Fix ASI_USERTXT access which caused the Solaris kernel to panic when using mdb/gdb/adb within the guest

Tricore

x86

Xen emulation under KVM

TCG

Known issues

Xtensa

Device emulation and assignment

ACPI / SMBIOS

Audio

Block devices

  • The 'virtio-blk' device has gained true multiqueue support where different queues of a single disk can be processed by different I/O threads. This can improve scalability in cases where the guest submitted enough I/O to saturate the host CPU running a single I/O thread processing the virtio-blk requests. Multiple I/O threads can be configured using the new 'iothread-vq-mapping' property.
  • 'usb-storage' doesn't ignore the properties 'backend_defaults', 'logical_block_size', 'physical_block_size', 'min_io_size', 'opt_io_size' and 'discard_granularity' any more.
  • Fixed 'vhost-vdpa-device' to be compatible with VDUSE block exports again (this was broken in QEMU 8.2.0)

Graphics

Hyper-V

I2C

Input devices

IPMI

Multi-process QEMU

Network devices

NVDIMM

NVMe

PCI/PCIe

SCSI

  • The ESP SCSI (am53c974/dc390) device has been substantially rewritten, fixing several long-standing bugs and making it easier to maintain in future.

SD card

SMBIOS

TPM

UFS

USB

VFIO

  • Introduced an IOMMU interface backend for VFIO devices
  • Introduced a new IOMMUFD backend for ARM, x86_64 and s390x platforms
  • Better error reporting
  • Allowed cpr-reboot for VFIO devices
  • Misc fixes

virtio

vDPA

Xen

fw_cfg

9pfs

virtiofs

Semihosting

Audio

Character devices

  • Fix potential crash if connection is dropped while the TLS handshake is still in progress
  • Fix I/O on TLS channels when chardev frontend is not ready to consume data
  • QEMU is more likely to process pending incoming data before processing EOF/HUP

Crypto subsystem

  • The 'sm4' cipher algorithm is now supported and can be used with the 'luks' block driver
  • The cipher test suite will automatically skip testing algorithms that have been disabled in the underlying OS crypto library at build time.

Authorization subsystem

GUI

GDBStub

  • the gdbstub now supports catching syscalls in user-mode
  • the gdbstub now supports fork-follow modes
  • the gsbstub now supports siginfo:read

TCG Plugins

  • vcpu_init callback will now always be in the vcpu context
  • A new API for accessing register values is now available (and used by execlog)
  • The inline API has been replaced with a thread safe scoreboard indexed by vcpu_index

Host support

Memory backends

  • Memory backends specified on the QEMU commandline can now be preallocated concurrently/asynchronously in some configurations, to speedup QEMU startup with preallocation on multiple memory backends: one requirement is that memory backends that are getting preallocated have a "thread-context" set.
  • QEMU 8.2 accidentally allowed for creation of memory backends with sizes that are not aligned to the (huge) page size. This has been fixed.

Migration

  • Fixed migration for SUSPENDED VM, where we used to ignore the SUSPENDED state and kick off the VM even if it was suspended before the migration.
  • New capability called "mapped-ram". It allows efficient VM snapshots save/load by providing both (1) constant size of ultimate VM image rather than unlimited, and (2) multi-threading support so that save/load of snapshots can be faster.
  • Zero page detection offloading for multifd, so that idle guest migration should get a major boost when multifd is enabled.
  • New parameter called "zero-page-detection", allow the user to choose the policy for detecting zero pages.
  • Enhancement to CPR-reboot mode, added VFIO supports (requires guest suspensions), new documents.
  • Fixed a rare postcopy hang with preempt mode since 8.2

Monitor

QMP

  • Fixed a race condition where monitor commands could be executed unexpectedly in the middle of another operation and caused crashes

HMP

Network

Block device backends and tools

  • The block layer is now thread safe and multiple I/O threads can send I/O requests to the same disk image. virtio-blk can be configured to make use of this and improve scalability (see above).
  • The 'luks' block driver now supports creation and usage of detached LUKS header files
  • The 'stream' and 'commit' block jobs have a new flag 'backing-mask-protocol'. If it is enabled and the base backing file uses a protocol driver (like 'file') directly, 'raw' is stored as the backing file format in the overlay instead of the protocol name.
  • In 'blklogwrites', potential log corruption bugs were fixed related to concurrent requests and to write zeroes operations
  • Fixed I/O errors in the libblkio based block drivers caused by incorrect memory alignment of bounce buffers
  • Fixed deadlocks that could hang the whole QEMU process in the mirror block job and the NBD export

Tracing

Semihosting

Miscellaneous

  • During startup QEMU system emulators will raise the max file descriptors soft limit to match the hard limit
  • Seccomp filters will now return EPERM rather than killing QEMU if code attempts to spawn a child process. Fixes compatibility with some NVIDIA libraries which try to run modprobe.
  • Thread-local coroutine pools have been mostly replaced by a global pool, which reduces the number of inactive coroutines (and therefore memory mappings) and is limited to a maximum size depending on vm.max_map_count on Linux. This fixes the "failed to set up stack guard page" error that has been reported on Linux hosts where the QEMU coroutine pool exceeded the vm.max_map_count limit.

User-mode emulation

runtime

binfmt_misc

alpha

arm/arm64/aarch64

LoongArch

HPPA

s390

x86

TCG

Record/Replay

  • fixed record/replay to avoid problems with partial chardev drains
  • updated replay-dump.py for current ABI

RISC-V

Guest agent

  • Fix build on Solaris
  • Improve help for --allow-rpcs and --block-rpcs command line options
  • Fix guest-get-fsinfo when a volume has more than one disk (Windows only)
  • Add support of Windows Server 2025 in guest-get-osinfo command (Windows only)

Build Information

Build Dependencies

Build hardening

  • QEMU build will include '-fzero-call-used-regs' to attempt to reduce exploitable ROP gadgets
  • QEMU build will include '-ftrivial-auto-var-init=zero' to reduce the chance of uninitialized stack variables causing security issues

Windows

  • 32-bit Windows is no longer supported as a host OS; use a 64-bit Windows host instead.

Testing and CI

  • The timeout for TCG tests was raised to 120s (for the benefit of TCI)
  • The OpenBSD VM was updated to 7.4

Known issues