ChangeLog/5.0

System emulation

Incompatible changes

• The bluetooth code has been removed without replacement. It was quite neglected over the years and likely not usable anymore. You can passthrough a dedicated USB bluetooth dongle to guests on most machines instead if you still need bluetooth in your guest.
• The pc-0.12, pc-0.13, pc-0.14, pc-0.15 machines have been removed. Newer versions of the machine type should be used instead.
• The "prep" ppc machine has been removed. The "40p" machine should be used now instead.
• The "-virtfs_synth" option has been removed. You can use "-fsdev synth" together with "-device virtio-9p-..." instead.
• The "-accel" and "-machine accel=" options are now incompatible with each other.

New deprecated options and features

• The "-tb-size N" option has been deprecated. It is replaced by "-accel tcg,tb-size=N".
• The virtio-blk SCSI passthrough feature (" -device virtio-blk,scsi=on") is deprecated. Use virtio-scsi instead.
• The "r4k" mips machine has been deprecated. The "malta" machine should be used nowadays instead.

Consult the "Deprecated Features" appendix for the full list of historically deprecated features/options.

Arm

• Emulation of the ARMv8.1-VHE architecture feature is now implemented
• The Cortex-M7 CPU is now supported
• New board: tacoma-bmc
• New board: Netduino Plus 2
• QEMU now correctly implements trapping of more EL1 system register accesses to EL2 (eg HCR_EL2 TID1, TID2 bits, HSTR_EL2)
• The no-op system registers required for a "trivial Jazelle" implementation have been added
• The DC CVAP and DC CVADP instructions are now supported
• Support for blocking semiconsole SYS_READC
• the i.MX RNGC device is now supported
• The Cortex-R5 and -R5f CPUs now provide a PMU
• The Exynos4210 SoC model now correctly handles DMA to/from the UARTs
• The Aspeed AST2600 SoC model now includes the eMMC controller
• Under KVM, we now by default stop and restart the guest generic timer counter when the VM is stopped and started so the guest OS doesn't see surprising time jumps. (This can be disabled with the kvm-no-adjvtime property.)

MIPS

• Support for R4000 machine is announced to be deprecated, and will be removed from code base in QEMU 5.2.

OpenRISC

• Fixed a bug that prevented the DZF bit of the FPCSR being set.

PowerPC

• pseries machine type
  • No longer require a reconfiguration reboot for a guest selecting XIVE interrupt controller when ic-mode=dual
  • Now consumes less host resources when running a KVM guest with XIVE (with a recent enough host kernel). This allows running more concurrent guests with KVM accelerated XIVE.
• powernv machine type
  • Numerous improvements to the model
  • Can now run KVM guests under a TCG emulated powernv machine
  • Basic POWER10 support
  • Removed num-chips machine property, use -smp sockets=NN instead

s390

• Adpater interrupt suppression is now available when running with KVM (previously disabled due to migration issues); support under tcg has already been available since 2.10
  • enable by specifying the cpu feature "ais=on"

Device emulation and assignment

9pfs

• Client is required to negotiate msize >= 4096 (9p client in linux already does that)

GUI

• The VNC server websocket impl has fixed compatibility with noVNC

Monitor

QMP

• The QMP command nbd-server-add now supports a 'description' parameter to match the behavior of command-line qemu-nbd --description.

Migration

• Add dbus-vmstate, a backend that allows external processes to migrate their data along with QEMU. See the documentation.

Block device backends and tools

• The command line qemu-nbd --partition, deprecated in 4.0, has been removed. Exposing a single partition of an image through NBD should now be accomplished via other means, such as using the offset and size parameters of an intermediate raw driver.

Tracing

• DEBUG_MMAP build hack replaced by target_mmap_* tracepoints

Miscellaneous

• It is now possible to specify multiple "-accel" options. The first available accelerator will be used. For example, "-machine accel=kvm:tcg" can now be expressed as "-accel kvm -accel tcg" with the added possibility of including options to configure the accelerator.
• KVM and Xen-specific machine options have been moved to "-accel"; the previous way to set the option is still available for backwards-compatibility. The options that were moved are:
  • "-machine kernel_irqchip=" (now "-accel kvm,kernel-irqchip=")
  • "-machine kvm_shadow_mem=" (now "-accel kvm,kvm-shadow-mem=")
  • "-machine igd-passthru=" (now "-accel xen,igd-passthrough=")
• changing the logfile via HMP is now atomically thread-safe
• virtiofsd is now included, this works with the vhost-user-fs device to provide a passthrough to a host filesystem directory.

Guest agent

• The 'set-guest-time' command is now fenced off on systems that do not have the 'hwclock' command available (e.g. on s390x).

Build Information

Container Based Builds

• --disable-containers allows configure to skip attempting to use them from cross builds (useful on non-x86 builds)

Testing

• multiarch targets added to Travis

Known issues

• see Planning/5.0