ChangeLog/4.2

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System emulation

Incompatible changes

  • The minimum version of the glib library is now 2.48
  • On s390x, using KVM now explicitly requires a host kernel version of at least 3.15 (which includes the 'flic' KVM device). This had been broken since QEMU 2.10 already.

New deprecated options and features

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

Alpha

68k

  • Added new "next-cube" machine for emulating a classic NeXTcube (still incomplete, can only boot to the firmware prompt)

Arm

  • Added Aspeed AST2600 SoC support
  • QEMU's Arm semihosting implementation now supports v2.0 of the specification, including the "STDOUT_STDERR" and "EXIT_EXTENDED" extensions
  • We now correctly support more than 256 CPUs when using KVM

HPPA

Microblaze

MIPS

  • Fixed bug involving emulation of ST.W instruction in system mode only (there was no bug in Linux user mode).

Nios2

OpenRISC

PowerPC

  • Behavior for unplug of multifunction PCI devices has been changed to match x86. Attempting to unplug any function will cause an unplug of the whole slot.
  • There are now separate machine types for POWER8 based and POWER9 based non-virtualized machines (powernv8 & powernv9).
  • Default RAM size for powernv machines has been increased to 1.75G which should allow more things to work with the default parameters.
  • RTAS (runtime firmware) code is now supplied by SLOF (boot time firmware) instead of by qemu itself. This won't affect users in most cases, but will affect users of -bios which bypasses SLOF, which includes kvm-unit-tests. You'll need a sufficiently recent version of kvm-unit-tests to handle this.
  • mffsce, mffscrn and mffscrni POWER9 instructions now supported in TCG
  • powernv machine now includes models for the Homer and OCC SRAM system devices
  • "info pic" HMP command now reports whether the irq chip is emulated in kernel or in qemu
  • pseries machine type no longer permits NUMA nodes with no CPU and no memory - this was already unlikely to work due to problems expressing this configuration to the guest

RISC-V

  • The `-initrd` argument is now supported.

s390

  • TCG now implements IEP (Instruction Execution Protection), a CPU feature introduced with the z14. Until the "qemu" CPU model is lifted to a z14, it can be enabled using the "max" CPU model ("-cpu max").

SH

SPARC

TileGX

Tricore

x86

Xtensa

Device emulation and assignment

ACPI

Audio

Block devices

GPIO

Graphics

Input devices

IPMI

IPMI UUIDs

UUID handling for the built-in IPMI BMC has changed. Before the UUID was set from the qemu UUID, if that was set. However, in a real system, the UUID of a BMC will be independent of the system UUID. So now the UUID must be explicitly set for a BMC if you want one. Otherwise the BMC will not have a UUID.

To set the UUID of a BMC, use the new property guid=11223344-5566-7788-99aa-bbccddeeff00 for the ipmi-bmc-sim device.

IPMI PCI Devices

New PCI interfaces for IPMI KCS and BT devices are available. The devices pci-ipmi-kcs and pci-ipmi-bt are used to choose these devices.

Network devices

NVDIMM

PCI/PCIe

SCSI

SMBIOS

TPM

USB

VFIO

virtio

  • virtio-mmio now supports the virtio standard compatible v2 personality (still defaulting to the legacy v1 personality for compatibility reasons)

Xen

fw_cfg

9pfs

  • the "local" backend now has a new 'multidevs' option to deal with cross-device setups (ie. when the shared directory spans over multiple devices on the host)

Semihosting

Audio

Character devices

Crypto subsystem

GUI

Host support

  • Any backend that supports connection as an Inet client (NBD, chardev, network device, monitor...) can now request to use TCP keep-alive with the server.

Memory backends

Monitor

  • bugs in gdbstub handling of F and ! packets have been fixed

Migration

  • The 'validate-uuid' migration compatibility checks the UUID matches on migration, preventing accidental migration of the wrong VM to the wrong destination. (Yury Kotov)

Network

  • The user mode host network backend now allows to set a guest-visible DNS address which is not in the virtual network, unless restrict mode is enabled.

Block device backends and tools

  • Block drivers can now support BDRV_REQ_PREFETCH for more efficient handling of copy-on-read requests; the NBD driver has wired this up to NBD_CMD_CACHE.
  • The LUKS block driver supports falloc/full preallocation.
  • The NBD server now advertises NBD_FLAG_CAN_MULTI_CONN on shared readonly connections.
  • The NBD server and client support the new NBD_CMD_FLAG_FAST_ZERO as an optimization during the copying of sparse images.
  • The backup block job now creates a filter node, just like mirror and commit do. Clients that care about the structure of the block graph need to take this into account.
  • Several assertion failures relating to the use of an NBD server with iothreads have been fixed.

Tracing

Miscellaneous

User-mode emulation

Alpha

Xtensa

  • call0 ABI may be selected for the user emulation with command line option -xtensa-abi-call0 (or with QEMU_XTENSA_ABI_CALL0 environment variable).

TCG

  • The tcg tests have had their configuration and build somewhat dissentagled from the main make file
  • tcg tests are now in $BUILDDIR/tests/tcg/$TARGET/ (rather than $BUILDDIR/$TARGET/tests/)

Guest agent

Build Information

Python

  • The minimum supported version of Python is now 3.5.

GIT submodules

Container Based Builds

  • The docker.py tooling now supports podman containers [1] as an alternative to docker
  • the docker.py now requires python3 to run
  • a number of the cross compiler containers have been updated to Buster

Build Dependencies

  • The minimum version of the glib library is now 2.48

Testing

Windows

Known issues