ChangeLog/4.2

System emulation

Incompatible changes

• The minimum version of the glib library is now 2.48

New deprecated options and features

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

68k

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

MIPS

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

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.

Device emulation and assignment

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.

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.

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)

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.

User-mode emulation

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/)

Build Information

Python

• The minimum supported version of Python is now 3.5.

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

Known issues

• see Planning/4.2