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.

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