ChangeLog/4.1

System emulation

New deprecated options and features

• The "-virtfs_synth" option is now deprecated. Please use "-fsdev synth" and "-device virtio-9p-..." instead.

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

Arm

• QEMU now supports emulating an FPU for Cortex-M CPUs, and the Cortex-M4 and Cortex-M33 now provide the FPU.
• The build config files have been switched to the new Kconfig system, so that a QEMU with individual boards can be built more easily

MIPS

• Marking referenced memory pages as executable is improved (it is restricted to necessary cases only).
• Emulation of MSA ASE instructions on big endian hosts is fixed for instructions LD.<B|H|W|D>, ST.<B|H|W|D>, COPY_S.<B|H|W|D>, COPY_U.<B|H|W>, and INSERT.<B|H|W|D>.
• The 'division by zero' cases in MSA ASE instructions DIV_<U|S>.<B|H|W|D> and MOD_<U|S>.<B|H|W|D> are now handled in QEMU and on the reference hardware the same way.

PowerPC

• NVIDIA V100 GPU/NVLink2 passthrough for spapr using VFIO PCI

s390

• The bios now supports IPL (boot) from ECKD DASD assigned to the guest via vfio-ccw.

x86

• New Hygon Dhyana CPU model
• The host-cache-info CPU option now affects the TOPOEXT CPUID leaf (0x8000001D)

Memory backends

• QEMU will automatically try to use the MAP_SYNC mmap flag for memory backends configured with pmem=on,share=on

Block devices and tools

• qemu-img rebase works now even when the input file doesn't have a backing file yet

Miscellaneous

• Unless QEMU is configured with --disable-blobs, make install will install UEFI platform firmware binaries, and matching variable store templates, at $prefix/share/qemu/edk2-*.fd.
  • These files are built from the edk2 project's ArmVirtPkg and OvmfPkg firmware platforms, and the edk2 project's OpenSSL submodule.
  • They are documented (and exposed to virt management applications) through JSON files in $prefix/share/qemu/firmware/.
  • The schema definition for the JSON descriptors is located at docs/interop/firmware.json in the QEMU source tree.

User-mode emulation

Alpha

• Fix for linux-user emulation of fp exceptions (launchpad bug 1701835)

Build Information

The configure argument --source-path has been removed. This argument used to be provided to allow the user to specify that the source tree was in a different location from the configure script itself. This odd way of building is no longer supported, and we always assume that the source tree is where the configure script is. (Note that a separate build tree is still permitted -- the build tree is the working directory in which configure is run.)

Python

• Build and test scripts will now use the python3 binary by default if available

Known issues

• see Planning/4.1