ChangeLog/5.1

System emulation

New deprecated options and features

Consult the "Deprecated Features" chapter of the QEMU System Emulation User's Guide for the full list of historically deprecated features/options.

Arm

• Emulation of the following architecture features is now implemented:
  • ARMv8.2-TTS2UXN
• xlnx-versal-virt: machine now supports RTC and SD
• New board model: sonorapass-bmc
• Host memory errors can now be reported to AArch64 KVM guests via ACPI when using the 'virt' board (this is disabled by default; enable with '-machine ras=on')
• All the imx6 and imx7 machines now support the watchdog timer device

PowerPC

• The "label-size" property is now mandatory for NVDIMMs on the "pseries" machine type (the PAPR specification only supports labelled NVDIMMs)
• NVLink2 devices can no longer be unplugged. This is not possible on real hardware, and was never supported by the guest side drivers, so this makes things safer.
• We no longer use reconfiguration reboots to handle difficult cases during CAS option negotiation
• Added an interface to inject POWER style NMIs

RISC-V

• Spike machine supports more then 1 CPU
• Spike machine supports the `-bios` option
• OpenSBI updated to v0.7
• linux-usermode improvements
• Support for the SiFive E34 CPU
• 32-bit improvements for the `sifive_u` machine
• Corrections to the Hypervisor extension page table walking
• Expose a "serial" property for the `sifive_u` machine that specifys the board serial number

s390

• Support for protected virtualization aka secure execution has been merged (KVM only)
  • The host needs to be a z15 or Linux One III with at least Linux 5.7

Device emulation and assignment

ACPI

• QEMU now exposes a WAET (Windows ACPI Emulated Devices Table) to guests -

this reduces virtualization overhead for non-enlightened windows (Vista and later) guests by avoiding guest workarounds for an unreliable ACPI PM timer.

• QEMU now supports both cold and hot plug of nvdimms for ARM Guests with ACPI.

PCI/PCIe

Attempts to hotplug devices into a pci slot with hotplug disabled will now return an error instead of adding the device without notifying the guest.

virtiofs

• virtiofsd:
  • Security fix: CVE-2020-10717, resource exhaustion of host fd's
  • Jailing improvements
  • Ensure that existing mounts under the shared directory are visible to the guest

Character devices

• The 'socket' backend now supports the abstract namespace for UNIX sockets, with the new 'abstract' and 'tight' options

GUI

• Windows keyboard fixes for GTK and SDL

GDBStub

• bug fix to m68k gdbstub
• linux-user now supports unix socket for debugging (needs a new gdb)
• some tests for the stub added to check-tcg

Block device backends and tools

• Optional zstd compression for qcow2 (enable with compression_type=zstd as a creation option)
• Fixed regression with 'qemu-nbd -c /dev/nbd0' keeping inherited stderr open (introduced in 4.1)
• 'qemu-img map' gained --start-offset and --max-length options for mapping only a subset of a file
• 'qemu-img' gained a new command mode 'bitmap' for manipulating persistent bitmaps in qcow2 files

Build Information

Build Dependencies

• Now requires GTK 3.22 or newer

Testing

• vm-build tests can now use alternatives to genisoimage (cdrkit)

Known issues

• see Planning/5.1