ChangeLog/2.7

System emulation

Incompatible changes

• Support for the original qcow2 image encryption has been disabled entirely from the system emulators. While QEMU 2.3 attempted to keep it available in system emulators, a bug in the code has actually broken it since 2.4, and no one complained. Supported for the format remains available only in command line tools qemu-img, qemu-io, qemu-nbd to facilitate data liberation. It is recommended to use 'qemu-img convert' to convert qcow2 encrypted images to uncrypted ones. The new LUKS encryption driver can provide a secure replacement, and a future release may integrate luks into qcow2 natively.
• Autoconverge is not considered experimental anymore; autoconverge-related commands do not have the "x-" prefix anymore.

Future incompatible changes

• Three options are using different names on the command line and in configuration file. In particular:
  • The "acpi" configuration file section matches command-line option "acpitable";
  • The "boot-opts" configuration file section matches command-line option "boot";
  • The "smp-opts" configuration file section matches command-line option "smp".

-readconfig will standardize on the name for the command line option.

• Behavior of automatic calculation of SMP topology when some SMP topology options for -smp are omitted (sockets, cores, threads) will change in the future. If guest ABI needs to be preserved on upgrades while using the SMP topology options, users should either set set all options explicitly (sockets, cores, threads), or omit all of them.
• Devices "allwinner-a10", "pc87312", "ssi-sd" will be configured with explicit properties instead of implicitly. This is unlikely to affect users.
• QMP command blockdev-add is still a work in progress. It doesn't support all block drivers, it lacks a matching blockdev-del, and more. It might change incompatibly.

ARM

• The "virt" machine type has support for NUMA.
• We now implement an emulated GICv3 interrupt controller, which is supported by the "virt" board and can be enabled with "-machine gic-version=3". Note that many guest OSes do not correctly support a GICv3 without security extensions; if your guest is Linux it must include commit 7c9b973061 "irqchip/gic-v3: Configure all interrupts as non-secure Group-1" or a backport of that patch to one of the stable branches. UEFI and FreeBSD are also known to need similar bug fixes.With a GICv3 the "virt" board now supports TCG (emulated CPU) configurations with more than 8 vCPUs.
• New Xilinx Zynq ZCU102 board (-M xlnx-zcu102).
• Xilinx Zynq boards have experimental support for ARM Security Extensions.
• Xilinx Zynq MP supports DisplayPort (graphics and audio) and DDC (used for EDID info).
• i.MX6?

KVM

• Xilinx Zynq boards support KVM on AArch64 hosts.

PowerPC

• Many TCG fixes.

pSeries

• Significant performance improvements for the spapr-llan device.
• Support for CPU hotplug.

s390

• Support for runtime instrumentation
• The IPL firmware can boot from devices in subchannel sets > 0
• Major refactoring and improvements of the s390x-specific PCI code
  • Optionally, zPCI specific 'uid' and 'fid' attributes may be provided
  • Guest-acknowledged hotunplug (rather than 'surprise removal' only)
• bootindex support for IPL from SCSI devices

Device emulation and assignment

Block devices

• Removed dataplane blockers? (Fam)

SCSI

• scsi-block now passes sense data correctly to the guest, so that it can support for example persistent reservations.

USB

• Support for Xen paravirtualized USB

VFIO

• Support for device assignment of Intel integrated graphics devices.

virtio

• Initial reconnect support for vhost-user.

GUI

• A new option "-machine graphics=on|off" lets you disable graphics in the VM like "-nographic" (e.g. OpenBIOS will use the serial port for boot messages) but without an implicit "-display none".

Migration

• Autoconverge is not considered experimental anymore. Autoconverge-related commands do not have the "x-" prefix.
• TODO: TLS support

Network

• New device e1000e for Intel 82574 NIC.

Block devices and tools

• New "bench" command in qemu-img .
• The "write" command in qemu-io grew "-f" and "-z -u" options.

TCG

• Speed improvements around 20%.

Tracing

• TODO: dfilter

User-mode emulation

• The long standing issue of linux-user failing to emulate signals and threads properly has been fixed thanks to Timothy E Baldwin's patchset implementing system call restarting, and Peter Maydell's further fixes
• fixes to fcntl, fadvise, msgrcv and other syscalls
• added rtnetlink(7) support

Deprecated and removed host or target support

• QEMU no longer supports building the linux-user targets on HPPA or m68k host systems
• The unicore32-linux-user target is unmaintained and implements a different system call ABI from mainline Linux for this architecture. We plan to drop support for it in QEMU 2.8.

Build dependencies

• The GTK+ user interface now supports VTE 2.91.
• The SDL user interface is now built if SDL2 is the only available version.

Known issues

• Statically linked system emulators crash due to ifunc.