ChangeLog/2.0

System emulation

ARM

• Support for "-M virt", a board type that only uses virtio devices
• Support for "-cpu host" when running under KVM
• Support for new ARMv8 instructions in TCG
• Support for AArch64 disassembling (requires a C++ compiler to be installed on the host)
• Support for AArch64 user-mode emulation
• Support for AArch64 system-mode emulation using KVM
• Support for the Canon PowerShot A1100 DIGIC board using "-M canon-a1100"
• Support for the allwinner-a10-based board "-M cubieboard"
• Support for flow control in the Cadence UART

Power

• Support for VSX instructions when running under TCG
• Prep is not anymore (incorrectly) included in qemu-system-ppcemb

x86

• On the Q35 machine, the HPET interrupt can now be attached to GSIs 16-23, like on real hardware.
• The Q35 machine now supports CPU hotplug.
• Two flash chips can be specified using the "-drive if=pflash" or "-pflash" options twice.
• Memory layout has changed slightly; to improve performance, the PIIX4 machine ("-M pc") now has 3GB of low memory instead of 3.5GB if the guest has more than 3.5GB of memory. Similarly, the Q35 machine ("-M q35") now has 2GB instead of 2.75GB of low memory if the guest has more than 2.75GB of overall memory.
• Support for migration of Intel MPX registers.
• The Apple SMC device is now exposed in the ACPI tables.
• PCI hotplug now supports devices behind a bridge (only for bridges not added by hotplug; hot-plugged bridges can still use the PCI Standard Hot-Plug Controller).
• Support for the Hyper-V reference time counter via the "hv-time" suboption of "-cpu". This can improve performance of Windows guests substantially for applications that do many floating-point or SIMD operations. (Requires KVM and Linux 3.14).

Xen

• PCI passthrough of devices with a ROM now works.

Device emulation

SCSI

• the SCSI layer can offload the WRITE SAME command to the host storage. This is supported on XFS file systems, raw devices, and iSCSI targets.

USB

• support for suspend-to-RAM in the XHCI controller
• support for Microsoft descriptors, to make Windows use remote suspend by default.

Block devices

• when the destination of "qemu-img convert" is a raw device, can ask the host storage to "discard" it instead of writing zeroes
• "qemu-img convert" can be passed a "-S 0" option to create a fully allocated image
• "qemu-img convert" can use hints from the host storage to speed up the transfer
• Live snapshot merge (...-commit) can be used to merge the active layer of an image into one of the snapshots
• Live and offline snapshot merge ("commit") will resize the destination image if necessary.
• The iSCSI backends support snapshot merge.
• The libcurl interface had bitrotted and has been fixed.
• QEMU is able to operate even if the underlying storage requires the buffer size to be a 4K multiple. This is the case for 4K-native disks (with cache=none or when accessed through iscsi:// URLs) and some raw devices. When this happens, QEMU emulates unaligned accesses using read-modify-write cycles if necessary. On properly configured guests newer than ~2009 there should be no performance penalty.
• qemu-io supports command editing via readline
• Pseudo-protocols like blkdebug and blkverify can be nested arbitrarily
• "query-block-stats" provides statistics for all images in the chain of backing files
• node-name, query-named-block-nodes: external snapshot, resize, change password
• Improved error messages for many operations
• QEMU can access NFSv3 shares directly from userspace using libnfs. The share must be configured to allow access from high-numbered ports

GUI

• Windows hosts support keyboard translation in the GTK+ interface

VNC

• setting the password via monitor command will not enable password auth as side effect any more. Use "qemu -vnc ${display},password" on the command line to enable password authentication.

Monitor

• New HMP command cpu-add for CPU hotplug
• New QMP commands object-add and object-del for generic object hotplug (enables virtio-rng hotplug)
• New HMP commands object_add and object_del for generic object hotplug
• Improved command-line completion for device_add and device_del (as well as the new commands object_add and object_del)

Migration

• Reduction (or elimination) of guest stalls during migration

Network

• New backend "netmap" on BSD systems

TCG

• QEMU can use getauxval to detect the host instruction set for PPC64, ARM, s390
• QEMU supports generating MOVBE instructions in the x86 backend

User-mode emulation

• support for several more system calls and parameters