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System emulation

All targets

  • ... QMP error changes go here ...
  • File descriptors can be passed to qemu using the new add-fd/remove-fd QMP commands. It is intended that they can be used in any place where QEMU would expect a file name. This is ensured for disk images, support in other parts of QEMU may still be inconsistent.


  • LPAE (large physical address extensions) are now supported for the Cortex-A15 CPU; you can now run a vexpress-a15 model with more than 4GB of RAM
  • The new monitor command "dump-guest-memory" creates an ELF dump of the guest memory.
  • New board model: i.MX31


  • The pSeries target correctly creates segment size device tree nodes (fixes odd bugs with HV vs PR KVM)
  • The pSeries target implements an IOMMU.
  • ... pSeries VGA, USB, etc.? ...
  • The E500 target generates its device tree dynamically
  • New mpc8544ds -machine option: dumpdtb. This allows to dump the dynamically generated device tree to a file.
  • Emulation for e5500 cores


  • Support for PCI passthrough is available for Xen fully-virtualized domains.
  • The new monitor command "dump-guest-memory" creates an ELF dump of the guest memory.
  • When using KVM, the in-kernel APIC supports MSI.
  • Also when using KVM, new PV EOI feature improves performance when both host and guest run linux 3.6-rc1 and up. To enable, add +kvm_pv_eoi to -cpu option, e.g.
-cpu kvm64,+kvm_pv_eoi
  • The "cpudef" config file section is being deprecated and may be removed in v1.3.

Device emulation

  • VGA and QXL cards (obtained with -vga std and -vga qxl) have 16 MB of VRAM rather than 8 MB.
  • Three new SCSI host bus adapter devices are available: am53c974 and dc390 emulate respectively an AMD PCI PCscsi and a Tekram DC-390 device, both of which are supported on older operating systems including MS DOS 6.2, MS Windows 3.11, 98 SE, NT 3.1 and NT 4.0. megasas emulated an LSI SAS1078 RAID controller. The next version of SeaBIOS will support booting from am53c974 and dc390 disks.
  • An USB-attached SCSI controller is now available.

Audio devices

  • The PC speaker audio card is now available by default.

Network devices

  • The guestfwd argument to slirp now supports running an arbitrary command on every TCP connection (as in inetd). This is invoked by specifying a target that starts with "cmd:".

Block devices

  • Emulated IDE and SCSI as well as virtio-blk devices can now switch the cache mode between writethrough and writeback. virtio-blk automatically switches to writethrough if the guest driver doesn't support flushes.
  • The default cache mode for images is now writeback.
  • Emulated SCSI devices can be given a custom vendor name, product name and WWN.
  • Improved support for passthrough of SCSI tapes and media changers.
  • libiscsi can be used together with scsi-generic to pass iSCSI tapes and media changers to the guest.
  • When raw files are streamed, parts of the files that are holes in the underlying filesystem are treated as unallocated (as long as the OS supports either the FIEMAP ioctl or the SEEK_HOLE/SEEK_DATA modes)
  • CD-ROM drives can now be used with AHCI


  • qcow2 images support a new option, lazy_refcounts. If on, the speed of cache=writethrough mode will be improved, at the cost of requiring an fsck-like pass (and thus QEMU 1.2) to use the image again after a power loss.
  • qemu-img check can now repair qcow2 and QED images with the new -r option.


  • Support for images in the streamOptimized subformat has been fixed. This is a VMDK subformat commonly used with OVF appliances.


  • rbd no longer ignores the cache setting

Live Migration, Save/Restore

  • Migration works much better with guests with large memory.
  • USB mass storage and passthrough devices support live migration.


  • The threaded VNC server is now enabled by default.

Guest agent

  • A new command "fstrim" was added to the guest agent.

New targets

  • OpenRISC is now supported for both user-mode and system emulation.

Build dependencies

  • No changes from 1.1.0.