ChangeLog/1.4

System emulation

Various CPU usage and throughput improvements for USB 2.0.
usb-tablet can be connected as an USB 2.0 device, also lowering the CPU usage substantially.
Improved support for pass-through of USB serial devices.
A new device usb-bot is the same as usb-storage, but is configured like other SCSI adapters and supports multiple LUNs.

Added support for IndustryPack emulation. The TEWS TPCI200 device emulation (device "tpci200") hosts IndustryPack modules, and the GE IP-Octal 232 emulation (device "ipoctal232") implements eight RS-232 serial ports.

pSeries: NVRAM support for improved guest installation experience
G3/G4: Allow dcbzl (for Mac OS X guests)
e500: Linux guests don't use use SWTLB anymore, freeing memory for real applications
e500: MSI support
e500: Allow for up to 31 PCI devices with -M ppce500
e500: Support idle hcall when running KVM on e500mc or above
e500: Emulate the EPR facility (e500mc and above)
PReP: Emulate a full PC87312 Super I/O chipset. This adds a parallel port. Changing the chipset configuration register at runtime is not yet supported.

Generation of APIC IDs for NUMA configuration is now compatible with the Intel® 64 Architecture Processor Topology Enumeration
Many fixes to the Q35 chipset emulation, including experimental AHCI migration support and support for device assignment.
Resetting the machine with a write to port 0xCF9 now works.
The xlevel argument for -cpu option currently silently fix-ups the user-provided value if it's less than 0x80000000. This will be removed in future QEMU versions; users are expected to provide valid xlevel value or QEMU will fail to start.

Persistent grants support implemented in xen_disk, giving substantial performance improvements.
xen_disk supports BLKIF_OP_FLUSH_DISKCACHE, making the device safer against power losses.
xen_console supports multiple secondary PV consoles.

New commands chardev-add and chardev-del add support for hotplugging character devices.
Various improvements in error messages

Discard operations are now supported on block devices and on filesystems other than XFS. They are also fully asynchronous now.
Block device mirroring (also known as storage migration) performance was greatly improved.
New experimental threaded backend for virtio-block-pci. This new backend achieves several times the IOPS of the existing virtio-blk implementation; for now it can only be used for raw image files and disables features such as live snapshots and storage migration.

Moved migration from a timer to a thread, improving latency in other parts of QEMU and throughput of migration itself
Many machine models are now correctly marked as not migratable.

A new spiceport character device can be used to support arbitrary communication between the SPICE server on the host and the client.

qemu-ga supports hooks that are executed when the guest receives the guest-fsfreeze-freeze and guest-fsfreeze-thaw commands