ChangeLog/2.0

System emulation

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).

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.

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

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

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.

New HMP command cpu-add for CPU hotplug.
New HMP commands object-add and object-del for generic object hotplug (enables virtio-rng hotplug).
New QMP commands object_add and object_del for generic object hotplug.