Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Merge in support for Xen HVM on amd64 architecture.

Copy the Xen HVM platform device driver from user/dfr/xenhvm/6.

Tidy this up a lot and improve the comments somewhat.

Mark the evtchn interrupt as MPSAFE and respect the INTR_MPSAFE flags passed
when binding event channels to handlers. Add svn:keywords to the files in
sys/dev/xen/xenpci.

Add support for suspend and resume. This currently only works for 64bit HV
mode kernels. A 32bit PV mode kernel will suspend but fails to restore because
Xen gets confused by the magic recursive mappings in the virtual address space.

Don't use pmap_mapdev to map HVM memory areas - this is ordinary physical
memory and we shouldn't use uncacheable mappings for it. Also, don't leak
virtual address space when the grant table size increases.

Add a driver the the Xen HVM special platform device.