Pull Xen updates from David Vrabel:
 "Features and fixes:

   - Add pvscsi frontend and backend drivers.
   - Remove _PAGE_IOMAP PTE flag, freeing it for alternate uses.
   - Try and keep memory contiguous during PV memory setup (reduces
     SWIOTLB usage).
   - Allow front/back drivers to use threaded irqs.
   - Support large initrds in PV guests.
   - Fix PVH guests in preparation for Xen 4.5"

* tag 'stable/for-linus-3.18-rc0-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip: (22 commits)
  xen: remove DEFINE_XENBUS_DRIVER() macro
  xen/xenbus: Remove BUG_ON() when error string trucated
  xen/xenbus: Correct the comments for xenbus_grant_ring()
  x86/xen: Set EFER.NX and EFER.SCE in PVH guests
  xen: eliminate scalability issues from initrd handling
  xen: sync some headers with xen tree
  xen: make pvscsi frontend dependant on xenbus frontend
  arm{,64}/xen: Remove "EXPERIMENTAL" in the description of the Xen options
  xen-scsifront: don't deadlock if the ring becomes full
  x86: remove the Xen-specific _PAGE_IOMAP PTE flag
  x86/xen: do not use _PAGE_IOMAP PTE flag for I/O mappings
  x86: skip check for spurious faults for non-present faults
  xen/efi: Directly include needed headers
  xen-scsiback: clean up a type issue in scsiback_make_tpg()
  xen-scsifront: use GFP_ATOMIC under spin_lock
  MAINTAINERS: Add xen pvscsi maintainer
  xen-scsiback: Add Xen PV SCSI backend driver
  xen-scsifront: Add Xen PV SCSI frontend driver
  xen: Add Xen pvSCSI protocol description
  xen/events: support threaded irqs for interdomain event channels
  ...