Pull additional xen update from David Vrabel:
 "Xen: additional features for 3.19-rc0

   - Linear p2m for x86 PV guests which simplifies the p2m code,
     improves performance and will allow for > 512 GB PV guests in the
     future.

  A last-minute, configuration specific issue was discovered with this
  change which is why it was not included in my previous pull request.
  This is now been fixed and tested"

* tag 'stable/for-linus-3.19-rc0b-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen: switch to post-init routines in xen mmu.c earlier
  Revert "swiotlb-xen: pass dev_addr to swiotlb_tbl_unmap_single"
  xen: annotate xen_set_identity_and_remap_chunk() with __init
  xen: introduce helper functions to do safe read and write accesses
  xen: Speed up set_phys_to_machine() by using read-only mappings
  xen: switch to linear virtual mapped sparse p2m list
  xen: Hide get_phys_to_machine() to be able to tune common path
  x86: Introduce function to get pmd entry pointer
  xen: Delay invalidating extra memory
  xen: Delay m2p_override initialization
  xen: Delay remapping memory of pv-domain
  xen: use common page allocation function in p2m.c
  xen: Make functions static
  xen: fix some style issues in p2m.c