[PATCH 0 of 2] x86/mm: Unsharing ENOMEM handling

[Andres Lagar-Cavilla <andres@lagarcavilla.org>]

These two patches were originally posted on Feb 15th as part of a larger
series.

They were left to simmer as a discussion on wait queues took precedence.

Regardless of the ultimate fate of wait queues, these two patches are necessary
as they solve some bugs on the memory sharing side. When unsharing fails,
domains would spin forever, hosts would crash, etc.

The patches also clarify the semantics of unsharing, and comment how it's
handled.

Two comments against the Feb 15th series taken care of here: 
 - We assert that the unsharing code can only return success or ENOMEN.
 - Acked-by Tim Deegan added to patch #1

Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.org>
Signed-off-by: Adin Scannell <adin@scannell.ca>
Acked-by: Tim Deegan <tim@xen.org>

 xen/arch/x86/mm/mem_event.c       |   5 ++-
 xen/include/asm-x86/mem_event.h   |  30 ++++++++++++++++++---
 xen/arch/x86/hvm/hvm.c            |  23 +++++++++++++++-
 xen/arch/x86/mm.c                 |   8 +++--
 xen/arch/x86/mm/mem_sharing.c     |  54 +++++++++++++++++++++++---------------
 xen/arch/x86/mm/p2m.c             |  18 ++++++++++++-
 xen/common/grant_table.c          |  11 ++++---
 xen/common/memory.c               |   1 +
 xen/include/asm-x86/mem_sharing.h |  27 ++++++++++++++++++-
 9 files changed, 138 insertions(+), 39 deletions(-)