[Xen-devel] [PATCH 0 of 5] Synchronized p2m lookups

[Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>]

Up until now, p2m lookups (get_gfn*) in the x86 architecture were not
synchronized against concurrent updates. With the addition of sharing and
paging subsystems that can dynamically modify the p2m, the need for
synchronized lookups becomes more pressing.

Without synchronized lookups, we've encountered host crashes triggered by race
conditions, particularly when exercising the sharing subsystem.

In this patch series we make p2m lookups fully synchronized. We still use a
single per-domain p2m lock (profiling work tbd may or may not indicate the need
for fine-grained locking).

We only enforce locking of p2m queries for hap-assisted domains. These are the
domains (in the case of EPT) that can exercise the paging and sharing
subsystems and thus most in need of synchronized lookups.

While the code *should* work for domains relying on shadow paging, it has not
been tested, hence we do not enable this at the moment.

Finally, the locking discipline in the PoD subsystem has been updated, since
PoD relied on some assumptions about the way the p2m lock is used.

Signed-off-by: Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>
Signed-off-by: Adin Scannell <adin@xxxxxxxxxxx>

 xen/arch/x86/mm/hap/hap.c        |    6 ++
 xen/arch/x86/mm/mm-locks.h       |   40 ++++++++-----
 xen/arch/x86/mm/p2m.c            |   21 ++++++-
 xen/include/asm-x86/p2m.h        |   47 ++++++++++------
 xen/arch/x86/mm/mem_sharing.c    |    2 -
 xen/arch/x86/mm/mm-locks.h       |    4 +-
 xen/arch/x86/mm/p2m-ept.c        |   33 +----------
 xen/arch/x86/mm/p2m-pod.c        |   14 +++-
 xen/arch/x86/mm/p2m-pt.c         |   45 ++------------
 xen/arch/x86/mm/p2m.c            |   64 +++++++++++----------
 xen/arch/x86/mm/mm-locks.h       |   10 +++
 xen/arch/x86/mm/p2m-pod.c        |  112 +++++++++++++++++++++++---------------
 xen/arch/x86/mm/p2m-pt.c         |    1 +
 xen/arch/x86/mm/p2m.c            |    8 ++-
 xen/include/asm-x86/p2m.h        |   27 ++------
 xen/arch/x86/hvm/emulate.c       |    2 +-
 xen/arch/x86/hvm/hvm.c           |   25 +++++--
 xen/arch/x86/mm.c                |   10 +-
 xen/arch/x86/mm/guest_walk.c     |    2 +-
 xen/arch/x86/mm/hap/guest_walk.c |    6 +-
 xen/arch/x86/mm/mem_access.c     |   10 +++
 xen/arch/x86/mm/mem_event.c      |    5 +
 xen/arch/x86/mm/p2m.c            |   52 ++++++++++--------
 xen/common/grant_table.c         |    2 +-
 xen/common/memory.c              |    2 +-
 xen/include/asm-x86/mem_access.h |    1 +
 xen/include/asm-x86/mem_event.h  |    3 +
 xen/include/asm-x86/p2m.h        |    6 +-
 xen/arch/x86/mm/p2m.c            |    4 +-
 29 files changed, 312 insertions(+), 252 deletions(-)

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