[PATCH 0 of 3] Fixes for paging/sharing with AMD processors

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

These are patches previously posted as RFC towards making paging and sharing
work for AMD NPT.

They are now ready for inclusion in the tree. They do not yet completely fix
paging in AMD, but each fixes an existing bug:

- Add "no-sharept" cli to allow disabling of sharing of iommu and p2m tables.
- Mask high order bits when installing INVALID_MFN on a pte, so those bits
don't trample over flags such as _PAGE_NX. I've used a suggestion from Tim
Deegan in this patch, so I took the liberty of adding his SoB.
- Teach paging to the page table-based p2m (p2m-pt). This involves fixing a few
if's and ASSERT's.

They've been tested to not break existing modes (shadow, AMD hap, dom0 as test
for pv domains)

Signed-off-by: Andres Lagar-Cavilla<andres@lagarcavilla.org>
Signed-off-by: Tim Deegan <tim@xen.org>

 xen/drivers/passthrough/iommu.c |   2 ++
 xen/include/asm-x86/page.h      |  12 ++++++++----
 xen/arch/x86/mm/p2m-pt.c        |  30 +++++++++++++++++++-----------
 3 files changed, 29 insertions(+), 15 deletions(-)