[PATCH v4 0/3] KVM: MMU: fix kvm_is_mmio_pfn()

[Haozhong Zhang]

Some reserved pages, such as those from NVDIMM DAX devices, are
not for MMIO, and can be mapped with cached memory type for better
performance. However, the above check misconceives those pages as
MMIO.  Because KVM maps MMIO pages with UC memory type, the
performance of guest accesses to those pages would be harmed.
Therefore, we check the host memory type by lookup_memtype() in
addition and only treat UC/UC- pages as MMIO.


Changes in v4:
 * Mask pfn_t and kvm_pfn_t specific flags in conversion.

Changes in v3:
 * Move cache mode check to pat.c as pat_pfn_is_uc()
 * Reintroduce converters between kvm_pfn_t and pfn_t.

Changes in v2:
 * Switch to lookup_memtype() to get host memory type.
 * Rewrite the comment in KVM MMU patch.
 * Remove v1 patch 2, which is not necessary in v2.


Haozhong Zhang (3):
  x86/mm: add function to check if a pfn is UC/UC-
  KVM: add converters between pfn_t and kvm_pfn_t
  KVM: MMU: consider host cache mode in MMIO page check

 arch/x86/include/asm/pat.h |  2 ++
 arch/x86/kvm/mmu.c         | 19 ++++++++++++++++++-
 arch/x86/mm/pat.c          | 14 ++++++++++++++
 include/linux/kvm_host.h   |  4 ++++
 4 files changed, 38 insertions(+), 1 deletion(-)

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2.14.1