[I just copy the commit message from patch 2] 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 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 (2): x86/mm: expose lookup_memtype() KVM: MMU: consider host cache mode in MMIO page check arch/x86/include/asm/pat.h | 2 ++ arch/x86/kvm/mmu.c | 30 +++++++++++++++++++++++++++--- arch/x86/mm/pat.c | 3 ++- 3 files changed, 31 insertions(+), 4 deletions(-) -- 2.14.1
