Re: [PATCH v2 0/2] KVM: MMU: fix kvm_is_mmio_pfn()

[Konrad Rzeszutek Wilk]

On Tue, Oct 31, 2017 at 07:48:38PM +0800, Haozhong Zhang wrote:
> [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.

Is there a specific workload you used to detect this?

Thanks!
> 
> 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
>