From mboxrd@z Thu Jan  1 00:00:00 1970
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Subject: Re: [PATCH v2 0/2] KVM: MMU: fix kvm_is_mmio_pfn()
Date: Thu, 2 Nov 2017 13:37:48 -0400
Message-ID: <20171102173748.GU22924@char.us.oracle.com>
References: <20171031114840.12615-1-haozhong.zhang@intel.com>
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Cc: kvm@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org,
        Paolo Bonzini <pbonzini@redhat.com>, rkrcmar@redhat.com,
        Xiao Guangrong <xiaoguangrong.eric@gmail.com>,
        Dan Williams <dan.j.williams@intel.com>,
        ivan.d.cuevas.escareno@intel.com, karthik.kumar@intel.com,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Borislav Petkov <bp@suse.de>,
        Mikulas Patocka <mpatocka@redhat.com>,
        Tom Lendacky <thomas.lendacky@amd.com>
To: Haozhong Zhang <haozhong.zhang@intel.com>,
        Olif Chapman <olif.chapman@oracle.com>
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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
>