From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1752567AbdKBGsQ (ORCPT <rfc822;w@1wt.eu>);
        Thu, 2 Nov 2017 02:48:16 -0400
Received: from mga01.intel.com ([192.55.52.88]:12153 "EHLO mga01.intel.com"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1750883AbdKBGsO (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Thu, 2 Nov 2017 02:48:14 -0400
X-ExtLoop1: 1
X-IronPort-AV: E=Sophos;i="5.44,332,1505804400"; 
   d="scan'208";a="1032498153"
Date: Thu, 2 Nov 2017 14:48:19 +0800
From: Haozhong Zhang <haozhong.zhang@intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: linux-kernel@vger.kernel.org, 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>, kvm@vger.kernel.org,
        x86@kernel.org
Subject: Re: [PATCH v2 0/2] KVM: MMU: fix kvm_is_mmio_pfn()
Message-ID: <20171102064819.7uu622mt6omcwtfk@hz-desktop>
Mail-Followup-To: Paolo Bonzini <pbonzini@redhat.com>,
        linux-kernel@vger.kernel.org, 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>, kvm@vger.kernel.org,
        x86@kernel.org
References: <20171031114840.12615-1-haozhong.zhang@intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20171031114840.12615-1-haozhong.zhang@intel.com>
User-Agent: NeoMutt/20170714 (1.8.3)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 10/31/17 19:48 +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.
> 
> 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
> 

Hi Paolo,

This patchset fixed a performance drop issue when using NVDIMM on KVM,
so I think it's nice to have in 4.14. Can you help to review it?

Thanks,
Haozhong