From patchwork Fri Nov 3 01:16:20 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Haozhong Zhang X-Patchwork-Id: 10039451 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 7E02B6028E for ; Fri, 3 Nov 2017 01:16:51 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7066D29472 for ; Fri, 3 Nov 2017 01:16:51 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 6516129474; Fri, 3 Nov 2017 01:16:51 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id F0A7629472 for ; Fri, 3 Nov 2017 01:16:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965025AbdKCBQg (ORCPT ); Thu, 2 Nov 2017 21:16:36 -0400 Received: from mga02.intel.com ([134.134.136.20]:59666 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964921AbdKCBQd (ORCPT ); Thu, 2 Nov 2017 21:16:33 -0400 Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 02 Nov 2017 18:16:32 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.44,336,1505804400"; d="scan'208";a="1239053909" Received: from hz-desktop.sh.intel.com (HELO localhost) ([10.239.159.142]) by fmsmga002.fm.intel.com with ESMTP; 02 Nov 2017 18:16:29 -0700 From: Haozhong Zhang To: kvm@vger.kernel.org, x86@kernel.org Cc: linux-kernel@vger.kernel.org, Paolo Bonzini , rkrcmar@redhat.com, Xiao Guangrong , Dan Williams , ivan.d.cuevas.escareno@intel.com, karthik.kumar@intel.com, Konrad Rzeszutek Wilk , Olif Chapman , Haozhong Zhang , Ingo Molnar Subject: [PATCH v3 3/3] KVM: MMU: consider host cache mode in MMIO page check Date: Fri, 3 Nov 2017 09:16:20 +0800 Message-Id: <20171103011620.21380-4-haozhong.zhang@intel.com> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20171103011620.21380-1-haozhong.zhang@intel.com> References: <20171103011620.21380-1-haozhong.zhang@intel.com> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 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. Signed-off-by: Haozhong Zhang Reported-by: Cuevas Escareno, Ivan D Reported-by: Kumar, Karthik --- arch/x86/kvm/mmu.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 0b481cc9c725..058ff6442638 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -2708,7 +2708,23 @@ static bool mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn, static bool kvm_is_mmio_pfn(kvm_pfn_t pfn) { if (pfn_valid(pfn)) - return !is_zero_pfn(pfn) && PageReserved(pfn_to_page(pfn)); + return !is_zero_pfn(pfn) && PageReserved(pfn_to_page(pfn)) && + /* + * 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 in addition and + * only treat UC/UC- pages as MMIO. + * + * pat_pfn_is_uc() works only when PAT is enabled, + * so check pat_enabled() as well. + */ + (!pat_enabled() || pat_pfn_is_uc(kvm_pfn_to_pfn(pfn))); return true; }