From patchwork Wed Dec 20 07:29:29 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Haozhong Zhang X-Patchwork-Id: 10125149 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 26E9460388 for ; Wed, 20 Dec 2017 07:30:50 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3918F296A0 for ; Wed, 20 Dec 2017 07:30:50 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 2C5DD296CC; Wed, 20 Dec 2017 07:30:50 +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 B7BAF296A0 for ; Wed, 20 Dec 2017 07:30:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932245AbdLTHaB (ORCPT ); Wed, 20 Dec 2017 02:30:01 -0500 Received: from mga04.intel.com ([192.55.52.120]:40910 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754457AbdLTH36 (ORCPT ); Wed, 20 Dec 2017 02:29:58 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 19 Dec 2017 23:29:57 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.45,430,1508828400"; d="scan'208";a="17525249" Received: from hz-desktop.sh.intel.com (HELO localhost) ([10.239.159.142]) by orsmga001.jf.intel.com with ESMTP; 19 Dec 2017 23:29:55 -0800 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 , Mikulas Patocka , Haozhong Zhang , Ingo Molnar Subject: [PATCH v6 2/2] KVM: MMU: consider host cache mode in MMIO page check Date: Wed, 20 Dec 2017 15:29:29 +0800 Message-Id: <20171220072929.5200-3-haozhong.zhang@intel.com> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20171220072929.5200-1-haozhong.zhang@intel.com> References: <20171220072929.5200-1-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 in addition and only treat UC/UC-/WC pages as MMIO. Signed-off-by: Haozhong Zhang Reported-by: Cuevas Escareno, Ivan D Reported-by: Kumar, Karthik Reviewed-by: Xiao Guangrong --- arch/x86/kvm/mmu.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 89da688784fa..e3b9998b3355 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -2708,7 +2708,18 @@ 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, and results in KVM mapping them with UC + * memory type, which would hurt the performance. + * Therefore, we check the host memory type in addition + * and only treat UC/UC-/WC pages as MMIO. + */ + (!pat_enabled() || pat_immune_to_uc_mtrr(pfn)); return true; }