From patchwork Wed Nov 8 07:56:30 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Haozhong Zhang X-Patchwork-Id: 10047931 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 855146032D for ; Wed, 8 Nov 2017 07:58:14 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 778D62A4FB for ; Wed, 8 Nov 2017 07:58:14 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 6C3982A500; Wed, 8 Nov 2017 07:58:14 +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 232732A4FB for ; Wed, 8 Nov 2017 07:58:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751013AbdKHH6C (ORCPT ); Wed, 8 Nov 2017 02:58:02 -0500 Received: from mga01.intel.com ([192.55.52.88]:4953 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751049AbdKHH4u (ORCPT ); Wed, 8 Nov 2017 02:56:50 -0500 Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 07 Nov 2017 23:56:50 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.44,363,1505804400"; d="scan'208";a="1241320401" Received: from hz-desktop.sh.intel.com (HELO localhost) ([10.239.159.142]) by fmsmga002.fm.intel.com with ESMTP; 07 Nov 2017 23:56:47 -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 v5 2/2] KVM: MMU: consider host cache mode in MMIO page check Date: Wed, 8 Nov 2017 15:56:30 +0800 Message-Id: <20171108075630.16991-3-haozhong.zhang@intel.com> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20171108075630.16991-1-haozhong.zhang@intel.com> References: <20171108075630.16991-1-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- pages as MMIO. Signed-off-by: Haozhong Zhang Reported-by: Cuevas Escareno, Ivan D Reported-by: Kumar, Karthik --- arch/x86/kvm/mmu.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 0b481cc9c725..7715476bc5c9 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -2708,7 +2708,20 @@ 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_enabled() || pat_pfn_is_uc_or_uc_minus(pfn)); return true; }