From patchwork Tue Oct 31 11:48:40 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Haozhong Zhang X-Patchwork-Id: 10034343 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 E3C9C602B9 for ; Tue, 31 Oct 2017 11:52:56 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id DE31E285D2 for ; Tue, 31 Oct 2017 11:52:56 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id CE0B028A7A; Tue, 31 Oct 2017 11:52:56 +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 53EC9285D2 for ; Tue, 31 Oct 2017 11:52:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753118AbdJaLsj (ORCPT ); Tue, 31 Oct 2017 07:48:39 -0400 Received: from mga14.intel.com ([192.55.52.115]:15618 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753085AbdJaLsi (ORCPT ); Tue, 31 Oct 2017 07:48:38 -0400 Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 31 Oct 2017 04:48:37 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.44,323,1505804400"; d="scan'208";a="169982821" Received: from hz-desktop.sh.intel.com (HELO localhost) ([10.239.159.142]) by fmsmga006.fm.intel.com with ESMTP; 31 Oct 2017 04:48:34 -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, Haozhong Zhang Subject: [PATCH v2 2/2] KVM: MMU: consider host cache mode in MMIO page check Date: Tue, 31 Oct 2017 19:48:40 +0800 Message-Id: <20171031114840.12615-3-haozhong.zhang@intel.com> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20171031114840.12615-1-haozhong.zhang@intel.com> References: <20171031114840.12615-1-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 | 30 +++++++++++++++++++++++++++--- 1 file changed, 27 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 0b481cc9c725..206828d18857 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -2707,10 +2707,34 @@ 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)); + bool is_mmio = true; - return true; + if (pfn_valid(pfn)) { + is_mmio = !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 by lookup_memtype() in addition and + * only treat UC/UC- pages as MMIO. + * + * lookup_memtype() works only when PAT is enabled, so + * add pat_enabled() check here. + */ + if (is_mmio && pat_enabled()) { + enum page_cache_mode cm = lookup_memtype(PFN_PHYS(pfn)); + + is_mmio = (cm == _PAGE_CACHE_MODE_UC || + cm == _PAGE_CACHE_MODE_UC_MINUS); + } + } + + return is_mmio; } static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,