From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932477AbdJ0C0Y (ORCPT ); Thu, 26 Oct 2017 22:26:24 -0400 Received: from mga04.intel.com ([192.55.52.120]:2310 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932452AbdJ0C0T (ORCPT ); Thu, 26 Oct 2017 22:26:19 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.44,303,1505804400"; d="scan'208";a="914265577" 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 3/3] KVM: MMU: consider host cache type in MMIO pfn check Date: Fri, 27 Oct 2017 10:25:24 +0800 Message-Id: <20171027022524.22589-4-haozhong.zhang@intel.com> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20171027022524.22589-1-haozhong.zhang@intel.com> References: <20171027022524.22589-1-haozhong.zhang@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org By default, KVM treats a reserved page as for MMIO purpose, and maps it to guest with UC memory type. However, some reserved pages are not for MMIO, such as pages of DAX device (e.g., /dev/daxX.Y). Mapping them with UC memory type will harm the performance. In order to exclude those cases, we check the host cache mode 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 | 32 +++++++++++++++++++++++++++++--- 1 file changed, 29 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 0b481cc9c725..d4c821a6df3d 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -2707,10 +2707,36 @@ 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)); + + /* + * By default, KVM treats a reserved page as for MMIO + * purpose, and maps it to guest with UC memory type. + * However, some reserved pages are not for MMIO, such + * as pages of DAX device (e.g., /dev/daxX.Y). Mapping + * them with UC memory type will harm the performance. + * In order to exclude those cases, we check the host + * cache mode in addition and only treat UC/UC- pages + * as MMIO. + * + * track_pfn_insert() works only when PAT is enabled, + * so add pat_enabled() here. + */ + if (is_mmio && pat_enabled()) { + pgprot_t prot; + enum page_cache_mode cm; + + track_pfn_insert(NULL, &prot, kvm_pfn_to_pfn(pfn)); + cm = pgprot2cachemode(prot); + 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, -- 2.14.1