Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752056AbbHEELF (ORCPT ); Wed, 5 Aug 2015 00:11:05 -0400 Received: from mga14.intel.com ([192.55.52.115]:45893 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751745AbbHEEKW (ORCPT ); Wed, 5 Aug 2015 00:10:22 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.15,613,1432623600"; d="scan'208";a="742410697" From: Xiao Guangrong To: pbonzini@redhat.com Cc: gleb@kernel.org, mtosatti@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, ru.pchel@gmail.com, Xiao Guangrong Subject: [PATCH v2 8/9] KVM: MMU: fully check zero bits for sptes Date: Wed, 5 Aug 2015 12:04:26 +0800 Message-Id: <1438747467-25425-9-git-send-email-guangrong.xiao@linux.intel.com> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1438747467-25425-1-git-send-email-guangrong.xiao@linux.intel.com> References: <1438747467-25425-1-git-send-email-guangrong.xiao@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2766 Lines: 93 The #PF with PFEC.RSV = 1 is designed to speed MMIO emulation, however, it is possible that the RSV #PF is caused by real BUG by mis-configure shadow page table entries This patch enables full check for the zero bits on shadow page table entries which include not only the reserved bit on hardware but also the bits spte never used, then dump the shadow page table hierarchy if the real bug is detected Signed-off-by: Xiao Guangrong --- arch/x86/kvm/mmu.c | 41 +++++++++++++++++++++++++++++++++++------ 1 file changed, 35 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index e6a7ed0..1393317 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -3295,31 +3295,60 @@ static bool quickly_check_mmio_pf(struct kvm_vcpu *vcpu, u64 addr, bool direct) return vcpu_match_mmio_gva(vcpu, addr); } -static u64 walk_shadow_page_get_mmio_spte(struct kvm_vcpu *vcpu, u64 addr) +/* return true if reserved bit is detected on spte. */ +static bool +walk_shadow_page_get_mmio_spte(struct kvm_vcpu *vcpu, u64 addr, u64 *sptep) { struct kvm_shadow_walk_iterator iterator; - u64 spte = 0ull; + u64 sptes[PT64_ROOT_LEVEL], spte = 0ull; + int root = 0, leaf; + bool reserved = false; if (!VALID_PAGE(vcpu->arch.mmu.root_hpa)) - return spte; + goto exit; walk_shadow_page_lockless_begin(vcpu); - for_each_shadow_entry_lockless(vcpu, addr, iterator, spte) + for_each_shadow_entry_lockless(vcpu, addr, iterator, spte) { + leaf = iterator.level; + + if (!root) + root = leaf; + + sptes[leaf - 1] = spte; + if (!is_shadow_present_pte(spte)) break; + + reserved |= is_shadow_zero_bits_set(&vcpu->arch.mmu, spte, + leaf); + } walk_shadow_page_lockless_end(vcpu); - return spte; + if (reserved) { + pr_err("%s: detect reserved bits on spte, addr 0x%llx, dump hierarchy:\n", + __func__, addr); + while (root >= leaf) { + pr_err("------ spte 0x%llx level %d.\n", + sptes[root - 1], root); + root--; + } + } +exit: + *sptep = spte; + return reserved; } int handle_mmio_page_fault_common(struct kvm_vcpu *vcpu, u64 addr, bool direct) { u64 spte; + bool reserved; if (quickly_check_mmio_pf(vcpu, addr, direct)) return RET_MMIO_PF_EMULATE; - spte = walk_shadow_page_get_mmio_spte(vcpu, addr); + reserved = walk_shadow_page_get_mmio_spte(vcpu, addr, &spte); + if (unlikely(reserved)) + return RET_MMIO_PF_BUG; if (is_mmio_spte(spte)) { gfn_t gfn = get_mmio_spte_gfn(spte); -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/