diff mbox series

[RFC,v7,35/78] KVM: x86: disable gpa_available optimization for fetch and page-walk NPF/EPT violations

Message ID 20200207181636.1065-36-alazar@bitdefender.com (mailing list archive)
State New, archived
Headers show
Series VM introspection | expand

Commit Message

Adalbert Lazăr Feb. 7, 2020, 6:15 p.m. UTC 
From: Mircea Cîrjaliu <mcirjaliu@bitdefender.com>

This change is needed because the introspection tool can write-protect
guest page tables, exec-protect heap/stack pages and let KVM emulate
the instruction that caused these violations.

Signed-off-by: Mircea Cîrjaliu <mcirjaliu@bitdefender.com>
Signed-off-by: Adalbert Lazăr <alazar@bitdefender.com>
---
 arch/x86/kvm/mmu/mmu.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)
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Patch

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 5f0ddc6b67de..d28b7425c4f1 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5636,8 +5636,13 @@  int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u64 error_code,
 	int r, emulation_type = 0;
 	bool direct = vcpu->arch.mmu->direct_map;
 
-	/* With shadow page tables, fault_address contains a GVA or nGPA.  */
-	if (vcpu->arch.mmu->direct_map) {
+	/*
+	 * With shadow page tables, fault_address contains a GVA or nGPA.
+	 * On a fetch fault, fault_address contains the instruction pointer.
+	 */
+	if (vcpu->arch.mmu->direct_map &&
+	    likely(!(error_code & PFERR_FETCH_MASK)) &&
+	    (error_code & PFERR_GUEST_FINAL_MASK)) {
 		vcpu->arch.gpa_available = true;
 		vcpu->arch.gpa_val = cr2;
 	}