HVM-576 KVM: MMU: fix direct sp's access corrupted

1 files changed, 28 insertions, 2 deletions

diff --git a/kvm_paging_tmpl.h b/kvm_paging_tmpl.h
index 93bd9f9..308a007 100644
--- a/kvm_paging_tmpl.h
+++ b/kvm_paging_tmpl.h
@@ -316,8 +316,34 @@ static uint64_t *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
 			break;
 		}
 
-		if (is_shadow_present_pte(*sptep) && !is_large_pte(*sptep))
-			continue;
+		if (is_shadow_present_pte(*sptep) && !is_large_pte(*sptep)) {
+			struct kvm_mmu_page *child;
+			unsigned direct_access;
+
+			if (level != gw->level)
+				continue;
+
+			/*
+			 * For the direct sp, if the guest pte's dirty bit
+			 * changed form clean to dirty, it will corrupt the
+			 * sp's access: allow writable in the read-only sp,
+			 * so we should update the spte at this point to get
+			 * a new sp with the correct access.
+			 */
+			direct_access = gw->pt_access & gw->pte_access;
+			if (!is_dirty_gpte(gw->ptes[gw->level - 1]))
+				direct_access &= ~ACC_WRITE_MASK;
+
+			child = page_header(vcpu->kvm,
+			    *sptep & PT64_BASE_ADDR_MASK);
+
+			if (child->role.access == direct_access)
+				continue;
+
+			mmu_page_remove_parent_pte(child, sptep);
+			__set_spte(sptep, shadow_trap_nonpresent_pte);
+			kvm_flush_remote_tlbs(vcpu->kvm);
+		}
 
 		if (is_large_pte(*sptep)) {
 			rmap_remove(vcpu->kvm, sptep);