[v3,3/11] KVM: MMU: fix direct sp's access corruptted

Commit Message

Xiao Guangrong June 30, 2010, 8:03 a.m. UTC

None

Patch

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 28c8493..f28f09d 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -325,8 +325,32 @@  static u64 *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(*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);