KVM: MMU: Add validate_direct_spte() helper

Add a helper to verify that a direct shadow page is valid wrt the required
access permissions; drop the page if it is not valid.

Reviewed-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 6 insertions, 21 deletions

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 0fb7068..0c7461d 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -338,30 +338,15 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
 			break;
 		}
 
-		if (is_shadow_present_pte(*sptep) && !is_large_pte(*sptep)) {
-			struct kvm_mmu_page *child;
-
-			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.
-			 */
-			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_shadow_present_pte(*sptep) && !is_large_pte(*sptep)
+		    && level == gw->level)
+			validate_direct_spte(vcpu, sptep, direct_access);
 
 		drop_large_spte(vcpu, sptep);
 
+		if (is_shadow_present_pte(*sptep))
+			continue;
+
 		if (level <= gw->level) {
 			direct = 1;
 			access = direct_access;