[PATCH] KVM: MMU: Treat user-mode faults as a hint that a page is no longer a page table

Signed-off-by: Avi Kivity <avi@qumranet.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/kvm/paging_tmpl.h

@@ -271,6 +271,7 @@ static int FNAME(fix_write_pf)(struct kvm_vcpu *vcpu,
 	pt_element_t *guest_ent;
 	int writable_shadow;
 	gfn_t gfn;
+	struct kvm_mmu_page *page;
 
 	if (is_writeble_pte(*shadow_ent))
 		return 0;
@@ -303,7 +304,17 @@ static int FNAME(fix_write_pf)(struct kvm_vcpu *vcpu,
 	}
 
 	gfn = walker->gfn;
-	if (kvm_mmu_lookup_page(vcpu, gfn)) {
+
+	if (user) {
+		/*
+		 * Usermode page faults won't be for page table updates.
+		 */
+		while ((page = kvm_mmu_lookup_page(vcpu, gfn)) != NULL) {
+			pgprintk("%s: zap %lx %x\n",
+				 __FUNCTION__, gfn, page->role.word);
+			kvm_mmu_zap_page(vcpu, page);
+		}
+	} else if (kvm_mmu_lookup_page(vcpu, gfn)) {
 		pgprintk("%s: found shadow page for %lx, marking ro\n",
 			 __FUNCTION__, gfn);
 		*write_pt = 1;