KVM: Move guest pte dirty bit management to the guest pagetable walker

This is more consistent with the accessed bit management, and makes the dirty
bit available earlier for other purposes.
Signed-off-by: Avi Kivity <avi@qumranet.com>

drivers/kvm/mmu.c

@@ -199,6 +199,11 @@ static int is_writeble_pte(unsigned long pte)
 	return pte & PT_WRITABLE_MASK;
 }
 
+static int is_dirty_pte(unsigned long pte)
+{
+	return pte & PT_DIRTY_MASK;
+}
+
 static int is_io_pte(unsigned long pte)
 {
 	return pte & PT_SHADOW_IO_MARK;

drivers/kvm/paging_tmpl.h

@@ -144,6 +144,10 @@ static int FNAME(walk_addr)(struct guest_walker *walker,
 		if (walker->level == PT_PAGE_TABLE_LEVEL) {
 			walker->gfn = (*ptep & PT_BASE_ADDR_MASK)
 				>> PAGE_SHIFT;
+			if (write_fault && !is_dirty_pte(*ptep)) {
+				mark_page_dirty(vcpu->kvm, table_gfn);
+				*ptep |= PT_DIRTY_MASK;
+			}
 			break;
 		}
 
@@ -153,6 +157,10 @@ static int FNAME(walk_addr)(struct guest_walker *walker,
 			walker->gfn = (*ptep & PT_DIR_BASE_ADDR_MASK)
 				>> PAGE_SHIFT;
 			walker->gfn += PT_INDEX(addr, PT_PAGE_TABLE_LEVEL);
+			if (write_fault && !is_dirty_pte(*ptep)) {
+				mark_page_dirty(vcpu->kvm, table_gfn);
+				*ptep |= PT_DIRTY_MASK;
+			}
 			break;
 		}
 
@@ -194,12 +202,6 @@ err:
 	return 0;
 }
 
-static void FNAME(mark_pagetable_dirty)(struct kvm *kvm,
-					struct guest_walker *walker)
-{
-	mark_page_dirty(kvm, walker->table_gfn[walker->level - 1]);
-}
-
 static void FNAME(set_pte_common)(struct kvm_vcpu *vcpu,
 				  u64 *shadow_pte,
 				  gpa_t gaddr,
@@ -221,23 +223,6 @@ static void FNAME(set_pte_common)(struct kvm_vcpu *vcpu,
 		 __FUNCTION__, *shadow_pte, (u64)gpte, access_bits,
 		 write_fault, user_fault, gfn);
 
-	if (write_fault && !dirty) {
-		pt_element_t *guest_ent, *tmp = NULL;
-
-		if (walker->ptep)
-			guest_ent = walker->ptep;
-		else {
-			tmp = kmap_atomic(walker->page, KM_USER0);
-			guest_ent = &tmp[walker->index];
-		}
-
-		*guest_ent |= PT_DIRTY_MASK;
-		if (!walker->ptep)
-			kunmap_atomic(tmp, KM_USER0);
-		dirty = 1;
-		FNAME(mark_pagetable_dirty)(vcpu->kvm, walker);
-	}
-
 	/*
 	 * We don't set the accessed bit, since we sometimes want to see
 	 * whether the guest actually used the pte (in order to detect