KVM: introduce kvm_for_each_memslot macro

Introduce kvm_for_each_memslot to walk all valid memslot

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index b5ed777..4c2900c 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -547,11 +547,11 @@
 
 void kvm_free_physmem(struct kvm *kvm)
 {
-	int i;
 	struct kvm_memslots *slots = kvm->memslots;
+	struct kvm_memory_slot *memslot;
 
-	for (i = 0; i < slots->nmemslots; ++i)
-		kvm_free_physmem_slot(&slots->memslots[i], NULL);
+	kvm_for_each_memslot(memslot, slots)
+		kvm_free_physmem_slot(memslot, NULL);
 
 	kfree(kvm->memslots);
 }
@@ -975,15 +975,13 @@
 static struct kvm_memory_slot *__gfn_to_memslot(struct kvm_memslots *slots,
 						gfn_t gfn)
 {
-	int i;
+	struct kvm_memory_slot *memslot;
 
-	for (i = 0; i < slots->nmemslots; ++i) {
-		struct kvm_memory_slot *memslot = &slots->memslots[i];
-
+	kvm_for_each_memslot(memslot, slots)
 		if (gfn >= memslot->base_gfn
 		    && gfn < memslot->base_gfn + memslot->npages)
 			return memslot;
-	}
+
 	return NULL;
 }