diff --git a/include/kernel/vm-region.h b/include/kernel/vm-region.h
index c4585b7..3c08fef 100644
--- a/include/kernel/vm-region.h
+++ b/include/kernel/vm-region.h
@@ -6,7 +6,7 @@
 #include <kernel/vm.h>
 
 #define VM_REGION_NAME_MAX 64
-#define VM_REGION_COPY_ALL ((size_t)-1)
+#define VM_REGION_COPY_ALL ((size_t) - 1)
 
 struct vm_region;
 struct vm_object;
@@ -168,13 +168,14 @@ extern kern_status_t vm_region_memmove(
 extern kern_status_t vm_region_memmove_v(
 	struct vm_region *dest_region,
 	size_t dest_offset,
-	struct iovec *dest,
+	const struct iovec *dest,
 	size_t nr_dest,
 	struct vm_region *src_region,
 	size_t src_offset,
 	const struct iovec *src,
 	size_t nr_src,
-	size_t bytes_to_move);
+	size_t bytes_to_move,
+	size_t *nr_bytes_moved);
 
 DEFINE_OBJECT_LOCK_FUNCTION(vm_region, vr_base)
 
diff --git a/vm/vm-region.c b/vm/vm-region.c
index 98b3b0a..47ed246 100644
--- a/vm/vm-region.c
+++ b/vm/vm-region.c
@@ -1737,13 +1737,14 @@ kern_status_t vm_region_memmove(
 extern kern_status_t vm_region_memmove_v(
 	struct vm_region *dest_region,
 	size_t dest_offset,
-	struct iovec *dest_vecs,
+	const struct iovec *dest_vecs,
 	size_t nr_dest_vecs,
 	struct vm_region *src_region,
 	size_t src_offset,
 	const struct iovec *src_vecs,
 	size_t nr_src_vecs,
-	size_t bytes_to_move)
+	size_t bytes_to_move,
+	size_t *nr_bytes_moved)
 {
 	if (src_region->vr_status != VM_REGION_ONLINE) {
 		return KERN_BAD_STATE;
@@ -1760,6 +1761,7 @@ extern kern_status_t vm_region_memmove_v(
 	iovec_iterator_seek(&src, src_offset);
 	iovec_iterator_seek(&dest, dest_offset);
 
+	size_t moved = 0;
 	while (bytes_to_move && src.it_len && dest.it_len) {
 		size_t to_move
 			= MIN(MIN(src.it_len, dest.it_len), bytes_to_move);
@@ -1778,6 +1780,11 @@ extern kern_status_t vm_region_memmove_v(
 		iovec_iterator_seek(&src, to_move);
 		iovec_iterator_seek(&dest, to_move);
 		bytes_to_move -= to_move;
+		moved += to_move;
+	}
+
+	if (nr_bytes_moved) {
+		*nr_bytes_moved = moved;
 	}
 
 	return KERN_OK;