diff --git a/mm/frame_vector.c b/mm/frame_vector.c
index 0e589a9a8801..1cd81d38ad2d 100644
--- a/mm/frame_vector.c
+++ b/mm/frame_vector.c
@@ -29,6 +29,10 @@
  * different type underlying the specified range of virtual addresses.
  * When the function isn't able to map a single page, it returns error.
  *
+ * Note that get_vaddr_frames() cannot follow VM_IO mappings. It used
+ * to be able to do that, but that could (racily) return non-refcounted
+ * pfns.
+ *
  * This function takes care of grabbing mmap_lock as necessary.
  */
 int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
@@ -77,8 +81,6 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
 			goto out;
 	}
 
-	/* This used to (racily) return non-refcounted pfns. Let people know */
-	WARN_ONCE(1, "get_vaddr_frames() cannot follow VM_IO mapping");
 	vec->nr_frames = 0;
 
 out: