diff --git a/Documentation/mm/highmem.rst b/Documentation/mm/highmem.rst
index 34d7097d3ce8..71dc09563ff8 100644
--- a/Documentation/mm/highmem.rst
+++ b/Documentation/mm/highmem.rst
@@ -77,6 +77,13 @@ list shows them in order of preference of use.
   for pages which are known to not come from ZONE_HIGHMEM. However, it is
   always safe to use kmap_local_page() / kunmap_local().
 
+  While it is significantly faster than kmap(), for the higmem case it
+  comes with restrictions about the pointers validity. Contrary to kmap()
+  mappings, the local mappings are only valid in the context of the caller
+  and cannot be handed to other contexts. This implies that users must
+  be absolutely sure to keep the use of the return address local to the
+  thread which mapped it.
+
   Nesting kmap_local_page() and kmap_atomic() mappings is allowed to a certain
   extent (up to KMAP_TYPE_NR) but their invocations have to be strictly ordered
   because the map implementation is stack based. See kmap_local_page() kdocs