diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
index b0c0d1b45b99..628364b0f69f 100644
--- a/Documentation/filesystems/proc.rst
+++ b/Documentation/filesystems/proc.rst
@@ -549,6 +549,10 @@ does not take into account swapped out page of underlying shmem objects.
 naturally aligned THP pages of any currently enabled size. 1 if true, 0
 otherwise.
 
+If both the kernel and the CPU support protection keys (pkeys),
+"ProtectionKey" indicates the memory protection key associated with the
+virtual memory area.
+
 "VmFlags" field deserves a separate description. This member represents the
 kernel flags associated with the particular virtual memory area in two letter
 encoded manner. The codes are the following: