diff --git a/include/asm-ia64/pal.h b/include/asm-ia64/pal.h
index 37e52a2..20a8d61 100644
--- a/include/asm-ia64/pal.h
+++ b/include/asm-ia64/pal.h
@@ -1433,7 +1433,12 @@
 } pal_version_u_t;
 
 
-/* Return PAL version information */
+/*
+ * Return PAL version information.  While the documentation states that
+ * PAL_VERSION can be called in either physical or virtual mode, some
+ * implementations only allow physical calls.  We don't call it very often,
+ * so the overhead isn't worth eliminating.
+ */
 static inline s64
 ia64_pal_version (pal_version_u_t *pal_min_version, pal_version_u_t *pal_cur_version)
 {