diff --git a/include/asm-x86/pgtable.h b/include/asm-x86/pgtable.h
index 55c3a0e3a8ce..b816134f753a 100644
--- a/include/asm-x86/pgtable.h
+++ b/include/asm-x86/pgtable.h
@@ -57,6 +57,7 @@
 #define _KERNPG_TABLE	(_PAGE_PRESENT | _PAGE_RW | _PAGE_ACCESSED |	\
 			 _PAGE_DIRTY)
 
+/* Set of bits not changed in pte_modify */
 #define _PAGE_CHG_MASK	(PTE_MASK | _PAGE_PCD | _PAGE_PWT |		\
 			 _PAGE_ACCESSED | _PAGE_DIRTY)