x86: pgtable, document pde bits

Some of pde bits weren't documented, add the short description to them.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/include/asm-x86/pgtable.h b/include/asm-x86/pgtable.h
index 2ce76507046467a78e8d3b737d4e00cd7f2a2133..f1d9f4a03f6fafc0dfe8de3634196f571608d6e4 100644 (file)
--- a/include/asm-x86/pgtable.h
+++ b/include/asm-x86/pgtable.h
@@ -4,13 +4,13 @@
 #define USER_PTRS_PER_PGD      ((TASK_SIZE-1)/PGDIR_SIZE+1)
 #define FIRST_USER_ADDRESS     0
 
-#define _PAGE_BIT_PRESENT      0
-#define _PAGE_BIT_RW           1
-#define _PAGE_BIT_USER         2
-#define _PAGE_BIT_PWT          3
-#define _PAGE_BIT_PCD          4
-#define _PAGE_BIT_ACCESSED     5
-#define _PAGE_BIT_DIRTY                6
+#define _PAGE_BIT_PRESENT      0       /* is present */
+#define _PAGE_BIT_RW           1       /* writeable */
+#define _PAGE_BIT_USER         2       /* userspace addressable */
+#define _PAGE_BIT_PWT          3       /* page write through */
+#define _PAGE_BIT_PCD          4       /* page cache disabled */
+#define _PAGE_BIT_ACCESSED     5       /* was accessed (raised by CPU) */
+#define _PAGE_BIT_DIRTY                6       /* was written to (raised by CPU) */
 #define _PAGE_BIT_FILE         6
 #define _PAGE_BIT_PSE          7       /* 4 MB (or 2MB) page */
 #define _PAGE_BIT_PAT          7       /* on 4KB pages */