powerpc/8xx: Use L1 entry APG to handle _PAGE_ACCESSED for CONFIG_SWAP

When CONFIG_SWAP is set, the TLB miss handlers have to also take
into account _PAGE_ACCESSED flag. At the moment it is done by
anding _PAGE_ACCESSED into _PAGE_PRESENT using 3 instructions.

This patch uses APG for handling _PAGE_ACCESSED, allowing to
just copy _PAGE_ACCESSED bit into APG field, hence reducing the
action to a single instruction.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 28 insertions, 6 deletions

diff --git a/arch/powerpc/include/asm/mmu-8xx.h b/arch/powerpc/include/asm/mmu-8xx.h
index a568ff5c5fb8..2f806e329648 100644
--- a/arch/powerpc/include/asm/mmu-8xx.h
+++ b/arch/powerpc/include/asm/mmu-8xx.h
@@ -34,12 +34,20 @@
  * respectively NA for All or X for Supervisor and no access for User.
  * Then we use the APG to say whether accesses are according to Page rules or
  * "all Supervisor" rules (Access to all)
- * Therefore, we define 2 APG groups. lsb is _PMD_USER
- * 0 => No user => 01 (all accesses performed according to page definition)
- * 1 => User => 00 (all accesses performed as supervisor iaw page definition)
+ * We also use the 2nd APG bit for _PAGE_ACCESSED when having SWAP:
+ * When that bit is not set access is done iaw "all user"
+ * which means no access iaw page rules.
+ * Therefore, we define 4 APG groups. lsb is _PMD_USER, 2nd is _PAGE_ACCESSED
+ * 0x => No access => 11 (all accesses performed as user iaw page definition)
+ * 10 => No user => 01 (all accesses performed according to page definition)
+ * 11 => User => 00 (all accesses performed as supervisor iaw page definition)
  * We define all 16 groups so that all other bits of APG can take any value
  */
+#ifdef CONFIG_SWAP
+#define MI_APG_INIT	0xf4f4f4f4
+#else
 #define MI_APG_INIT	0x44444444
+#endif
 
 /* The effective page number register.  When read, contains the information
  * about the last instruction TLB miss.  When MI_RPN is written, bits in
@@ -107,12 +115,20 @@
  * Supervisor and no access for user and NA for ALL.
  * Then we use the APG to say whether accesses are according to Page rules or
  * "all Supervisor" rules (Access to all)
- * Therefore, we define 2 APG groups. lsb is _PMD_USER
- * 0 => No user => 01 (all accesses performed according to page definition)
- * 1 => User => 00 (all accesses performed as supervisor iaw page definition)
+ * We also use the 2nd APG bit for _PAGE_ACCESSED when having SWAP:
+ * When that bit is not set access is done iaw "all user"
+ * which means no access iaw page rules.
+ * Therefore, we define 4 APG groups. lsb is _PMD_USER, 2nd is _PAGE_ACCESSED
+ * 0x => No access => 11 (all accesses performed as user iaw page definition)
+ * 10 => No user => 01 (all accesses performed according to page definition)
+ * 11 => User => 00 (all accesses performed as supervisor iaw page definition)
  * We define all 16 groups so that all other bits of APG can take any value
  */
+#ifdef CONFIG_SWAP
+#define MD_APG_INIT	0xf4f4f4f4
+#else
 #define MD_APG_INIT	0x44444444
+#endif
 
 /* The effective page number register.  When read, contains the information
  * about the last instruction TLB miss.  When MD_RPN is written, bits in
@@ -164,6 +180,12 @@
  */
 #define SPRN_M_TW	799
 
+/* APGs */
+#define M_APG0		0x00000000
+#define M_APG1		0x00000020
+#define M_APG2		0x00000040
+#define M_APG3		0x00000060
+
 #ifndef __ASSEMBLY__
 typedef struct {
 	unsigned int id;