powerpc/8xx: Remove _PAGE_USER and handle user access at PMD level

As Linux kernel separates KERNEL and USER address spaces, there is
therefore no need to flag USER access at page level.

Today, the 8xx TLB handlers already handle user access in the L1 entry
through Access Protection Groups, it is then natural to move the user
access handling at PMD level once _PAGE_NA allows to handle PAGE_NONE
protection without _PAGE_USER

In the mean time, as we free up one bit in the PTE, we can use it to
include SPS (page size flag) in the PTE and avoid handling it at every
TLB miss hence removing special handling based on compiled page size.

For _PAGE_EXEC, we rework it to use PP PTE bits, avoiding the copy
of _PAGE_EXEC bit into the L1 entry. Unfortunatly we are not
able to put it at the correct location as it conflicts with
NA/RO/RW bits for data entries.

Upper bits of APG in L1 entry overlap with PMD base address. In
order to avoid having to filter that out, we set up all groups so that
upper bits can have any value.

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

1 files changed, 17 insertions, 17 deletions

diff --git a/arch/powerpc/include/asm/mmu-8xx.h b/arch/powerpc/include/asm/mmu-8xx.h
index 5bb3dbede41a..a568ff5c5fb8 100644
--- a/arch/powerpc/include/asm/mmu-8xx.h
+++ b/arch/powerpc/include/asm/mmu-8xx.h
@@ -29,17 +29,17 @@
 #define MI_Kp		0x40000000	/* Should always be set */
 
 /*
- * All pages' PP exec bits are set to 000, which means Execute for Supervisor
- * and no Execute for User.
- * Then we use the APG to say whether accesses are according to Page rules,
- * "all Supervisor" rules (Exec for all) and "all User" rules (Exec for noone)
- * Therefore, we define 4 APG groups. msb is _PAGE_EXEC, lsb is _PAGE_USER
- * 0 (00) => Not User, no exec => 11 (all accesses performed as user)
- * 1 (01) => User but no exec => 11 (all accesses performed as user)
- * 2 (10) => Not User, exec => 01 (rights according to page definition)
- * 3 (11) => User, exec => 00 (all accesses performed as supervisor)
- */
-#define MI_APG_INIT	0xf4ffffff
+ * All pages' PP data bits are set to either 001 or 011 by copying _PAGE_EXEC
+ * into bit 21 in the ITLBmiss handler (bit 21 is the middle bit), which means
+ * 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 define all 16 groups so that all other bits of APG can take any value
+ */
+#define MI_APG_INIT	0x44444444
 
 /* The effective page number register.  When read, contains the information
  * about the last instruction TLB miss.  When MI_RPN is written, bits in
@@ -102,17 +102,17 @@
 #define MD_Kp		0x40000000	/* Should always be set */
 
 /*
- * All pages' PP data bits are set to either 000 or 011, which means
+ * All pages' PP data bits are set to either 000 or 011 or 001, which means
  * respectively RW for Supervisor and no access for User, or RO for
- * Supervisor and no access for user.
+ * 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 _PAGE_USER
+ * 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
- *                                 according to page definition)
+ * 1 => 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
  */
-#define MD_APG_INIT	0x4fffffff
+#define MD_APG_INIT	0x44444444
 
 /* The effective page number register.  When read, contains the information
  * about the last instruction TLB miss.  When MD_RPN is written, bits in