linux-kernel - [PATCH 2/7] powerpc/8xx: Only define APG0 and APG1

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Message-Id: <cb7f191cc86960bfd26567c045ed59761ab423ca.1551820475.git.christophe.leroy@c-s.fr>
Date:   Tue,  5 Mar 2019 21:18:15 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>, ruscur@...sell.cc
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH 2/7] powerpc/8xx: Only define APG0 and APG1

Since the 8xx implements hardware page table walk assistance,
the PGD entries always point to a 4k aligned page, so the 2 upper
bit of the APG are not clobbered anymore and remain 0. Therefore
only APG0 and APG1 are used and need a definition. We set the
other APG to the lowest permission level.

Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
 arch/powerpc/include/asm/nohash/32/mmu-8xx.h | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/include/asm/nohash/32/mmu-8xx.h b/arch/powerpc/include/asm/nohash/32/mmu-8xx.h
index 0a1a3fc54e54..fc5a653d5dd2 100644
--- a/arch/powerpc/include/asm/nohash/32/mmu-8xx.h
+++ b/arch/powerpc/include/asm/nohash/32/mmu-8xx.h
@@ -35,11 +35,11 @@
  * 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)
+ * 0 => Kernel => 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
+ * 2-16 => NA => 11 (all accesses performed as user iaw page definition)
  */
-#define MI_APG_INIT	0x44444444
+#define MI_APG_INIT	0x4fffffff
 
 /* The effective page number register.  When read, contains the information
  * about the last instruction TLB miss.  When MI_RPN is written, bits in
@@ -108,11 +108,11 @@
  * 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)
+ * 0 => Kernel => 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
+ * 2-16 => NA => 11 (all accesses performed as user iaw page definition)
  */
-#define MD_APG_INIT	0x44444444
+#define MD_APG_INIT	0x4fffffff
 
 /* The effective page number register.  When read, contains the information
  * about the last instruction TLB miss.  When MD_RPN is written, bits in
-- 
2.13.3