[v2 PATCH 2/2] powerpc/8xx: use _PAGE_RO instead of _PAGE_RW

On powerpc 8xx, in TLB entries, 0x400 bit is set to 1 for read-only pages
and is set to 0 for RW pages. So we should use _PAGE_RO instead of _PAGE_RW

Signed-off-by: Christophe Leroy <redacted>

---
v2 is a complete rework compared to v1

 arch/powerpc/include/asm/pte-8xx.h | 7 +++----
 arch/powerpc/kernel/head_8xx.S     | 3 ---
 2 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/include/asm/pte-8xx.h b/arch/powerpc/include/asm/pte-8xx.h
index daa4616..4f5583e 100644
--- a/arch/powerpc/include/asm/pte-8xx.h
+++ b/arch/powerpc/include/asm/pte-8xx.h

@@ -46,7 +46,7 @@
  * require a TLB exception handler change.  It is assumed unused bits
  * are always zero.
  */
-#define _PAGE_RW	0x0400	/* lsb PP bits, inverted in HW */
+#define _PAGE_RO	0x0400	/* lsb PP bits */
 #define _PAGE_USER	0x0800	/* msb PP bits */
 /* set when neither _PAGE_USER nor _PAGE_RW are set */
 #define _PAGE_KNLRO	0x0200

@@ -62,9 +62,8 @@
 #define PTE_ATOMIC_UPDATES	1
 
 /* We need to add _PAGE_SHARED to kernel pages */
-#define _PAGE_KERNEL_RO	(_PAGE_SHARED | _PAGE_KNLRO)
-#define _PAGE_KERNEL_ROX	(_PAGE_EXEC | _PAGE_KNLRO)
-#define _PAGE_KERNEL_RW	(_PAGE_DIRTY | _PAGE_RW | _PAGE_HWWRITE)
+#define _PAGE_KERNEL_RO	(_PAGE_SHARED | _PAGE_RO | _PAGE_KNLRO)
+#define _PAGE_KERNEL_ROX	(_PAGE_EXEC | _PAGE_RO | _PAGE_KNLRO)
 
 #endif /* __KERNEL__ */
 #endif /*  _ASM_POWERPC_PTE_8xx_H */

diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 3d4b8ee..807b0db 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S

@@ -441,9 +441,6 @@ DataStoreTLBMiss:
 	and	r11, r11, r10
 	rlwimi	r10, r11, 0, _PAGE_PRESENT
 #endif
-	/* invert RW */
-	xori	r10, r10, _PAGE_RW
-
 	/* The Linux PTE won't go exactly into the MMU TLB.
 	 * Software indicator bits 22 and 28 must be clear.
 	 * Software indicator bits 24, 25, 26, and 27 must be

-- 
2.1.0

On Wed, 2014-12-17 at 10:14 +0100, Christophe Leroy wrote:

It looks like pte_update() needs to be updated to match.

 #define _PAGE_USER	0x0800	/* msb PP bits */
 /* set when neither _PAGE_USER nor _PAGE_RW are set */

Also update this comment.

Where did _PAGE_KERNEL_RW go?

-Scott

Le 18/12/2014 03:22, Scott Wood a écrit :

On Wed, 2014-12-17 at 10:14 +0100, Christophe Leroy wrote:

quoted

On powerpc 8xx, in TLB entries, 0x400 bit is set to 1 for read-only pages
and is set to 0 for RW pages. So we should use _PAGE_RO instead of _PAGE_RW

Signed-off-by: Christophe Leroy <redacted>

---
v2 is a complete rework compared to v1

  arch/powerpc/include/asm/pte-8xx.h | 7 +++----
  arch/powerpc/kernel/head_8xx.S     | 3 ---
  2 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/include/asm/pte-8xx.h b/arch/powerpc/include/asm/pte-8xx.h
index daa4616..4f5583e 100644
--- a/arch/powerpc/include/asm/pte-8xx.h
+++ b/arch/powerpc/include/asm/pte-8xx.h

@@ -46,7 +46,7 @@
   * require a TLB exception handler change.  It is assumed unused bits
   * are always zero.
   */
-#define _PAGE_RW	0x0400	/* lsb PP bits, inverted in HW */
+#define _PAGE_RO	0x0400	/* lsb PP bits */

It looks like pte_update() needs to be updated to match.

quoted

  #define _PAGE_USER	0x0800	/* msb PP bits */
  /* set when neither _PAGE_USER nor _PAGE_RW are set */

Also update this comment.

quoted

  #define _PAGE_KNLRO	0x0200

@@ -62,9 +62,8 @@
  #define PTE_ATOMIC_UPDATES	1
  
  /* We need to add _PAGE_SHARED to kernel pages */
-#define _PAGE_KERNEL_RO	(_PAGE_SHARED | _PAGE_KNLRO)
-#define _PAGE_KERNEL_ROX	(_PAGE_EXEC | _PAGE_KNLRO)
-#define _PAGE_KERNEL_RW	(_PAGE_DIRTY | _PAGE_RW | _PAGE_HWWRITE)
+#define _PAGE_KERNEL_RO	(_PAGE_SHARED | _PAGE_RO | _PAGE_KNLRO)
+#define _PAGE_KERNEL_ROX	(_PAGE_EXEC | _PAGE_RO | _PAGE_KNLRO)
  
  #endif /* __KERNEL__ */
  #endif /*  _ASM_POWERPC_PTE_8xx_H */

Where did _PAGE_KERNEL_RW go?

It is already defined like this in pte-common.h:

#ifndef _PAGE_KERNEL_RW
#define _PAGE_KERNEL_RW        (_PAGE_DIRTY | _PAGE_RW | _PAGE_HWWRITE)
#endif


Christophe