Subject: [PATCH v4 17/21] powerpc/8xx: set PTE bit 22 off TLBmiss

From: Christophe Leroy <[email-masked]>
Date: Fri, 19 Sep 2014 10:36:09 +0200 (CEST)

No need to re-set this bit at each TLB miss. Let's set it in the PTE.

Signed-off-by: Christophe Leroy <[email-masked]>

---
Changes in v2:
- None

Changes in v3:
- Removed PPC405 related macro from PPC8xx specific code
- PTE_NONE_MASK doesn't need PAGE_ACCESSED in Linux 2.6

Changes in v4:
- None

 arch/powerpc/include/asm/pgtable-ppc32.h | 20 ++++++++++++++++++++
 arch/powerpc/include/asm/pte-8xx.h       |  7 +++++--
 arch/powerpc/kernel/head_8xx.S           | 10 ++--------
 3 files changed, 27 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/include/asm/pgtable-ppc32.h b/arch/powerpc/include/asm/pgtable-ppc32.h
index 47edde8..35a9b44 100644
--- a/arch/powerpc/include/asm/pgtable-ppc32.h
+++ b/arch/powerpc/include/asm/pgtable-ppc32.h
@@ -172,6 +172,25 @@ static inline unsigned long pte_update(pte_t *p,
 #ifdef PTE_ATOMIC_UPDATES
 	unsigned long old, tmp;
 
+#ifdef CONFIG_PPC_8xx
+	unsigned long tmp2;
+
+	__asm__ __volatile__("\
+1:	lwarx	%0,0,%4\n\
+	andc	%1,%0,%5\n\
+	or	%1,%1,%6\n\
+	/* 0x200 == Extended encoding, bit 22 */ \
+	/* Bit 22 has to be 1 if neither _PAGE_USER nor _PAGE_RW are set */ \
+	rlwimi	%1,%1,32-2,0x200\n /* get _PAGE_USER */ \
+	rlwinm	%3,%1,32-1,0x200\n /* get _PAGE_RW */ \
+	or	%1,%3,%1\n\
+	xori	%1,%1,0x200\n"
+"	stwcx.	%1,0,%4\n\
+	bne-	1b"
+	: "=&r" (old), "=&r" (tmp), "=m" (*p), "=&r" (tmp2)
+	: "r" (p), "r" (clr), "r" (set), "m" (*p)
+	: "cc" );
+#else /* CONFIG_PPC_8xx */
 	__asm__ __volatile__("\
 1:	lwarx	%0,0,%3\n\
 	andc	%1,%0,%4\n\
@@ -182,6 +201,7 @@ static inline unsigned long pte_update(pte_t *p,
 	: "=&r" (old), "=&r" (tmp), "=m" (*p)
 	: "r" (p), "r" (clr), "r" (set), "m" (*p)
 	: "cc" );
+#endif /* CONFIG_PPC_8xx */
 #else /* PTE_ATOMIC_UPDATES */
 	unsigned long old = pte_val(*p);
 	*p = __pte((old & ~clr) | set);
diff --git a/arch/powerpc/include/asm/pte-8xx.h b/arch/powerpc/include/asm/pte-8xx.h
index d44826e..daa4616 100644
--- a/arch/powerpc/include/asm/pte-8xx.h
+++ b/arch/powerpc/include/asm/pte-8xx.h
@@ -48,19 +48,22 @@
  */
 #define _PAGE_RW	0x0400	/* lsb PP bits, inverted in HW */
 #define _PAGE_USER	0x0800	/* msb PP bits */
+/* set when neither _PAGE_USER nor _PAGE_RW are set */
+#define _PAGE_KNLRO	0x0200
 
 #define _PMD_PRESENT	0x0001
 #define _PMD_BAD	0x0ff0
 #define _PMD_PAGE_MASK	0x000c
 #define _PMD_PAGE_8M	0x000c
 
-#define _PTE_NONE_MASK _PAGE_ACCESSED
+#define _PTE_NONE_MASK _PAGE_KNLRO
 
 /* Until my rework is finished, 8xx still needs atomic PTE updates */
 #define PTE_ATOMIC_UPDATES	1
 
 /* We need to add _PAGE_SHARED to kernel pages */
-#define _PAGE_KERNEL_RO	(_PAGE_SHARED)
+#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)
 
 #endif /* __KERNEL__ */
diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index a7af26e..48d3de8 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -445,14 +445,8 @@ DataStoreTLBMiss:
 	and	r11, r11, r10
 	rlwimi	r10, r11, 0, _PAGE_PRESENT
 #endif
-	/* Honour kernel RO, User NA */
-	/* 0x200 == Extended encoding, bit 22 */
-	rlwimi	r10, r10, 32-2, 0x200 /* Copy USER to bit 22, 0x200 */
-	/* r11 =  (r10 & _PAGE_RW) >> 1 */
-	rlwinm	r11, r10, 32-1, 0x200
-	or	r10, r11, r10
-	/* invert RW and 0x200 bits */
-	xori	r10, r10, _PAGE_RW | 0x200
+	/* 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.
-- 
2.1.0