Update the TLB asm to make proper use of _PAGE_DIRY and _PAGE_ACCESSED.
Pros:
- I/D TLB Miss never needs to write to the linux pte.
- _PAGE_ACCESSED is only set on TLB Error fixing accounting
- _PAGE_DIRTY is mapped to 0x100, the changed bit, and is set directly
when a page has been made dirty.
- Proper RO/RW mapping of user space.
- Free up 2 SW TLB bits in the linux pte(add back _PAGE_WRITETHRU ?)
Cons:
- 1 more instructions in I/D TLB Miss, but the since the linux pte is
not written anymore, it should still be a big win.
---
arch/powerpc/include/asm/pte-8xx.h | 13 +++---
arch/powerpc/kernel/head_8xx.S | 82 ++++++++++++++++--------------------
2 files changed, 43 insertions(+), 52 deletions(-)
diff --git a/arch/powerpc/include/asm/pte-8xx.h
b/arch/powerpc/include/asm/pte-8xx.h
index 8c6e312..f23cd15 100644
--- a/arch/powerpc/include/asm/pte-8xx.h
+++ b/arch/powerpc/include/asm/pte-8xx.h
@@ -32,22 +32,21 @@
#define _PAGE_FILE 0x0002 /* when !present: nonlinear file mapping */
#define _PAGE_NO_CACHE 0x0002 /* I: cache inhibit */
#define _PAGE_SHARED 0x0004 /* No ASID (context) compare */
+#define _PAGE_DIRTY 0x0100 /* C: page changed */
-/* These five software bits must be masked out when the entry is loaded
- * into the TLB.
+/* These 3 software bits must be masked out when the entry is loaded
+ * into the TLB, 2 SW bits left.
*/
#define _PAGE_EXEC 0x0008 /* software: i-cache coherency required */
#define _PAGE_GUARDED 0x0010 /* software: guarded access */
-#define _PAGE_DIRTY 0x0020 /* software: page changed */
-#define _PAGE_RW 0x0040 /* software: user write access allowed */
-#define _PAGE_ACCESSED 0x0080 /* software: page referenced */
+#define _PAGE_ACCESSED 0x0020 /* software: page referenced */
/* Setting any bits in the nibble with the follow two controls will
* require a TLB exception handler change. It is assumed unused bits
* are always zero.
*/
-#define _PAGE_HWWRITE 0x0100 /* h/w write enable: never set in Linux PTE */
-#define _PAGE_USER 0x0800 /* One of the PP bits, the other is USER&~RW */
+#define _PAGE_RW 0x0400 /* lsb PP bits, inverted in HW */
+#define _PAGE_USER 0x0800 /* msb PP bits */
#define _PMD_PRESENT 0x0001
#define _PMD_BAD 0x0ff0
diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 118bb05..3cf1289 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -333,26 +333,18 @@ InstructionTLBMiss:
mfspr r11, SPRN_MD_TWC /* ....and get the pte address */
lwz r10, 0(r11) /* Get the pte */
-#ifdef CONFIG_SWAP
- /* do not set the _PAGE_ACCESSED bit of a non-present page */
- andi. r11, r10, _PAGE_PRESENT
- beq 4f
- ori r10, r10, _PAGE_ACCESSED
- mfspr r11, SPRN_MD_TWC /* get the pte address again */
- stw r10, 0(r11)
-4:
-#else
- ori r10, r10, _PAGE_ACCESSED
- stw r10, 0(r11)
-#endif
+ andi. r11, r10, _PAGE_USER | _PAGE_ACCESSED
+ cmpwi cr0, r11, _PAGE_USER | _PAGE_ACCESSED
+ bne- cr0, 2f
+ /* Dont' bother with PP lsb, bit 21 for now */
/* The Linux PTE won't go exactly into the MMU TLB.
- * Software indicator bits 21, 22 and 28 must be clear.
+ * Software indicator bits 22 and 28 must be clear.
* Software indicator bits 24, 25, 26, and 27 must be
* set. All other Linux PTE bits control the behavior
* of the MMU.
*/
-2: li r11, 0x00f0
+ li r11, 0x00f0
rlwimi r10, r11, 0, 24, 28 /* Set 24-27, clear 28 */
DO_8xx_CPU6(0x2d80, r3)
mtspr SPRN_MI_RPN, r10 /* Update TLB entry */
@@ -365,6 +357,19 @@ InstructionTLBMiss:
lwz r3, 8(r0)
#endif
rfi
+2:
+ mfspr r11, SRR1
+ rlwinm r11, r11, 0, 5, 3 /* clear guarded */
+ mtspr SRR1, r11
+
+ mfspr r10, SPRN_M_TW /* Restore registers */
+ lwz r11, 0(r0)
+ mtcr r11
+ lwz r11, 4(r0)
+#ifdef CONFIG_8xx_CPU6
+ lwz r3, 8(r0)
+#endif
+ b InstructionAccess
. = 0x1200
DataStoreTLBMiss:
@@ -409,21 +414,14 @@ DataStoreTLBMiss:
DO_8xx_CPU6(0x3b80, r3)
mtspr SPRN_MD_TWC, r11
-#ifdef CONFIG_SWAP
- /* do not set the _PAGE_ACCESSED bit of a non-present page */
- andi. r11, r10, _PAGE_PRESENT
- beq 4f
- ori r10, r10, _PAGE_ACCESSED
-4:
- /* and update pte in table */
-#else
- ori r10, r10, _PAGE_ACCESSED
-#endif
- mfspr r11, SPRN_MD_TWC /* get the pte address again */
- stw r10, 0(r11)
+ andi. r11, r10, _PAGE_ACCESSED
+ bne+ cr0, 5f /* branch if access allowed */
+ rlwinm r10, r10, 0, 21, 19 /* Clear _PAGE_USER */
+ ori r10, r10, _PAGE_RW /* Set RW bit for xor below to clear it */
+5: xori r10, r10, _PAGE_RW /* invert RW bit */
/* The Linux PTE won't go exactly into the MMU TLB.
- * Software indicator bits 21, 22 and 28 must be clear.
+ * Software indicator bits 22 and 28 must be clear.
* Software indicator bits 24, 25, 26, and 27 must be
* set. All other Linux PTE bits control the behavior
* of the MMU.
@@ -472,8 +470,8 @@ DataTLBError:
/* First, make sure this was a store operation.
*/
mfspr r10, SPRN_DSISR
- andis. r11, r10, 0x4800 /* no translation, no permission. */
- bne 2f /* branch if either is set */
+ andis. r11, r10, 0x4000 /* no translation */
+ bne 2f /* branch if set */
/* The EA of a data TLB miss is automatically stored in the MD_EPN
* register. The EA of a data TLB error is automatically stored in
@@ -522,26 +520,20 @@ DataTLBError:
mfspr r11, SPRN_MD_TWC /* ....and get the pte address
*/
lwz r10, 0(r11) /* Get the pte */
- andi. r11, r10, _PAGE_RW /* Is it writeable? */
- beq 2f /* Bail out if not */
-
- /* Update 'changed', among others.
- */
-#ifdef CONFIG_SWAP
+ mfspr r11, DSISR
+ andis. r11, r11, 0x0200 /* store */
+ beq 5f
+ andi. r11, r10, _PAGE_RW /* writeable? */
+ beq 2f /* nope */
ori r10, r10, _PAGE_DIRTY|_PAGE_HWWRITE
- /* do not set the _PAGE_ACCESSED bit of a non-present page */
- andi. r11, r10, _PAGE_PRESENT
- beq 4f
- ori r10, r10, _PAGE_ACCESSED
-4:
-#else
- ori r10, r10, _PAGE_DIRTY|_PAGE_ACCESSED|_PAGE_HWWRITE
-#endif
- mfspr r11, SPRN_MD_TWC /* Get pte address again */
+5: ori r10, r10, _PAGE_ACCESSED
+ mfspr r11, MD_TWC /* Get pte address again */
stw r10, 0(r11) /* and update pte in table */
+ xori r10, r10, _PAGE_RW /* RW bit is inverted */
+
/* The Linux PTE won't go exactly into the MMU TLB.
- * Software indicator bits 21, 22 and 28 must be clear.
+ * Software indicator bits 22 and 28 must be clear.
* Software indicator bits 24, 25, 26, and 27 must be
* set. All other Linux PTE bits control the behavior
* of the MMU.
--
1.6.4.4
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