[PATCH 05/15] 8xx: Update TLB asm so it behaves as linux mm expects.
Joakim Tjernlund
Joakim.Tjernlund at transmode.se
Tue Jun 14 23:54:50 EST 2011
Update the TLB asm to make proper use of _PAGE_DIRTY and _PAGE_ACCESSED.
Get rid of _PAGE_HWWRITE too.
Pros:
- PRESENT is copied to ACCESSED, fixing accounting
- 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 ?)
- kernel RO/user NA support. Not sure this is really needed, would save
a few insn if not required.
Cons:
- A few more instructions in the DTLB Miss routine.
Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund at transmode.se>
---
arch/ppc/kernel/head_8xx.S | 53 ++++++++++++++++++++++++++-----------------
include/asm-ppc/pgtable.h | 15 +++++------
2 files changed, 39 insertions(+), 29 deletions(-)
diff --git a/arch/ppc/kernel/head_8xx.S b/arch/ppc/kernel/head_8xx.S
index 9d8a1b5..c9770b6 100644
--- a/arch/ppc/kernel/head_8xx.S
+++ b/arch/ppc/kernel/head_8xx.S
@@ -369,25 +369,27 @@ InstructionTLBMiss:
*/
tophys(r21,r21)
ori r21,r21,1 /* Set valid bit */
- beq- 2f /* If zero, don't try to find a pte */
DO_8xx_CPU6(0x2b80, r3)
mtspr MI_TWC, r21 /* Set segment attributes */
+ beq- 2f /* If zero, don't try to find a pte */
DO_8xx_CPU6(0x3b80, r3)
mtspr MD_TWC, r21 /* Load pte table base address */
mfspr r21, MD_TWC /* ....and get the pte address */
lwz r20, 0(r21) /* Get the pte */
- ori r20, r20, _PAGE_ACCESSED
- stw r20, 0(r21)
-
+#if 1
+ /* if !swap, you can delete this */
+ rlwimi r20, r20, 5, _PAGE_PRESENT<<5 /* Copy PRESENT to ACCESSED */
+ stw r20, 0(r21) /* Update pte */
+#endif
/* The Linux PTE won't go exactly into the MMU TLB.
- * Software indicator bits 21, 22 and 28 must be clear.
+ * Software indicator bits 21 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 r21, 0x00f0
- rlwimi r20, r21, 0, 24, 28 /* Set 24-27, clear 28 */
+ rlwimi r20, r21, 0, 0x07f8 /* Set 24-27, clear 21-23,28 */
DO_8xx_CPU6(0x2d80, r3)
mtspr MI_RPN, r20 /* Update TLB entry */
@@ -444,12 +446,25 @@ DataStoreTLBMiss:
DO_8xx_CPU6(0x3b80, r3)
mtspr MD_TWC, r21
- mfspr r21, MD_TWC /* get the pte address again */
- ori r20, r20, _PAGE_ACCESSED
- stw r20, 0(r21)
+#if 1
+ /* if !swap, you can delete this */
+ mfspr r21, MD_TWC /* get the pte address */
+ rlwimi r20, r20, 5, _PAGE_PRESENT<<5 /* Copy PRESENT to ACCESSED */
+ stw r20, 0(r21) /* Update pte */
+#endif
+
+ /* Honour kernel RO, User NA */
+ /* 0x200 == Extended encoding, bit 22 */
+ /* r20 |= (r20 & _PAGE_USER) >> 2 */
+ rlwimi r20, r20, 32-2, 0x200
+ /* r21 = (r20 & _PAGE_RW) >> 1 */
+ rlwinm r21, r20, 32-1, 0x200
+ or r20, r21, r20
+ /* invert RW and 0x200 bits */
+ xori r20, r20, _PAGE_RW | 0x200
/* 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.
@@ -496,11 +511,12 @@ DataTLBError:
stw r20, 0(r0)
stw r21, 4(r0)
- /* First, make sure this was a store operation.
- */
mfspr r20, DSISR
- andis. r21, r20, 0x0200 /* If set, indicates store op */
- beq 2f
+ andis. r21, r20, 0x4800 /* !translation or protection */
+ bne- 2f
+ /* Only Change bit left now, do it here as it is faster
+ * than trapping to the C fault handler.
+ */
/* 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
@@ -550,17 +566,12 @@ DataTLBError:
mfspr r21, MD_TWC /* ....and get the pte address */
lwz r20, 0(r21) /* Get the pte */
- andi. r21, r20, _PAGE_RW /* Is it writeable? */
- beq 2f /* Bail out if not */
-
- /* Update 'changed', among others.
- */
ori r20, r20, _PAGE_DIRTY|_PAGE_ACCESSED|_PAGE_HWWRITE
- mfspr r21, MD_TWC /* Get pte address again */
stw r20, 0(r21) /* and update pte in table */
+ xori r20, r20, _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.
diff --git a/include/asm-ppc/pgtable.h b/include/asm-ppc/pgtable.h
index 71b2165..2ba37d3 100644
--- a/include/asm-ppc/pgtable.h
+++ b/include/asm-ppc/pgtable.h
@@ -298,21 +298,20 @@ extern unsigned long vmalloc_start;
#define _PAGE_NO_CACHE 0x0002 /* I: cache inhibit */
#define _PAGE_SHARED 0x0004 /* No ASID (context) compare */
-/* These five software bits must be masked out when the entry is loaded
- * into the TLB.
+/* These three software bits must be masked out when the entry is loaded
+ * into the TLB, 2 SW bits free.
*/
#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.
+ * are always zero, encoding(bit 22).
*/
-#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_DIRTY 0x0100 /* Changed: page changed */
+#define _PAGE_RW 0x0400 /* PP lsb(bit 21), user write access allowed */
+#define _PAGE_USER 0x0800 /* PP msb(bit 20), user access allowed */
#define _PMD_PRESENT PAGE_MASK
#define _PMD_PAGE_MASK 0x000c
--
1.7.3.4
More information about the Linuxppc-dev
mailing list