[PATCH 8/8] powerpc/8xx: Use L1 entry APG to handle _PAGE_ACCESSED for CONFIG_SWAP

From: Christophe Leroy
Date: Fri Jan 12 2018 - 07:45:51 EST

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When CONFIG_SWAP is set, the TLB miss handlers have to also take
into account _PAGE_ACCESSED flag. At the moment it is done by
anding _PAGE_ACCESSED into _PAGE_PRESENT using 3 instructions.

This patch uses APG for handling _PAGE_ACCESSED, allowing to
just copy _PAGE_ACCESSED bit into APG field, hence reducing the
action to a single instruction.

Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
---
arch/powerpc/include/asm/mmu-8xx.h | 34 +++++++++++++++++++++++-----
arch/powerpc/kernel/head_8xx.S | 45 +++++++++++++++-----------------------
arch/powerpc/mm/8xx_mmu.c | 2 +-
3 files changed, 47 insertions(+), 34 deletions(-)

diff --git a/arch/powerpc/include/asm/mmu-8xx.h b/arch/powerpc/include/asm/mmu-8xx.h
index ae68f6c848d3..ee5591fe6efc 100644
--- a/arch/powerpc/include/asm/mmu-8xx.h
+++ b/arch/powerpc/include/asm/mmu-8xx.h
@@ -34,12 +34,20 @@
* respectively NA for All or X for Supervisor and no access for User.
* 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)
- * 1 => User => 00 (all accesses performed as supervisor iaw page definition)
+ * We also use the 2nd APG bit for _PAGE_ACCESSED when having SWAP:
+ * When that bit is not set access is done iaw "all user"
+ * which means no access iaw page rules.
+ * Therefore, we define 4 APG groups. lsb is _PMD_USER, 2nd is _PAGE_ACCESSED
+ * 0x => No access => 11 (all accesses performed as user iaw page definition)
+ * 10 => No user => 01 (all accesses performed according to page definition)
+ * 11 => 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
*/
+#ifdef CONFIG_SWAP
+#define MI_APG_INIT 0xf4f4f4f4
+#else
#define MI_APG_INIT 0x44444444
+#endif

/* The effective page number register. When read, contains the information
* about the last instruction TLB miss. When MI_RPN is written, bits in
@@ -107,12 +115,20 @@
* Supervisor and no access for user and NA for ALL.
* 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)
- * 1 => User => 00 (all accesses performed as supervisor iaw page definition)
+ * We also use the 2nd APG bit for _PAGE_ACCESSED when having SWAP:
+ * When that bit is not set access is done iaw "all user"
+ * which means no access iaw page rules.
+ * Therefore, we define 4 APG groups. lsb is _PMD_USER, 2nd is _PAGE_ACCESSED
+ * 0x => No access => 11 (all accesses performed as user iaw page definition)
+ * 10 => No user => 01 (all accesses performed according to page definition)
+ * 11 => 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
*/
+#ifdef CONFIG_SWAP
+#define MD_APG_INIT 0xf4f4f4f4
+#else
#define MD_APG_INIT 0x44444444
+#endif

/* The effective page number register. When read, contains the information
* about the last instruction TLB miss. When MD_RPN is written, bits in
@@ -164,6 +180,12 @@
*/
#define SPRN_M_TW 799

+/* APGs */
+#define M_APG0 0x00000000
+#define M_APG1 0x00000020
+#define M_APG2 0x00000040
+#define M_APG3 0x00000060
+
#ifndef __ASSEMBLY__
typedef struct {
unsigned int id;
diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index c3b831bb8bad..d8670a37d70c 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -354,14 +354,13 @@ _ENTRY(ITLBMiss_cmp)
#if defined(ITLB_MISS_KERNEL) || defined(CONFIG_HUGETLB_PAGE)
mtcr r12
#endif
- /* Load the MI_TWC with the attributes for this "segment." */
- mtspr SPRN_MI_TWC, r11 /* Set segment attributes */

#ifdef CONFIG_SWAP
- rlwinm r11, r10, 32-5, _PAGE_PRESENT
- and r11, r11, r10
- rlwimi r10, r11, 0, _PAGE_PRESENT
+ rlwinm r11, r10, 31, _PAGE_ACCESSED >> 1
#endif
+ /* Load the MI_TWC with the attributes for this "segment." */
+ mtspr SPRN_MI_TWC, r11 /* Set segment attributes */
+
li r11, RPN_PATTERN | 0x200
/* The Linux PTE won't go exactly into the MMU TLB.
* Software indicator bits 20 and 23 must be clear.
@@ -472,22 +471,14 @@ _ENTRY(DTLBMiss_jmp)
* above.
*/
rlwimi r11, r10, 0, _PAGE_GUARDED
- mtspr SPRN_MD_TWC, r11
-
- /* Both _PAGE_ACCESSED and _PAGE_PRESENT has to be set.
- * We also need to know if the insn is a load/store, so:
- * Clear _PAGE_PRESENT and load that which will
- * trap into DTLB Error with store bit set accordinly.
- */
- /* PRESENT=0x1, ACCESSED=0x20
- * r11 = ((r10 & PRESENT) & ((r10 & ACCESSED) >> 5));
- * r10 = (r10 & ~PRESENT) | r11;
- */
#ifdef CONFIG_SWAP
- rlwinm r11, r10, 32-5, _PAGE_PRESENT
- and r11, r11, r10
- rlwimi r10, r11, 0, _PAGE_PRESENT
+ /* _PAGE_ACCESSED has to be set. We use second APG bit for that, 0
+ * on that bit will represent a Non Access group
+ */
+ rlwinm r11, r10, 31, _PAGE_ACCESSED >> 1
#endif
+ mtspr SPRN_MD_TWC, r11
+
/* The Linux PTE won't go exactly into the MMU TLB.
* Software indicator bits 24, 25, 26, and 27 must be
* set. All other Linux PTE bits control the behavior
@@ -647,8 +638,8 @@ InstructionBreakpoint:
*/
DTLBMissIMMR:
mtcr r12
- /* Set 512k byte guarded page and mark it valid */
- li r10, MD_PS512K | MD_GUARDED | MD_SVALID
+ /* Set 512k byte guarded page and mark it valid and accessed */
+ li r10, MD_PS512K | MD_GUARDED | MD_SVALID | M_APG2
mtspr SPRN_MD_TWC, r10
mfspr r10, SPRN_IMMR /* Get current IMMR */
rlwinm r10, r10, 0, 0xfff80000 /* Get 512 kbytes boundary */
@@ -666,8 +657,8 @@ _ENTRY(dtlb_miss_exit_2)

DTLBMissLinear:
mtcr r12
- /* Set 8M byte page and mark it valid */
- li r11, MD_PS8MEG | MD_SVALID
+ /* Set 8M byte page and mark it valid and accessed */
+ li r11, MD_PS8MEG | MD_SVALID | M_APG2
mtspr SPRN_MD_TWC, r11
rlwinm r10, r10, 0, 0x0f800000 /* 8xx supports max 256Mb RAM */
ori r10, r10, 0xf0 | MD_SPS16K | _PAGE_PRIVILEGED | _PAGE_DIRTY | \
@@ -685,8 +676,8 @@ _ENTRY(dtlb_miss_exit_3)
#ifndef CONFIG_PIN_TLB_TEXT
ITLBMissLinear:
mtcr r12
- /* Set 8M byte page and mark it valid */
- li r11, MI_PS8MEG | MI_SVALID
+ /* Set 8M byte page and mark it valid,accessed */
+ li r11, MI_PS8MEG | MI_SVALID | M_APG2
mtspr SPRN_MI_TWC, r11
rlwinm r10, r10, 0, 0x0f800000 /* 8xx supports max 256Mb RAM */
ori r10, r10, 0xf0 | MI_SPS16K | _PAGE_PRIVILEGED | _PAGE_DIRTY | \
@@ -969,7 +960,7 @@ initial_mmu:
ori r8, r8, MI_EVALID /* Mark it valid */
mtspr SPRN_MI_EPN, r8
li r8, MI_PS8MEG /* Set 8M byte page */
- ori r8, r8, MI_SVALID /* Make it valid */
+ ori r8, r8, MI_SVALID | M_APG2 /* Make it valid, APG 2 */
mtspr SPRN_MI_TWC, r8
li r8, MI_BOOTINIT /* Create RPN for address 0 */
mtspr SPRN_MI_RPN, r8 /* Store TLB entry */
@@ -996,7 +987,7 @@ initial_mmu:
ori r8, r8, MD_EVALID /* Mark it valid */
mtspr SPRN_MD_EPN, r8
li r8, MD_PS512K | MD_GUARDED /* Set 512k byte page */
- ori r8, r8, MD_SVALID /* Make it valid */
+ ori r8, r8, MD_SVALID | M_APG2 /* Make it valid and accessed */
mtspr SPRN_MD_TWC, r8
mr r8, r9 /* Create paddr for TLB */
ori r8, r8, MI_BOOTINIT|0x2 /* Inhibit cache -- Cort */
diff --git a/arch/powerpc/mm/8xx_mmu.c b/arch/powerpc/mm/8xx_mmu.c
index 5d53684c2ebd..cf77d755246d 100644
--- a/arch/powerpc/mm/8xx_mmu.c
+++ b/arch/powerpc/mm/8xx_mmu.c
@@ -79,7 +79,7 @@ void __init MMU_init_hw(void)
for (; i < 32 && mem >= LARGE_PAGE_SIZE_8M; i++) {
mtspr(SPRN_MD_CTR, ctr | (i << 8));
mtspr(SPRN_MD_EPN, (unsigned long)__va(addr) | MD_EVALID);
- mtspr(SPRN_MD_TWC, MD_PS8MEG | MD_SVALID);
+ mtspr(SPRN_MD_TWC, MD_PS8MEG | MD_SVALID | M_APG2);
mtspr(SPRN_MD_RPN, addr | flags | _PAGE_PRESENT);
addr += LARGE_PAGE_SIZE_8M;
mem -= LARGE_PAGE_SIZE_8M;
--
2.13.3

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