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Subject[PATCH v5 10/17] powerpc/8xx: Use alternative scratch registers in DTLB miss handler
Date
In preparation of handling CONFIG_VMAP_STACK, DTLB miss handler need
to use different scratch registers than other exception handlers in
order to not jeopardise exception entry on stack DTLB misses.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
arch/powerpc/kernel/head_8xx.S | 27 ++++++++++++++-------------
arch/powerpc/perf/8xx-pmu.c | 12 ++++++++----
2 files changed, 22 insertions(+), 17 deletions(-)

diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 25e19af49705..3de9c5f1746c 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -193,8 +193,9 @@ SystemCall:
0: lwz r10, (dtlb_miss_counter - PAGE_OFFSET)@l(0)
addi r10, r10, 1
stw r10, (dtlb_miss_counter - PAGE_OFFSET)@l(0)
- mfspr r10, SPRN_SPRG_SCRATCH0
- mfspr r11, SPRN_SPRG_SCRATCH1
+ mfspr r10, SPRN_DAR
+ mtspr SPRN_DAR, r11 /* Tag DAR */
+ mfspr r11, SPRN_M_TW
rfi
#endif

@@ -337,8 +338,8 @@ ITLBMissLinear:

. = 0x1200
DataStoreTLBMiss:
- mtspr SPRN_SPRG_SCRATCH0, r10
- mtspr SPRN_SPRG_SCRATCH1, r11
+ mtspr SPRN_DAR, r10
+ mtspr SPRN_M_TW, r11
mfcr r11

/* If we are faulting a kernel address, we have to use the
@@ -403,10 +404,10 @@ DataStoreTLBMiss:
mtspr SPRN_MD_RPN, r10 /* Update TLB entry */

/* Restore registers */
- mtspr SPRN_DAR, r11 /* Tag DAR */

-0: mfspr r10, SPRN_SPRG_SCRATCH0
- mfspr r11, SPRN_SPRG_SCRATCH1
+0: mfspr r10, SPRN_DAR
+ mtspr SPRN_DAR, r11 /* Tag DAR */
+ mfspr r11, SPRN_M_TW
rfi
patch_site 0b, patch__dtlbmiss_exit_1

@@ -422,10 +423,10 @@ DTLBMissIMMR:
mtspr SPRN_MD_RPN, r10 /* Update TLB entry */

li r11, RPN_PATTERN
- mtspr SPRN_DAR, r11 /* Tag DAR */

-0: mfspr r10, SPRN_SPRG_SCRATCH0
- mfspr r11, SPRN_SPRG_SCRATCH1
+0: mfspr r10, SPRN_DAR
+ mtspr SPRN_DAR, r11 /* Tag DAR */
+ mfspr r11, SPRN_M_TW
rfi
patch_site 0b, patch__dtlbmiss_exit_2

@@ -459,10 +460,10 @@ DTLBMissLinear:
mtspr SPRN_MD_RPN, r10 /* Update TLB entry */

li r11, RPN_PATTERN
- mtspr SPRN_DAR, r11 /* Tag DAR */

-0: mfspr r10, SPRN_SPRG_SCRATCH0
- mfspr r11, SPRN_SPRG_SCRATCH1
+0: mfspr r10, SPRN_DAR
+ mtspr SPRN_DAR, r11 /* Tag DAR */
+ mfspr r11, SPRN_M_TW
rfi
patch_site 0b, patch__dtlbmiss_exit_3

diff --git a/arch/powerpc/perf/8xx-pmu.c b/arch/powerpc/perf/8xx-pmu.c
index 19124b0b171a..1ad03c55c88c 100644
--- a/arch/powerpc/perf/8xx-pmu.c
+++ b/arch/powerpc/perf/8xx-pmu.c
@@ -157,10 +157,6 @@ static void mpc8xx_pmu_read(struct perf_event *event)

static void mpc8xx_pmu_del(struct perf_event *event, int flags)
{
- /* mfspr r10, SPRN_SPRG_SCRATCH0 */
- unsigned int insn = PPC_INST_MFSPR | __PPC_RS(R10) |
- __PPC_SPR(SPRN_SPRG_SCRATCH0);
-
mpc8xx_pmu_read(event);

/* If it was the last user, stop counting to avoid useles overhead */
@@ -173,6 +169,10 @@ static void mpc8xx_pmu_del(struct perf_event *event, int flags)
break;
case PERF_8xx_ID_ITLB_LOAD_MISS:
if (atomic_dec_return(&itlb_miss_ref) == 0) {
+ /* mfspr r10, SPRN_SPRG_SCRATCH0 */
+ unsigned int insn = PPC_INST_MFSPR | __PPC_RS(R10) |
+ __PPC_SPR(SPRN_SPRG_SCRATCH0);
+
patch_instruction_site(&patch__itlbmiss_exit_1, insn);
#ifndef CONFIG_PIN_TLB_TEXT
patch_instruction_site(&patch__itlbmiss_exit_2, insn);
@@ -181,6 +181,10 @@ static void mpc8xx_pmu_del(struct perf_event *event, int flags)
break;
case PERF_8xx_ID_DTLB_LOAD_MISS:
if (atomic_dec_return(&dtlb_miss_ref) == 0) {
+ /* mfspr r10, SPRN_DAR */
+ unsigned int insn = PPC_INST_MFSPR | __PPC_RS(R10) |
+ __PPC_SPR(SPRN_DAR);
+
patch_instruction_site(&patch__dtlbmiss_exit_1, insn);
patch_instruction_site(&patch__dtlbmiss_exit_2, insn);
patch_instruction_site(&patch__dtlbmiss_exit_3, insn);
--
2.13.3
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