[PATCH] ppc64: Turn runlatch on in exception entry

Enable the runlatch at the start of each exception.  Unfortunately we are out
of space in the 0x300 handler, so I added it a bit later.

The SPR write is fairly expensive, perhaps we should cache the runlatch state
in the paca and avoid the write when possible.

We don't need to turn the runlatch off, we do that in the idle loop.  Better
to take the hit in the idle loop than for each exception exit.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 19 insertions, 0 deletions

diff --git a/arch/ppc64/kernel/head.S b/arch/ppc64/kernel/head.S
index 675c2708588f..93ebcac0d5a2 100644
--- a/arch/ppc64/kernel/head.S
+++ b/arch/ppc64/kernel/head.S
@@ -308,6 +308,7 @@ exception_marker:
 label##_pSeries:                                        \
         HMT_MEDIUM;                                     \
         mtspr   SPRG1,r13;              /* save r13 */  \
+        RUNLATCH_ON(r13);                               \
         EXCEPTION_PROLOG_PSERIES(PACA_EXGEN, label##_common)
 
 #define STD_EXCEPTION_ISERIES(n, label, area)           \
@@ -315,6 +316,7 @@ label##_pSeries:					\
 label##_iSeries:                                        \
         HMT_MEDIUM;                                     \
         mtspr   SPRG1,r13;              /* save r13 */  \
+        RUNLATCH_ON(r13);                               \
         EXCEPTION_PROLOG_ISERIES_1(area);               \
         EXCEPTION_PROLOG_ISERIES_2;                     \
         b       label##_common
@@ -324,6 +326,7 @@ label##_iSeries:					\
 label##_iSeries:                                                        \
         HMT_MEDIUM;                                                     \
         mtspr   SPRG1,r13;              /* save r13 */                  \
+        RUNLATCH_ON(r13);                                               \
         EXCEPTION_PROLOG_ISERIES_1(PACA_EXGEN);                         \
         lbz     r10,PACAPROCENABLED(r13);                               \
         cmpwi   0,r10,0;                                                \
@@ -393,6 +396,7 @@ __start_interrupts:
 _machine_check_pSeries:
         HMT_MEDIUM
         mtspr   SPRG1,r13               /* save r13 */
+        RUNLATCH_ON(r13)
         EXCEPTION_PROLOG_PSERIES(PACA_EXMC, machine_check_common)
 
         . = 0x300
@@ -419,6 +423,7 @@ END_FTR_SECTION_IFCLR(CPU_FTR_SLB)
 data_access_slb_pSeries:
         HMT_MEDIUM
         mtspr   SPRG1,r13
+        RUNLATCH_ON(r13)
         mfspr   r13,SPRG3               /* get paca address into r13 */
         std     r9,PACA_EXSLB+EX_R9(r13)        /* save r9 - r12 */
         std     r10,PACA_EXSLB+EX_R10(r13)
@@ -439,6 +444,7 @@ data_access_slb_pSeries:
 instruction_access_slb_pSeries:
         HMT_MEDIUM
         mtspr   SPRG1,r13
+        RUNLATCH_ON(r13)
         mfspr   r13,SPRG3               /* get paca address into r13 */
         std     r9,PACA_EXSLB+EX_R9(r13)        /* save r9 - r12 */
         std     r10,PACA_EXSLB+EX_R10(r13)
@@ -464,6 +470,7 @@ instruction_access_slb_pSeries:
         .globl  system_call_pSeries
 system_call_pSeries:
         HMT_MEDIUM
+        RUNLATCH_ON(r9)
         mr      r9,r13
         mfmsr   r10
         mfspr   r13,SPRG3
@@ -707,11 +714,13 @@ fwnmi_data_area:
 system_reset_fwnmi:
         HMT_MEDIUM
         mtspr   SPRG1,r13               /* save r13 */
+        RUNLATCH_ON(r13)
         EXCEPTION_PROLOG_PSERIES(PACA_EXGEN, system_reset_common)
         .globl machine_check_fwnmi
 machine_check_fwnmi:
         HMT_MEDIUM
         mtspr   SPRG1,r13               /* save r13 */
+        RUNLATCH_ON(r13)
         EXCEPTION_PROLOG_PSERIES(PACA_EXMC, machine_check_common)
 
         /*
@@ -848,6 +857,7 @@ unrecov_fer:
         .align  7
         .globl data_access_common
 data_access_common:
+        RUNLATCH_ON(r10)                /* It wont fit in the 0x300 handler */
         mfspr   r10,DAR
         std     r10,PACA_EXGEN+EX_DAR(r13)
         mfspr   r10,DSISR
diff --git a/include/asm-ppc64/processor.h b/include/asm-ppc64/processor.h
index 06aa07c2c71d..352306cfb579 100644
--- a/include/asm-ppc64/processor.h
+++ b/include/asm-ppc64/processor.h
@@ -524,6 +524,15 @@ static inline void ppc64_runlatch_off(void)
 
 #endif /* __ASSEMBLY__ */
 
+#ifdef __KERNEL__
+#define RUNLATCH_ON(REG)                        \
+BEGIN_FTR_SECTION                               \
+        mfspr   (REG),SPRN_CTRLF;               \
+        ori     (REG),(REG),CTRL_RUNLATCH;      \
+        mtspr   SPRN_CTRLT,(REG);               \
+END_FTR_SECTION_IFSET(CPU_FTR_CTRL)
+#endif
+
 /*
  * Number of entries in the SLB. If this ever changes we should handle
  * it with a use a cpu feature fixup.