[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>

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

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.