[PATCH V2 2/2] arch/powerpc/perf: Update get_mem_data_src function to use saved values of sier and mmcra regs

[Athira Rajeev]

During performance monitor interrupt handling, the regs are setup using
perf_read_regs function. Here some of the pt_regs fields is overloaded.
Samples Instruction Event Register (SIER) is loaded into pt_regs,
overloading regs->dar. And regs->dsisr to store MMCRA (Monitor Mode
Control Register A) so that we only need to read these once on each
interrupt.

Update the isa207_get_mem_data_src function to use regs->dar instead of
reading from SPRN_SIER again. Also use regs->dsisr to read the mmcra
value

Signed-off-by: Athira Rajeev <atrajeev at linux.vnet.ibm.com>
---
 arch/powerpc/perf/isa207-common.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/perf/isa207-common.c b/arch/powerpc/perf/isa207-common.c
index 031a2b63c171..2b3547fdba4a 100644
--- a/arch/powerpc/perf/isa207-common.c
+++ b/arch/powerpc/perf/isa207-common.c
@@ -319,7 +319,13 @@ void isa207_get_mem_data_src(union perf_mem_data_src *dsrc, u32 flags,
 		return;
 	}
 
-	sier = mfspr(SPRN_SIER);
+	/*
+	 * Use regs-dar for SPRN_SIER which is saved
+	 * during perf_read_regs at the beginning
+	 * of the PMU interrupt handler to avoid multiple
+	 * reads of SPRN_SIER
+	 */
+	sier = regs->dar;
 	val = (sier & ISA207_SIER_TYPE_MASK) >> ISA207_SIER_TYPE_SHIFT;
 	if (val != 1 && val != 2 && !(val == 7 && cpu_has_feature(CPU_FTR_ARCH_31))) {
 		dsrc->val = 0;
@@ -340,8 +346,12 @@ void isa207_get_mem_data_src(union perf_mem_data_src *dsrc, u32 flags,
 		 * to determine the exact instruction type. If the sampling
 		 * criteria is neither load or store, set the type as default
 		 * to NA.
+		 *
+		 * Use regs->dsisr for MMCRA which is saved during perf_read_regs
+		 * at the beginning of the PMU interrupt handler to avoid
+		 * multiple reads of SPRN_MMCRA
 		 */
-		mmcra = mfspr(SPRN_MMCRA);
+		mmcra = regs->dsisr;
 
 		op_type = (mmcra >> MMCRA_SAMP_ELIG_SHIFT) & MMCRA_SAMP_ELIG_MASK;
 		switch (op_type) {
-- 
2.39.3