arch/powerpc/perf: Update get_mem_data_src function to use saved values of sier and mmcra regs

JIRA: https://issues.redhat.com/browse/RHEL-80602



commit f848e7ee1588d66539da7315d9a99bfaeda3b970
Author: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Date:   Tue Jan 21 18:46:21 2025 +0530

    arch/powerpc/perf: Update get_mem_data_src function to use saved values of sier and mmcra regs

    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@linux.vnet.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
    Link: https://patch.msgid.link/20250121131621.39054-2-atrajeev@linux.vnet.ibm.com



Signed-off-by: Mamatha Inamdar <minamdar@redhat.com>

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) {