[PATCH V8 08/10] powerpc, perf: Change POWER8 PMU configuration to work with SW filters

[Anshuman Khandual]

The kernel now supports SW based branch filters for book3s systems with
some specific requirements while dealing with HW supported branch filters
in order to achieve overall OR semantics prevailing in perf branch stack
sampling framework. This patch adapts the BHRB branch filter configuration
to meet those protocols. POWER8 PMU can only handle one HW based branch
filter request at any point of time. For all other combinations PMU will
pass it on to the SW.

Signed-off-by: Anshuman Khandual <khandual at linux.vnet.ibm.com>
---
 arch/powerpc/perf/power8-pmu.c | 51 ++++++++++++++++++++++++++++++++++++------
 1 file changed, 44 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/perf/power8-pmu.c b/arch/powerpc/perf/power8-pmu.c
index 5e17cb5..8fccf6c 100644
--- a/arch/powerpc/perf/power8-pmu.c
+++ b/arch/powerpc/perf/power8-pmu.c
@@ -656,6 +656,16 @@ static int power8_generic_events[] = {
 
 static u64 power8_bhrb_filter_map(u64 branch_sample_type, u64 *bhrb_filter)
 {
+	u64 x, pmu_bhrb_filter;
+
+	pmu_bhrb_filter = 0;
+	*bhrb_filter = 0;
+
+	if (branch_sample_type & PERF_SAMPLE_BRANCH_ANY) {
+		*bhrb_filter = PERF_SAMPLE_BRANCH_ANY;
+		return pmu_bhrb_filter;
+	}
+
 	/* BHRB and regular PMU events share the same privilege state
 	 * filter configuration. BHRB is always recorded along with a
 	 * regular PMU event. As the privilege state filter is handled
@@ -666,15 +676,42 @@ static u64 power8_bhrb_filter_map(u64 branch_sample_type, u64 *bhrb_filter)
 	/* Ignore user, kernel, hv bits */
 	branch_sample_type &= ~PERF_SAMPLE_BRANCH_PLM_ALL;
 
-	/* No branch filter requested */
-	if (branch_sample_type == PERF_SAMPLE_BRANCH_ANY)
-		return 0;
+	/*
+	 * POWER8 does not support ORing of PMU HW branch filters. Hence
+	 * if multiple branch filters are requested which may include filters
+	 * supported in PMU, still go ahead and clear the PMU based HW branch
+	 * filter component as in this case all the filters will be processed
+	 * in SW.
+	 */
 
-	if (branch_sample_type == PERF_SAMPLE_BRANCH_ANY_CALL)
-		return POWER8_MMCRA_IFM1;
+	for_each_branch_sample_type(x) {
+		/* Ignore privilege branch filters */
+		if ((x == PERF_SAMPLE_BRANCH_USER)
+			|| (x == PERF_SAMPLE_BRANCH_KERNEL)
+				|| (x == PERF_SAMPLE_BRANCH_HV))
+			continue;
+
+		if (!(branch_sample_type & x))
+			continue;
+
+		/* Supported individual PMU branch filters */
+		if (branch_sample_type & PERF_SAMPLE_BRANCH_ANY_CALL) {
+			branch_sample_type &= ~PERF_SAMPLE_BRANCH_ANY_CALL;
+			if (branch_sample_type) {
+				/* Multiple filters will be processed in SW */
+				pmu_bhrb_filter = 0;
+				*bhrb_filter = 0;
+				return pmu_bhrb_filter;
+			} else {
+				/* Individual filter will be processed in HW */
+				pmu_bhrb_filter |= POWER8_MMCRA_IFM1;
+				*bhrb_filter    |= PERF_SAMPLE_BRANCH_ANY_CALL;
+				return pmu_bhrb_filter;
+			}
+		}
+	}
 
-	/* Every thing else is unsupported */
-	return -1;
+	return pmu_bhrb_filter;
 }
 
 static void power8_config_bhrb(u64 pmu_bhrb_filter)
-- 
2.1.0