[PATCH 1/3] powerpc/perf: Fix branch_filter support for multiple filters in powerpc

[Athira Rajeev]

For PERF_SAMPLE_BRANCH_STACK sample type, different branch_sample_type
ie branch filters are supported. The branch filters are requested via
event attribute "branch_sample_type". Multiple branch filters can be
passed in event attribute.

Example:
perf record -b -o- -B --branch-filter any,ind_call true

Powerpc does not support having multiple branch filters at
sametime. In powerpc, branch filters for branch stack sampling
is set via MMCRA IFM bits [32:33]. But currently when requesting
for multiple filter types, the "perf record" command does not
report any error.

Example:
perf record -b -o- -B --branch-filter any,save_type true
perf record -b -o- -B --branch-filter any,ind_call true

The "bhrb_filter_map" function in PMU driver code does the
validity check for supported branch filters. But this check
is done for single filter. Hence "perf record" will proceed
here without reporting any error.

Fix power_pmu_event_init to return EOPNOTSUPP when multiple
branch filters are requested in the event attr.

After the fix:
perf record --branch-filter any,ind_call -- ls
Error:
cycles: PMU Hardware doesn't support sampling/overflow-interrupts.
Try 'perf stat'

Reported-by: Disha Goel <disgoel at linux.vnet.ibm.com>
Signed-off-by: Athira Rajeev <atrajeev at linux.vnet.ibm.com>
Reviewed-by: Madhavan Srinivasan <maddy at linux.ibm.com>
---
 arch/powerpc/perf/core-book3s.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index 13919eb96931..2c2d235cb8d8 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -2131,6 +2131,21 @@ static int power_pmu_event_init(struct perf_event *event)
 	if (has_branch_stack(event)) {
 		u64 bhrb_filter = -1;
 
+		/*
+		 * powerpc does not support having multiple branch filters
+		 * at sametime. Branch filters are set via MMCRA IFM[32:33]
+		 * bits for power8 and above. Return EOPNOTSUPP when multiple
+		 * branch filters are requested in the event attr.
+		 *
+		 * When opening event via perf_event_open, branch_sample_type
+		 * gets adjusted in perf_copy_attr function. Kernel will
+		 * automatically adjust the branch_sample_type based on the
+		 * event modifier settings to include PERF_SAMPLE_BRANCH_PLM_ALL.
+		 * Hence drop the check for PERF_SAMPLE_BRANCH_PLM_ALL.
+		 */
+		if (hweight64(event->attr.branch_sample_type & ~PERF_SAMPLE_BRANCH_PLM_ALL) > 1)
+			return -EOPNOTSUPP;
+
 		if (ppmu->bhrb_filter_map)
 			bhrb_filter = ppmu->bhrb_filter_map(
 					event->attr.branch_sample_type);
-- 
2.31.1