[PATCH v2] drivers/perf: riscv: Disable PERF_SAMPLE_BRANCH_* while not supported

[Pu Lehui]

From: Pu Lehui <pulehui at huawei.com>

RISC-V perf driver does not yet support branch sampling. Although the
specification is in the works [0], it is best to disable such events
until support is available, otherwise we will get unexpected results.
Due to this reason, two riscv bpf testcases get_branch_snapshot and
perf_branches/perf_branches_hw fail.

Link: https://github.com/riscv/riscv-control-transfer-records [0]
Fixes: f5bfa23f576f ("RISC-V: Add a perf core library for pmu drivers")
Signed-off-by: Pu Lehui <pulehui at huawei.com>
---
 drivers/perf/riscv_pmu.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/perf/riscv_pmu.c b/drivers/perf/riscv_pmu.c
index c78a6fd6c57f..b4efdddb2ad9 100644
--- a/drivers/perf/riscv_pmu.c
+++ b/drivers/perf/riscv_pmu.c
@@ -313,6 +313,10 @@ static int riscv_pmu_event_init(struct perf_event *event)
 	u64 event_config = 0;
 	uint64_t cmask;
 
+	/* driver does not support branch stack sampling */
+	if (has_branch_stack(event))
+		return -EOPNOTSUPP;
+
 	hwc->flags = 0;
 	mapped_event = rvpmu->event_map(event, &event_config);
 	if (mapped_event < 0) {
-- 
2.34.1