@@ -537,9 +537,28 @@ static int armpmu_event_init(struct perf_event *event)
!cpumask_test_cpu(event->cpu, &armpmu->supported_cpus))
return -ENOENT;
- /* does not support taken branch sampling */
- if (has_branch_stack(event))
- return -EOPNOTSUPP;
+ if (has_branch_stack(event)) {
+ /*
+ * BRBE support is absent. Select CONFIG_ARM_BRBE_PMU
+ * in the config, before branch stack sampling events
+ * can be requested.
+ */
+ if (!IS_ENABLED(CONFIG_ARM_BRBE_PMU)) {
+ pr_info("BRBE is disabled, select CONFIG_ARM_BRBE_PMU\n");
+ return -EOPNOTSUPP;
+ }
+
+ /*
+ * Branch stack sampling event can not be supported in
+ * case either the required driver itself is absent or
+ * BRBE buffer, is not supported. Besides checking for
+ * the callback prevents a crash in case it's absent.
+ */
+ if (!armpmu->brbe_supported || !armpmu->brbe_supported(event)) {
+ pr_info("BRBE is not supported\n");
+ return -EOPNOTSUPP;
+ }
+ }
if (armpmu->map_event(event) == -ENOENT)
return -ENOENT;
Now that all the required pieces are already in place, just enable the perf branch stack sampling support on arm64 platform, by removing the gate which blocks it in armpmu_event_init(). Cc: Mark Rutland <mark.rutland@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: linux-kernel@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> --- drivers/perf/arm_pmu.c | 25 ++++++++++++++++++++++--- 1 file changed, 22 insertions(+), 3 deletions(-)