[PATCH 02/10] perf: Add capability for common event support

[Robin Murphy]

Many PMUs do not support common hardware/cache/etc. events and only
handle their own PMU-specific events. Since this only depends on
matching the event and PMU types, it's a prime candidate for a core
capability to save more event_init boilerplate in drivers.

Signed-off-by: Robin Murphy <robin.murphy at arm.com>
---
 include/linux/perf_event.h | 1 +
 kernel/events/core.c       | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index d2a15c0c6f8a..983201f21dd2 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -291,6 +291,7 @@ struct perf_event_pmu_context;
 #define PERF_PMU_CAP_NO_EXCLUDE			0x0040
 #define PERF_PMU_CAP_AUX_OUTPUT			0x0080
 #define PERF_PMU_CAP_EXTENDED_HW_TYPE		0x0100
+#define PERF_PMU_CAP_NO_COMMON_EVENTS		0x0200
 
 struct perf_output_handle;
 
diff --git a/kernel/events/core.c b/kernel/events/core.c
index f0f0f71213a1..7ad80826c218 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -11649,6 +11649,11 @@ static int perf_try_init_event(struct pmu *pmu, struct perf_event *event)
 	struct perf_event_context *ctx = NULL;
 	int ret;
 
+	/* Short-circuit if we know the PMU won't want this event */
+	if (pmu->capabilities & PERF_PMU_CAP_NO_COMMON_EVENTS &&
+	    event->attr.type != pmu->type)
+		return -ENOENT;
+
 	if (!try_module_get(pmu->module))
 		return -ENODEV;
 
-- 
2.39.2.101.g768bb238c484.dirty