[PATCH 18/19] perf: Introduce positive capability for raw events

[Robin Murphy <robin.murphy@arm.com>]

Only a handful of CPU PMUs accept PERF_TYPE_{RAW,HARDWARE,HW_CACHE}
events without registering themselves as PERF_TYPE_RAW in the first
place. Add an explicit opt-in for these special cases, so that we can
make life easier for every other driver (and probably also speed up the
slow-path search) by having perf_try_init_event() do the basic type
checking to cover the majority of cases.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---

A further possibility is to automatically add the cap to PERF_TYPE_RAW
PMUs in perf_pmu_register() to have a single point-of-use condition; I'm
undecided...
---
 arch/s390/kernel/perf_cpum_cf.c    |  1 +
 arch/s390/kernel/perf_pai_crypto.c |  2 +-
 arch/s390/kernel/perf_pai_ext.c    |  2 +-
 arch/x86/events/core.c             |  2 +-
 drivers/perf/arm_pmu.c             |  1 +
 include/linux/perf_event.h         |  1 +
 kernel/events/core.c               | 15 +++++++++++++++
 7 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/arch/s390/kernel/perf_cpum_cf.c b/arch/s390/kernel/perf_cpum_cf.c
index 1a94e0944bc5..782ab755ddd4 100644
--- a/arch/s390/kernel/perf_cpum_cf.c
+++ b/arch/s390/kernel/perf_cpum_cf.c
@@ -1054,6 +1054,7 @@ static void cpumf_pmu_del(struct perf_event *event, int flags)
 /* Performance monitoring unit for s390x */
 static struct pmu cpumf_pmu = {
 	.task_ctx_nr  = perf_sw_context,
+	.capabilities = PERF_PMU_CAP_RAW_EVENTS,
 	.pmu_enable   = cpumf_pmu_enable,
 	.pmu_disable  = cpumf_pmu_disable,
 	.event_init   = cpumf_pmu_event_init,
diff --git a/arch/s390/kernel/perf_pai_crypto.c b/arch/s390/kernel/perf_pai_crypto.c
index a64b6b056a21..b5b6d8b5d943 100644
--- a/arch/s390/kernel/perf_pai_crypto.c
+++ b/arch/s390/kernel/perf_pai_crypto.c
@@ -569,7 +569,7 @@ static const struct attribute_group *paicrypt_attr_groups[] = {
 /* Performance monitoring unit for mapped counters */
 static struct pmu paicrypt = {
 	.task_ctx_nr  = perf_hw_context,
-	.capabilities = PERF_PMU_CAP_SAMPLING,
+	.capabilities = PERF_PMU_CAP_SAMPLING | PERF_PMU_CAP_RAW_EVENTS,
 	.event_init   = paicrypt_event_init,
 	.add	      = paicrypt_add,
 	.del	      = paicrypt_del,
diff --git a/arch/s390/kernel/perf_pai_ext.c b/arch/s390/kernel/perf_pai_ext.c
index 1261f80c6d52..bcd28c38da70 100644
--- a/arch/s390/kernel/perf_pai_ext.c
+++ b/arch/s390/kernel/perf_pai_ext.c
@@ -595,7 +595,7 @@ static const struct attribute_group *paiext_attr_groups[] = {
 /* Performance monitoring unit for mapped counters */
 static struct pmu paiext = {
 	.task_ctx_nr  = perf_hw_context,
-	.capabilities = PERF_PMU_CAP_SAMPLING,
+	.capabilities = PERF_PMU_CAP_SAMPLING | PERF_PMU_CAP_RAW_EVENTS,
 	.event_init   = paiext_event_init,
 	.add	      = paiext_add,
 	.del	      = paiext_del,
diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 789dfca2fa67..764728bb80ae 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -2697,7 +2697,7 @@ static bool x86_pmu_filter(struct pmu *pmu, int cpu)
 }
 
 static struct pmu pmu = {
-	.capabilities		= PERF_PMU_CAP_SAMPLING,
+	.capabilities		= PERF_PMU_CAP_SAMPLING | PERF_PMU_CAP_RAW_EVENTS,
 
 	.pmu_enable		= x86_pmu_enable,
 	.pmu_disable		= x86_pmu_disable,
diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
index 72d8f38d0aa5..bc772a3bf411 100644
--- a/drivers/perf/arm_pmu.c
+++ b/drivers/perf/arm_pmu.c
@@ -877,6 +877,7 @@ struct arm_pmu *armpmu_alloc(void)
 		 * specific PMU.
 		 */
 		.capabilities	= PERF_PMU_CAP_SAMPLING |
+				  PERF_PMU_CAP_RAW_EVENTS |
 				  PERF_PMU_CAP_EXTENDED_REGS |
 				  PERF_PMU_CAP_EXTENDED_HW_TYPE,
 	};
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 183b7c48b329..c6ad036c0037 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -305,6 +305,7 @@ struct perf_event_pmu_context;
 #define PERF_PMU_CAP_EXTENDED_HW_TYPE	0x0100
 #define PERF_PMU_CAP_AUX_PAUSE		0x0200
 #define PERF_PMU_CAP_AUX_PREFER_LARGE	0x0400
+#define PERF_PMU_CAP_RAW_EVENTS		0x0800
 
 /**
  * pmu::scope
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 71b2a6730705..2ecee76d2ae2 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -12556,11 +12556,26 @@ static inline bool has_extended_regs(struct perf_event *event)
 	       (event->attr.sample_regs_intr & PERF_REG_EXTENDED_MASK);
 }
 
+static bool is_raw_pmu(const struct pmu *pmu)
+{
+	return pmu->type == PERF_TYPE_RAW ||
+	       pmu->capabilities & PERF_PMU_CAP_RAW_EVENTS;
+}
+
 static int perf_try_init_event(struct pmu *pmu, struct perf_event *event)
 {
 	struct perf_event_context *ctx = NULL;
 	int ret;
 
+	/*
+	 * Before touching anything, we can safely skip:
+	 * - any event for a specific PMU which is not this one
+	 * - any common event if this PMU doesn't support them
+	 */
+	if (event->attr.type != pmu->type &&
+	    (event->attr.type >= PERF_TYPE_MAX || is_raw_pmu(pmu)))
+		return -ENOENT;
+
 	if (!try_module_get(pmu->module))
 		return -ENODEV;
 
-- 
2.39.2.101.g768bb238c484.dirty