[PATCH 1/3] perf: disable sampled events if no PMU interrupt

[Vince Weaver]

Add common code to generate ENOTSUPP at event creation time if an 
architecture attempts to create a sampled event and PERF_PMU_NO_INTERRUPT
is set.

This adds a new pmu->capabilities flag.  
Initially we only support PERF_PMU_NO_INTERRUPT (to indicate a PMU
has no support for generating hardware interrupts) but there are 
other capabilities that can be added later.

Signed-off-by: Vince Weaver <vincent.weaver@xxxxxxxxx>

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 3356abc..2164763 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -251,9 +251,20 @@ struct pmu {
 	 * flush branch stack on context-switches (needed in cpu-wide mode)
 	 */
 	void (*flush_branch_stack)	(void);
+
+	/*
+	 * various common per-pmu feature flags
+	 */
+	int capabilities;
+
 };
 
 /**
+ * struct pmu->capabilites flags
+ */
+#define PERF_PMU_NO_INTERRUPT		1
+
+/**
  * enum perf_event_active_state - the states of a event
  */
 enum perf_event_active_state {
diff --git a/kernel/events/core.c b/kernel/events/core.c
index f83a71a..f5d8554 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7072,6 +7072,13 @@ SYSCALL_DEFINE5(perf_event_open,
 		}
 	}
 
+	if (is_sampling_event(event)) {
+		if (event->pmu->capabilities & PERF_PMU_NO_INTERRUPT) {
+			err = -ENOTSUPP;
+			goto err_alloc;
+		}
+	}
+
 	account_event(event);
 
 	/*
--
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