linux-kernel - [PATCH 1/2] perf: Allow normal events to be sources of AUX data

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Date:   Thu,  2 May 2019 13:50:21 +0300
From:   Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:     Arnaldo Carvalho de Melo <acme@...hat.com>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        jolsa@...hat.com, adrian.hunter@...el.com,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Subject: [PATCH 1/2] perf: Allow normal events to be sources of AUX data

In some cases, ordinary (non-AUX) events can generate data for AUX events.
For example, PEBS events can come out as records in the Intel PT stream
instead of their usual DS records, if configured to do so.

Add an attribute bit for such events to be configured to generate AUX data.

Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
---
 include/uapi/linux/perf_event.h | 3 ++-
 kernel/events/core.c            | 9 +++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 7198ddd0c6b1..213cae95e713 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -374,7 +374,8 @@ struct perf_event_attr {
 				namespaces     :  1, /* include namespaces data */
 				ksymbol        :  1, /* include ksymbol events */
 				bpf_event      :  1, /* include bpf events */
-				__reserved_1   : 33;
+				aux_source     :  1, /* generate AUX records instead of events */
+				__reserved_1   : 32;
 
 	union {
 		__u32		wakeup_events;	  /* wakeup every n events */
diff --git a/kernel/events/core.c b/kernel/events/core.c
index abbd4b3b96c2..ea9eff6fcf6a 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -10382,6 +10382,15 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
 		goto err_ns;
 	}
 
+	/*
+	 * If it's set at this point, the PMU didn't handle it, so
+	 * it doesn't do it.
+	 */
+	if (event->attr.aux_source) {
+		err = -EOPNOTSUPP;
+		goto err_pmu;
+	}
+
 	err = exclusive_event_init(event);
 	if (err)
 		goto err_pmu;
-- 
2.20.1