linux-kernel - [PATCH RFC 2/3] perf/x86/intel/pt: Add support for pause

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Date:   Thu, 23 Nov 2023 14:18:50 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Thomas Richter <tmricht@...ux.ibm.com>,
        Hendrik Brueckner <brueckner@...ux.ibm.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        James Clark <james.clark@....com>, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org,
        Yicong Yang <yangyicong@...ilicon.com>,
        Jonathan Cameron <jonathan.cameron@...wei.com>,
        Will Deacon <will@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org
Subject: [PATCH RFC 2/3] perf/x86/intel/pt: Add support for pause_resume()

Prevent tracing to start if aux_paused.

Implement pause_resume() callback. When aux_paused, stop tracing. When
not aux_paused, only start tracing if it isn't currently meant to be
stopped.

Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
---
 arch/x86/events/intel/pt.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
index 42a55794004a..aa883b64814a 100644
--- a/arch/x86/events/intel/pt.c
+++ b/arch/x86/events/intel/pt.c
@@ -418,6 +418,9 @@ static void pt_config_start(struct perf_event *event)
 	struct pt *pt = this_cpu_ptr(&pt_ctx);
 	u64 ctl = event->hw.config;
 
+	if (event->aux_paused)
+		return;
+
 	ctl |= RTIT_CTL_TRACEEN;
 	if (READ_ONCE(pt->vmx_on))
 		perf_aux_output_flag(&pt->handle, PERF_AUX_FLAG_PARTIAL);
@@ -1563,6 +1566,14 @@ EXPORT_SYMBOL_GPL(intel_pt_handle_vmx);
  * PMU callbacks
  */
 
+static void pt_event_pause_resume(struct perf_event *event)
+{
+	if (event->aux_paused)
+		pt_config_stop(event);
+	else if (!event->hw.state)
+		pt_config_start(event);
+}
+
 static void pt_event_start(struct perf_event *event, int mode)
 {
 	struct hw_perf_event *hwc = &event->hw;
@@ -1798,6 +1809,7 @@ static __init int pt_init(void)
 	pt_pmu.pmu.del			 = pt_event_del;
 	pt_pmu.pmu.start		 = pt_event_start;
 	pt_pmu.pmu.stop			 = pt_event_stop;
+	pt_pmu.pmu.pause_resume		 = pt_event_pause_resume;
 	pt_pmu.pmu.snapshot_aux		 = pt_event_snapshot_aux;
 	pt_pmu.pmu.read			 = pt_event_read;
 	pt_pmu.pmu.setup_aux		 = pt_buffer_setup_aux;
-- 
2.34.1