linux-kernel - [PATCH] perf intel-pt: Fix error with config term pt=0

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Message-Id: <20181127084336.12142-1-adrian.hunter@intel.com>
Date:   Tue, 27 Nov 2018 10:43:36 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Jiri Olsa <jolsa@...hat.com>, linux-kernel@...r.kernel.org
Subject: [PATCH] perf intel-pt: Fix error with config term pt=0

Users should never use 'pt=0', but if they do it may give a meaningless
error:

	$ perf record -e intel_pt/pt=0/u uname
	Error:
	The sys_perf_event_open() syscall returned with 22 (Invalid argument) for
	event (intel_pt/pt=0/u).

Fix that by forcing 'pt=1'.

Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
---
 tools/perf/arch/x86/util/intel-pt.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/perf/arch/x86/util/intel-pt.c b/tools/perf/arch/x86/util/intel-pt.c
index db0ba8caf5a2..af25a7824ee0 100644
--- a/tools/perf/arch/x86/util/intel-pt.c
+++ b/tools/perf/arch/x86/util/intel-pt.c
@@ -524,10 +524,18 @@ static int intel_pt_validate_config(struct perf_pmu *intel_pt_pmu,
 				    struct perf_evsel *evsel)
 {
 	int err;
+	char c;
 
 	if (!evsel)
 		return 0;
 
+	/*
+	 * If supported, force pass-through config term (pt=1) even if user
+	 * sets pt=0, which avoids senseless kernel errors.
+	 */
+	if (perf_pmu__scan_file(intel_pt_pmu, "format/pt", "%c", &c) == 1)
+		evsel->attr.config |= 1;
+
 	err = intel_pt_val_config_term(intel_pt_pmu, "caps/cycle_thresholds",
 				       "cyc_thresh", "caps/psb_cyc",
 				       evsel->attr.config);
-- 
2.17.1