linux-kernel - [PATCH] perf parser: Improve error message for PMU address filters

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Message-Id: <20180704095409.6109-1-jackdev@mailbox.org>
Date:   Wed,  4 Jul 2018 11:54:09 +0200
From:   Jack Henschel <jackdev@...lbox.org>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Jack Henschel <jackdev@...lbox.org>
Subject: [PATCH] perf parser: Improve error message for PMU address filters

This patch improves the error message of the perf events parser
when the PMU hardware does not support address filters.

Previously, the perf returned the following error:
> --filter option should follow a -e tracepoint or HW tracer option
This implies there is some syntax error present in the command line,
which is not true. Rather, notify the user that the CPU does not have
support for this feature.

For example, Intel chips based on the Broadwell micro-archticture have
the Intel PT PMU, but do not support address filtering.

Signed-off-by: Jack Henschel <jackdev@...lbox.org>
---
 tools/perf/util/parse-events.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 15eec49e71a1..f8cd3e7c9186 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -1991,8 +1991,11 @@ static int set_filter(struct perf_evsel *evsel, const void *arg)
 	int nr_addr_filters = 0;
 	struct perf_pmu *pmu = NULL;
 
-	if (evsel == NULL)
-		goto err;
+	if (evsel == NULL) {
+		fprintf(stderr,
+			"--filter option should follow a -e tracepoint or HW tracer option\n");
+		return -1;
+	}
 
 	if (evsel->attr.type == PERF_TYPE_TRACEPOINT) {
 		if (perf_evsel__append_tp_filter(evsel, str) < 0) {
@@ -2014,8 +2017,11 @@ static int set_filter(struct perf_evsel *evsel, const void *arg)
 		perf_pmu__scan_file(pmu, "nr_addr_filters",
 				    "%d", &nr_addr_filters);
 
-	if (!nr_addr_filters)
-		goto err;
+	if (!nr_addr_filters) {
+		fprintf(stderr,
+			"This CPU does not support address filtering\n");
+		return -1;
+	}
 
 	if (perf_evsel__append_addr_filter(evsel, str) < 0) {
 		fprintf(stderr,
@@ -2024,12 +2030,6 @@ static int set_filter(struct perf_evsel *evsel, const void *arg)
 	}
 
 	return 0;
-
-err:
-	fprintf(stderr,
-		"--filter option should follow a -e tracepoint or HW tracer option\n");
-
-	return -1;
 }
 
 int parse_filter(const struct option *opt, const char *str,
-- 
2.18.0