linux-kernel - [PATCH 2/4] perf evsel: Print warning for excluding kernel mode instruction tracing

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Date:   Sat, 30 Jan 2021 00:35:11 +0530
From:   Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Leo Yan <leo.yan@...aro.org>
Cc:     coresight@...ts.linaro.org, Stephen Boyd <swboyd@...omium.org>,
        Denis Nikitin <denik@...omium.org>,
        Mattias Nissler <mnissler@...omium.org>,
        Al Grant <al.grant@....com>, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
Subject: [PATCH 2/4] perf evsel: Print warning for excluding kernel mode instruction tracing

Add a warning message to check CONFIG_EXCLUDE_KERNEL_HW_ITRACE kernel
config which excludes kernel mode instruction tracing to help perf tool
users identify the perf event open failure when they attempt kernel mode
tracing with this config enabled.

Tested-by: Denis Nikitin <denik@...omium.org>
Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
---
 tools/perf/util/evsel.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index c26ea82220bd..09cc0349f883 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2630,7 +2630,8 @@ int evsel__open_strerror(struct evsel *evsel, struct target *target,
 		 ">= 1: Disallow CPU event access\n"
 		 ">= 2: Disallow kernel profiling\n"
 		 "To make the adjusted perf_event_paranoid setting permanent preserve it\n"
-		 "in /etc/sysctl.conf (e.g. kernel.perf_event_paranoid = <setting>)",
+		 "in /etc/sysctl.conf (e.g. kernel.perf_event_paranoid = <setting>)\n\n"
+		 "Also check CONFIG_EXCLUDE_KERNEL_HW_ITRACE if kernel mode tracing is allowed.",
 		 perf_event_paranoid());
 	case ENOENT:
 		return scnprintf(msg, size, "The %s event is not supported.", evsel__name(evsel));
-- 
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