linux-kernel - [PATCH v7 11/13] perf tools: Improve IBS error handling

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Date:   Tue, 22 Mar 2022 15:15:15 -0700
From:   Stephane Eranian <eranian@...gle.com>
To:     linux-kernel@...r.kernel.org
Cc:     peterz@...radead.org, kim.phillips@....com, acme@...hat.com,
        jolsa@...hat.com, songliubraving@...com, rafael@...nel.org,
        ravi.bangoria@....com, sandipan.das@....com
Subject: [PATCH v7 11/13] perf tools: Improve IBS error handling

From: Kim Phillips <kim.phillips@....com>

improve the error message returned on failed perf_event_open() on AMD when
using IBS.

Output of executing 'perf record -e ibs_op// true' BEFORE this patch:

The sys_perf_event_open() syscall returned with 22 (Invalid argument)for event (ibs_op//u).
/bin/dmesg | grep -i perf may provide additional information.

Output after:

AMD IBS cannot exclude kernel events.  Try running at a higher privilege level.

Output of executing 'sudo perf record -e ibs_op// true' BEFORE this patch:

Error:
The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (ibs_op//).
/bin/dmesg | grep -i perf may provide additional information.

Output after:

Error:
AMD IBS may only be available in system-wide/per-cpu mode.  Try using -a, or -C and workload affinity

Signed-off-by: Kim Phillips <kim.phillips@....com>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc: Ian Rogers <irogers@...gle.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Joao Martins <joao.m.martins@...cle.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Michael Petlan <mpetlan@...hat.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Robert Richter <robert.richter@....com>
Cc: Stephane Eranian <eranian@...gle.com>
---
 tools/perf/util/evsel.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 14b0e7ffa2c7..e8ff7a4bd490 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2847,9 +2847,23 @@ static bool find_process(const char *name)
 	return ret ? false : true;
 }
 
+static bool is_amd(const char *arch, const char *cpuid)
+{
+	return arch && !strcmp("x86", arch) && cpuid && strstarts(cpuid, "AuthenticAMD");
+}
+
+static bool is_amd_ibs(struct evsel *evsel)
+{
+	return evsel->core.attr.precise_ip
+	    || (evsel->pmu_name && !strncmp(evsel->pmu_name, "ibs", 3));
+}
+
 int evsel__open_strerror(struct evsel *evsel, struct target *target,
 			 int err, char *msg, size_t size)
 {
+	struct perf_env *env = evsel__env(evsel);
+	const char *arch = perf_env__arch(env);
+	const char *cpuid = perf_env__cpuid(env);
 	char sbuf[STRERR_BUFSIZE];
 	int printed = 0, enforced = 0;
 
@@ -2949,6 +2963,17 @@ int evsel__open_strerror(struct evsel *evsel, struct target *target,
 			return scnprintf(msg, size,
 	"Invalid event (%s) in per-thread mode, enable system wide with '-a'.",
 					evsel__name(evsel));
+		if (is_amd(arch, cpuid)) {
+			if (is_amd_ibs(evsel)) {
+				if (evsel->core.attr.exclude_kernel)
+					return scnprintf(msg, size,
+	"AMD IBS can't exclude kernel events.  Try running at a higher privilege level.");
+				if (!evsel->core.system_wide)
+					return scnprintf(msg, size,
+	"AMD IBS may only be available in system-wide/per-cpu mode.  Try using -a, or -C and workload affinity");
+			}
+		}
+
 		break;
 	case ENODATA:
 		return scnprintf(msg, size, "Cannot collect data source with the load latency event alone. "
-- 
2.35.1.894.gb6a874cedc-goog