linux-kernel - [PATCH v3 11/13] perf tools: improve IBS error handling

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Date:   Tue, 30 Nov 2021 17:02:15 -0800
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, mpe@...erman.id.au,
        maddy@...ux.ibm.com
Subject: [PATCH v3 11/13] perf tools: improve IBS error handling

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

This patch improves the error message returned on failed perf_event_open() on
AMD when using IBS.

Signed-off-by: Kim Phillips <kim.phillips@....com>
---
 tools/perf/util/evsel.c | 42 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index ac0127be0459..39e9063c0a80 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2852,12 +2852,52 @@ static bool find_process(const char *name)
 	return ret ? false : true;
 }
 
+static bool is_amd;
+
+static char *fgrep(FILE *inf, const char *str)
+{
+	char line[256];
+	int slen = strlen(str);
+
+	while (!feof(inf)) {
+		if (!fgets(line, 256, inf))
+			break;
+		if (strncmp(line, str, slen))
+			continue;
+
+		return strdup(line);
+	}
+
+	return NULL;
+}
+
+static void detect_amd(void)
+{
+	FILE *inf = fopen("/proc/cpuinfo", "r");
+	char *res;
+
+	if (!inf)
+		return;
+
+	res = fgrep(inf, "vendor_id");
+
+	if (res) {
+		char *s = strchr(res, ':');
+
+		is_amd = s && !strcmp(s, ": AuthenticAMD\n");
+		free(res);
+	}
+	fclose(inf);
+}
+
 int evsel__open_strerror(struct evsel *evsel, struct target *target,
 			 int err, char *msg, size_t size)
 {
 	char sbuf[STRERR_BUFSIZE];
 	int printed = 0, enforced = 0;
 
+	detect_amd();
+
 	switch (err) {
 	case EPERM:
 	case EACCES:
@@ -2950,6 +2990,8 @@ int evsel__open_strerror(struct evsel *evsel, struct target *target,
 			return scnprintf(msg, size, "wrong clockid (%d).", clockid);
 		if (perf_missing_features.aux_output)
 			return scnprintf(msg, size, "The 'aux_output' feature is not supported, update the kernel.");
+		if (is_amd && (evsel->core.attr.precise_ip || !strncmp(evsel->pmu_name, "ibs", 3)) && (evsel->core.attr.exclude_kernel))
+			return scnprintf(msg, size, "AMD IBS can't exclude kernel events.  Try running at a higher privilege level.");
 		break;
 	case ENODATA:
 		return scnprintf(msg, size, "Cannot collect data source with the load latency event alone. "
-- 
2.34.0.rc2.393.gf8c9666880-goog