[PATCH 2/2] perf tools: Improve IBS error handling

[Kim Phillips <kim.phillips@amd.com>]

This patch improves 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 can't 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@amd.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Joao Martins <joao.m.martins@oracle.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Robert Richter <robert.richter@amd.com>
Cc: Stephane Eranian <eranian@google.com>
---
 tools/perf/util/evsel.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index b915840690d4..f8a9cbd99314 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2743,9 +2743,22 @@ 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 || !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;
 
@@ -2841,6 +2854,17 @@ 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(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. "
-- 
2.31.1