perf evlist: Add evlist__add_dummy_on_all_cpus()

Add evlist__add_dummy_on_all_cpus() to enable creating a system-wide dummy
event that sets up the system-wide maps before map propagation.

For convenience, add evlist__add_aux_dummy() so that the logic can be used
whether or not the event needs to be system-wide.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Ian Rogers <irogers@google.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexey Bayduraev <alexey.v.bayduraev@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Leo Yan <leo.yan@linaro.org>
Link: https://lore.kernel.org/r/20220524075436.29144-6-adrian.hunter@intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/evlist.c

@@ -264,6 +264,51 @@ int evlist__add_dummy(struct evlist *evlist)
 	return 0;
 }
 
+static void evlist__add_on_all_cpus(struct evlist *evlist, struct evsel *evsel)
+{
+	evsel->core.system_wide = true;
+
+	/*
+	 * All CPUs.
+	 *
+	 * Note perf_event_open() does not accept CPUs that are not online, so
+	 * in fact this CPU list will include only all online CPUs.
+	 */
+	perf_cpu_map__put(evsel->core.own_cpus);
+	evsel->core.own_cpus = perf_cpu_map__new(NULL);
+	perf_cpu_map__put(evsel->core.cpus);
+	evsel->core.cpus = perf_cpu_map__get(evsel->core.own_cpus);
+
+	/* No threads */
+	perf_thread_map__put(evsel->core.threads);
+	evsel->core.threads = perf_thread_map__new_dummy();
+
+	evlist__add(evlist, evsel);
+}
+
+struct evsel *evlist__add_aux_dummy(struct evlist *evlist, bool system_wide)
+{
+	struct evsel *evsel = evlist__dummy_event(evlist);
+
+	if (!evsel)
+		return NULL;
+
+	evsel->core.attr.exclude_kernel = 1;
+	evsel->core.attr.exclude_guest = 1;
+	evsel->core.attr.exclude_hv = 1;
+	evsel->core.attr.freq = 0;
+	evsel->core.attr.sample_period = 1;
+	evsel->no_aux_samples = true;
+	evsel->name = strdup("dummy:u");
+
+	if (system_wide)
+		evlist__add_on_all_cpus(evlist, evsel);
+	else
+		evlist__add(evlist, evsel);
+
+	return evsel;
+}
+
 static int evlist__add_attrs(struct evlist *evlist, struct perf_event_attr *attrs, size_t nr_attrs)
 {
 	struct evsel *evsel, *n;

tools/perf/util/evlist.h

@@ -114,6 +114,11 @@ int arch_evlist__add_default_attrs(struct evlist *evlist);
 struct evsel *arch_evlist__leader(struct list_head *list);
 
 int evlist__add_dummy(struct evlist *evlist);
+struct evsel *evlist__add_aux_dummy(struct evlist *evlist, bool system_wide);
+static inline struct evsel *evlist__add_dummy_on_all_cpus(struct evlist *evlist)
+{
+	return evlist__add_aux_dummy(evlist, true);
+}
 
 int evlist__add_sb_event(struct evlist *evlist, struct perf_event_attr *attr,
 			 evsel__sb_cb_t cb, void *data);