1 files changed, 40 insertions, 0 deletions

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 5fc7bd42c803..b4b54d84e9b0 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -1175,11 +1175,51 @@ void perf_evlist__close(struct perf_evlist *evlist)
         }
 }
 
+static int perf_evlist__create_syswide_maps(struct perf_evlist *evlist)
+{
+        int err = -ENOMEM;
+
+        /*
+         * Try reading /sys/devices/system/cpu/online to get
+         * an all cpus map.
+         *
+         * FIXME: -ENOMEM is the best we can do here, the cpu_map
+         * code needs an overhaul to properly forward the
+         * error, and we may not want to do that fallback to a
+         * default cpu identity map :-\
+         */
+        evlist->cpus = cpu_map__new(NULL);
+        if (evlist->cpus == NULL)
+                goto out;
+
+        evlist->threads = thread_map__new_dummy();
+        if (evlist->threads == NULL)
+                goto out_free_cpus;
+
+        err = 0;
+out:
+        return err;
+out_free_cpus:
+        cpu_map__delete(evlist->cpus);
+        evlist->cpus = NULL;
+        goto out;
+}
+
 int perf_evlist__open(struct perf_evlist *evlist)
 {
         struct perf_evsel *evsel;
         int err;
 
+        /*
+         * Default: one fd per CPU, all threads, aka systemwide
+         * as sys_perf_event_open(cpu = -1, thread = -1) is EINVAL
+         */
+        if (evlist->threads == NULL && evlist->cpus == NULL) {
+                err = perf_evlist__create_syswide_maps(evlist);
+                if (err < 0)
+                        goto out_err;
+        }
+
         perf_evlist__update_id_pos(evlist);
 
         evlist__for_each(evlist, evsel) {