perf stat: Tell user about unsupported events in the list

Similar to perf-record, tell user about unsupported events
that will not be counted if invoked in verbose mode.

e.g.,

 $ perf stat -e dTLB-prefetch-misses -v -- sleep 1
 dTLB-prefetch-misses event is not supported by the kernel.
 dTLB-prefetch-misses: 0 0 0

 Performance counter stats for 'sleep 1':

     <not counted> dTLB-prefetch-misses

        1.001884783  seconds time elapsed

Signed-off-by: David Ahern <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

tools/perf/builtin-stat.c

@@ -377,8 +377,12 @@ static int run_perf_stat(int argc __used, const char **argv)
 
 	list_for_each_entry(counter, &evsel_list->entries, node) {
 		if (create_perf_stat_counter(counter) < 0) {
-			if (errno == EINVAL || errno == ENOSYS || errno == ENOENT)
+			if (errno == EINVAL || errno == ENOSYS || errno == ENOENT) {
+				if (verbose)
+					ui__warning("%s event is not supported by the kernel.\n",
+						    event_name(counter));
 				continue;
+			}
 
 			if (errno == EPERM || errno == EACCES) {
 				error("You may not have permission to collect %sstats.\n"