perf list: Add explanation about raw hardware event descriptors

Using explanation given by Ingo Molnar in the oprofile mailing list.
Suggested-by: NNick Black <dank@qemfd.net>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Nick Black <dank@qemfd.net>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf-list.txt

@@ -15,6 +15,24 @@ DESCRIPTION
 This command displays the symbolic event types which can be selected in the
 various perf commands with the -e option.
 
+RAW HARDWARE EVENT DESCRIPTOR
+-----------------------------
+Even when an event is not available in a symbolic form within perf right now,
+it can be encoded as <UMASK VALUE><EVENT NUM>, for instance, if the Intel docs
+describe an event as:
+
+  Event  Umask  Event Mask
+  Num.   Value  Mnemonic    Description                        Comment
+
+  A8H      01H  LSD.UOPS    Counts the number of micro-ops     Use cmask=1 and
+                            delivered by loop stream detector  invert to count
+                                                               cycles
+
+raw encoding of 0x1A8 can be used:
+
+ perf stat -e r1a8 -a sleep 1
+ perf record -e r1a8 ...
+
 OPTIONS
 -------
 None

tools/perf/util/parse-events.c

@@ -936,7 +936,7 @@ void print_events(void)
 
 	printf("\n");
 	printf("  %-42s [%s]\n",
-		"rNNN", event_type_descriptors[PERF_TYPE_RAW]);
+		"rNNN (NNN=<UMASK VALUE><EVENT NUM>)", event_type_descriptors[PERF_TYPE_RAW]);
 	printf("\n");
 
 	printf("  %-42s [%s]\n",