This is a note to let you know that I've just added the patch titled
perf/x86: Fix filter_events() bug with event mappings
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
perf-x86-fix-filter_events-bug-with-event-mappings.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 61b87cae6361ea6af161c1ffa549898892707b19 Mon Sep 17 00:00:00 2001
From: Stephane Eranian <eranian@xxxxxxxxxx>
Date: Mon, 7 Dec 2015 20:33:25 +0100
Subject: perf/x86: Fix filter_events() bug with event mappings
From: Stephane Eranian <eranian@xxxxxxxxxx>
commit 61b87cae6361ea6af161c1ffa549898892707b19 upstream.
This patch fixes a bug in the filter_events() function.
The patch fixes the bug whereby if some mappings did not
exist, e.g., STALLED_CYCLES_FRONTEND, then any event after it
in the attrs array would disappear from the published list of
events in /sys/devices/cpu/events. This could be verified
easily on any system post SNB (which do not publish
STALLED_CYCLES_FRONTEND):
$ ./perf stat -e cycles,ref-cycles true
Performance counter stats for 'true':
1,217,348 cycles
<not supported> ref-cycles
The problem is that in filter_events() there is an assumption
that the argument (attrs) is organized in increasing continuous
event indexes related to the event_map(). But if we remove the
non-supported events by shifing the position in the array, then
the lookup x86_pmu.event_map() needs to compensate for it, otherwise
we are looking up the wrong index. This patch corrects this problem
by compensating for the deleted events and with that ref-cycles
reappears (here shown on Haswell):
$ perf stat -e ref-cycles,cycles true
Performance counter stats for 'true':
4,525,910 ref-cycles
1,064,920 cycles
0.002943888 seconds time elapsed
Signed-off-by: Stephane Eranian <eranian@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vince Weaver <vincent.weaver@xxxxxxxxx>
Cc: jolsa@xxxxxxxxxx
Cc: kan.liang@xxxxxxxxx
Fixes: 8300daa26755 ("perf/x86: Filter out undefined events from sysfs events attribute")
Link: http://lkml.kernel.org/r/1449516805-6637-1-git-send-email-eranian@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/cpu/perf_event.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -1550,6 +1550,7 @@ static void __init filter_events(struct
{
struct device_attribute *d;
struct perf_pmu_events_attr *pmu_attr;
+ int offset = 0;
int i, j;
for (i = 0; attrs[i]; i++) {
@@ -1558,7 +1559,7 @@ static void __init filter_events(struct
/* str trumps id */
if (pmu_attr->event_str)
continue;
- if (x86_pmu.event_map(i))
+ if (x86_pmu.event_map(i + offset))
continue;
for (j = i; attrs[j]; j++)
@@ -1566,6 +1567,14 @@ static void __init filter_events(struct
/* Check the shifted attr. */
i--;
+
+ /*
+ * event_map() is index based, the attrs array is organized
+ * by increasing event index. If we shift the events, then
+ * we need to compensate for the event_map(), otherwise
+ * we are looking up the wrong event in the map
+ */
+ offset++;
}
}
Patches currently in stable-queue which might be from eranian@xxxxxxxxxx are
queue-4.4/perf-x86-fix-filter_events-bug-with-event-mappings.patch
