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 This could be verified easily on any system post SNB (which do not publish STALLED_CYCLES_FRONTEND): $ ./perf stat -e cycles,ref-cycles true Performance counter stats for 'true': 1,217,348 cycles 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