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| author | Kan Liang <kan.liang@linux.intel.com> | 2025-04-24 16:47:18 +0300 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2025-04-25 15:55:19 +0300 |
| commit | 7da9960b59fb7e590eb8538c9428db55a4ea2d23 (patch) | |
| tree | 1a72230ecd4aebbd55185837d9e2e6ffba9512bb | |
| parent | e9988ad7b1744991118ac348a804f9395368a284 (diff) | |
| download | linux-7da9960b59fb7e590eb8538c9428db55a4ea2d23.tar.xz | |
perf/x86/intel/ds: Fix counter backwards of non-precise events counters-snapshotting
The counter backwards may be observed in the PMI handler when
counters-snapshotting some non-precise events in the freq mode.
For the non-precise events, it's possible the counters-snapshotting
records a positive value for an overflowed PEBS event. Then the HW
auto-reload mechanism reset the counter to 0 immediately. Because the
pebs_event_reset is cleared in the freq mode, which doesn't set the
PERF_X86_EVENT_AUTO_RELOAD.
In the PMI handler, 0 will be read rather than the positive value
recorded in the counters-snapshotting record.
The counters-snapshotting case has to be specially handled. Since the
event value has been updated when processing the counters-snapshotting
record, only needs to set the new period for the counter via
x86_pmu_set_period().
Fixes: e02e9b0374c3 ("perf/x86/intel: Support PEBS counters snapshotting")
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20250424134718.311934-6-kan.liang@linux.intel.com
| -rw-r--r-- | arch/x86/events/intel/ds.c | 21 |
1 files changed, 19 insertions, 2 deletions
diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c index 18c3ab579b8b..9b20acc0e932 100644 --- a/arch/x86/events/intel/ds.c +++ b/arch/x86/events/intel/ds.c @@ -2379,8 +2379,25 @@ __intel_pmu_pebs_last_event(struct perf_event *event, */ intel_pmu_save_and_restart_reload(event, count); } - } else - intel_pmu_save_and_restart(event); + } else { + /* + * For a non-precise event, it's possible the + * counters-snapshotting records a positive value for the + * overflowed event. Then the HW auto-reload mechanism + * reset the counter to 0 immediately, because the + * pebs_event_reset is cleared if the PERF_X86_EVENT_AUTO_RELOAD + * is not set. The counter backwards may be observed in a + * PMI handler. + * + * Since the event value has been updated when processing the + * counters-snapshotting record, only needs to set the new + * period for the counter. + */ + if (is_pebs_counter_event_group(event)) + static_call(x86_pmu_set_period)(event); + else + intel_pmu_save_and_restart(event); + } } static __always_inline void |