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Commit 7da9960b authored by Kan Liang's avatar Kan Liang Committed by Peter Zijlstra
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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: e02e9b03 ("perf/x86/intel: Support PEBS counters snapshotting")
Signed-off-by: default avatarKan Liang <kan.liang@linux.intel.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20250424134718.311934-6-kan.liang@linux.intel.com
parent e9988ad7
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