]> www.infradead.org Git - users/jedix/linux-maple.git/commit
perf/x86/intel/ds: Fix counter backwards of non-precise events counters-snapshotting
authorKan Liang <kan.liang@linux.intel.com>
Thu, 24 Apr 2025 13:47:18 +0000 (06:47 -0700)
committerPeter Zijlstra <peterz@infradead.org>
Fri, 25 Apr 2025 12:55:19 +0000 (14:55 +0200)
commit7da9960b59fb7e590eb8538c9428db55a4ea2d23
tree1a72230ecd4aebbd55185837d9e2e6ffba9512bb
parente9988ad7b1744991118ac348a804f9395368a284
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
arch/x86/events/intel/ds.c