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SubjectRe: [PATCH 2/3] perf/x86/pebs: add workaround for broken OVFL status on HSW
> +		/*
> + * There are cases where, even though, the PEBS ovfl bit is set in
> + * GLOBAL_OVF_STATUS, the PEBS events may also have their overflow bits
> + * set for their counters. We must clear them here because they have
> + * been processed as exact samples in the drain_pebs() routine. They
> + * must not be processed again in the for_each_bit_set() loop for
> + * regular samples below.
> + */
> + status &= ~cpuc->pebs_enabled;
> + status &= x86_pmu.intel_ctrl | GLOBAL_STATUS_TRACE_TOPAPMI;

If you just clear the bits here they will not be acked and stay around
forever in GLOBAL_STATUS, which causes other problems.

You need a separate ack_status variable that contains all bits and is always
acked.

-Andi
--
ak@linux.intel.com -- Speaking for myself only

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