With checkpointed counters there can be a situation where the counter
is overflowing, aborts the transaction, is set back to a non overflowing
checkpoint, causes interupt. The interrupt doesn't see the overflow
because it has been checkpointed. This is then a spurious PMI, typically with
a ugly NMI message. It can also lead to excessive aborts.
Avoid this problem by:
- Using the full counter width for counting counters (earlier patch)
- Forbid sampling for checkpointed counters. It's not too useful anyways,
checkpointing is mainly for counting. The check is approximate
(to still handle KVM), but should catch the majority of cases.
- On a PMI always set back checkpointed counters to zero.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1378438661-24765-2-git-send-email-andi@firstfloor.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2dbf0116aa