x86/perf/amd: Remove need to check "running" bit in NMI handler

x86/perf/amd: Remove need to check "running" bit in NMI handler

Spurious interrupt support was added to perf in the following commit, almost
a decade ago:

  63e6be6d98e1 ("perf, x86: Catch spurious interrupts after disabling counters")

The two previous patches (resolving the race condition when disabling a
PMC and NMI latency mitigation) allow for the removal of this older
spurious interrupt support.

Currently in x86_pmu_stop(), the bit for the PMC in the active_mask bitmap
is cleared before disabling the PMC, which sets up a race condition. This
race condition was mitigated by introducing the running bitmap. That race
condition can be eliminated by first disabling the PMC, waiting for PMC
reset on overflow and then clearing the bit for the PMC in the active_mask
bitmap. The NMI handler will not re-enable a disabled counter.

If x86_pmu_stop() is called from the perf NMI handler, the NMI latency
mitigation support will guard against any unhandled NMI messages.

Signed-off-by: Tom Lendacky <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: <[email protected]> # 4.14.x-
Cc: Alexander Shishkin <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vince Weaver <[email protected]>
Link: https://lkml.kernel.org/r/Message-ID:
Signed-off-by: Ingo Molnar <[email protected]>