Re: [PATCH 4/5] perf/x86: Change x86_pmu::limit_period signature

[Peter Zijlstra]

On Wed, May 11, 2022 at 01:47:06PM -0400, Liang, Kan wrote:
> > @@ -1386,19 +1387,14 @@ int x86_perf_event_set_period(struct per
> >   		hwc->last_period = period;
> >   		ret = 1;
> >   	}
> > -	/*
> > -	 * Quirk: certain CPUs dont like it if just 1 hw_event is left:
> > -	 */
> > -	if (unlikely(left < 2))
> > -		left = 2;
> > 
> 
> Is the quirk accidentally deleted?
> We should still need the quirk for certain CPUs.

No, but I did forget to write about it in the Changelog :/

IIRC it was Nehalem that triggered that and that should now be covered
by nhm_limit_period().

Or are you aware of more machines that need this?

Anyway, perhaps this should be its own separate commit.