Re: [PATCH -v3] perf, x86: try to handle unknown nmis with running perfctrs

From: Peter Zijlstra <peterz@infradead.org>
To: Robert Richter <robert.richter@amd.com>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>,
	Don Zickus <dzickus@redhat.com>, Ingo Molnar <mingo@elte.hu>,
	Lin Ming <ming.m.lin@intel.com>,
	"fweisbec@gmail.com" <fweisbec@gmail.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"Huang, Ying" <ying.huang@intel.com>,
	Yinghai Lu <yinghai@kernel.org>, Andi Kleen <andi@firstfloor.org>
Subject: Re: [PATCH -v3] perf, x86: try to handle unknown nmis with running perfctrs
Date: Fri, 27 Aug 2010 10:11:21 +0200	[thread overview]
Message-ID: <1282896681.1975.1760.camel@laptop> (raw)
In-Reply-To: <20100827075737.GE22783@erda.amd.com>

On Fri, 2010-08-27 at 09:57 +0200, Robert Richter wrote:
> On 26.08.10 14:02:50, Cyrill Gorcunov wrote:
> > > diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
> > > index 4539b4b..9e65a7b 100644
> > > --- a/arch/x86/kernel/cpu/perf_event_intel.c
> > > +++ b/arch/x86/kernel/cpu/perf_event_intel.c
> > > @@ -777,7 +777,9 @@ again:
> > >  
> > >  done:
> > >  	intel_pmu_enable_all(0);
> > > -	return handled;
> > > +	if (!handled)
> > > +		return handled;
> > > +	return ++handled;
> > >  }
> > >  
> > >  static struct event_constraint *
> > > 
> > 
> > ok, it seems it just treat any unknown nmi as being came from PMU, no?
> 
> Yes, this just throws away all unknown nmis after a perf nmi. It
> disables unknown nmi detection on this cpu type.

Wouldn't returning 2 be more sensible, then it would only eat a few
unknowns after each pmi? (Still assuming you return 0 when there really
was nothing to do)