Re: [PATCH 3/5] perf, x86: Disable PEBS on clowertown chips

Stephane Eranian
2010-03-05T21:22:13Z

On Fri, Mar 5, 2010 at 1:05 PM, Peter Zijlstra <peterz@infradead.org> wrote:
> On Fri, 2010-03-05 at 20:15 +0100, Peter Zijlstra wrote:
>> On Fri, 2010-03-05 at 10:58 -0800, Stephane Eranian wrote:
>> > >        case 15: /* original 65 nm celeron/pentium/core2/xeon, "Merom"/"Conroe" */
>> > > +               x86_pmu.quirks = intel_clowertown_quirks;
>> >
>> > That's too coarse grain!
>> > It is more subtle than this. Some of the errata are marked as Plan
>> > fix. They seem to be
>> > fixed in later models. Your looking at the E5xxx series errata but the
>> > E7xxx do not have
>> > the same problems.
>>
>> OK, I'll look at those errata again and try to come up with a stepping
>> test for this errata.
>
> The two serious ones, AJ106 and AJ68 are no fix and are listed as such
> in all errata I can find, including the 7[23]00 series.
>
Not E74xx. I think it would be fine to drop LBR with PEBS as the work-around
to AJ106.

> I checked the 65nm Core2Duo, Xeon 5200 and Xeon 7[23]00 spec updates.
> Going by that it seems the full model 15 family is broken and I'll leave
> the patch as is.

But the E74xx are okay and you are excluding them. Worst case you should
provide an override.