linux-kernel - Re: [PATCH V6 2/5] perf/x86/kvm: Avoid unnecessary work in guest filtering

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Message-ID: <12e3f6d3-0186-a540-7feb-778f4d78c8cf@linux.intel.com>
Date:   Mon, 4 Feb 2019 15:37:58 -0500
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
        ak@...ux.intel.com, eranian@...gle.com
Subject: Re: [PATCH V6 2/5] perf/x86/kvm: Avoid unnecessary work in guest
 filtering



On 2/4/2019 2:43 PM, Borislav Petkov wrote:
> On Mon, Feb 04, 2019 at 01:57:49PM -0500, Liang, Kan wrote:
>> You mean a given microcode revision X applying to multiple stepping,
>> right?
> 
> Yes, the range thing. You specify a range of steppings:
> 
> kabylake mobile  with steppings 9-12
> kabylake desktop with steppings 10-13
> 
>> I don't think so. I still think the KABYLAKE case is an uncommon case.
> 
> You mean it is uncommon because there are already *two* models which
> need it or because this is only kabylake and it won't happen in the
> future?

The latter.
As you can see in the patch series, for other platforms (from core to 
atom), the microcode revision is always different on different stepping 
of the same model.
I believe the kabylake thing is one off.

> 
>> Can we do something as below just for this case?
> 
> Of course not. _FOUR is just silly and if a *fifth* stepping appears,
> you need to go fixup again.
> 
> If anything and if this kabylake thing is one off, I'd prefer we keep it
> as is.
> 

OK. I will keep it as is on V7.

Thanks,
Kan