linux-kernel - Re: [PATCH 3/4] perf, x86: check ucode before disabling PEBS on SandyBridge v3

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Date:	Wed, 13 Jun 2012 23:36:57 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Andi Kleen <ak@...ux.intel.com>
Cc:	Andi Kleen <andi@...stfloor.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org, eranian@...gle.com
Subject: Re: [PATCH 3/4] perf, x86: check ucode before disabling PEBS on
 SandyBridge v3

On Wed, 2012-06-13 at 14:34 -0700, Andi Kleen wrote:
> > Stephane actually wrote:
> > 
> > "Ok, so to close on this, I tried the 6/6/2012 ucode update on a few
> > SNB-EP systems.
> > 
> > I got two answers depending on the stepping:
> > C1 (stepping 6) -> 0x618
> > C2 (stepping 7) -> 0x70c
> > 
> > So we need to check x86_mask for stepping and adjust the value of
> > snb_ucode_rev accordingly for model 45."
> 
> not sure i understood your point? 
> What do you want me to change?
> 
> I check different numbers on the different models.
> 
> FWIW it works on a Sandy Bridge E and I believe I didn't change
> the logic for non E, which Stephane tested.

Is there a ucode revision for C2 higher than 0x618 but lower than
0x70c ? If so, your code is wrong for it would enable PEBS on that chip.
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