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

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Date:	Tue, 12 Jun 2012 10:14:16 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	andi@...stfloor.org, mingo@...e.hu, ming.m.lin@...el.com,
	Andreas Herrmann <andreas.herrmann3@....com>,
	Borislav Petkov <borislav.petkov@....com>,
	Dimitri Sivanich <sivanich@....com>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>
Subject: Re: [PATCH] perf/x86: check ucode before disabling PEBS on SandyBridge

On Fri, Jun 8, 2012 at 4:25 PM, Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Fri, 2012-06-08 at 16:07 +0200, Stephane Eranian wrote:
> > > +static const u32 snb_ucode_rev = 0x28;
> > > +
> >
> > That needs to be a per CPU model value. It
> > is not the same for SNB vs. SNB-EP. On EP
> > it may even depends on stepping.
>
> Yeah, you said, easiest is removing the const and putting some
> assignments to the thing somewhere in our model switch.
>
> Do you know what values for what chip we should use?
>

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.
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