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

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Date:	Fri, 8 Jun 2012 11:35:13 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Stephane Eranian <eranian@...gle.com>,
	linux-kernel@...r.kernel.org, andi@...stfloor.org, mingo@...e.hu,
	ming.m.lin@...el.com
Subject: Re: [PATCH] perf/x86: check ucode before disabling PEBS on
 SandyBridge


* Peter Zijlstra <peterz@...radead.org> wrote:

> On Thu, 2012-06-07 at 12:48 +0200, Stephane Eranian wrote:
> > >> The warning could also be done on boot. But the check has to be done
> > >>  when the event is created.
> > >
> > > Is this because of the ucode loader not having done its thing yet etc..?
> 
> Ah, its because you can update ucode at runtime of course.
> 
> A quick look at the ucode loader doesn't show it having a 
> notifier either, so then yeah we need to check on every event 
> creation :/
> 
> Or we could put a hook in the ucode loader.

I'd really suggest the latter - I doubt this will be our only 
ucode dependent quirk, going forward ...

Thanks,

	Ingo
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