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

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Date:	Thu, 07 Jun 2012 12:45:32 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	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

On Thu, 2012-06-07 at 12:35 +0200, Stephane Eranian wrote:
> > This will only warn about the PEBS issue once you try and use a PEBS
> > counter. Shouldn't we do this on boot? IOW. put check_pebs_quirks()
> > inside the existing quirk code instead of here?
> >
> 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..?

> The other thing is that as it is now, if you
> get an error, you check dmesg and it's obvious what is wrong. With
> the boot warning, you'd have to look back all the way to the early boot
> messages. Whatever you prefer, I am fine. 

We could do both I guess. But the event creation one needs a rate
limiter.
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