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

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Message-ID: <CABPqkBQ=tLXXsgvzQx+i01Owm4MM8m=6cEVVi4ab64gOiTTBYQ@mail.gmail.com>
Date:	Thu, 7 Jun 2012 12:48:12 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	Peter Zijlstra <peterz@...radead.org>
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, Jun 7, 2012 at 12:45 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> 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.

Let's keep things simple, move the warning on boot, keep the quiet check
on creation.
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