linux-kernel - Re: [PATCH 2/2] perf/x86/intel/pt: Fail event creation if VMX operation is on

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Date:   Wed, 15 Feb 2017 15:09:25 +0200
From:   Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        vince@...ter.net, eranian@...gle.com,
        Arnaldo Carvalho de Melo <acme@...radead.org>,
        Borislav Petkov <bp@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 2/2] perf/x86/intel/pt: Fail event creation if VMX operation is on

Arnaldo Carvalho de Melo <acme@...nel.org> writes:

> Em Wed, Feb 15, 2017 at 10:34:58AM +0200, Alexander Shishkin escreveu:
>> Arnaldo Carvalho de Melo <acme@...nel.org> writes:
>> > Em Tue, Feb 14, 2017 at 03:24:16PM +0200, Alexander Shishkin escreveu:
>> > Yeah, I saw that as well, and Andi told me about this limitation, so,
>> > for quite a while now, everytime I need to test PT on the only machine I
>> > have with it, I have to stop my kvm sessions :-\
>
>> > Thanks for working on this!
>
>> Well, we can't make the limitation go away. You'll still have to stop
>> kvms to get any 'meaningful' PT data.
>
> If we can't make the limitation go away we need to at least warn users
> instead of let 'perf record' sit there doing nothing and then at the end
> return as if everything went well only to when trying to use 'perf
> script' nothing will appear.

I tend to like Peter's idea about PERF_RECORD_AUX with a PAUSED flag to
indicate this.

Regards,
--
Alex