linux-kernel - Re: [PATCH 1/2] perf: ignore LBR and offcore

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Message-ID: <20140623091952.GP19860@laptop.programming.kicks-ass.net>
Date:	Mon, 23 Jun 2014 11:19:52 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	"Liang, Kan" <kan.liang@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"Kleen, Andi" <andi.kleen@...el.com>
Subject: Re: [PATCH 1/2] perf: ignore LBR and offcore_rsp.

On Thu, Jun 19, 2014 at 10:52:52AM -0700, Andi Kleen wrote:
> Andi Kleen <andi@...stfloor.org> writes:
> >>
> >>>     Signed-off-by: Kan Liang <kan.liang@...el.com>
> >>
> >> And here I thought that Andi was of the opinion that if you set CPUID to
> >> indicate a particular CPU you had better also handle all its MSRs.
> >
> > Yes, philosophically that would be the right way,
> > but we needed a short term fix to stop things from crashing, and that
> > was the simplest.
> 
> I should add there is another reason for this patch now,
> and doing it in perf instead of somewhere else
> (this should probably go into the description).
> 
> With PT on enabling LBR can #GP. So perf needs to handle
> this case without crashing. This can happen independently
> of any hypervisors.

WTH is a PT?
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