From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 1/2] perf: ignore LBR and offcore_rsp.
Date: Mon, 23 Jun 2014 11:19:52 +0200
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Cc: "Liang, Kan" <kan.liang@intel.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"Kleen, Andi" <andi.kleen@intel.com>
To: Andi Kleen <andi@firstfloor.org>
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On Thu, Jun 19, 2014 at 10:52:52AM -0700, Andi Kleen wrote:
> Andi Kleen <andi@firstfloor.org> writes:
> >>
> >>>     Signed-off-by: Kan Liang <kan.liang@intel.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?