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Message-ID: <1347538265.15764.129.camel@twins>
Subject: Re: [RFC][PATCH] perf, intel: Don't touch MSR_IA32_DEBUGCTLMSR from
 NMI context
From: Peter Zijlstra <peterz@infradead.org>
To: Stephane Eranian <eranian@google.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Oleg Nesterov <oleg@redhat.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@kernel.org>
Date: Thu, 13 Sep 2012 14:11:05 +0200
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On Thu, 2012-09-13 at 13:49 +0200, Stephane Eranian wrote:
> Should be, though it is pretty ugly to stash all of this in the
> put/get constraints.

Agreed, I almost added two extra functions for it but when I went to
look at where to call them I ended up next to get/put constraints.

> I will run some tests.
> 
> I wonder what this does when you come in to get/put with a fake cpuc. You don't
> want to perturb the local lbr which may be in use. 

Fake cpu will never set ->alloc and thus intel_pmu_has_lbr() should fail
and we don't do anything.