linux-kernel - Re: [RFC PATCH 2/3 v3] perf: Implement Nehalem uncore pmu

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Date:	Mon, 13 Dec 2010 17:51:06 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	Lin Ming <ming.m.lin@...el.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andi Kleen <andi@...stfloor.org>, Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Arjan van de Ven <arjan@...radead.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 2/3 v3] perf: Implement Nehalem uncore pmu

> If think there you want something like:
> 
> if (cpu == cpumask_first(topology_core_siblings(cpu)) {
>       rdmsrl(MSR_IA32_DEBUGCTLMSR, val);
>      wrmsrl(MSR_IA32_DEBUGCTLMSR, val | DEBUGCTLMSR_ENABLE_UNCORE_PMI);
> }

You have to be careful with hotplug. The code would need to be rerun
on hotplug. Otherwise the interrupt may end up on a downed CPU.
-Andi
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