linux-kernel - Re: [PATCH -tip] perf, x86: fix unknown NMIs on a Pentium4 box

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Date:	Fri, 15 Apr 2011 00:18:52 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Don Zickus <dzickus@...hat.com>
CC:	Ingo Molnar <mingo@...e.hu>, Lin Ming <ming.m.lin@...el.com>,
	Shaun Ruffell <sruffell@...ium.com>,
	Maciej Rutecki <maciej.rutecki@...il.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Stephane Eranian <eranian@...gle.com>,
	Robert Richter <robert.richter@....com>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -tip] perf, x86: fix unknown NMIs on a Pentium4 box

On 04/15/2011 12:05 AM, Cyrill Gorcunov wrote:
...
>>
>> I don't think this patch will work.  It would make sense if the unmasking
>> happened _after_ the "if (!handled)" path, but that is not the path Ingo
>> wanted for v1.
> 
> This thing happened if inflight nmi reaches the system and note that inflight
> NMI comes from perf and masks lvt entry, it has nothing to do with "handled" but
> rather the _fact_ that NMI reached apic via LVTPC and as result -- masked it.
> Don, I might be missin something, brain is slowly going to sleep :)
> 

Seems I'm wrong in this assumption, otherwise when this mechanism was
introduced for first time every in-flight nmi catched would block further
perf activity.

>>
>> Cheers,
>> Don
>>

-- 
    Cyrill
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