linux-kernel - Re: [PATCH] x86: fix duplicate calls of the nmi handler

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Date:	Fri, 17 Sep 2010 08:13:16 +0800
From:	Huang Ying <ying.huang@...el.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Robert Richter <robert.richter@....com>,
	Ingo Molnar <mingo@...e.hu>, Don Zickus <dzickus@...hat.com>,
	"gorcunov@...il.com" <gorcunov@...il.com>,
	"fweisbec@...il.com" <fweisbec@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Lin, Ming M" <ming.m.lin@...el.com>,
	"yinghai@...nel.org" <yinghai@...nel.org>,
	"andi@...stfloor.org" <andi@...stfloor.org>,
	"eranian@...gle.com" <eranian@...gle.com>
Subject: Re: [PATCH] x86: fix duplicate calls of the nmi handler

On Fri, 2010-09-17 at 01:42 +0800, Peter Zijlstra wrote:
> On Fri, 2010-09-10 at 17:56 +0200, Robert Richter wrote:
> > The commit:
> > 
> >  e40b172 x86: Move notify_die from nmi.c to traps.c
> > 
> > moved the nmi handler call to default_do_nmi(). DIE_NMI_IPI and
> > DIE_NMI are called subsequently now. If the return code is
> > !NOTIFY_STOP, then the handlers are called twice. This patch fixes
> > this. 
> 
> What is this NMI_IPI thing, and why do we bother?
> 
> If the hardware reason thin can discriminate between IPI and other NMIs
> we should never call both chains, if it cannot, why do we have 2 chains?
> 
> In any case, I don't think perf/oprofile/etc,. should use NMI_IPI, that
> doesn't really make sense.
> 
> Or am I totally confused about things here?

Please take a look at my recent patch that rewrites the NMI handler.
Where NMI are divided into two types. CPU specific NMI are processed
firstly as DIE_NMI_IPI, and non-CPU specific NMI are processed as
DIE_NMI.

CPU specific NMIs include perf event, oprofile, crash, etc. They can be
processed on specific CPU only.

non-CPU specific NMIs include SERR and IOCHK NMI (via checking port
0x61) and APEI GHES NMI. They can be processed on any CPU.

Best Regards,
Huang Ying


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