linux-kernel - Re: [V5][PATCH 3/6] x86, nmi: wire up NMI handlers to new routines

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Date:	Wed, 21 Sep 2011 10:06:09 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Borislav Petkov <bp@...64.org>
Cc:	Huang Ying <ying.huang@...el.com>,
	"x86@...nel.org" <x86@...nel.org>,
	Andi Kleen <andi@...stfloor.org>,
	Robert Richter <robert.richter@....com>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"paulmck@...ux.vnet.ibm.com" <paulmck@...ux.vnet.ibm.com>,
	"avi@...hat.com" <avi@...hat.com>,
	"jeremy@...p.org" <jeremy@...p.org>,
	Jason Wessel <jason.wessel@...driver.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Corey Minyard <minyard@....org>,
	Jack Steiner <steiner@....com>,
	Alan Cox <alan@...ux.intel.com>,
	Tony Luck <tony.luck@...el.com>
Subject: Re: [V5][PATCH 3/6] x86, nmi: wire up NMI handlers to new routines

On Wed, Sep 21, 2011 at 12:49:36PM +0200, Borislav Petkov wrote:
> + Tony.
> 
> On Wed, Sep 21, 2011 at 01:41:39PM +0800, Huang Ying wrote:
> > On 09/20/2011 10:43 PM, Don Zickus wrote:
> > > Just convert all the files that have an nmi handler to the new routines.
> > > Most of it is straight forward conversion.  A couple of places needed some
> > > tweaking like kgdb which separates the debug notifier from the nmi handler
> > > and mce removes a call to notify_die (as I couldn't figure out why it was
> > > there).
> > 
> > It is used to call a debugger on a machine check, according to following
> > thread:
> > 
> > https://lkml.org/lkml/2010/5/27/114
> 
> Thanks for digging that out - I couldn't find anywhere in the git logs
> why was this added in the first place.
> 
> > So maybe we can turn that into a kgdb direct call?
> 
> After reading the thread, the semi-legitimate usage of using it as
> a jump into the debugger just because some hardware reports certain
> conditions through an MCE sounds pretty hacky to me.
> 
> Besides, if the driver developer needs that, he can add the code for the
> duration of her/his development cycle as aid, and remove it in the end.
> 
> This early-exit deal is especially inacceptable if you get an
> uncorrectable error and some notifier call in the chain consumes it and
> we never get to report it or decode it, or do recovery action. And thus
> the box merrily continues on although a corruption just happened and we
> didn't even get a chance to panic.
> 
> So I really really want to remove it, actually.

Cool.  Thanks Ying and Boris for settling that.  I was scratching my head
trying to understand why that was there.  It keeps the code simpler to
now. :-)

Cheers,
Don
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