linux-kernel - Re: [RFC 5/6] x86, NMI, Add support to notify hardware error with unknown NMI

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Date:	Mon, 13 Sep 2010 14:23:54 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Huang Ying <ying.huang@...el.com>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC 5/6] x86, NMI, Add support to notify hardware error with
 unknown NMI

On Mon, Sep 13, 2010 at 08:07:07PM +0200, Andi Kleen wrote:
> 
> > 
> > Honestly, I don't think you need much screen real estate.  It would be
> > nice when an unknown NMI comes in, if the kernel just pokes around
> > the hardware registers and display a summary of what it found.  For
> > example,
> > 
> > The following devices had error bits set in the status registers:
> > PCI device x:y.z - STATUS_BIT1 | STATUS_BIT2
> > HW device xyz - STATUS_BIT3
> > ...
> 
> You mean data from the generic PCI config space?

Yes. I normally just look at the Status register.  With PCI-e I'll look at
the other status registers in the capabilities field too.

> 
> I don't think i would feel comfortable with arbitrary driver callbacks
> (the risk of the driver breaking the panic would be high)

Neither would I.

> 
> But if it's generic if not on the screen it should
> be at least in the error serialization data and logged after boot.

I guess I don't know what that is, 'error serialization data'.  Is there
somewhere I can read more about it?

> 
> At least on PCI-E it may be enough to simply dump all recent AER
> data.

This assumes AER is supported on the bridge?  Which for newer chips is
probably true, but I wasn't sure about older ones.

How would I dump AER data from within the kernel?

> 
> > 
> > But I guess if we accept the fact that an unknown NMI will panic the
> > box, then we can probably be a little more liberal in breaking
> > spinlocks and poking around the hardware to display some userful info.
> 
> You have to be a bit careful with that, you may caused nested errors
> (e.g. machine checks or more NMIs). I suppose this could be checked for
> though.

Of course.

Cheers,
Don
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