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

Don Zickus
2010-09-13T18:24:08Z

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