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    SubjectRe: [RFC] x86, NMI, Treat unknown NMI as hardware error
    On 05/16/2011 11:03 PM, Don Zickus wrote:
    > On Mon, May 16, 2011 at 09:09:45AM +0800, Huang Ying wrote:
    >>> Ying, the concern is rather related to the code scheme in general. Since
    >>> we have notifiers I think the better way to be consistent here and use
    >>> hwerr notifier too. But it's IMHO ;)
    >> As for go notifiers or not. IMHO, a rule can be:
    >> - If it is something like a driver, than it should go notifier
    >> - If it is architectural/PC defacto standard, it can sit outside of
    >> notifier.
    > Hmm, then what do you do about perf? That is architectural and a defacto
    > standard, but I am not sure hardcoding that would be appropriate.

    Good point!

    >> I think that seeing unknown NMI as hardware error should be part of PC
    >> defacto standard. Do you think so?
    > Well after thinking about it, I would say no. And my reason is, if
    > vendors are really serious about using NMIs as an indicator for hardware
    > errors, shouldn't they be setting a bit in the memory controller/north
    > bridge or south bridge/IOHC for an NMI handler to read? I mean hardware

    UV platform has such bit iirc :)

    > devices don't just get wired directly to the NMI pin on the cpu, right?
    > They generally have to go through some hub that acts as a multiplexer.
    > In those cases, why can't those hubs set a bit saying it detected an error
    > (don't PCIe bridges already do that?) and let the NMI handler read it to
    > confirm. This way we can leave 'unknown NMIs' as a way to say an
    > unclaimed NMI entered the system and we can have users set policy about
    > what to do, panic, printk, whatever.
    > But for the HEST stuff, it should be smart enough by now to trap any
    > hardware error, no? How does a machine that supports HEST let a hardware
    > error get through without detecting it? Isn't that the point? Detect a
    > hardware error, grab as much info about it as possible, save the error
    > record and then panic?
    > Otherwise if you just panic, then you have no idea why the machine errored
    > in the first place. It might be the safe thing to do in some
    > circumstances, but then you have to wonder why the fancy HEST enabled
    > server didn't catch it. Isn't that what people are spending extra money
    > for those Intel servers with RAS features?
    > Cheers,
    > Don


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