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    SubjectRe: [PATCH 08/13] xen/pvticketlock: disable interrupts while blocking
    On 09/07/2011 07:52 PM, Don Zickus wrote:
    > >
    > > May I ask how? Detecting a back-to-back NMI?
    > Pretty boring actually. Currently we execute an NMI handler until one of
    > them returns handled. Then we stop. This may cause us to miss an NMI in
    > the case of multiple NMIs at once. Now we are changing it to execute
    > _all_ the handlers to make sure we didn't miss one.

    That's going to be pretty bad for kvm - those handlers become a lot more
    expensive since they involve reading MSRs. Even worse if we start using
    NMIs as a wakeup for pv spinlocks as provided by this patchset.

    > But then the downside
    > here is we accidentally handle an NMI that was latched. This would cause
    > a 'Dazed on confused' message as that NMI was already handled by the
    > previous NMI.
    > We are working on an algorithm to detect this condition and flag it
    > (nothing complicated). But it may never be perfect.
    > On the other hand, what else are we going to do with an edge-triggered
    > shared interrupt line?

    How about, during NMI, save %rip to a per-cpu variable. Handle just one
    cause. If, on the next NMI, we hit the same %rip, assume back-to-back
    NMI has occured and now handle all causes.

    error compiling committee.c: too many arguments to function

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      Last update: 2011-09-07 19:15    [W:0.020 / U:5.488 seconds]
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