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    SubjectRe: [patch 2/2] x86 NMI-safe INT3 and Page Fault
    * Avi Kivity ( wrote:
    > On 07/16/2010 09:05 PM, H. Peter Anvin wrote:
    >>> Module loading can certainly take a vmalloc_sync_all() (though I agree
    >>> it's unpleasant). Anything else?
    >>> Note perf is not modular at this time, but could be made so with
    >>> preempt/sched notifiers to hook the context switch.
    >> Actually, module loading is already a performance problem; a lot of
    >> distros load sometimes hundreds of modules on startup, and it's heavily
    >> serialized, so I can see this being desirable to skip.
    > There aren't that many processes at this time (or there shouldn't be,
    > don't know how fork-happy udev is at this stage), so the sync should be
    > pretty fast. In any case, we can sync only modules that contain NMI
    > handlers.

    USB hotplug is a use-case happening randomly after the system is well there and
    running; I'm afraid this does not fit in your module loading expectations. It
    triggers tons of events, many of these actually load modules.



    >> I really hope noone ever gets the idea of touching user space from an
    >> NMI handler, though, and expecting it to work...
    > I think the concern here is about an NMI handler's code running in
    > vmalloc space, or is it something else?
    > --
    > I have a truly marvellous patch that fixes the bug which this
    > signature is too narrow to contain.

    Mathieu Desnoyers
    Operating System Efficiency R&D Consultant
    EfficiOS Inc.

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