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    SubjectRe: [patch 2/2] x86 NMI-safe INT3 and Page Fault
    On Fri, Jul 16, 2010 at 3:07 PM, Andi Kleen <> wrote:
    > One issue I have with nesting NMIs is that you need
    > a nesting limit, otherwise you'll overflow the NMI stack.

    Have you actually looked at the suggestion I (and now Mathieu)
    suggested code for?

    The nesting is very limited. NMI's would nest just once, and when that
    happens, the nested NMI would never use more than something like a
    hundred bytes of stack (most of which is what the CPU pushes
    directly). And there would be no device interrupts that nest, and
    practically the faults that nest obviously aren't going to be complex
    faults either (ie the page fault would be the simple case that never
    calls to 'handle_vm_fault()', but handles it all in

    IOW, there is absolutely _no_ issues with nesting. It's two levels
    deep, and a much smaller stack footprint than our regular exception
    nesting for those two levels too.

    And your argument that there would be more and more NMI usage only
    makes it more important that we handle NMI's without going crazy. Just
    handle them cleanly instead of making them something totally special.


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