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    SubjectRe: [patch 1/2] x86_64 page fault NMI-safe

    * Linus Torvalds <torvalds@linux-foundation.org> wrote:

    > On Wed, Jul 14, 2010 at 1:17 PM, Mathieu Desnoyers
    > <mathieu.desnoyers@efficios.com> wrote:
    > >
    > > It only handles the case of a single NMI coming in. What happens in this
    > > scenario?
    >
    > [ two nested NMI's ]
    >
    > The _right_ thing happens.
    >
    > What do you think the hardware would have done itself? The NMI was blocked.
    > It wouldn't get replayed twice. If you have two NMI's happening while
    > another NMI is active, you will get a single NMI after the first NMI has
    > completed.

    If it ever became an issue, we could even do what softirqs do and re-execute
    the NMI handler. At least for things like PMU NMIs we have to handle them once
    they have been (re-)issued, or we'd get a stuck PMU.

    But in any case it should be a non-issue.

    Ingo


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