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    SubjectRe: [V2 PATCH 0/6] x86, NMI: give NMI handler a face-lift
    On Fri, Nov 19, 2010 at 12:01:59AM +0300, Cyrill Gorcunov wrote:
    > On Thu, Nov 18, 2010 at 03:52:03PM -0500, Don Zickus wrote:
    > ...
    > > >
    > > > ok, Don, but you mentioned there are false alarms on real P4 machine, right?
    > >
    > > Yeah, there are two problems. One is using kgdb tests on kvm guests. The
    > > other is using kgdb tests on a bare metal p4 machine.
    > >
    > > Cheers,
    > > Don
    > >
    >
    > ok, thanks, Jason just confirmed it too. I thing if we run with kgdb armed
    > it (kgdb) should obtain nmi handler first and perf only after.
    >
    > actually I'm not sure why p4 hangs here while core passes the test, most

    because p4 reads the wrong high register which comes back zero. This will
    always set overflow=1, thus swallowing all NMI if something like the nmi
    watchdog has perf active.

    Cheers,
    Don


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