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    SubjectRe: A question of perf NMI handler
    On Wed, Aug 04, 2010 at 12:20:26PM -0400, Don Zickus wrote:
    > > >
    > > > Because the reason registers are never set. If they were, then the code
    > > > wouldn't have to walk the notify_chain. :-)
    > > >
    > >
    > > maybe we're talking about different things. i meant that if there is nmi
    > > with a reason (from 0x61) the handling of such nmi should be done before
    > > notify_die I think (if only I not miss something behind).
    > No we are talking about the same thing. :-) And that code is already

    seems not actually ;)

    > there. The problem is the bits in register 0x61 are not always set
    > correctly in the case of SERRs (well at least in all the cases I have
    > dealt with). So you can easily can a flood of unknown nmis from an SERR
    > and register 0x61 would have the PERR/SERR bits set to 0. Fun, huh?

    if there is nothing in nmi_sc the code flows into another branch. And
    it hits the problem of perf events eating all nmi giving no chance the
    others. So we take if (!(reason & 0xc0)) case and hit DIE_NMI_IPI
    (/me scratching the head why it's not under CONFIG_X86_LOCAL_APIC) and
    drop all code, unpleasant.

    > Cheers,
    > Don
    -- Cyrill

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