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    SubjectRe: [PATCH 3/4] x86/ftrace: make ftrace_int3_handler() not to skip fops invocation
    On Mon, Apr 29, 2019 at 05:08:46PM -0700, Sean Christopherson wrote:
    > On Mon, Apr 29, 2019 at 03:22:09PM -0700, Linus Torvalds wrote:
    > > On Mon, Apr 29, 2019 at 3:08 PM Sean Christopherson
    > > <sean.j.christopherson@intel.com> wrote:
    > > >
    > > > FWIW, Lakemont (Quark) doesn't block NMI/SMI in the STI shadow, but I'm
    > > > not sure that counters the "horrible errata" statement ;-). SMI+RSM saves
    > > > and restores STI blocking in that case, but AFAICT NMI has no such
    > > > protection and will effectively break the shadow on its IRET.
    > >
    > > Ugh. I can't say I care deeply about Quark (ie never seemed to go
    > > anywhere), but it's odd. I thought it was based on a Pentium core (or
    > > i486+?). Are you saying those didn't do it either?
    >
    > It's 486 based, but either way I suspect the answer is "yes". IIRC,
    > Knights Corner, a.k.a. Larrabee, also had funkiness around SMM and that
    > was based on P54C, though I'm struggling to recall exactly what the
    > Larrabee weirdness was.

    Aha! Found an ancient comment that explicitly states P5 does not block
    NMI/SMI in the STI shadow, while P6 does block NMI/SMI.

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