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    SubjectRe: [PATCH] [GIT PULL v2] x86: Workaround for NMI iret woes

    * Steven Rostedt <> wrote:

    > > > + pushq_cfi $repeat_nmi
    > > > +
    > > > + /* Put stack back */
    > > > + addq $(11*8), %rsp
    > This is where we put the stack back to the original position.
    > Is CFI notation really necessary here?

    i'd add it if it's not hard or ugly - in theory we could get a
    #MC exception in that window.

    > > Note that the IRQ return checks are needed because NMI path
    > > can set the irq-work TIF. Might be worth putting into the
    > > comment - NMIs are not *entirely* passive entities.
    > The NMI path can set the TIF flags? Then where should they be
    > processed. There was an assumption that NMIs shouldn't do
    > that. I could have been wrong with that. What work needs to be
    > done and when? This is the change that Linus made. If that's
    > the case, we need to work something else out.

    Hm, you are right, we at most access them (for 32-bit compat
    checks for example) but don't modify them - we have switched to
    using the special irq work self-IPI.

    So the change is fine.

    > > Something like nmi_postprocess_retry_preprocess()?
    > Not sure what would be good, as i386 does the retry, x86_64
    > just switches the idt. The two archs do two different things.
    > The above name would be confusing as it doesn't match what
    > x86_64 does.

    Yeah, that assymetry is bothering me too. I guess we can keep it
    as-is, no strong feelings. The whole thing *feels* fragile.



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