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    Subject[RFD] x86/split_lock: Request to Intel
    The more I look at this trainwreck, the less interested I am in merging any
    of this at all.

    The fact that it took Intel more than a year to figure out that the MSR is
    per core and not per thread is yet another proof that this industry just
    works by pure chance.

    There is a simple way out of this misery:

    Intel issues a microcode update which does:

    1) Convert the OR logic of the AC enable bit in the TEST_CTRL MSR to
    AND logic, i.e. when one thread disables AC it's automatically
    disabled on the core.

    Alternatively it supresses the #AC when the current thread has it
    disabled.

    2) Provide a separate bit which indicates that the AC enable logic is
    actually AND based or that #AC is supressed when the current thread
    has it disabled.

    Which way I don't really care as long as it makes sense.

    If that's not going to happen, then we just bury the whole thing and put it
    on hold until a sane implementation of that functionality surfaces in
    silicon some day in the not so foreseeable future.

    Seriously, this makes only sense when it's by default enabled and not
    rendered useless by VIRT. Otherwise we never get any reports and none of
    the issues are going to be fixed.

    Thanks,

    tglx

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