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    SubjectRe: [PATCH] x86: provide a DMI based port 0x80 I/O delay override
    David P. Reed wrote:
    > Alan Cox wrote:
    >>> Now what's interesting is that the outb to port 80 is *faster* than
    >>> an outb to an unused port, on my machine. So there's something there
    >>> - actually accepting the bus transaction. In the ancient 5150 PC,
    >>> 80 was
    >>
    >> Yes and I even told you a while back how to verify where it is. From the
    >> timing you get its not on the LPC bus but chipset core so pretty
    >> certainly an SMM trap as other systems with the same chipset don't have
    >> the bug. Probably all that is needed is a BIOS upgrade
    >>
    >>
    > Actually, I could see whether it was SMM trapping due to AMD MSR's that
    > would allow such trapping, performance or debug registers. Nothing was
    > set to trap with SMI or other traps on any port outputs. But I'm
    > continuing to investigate for a cause. It would be nice if it were a
    > BIOS-fixable problem. It would be even nicer if the BIOS were GPL...

    If it was an SMM trap, I would expect it to be trapped in the SuperIO chip.

    -hpa


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