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    SubjectRe: Problems with EDAC coexisting with BIOS
    On Wed, May 03, 2006 at 09:25:01PM +0100, Tim Small wrote:
    > existing BIOSs, but the EDAC module could reprogram the chipset
    > error-signalling registers, so that an ECC error no longer triggers an

    This is key, I think.

    > SMI. The BIOS SMI handler could then read the signalling registers, and
    > leave the ECC registers well alone if ECC errors are not set to generate
    > an SMI.

    The fundamental problem with SMI is that we CAN'T know what it is doing.
    I've seen systems which trigger SMI from a GPIO toggled by a clock. I've
    seen systems trigger SMI from a chipset-internal periodic timer. I've
    seen chipsets route NMI->SMI or even MCE->SMI. If the BIOS is polling the
    error status registers from a periodic SMI, we're GOING to lose data.

    The big hammer - turn off SMI - is probably OK on some systems, but is not
    a general solution. More and more hardware workarounds and features are
    SMI based. There are some rather interesting things that can be done in
    SMM, *iff* we could get the BIOS out of the way.

    Tim (watching EDAC from time to time, quietly)
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      Last update: 2006-05-03 22:40    [W:0.019 / U:0.396 seconds]
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