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    SubjectRe: 2.6.22-rc1 does not boot on VIA C3_2 cause of X86_CMPXCHG64
    Dave Jones wrote:
    > The C3s all have cx8, but it needs to be enabled in an MSR first.
    > (See arch/i386/kernel/cpu/centaur.c , search for CX8)
    > Did we add code that uses cmpxchg8b before identify_cpu() gets run ?
    > I've not been paying attention to .22rc (busy trying to beat .21 into shape for F7)
    > so I may have missed something obvious. Andi?
    > Dave

    May I brought up a wrong reason with the command cmpxchg64.
    But disabling CONFIG_X86_CMPXCHG64 helps.

    The via C3 EBGA datasheet R1.9 tells me this command works always:
    >The CMPXCHG8B instruction is provided and always enabled, however, it appears disabled in the corresponding
    >CPUID function bit 0 to avoid a bug in an early version of Windows NT. However, this default can be changed
    >via a bit in the FCR MSR.

    Hmm, I should be able to add a few small "here I am" to
    the my local boot code with a little hint.

    Anyway I will try tomorrow to find this on my own.
    printfs for debugging are more friendly than assembler.

    H. Peter Anvin wrote:
    > Andi added code to verify that we can actually execute on the processor
    > before protected mode (so we can still get a message out through the
    > BIOS.) That code presumably doesn't know of the MSR that needs to be
    > touched.

    Best regards,

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      Last update: 2007-05-17 03:43    [W:0.020 / U:1.264 seconds]
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