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    SubjectRe: Geode LX boot fails after x86 microcode revision change
    On Tue, Nov 08, 2011 at 02:19:29PM -0800, H. Peter Anvin wrote:
    > > If so, then a family check is unavoidable.
    > Either that, or make changes so that we can handle exceptions earlier.
    > That would be useful for other reasons.

    Well, I did some experimenting with this by forcing a guest to #GP on a
    rdmsr in kvm. What I got was the early_idt_handler's panic message:

    "PANIC: early exception %02lx rip %lx:%lx error %lx cr2 %lx\n"

    because of the following boot code flow:

    |-> ... set_intr_gate /* register early_idt_handler */
    |-> x86_64_start_reservations
    |-> start_kernel
    |-> setup_arch
    |-> early_cpu_init() /*
    * this is where we need the extable for
    * rdmsr_safe
    |-> trap_init() /* switch to default #GP handler */

    and do_general_protection does the actual exception fixup. Now, the
    whole setup_arch() is running with the initial traps and only after we
    finish it and a bunch of other stuff, we switch to the #GP handler in

    From where I stand, maybe I could try to teach the early_idt_handler in
    head_64.S to do fixup_exception() ?

    Also, we might need the patches which sort extable at build time too,
    which are floating around lkml currently.



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