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    SubjectRe: [PATCH] Use x2apic_supported() in the default_apic_id_valid() function.
    On Thu, Mar 15, 2012 at 7:08 PM, Yinghai Lu <> wrote:
    >> So this change breaks the commit
    >> c284b42abadbb22083bfde24d308899c08d44ffa.
    >> I think the right thing is to have two different apid_id_valid checks
    >> one for xapic driver (apic_flat_64.c) and another for x2apic driver
    >> (x2apic_phys/cluster.c) and that way, x2apic MADT entries will be parsed
    >> only if bios has handed over the OS in x2apic mode or if we have
    >> selected the numachip model.
    > that looks like more clear.

    after more thinking, I think We should still use cpu_has_x2apic checking.

    one maybe invalid case:

    System have some cpus apic id < 255, and some cpu apic id > 255.
    BSP apic id < 255.
    those cpus apic id < 255 will be put into xapic mode, cpus > 255 will
    be put into x2apic mode.
    and DMAR table intr-remapping will be working.

    So if we check x2apic_mode early, will skip cpu with apic id > 255,
    even switch to x2apic later.


    Yinghai Lu

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