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    SubjectRe: [PATCH] Move APIC ID validity check into platform APIC code
    On 3/14/2012 18:58, Yinghai Lu wrote:
    > On Wed, Mar 14, 2012 at 12:17 AM, Daniel J Blueman
    []
    >
    > can you check if you can update
    >
    > !cpu_has_x2apic&& (apic_id>= 0xff)&& enabled
    >
    > in arch/x86/kernel/acpi/boot.c::acpi_parse_x2apic()
    >
    > to use some kind of apic_id_valid()
    >
    > so you could avoid setting that feature bit.
    >
    > the checking in SRAT could be removed.
    >

    Yinghai/Team,

    One question (as I don't really know *why* this was added to the
    acpi/srat parsing code). In arch/x86/kernel/smpboot.c the check was
    originally :

    !x2apic_mode && apicid >= 255

    However in arch/x86/kernel/acpi/boot.c and arch/x86/mm/srat.c these
    tests are used :

    !cpu_has_x2apic && (apic_id >= 0xff)

    Clearly, "cpu_has_x2apic" and "x2apic_mode" are two different things.

    Since we can force "cpu_has_x2apic", when Daniel crafted this patch he
    made the following "default" function :

    static inline int default_apic_id_valid(int apicid)
    {
    return x2apic_mode || (apicid < 255);
    }

    which, as you can see, checks against "x2apic_mode".

    My question is; Is checking for "x2apic_mode" going to do the trick in
    the arch/x86/kernel/acpi/boot.c::acpi_parse_x2apic() ?

    If the answer is yes, the patch is going to be very simple. But we can't
    verify that the code in arch/x86/kernel/acpi/boot.c::acpi_parse_x2apic()
    actually triggers for the case you wanted it to trigger for because then
    it will check against "x2apic_mode" and not "cpu_has_x2apic".

    Cheers,
    --
    Steffen Persvold, Chief Architect NumaChip
    Numascale AS - www.numascale.com
    Tel: +47 92 49 25 54 Skype: spersvold


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