Re: APIC version and 8-bit APIC IDs

[Andi Kleen]

Martin Wilck <martin.wilck@xxxxxxxxxxxxxxxxxxx> writes:

> Hi William, hello everyone,
> 
> The MP_valid_apicid() function [arch/i386/kernel/mpparse.c] checks
> whether the APIC version field is >=20 in order to determine whether
> the CPU supports 8-bit physical APIC ids.

Yes, it's broken. In fact I removed it in my physflat32 patch
which is needed for 16 core AMD systems. I don't think there
is a generic way to fix it because the XAPIC check breaks
on AMD systems and there is no good way to decide early 
on subarchitectures before doing this check. Also it's only
a sanity check for broken BIOS, and in this case it causes more problems
than it solves.

ftp://ftp.firstfloor.org/pub/ak/x86_64/x86_64-2.6.13rc3-1/patches/physflat32

Will hopefully be fixed in 2.6.14.

-Andi
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