Hi,

I recently came across an Intel statement saying that the "INIT Level 
deassert" IPI used by sync_arb_IDs() (arch/i386/kernel/apic.c) should 
not be used on P4 and Xeon which don't have APIC bus arbitration anyway.

See Intel IA32 architecture software developers manual vol. 3, 8.6.1 
(p.8-23), 8.7 (p. 8.31).

The patch below skips the unsupported IPI on P4/Xeon.

The same thing should probably be done for x86_64.

Regards,
Martin

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