Right. The current io-apic code probably doesn't work at all on non-SMP
systems, so you have to compile for UP to make it work.
I'll probably make it default to using the old setup, with a run-time
utility to set up the IO-APIC interrupt handling. That way we won't be
making any mistakes at bootup, so the machine will at least work, and we
can write a small user-level program that parses the PCI irq tables to
find out what the pirq setting should be..
That should also make the SMP kernel boot on an UP machine again.
Linus