[BUG] x2APIC lockup on Dell machines

[khale]

We have a Dell R430 that we're doing some testing on, and when we ran into an issue where we receive a spurious interrupt and the machine locks up in the bootup sequence (just about when interrupts are enabled in init.c).

Curious thing is that when we disable x2APIC mode in the BIOS the issue goes away. Is there possibly some x2APIC/SPIV interaction we're missing here?

[khale]

@PeterDinda have you seen anything like this happen on you guys' hardware?

[PeterDinda]

I have not. It's possible since I wrote the x2apic code to get us on the phi knl that there is something peculiar to it. If it's easy, can you add a dump of the detection code (acpi output)? How APICs are reported in the tables is a bit strange, as I recall.