Re: APIC version and 8-bit APIC IDs

[Martin Wilck <martin.wilck@fujitsu-siemens.com>]

Andi Kleen wrote:

> 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 

on the Intel Xeon MP systems, too,

> 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.

agreed.

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

That is a beautiful patch, thank you.

Only one small point: I wonder whether it is correct to use the number 
of CPUs as criterion for this architecture. AFAICS, the Specs allow
having only 4 CPUS, but giving them APIC IDs e.g. 16,17,18,19. In this 
case, physflat32 should be used as well (in particular, the APIC ID 
broadcast and mask must be set to 0xff).

> Will hopefully be fixed in 2.6.14.

Great,

Martin

-- 
Martin Wilck                Phone: +49 5251 8 15113
Fujitsu Siemens Computers   Fax:   +49 5251 8 20409
Heinz-Nixdorf-Ring 1        mailto:Martin.Wilck@Fujitsu-Siemens.com
D-33106 Paderborn           http://www.fujitsu-siemens.com/primergy