Re: [ACPI] Re: [BKPATCH] LAPIC fix for 2.6

[Andi Kleen <ak@suse.de>]

On Sun, Oct 10, 2004 at 05:47:05PM -0700, Linus Torvalds wrote:
> 
> 
> On Sun, 10 Oct 2004, Maciej W. Rozycki wrote:
> > 
> >  Hmm, any particular reason to keep the local APIC disabled by default?  
> 
> Yes. It changes interrupt handling, so any SMM stuff tends to break on
> BIOSes that don't know about APICs. Things like the magic keys etc. It
> apparently also breaks some ACPI stuff (likely AML code that "knows" that
> interrupts are done with the legacy controller).
> 
> Mostly a laptop issue, I suspect - simply because desktops don't do 
> anything strange these days.

It's more than a laptop issue. Especially older desktops still don't
work with APIC by default, and even a lot of modern ones have problems.  

It works around ACPI bugs. Some common issues I ran into on x86-64:
nvidia nforce2/3 is still often broken because of the bogus timer override 
so many BIOS have) 
Some VIA K8 boards get mysterious IDE DMA errors after some time when the APIC 
is on.

[Patch for the Nvidia thing is pending - just always ignore it - but not 
submitted yet for i386 yet. x86-64 has it fixed in -mm*]

-Andi