Re: [PATCH] x86: change IO-APIC ack method default for single IO-APIC systems

[Keir Fraser <keir.fraser@eu.citrix.com>]

On 21/01/2009 14:21, "Jan Beulich" <jbeulich@novell.com> wrote:

> "ioapic_ack=old". With that knowledge I think it is now reasonable to
> include that patch in -unstable, as the introduction of the 'new' ack
> method was only to address issues with certain chipsets silently
> setting up alternative IRQ routes when RTEs in secondary IO-APICs got
> masked.

I don't specifically recall that this issue required two IO-APICs. In fact I
think it did not. It was actually something to do with the chipset trying to
distinguish between an OS using 'legacy' routing versus 'mp-bios' routing,
via a rather distasteful IO-APIC hack. Unfortunately the hack was not that
uncommon and I don't think those chipsets had more than one IO-APIC.

Overall I think ack_type new has worked quite well. I was actually about to
remove the old ack_type! (But now I won't ;-) I'm not inclined to take this
patch though.

 -- Keir