Re: [PATCH RFC] x86/acpi: don't ignore I/O APICs just because there's no local APIC

From: Eric W. Biederman
Date: Thu Jun 18 2009 - 15:27:54 EST

Jeremy Fitzhardinge <jeremy@xxxxxxxx> writes:

> On 06/18/09 09:08, Len Brown wrote:
>>> In principle, the local APIC and the I/O APIC are distinct (but related)
>>> components, which can be independently present.
>> bzzzzt, but thanks for playing:-)
> Perhaps I should have expressed that a bit more clearly: you could, if
> mad, build a machine with I/O APICs and some other mechanism for
> delivering the interrupts to CPUs. In practice, I doubt anyone ever
> has, or ever would.
> The only actual exception I know of is Xen's replacement of the physical
> local APIC with a paravirtualized interrupt interface.

No one ever has. Xen doesn't have I/O APICs either. Not in any real
sense. Xen just has devices that looking like I/O apics if you don't
look close.


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