Re: [PATCH 1/2] x86, ioapic: Reserve only 128 bytes for IOAPICs

H. Peter Anvin
2011-08-26T16:24:41Z

On 08/26/2011 09:21 AM, Bjorn Helgaas wrote:
>
> Is there some spec that requires all IOAPICs to be 1K aligned? I
> don't doubt that's the case; I'd just like to see something more
> concrete than folklore. I'm pretty sure there's some (possibly
> secret) "IOAPIC architecture spec," and a section reference to it
> would be nice. Even before my patch, I don't think we actually
> checked or enforced any *alignment* -- we only set the size. I don't
> know if it's worth it unless we have a problem it would fix, and it's
> conceivable that we'd start warning about a perfectly functional
> IOAPIC that's 128-byte aligned.
>

The PIIX3 IOAPIC decoder could only decode addresses on a 1K
granularity, but I don't think that was architectural. I will try to ask.

-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.