Re: xen interrupt system

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Tue, Aug 25, 2009 at 02:34:11PM +0200, Christoph Egger wrote:
> > > > How do we know the "GSI space" ?
> > >
> > > From the MADT ACPI table, IO Apic structure byte offset 8.
> >
> > And if we don't use ACPI ? I have systems where it's not useable.
> 
> a) Update your BIOS to latest version.

I have the latest version.

> 
> b) Not sure how many such systems would have more than one IOAPIC. If there's
> only one IOAPIC then it's easy as its gsi_base will be zero.

The Dell PE1850 have several ioapics for example. 

> 
> > I guess we have something similar in the MPBIOS ?
> > I think we have the GSI in pic_vecbase in NetBSD, but I suspect it's
> > set to -1 when using MPBIOS (from reading the sources).
> 
> The issue of no ACPI is hardly a practical one these days, as there aren't
> really any system made in the last 10+ years with no ACPI.

The PE1850 isn't 10 years old, and yet it has its issues with acpi.

> 
> >
> > Now back to the original question, what does PHYSDEVOP_ASSIGN_VECTOR
> > expects as input ?
> 
> According to Intel, it always expected the GSI number.

Experimentally, it was accepting any number, unless it was a
number already allocated (and some were allocated at boot).
Maybe we can change it to try to use the GSI number when it exists,
hopefully we'll reuse the same number as Xen already used for this pin
and things would work for older hypervisors too.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--