Re: xen interrupt system

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

On Thu, Aug 20, 2009 at 05:53:45PM +0200, Christoph Egger wrote:
> > > Why are we doing this in first place ?
> > > Disabling ioapics doesn't really sound to be right.
> >
> > Because we don't know the state of the system. So we first
> > disable all interrupt pins, and then reenable the ones we use.
> > Maybe this could be skipped in the Xen case. It's probably worth a try.
> 
> I tried but this alone had no effect.
> 
> During boot, I also have this in serial output:
> [...]
> svwsata0: ServerWorks HT-1000 SATA Controller (rev. 0x00)
> linkdev LNKS returned ACPI global irq 7, line 7
> (XEN) io_apic.c:2292: 
> (XEN) ioapic_guest_write: apic=0, pin=7, old_irq=-1, new_irq=94
> (XEN) ioapic_guest_write: old_entry=00000948, new_entry=0000a95e
> (XEN) ioapic_guest_write: Installing bogus unmasked IO-APIC entry!
> ioapic0: int7 
> 0x1a95e<vector=0x5e,delmode=0x1,logical,actlo,level,masked,dest=0x0> 
> 0xff000000<target=0xff>
> svwsata0: using ioapic0 pin 7, event channel 7 for native-PCI interrupt

We had an active entry for this pin. I guess Xen wants us to mask it
before changing it (but a look in the sources would tell more), this is what
the code in ioapic_attach() tries to do (in fact, it reprograms
the apic from scratch).
The old entry was IOAPIC_REDLO_DSTMOD, IOAPIC_REDLO_DEL_LOPRI and we're
trying to add the IOAPIC_REDLO_ACTLO | IOAPIC_REDLO_LEVEL flags (in
addition to changing the vector). I don't know why Xen says it's invalid,
a look at the sources could give details about this.

-- 
Manuel Bouyer, LIP6, Universite Paris VI.           
Manuel.Bouyer%lip6.fr@localhost
     NetBSD: 26 ans d'experience feront toujours la difference
--