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Date: Wed, 26 Aug 2009 18:30:54 +0200
From: Gerd Hoffmann <kraxel@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 2/2] Route IOAPIC interrupts via ISA bus
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To: Avi Kivity <avi@redhat.com>
Cc: qemu-devel@nongnu.org

On 08/26/09 18:06, Avi Kivity wrote:
> On 08/26/2009 07:03 PM, Gerd Hoffmann wrote:
>> Now we probably need some acpi magic to tell the guest OS that there
>> are a few more IRQ lines?
>
> I wanted to route the PCI IRQs to those lines (and have eight links
> instead of four).

Right now we have IRQs 5,10,11 for PCI.  Having one more IRQ (so we have 
one for each link) would be useful IMHO.  eight links + eight irqs would 
be even more useful.  What needs to be done for that?

BTW: Seems linux doesn't use IRQ 5 even with lots of PCI devices, 
instead it makes them share 10+11 ...

> Now I don't think it's worthwhile, as every guest that
> is interesting from a performance point of view has MSI support.

Not all emulated devices have MSI support though ...

> So I think we should just leave these lines as is, terminated with a
> 4.7K resistor to avoid picking up noise.

Oh, nice, didn't know kvm has virtual resistor support.

cheers,
   Gerd