Re: [Qemu-devel] [PATCH 2/2] Route IOAPIC interrupts via ISA bus

[Avi Kivity <avi@redhat.com>]

On 08/26/2009 07:30 PM, Gerd Hoffmann wrote:
> 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 ...

We could change the defaults to include 5, but maybe it makes more sense 
to fix Linux to distribute active PCI IRQs across the resources it has 
at its disposal.

>
>> 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 ...

They'll be slow regardless.  I should be easy to support msi on e1000 
though.

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