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

[Beth Kon <eak@us.ibm.com>]

Avi Kivity wrote:
> On 08/26/2009 07:03 PM, Gerd Hoffmann wrote:
>> On 08/09/09 18:44, Avi Kivity wrote:
>>> Instead of calling the IOAPIC from the PIC, raise IOAPIC irqs via 
>>> the ISA bus.
>>> As a side effect, IOAPIC lines 16-23 are enabled.
>>
>> 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).  Now I don't think it's worthwhile, as every guest 
> that is interesting from a performance point of view has MSI support.
>
> So I think we should just leave these lines as is, terminated with a 
> 4.7K resistor to avoid picking up noise.
>
I was thinking of the HPET advertising one or more of these new ioapic 
interrupts so that it could support non-legacy operation. It can't at 
the moment because there are no interrupt lines available. I haven't 
looked into the details of what would remain to be done to make this 
happen, but does it sound reasonable? Sounds like at a minimum acpi 
needs some work.