Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api

[Michael S. Tsirkin]

On Thu, May 21, 2009 at 03:08:18PM +0300, Avi Kivity wrote:
> Paul Brook wrote:
>>>>> In any case we need some internal API for this, and qemu_irq looks like
>>>>> a good choice.
>>>>>         
>>>> What do you expect to be using this API?
>>>>       
>>> virtio, emulated devices capable of supporting MSI (e1000?), device
>>> assignment (not yet in qemu.git).
>>>     
>>
>> It probably makes sense to have common infrastructure in pci.c to  
>> expose/implement device side MSI functionality. However I see no need 
>> for a direct API between the device and the APIC. We already have an 
>> API for memory accesses and MMIO regions. I'm pretty sure a system 
>> could implement MSI by pointing the device at system ram, and having 
>> the CPU periodically poll that.
>>   
>
> Instead of writing directly, let's abstract it behind a qemu_set_irq().   
> This is easier for device authors.  The default implementation of the  
> irq callback could write to apic memory, while for kvm we can directly  
> trigger the interrupt via the kvm APIs.

Right.

-- 
MST