Re: [PATCH RFC 0/8] virtio: add guest MSI-X support

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Apr 28, 2009 at 08:51:08PM +0300, Avi Kivity wrote:
> Michael S. Tsirkin wrote:
>> This does not work for MSIX - in linux, you must map all MSI-X entries
>> to interrupt vectors upfront.
>>   
>
> What?  that's very inflexible.
>
> Can you point me at the code?

See pci_enable_msix in include/linux/pci.h

>> So what I see is transports providing something like:
>>
>> struct virtio_interrupt_mapping {
>> 	int virtqueue;
>> 	int interrupt;
>> };
>>
>> map_vqs_to_interrupt(dev, struct virtio_interrupt_mapping *, int nvirtqueues);
>> unmap_vqs(dev);
>>   
>
> Isn't that the same thing?  Please explain the flow.

So to map vq 0 to vector 0, vq 1 to vector 1 and vq 2 to vector 2 the driver would do:

struct virtio_interrupt_mapping mapping[3] = { {0, 0}, {1, 1}, {2, 2} };
vec = map_vqs_to_interrupt(dev, mapping, 3);
if (vec) {
  error handling
}

and then find_vq as usual.

-- 
MST