On Wed, 19 Jun 2024 17:19:12 -0400, "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote:
> On Thu, Jun 20, 2024 at 12:19:05AM +0800, Heng Qi wrote:
> > @@ -5312,7 +5315,7 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
> >
> > /* Parameters for control virtqueue, if any */
> > if (vi->has_cvq) {
> > - callbacks[total_vqs - 1] = NULL;
> > + callbacks[total_vqs - 1] = virtnet_cvq_done;
> > names[total_vqs - 1] = "control";
> > }
> >
>
> If the # of MSIX vectors is exactly for data path VQs,
> this will cause irq sharing between VQs which will degrade
> performance significantly.
>
> So no, you can not just do it unconditionally.
>
> The correct fix probably requires virtio core/API extensions.
If the introduction of cvq irq causes interrupts to become shared, then
ctrlq need to fall back to polling mode and keep the status quo.
Thanks.
>
> --
> MST
>
