Re: [Qemu-devel] [RFC v2 6/8] virtio: flush/push for packed ring

[Maxime Coquelin]

Hi Wei,

On 9/20/18 4:13 PM, Maxime Coquelin wrote:
> >       }
> > @@ -575,6 +630,34 @@ void virtqueue_flush(VirtQueue *vq, unsigned int 
> > count)
> >           vq->signalled_used_valid = false;
> >   }
> > +static void virtqueue_packed_flush(VirtQueue *vq, unsigned int count)
> > +{
> > +    if (unlikely(!vq->vring.desc)) {
> > +        return;
> > +    }
> > +
> > +    vq->inuse -= count;
> > +    vq->used_idx += count;
>
> I think it is wrong, because count seems to be representing the number
> of descriptor chains.
>
> But in case of packed ring layout, used index must be incremented by the
> number of descriptors.
>
> For example, I'm having trouble with the ctrl queue, where the commands
> sent by the guest use 3 descriptors, but count is 1.

It seems you didn't fixed this issue in your last revision.
I guess it works for virtio-net Kernel driver (with the fix you
proposed) in guest because it is using indirect descs.

But Virtio PMD does not use indirect descs for the control vq.

Thanks,
Maxime