Re: [PATCH v12 38/40] virtio_net: support rx queue resize

[Xuan Zhuo <xuanzhuo@linux.alibaba.com>]

On Mon, 25 Jul 2022 14:57:11 +0800, Jason Wang <jasowang@redhat.com> wrote:
> On Mon, Jul 25, 2022 at 2:43 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
> >
> > On Thu, 21 Jul 2022 17:25:59 +0800, Jason Wang <jasowang@redhat.com> wrote:
> > >
> > > 在 2022/7/20 11:04, Xuan Zhuo 写道:
> > > > This patch implements the resize function of the rx queues.
> > > > Based on this function, it is possible to modify the ring num of the
> > > > queue.
> > > >
> > > > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > > > ---
> > > >   drivers/net/virtio_net.c | 22 ++++++++++++++++++++++
> > > >   1 file changed, 22 insertions(+)
> > > >
> > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > > index fe4dc43c05a1..1115a8b59a08 100644
> > > > --- a/drivers/net/virtio_net.c
> > > > +++ b/drivers/net/virtio_net.c
> > > > @@ -278,6 +278,8 @@ struct padded_vnet_hdr {
> > > >     char padding[12];
> > > >   };
> > > >
> > > > +static void virtnet_rq_free_unused_buf(struct virtqueue *vq, void *buf);
> > > > +
> > > >   static bool is_xdp_frame(void *ptr)
> > > >   {
> > > >     return (unsigned long)ptr & VIRTIO_XDP_FLAG;
> > > > @@ -1846,6 +1848,26 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
> > > >     return NETDEV_TX_OK;
> > > >   }
> > > >
> > > > +static int virtnet_rx_resize(struct virtnet_info *vi,
> > > > +                        struct receive_queue *rq, u32 ring_num)
> > > > +{
> > > > +   int err, qindex;
> > > > +
> > > > +   qindex = rq - vi->rq;
> > > > +
> > > > +   napi_disable(&rq->napi);
> > >
> > >
> > > We need to disable refill work as well. So this series might need
> > > rebasing on top of
> > >
> > > https://lore.kernel.org/netdev/20220704074859.16912-1-jasowang@redhat.com/
> >
> > I understand that your patch is used to solve the situation where dev is
> > destoryed but refill work is running.
> >
> > And is there such a possibility here?
>
> E.g the refill work runs in parallel with this function?

napi_disable enables lock-like functionality. So I think it's safe.

Thanks.

>
> Thanks
>
> > Or is there any other scenario that I'm
> > not expecting?
> >
> > Thanks.
> >
> >
> > >
> > > I will send a new version (probably tomorrow).
> > >
> > > Thanks
> > >
> > >
> > > > +
> > > > +   err = virtqueue_resize(rq->vq, ring_num, virtnet_rq_free_unused_buf);
> > > > +   if (err)
> > > > +           netdev_err(vi->dev, "resize rx fail: rx queue index: %d err: %d\n", qindex, err);
> > > > +
> > > > +   if (!try_fill_recv(vi, rq, GFP_KERNEL))
> > > > +           schedule_delayed_work(&vi->refill, 0);
> > > > +
> > > > +   virtnet_napi_enable(rq->vq, &rq->napi);
> > > > +   return err;
> > > > +}
> > > > +
> > > >   /*
> > > >    * Send command via the control virtqueue and check status.  Commands
> > > >    * supported by the hypervisor, as indicated by feature bits, should
> > >
> >
>