Re: [PATCH net-next] virtio-net: xsk: Support wakeup on RX side

[Bui Quang Minh]

On 2/28/26 13:16, Jason Xing wrote:
> On Sat, Feb 28, 2026 at 1:03 PM Bui Quang Minh <minhquangbui99@xxxxxxxxx> wrote:
> > Hi Jason,
> >
> > On 2/28/26 10:49, Jason Xing wrote:
> > > Hi Bui,
> > >
> > > On Fri, Feb 27, 2026 at 11:20 PM Bui Quang Minh
> > > <minhquangbui99@xxxxxxxxx> wrote:
> > > > When XDP_USE_NEED_WAKEUP is used and the fill ring is empty so no buffer
> > > > is allocated on RX side, allow RX NAPI to be descheduled. This avoids
> > > > wasting CPU cycles on polling. Users will be notified and they need to
> > > > make a wakeup call after refilling the ring.
> > > >
> > > > Signed-off-by: Bui Quang Minh <minhquangbui99@xxxxxxxxx>
> > > > ---
> > > >    drivers/net/virtio_net.c | 38 ++++++++++++++++++++++++++++++--------
> > > >    1 file changed, 30 insertions(+), 8 deletions(-)
> > > >
> > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > > index db88dcaefb20..494acc904b2c 100644
> > > > --- a/drivers/net/virtio_net.c
> > > > +++ b/drivers/net/virtio_net.c
> > > > @@ -1454,8 +1454,19 @@ static int virtnet_add_recvbuf_xsk(struct virtnet_info *vi, struct receive_queue
> > > >           xsk_buffs = rq->xsk_buffs;
> > > >
> > > >           num = xsk_buff_alloc_batch(pool, xsk_buffs, rq->vq->num_free);
> > > > -       if (!num)
> > > > +       if (!num) {
> > > > +               if (xsk_uses_need_wakeup(pool)) {
> > > > +                       xsk_set_rx_need_wakeup(pool);
> > > > +                       /* Return 0 instead of -ENOMEM so that NAPI is
> > > > +                        * descheduled.
> > > > +                        */
> > > > +                       return 0;
> > > > +               }
> > > > +
> > > >                   return -ENOMEM;
> > > > +       } else {
> > > > +               xsk_clear_rx_need_wakeup(pool);
> > > > +       }
> > > >
> > > >           len = xsk_pool_get_rx_frame_size(pool) + vi->hdr_len;
> > > >
> > > > @@ -1588,20 +1599,21 @@ static bool virtnet_xsk_xmit(struct send_queue *sq, struct xsk_buff_pool *pool,
> > > >           return sent;
> > > >    }
> > > >
> > > > -static void xsk_wakeup(struct send_queue *sq)
> > > > +static void xsk_wakeup(struct napi_struct *napi, struct virtqueue *vq)
> > > >    {
> > > > -       if (napi_if_scheduled_mark_missed(&sq->napi))
> > > > +       if (napi_if_scheduled_mark_missed(napi))
> > > >                   return;
> > > >
> > > >           local_bh_disable();
> > > > -       virtqueue_napi_schedule(&sq->napi, sq->vq);
> > > > +       virtqueue_napi_schedule(napi, vq);
> > > >           local_bh_enable();
> > > >    }
> > > >
> > > >    static int virtnet_xsk_wakeup(struct net_device *dev, u32 qid, u32 flag)
> > > >    {
> > > >           struct virtnet_info *vi = netdev_priv(dev);
> > > > -       struct send_queue *sq;
> > > > +       struct napi_struct *napi;
> > > > +       struct virtqueue *vq;
> > > >
> > > >           if (!netif_running(dev))
> > > >                   return -ENETDOWN;
> > > > @@ -1609,9 +1621,19 @@ static int virtnet_xsk_wakeup(struct net_device *dev, u32 qid, u32 flag)
> > > >           if (qid >= vi->curr_queue_pairs)
> > > >                   return -EINVAL;
> > > >
> > > > -       sq = &vi->sq[qid];
> > > > +       if (flag == XDP_WAKEUP_TX) {
> > > Better use &?
> > Sorry, I don't get your point. Can you elaborate more?
> Oh, I meant using 'flag & XDP_WAKEUP_TX' is preferrable. IIUC, since
> this patch provides a way to enable the RX flag, for virtio_net, this
> flag can be set by TX and RX altogether? Please see this call trace:
> xsk_poll()->xsk_wakeup(xs, pool->cached_need_wakeup).

Oh, you're right. I'll fix it in the next version.

Thanks,
Quang Minh.