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

[Jason Xing <kerneljasonxing@gmail.com>]

On Sat, Feb 28, 2026 at 1:03 PM Bui Quang Minh <minhquangbui99@gmail.com> 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@gmail.com> 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@gmail.com>
> >> ---
> >>   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).

Thanks,
Jason