From: Menglong Dong During packet receiving in virtio-net, the rq can be empty, which means "rq->vq->num_free == virtqueue_get_vring_size(rq->vq)", in virtnet_add_recvbuf_xsk(), if we are using xsk. Meanwhile, the fill ring can be empty too, which means we can't allocate anything from xsk_buff_alloc_batch(). Then, we will set the XDP_RING_NEED_WAKEUP flag. However, if the user clean all the data in rx ring and fill the "fill ring" and check the XDP_RING_NEED_WAKEUP flag after xsk_buff_alloc_batch() and before xsk_set_rx_need_wakeup(), then the rx napi will never be scheduled: the rx ring is empty, which means we will never receive a packet to trigger the further recv fill. The rx ring is empty now, so the user will not check the flag too. Fix this by set the XDP_RING_NEED_WAKEUP flag before xsk_buff_alloc_batch() if both rq->vq and fill ring are empty. Meanwhile, set the XDP_RING_NEED_WAKEUP flag if we have any free entry in rq->vq. Fixes: e3f8800aa243 ("virtio-net: xsk: Support wakeup on RX side") Signed-off-by: Menglong Dong --- drivers/net/virtio_net.c | 25 ++++++++++++++++++++++--- 1 file changed, 22 insertions(+), 3 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index f4adcfee7a80..4b5b3fa62008 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -1323,16 +1323,27 @@ static int virtnet_add_recvbuf_xsk(struct virtnet_info *vi, struct receive_queue struct xsk_buff_pool *pool, gfp_t gfp) { struct xdp_buff **xsk_buffs; + bool need_wakeup; dma_addr_t addr; int err = 0; u32 len, i; int num; + need_wakeup = xsk_uses_need_wakeup(pool); xsk_buffs = rq->xsk_buffs; + /* If both rq->vq and fill ring are empty, and then the user submit + * all the chunks to the fill ring and check the wake up flag + * after xsk_buff_alloc_batch() and before xsk_set_rx_need_wakeup(), + * we will lose the chance to wake up the rx napi, so we have to + * set the need_wakeup flag here. + */ + if (need_wakeup && virtqueue_get_vring_size(rq->vq) == rq->vq->num_free) + xsk_set_rx_need_wakeup(pool); + num = xsk_buff_alloc_batch(pool, xsk_buffs, rq->vq->num_free); if (!num) { - if (xsk_uses_need_wakeup(pool)) { + if (need_wakeup) { xsk_set_rx_need_wakeup(pool); /* Return 0 instead of -ENOMEM so that NAPI is * descheduled. @@ -1341,8 +1352,6 @@ static int virtnet_add_recvbuf_xsk(struct virtnet_info *vi, struct receive_queue } return -ENOMEM; - } else { - xsk_clear_rx_need_wakeup(pool); } len = xsk_pool_get_rx_frame_size(pool) + vi->hdr_len; @@ -1363,6 +1372,16 @@ static int virtnet_add_recvbuf_xsk(struct virtnet_info *vi, struct receive_queue goto err; } + if (need_wakeup) { + if (rq->vq->num_free) + /* We have free buffers, so we'd better wake up the + * rx napi as soon as possible. + */ + xsk_set_rx_need_wakeup(pool); + else + xsk_clear_rx_need_wakeup(pool); + } + return num; err: -- 2.54.0