Re: [net PATCH v3 3/5] virtio_net: factor out xdp handler for readability

[Jason Wang]

On 2017年01月13日 10:51, John Fastabend wrote:

At this point the do_xdp_prog is mostly if/else branches handling
the different modes of virtio_net. So remove it and handle running
the program in the per mode handlers.

Signed-off-by: John Fastabend <john.r.fastab...@intel.com>
---
  drivers/net/virtio_net.c |   76 +++++++++++++++++-----------------------------
  1 file changed, 28 insertions(+), 48 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 43cb2e0..ec54644 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -388,49 +388,6 @@ static void virtnet_xdp_xmit(struct virtnet_info *vi,
        virtqueue_kick(sq->vq);
  }

[...]

/* This happens when rx buffer size is underestimated */

@@ -598,8 +570,10 @@ static struct sk_buff *receive_mergeable(struct net_device 
*dev,
                if (unlikely(hdr->hdr.gso_type))
                        goto err_xdp;

- act = do_xdp_prog(vi, rq, xdp_prog,

-                                 page_address(xdp_page) + offset, len);
+               data = page_address(xdp_page) + offset;
+               xdp.data = data + desc_room;
+               xdp.data_end = xdp.data + (len - vi->hdr_len);

It looks desc_room is always vi->hdr_len.

+               act = bpf_prog_run_xdp(xdp_prog, &xdp);
                switch (act) {
                case XDP_PASS:
                        /* We can only create skb based on xdp_page. */
@@ -613,13 +587,19 @@ static struct sk_buff *receive_mergeable(struct 
net_device *dev,
                        }
                        break;
                case XDP_TX:
+                       qp = vi->curr_queue_pairs -
+                               vi->xdp_queue_pairs +
+                               smp_processor_id();
+                       virtnet_xdp_xmit(vi, rq, &vi->sq[qp], &xdp, data);
                        ewma_pkt_len_add(&rq->mrg_avg_pkt_len, len);
                        if (unlikely(xdp_page != page))
                                goto err_xdp;
                        rcu_read_unlock();
                        goto xdp_xmit;
-               case XDP_DROP:
                default:
+                       bpf_warn_invalid_xdp_action(act);
+               case XDP_ABORTED:
+               case XDP_DROP:
                        if (unlikely(xdp_page != page))
                                __free_pages(xdp_page, 0);
                        ewma_pkt_len_add(&rq->mrg_avg_pkt_len, len);