[RFC PATCH net-next 5/5] virtio-net: support XDP rx handler

[Jason Wang <jasowang@redhat.com>]

This patch tries to add the support of XDP rx handler to
virtio-net. This is straight-forward, just call xdp_do_pass() and
behave depends on its return value.

Test was done by using XDP_DROP (xdp1) for macvlan on top of
virtio-net. PPS of SKB mode was ~1.2Mpps while PPS of native XDP mode
was ~2.2Mpps. About 83% improvement was measured.

Notes: for RFC, only mergeable buffer case was implemented.

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 drivers/net/virtio_net.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 62311dd..1e22ad9 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -777,6 +777,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 	rcu_read_lock();
 	xdp_prog = rcu_dereference(rq->xdp_prog);
 	if (xdp_prog) {
+		rx_xdp_handler_result_t ret;
 		struct xdp_frame *xdpf;
 		struct page *xdp_page;
 		struct xdp_buff xdp;
@@ -825,6 +826,15 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 
 		switch (act) {
 		case XDP_PASS:
+			ret = xdp_do_pass(&xdp);
+			if (ret == RX_XDP_HANDLER_DROP)
+				goto drop;
+			if (ret != RX_XDP_HANDLER_FALLBACK) {
+				if (unlikely(xdp_page != page))
+					put_page(page);
+				rcu_read_unlock();
+				goto xdp_xmit;
+			}
 			/* recalculate offset to account for any header
 			 * adjustments. Note other cases do not build an
 			 * skb and avoid using offset
@@ -881,6 +891,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 		case XDP_ABORTED:
 			trace_xdp_exception(vi->dev, xdp_prog, act);
 			/* fall through */
+drop:
 		case XDP_DROP:
 			if (unlikely(xdp_page != page))
 				__free_pages(xdp_page, 0);
-- 
2.7.4