Linux Virtualization - Dec 2017 - [bpf-next V1-RFC PATCH 11/14] virtio_net: setup xdp_rxq_info

The virtio_net driver doesn't dynamically change the RX-ring queue
layout and backing pages, but instead reject XDP setup if all the
conditions for XDP is not meet.  Thus, the xdp_rxq_info also remains
fairly static.  This allow us to simply add the init+reg/unreg to
net_device open/close functions.

Driver hook points for xdp_rxq_info:
 * init+reg: virtnet_open
 * unreg   : virtnet_close

Cc: "Michael S. Tsirkin" <mst at redhat.com>
Cc: Jason Wang <jasowang at redhat.com>
Cc: virtualization at lists.linux-foundation.org
Signed-off-by: Jesper Dangaard Brouer <brouer at redhat.com>
---
 drivers/net/virtio_net.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 19a985ef9104..9792183befbf 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -31,6 +31,7 @@
 #include <linux/average.h>
 #include <linux/filter.h>
 #include <net/route.h>
+#include <net/xdp.h>
 
 static int napi_weight = NAPI_POLL_WEIGHT;
 module_param(napi_weight, int, 0444);
@@ -115,6 +116,8 @@ struct receive_queue {
 
 	/* Name of this receive queue: input.$index */
 	char name[40];
+
+	struct xdp_rxq_info xdp_rxq;
 };
 
 struct virtnet_info {
@@ -556,6 +559,7 @@ static struct sk_buff *receive_small(struct net_device *dev,
 		xdp.data = xdp.data_hard_start + xdp_headroom;
 		xdp_set_data_meta_invalid(&xdp);
 		xdp.data_end = xdp.data + len;
+		xdp.rxq = &rq->xdp_rxq;
 		orig_data = xdp.data;
 		act = bpf_prog_run_xdp(xdp_prog, &xdp);
 
@@ -1229,6 +1233,13 @@ static int virtnet_open(struct net_device *dev)
 			/* Make sure we have some buffers: if oom use wq. */
 			if (!try_fill_recv(vi, &vi->rq[i], GFP_KERNEL))
 				schedule_delayed_work(&vi->refill, 0);
+
+		/* XDP RX queue info */
+		xdp_rxq_info_init(&vi->rq[i].xdp_rxq);
+		vi->rq[i].xdp_rxq.dev = dev;
+		vi->rq[i].xdp_rxq.queue_index = i;
+		xdp_rxq_info_reg(&vi->rq[i].xdp_rxq);
+
 		virtnet_napi_enable(vi->rq[i].vq, &vi->rq[i].napi);
 		virtnet_napi_tx_enable(vi, vi->sq[i].vq, &vi->sq[i].napi);
 	}
@@ -1557,6 +1568,7 @@ static int virtnet_close(struct net_device *dev)
 	cancel_delayed_work_sync(&vi->refill);
 
 	for (i = 0; i < vi->max_queue_pairs; i++) {
+		xdp_rxq_info_unreg(&vi->rq[i].xdp_rxq);
 		napi_disable(&vi->rq[i].napi);
 		virtnet_napi_tx_disable(&vi->sq[i].napi);
 	}