On 2018年01月24日 00:03, Samudrala, Sridhar wrote:
On 1/23/2018 2:33 AM, Jason Wang wrote:
On 2018年01月12日 13:58, Sridhar Samudrala wrote:
static netdev_tx_t start_xmit(struct sk_buff *skb, struct
net_device *dev)
{
struct virtnet_info *vi = netdev_priv(dev);
int qnum = skb_get_queue_mapping(skb);
struct send_queue *sq = &vi->sq[qnum];
+ struct net_device *vf_netdev;
int err;
struct netdev_queue *txq = netdev_get_tx_queue(dev, qnum);
bool kick = !skb->xmit_more;
bool use_napi = sq->napi.weight;
+ /* If VF is present and up then redirect packets
+ * called with rcu_read_lock_bh
+ */
+ vf_netdev = rcu_dereference_bh(vi->vf_netdev);
+ if (vf_netdev && netif_running(vf_netdev) &&
+ !netpoll_tx_running(dev) &&
+ is_unicast_ether_addr(eth_hdr(skb)->h_dest))
+ return virtnet_vf_xmit(dev, vf_netdev, skb);
+
A question here.
If I read the code correctly, all features were validated against
virtio instead VF before transmitting. This assumes VF's feature is a
superset of virtio, does this really work? Do we need to sanitize the
feature before joining? (e.g at last NETIF_R_GSO_ROBUST needs to be
removed).
Actually, virtnet_vf_xmit() calls dev_queue_xmit() after updating
skb->dev to vf netdev.
So the features get validated against VF features and the right tx
queue is selected
before the real transmit.
I see, the the packet will go through qdiscs twice which is suboptimal.
And the device may lose some ability of VF like tunnel GSO.
Thanks
Thanks
Sridhar
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