Jason Wang
2021-Mar-09 02:17 UTC
[PATCH v7 net-next] virtio-net: support XDP when not more queues
On 2021/3/8 4:52 ??, Xuan Zhuo wrote:> The number of queues implemented by many virtio backends is limited, > especially some machines have a large number of CPUs. In this case, it > is often impossible to allocate a separate queue for > XDP_TX/XDP_REDIRECT, then xdp cannot be loaded to work, even xdp does > not use the XDP_TX/XDP_REDIRECT. > > This patch allows XDP_TX/XDP_REDIRECT to run by reuse the existing SQ > with __netif_tx_lock() hold when there are not enough queues. > > Signed-off-by: Xuan Zhuo <xuanzhuo at linux.alibaba.com> > Reviewed-by: Dust Li <dust.li at linux.alibaba.com> > --- > v7: 1. use macros to implement get/put > 2. remove 'flag'. (suggested by Jason Wang) > > v6: 1. use __netif_tx_acquire()/__netif_tx_release(). (suggested by Jason Wang) > 2. add note for why not lock. (suggested by Jason Wang) > 3. Use variable 'flag' to record with or without locked. It is not safe to > use curr_queue_pairs in "virtnet_put_xdp_sq", because it may changed after > "virtnet_get_xdp_sq". > > v5: change subject from 'support XDP_TX when not more queues' > > v4: make sparse happy > suggested by Jakub Kicinski > > v3: add warning when no more queues > suggested by Jesper Dangaard Brouer > > drivers/net/virtio_net.c | 55 ++++++++++++++++++++++++++++++++++++------------ > 1 file changed, 42 insertions(+), 13 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index ba8e637..5ce40ec 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -195,6 +195,9 @@ struct virtnet_info { > /* # of XDP queue pairs currently used by the driver */ > u16 xdp_queue_pairs; > > + /* xdp_queue_pairs may be 0, when xdp is already loaded. So add this. */ > + bool xdp_enabled; > + > /* I like... big packets and I cannot lie! */ > bool big_packets; > > @@ -481,12 +484,34 @@ static int __virtnet_xdp_xmit_one(struct virtnet_info *vi, > return 0; > } > > -static struct send_queue *virtnet_xdp_sq(struct virtnet_info *vi) > -{ > - unsigned int qp; > - > - qp = vi->curr_queue_pairs - vi->xdp_queue_pairs + smp_processor_id(); > - return &vi->sq[qp]; > +/* when vi->curr_queue_pairs > nr_cpu_ids, the txq/sq is only used for xdp tx on > + * the current cpu, so it does not need to be locked. > + */ > +#define virtnet_xdp_get_sq(vi) ({ \ > + struct netdev_queue *txq; \ > + typeof(vi) v = (vi); \Any reason for not using vi directly? Other looks good. Thanks> + unsigned int qp; \ > + if (v->curr_queue_pairs > nr_cpu_ids) { \ > + qp = v->curr_queue_pairs - v->xdp_queue_pairs; \ > + qp += smp_processor_id(); \ > + txq = netdev_get_tx_queue(v->dev, qp); \ > + __netif_tx_acquire(txq); \ > + } else { \ > + qp = smp_processor_id() % v->curr_queue_pairs; \ > + txq = netdev_get_tx_queue(v->dev, qp); \ > + __netif_tx_lock(txq, raw_smp_processor_id()); \ > + } \ > + v->sq + qp; \ > +}) > + > +#define virtnet_xdp_put_sq(vi, q) { \ > + struct netdev_queue *txq; \ > + typeof(vi) v = (vi); \ > + txq = netdev_get_tx_queue(v->dev, (q) - v->sq); \ > + if (v->curr_queue_pairs > nr_cpu_ids) \ > + __netif_tx_release(txq); \ > + else \ > + __netif_tx_unlock(txq); \ > } > > static int virtnet_xdp_xmit(struct net_device *dev, > @@ -512,7 +537,7 @@ static int virtnet_xdp_xmit(struct net_device *dev, > if (!xdp_prog) > return -ENXIO; > > - sq = virtnet_xdp_sq(vi); > + sq = virtnet_xdp_get_sq(vi); > > if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK)) { > ret = -EINVAL; > @@ -560,12 +585,13 @@ static int virtnet_xdp_xmit(struct net_device *dev, > sq->stats.kicks += kicks; > u64_stats_update_end(&sq->stats.syncp); > > + virtnet_xdp_put_sq(vi, sq); > return ret; > } > > static unsigned int virtnet_get_headroom(struct virtnet_info *vi) > { > - return vi->xdp_queue_pairs ? VIRTIO_XDP_HEADROOM : 0; > + return vi->xdp_enabled ? VIRTIO_XDP_HEADROOM : 0; > } > > /* We copy the packet for XDP in the following cases: > @@ -1457,12 +1483,13 @@ static int virtnet_poll(struct napi_struct *napi, int budget) > xdp_do_flush(); > > if (xdp_xmit & VIRTIO_XDP_TX) { > - sq = virtnet_xdp_sq(vi); > + sq = virtnet_xdp_get_sq(vi); > if (virtqueue_kick_prepare(sq->vq) && virtqueue_notify(sq->vq)) { > u64_stats_update_begin(&sq->stats.syncp); > sq->stats.kicks++; > u64_stats_update_end(&sq->stats.syncp); > } > + virtnet_xdp_put_sq(vi, sq); > } > > return received; > @@ -2417,10 +2444,9 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog, > > /* XDP requires extra queues for XDP_TX */ > if (curr_qp + xdp_qp > vi->max_queue_pairs) { > - NL_SET_ERR_MSG_MOD(extack, "Too few free TX rings available"); > - netdev_warn(dev, "request %i queues but max is %i\n", > + netdev_warn(dev, "XDP request %i queues but max is %i. XDP_TX and XDP_REDIRECT will operate in a slower locked tx mode.\n", > curr_qp + xdp_qp, vi->max_queue_pairs); > - return -ENOMEM; > + xdp_qp = 0; > } > > old_prog = rtnl_dereference(vi->rq[0].xdp_prog); > @@ -2454,11 +2480,14 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog, > vi->xdp_queue_pairs = xdp_qp; > > if (prog) { > + vi->xdp_enabled = true; > for (i = 0; i < vi->max_queue_pairs; i++) { > rcu_assign_pointer(vi->rq[i].xdp_prog, prog); > if (i == 0 && !old_prog) > virtnet_clear_guest_offloads(vi); > } > + } else { > + vi->xdp_enabled = false; > } > > for (i = 0; i < vi->max_queue_pairs; i++) { > @@ -2526,7 +2555,7 @@ static int virtnet_set_features(struct net_device *dev, > int err; > > if ((dev->features ^ features) & NETIF_F_LRO) { > - if (vi->xdp_queue_pairs) > + if (vi->xdp_enabled) > return -EBUSY; > > if (features & NETIF_F_LRO) > -- > 1.8.3.1 >