From: Xuan Zhuo xuanzhuo@linux.alibaba.com
[ Upstream commit 97c2c69e1926260c78c7f1c0b2c987934f1dc7a1 ]
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@linux.alibaba.com Reviewed-by: Dust Li dust.li@linux.alibaba.com Acked-by: Jason Wang jasowang@redhat.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/virtio_net.c | 62 +++++++++++++++++++++++++++++++--------- 1 file changed, 49 insertions(+), 13 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 7d1f609306f9..a47cf77a0b08 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;
@@ -485,12 +488,41 @@ 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. + * + * Here we use marco instead of inline functions because we have to deal with + * three issues at the same time: 1. the choice of sq. 2. judge and execute the + * lock/unlock of txq 3. make sparse happy. It is difficult for two inline + * functions to perfectly solve these three problems at the same time. + */ +#define virtnet_xdp_get_sq(vi) ({ \ + struct netdev_queue *txq; \ + typeof(vi) v = (vi); \ + 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, @@ -516,7 +548,7 @@ 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; @@ -564,12 +596,13 @@ out: 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: @@ -1473,12 +1506,13 @@ 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; @@ -2453,10 +2487,9 @@ 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); @@ -2490,11 +2523,14 @@ 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++) { @@ -2562,7 +2598,7 @@ 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)