From 1d0a3bfff9f515761ff4e698c817f47c3255d267 Mon Sep 17 00:00:00 2001 From: mengensun Date: Wed, 15 Dec 2021 16:57:13 +0800 Subject: [PATCH] virtio-net: support XDP when not more queues 97c2c69e19 support XDP when not more queues 9ce4e3d6d8 use netdev_warn_once to output warn when without enough queues 3dcc1edcbb reduce raw_smp_processor_id() calling in virtnet_xdp_get_sq [97c2c69e19 desc] 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. [9ce4e3d6d8 disc] This warning is output when virtnet does not have enough queues, but it only needs to be printed once to inform the user of this situation. It is not necessary to print it every time. If the user loads xdp frequently, this log appears too much. [3dcc1edcbb desc] smp_processor_id()/raw* will be called once each when not more queues in virtnet_xdp_get_sq() which is called in non-preemptible context, so it's safe to call the function smp_processor_id() once. Signed-off-by: Li RongQing Signed-off-by: David S. Miller Signed-off-by: Xuan Zhuo Signed-off-by: David S. Miller Signed-off-by: Xuan Zhuo Acked-by: Jason Wang Signed-off-by: David S. Miller Reviewed-by: Dust Li --- drivers/net/virtio_net.c | 63 +++++++++++++++++++++++++++++++--------- 1 file changed, 50 insertions(+), 13 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 5067371c9..9b7c1e6af 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 +484,42 @@ 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; +/* 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) ({ \ + int cpu = smp_processor_id(); \ + 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 += cpu; \ + txq = netdev_get_tx_queue(v->dev, qp); \ + __netif_tx_acquire(txq); \ + } else { \ + qp = cpu % v->curr_queue_pairs; \ + txq = netdev_get_tx_queue(v->dev, qp); \ + __netif_tx_lock(txq, cpu); \ + } \ + v->sq + qp; \ +}) - qp = vi->curr_queue_pairs - vi->xdp_queue_pairs + smp_processor_id(); - return &vi->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 +545,7 @@ 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 +593,13 @@ 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: @@ -1458,12 +1492,13 @@ static int virtnet_poll(struct napi_struct *napi, int budget) xdp_do_flush_map(); 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; @@ -2486,10 +2521,9 @@ 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", - curr_qp + xdp_qp, vi->max_queue_pairs); - return -ENOMEM; + netdev_warn_once(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); + xdp_qp = 0; } old_prog = rtnl_dereference(vi->rq[0].xdp_prog); @@ -2523,11 +2557,14 @@ 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++) { @@ -2612,7 +2649,7 @@ 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)