[PATCH netdev] virtio-net: support XDP_TX when not more queues
From: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Date: 2021-01-13 08:11:07
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. This patch allows XDP_TX 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> --- drivers/net/virtio_net.c | 47 +++++++++++++++++++++++++++++++++++------------ 1 file changed, 35 insertions(+), 12 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index ba8e637..7a3b2a7 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;
@@ -481,14 +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) +static struct send_queue *virtnet_get_xdp_sq(struct virtnet_info *vi) { unsigned int qp; + struct netdev_queue *txq; + + if (vi->curr_queue_pairs > nr_cpu_ids) { + qp = vi->curr_queue_pairs - vi->xdp_queue_pairs + smp_processor_id(); + } else { + qp = smp_processor_id() % vi->curr_queue_pairs; + txq = netdev_get_tx_queue(vi->dev, qp); + __netif_tx_lock(txq, raw_smp_processor_id()); + } - qp = vi->curr_queue_pairs - vi->xdp_queue_pairs + smp_processor_id(); return &vi->sq[qp]; } +static void virtnet_put_xdp_sq(struct virtnet_info *vi) +{ + unsigned int qp; + struct netdev_queue *txq; + + if (vi->curr_queue_pairs <= nr_cpu_ids) { + qp = smp_processor_id() % vi->curr_queue_pairs; + txq = netdev_get_tx_queue(vi->dev, qp); + __netif_tx_unlock(txq); + } +} + static int virtnet_xdp_xmit(struct net_device *dev, int n, struct xdp_frame **frames, u32 flags) {
@@ -512,7 +535,7 @@ static int virtnet_xdp_xmit(struct net_device *dev, if (!xdp_prog) return -ENXIO; - sq = virtnet_xdp_sq(vi); + sq = virtnet_get_xdp_sq(vi); if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK)) { ret = -EINVAL;
@@ -560,12 +583,13 @@ static int virtnet_xdp_xmit(struct net_device *dev, sq->stats.kicks += kicks; u64_stats_update_end(&sq->stats.syncp); + virtnet_put_xdp_sq(vi); 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 +1481,13 @@ 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_get_xdp_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_put_xdp_sq(vi); } return received;
@@ -2416,12 +2441,8 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog, xdp_qp = nr_cpu_ids; /* 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; - } + if (curr_qp + xdp_qp > vi->max_queue_pairs) + xdp_qp = 0; old_prog = rtnl_dereference(vi->rq[0].xdp_prog); if (!prog && !old_prog)
@@ -2453,12 +2474,14 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog, netif_set_real_num_rx_queues(dev, curr_qp + xdp_qp); vi->xdp_queue_pairs = xdp_qp; + vi->xdp_enabled = false; if (prog) { 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); } + vi->xdp_enabled = true; } for (i = 0; i < vi->max_queue_pairs; i++) {
@@ -2526,7 +2549,7 @@ 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