| Message ID | 1614940150-38458-1-git-send-email-xuanzhuo@linux.alibaba.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v6,net-next] virtio-net: support XDP when not more queues | expand |
On 2021/3/5 6:29 下午, 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@linux.alibaba.com> > Reviewed-by: Dust Li <dust.li@linux.alibaba.com> > --- > 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 | 63 ++++++++++++++++++++++++++++++++++++++++-------- > 1 file changed, 53 insertions(+), 10 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index ba8e637..f9e024d 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 +484,48 @@ 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, int *flag) > + __acquires(txq->_xmit_lock) > { > + struct netdev_queue *txq; > unsigned int qp; > > - qp = vi->curr_queue_pairs - vi->xdp_queue_pairs + smp_processor_id(); > + if (vi->curr_queue_pairs > nr_cpu_ids) { > + qp = vi->curr_queue_pairs - vi->xdp_queue_pairs + smp_processor_id(); > + txq = netdev_get_tx_queue(vi->dev, qp); > + > + /* In this case, this txq is only used for xdp tx on the current > + * cpu, so it does not need to be locked. > + * __netif_tx_acquire is for sparse. > + */ > + __netif_tx_acquire(txq); > + *flag = false; > + } else { > + qp = smp_processor_id() % vi->curr_queue_pairs; > + txq = netdev_get_tx_queue(vi->dev, qp); > + __netif_tx_lock(txq, raw_smp_ƒprocessor_id()); > + *flag = true; > + } > + > return &vi->sq[qp]; Two questions: 1) Can we simply check xdp_queue_paris against 0 then we don't need flag? 2) Can we pass txq to virtnet_get_xdp_sq() then the annotation looks even more better? Thanks > } > > +static void virtnet_put_xdp_sq(struct virtnet_info *vi, struct send_queue *sq, > + int flag) > + __releases(txq->_xmit_lock) > +{ > + struct netdev_queue *txq; > + unsigned int qp; > + > + qp = sq - vi->sq; > + txq = netdev_get_tx_queue(vi->dev, qp); > + > + if (flag) > + __netif_tx_unlock(txq); > + else > + __netif_tx_release(txq); > +} > + > static int virtnet_xdp_xmit(struct net_device *dev, > int n, struct xdp_frame **frames, u32 flags) > { > @@ -496,12 +533,12 @@ static int virtnet_xdp_xmit(struct net_device *dev, > struct receive_queue *rq = vi->rq; > struct bpf_prog *xdp_prog; > struct send_queue *sq; > + int ret, err, sq_flag; > unsigned int len; > int packets = 0; > int bytes = 0; > int drops = 0; > int kicks = 0; > - int ret, err; > void *ptr; > int i; > > @@ -512,7 +549,7 @@ 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, &sq_flag); > > if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK)) { > ret = -EINVAL; > @@ -560,12 +597,13 @@ 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, sq, sq_flag); > 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 +1495,15 @@ static int virtnet_poll(struct napi_struct *napi, int budget) > xdp_do_flush(); > > if (xdp_xmit & VIRTIO_XDP_TX) { > - sq = virtnet_xdp_sq(vi); > + int sq_flag; > + > + sq = virtnet_get_xdp_sq(vi, &sq_flag); > 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, sq, sq_flag); > } > > return received; > @@ -2417,10 +2458,9 @@ 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 +2494,14 @@ 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 +2569,7 @@ 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 >
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index ba8e637..f9e024d 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 +484,48 @@ 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, int *flag) + __acquires(txq->_xmit_lock) { + struct netdev_queue *txq; unsigned int qp; - qp = vi->curr_queue_pairs - vi->xdp_queue_pairs + smp_processor_id(); + if (vi->curr_queue_pairs > nr_cpu_ids) { + qp = vi->curr_queue_pairs - vi->xdp_queue_pairs + smp_processor_id(); + txq = netdev_get_tx_queue(vi->dev, qp); + + /* In this case, this txq is only used for xdp tx on the current + * cpu, so it does not need to be locked. + * __netif_tx_acquire is for sparse. + */ + __netif_tx_acquire(txq); + *flag = false; + } 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()); + *flag = true; + } + return &vi->sq[qp]; } +static void virtnet_put_xdp_sq(struct virtnet_info *vi, struct send_queue *sq, + int flag) + __releases(txq->_xmit_lock) +{ + struct netdev_queue *txq; + unsigned int qp; + + qp = sq - vi->sq; + txq = netdev_get_tx_queue(vi->dev, qp); + + if (flag) + __netif_tx_unlock(txq); + else + __netif_tx_release(txq); +} + static int virtnet_xdp_xmit(struct net_device *dev, int n, struct xdp_frame **frames, u32 flags) { @@ -496,12 +533,12 @@ static int virtnet_xdp_xmit(struct net_device *dev, struct receive_queue *rq = vi->rq; struct bpf_prog *xdp_prog; struct send_queue *sq; + int ret, err, sq_flag; unsigned int len; int packets = 0; int bytes = 0; int drops = 0; int kicks = 0; - int ret, err; void *ptr; int i; @@ -512,7 +549,7 @@ 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, &sq_flag); if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK)) { ret = -EINVAL; @@ -560,12 +597,13 @@ 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, sq, sq_flag); 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 +1495,15 @@ static int virtnet_poll(struct napi_struct *napi, int budget) xdp_do_flush(); if (xdp_xmit & VIRTIO_XDP_TX) { - sq = virtnet_xdp_sq(vi); + int sq_flag; + + sq = virtnet_get_xdp_sq(vi, &sq_flag); 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, sq, sq_flag); } return received; @@ -2417,10 +2458,9 @@ 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 +2494,14 @@ 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 +2569,7 @@ 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)