| Message ID | 1615343085-39786-1-git-send-email-xuanzhuo@linux.alibaba.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v8,net-next] virtio-net: support XDP when not more queues | expand |
On Wed, Mar 10, 2021 at 10:24:45AM +0800, 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> > Acked-by: Jason Wang <jasowang@redhat.com> > --- > v8: 1. explain why use macros not inline functions. (suggested by Michael S. Tsirkin) > 2. empty line after variable definitions inside marcos. (suggested by Michael S. Tsirkin) > > 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 | 62 ++++++++++++++++++++++++++++++++++++++---------- > 1 file changed, 49 insertions(+), 13 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 82e520d..ae82e8e 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 +484,41 @@ 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. This comment isn't really helpful :( I did the following and sparse does not seem to complain. diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 2ca4bd2fec94..aee11164bab9 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -486,39 +486,36 @@ static int __virtnet_xdp_xmit_one(struct virtnet_info *vi, /* 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; \ -}) +static inline struct send_queue *virtnet_xdp_get_sq(struct virtnet_info * vi) +{ + struct netdev_queue *txq; + typeof(vi) v = (vi); + unsigned int 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); \ + 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()); + } + return v->sq + qp; +} + +static inline void virtnet_xdp_put_sq(struct virtnet_info * vi, struct send_queue *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, so what is the issue then? > + */ > +#define virtnet_xdp_get_sq(vi) ({ \ > + struct netdev_queue *txq; \ > + typeof(vi) v = (vi); \ It's really always struct virtnet_info *vi isn't it? Better use it as such so it's validated. any local variables in a macro need to have very long names otherwise it can shadow a local variable used in a macro argument. E.g. __virtnet_xdp_get_sq_v. > + unsigned int qp; \ I think it's just a tx queue index ... call it appropriately? > + \ > + 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); \ can curr_queue_pairs change after the call to virtnet_xdp_get_sq? If it does the lock/unlock won't be balanced ... pls add a comment explaining why that can't happen ... or maybe better yet, just return the tx queue number from get and pass it to put? > } > > static int virtnet_xdp_xmit(struct net_device *dev, > @@ -512,7 +544,7 @@ 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 +592,13 @@ 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: > @@ -1458,12 +1491,13 @@ 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; > @@ -2418,10 +2452,9 @@ 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); > @@ -2455,11 +2488,14 @@ 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++) { > @@ -2527,7 +2563,7 @@ 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 82e520d..ae82e8e 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 +484,41 @@ 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, @@ -512,7 +544,7 @@ 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 +592,13 @@ 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: @@ -1458,12 +1491,13 @@ 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; @@ -2418,10 +2452,9 @@ 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); @@ -2455,11 +2488,14 @@ 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++) { @@ -2527,7 +2563,7 @@ 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)