Message-ID: <20251031212103.310683-3-daniel@iogearbox.net>
Date: Fri, 31 Oct 2025 22:20:51 +0100
From: Daniel Borkmann <daniel@...earbox.net>
To: netdev@...r.kernel.org
Cc: bpf@...r.kernel.org,
	kuba@...nel.org,
	davem@...emloft.net,
	razor@...ckwall.org,
	pabeni@...hat.com,
	willemb@...gle.com,
	sdf@...ichev.me,
	john.fastabend@...il.com,
	martin.lau@...nel.org,
	jordan@...fe.io,
	maciej.fijalkowski@...el.com,
	magnus.karlsson@...el.com,
	dw@...idwei.uk,
	toke@...hat.com,
	yangzhenze@...edance.com,
	wangdongdong.6@...edance.com
Subject: [PATCH net-next v4 02/14] net: Implement netdev_nl_bind_queue_doit

From: David Wei <dw@...idwei.uk>

Implement netdev_nl_bind_queue_doit() that creates an rx queue in a
virtual netdev and then binds it to an rxq in a real netdev to create
a queue pair.

Example with ynl client:

  # ./pyynl/cli.py \
      --spec ~/netlink/specs/netdev.yaml \
      --do bind-queue \
      --json '{"src-ifindex": 4, "src-queue-id": 15, "dst-ifindex": 8, "queue-type": "rx"}'
  {'dst-queue-id': 1}

Note that the netdevice locking order is always from the virtual to
the physical device.

Signed-off-by: David Wei <dw@...idwei.uk>
Co-developed-by: Daniel Borkmann <daniel@...earbox.net>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Reviewed-by: Nikolay Aleksandrov <razor@...ckwall.org>
---
 include/net/netdev_queues.h   |   7 ++
 include/net/netdev_rx_queue.h |  38 ++++++++-
 net/core/dev.h                |   7 ++
 net/core/netdev-genl.c        | 150 +++++++++++++++++++++++++++++++++-
 net/core/netdev_rx_queue.c    |  63 ++++++++++++++
 5 files changed, 262 insertions(+), 3 deletions(-)

diff --git a/include/net/netdev_queues.h b/include/net/netdev_queues.h
index cd00e0406cf4..67e89710577f 100644
--- a/include/net/netdev_queues.h
+++ b/include/net/netdev_queues.h
@@ -130,6 +130,11 @@ void netdev_stat_queue_sum(struct net_device *netdev,
  * @ndo_queue_get_dma_dev: Get dma device for zero-copy operations to be used
  *			   for this queue. Return NULL on error.
  *
+ * @ndo_queue_create: Create a new RX queue which can be bound to another queue.
+ *		      Ops on this queue are redirected to the peer queue e.g.
+ *		      when opening a memory provider. On success, the new queue
+ *		      id is stored into idx.
+ *
  * Note that @ndo_queue_mem_alloc and @ndo_queue_mem_free may be called while
  * the interface is closed. @ndo_queue_start and @ndo_queue_stop will only
  * be called for an interface which is open.
@@ -149,6 +154,8 @@ struct netdev_queue_mgmt_ops {
 						  int idx);
 	struct device *		(*ndo_queue_get_dma_dev)(struct net_device *dev,
 							 int idx);
+	int			(*ndo_queue_create)(struct net_device *dev,
+						    int *idx);
 };
 
 bool netif_rxq_has_unreadable_mp(struct net_device *dev, int idx);
diff --git a/include/net/netdev_rx_queue.h b/include/net/netdev_rx_queue.h
index 8cdcd138b33f..3a02d47e42bc 100644
--- a/include/net/netdev_rx_queue.h
+++ b/include/net/netdev_rx_queue.h
@@ -28,6 +28,8 @@ struct netdev_rx_queue {
 #endif
 	struct napi_struct		*napi;
 	struct pp_memory_provider_params mp_params;
+	struct netdev_rx_queue		*peer;
+	netdevice_tracker		peer_tracker;
 } ____cacheline_aligned_in_smp;
 
 /*
@@ -56,6 +58,38 @@ get_netdev_rx_queue_index(struct netdev_rx_queue *queue)
 	return index;
 }
 
-int netdev_rx_queue_restart(struct net_device *dev, unsigned int rxq);
+static inline void __netdev_rx_queue_peer(struct netdev_rx_queue *src_rxq,
+					  struct netdev_rx_queue *dst_rxq)
+{
+	WRITE_ONCE(src_rxq->peer, dst_rxq);
+	WRITE_ONCE(dst_rxq->peer, src_rxq);
+}
 
-#endif
+static inline void __netdev_rx_queue_unpeer(struct netdev_rx_queue *src_rxq,
+					    struct netdev_rx_queue *dst_rxq)
+{
+	WRITE_ONCE(src_rxq->peer, NULL);
+	WRITE_ONCE(dst_rxq->peer, NULL);
+}
+
+static inline bool netdev_rx_queue_peered(struct net_device *dev,
+					  u16 queue_id)
+{
+	if (queue_id < dev->real_num_rx_queues)
+		return dev->_rx[queue_id].peer;
+	return false;
+}
+
+void netdev_rx_queue_peer(struct net_device *src_dev,
+			  struct netdev_rx_queue *src_rxq,
+			  struct netdev_rx_queue *dst_rxq);
+void netdev_rx_queue_unpeer(struct net_device *src_dev,
+			    struct netdev_rx_queue *src_rxq,
+			    struct netdev_rx_queue *dst_rxq);
+int netdev_rx_queue_restart(struct net_device *dev, unsigned int rxq);
+struct netdev_rx_queue *
+netif_get_rx_queue_peer_locked(struct net_device **dev,
+			       unsigned int *rxq_idx);
+void netif_put_rx_queue_peer_locked(struct net_device *orig_dev,
+				    struct net_device *dev);
+#endif /* _LINUX_NETDEV_RX_QUEUE_H */
diff --git a/net/core/dev.h b/net/core/dev.h
index 900880e8b5b4..321529477b38 100644
--- a/net/core/dev.h
+++ b/net/core/dev.h
@@ -35,6 +35,13 @@ struct net_device *
 netdev_xa_find_lock(struct net *net, struct net_device *dev,
 		    unsigned long *index);
 
+static inline struct net_device *netdev_put_lock(struct net_device *dev,
+						 netdevice_tracker *tracker)
+{
+	netdev_tracker_free(dev, tracker);
+	return __netdev_put_lock(dev, dev_net(dev));
+}
+
 DEFINE_FREE(netdev_unlock, struct net_device *, if (_T) netdev_unlock(_T));
 
 #define for_each_netdev_lock_scoped(net, var_name, ifindex)		\
diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
index ce1018ea390f..4fa7e881441f 100644
--- a/net/core/netdev-genl.c
+++ b/net/core/netdev-genl.c
@@ -1122,7 +1122,155 @@ int netdev_nl_bind_tx_doit(struct sk_buff *skb, struct genl_info *info)
 
 int netdev_nl_bind_queue_doit(struct sk_buff *skb, struct genl_info *info)
 {
-	return -EOPNOTSUPP;
+	struct netdev_rx_queue *src_rxq, *dst_rxq, *tmp_rxq;
+	u32 src_ifidx, src_qid, dst_ifidx, dst_qid, q_type;
+	struct net_device *src_dev, *dst_dev;
+	netdevice_tracker dev_tracker;
+	struct sk_buff *rsp;
+	int err = 0;
+	void *hdr;
+
+	if (GENL_REQ_ATTR_CHECK(info, NETDEV_A_QUEUE_PAIR_QUEUE_TYPE) ||
+	    GENL_REQ_ATTR_CHECK(info, NETDEV_A_QUEUE_PAIR_SRC_IFINDEX) ||
+	    GENL_REQ_ATTR_CHECK(info, NETDEV_A_QUEUE_PAIR_SRC_QUEUE_ID) ||
+	    GENL_REQ_ATTR_CHECK(info, NETDEV_A_QUEUE_PAIR_DST_IFINDEX))
+		return -EINVAL;
+
+	src_ifidx = nla_get_u32(info->attrs[NETDEV_A_QUEUE_PAIR_SRC_IFINDEX]);
+	src_qid = nla_get_u32(info->attrs[NETDEV_A_QUEUE_PAIR_SRC_QUEUE_ID]);
+	dst_ifidx = nla_get_u32(info->attrs[NETDEV_A_QUEUE_PAIR_DST_IFINDEX]);
+	q_type = nla_get_u32(info->attrs[NETDEV_A_QUEUE_PAIR_QUEUE_TYPE]);
+
+	if (q_type != NETDEV_QUEUE_TYPE_RX) {
+		NL_SET_ERR_MSG(info->extack, "Only binding of RX queue supported");
+		return -EOPNOTSUPP;
+	}
+	if (dst_ifidx == src_ifidx) {
+		NL_SET_ERR_MSG(info->extack,
+			       "Destination driver cannot be same as source driver");
+		return -EOPNOTSUPP;
+	}
+
+	rsp = genlmsg_new(GENLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!rsp)
+		return -ENOMEM;
+
+	hdr = genlmsg_iput(rsp, info);
+	if (!hdr) {
+		err = -EMSGSIZE;
+		goto err_genlmsg_free;
+	}
+
+	/* Locking order is always from the virtual to the physical device
+	 * since this is also the same order when applications open the
+	 * memory provider later on.
+	 */
+	dst_dev = netdev_get_by_index_lock(genl_info_net(info), dst_ifidx);
+	if (!dst_dev) {
+		err = -ENODEV;
+		goto err_genlmsg_free;
+	}
+	if (dst_dev->dev.parent) {
+		err = -EOPNOTSUPP;
+		NL_SET_ERR_MSG(info->extack,
+			       "Destination device is not a virtual device");
+		goto err_unlock_dst_dev;
+	}
+	if (!dst_dev->queue_mgmt_ops ||
+	    !dst_dev->queue_mgmt_ops->ndo_queue_create) {
+		err = -EOPNOTSUPP;
+		NL_SET_ERR_MSG(info->extack,
+			       "Destination driver does not support queue management operations");
+		goto err_unlock_dst_dev;
+	}
+	if (dst_dev->real_num_rx_queues < 1) {
+		err = -EOPNOTSUPP;
+		NL_SET_ERR_MSG(info->extack,
+			       "Destination device must have at least one real RX queue");
+		goto err_unlock_dst_dev;
+	}
+
+	src_dev = netdev_get_by_index(genl_info_net(info), src_ifidx,
+				      &dev_tracker, GFP_KERNEL);
+	if (!src_dev) {
+		err = -ENODEV;
+		goto err_unlock_dst_dev;
+	}
+	if (!src_dev->dev.parent) {
+		err = -EOPNOTSUPP;
+		NL_SET_ERR_MSG(info->extack,
+			       "Source device is a virtual device");
+		goto err_unlock_dst_dev_src_dev_put;
+	}
+	if (!netif_device_present(src_dev)) {
+		err = -ENODEV;
+		NL_SET_ERR_MSG(info->extack,
+			       "Source device has been removed from the system");
+		goto err_unlock_dst_dev_src_dev_put;
+	}
+	if (!src_dev->queue_mgmt_ops) {
+		err = -EOPNOTSUPP;
+		NL_SET_ERR_MSG(info->extack,
+			       "Source driver does not support queue management operations");
+		goto err_unlock_dst_dev_src_dev_put;
+	}
+
+	src_dev = netdev_put_lock(src_dev, &dev_tracker);
+	if (!src_dev) {
+		err = -ENODEV;
+		goto err_unlock_dst_dev;
+	}
+	if (src_qid >= src_dev->real_num_rx_queues) {
+		err = -ERANGE;
+		NL_SET_ERR_MSG(info->extack,
+			       "Source device queue is out of range");
+		goto err_unlock_src_dev;
+	}
+
+	src_rxq = __netif_get_rx_queue(src_dev, src_qid);
+	if (src_rxq->peer) {
+		err = -EBUSY;
+		NL_SET_ERR_MSG(info->extack,
+			       "Source device queue is already bound");
+		goto err_unlock_src_dev;
+	}
+
+	tmp_rxq = __netif_get_rx_queue(dst_dev, dst_dev->real_num_rx_queues - 1);
+	if (tmp_rxq->peer && tmp_rxq->peer->dev != src_dev) {
+		err = -EOPNOTSUPP;
+		NL_SET_ERR_MSG(info->extack,
+			       "Binding multiple queues from different source devices not supported");
+		goto err_unlock_src_dev;
+	}
+
+	err = dst_dev->queue_mgmt_ops->ndo_queue_create(dst_dev, &dst_qid);
+	if (err) {
+		NL_SET_ERR_MSG(info->extack,
+			       "Destination device is unable to create a new queue");
+		goto err_unlock_src_dev;
+	}
+
+	dst_rxq = __netif_get_rx_queue(dst_dev, dst_qid);
+	netdev_rx_queue_peer(src_dev, src_rxq, dst_rxq);
+
+	nla_put_u32(rsp, NETDEV_A_QUEUE_PAIR_DST_QUEUE_ID, dst_qid);
+	genlmsg_end(rsp, hdr);
+
+	netdev_unlock(src_dev);
+	netdev_unlock(dst_dev);
+
+	return genlmsg_reply(rsp, info);
+
+err_unlock_dst_dev_src_dev_put:
+	netdev_put(src_dev, &dev_tracker);
+	goto err_unlock_dst_dev;
+err_unlock_src_dev:
+	netdev_unlock(src_dev);
+err_unlock_dst_dev:
+	netdev_unlock(dst_dev);
+err_genlmsg_free:
+	nlmsg_free(rsp);
+	return err;
 }
 
 void netdev_nl_sock_priv_init(struct netdev_nl_sock *priv)
diff --git a/net/core/netdev_rx_queue.c b/net/core/netdev_rx_queue.c
index c7d9341b7630..6eb12f3b969c 100644
--- a/net/core/netdev_rx_queue.c
+++ b/net/core/netdev_rx_queue.c
@@ -18,6 +18,69 @@ bool netif_rxq_has_unreadable_mp(struct net_device *dev, int idx)
 }
 EXPORT_SYMBOL(netif_rxq_has_unreadable_mp);
 
+void netdev_rx_queue_peer(struct net_device *src_dev,
+			  struct netdev_rx_queue *src_rxq,
+			  struct netdev_rx_queue *dst_rxq)
+{
+	netdev_assert_locked(src_dev);
+	netdev_assert_locked(dst_rxq->dev);
+
+	netdev_hold(src_dev, &src_rxq->peer_tracker, GFP_KERNEL);
+	__netdev_rx_queue_peer(src_rxq, dst_rxq);
+}
+
+void netdev_rx_queue_unpeer(struct net_device *src_dev,
+			    struct netdev_rx_queue *src_rxq,
+			    struct netdev_rx_queue *dst_rxq)
+{
+	WARN_ON_ONCE(READ_ONCE(dst_rxq->dev->reg_state) != NETREG_UNREGISTERING);
+
+	netdev_assert_locked(dst_rxq->dev);
+	netdev_assert_locked(src_dev);
+
+	__netdev_rx_queue_unpeer(src_rxq, dst_rxq);
+	netdev_put(src_dev, &src_rxq->peer_tracker);
+}
+
+static struct netdev_rx_queue *
+__netif_get_rx_queue_peer(struct net_device **dev, unsigned int *rxq_idx)
+{
+	struct net_device *orig_dev = *dev;
+	struct netdev_rx_queue *rxq = __netif_get_rx_queue(orig_dev, *rxq_idx);
+
+	if (rxq->peer) {
+		if (orig_dev->dev.parent)
+			return NULL;
+		rxq = rxq->peer;
+		*rxq_idx = get_netdev_rx_queue_index(rxq);
+		*dev = rxq->dev;
+	}
+	return rxq;
+}
+
+struct netdev_rx_queue *
+netif_get_rx_queue_peer_locked(struct net_device **dev, unsigned int *rxq_idx)
+{
+	struct net_device *orig_dev = *dev;
+	struct netdev_rx_queue *rxq;
+
+	/* Locking order is always from the virtual to the physical device
+	 * see netdev_nl_bind_queue_doit().
+	 */
+	netdev_ops_assert_locked(orig_dev);
+	rxq = __netif_get_rx_queue_peer(dev, rxq_idx);
+	if (rxq && orig_dev != *dev)
+		netdev_lock(*dev);
+	return rxq;
+}
+
+void netif_put_rx_queue_peer_locked(struct net_device *orig_dev,
+				    struct net_device *dev)
+{
+	if (orig_dev != dev)
+		netdev_unlock(dev);
+}
+
 int netdev_rx_queue_restart(struct net_device *dev, unsigned int rxq_idx)
 {
 	struct netdev_rx_queue *rxq = __netif_get_rx_queue(dev, rxq_idx);
-- 
2.43.0

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