net: move mp dev config validation to __net_mp_open_rxq()

devmem code performs a number of safety checks to avoid having
to reimplement all of them in the drivers. Move those to
__net_mp_open_rxq() and reuse that function for binding to make
sure that io_uring ZC also benefits from them.

While at it rename the queue ID variable to rxq_idx in
__net_mp_open_rxq(), we touch most of the relevant lines.

The XArray insertion is reordered after the netdev_rx_queue_restart()
call, otherwise we'd need to duplicate the queue index check
or risk inserting an invalid pointer. The XArray allocation
failures should be extremely rare.

Reviewed-by: Mina Almasry <almasrymina@google.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Fixes: 6e18ed929d3b ("net: add helpers for setting a memory provider on an rx queue")
Link: https://patch.msgid.link/20250403013405.2827250-2-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 38 insertions, 11 deletions

diff --git a/net/core/netdev_rx_queue.c b/net/core/netdev_rx_queue.c
index 3af716f77a13..556b5393ec9f 100644
--- a/net/core/netdev_rx_queue.c
+++ b/net/core/netdev_rx_queue.c
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
+#include <linux/ethtool_netlink.h>
 #include <linux/netdevice.h>
 #include <net/netdev_lock.h>
 #include <net/netdev_queues.h>
@@ -86,8 +87,9 @@ err_free_new_mem:
 }
 EXPORT_SYMBOL_NS_GPL(netdev_rx_queue_restart, "NETDEV_INTERNAL");
 
-static int __net_mp_open_rxq(struct net_device *dev, unsigned ifq_idx,
-			     struct pp_memory_provider_params *p)
+int __net_mp_open_rxq(struct net_device *dev, unsigned int rxq_idx,
+		      const struct pp_memory_provider_params *p,
+		      struct netlink_ext_ack *extack)
 {
 	struct netdev_rx_queue *rxq;
 	int ret;
@@ -95,16 +97,41 @@ static int __net_mp_open_rxq(struct net_device *dev, unsigned ifq_idx,
 	if (!netdev_need_ops_lock(dev))
 		return -EOPNOTSUPP;
 
-	if (ifq_idx >= dev->real_num_rx_queues)
+	if (rxq_idx >= dev->real_num_rx_queues)
 		return -EINVAL;
-	ifq_idx = array_index_nospec(ifq_idx, dev->real_num_rx_queues);
+	rxq_idx = array_index_nospec(rxq_idx, dev->real_num_rx_queues);
 
-	rxq = __netif_get_rx_queue(dev, ifq_idx);
-	if (rxq->mp_params.mp_ops)
+	if (rxq_idx >= dev->real_num_rx_queues) {
+		NL_SET_ERR_MSG(extack, "rx queue index out of range");
+		return -ERANGE;
+	}
+	if (dev->cfg->hds_config != ETHTOOL_TCP_DATA_SPLIT_ENABLED) {
+		NL_SET_ERR_MSG(extack, "tcp-data-split is disabled");
+		return -EINVAL;
+	}
+	if (dev->cfg->hds_thresh) {
+		NL_SET_ERR_MSG(extack, "hds-thresh is not zero");
+		return -EINVAL;
+	}
+	if (dev_xdp_prog_count(dev)) {
+		NL_SET_ERR_MSG(extack, "unable to custom memory provider to device with XDP program attached");
 		return -EEXIST;
+	}
+
+	rxq = __netif_get_rx_queue(dev, rxq_idx);
+	if (rxq->mp_params.mp_ops) {
+		NL_SET_ERR_MSG(extack, "designated queue already memory provider bound");
+		return -EEXIST;
+	}
+#ifdef CONFIG_XDP_SOCKETS
+	if (rxq->pool) {
+		NL_SET_ERR_MSG(extack, "designated queue already in use by AF_XDP");
+		return -EBUSY;
+	}
+#endif
 
 	rxq->mp_params = *p;
-	ret = netdev_rx_queue_restart(dev, ifq_idx);
+	ret = netdev_rx_queue_restart(dev, rxq_idx);
 	if (ret) {
 		rxq->mp_params.mp_ops = NULL;
 		rxq->mp_params.mp_priv = NULL;
@@ -112,19 +139,19 @@ static int __net_mp_open_rxq(struct net_device *dev, unsigned ifq_idx,
 	return ret;
 }
 
-int net_mp_open_rxq(struct net_device *dev, unsigned ifq_idx,
+int net_mp_open_rxq(struct net_device *dev, unsigned int rxq_idx,
 		    struct pp_memory_provider_params *p)
 {
 	int ret;
 
 	netdev_lock(dev);
-	ret = __net_mp_open_rxq(dev, ifq_idx, p);
+	ret = __net_mp_open_rxq(dev, rxq_idx, p, NULL);
 	netdev_unlock(dev);
 	return ret;
 }
 
-static void __net_mp_close_rxq(struct net_device *dev, unsigned ifq_idx,
-			      struct pp_memory_provider_params *old_p)
+void __net_mp_close_rxq(struct net_device *dev, unsigned int ifq_idx,
+			const struct pp_memory_provider_params *old_p)
 {
 	struct netdev_rx_queue *rxq;