netdev - [PATCH net-next v5 06/16] net: Proxy netdev_queue_get_dma

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Message-ID: <20260109212632.146920-7-daniel@iogearbox.net>
Date: Fri,  9 Jan 2026 22:26:22 +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 v5 06/16] net: Proxy netdev_queue_get_dma_dev for leased queues

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

Extend netdev_queue_get_dma_dev to return the physical device of the
real rxq for DMA in case the queue was leased. This allows memory
providers like io_uring zero-copy or devmem to bind to the physically
leased rxq via virtual devices such as netkit.

Signed-off-by: David Wei <dw@...idwei.uk>
Co-developed-by: Daniel Borkmann <daniel@...earbox.net>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
---
 net/core/netdev_queues.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/net/core/netdev_queues.c b/net/core/netdev_queues.c
index fae92ee090c4..97acf6440829 100644
--- a/net/core/netdev_queues.c
+++ b/net/core/netdev_queues.c
@@ -9,16 +9,29 @@
  * @dev:	net_device
  * @idx:	queue index
  *
- * Get dma device for zero-copy operations to be used for this queue.
+ * Get dma device for zero-copy operations to be used for this queue. If the
+ * queue is leased to a physical queue, we retrieve the latter's dma device.
  * When such device is not available or valid, the function will return NULL.
  *
  * Return: Device or NULL on error
  */
 struct device *netdev_queue_get_dma_dev(struct net_device *dev, int idx)
 {
-	const struct netdev_queue_mgmt_ops *queue_ops = dev->queue_mgmt_ops;
+	const struct netdev_queue_mgmt_ops *queue_ops;
 	struct device *dma_dev;
 
+	if (idx < dev->real_num_rx_queues) {
+		struct netdev_rx_queue *rxq = __netif_get_rx_queue(dev, idx);
+
+		if (rxq->lease) {
+			rxq = rxq->lease;
+			dev = rxq->dev;
+			idx = get_netdev_rx_queue_index(rxq);
+		}
+	}
+
+	queue_ops = dev->queue_mgmt_ops;
+
 	if (queue_ops && queue_ops->ndo_queue_get_dma_dev)
 		dma_dev = queue_ops->ndo_queue_get_dma_dev(dev, idx);
 	else
-- 
2.43.0