[PATCH net-next v5 06/16] net: Proxy netdev_queue_get_dma_dev for leased queues

[Daniel Borkmann <daniel@iogearbox.net>]

From: David Wei <dw@davidwei.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@davidwei.uk>
Co-developed-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.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