Commit 222b5566 authored by David Wei's avatar David Wei Committed by Jakub Kicinski
Browse files

net: Proxy netdev_queue_get_dma_dev for leased queues 



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: default avatarDavid Wei <dw@davidwei.uk>
Co-developed-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Reviewed-by: default avatarNikolay Aleksandrov <razor@blackwall.org>
Link: https://patch.msgid.link/20260402231031.447597-8-daniel@iogearbox.net


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 5602ad61

include/net/netdev_queues.h

+3 −1
Original line number Diff line number Diff line
@@ -380,7 +380,9 @@ static inline unsigned int netif_xmit_timeout_ms(struct netdev_queue *txq) 
					 get_desc, start_thrs);		\

	})



struct device *netdev_queue_get_dma_dev(struct net_device *dev, int idx);

struct device *netdev_queue_get_dma_dev(struct net_device *dev,

					unsigned int idx,

					enum netdev_queue_type type);

bool netdev_can_create_queue(const struct net_device *dev,

			     struct netlink_ext_ack *extack);

bool netdev_can_lease_queue(const struct net_device *dev,

io_uring/zcrx.c

+2 −1
Original line number Diff line number Diff line
@@ -829,7 +829,8 @@ int io_register_zcrx_ifq(struct io_ring_ctx *ctx, 
	}

	netdev_hold(ifq->netdev, &ifq->netdev_tracker, GFP_KERNEL);



	ifq->dev = netdev_queue_get_dma_dev(ifq->netdev, reg.if_rxq);

	ifq->dev = netdev_queue_get_dma_dev(ifq->netdev, reg.if_rxq,

					    NETDEV_QUEUE_TYPE_RX);

	if (!ifq->dev) {

		ret = -EOPNOTSUPP;

		goto netdev_put_unlock;

net/core/netdev-genl.c

+3 −2
Original line number Diff line number Diff line
@@ -976,7 +976,8 @@ netdev_nl_get_dma_dev(struct net_device *netdev, unsigned long *rxq_bitmap, 
	for_each_set_bit(rxq_idx, rxq_bitmap, netdev->real_num_rx_queues) {

		struct device *rxq_dma_dev;



		rxq_dma_dev = netdev_queue_get_dma_dev(netdev, rxq_idx);

		rxq_dma_dev = netdev_queue_get_dma_dev(netdev, rxq_idx,

						       NETDEV_QUEUE_TYPE_RX);

		if (dma_dev && rxq_dma_dev != dma_dev) {

			NL_SET_ERR_MSG_FMT(extack, "DMA device mismatch between queue %u and %u (multi-PF device?)",

					   rxq_idx, prev_rxq_idx);
@@ -1153,7 +1154,7 @@ int netdev_nl_bind_tx_doit(struct sk_buff *skb, struct genl_info *info) 
		goto err_unlock_netdev;

	}



	dma_dev = netdev_queue_get_dma_dev(netdev, 0);

	dma_dev = netdev_queue_get_dma_dev(netdev, 0, NETDEV_QUEUE_TYPE_TX);

	binding = net_devmem_bind_dmabuf(netdev, dma_dev, DMA_TO_DEVICE,

					 dmabuf_fd, priv, info->extack);

	if (IS_ERR(binding)) {

net/core/netdev_queues.c

+32 −9
Original line number Diff line number Diff line
@@ -6,27 +6,50 @@ 


#include "dev.h"



static struct device *

__netdev_queue_get_dma_dev(struct net_device *dev, unsigned int idx)

{

	const struct netdev_queue_mgmt_ops *queue_ops = dev->queue_mgmt_ops;

	struct device *dma_dev;



	if (queue_ops && queue_ops->ndo_queue_get_dma_dev)

		dma_dev = queue_ops->ndo_queue_get_dma_dev(dev, idx);

	else

		dma_dev = dev->dev.parent;



	return dma_dev && dma_dev->dma_mask ? dma_dev : NULL;

}



/**

 * netdev_queue_get_dma_dev() - get dma device for zero-copy operations

 * @dev:	net_device

 * @idx:	queue index

 * @type:	queue type (RX or TX)

 *

 * Get dma device for zero-copy operations to be used for this queue.

 * When such device is not available or valid, the function will return NULL.

 * Get dma device for zero-copy operations to be used for this queue. If

 * the queue is an RX queue leased from a physical queue, we retrieve the

 * physical queue's dma device. When the dma 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)

struct device *netdev_queue_get_dma_dev(struct net_device *dev,

					unsigned int idx,

					enum netdev_queue_type type)

{

	const struct netdev_queue_mgmt_ops *queue_ops = dev->queue_mgmt_ops;

	struct net_device *orig_dev = dev;

	struct device *dma_dev;



	if (queue_ops && queue_ops->ndo_queue_get_dma_dev)

		dma_dev = queue_ops->ndo_queue_get_dma_dev(dev, idx);

	else

		dma_dev = dev->dev.parent;

	/* Only RX side supports queue leasing today. */

	if (type != NETDEV_QUEUE_TYPE_RX || !netif_rxq_is_leased(dev, idx))

		return __netdev_queue_get_dma_dev(dev, idx);



	return dma_dev && dma_dev->dma_mask ? dma_dev : NULL;

	if (!netif_get_rx_queue_lease_locked(&dev, &idx))

		return NULL;



	dma_dev = __netdev_queue_get_dma_dev(dev, idx);

	netif_put_rx_queue_lease_locked(orig_dev, dev);

	return dma_dev;

}



bool netdev_can_create_queue(const struct net_device *dev,