Commit 13d8e05a authored by Dragos Tatulea's avatar Dragos Tatulea Committed by Jakub Kicinski
Browse files

queue_api: add support for fetching per queue DMA dev 



For zerocopy (io_uring, devmem), there is an assumption that the
parent device can do DMA. However that is not always the case:
- Scalable Function netdevs [1] have the DMA device in the grandparent.
- For Multi-PF netdevs [2] queues can be associated to different DMA
devices.

This patch introduces the a queue based interface for allowing drivers
to expose a different DMA device for zerocopy.

[1] Documentation/networking/device_drivers/ethernet/mellanox/mlx5/switchdev.rst
[2] Documentation/networking/multi-pf-netdev.rst

Signed-off-by: default avatarDragos Tatulea <dtatulea@nvidia.com>
Reviewed-by: default avatarPavel Begunkov <asml.silence@gmail.com>
Reviewed-by: default avatarMina Almasry <almasrymina@google.com>
Link: https://patch.msgid.link/20250827144017.1529208-3-dtatulea@nvidia.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 14cd01c2

include/net/netdev_queues.h

+7 −0
Original line number Diff line number Diff line
@@ -127,6 +127,9 @@ void netdev_stat_queue_sum(struct net_device *netdev, 
 * @ndo_queue_stop:	Stop the RX queue at the specified index. The stopped

 *			queue's memory is written at the specified address.

 *

 * @ndo_queue_get_dma_dev: Get dma device for zero-copy operations to be used

 *			   for this queue. Return NULL on error.

 *

 * 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.
@@ -144,6 +147,8 @@ struct netdev_queue_mgmt_ops { 
	int			(*ndo_queue_stop)(struct net_device *dev,

						  void *per_queue_mem,

						  int idx);

	struct device *		(*ndo_queue_get_dma_dev)(struct net_device *dev,

							 int idx);

};



/**
@@ -321,4 +326,6 @@ static inline void netif_subqueue_sent(const struct net_device *dev, 
					 get_desc, start_thrs);		\

	})



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



#endif

net/core/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ obj-$(CONFIG_NETDEV_ADDR_LIST_TEST) += dev_addr_lists_test.o 
obj-y += net-sysfs.o

obj-y += hotdata.o

obj-y += netdev_rx_queue.o

obj-y += netdev_queues.o

obj-$(CONFIG_PAGE_POOL) += page_pool.o page_pool_user.o

obj-$(CONFIG_PROC_FS) += net-procfs.o

obj-$(CONFIG_NET_PKTGEN) += pktgen.o

net/core/netdev_queues.c

0 → 100644
+27 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0-or-later



#include <net/netdev_queues.h>



/**

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

 * @dev:	net_device

 * @idx:	queue index

 *

 * 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.

 *

 * 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;

	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;

}