[RFC,net-next,v8,04/14] netdev: support binding dma-buf to netdevice

Add a netdev_dmabuf_binding struct which represents the
dma-buf-to-netdevice binding. The netlink API will bind the dma-buf to
rx queues on the netdevice. On the binding, the dma_buf_attach
& dma_buf_map_attachment will occur. The entries in the sg_table from
mapping will be inserted into a genpool to make it ready
for allocation.

The chunks in the genpool are owned by a dmabuf_chunk_owner struct which
holds the dma-buf offset of the base of the chunk and the dma_addr of
the chunk. Both are needed to use allocations that come from this chunk.

We create a new type that represents an allocation from the genpool:
net_iov. We setup the net_iov allocation size in the
genpool to PAGE_SIZE for simplicity: to match the PAGE_SIZE normally
allocated by the page pool and given to the drivers.

The user can unbind the dmabuf from the netdevice by closing the netlink
socket that established the binding. We do this so that the binding is
automatically unbound even if the userspace process crashes.

The binding and unbinding leaves an indicator in struct netdev_rx_queue
that the given queue is bound, but the binding doesn't take effect until
the driver actually reconfigures its queues, and re-initializes its page
pool.

The netdev_dmabuf_binding struct is refcounted, and releases its
resources only when all the refs are released.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Kaiyuan Zhang <kaiyuanz@google.com>
Signed-off-by: Mina Almasry <almasrymina@google.com>

---

v8:
- move dmabuf_devmem_ops usage to later patch to avoid patch-by-patch
  build error.

v7:
- Use IS_ERR() instead of IS_ERR_OR_NULL() for the dma_buf_get() return
  value.
- Changes netdev_* naming in devmem.c to net_devmem_* (Yunsheng).
- DMA_BIDIRECTIONAL -> DMA_FROM_DEVICE (Yunsheng).
- Added a comment around recovering of the old rx queue in
  net_devmem_restart_rx_queue(), and added freeing of old_mem if the
  restart of the old queue fails. (Yunsheng).
- Use kernel-family sock-priv (Jakub).
- Put pp_memory_provider_params in netdev_rx_queue instead of the
  dma-buf specific binding (Pavel & David).
- Move queue management ops to queue_mgmt_ops instead of netdev_ops
  (Jakub).
- Remove excess whitespaces (Jakub).
- Use genlmsg_iput (Jakub).

v6:
- Validate rx queue index
- Refactor new functions into devmem.c (Pavel)

v5:
- Renamed page_pool_iov to net_iov, and moved that support to devmem.h
  or netmem.h.

v1:

- Introduce devmem.h instead of bloating netdevice.h (Jakub)
- ENOTSUPP -> EOPNOTSUPP (checkpatch.pl I think)
- Remove unneeded rcu protection for binding->list (rtnl protected)
- Removed extraneous err_binding_put: label.
- Removed dma_addr += len (Paolo).
- Don't override err on netdev_bind_dmabuf_to_queue failure.
- Rename devmem -> dmabuf (David).
- Add id to dmabuf binding (David/Stan).
- Fix missing xa_destroy bound_rq_list.
- Use queue api to reset bound RX queues (Jakub).
- Update netlink API for rx-queue type (tx/re) (Jakub).

RFC v3:
- Support multi rx-queue binding

---
 Documentation/netlink/specs/netdev.yaml |   4 +
 include/net/devmem.h                    | 111 +++++++++
 include/net/netdev_rx_queue.h           |   2 +
 include/net/netmem.h                    |  10 +
 include/net/page_pool/types.h           |   5 +
 net/core/Makefile                       |   2 +-
 net/core/dev.c                          |   3 +
 net/core/devmem.c                       | 303 ++++++++++++++++++++++++
 net/core/netdev-genl-gen.c              |   4 +
 net/core/netdev-genl-gen.h              |   4 +
 net/core/netdev-genl.c                  | 105 +++++++-
 11 files changed, 550 insertions(+), 3 deletions(-)
 create mode 100644 include/net/devmem.h
 create mode 100644 net/core/devmem.c

On 2024-04-02 5:20 pm, Mina Almasry wrote:
> Add a netdev_dmabuf_binding struct which represents the
> dma-buf-to-netdevice binding. The netlink API will bind the dma-buf to
> rx queues on the netdevice. On the binding, the dma_buf_attach
> & dma_buf_map_attachment will occur. The entries in the sg_table from
> mapping will be inserted into a genpool to make it ready
> for allocation.
> 
> The chunks in the genpool are owned by a dmabuf_chunk_owner struct which
> holds the dma-buf offset of the base of the chunk and the dma_addr of
> the chunk. Both are needed to use allocations that come from this chunk.
> 
> We create a new type that represents an allocation from the genpool:
> net_iov. We setup the net_iov allocation size in the
> genpool to PAGE_SIZE for simplicity: to match the PAGE_SIZE normally
> allocated by the page pool and given to the drivers.
> 
> The user can unbind the dmabuf from the netdevice by closing the netlink
> socket that established the binding. We do this so that the binding is
> automatically unbound even if the userspace process crashes.
> 
> The binding and unbinding leaves an indicator in struct netdev_rx_queue
> that the given queue is bound, but the binding doesn't take effect until
> the driver actually reconfigures its queues, and re-initializes its page
> pool.
> 
> The netdev_dmabuf_binding struct is refcounted, and releases its
> resources only when all the refs are released.
> 
> Signed-off-by: Willem de Bruijn <willemb@google.com>
> Signed-off-by: Kaiyuan Zhang <kaiyuanz@google.com>
> Signed-off-by: Mina Almasry <almasrymina@google.com>
> 
> ---
> 
> v8:
> - move dmabuf_devmem_ops usage to later patch to avoid patch-by-patch
>   build error.
> 
> v7:
> - Use IS_ERR() instead of IS_ERR_OR_NULL() for the dma_buf_get() return
>   value.
> - Changes netdev_* naming in devmem.c to net_devmem_* (Yunsheng).
> - DMA_BIDIRECTIONAL -> DMA_FROM_DEVICE (Yunsheng).
> - Added a comment around recovering of the old rx queue in
>   net_devmem_restart_rx_queue(), and added freeing of old_mem if the
>   restart of the old queue fails. (Yunsheng).
> - Use kernel-family sock-priv (Jakub).
> - Put pp_memory_provider_params in netdev_rx_queue instead of the
>   dma-buf specific binding (Pavel & David).
> - Move queue management ops to queue_mgmt_ops instead of netdev_ops
>   (Jakub).
> - Remove excess whitespaces (Jakub).
> - Use genlmsg_iput (Jakub).
> 
> v6:
> - Validate rx queue index
> - Refactor new functions into devmem.c (Pavel)
> 
> v5:
> - Renamed page_pool_iov to net_iov, and moved that support to devmem.h
>   or netmem.h.
> 
> v1:
> 
> - Introduce devmem.h instead of bloating netdevice.h (Jakub)
> - ENOTSUPP -> EOPNOTSUPP (checkpatch.pl I think)
> - Remove unneeded rcu protection for binding->list (rtnl protected)
> - Removed extraneous err_binding_put: label.
> - Removed dma_addr += len (Paolo).
> - Don't override err on netdev_bind_dmabuf_to_queue failure.
> - Rename devmem -> dmabuf (David).
> - Add id to dmabuf binding (David/Stan).
> - Fix missing xa_destroy bound_rq_list.
> - Use queue api to reset bound RX queues (Jakub).
> - Update netlink API for rx-queue type (tx/re) (Jakub).
> 
> RFC v3:
> - Support multi rx-queue binding
> 
> ---
>  Documentation/netlink/specs/netdev.yaml |   4 +
>  include/net/devmem.h                    | 111 +++++++++
>  include/net/netdev_rx_queue.h           |   2 +
>  include/net/netmem.h                    |  10 +
>  include/net/page_pool/types.h           |   5 +
>  net/core/Makefile                       |   2 +-
>  net/core/dev.c                          |   3 +
>  net/core/devmem.c                       | 303 ++++++++++++++++++++++++
>  net/core/netdev-genl-gen.c              |   4 +
>  net/core/netdev-genl-gen.h              |   4 +
>  net/core/netdev-genl.c                  | 105 +++++++-
>  11 files changed, 550 insertions(+), 3 deletions(-)
>  create mode 100644 include/net/devmem.h
>  create mode 100644 net/core/devmem.c
> 
> diff --git a/Documentation/netlink/specs/netdev.yaml b/Documentation/netlink/specs/netdev.yaml
> index 275d1faa87a6..bf4e58dfe9dd 100644
> --- a/Documentation/netlink/specs/netdev.yaml
> +++ b/Documentation/netlink/specs/netdev.yaml
> @@ -550,6 +550,10 @@ operations:
>              - tx-packets
>              - tx-bytes
>  
> +kernel-family:
> +  headers: [ "linux/list.h"]
> +  sock-priv: struct list_head
> +
>  mcast-groups:
>    list:
>      -
> diff --git a/include/net/devmem.h b/include/net/devmem.h
> new file mode 100644
> index 000000000000..fa03bdabdffd
> --- /dev/null
> +++ b/include/net/devmem.h
> @@ -0,0 +1,111 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * Device memory TCP support
> + *
> + * Authors:	Mina Almasry <almasrymina@google.com>
> + *		Willem de Bruijn <willemb@google.com>
> + *		Kaiyuan Zhang <kaiyuanz@google.com>
> + *
> + */
> +#ifndef _NET_DEVMEM_H
> +#define _NET_DEVMEM_H
> +
> +struct net_devmem_dmabuf_binding {
> +	struct dma_buf *dmabuf;
> +	struct dma_buf_attachment *attachment;
> +	struct sg_table *sgt;
> +	struct net_device *dev;
> +	struct gen_pool *chunk_pool;
> +
> +	/* The user holds a ref (via the netlink API) for as long as they want
> +	 * the binding to remain alive. Each page pool using this binding holds
> +	 * a ref to keep the binding alive. Each allocated net_iov holds a
> +	 * ref.
> +	 *
> +	 * The binding undos itself and unmaps the underlying dmabuf once all
> +	 * those refs are dropped and the binding is no longer desired or in
> +	 * use.
> +	 */
> +	refcount_t ref;
> +
> +	/* The list of bindings currently active. Used for netlink to notify us
> +	 * of the user dropping the bind.
> +	 */
> +	struct list_head list;
> +
> +	/* rxq's this binding is active on. */
> +	struct xarray bound_rxq_list;
> +
> +	/* ID of this binding. Globally unique to all bindings currently
> +	 * active.
> +	 */
> +	u32 id;
> +};
> +
> +/* Owner of the dma-buf chunks inserted into the gen pool. Each scatterlist
> + * entry from the dmabuf is inserted into the genpool as a chunk, and needs
> + * this owner struct to keep track of some metadata necessary to create
> + * allocations from this chunk.
> + */
> +struct dmabuf_genpool_chunk_owner {
> +	/* Offset into the dma-buf where this chunk starts.  */
> +	unsigned long base_virtual;
> +
> +	/* dma_addr of the start of the chunk.  */
> +	dma_addr_t base_dma_addr;
> +
> +	/* Array of net_iovs for this chunk. */
> +	struct net_iov *niovs;
> +	size_t num_niovs;
> +
> +	struct net_devmem_dmabuf_binding *binding;
> +};
> +
> +#ifdef CONFIG_DMA_SHARED_BUFFER
> +void __net_devmem_dmabuf_binding_free(struct net_devmem_dmabuf_binding *binding);
> +int net_devmem_bind_dmabuf(struct net_device *dev, unsigned int dmabuf_fd,
> +			   struct net_devmem_dmabuf_binding **out);
> +void net_devmem_unbind_dmabuf(struct net_devmem_dmabuf_binding *binding);
> +int net_devmem_bind_dmabuf_to_queue(struct net_device *dev, u32 rxq_idx,
> +				    struct net_devmem_dmabuf_binding *binding);
> +#else
> +static inline void
> +__net_devmem_dmabuf_binding_free(struct net_devmem_dmabuf_binding *binding)
> +{
> +}
> +
> +static inline int net_devmem_bind_dmabuf(struct net_device *dev,
> +					 unsigned int dmabuf_fd,
> +					 struct net_devmem_dmabuf_binding **out)
> +{
> +	return -EOPNOTSUPP;
> +}
> +static inline void
> +net_devmem_unbind_dmabuf(struct net_devmem_dmabuf_binding *binding)
> +{
> +}
> +
> +static inline int
> +net_devmem_bind_dmabuf_to_queue(struct net_device *dev, u32 rxq_idx,
> +				struct net_devmem_dmabuf_binding *binding)
> +{
> +	return -EOPNOTSUPP;
> +}
> +#endif
> +
> +static inline void
> +net_devmem_dmabuf_binding_get(struct net_devmem_dmabuf_binding *binding)
> +{
> +	refcount_inc(&binding->ref);
> +}
> +
> +static inline void
> +net_devmem_dmabuf_binding_put(struct net_devmem_dmabuf_binding *binding)
> +{
> +	if (!refcount_dec_and_test(&binding->ref))
> +		return;
> +
> +	__net_devmem_dmabuf_binding_free(binding);
> +}
> +
> +#endif /* _NET_DEVMEM_H */
> diff --git a/include/net/netdev_rx_queue.h b/include/net/netdev_rx_queue.h
> index aa1716fb0e53..f0d093f72a2c 100644
> --- a/include/net/netdev_rx_queue.h
> +++ b/include/net/netdev_rx_queue.h
> @@ -6,6 +6,7 @@
>  #include <linux/netdevice.h>
>  #include <linux/sysfs.h>
>  #include <net/xdp.h>
> +#include <net/page_pool/types.h>
>  
>  /* This structure contains an instance of an RX queue. */
>  struct netdev_rx_queue {
> @@ -25,6 +26,7 @@ struct netdev_rx_queue {
>  	 * Readers and writers must hold RTNL
>  	 */
>  	struct napi_struct		*napi;
> +	struct pp_memory_provider_params mp_params;
>  } ____cacheline_aligned_in_smp;
>  
>  /*
> diff --git a/include/net/netmem.h b/include/net/netmem.h
> index d8b810245c1d..72e932a1a948 100644
> --- a/include/net/netmem.h
> +++ b/include/net/netmem.h
> @@ -8,6 +8,16 @@
>  #ifndef _NET_NETMEM_H
>  #define _NET_NETMEM_H
>  
> +#include <net/devmem.h>
> +
> +/* net_iov */
> +
> +struct net_iov {
> +	struct dmabuf_genpool_chunk_owner *owner;
> +};
> +
> +/* netmem */
> +
>  /**
>   * typedef netmem_ref - a nonexistent type marking a reference to generic
>   * network memory.
> diff --git a/include/net/page_pool/types.h b/include/net/page_pool/types.h
> index ffe5f31fb0da..07e6afafedbe 100644
> --- a/include/net/page_pool/types.h
> +++ b/include/net/page_pool/types.h
> @@ -135,6 +135,11 @@ struct memory_provider_ops {
>  	bool (*release_page)(struct page_pool *pool, struct page *page);
>  };
>  
> +struct pp_memory_provider_params {
> +	const struct memory_provider_ops *mp_ops;
> +	void *mp_priv;
> +};
> +
>  struct page_pool {
>  	struct page_pool_params_fast p;
>  
> diff --git a/net/core/Makefile b/net/core/Makefile
> index 21d6fbc7e884..f5b7bfaba097 100644
> --- a/net/core/Makefile
> +++ b/net/core/Makefile
> @@ -13,7 +13,7 @@ obj-y		     += dev.o dev_addr_lists.o dst.o netevent.o \
>  			neighbour.o rtnetlink.o utils.o link_watch.o filter.o \
>  			sock_diag.o dev_ioctl.o tso.o sock_reuseport.o \
>  			fib_notifier.o xdp.o flow_offload.o gro.o \
> -			netdev-genl.o netdev-genl-gen.o gso.o
> +			netdev-genl.o netdev-genl-gen.o gso.o devmem.o
>  
>  obj-$(CONFIG_NETDEV_ADDR_LIST_TEST) += dev_addr_lists_test.o
>  
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 818699dea9d7..7ef8def6ec43 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -157,6 +157,9 @@
>  #include <net/page_pool/types.h>
>  #include <net/page_pool/helpers.h>
>  #include <net/rps.h>
> +#include <linux/genalloc.h>
> +#include <linux/dma-buf.h>
> +#include <net/devmem.h>
>  
>  #include "dev.h"
>  #include "net-sysfs.h"
> diff --git a/net/core/devmem.c b/net/core/devmem.c
> new file mode 100644
> index 000000000000..02a6abaecf40
> --- /dev/null
> +++ b/net/core/devmem.c
> @@ -0,0 +1,303 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + *      Devmem TCP
> + *
> + *      Authors:	Mina Almasry <almasrymina@google.com>
> + *			Willem de Bruijn <willemdebruijn.kernel@gmail.com>
> + *			Kaiyuan Zhang <kaiyuanz@google.com
> + */
> +
> +#include <linux/types.h>
> +#include <linux/mm.h>
> +#include <linux/netdevice.h>
> +#include <trace/events/page_pool.h>
> +#include <net/netdev_rx_queue.h>
> +#include <net/page_pool/types.h>
> +#include <net/page_pool/helpers.h>
> +#include <linux/genalloc.h>
> +#include <linux/dma-buf.h>
> +#include <net/devmem.h>
> +#include <net/netdev_queues.h>
> +
> +/* Device memory support */
> +
> +#ifdef CONFIG_DMA_SHARED_BUFFER
> +static void net_devmem_dmabuf_free_chunk_owner(struct gen_pool *genpool,
> +					       struct gen_pool_chunk *chunk,
> +					       void *not_used)
> +{
> +	struct dmabuf_genpool_chunk_owner *owner = chunk->owner;
> +
> +	kvfree(owner->niovs);
> +	kfree(owner);
> +}
> +
> +void __net_devmem_dmabuf_binding_free(struct net_devmem_dmabuf_binding *binding)
> +{
> +	size_t size, avail;
> +
> +	gen_pool_for_each_chunk(binding->chunk_pool,
> +				net_devmem_dmabuf_free_chunk_owner, NULL);
> +
> +	size = gen_pool_size(binding->chunk_pool);
> +	avail = gen_pool_avail(binding->chunk_pool);
> +
> +	if (!WARN(size != avail, "can't destroy genpool. size=%zu, avail=%zu",
> +		  size, avail))
> +		gen_pool_destroy(binding->chunk_pool);
> +
> +	dma_buf_unmap_attachment(binding->attachment, binding->sgt,
> +				 DMA_FROM_DEVICE);
> +	dma_buf_detach(binding->dmabuf, binding->attachment);
> +	dma_buf_put(binding->dmabuf);
> +	xa_destroy(&binding->bound_rxq_list);
> +	kfree(binding);
> +}
> +
> +static int net_devmem_restart_rx_queue(struct net_device *dev, int rxq_idx)
> +{
> +	void *new_mem;
> +	void *old_mem;
> +	int err;
> +
> +	if (!dev->queue_mgmt_ops->ndo_queue_stop ||
> +	    !dev->queue_mgmt_ops->ndo_queue_mem_free ||
> +	    !dev->queue_mgmt_ops->ndo_queue_mem_alloc ||
> +	    !dev->queue_mgmt_ops->ndo_queue_start)
> +		return -EOPNOTSUPP;
> +
> +	new_mem = dev->queue_mgmt_ops->ndo_queue_mem_alloc(dev, rxq_idx);
> +	if (!new_mem)
> +		return -ENOMEM;
> +
> +	err = dev->queue_mgmt_ops->ndo_queue_stop(dev, rxq_idx, &old_mem);
> +	if (err)
> +		goto err_free_new_mem;
> +
> +	err = dev->queue_mgmt_ops->ndo_queue_start(dev, rxq_idx, new_mem);
> +	if (err)
> +		goto err_start_queue;
> +
> +	dev->queue_mgmt_ops->ndo_queue_mem_free(dev, old_mem);
> +
> +	return 0;
> +
> +err_start_queue:
> +	/* Restarting the queue with old_mem should be successful as we haven't
> +	 * changed any of the queue configuration, and there is not much we can
> +	 * do to recover from a failure here.
> +	 *
> +	 * WARN if the we fail to recover the old rx queue, and at least free
> +	 * old_mem so we don't also leak that.
> +	 */
> +	if (dev->queue_mgmt_ops->ndo_queue_start(dev, rxq_idx, old_mem)) {
> +		WARN(1,
> +		     "Failed to restart old queue in error path. RX queue %d may be unhealthy.",
> +		     rxq_idx);
> +		dev->queue_mgmt_ops->ndo_queue_mem_free(dev, &old_mem);
> +	}
> +
> +err_free_new_mem:
> +	dev->queue_mgmt_ops->ndo_queue_mem_free(dev, new_mem);
> +
> +	return err;
> +}
> +
> +/* Protected by rtnl_lock() */
> +static DEFINE_XARRAY_FLAGS(net_devmem_dmabuf_bindings, XA_FLAGS_ALLOC1);
> +
> +void net_devmem_unbind_dmabuf(struct net_devmem_dmabuf_binding *binding)
> +{
> +	struct netdev_rx_queue *rxq;
> +	unsigned long xa_idx;
> +	unsigned int rxq_idx;
> +
> +	if (!binding)
> +		return;
> +
> +	if (binding->list.next)
> +		list_del(&binding->list);
> +
> +	xa_for_each(&binding->bound_rxq_list, xa_idx, rxq) {
> +		if (rxq->mp_params.mp_priv == binding) {
> +			/* We hold the rtnl_lock while binding/unbinding
> +			 * dma-buf, so we can't race with another thread that
> +			 * is also modifying this value. However, the page_pool
> +			 * may read this config while it's creating its
> +			 * rx-queues. WRITE_ONCE() here to match the
> +			 * READ_ONCE() in the page_pool.
> +			 */
> +			WRITE_ONCE(rxq->mp_params.mp_ops, NULL);
> +			WRITE_ONCE(rxq->mp_params.mp_priv, NULL);
> +
> +			rxq_idx = get_netdev_rx_queue_index(rxq);
> +
> +			net_devmem_restart_rx_queue(binding->dev, rxq_idx);
> +		}
> +	}
> +
> +	xa_erase(&net_devmem_dmabuf_bindings, binding->id);
> +
> +	net_devmem_dmabuf_binding_put(binding);
> +}
> +
> +int net_devmem_bind_dmabuf_to_queue(struct net_device *dev, u32 rxq_idx,
> +				    struct net_devmem_dmabuf_binding *binding)
> +{
> +	struct netdev_rx_queue *rxq;
> +	u32 xa_idx;
> +	int err;
> +
> +	if (rxq_idx >= dev->num_rx_queues)
> +		return -ERANGE;
> +
> +	rxq = __netif_get_rx_queue(dev, rxq_idx);
> +	if (rxq->mp_params.mp_priv)
> +		return -EEXIST;
> +
> +	err = xa_alloc(&binding->bound_rxq_list, &xa_idx, rxq, xa_limit_32b,
> +		       GFP_KERNEL);
> +	if (err)
> +		return err;
> +
> +	/* We hold the rtnl_lock while binding/unbinding dma-buf, so we can't
> +	 * race with another thread that is also modifying this value. However,
> +	 * the driver may read this config while it's creating its * rx-queues.
> +	 * WRITE_ONCE() here to match the READ_ONCE() in the driver.
> +	 */
> +	WRITE_ONCE(rxq->mp_params.mp_priv, binding);

Is the mp_ops update missing here?

> +
> +	err = net_devmem_restart_rx_queue(dev, rxq_idx);
> +	if (err)
> +		goto err_xa_erase;
> +
> +	return 0;
> +
> +err_xa_erase:
> +	WRITE_ONCE(rxq->mp_params.mp_ops, NULL);
> +	WRITE_ONCE(rxq->mp_params.mp_priv, NULL);
> +	xa_erase(&binding->bound_rxq_list, xa_idx);
> +
> +	return err;
> +}
> +
> +int net_devmem_bind_dmabuf(struct net_device *dev, unsigned int dmabuf_fd,
> +			   struct net_devmem_dmabuf_binding **out)
> +{
> +	struct net_devmem_dmabuf_binding *binding;
> +	static u32 id_alloc_next;
> +	struct scatterlist *sg;
> +	struct dma_buf *dmabuf;
> +	unsigned int sg_idx, i;
> +	unsigned long virtual;
> +	int err;
> +
> +	dmabuf = dma_buf_get(dmabuf_fd);
> +	if (IS_ERR(dmabuf))
> +		return -EBADFD;
> +
> +	binding = kzalloc_node(sizeof(*binding), GFP_KERNEL,
> +			       dev_to_node(&dev->dev));
> +	if (!binding) {
> +		err = -ENOMEM;
> +		goto err_put_dmabuf;
> +	}
> +
> +	binding->dev = dev;
> +
> +	err = xa_alloc_cyclic(&net_devmem_dmabuf_bindings, &binding->id,
> +			      binding, xa_limit_32b, &id_alloc_next,
> +			      GFP_KERNEL);
> +	if (err < 0)
> +		goto err_free_binding;
> +
> +	xa_init_flags(&binding->bound_rxq_list, XA_FLAGS_ALLOC);
> +
> +	refcount_set(&binding->ref, 1);
> +
> +	binding->dmabuf = dmabuf;
> +
> +	binding->attachment = dma_buf_attach(binding->dmabuf, dev->dev.parent);
> +	if (IS_ERR(binding->attachment)) {
> +		err = PTR_ERR(binding->attachment);
> +		goto err_free_id;
> +	}
> +
> +	binding->sgt =
> +		dma_buf_map_attachment(binding->attachment, DMA_BIDIRECTIONAL);
> +	if (IS_ERR(binding->sgt)) {
> +		err = PTR_ERR(binding->sgt);
> +		goto err_detach;
> +	}
> +
> +	/* For simplicity we expect to make PAGE_SIZE allocations, but the
> +	 * binding can be much more flexible than that. We may be able to
> +	 * allocate MTU sized chunks here. Leave that for future work...
> +	 */
> +	binding->chunk_pool =
> +		gen_pool_create(PAGE_SHIFT, dev_to_node(&dev->dev));
> +	if (!binding->chunk_pool) {
> +		err = -ENOMEM;
> +		goto err_unmap;
> +	}
> +
> +	virtual = 0;
> +	for_each_sgtable_dma_sg(binding->sgt, sg, sg_idx) {
> +		dma_addr_t dma_addr = sg_dma_address(sg);
> +		struct dmabuf_genpool_chunk_owner *owner;
> +		size_t len = sg_dma_len(sg);
> +		struct net_iov *niov;
> +
> +		owner = kzalloc_node(sizeof(*owner), GFP_KERNEL,
> +				     dev_to_node(&dev->dev));
> +		owner->base_virtual = virtual;
> +		owner->base_dma_addr = dma_addr;
> +		owner->num_niovs = len / PAGE_SIZE;
> +		owner->binding = binding;
> +
> +		err = gen_pool_add_owner(binding->chunk_pool, dma_addr,
> +					 dma_addr, len, dev_to_node(&dev->dev),
> +					 owner);
> +		if (err) {
> +			err = -EINVAL;
> +			goto err_free_chunks;
> +		}
> +
> +		owner->niovs = kvmalloc_array(owner->num_niovs,
> +					      sizeof(*owner->niovs),
> +					      GFP_KERNEL);
> +		if (!owner->niovs) {
> +			err = -ENOMEM;
> +			goto err_free_chunks;
> +		}
> +
> +		for (i = 0; i < owner->num_niovs; i++) {
> +			niov = &owner->niovs[i];
> +			niov->owner = owner;
> +		}
> +
> +		virtual += len;
> +	}
> +
> +	*out = binding;
> +
> +	return 0;
> +
> +err_free_chunks:
> +	gen_pool_for_each_chunk(binding->chunk_pool,
> +				net_devmem_dmabuf_free_chunk_owner, NULL);
> +	gen_pool_destroy(binding->chunk_pool);
> +err_unmap:
> +	dma_buf_unmap_attachment(binding->attachment, binding->sgt,
> +				 DMA_BIDIRECTIONAL);
> +err_detach:
> +	dma_buf_detach(dmabuf, binding->attachment);
> +err_free_id:
> +	xa_erase(&net_devmem_dmabuf_bindings, binding->id);
> +err_free_binding:
> +	kfree(binding);
> +err_put_dmabuf:
> +	dma_buf_put(dmabuf);
> +	return err;
> +}
> +#endif
> diff --git a/net/core/netdev-genl-gen.c b/net/core/netdev-genl-gen.c
> index bbaaa1b36b5b..da65595750fd 100644
> --- a/net/core/netdev-genl-gen.c
> +++ b/net/core/netdev-genl-gen.c
> @@ -9,6 +9,7 @@
>  #include "netdev-genl-gen.h"
>  
>  #include <uapi/linux/netdev.h>
> +#include <linux/list.h>
>  
>  /* Integer value ranges */
>  static const struct netlink_range_validation netdev_a_page_pool_id_range = {
> @@ -186,4 +187,7 @@ struct genl_family netdev_nl_family __ro_after_init = {
>  	.n_split_ops	= ARRAY_SIZE(netdev_nl_ops),
>  	.mcgrps		= netdev_nl_mcgrps,
>  	.n_mcgrps	= ARRAY_SIZE(netdev_nl_mcgrps),
> +	.sock_priv_size	= sizeof(struct list_head),
> +	.sock_priv_init	= (void *)netdev_nl_sock_priv_init,
> +	.sock_priv_destroy = (void *)netdev_nl_sock_priv_destroy,
>  };
> diff --git a/net/core/netdev-genl-gen.h b/net/core/netdev-genl-gen.h
> index ca5a0983f283..2c431b7dcbc8 100644
> --- a/net/core/netdev-genl-gen.h
> +++ b/net/core/netdev-genl-gen.h
> @@ -10,6 +10,7 @@
>  #include <net/genetlink.h>
>  
>  #include <uapi/linux/netdev.h>
> +#include <linux/list.h>
>  
>  /* Common nested types */
>  extern const struct nla_policy netdev_page_pool_info_nl_policy[NETDEV_A_PAGE_POOL_IFINDEX + 1];
> @@ -40,4 +41,7 @@ enum {
>  
>  extern struct genl_family netdev_nl_family;
>  
> +void netdev_nl_sock_priv_init(struct list_head *priv);
> +void netdev_nl_sock_priv_destroy(struct list_head *priv);
> +
>  #endif /* _LINUX_NETDEV_GEN_H */
> diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
> index 67711d29d0d4..38b2fe090adc 100644
> --- a/net/core/netdev-genl.c
> +++ b/net/core/netdev-genl.c
> @@ -10,6 +10,7 @@
>  #include <net/netdev_rx_queue.h>
>  #include <net/netdev_queues.h>
>  #include <net/busy_poll.h>
> +#include <net/devmem.h>
>  
>  #include "netdev-genl-gen.h"
>  #include "dev.h"
> @@ -674,10 +675,96 @@ int netdev_nl_qstats_get_dumpit(struct sk_buff *skb,
>  	return err;
>  }
>  
> -/* Stub */
>  int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct genl_info *info)
>  {
> -	return 0;
> +	struct nlattr *tb[ARRAY_SIZE(netdev_queue_dmabuf_nl_policy)];
> +	struct net_devmem_dmabuf_binding *out_binding;
> +	struct list_head *sock_binding_list;
> +	u32 ifindex, dmabuf_fd, rxq_idx;
> +	struct net_device *netdev;
> +	struct sk_buff *rsp;
> +	struct nlattr *attr;
> +	int rem, err = 0;
> +	void *hdr;
> +
> +	if (GENL_REQ_ATTR_CHECK(info, NETDEV_A_DEV_IFINDEX) ||
> +	    GENL_REQ_ATTR_CHECK(info, NETDEV_A_BIND_DMABUF_DMABUF_FD) ||
> +	    GENL_REQ_ATTR_CHECK(info, NETDEV_A_BIND_DMABUF_QUEUES))
> +		return -EINVAL;
> +
> +	ifindex = nla_get_u32(info->attrs[NETDEV_A_DEV_IFINDEX]);
> +	dmabuf_fd = nla_get_u32(info->attrs[NETDEV_A_BIND_DMABUF_DMABUF_FD]);
> +
> +	rtnl_lock();
> +
> +	netdev = __dev_get_by_index(genl_info_net(info), ifindex);
> +	if (!netdev) {
> +		err = -ENODEV;
> +		goto err_unlock;
> +	}
> +
> +	err = net_devmem_bind_dmabuf(netdev, dmabuf_fd, &out_binding);
> +	if (err)
> +		goto err_unlock;
> +
> +	nla_for_each_attr(attr, genlmsg_data(info->genlhdr),
> +			  genlmsg_len(info->genlhdr), rem) {
> +		if (nla_type(attr) != NETDEV_A_BIND_DMABUF_QUEUES)
> +			continue;
> +
> +		err = nla_parse_nested(
> +			tb, ARRAY_SIZE(netdev_queue_dmabuf_nl_policy) - 1, attr,
> +			netdev_queue_dmabuf_nl_policy, info->extack);
> +		if (err < 0)
> +			goto err_unbind;
> +
> +		rxq_idx = nla_get_u32(tb[NETDEV_A_QUEUE_DMABUF_IDX]);
> +		if (rxq_idx >= netdev->num_rx_queues) {
> +			err = -ERANGE;
> +			goto err_unbind;
> +		}
> +
> +		err = net_devmem_bind_dmabuf_to_queue(netdev, rxq_idx,
> +						      out_binding);
> +		if (err)
> +			goto err_unbind;
> +	}
> +
> +	sock_binding_list = genl_sk_priv_get(&netdev_nl_family,
> +					     NETLINK_CB(skb).sk);
> +	if (IS_ERR(sock_binding_list)) {
> +		err = PTR_ERR(sock_binding_list);
> +		goto err_unbind;
> +	}
> +
> +	list_add(&out_binding->list, sock_binding_list);
> +
> +	rsp = genlmsg_new(GENLMSG_DEFAULT_SIZE, GFP_KERNEL);
> +	if (!rsp) {
> +		err = -ENOMEM;
> +		goto err_unbind;
> +	}
> +
> +	hdr = genlmsg_iput(rsp, info);
> +	if (!hdr) {
> +		err = -EMSGSIZE;
> +		goto err_genlmsg_free;
> +	}
> +
> +	nla_put_u32(rsp, NETDEV_A_BIND_DMABUF_DMABUF_ID, out_binding->id);
> +	genlmsg_end(rsp, hdr);
> +
> +	rtnl_unlock();
> +
> +	return genlmsg_reply(rsp, info);
> +
> +err_genlmsg_free:
> +	nlmsg_free(rsp);
> +err_unbind:
> +	net_devmem_unbind_dmabuf(out_binding);
> +err_unlock:
> +	rtnl_unlock();
> +	return err;
>  }
>  
>  static int netdev_genl_netdevice_event(struct notifier_block *nb,
> @@ -724,3 +811,17 @@ static int __init netdev_genl_init(void)
>  }
>  
>  subsys_initcall(netdev_genl_init);
> +
> +void netdev_nl_sock_priv_init(struct list_head *priv)
> +{
> +	INIT_LIST_HEAD(priv);
> +}
> +
> +void netdev_nl_sock_priv_destroy(struct list_head *priv)
> +{
> +	struct net_devmem_dmabuf_binding *binding;
> +	struct net_devmem_dmabuf_binding *temp;
> +
> +	list_for_each_entry_safe(binding, temp, priv, list)
> +		net_devmem_unbind_dmabuf(binding);
> +}

On Wed, Apr 24, 2024 at 10:36 AM David Wei <dw@davidwei.uk> wrote:
>
> On 2024-04-02 5:20 pm, Mina Almasry wrote:
> > +     /* We hold the rtnl_lock while binding/unbinding dma-buf, so we can't
> > +      * race with another thread that is also modifying this value. However,
> > +      * the driver may read this config while it's creating its * rx-queues.
> > +      * WRITE_ONCE() here to match the READ_ONCE() in the driver.
> > +      */
> > +     WRITE_ONCE(rxq->mp_params.mp_priv, binding);
>
> Is the mp_ops update missing here?
>

I  do it in this patch, because it's the one that introduces mp_ops:
https://patchwork.kernel.org/project/netdevbpf/patch/20240403002053.2376017-9-almasrymina@google.com/