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, and the binding is actuated by resetting
the rx queue using the queue API.

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>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com> # excluding netlink
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Link: https://patch.msgid.link/20240910171458.219195-4-almasrymina@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 26 insertions, 0 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 8f4dead64284..7818d7f6295e 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -161,6 +161,7 @@
 #include <linux/phy_link_topology.h>
 
 #include "dev.h"
+#include "devmem.h"
 #include "net-sysfs.h"
 
 static DEFINE_SPINLOCK(ptype_lock);
@@ -9367,6 +9368,11 @@ int dev_xdp_propagate(struct net_device *dev, struct netdev_bpf *bpf)
 	if (!dev->netdev_ops->ndo_bpf)
 		return -EOPNOTSUPP;
 
+	if (dev_get_min_mp_channel_count(dev)) {
+		NL_SET_ERR_MSG(bpf->extack, "unable to propagate XDP to device using memory provider");
+		return -EBUSY;
+	}
+
 	return dev->netdev_ops->ndo_bpf(dev, bpf);
 }
 EXPORT_SYMBOL_GPL(dev_xdp_propagate);
@@ -9399,6 +9405,11 @@ static int dev_xdp_install(struct net_device *dev, enum bpf_xdp_mode mode,
 	struct netdev_bpf xdp;
 	int err;
 
+	if (dev_get_min_mp_channel_count(dev)) {
+		NL_SET_ERR_MSG(extack, "unable to install XDP to device using memory provider");
+		return -EBUSY;
+	}
+
 	memset(&xdp, 0, sizeof(xdp));
 	xdp.command = mode == XDP_MODE_HW ? XDP_SETUP_PROG_HW : XDP_SETUP_PROG;
 	xdp.extack = extack;
@@ -9823,6 +9834,20 @@ err_out:
 	return err;
 }
 
+u32 dev_get_min_mp_channel_count(const struct net_device *dev)
+{
+	int i;
+
+	ASSERT_RTNL();
+
+	for (i = dev->real_num_rx_queues - 1; i >= 0; i--)
+		if (dev->_rx[i].mp_params.mp_priv)
+			/* The channel count is the idx plus 1. */
+			return i + 1;
+
+	return 0;
+}
+
 /**
  * dev_index_reserve() - allocate an ifindex in a namespace
  * @net: the applicable net namespace
@@ -11359,6 +11384,7 @@ void unregister_netdevice_many_notify(struct list_head *head,
 		dev_tcx_uninstall(dev);
 		dev_xdp_uninstall(dev);
 		bpf_dev_bound_netdev_unregister(dev);
+		dev_dmabuf_uninstall(dev);
 
 		netdev_offload_xstats_disable_all(dev);