linux-stable.git/net/core/netdev_queues.c, branch v7.2 Linux kernel stable tree net: expect instance lock in netdev_queue_get_dma_dev() 2026-08-10T22:54:42+00:00 Jakub Kicinski kuba@kernel.org 2026-08-06T22:56:26+00:00 92465f46f3c3a92e4758af20d2363b7adc43e1f5 netdev_queue_get_dma_dev() uses "compat" locking assert which wants either the rtnl_lock or netdev instance lock. This is not right, the callers are taking the instance lock unconditionally. All entry points for queue config are purely instance locked. In other words the callers use netdev_get_by_index_lock(), not netdev_get_by_index_lock_ops_compat(). All the state we will access is effectively instance lock protected (it's const for devices which are not ops-locked). Update the assert to avoid false positive warnings. Cc: stable@vger.kernel.org Fixes: b6c5f9454ef34 ("io_uring/zcrx: call netdev_queue_get_dma_dev() under instance lock") Reported-by: syzbot+a78926bdac2adb52dc0e@syzkaller.appspotmail.com Reviewed-by: Simon Horman <horms@kernel.org> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://patch.msgid.link/20260806225627.3998672-1-kuba@kernel.org Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
netdev_queue_get_dma_dev() uses "compat" locking assert which wants
either the rtnl_lock or netdev instance lock. This is not right,
the callers are taking the instance lock unconditionally. All entry
points for queue config are purely instance locked.

In other words the callers use netdev_get_by_index_lock(), not
netdev_get_by_index_lock_ops_compat(). All the state we will
access is effectively instance lock protected (it's const for
devices which are not ops-locked).

Update the assert to avoid false positive warnings.

Cc: stable@vger.kernel.org
Fixes: b6c5f9454ef34 ("io_uring/zcrx: call netdev_queue_get_dma_dev() under instance lock")
Reported-by: syzbot+a78926bdac2adb52dc0e@syzkaller.appspotmail.com
Reviewed-by: Simon Horman <horms@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://patch.msgid.link/20260806225627.3998672-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
net: rename netdev_ops_assert_locked() 2026-06-04T21:04:55+00:00 Jakub Kicinski kuba@kernel.org 2026-06-03T01:28:30+00:00 251bc9db88fb351ea2dfbd976c4e6aaae6507a91 Jakub suggests renaming the existing assert to match the netdev_lock_ops_compat() semantics. We want netdev_assert_locked_ops() to mean - if the driver is ops locked - check that it's holding the device lock. The existing helper check for either ops lock or rtnl_lock, which is the locking behavior of netdev_lock_ops_compat(). The reason for naming divergence is likely that netdev_ops_assert_locked() predated the _compat() helpers. Suggested-by: Jakub Sitnicki <jakub@cloudflare.com> Reviewed-by: Nicolai Buchwitz <nb@tipi-net.de> Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com> Acked-by: Stanislav Fomichev <sdf@fomichev.me> Link: https://patch.msgid.link/20260603012840.2254293-2-kuba@kernel.org Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
Jakub suggests renaming the existing assert to match
the netdev_lock_ops_compat() semantics.

We want netdev_assert_locked_ops() to mean - if the driver
is ops locked - check that it's holding the device lock.

The existing helper check for either ops lock or rtnl_lock,
which is the locking behavior of netdev_lock_ops_compat().

The reason for naming divergence is likely that
netdev_ops_assert_locked() predated the _compat() helpers.

Suggested-by: Jakub Sitnicki <jakub@cloudflare.com>
Reviewed-by: Nicolai Buchwitz <nb@tipi-net.de>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20260603012840.2254293-2-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
net: remove the netif_get_rx_queue_lease_locked() helpers 2026-04-10T01:26:28+00:00 Jakub Kicinski kuba@kernel.org 2026-04-08T22:12:51+00:00 581d28606cdd51c5da06330e8fb97476503cd74d The netif_get_rx_queue_lease_locked() API hides the locking and the descend onto the leased queue. Making the code harder to follow (at least to me). Remove the API and open code the descend a bit. Most of the code now looks like: if (!leased) return __helper(x); hw_rxq = .. netdev_lock(hw_rxq->dev); ret = __helper(x); netdev_unlock(hw_rxq->dev); return ret; Of course if we have more code paths that need the wrapping we may need to revisit. For now, IMHO, having to know what netif_get_rx_queue_lease_locked() does is not worth the 20LoC it saves. Link: https://patch.msgid.link/20260408151251.72bd2482@kernel.org Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
The netif_get_rx_queue_lease_locked() API hides the locking
and the descend onto the leased queue. Making the code
harder to follow (at least to me). Remove the API and open
code the descend a bit. Most of the code now looks like:

 if (!leased)
     return __helper(x);

 hw_rxq = ..
 netdev_lock(hw_rxq->dev);
 ret = __helper(x);
 netdev_unlock(hw_rxq->dev);

 return ret;

Of course if we have more code paths that need the wrapping
we may need to revisit. For now, IMHO, having to know what
netif_get_rx_queue_lease_locked() does is not worth the 20LoC
it saves.

Link: https://patch.msgid.link/20260408151251.72bd2482@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
net: Proxy netdev_queue_get_dma_dev for leased queues 2026-04-10T01:21:46+00:00 David Wei dw@davidwei.uk 2026-04-02T23:10:24+00:00 222b5566a02dbf136291376e4aa1806213fe9fa2 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> Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org> Link: https://patch.msgid.link/20260402231031.447597-8-daniel@iogearbox.net Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
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>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://patch.msgid.link/20260402231031.447597-8-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
net: Implement netdev_nl_queue_create_doit 2026-04-10T01:21:45+00:00 Daniel Borkmann daniel@iogearbox.net 2026-04-02T23:10:19+00:00 d04686d9bc86432ea3008d5f358373d8466d1943 Implement netdev_nl_queue_create_doit which creates a new rx queue in a virtual netdev and then leases it to a rx queue in a physical netdev. Example with ynl client: # ynl --family netdev --output-json --do queue-create \ --json '{"ifindex": 8, "type": "rx", "lease": {"ifindex": 4, "queue": {"type": "rx", "id": 15}}}' {'id': 1} Note that the netdevice locking order is always from the virtual to the physical device. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Co-developed-by: David Wei <dw@davidwei.uk> Signed-off-by: David Wei <dw@davidwei.uk> Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org> Link: https://patch.msgid.link/20260402231031.447597-3-daniel@iogearbox.net Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
Implement netdev_nl_queue_create_doit which creates a new rx queue in a
virtual netdev and then leases it to a rx queue in a physical netdev.

Example with ynl client:

  # ynl --family netdev --output-json --do queue-create \
        --json '{"ifindex": 8, "type": "rx", "lease": {"ifindex": 4, "queue": {"type": "rx", "id": 15}}}'
  {'id': 1}

Note that the netdevice locking order is always from the virtual to
the physical device.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Co-developed-by: David Wei <dw@davidwei.uk>
Signed-off-by: David Wei <dw@davidwei.uk>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://patch.msgid.link/20260402231031.447597-3-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
queue_api: add support for fetching per queue DMA dev 2025-08-28T23:05:31+00:00 Dragos Tatulea dtatulea@nvidia.com 2025-08-27T14:39:55+00:00 13d8e05adf9dd06c74fcc6ba42ec4bf780fd557f 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: Dragos Tatulea <dtatulea@nvidia.com> Reviewed-by: Pavel Begunkov <asml.silence@gmail.com> Reviewed-by: Mina Almasry <almasrymina@google.com> Link: https://patch.msgid.link/20250827144017.1529208-3-dtatulea@nvidia.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
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: Dragos Tatulea <dtatulea@nvidia.com>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: Mina Almasry <almasrymina@google.com>
Link: https://patch.msgid.link/20250827144017.1529208-3-dtatulea@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>