net/mlx5: Fix Unbinding uplink-netdev in switchdev mode

It is possible to unbind the uplink ETH driver while the E-Switch is
in switchdev mode. This leads to netdevice reference counting issues[1],
as the driver removal path was not designed to clean up from this state.

During uplink ETH driver removal (_mlx5e_remove), the code now waits for
any concurrent E-Switch mode transition to finish. It then removes the
REPs auxiliary device, if exists. This ensures a graceful cleanup.

[1]
unregister_netdevice: waiting for eth2 to become free. Usage count = 2
ref_tracker: netdev@00000000c912e04b has 1/1 users at
     ib_device_set_netdev+0x130/0x270 [ib_core]
     mlx5_ib_vport_rep_load+0xf4/0x3e0 [mlx5_ib]
     mlx5_esw_offloads_rep_load+0xc7/0xe0 [mlx5_core]
     esw_offloads_enable+0x583/0x900 [mlx5_core]
     mlx5_eswitch_enable_locked+0x1b2/0x290 [mlx5_core]
     mlx5_devlink_eswitch_mode_set+0x107/0x3e0 [mlx5_core]
     devlink_nl_eswitch_set_doit+0x60/0xd0
     genl_family_rcv_msg_doit+0xe0/0x130
     genl_rcv_msg+0x183/0x290
     netlink_rcv_skb+0x4b/0xf0
     genl_rcv+0x24/0x40
     netlink_unicast+0x255/0x380
     netlink_sendmsg+0x1f3/0x420
     __sock_sendmsg+0x38/0x60
     __sys_sendto+0x119/0x180
     __x64_sys_sendto+0x20/0x30

Fixes: 7a9fb35e8c ("net/mlx5e: Do not reload ethernet ports when changing eswitch mode")
Signed-off-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/1769411695-18820-2-git-send-email-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/mellanox/mlx5/core/dev.c

@@ -575,3 +575,17 @@ bool mlx5_same_hw_devs(struct mlx5_core_dev *dev, struct mlx5_core_dev *peer_dev
 	return plen && flen && flen == plen &&
 		!memcmp(fsystem_guid, psystem_guid, flen);
 }
+
+void mlx5_core_reps_aux_devs_remove(struct mlx5_core_dev *dev)
+{
+	struct mlx5_priv *priv = &dev->priv;
+
+	if (priv->adev[MLX5_INTERFACE_PROTOCOL_ETH])
+		device_lock_assert(&priv->adev[MLX5_INTERFACE_PROTOCOL_ETH]->adev.dev);
+	else
+		mlx5_core_err(dev, "ETH driver already removed\n");
+	if (priv->adev[MLX5_INTERFACE_PROTOCOL_IB_REP])
+		del_adev(&priv->adev[MLX5_INTERFACE_PROTOCOL_IB_REP]->adev);
+	if (priv->adev[MLX5_INTERFACE_PROTOCOL_ETH_REP])
+		del_adev(&priv->adev[MLX5_INTERFACE_PROTOCOL_ETH_REP]->adev);
+}

drivers/net/ethernet/mellanox/mlx5/core/en_main.c

@@ -6842,6 +6842,7 @@ static void _mlx5e_remove(struct auxiliary_device *adev)
 	struct mlx5e_priv *priv = netdev_priv(netdev);
 	struct mlx5_core_dev *mdev = edev->mdev;
 
+	mlx5_eswitch_safe_aux_devs_remove(mdev);
 	mlx5_core_uplink_netdev_set(mdev, NULL);
 
 	if (priv->profile)

drivers/net/ethernet/mellanox/mlx5/core/eswitch.h

@@ -929,6 +929,7 @@ int mlx5_esw_ipsec_vf_packet_offload_set(struct mlx5_eswitch *esw, struct mlx5_v
 int mlx5_esw_ipsec_vf_packet_offload_supported(struct mlx5_core_dev *dev,
 					       u16 vport_num);
 bool mlx5_esw_host_functions_enabled(const struct mlx5_core_dev *dev);
+void mlx5_eswitch_safe_aux_devs_remove(struct mlx5_core_dev *dev);
 #else  /* CONFIG_MLX5_ESWITCH */
 /* eswitch API stubs */
 static inline int  mlx5_eswitch_init(struct mlx5_core_dev *dev) { return 0; }
@@ -1012,6 +1013,9 @@ mlx5_esw_vport_vhca_id(struct mlx5_eswitch *esw, u16 vportn, u16 *vhca_id)
 	return false;
 }
 
+static inline void
+mlx5_eswitch_safe_aux_devs_remove(struct mlx5_core_dev *dev) {}
+
 #endif /* CONFIG_MLX5_ESWITCH */
 
 #endif /* __MLX5_ESWITCH_H__ */

drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c

@@ -3981,6 +3981,32 @@ static bool mlx5_devlink_switchdev_active_mode_change(struct mlx5_eswitch *esw,
 	return true;
 }
 
+#define MLX5_ESW_HOLD_TIMEOUT_MS 7000
+#define MLX5_ESW_HOLD_RETRY_DELAY_MS 500
+
+void mlx5_eswitch_safe_aux_devs_remove(struct mlx5_core_dev *dev)
+{
+	unsigned long timeout;
+	bool hold_esw = true;
+
+	/* Wait for any concurrent eswitch mode transition to complete. */
+	if (!mlx5_esw_hold(dev)) {
+		timeout = jiffies + msecs_to_jiffies(MLX5_ESW_HOLD_TIMEOUT_MS);
+		while (!mlx5_esw_hold(dev)) {
+			if (!time_before(jiffies, timeout)) {
+				hold_esw = false;
+				break;
+			}
+			msleep(MLX5_ESW_HOLD_RETRY_DELAY_MS);
+		}
+	}
+	if (hold_esw) {
+		if (mlx5_eswitch_mode(dev) == MLX5_ESWITCH_OFFLOADS)
+			mlx5_core_reps_aux_devs_remove(dev);
+		mlx5_esw_release(dev);
+	}
+}
+
 int mlx5_devlink_eswitch_mode_set(struct devlink *devlink, u16 mode,
 				  struct netlink_ext_ack *extack)
 {

drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.h

@@ -290,6 +290,7 @@ int mlx5_register_device(struct mlx5_core_dev *dev);
 void mlx5_unregister_device(struct mlx5_core_dev *dev);
 void mlx5_dev_set_lightweight(struct mlx5_core_dev *dev);
 bool mlx5_dev_is_lightweight(struct mlx5_core_dev *dev);
+void mlx5_core_reps_aux_devs_remove(struct mlx5_core_dev *dev);
 
 void mlx5_fw_reporters_create(struct mlx5_core_dev *dev);
 int mlx5_query_mtpps(struct mlx5_core_dev *dev, u32 *mtpps, u32 mtpps_size);