From: Simon Horman <horms@kernel.org>
To: Tariq Toukan <tariqt@nvidia.com>
Cc: Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Andrew Lunn <andrew+netdev@lunn.ch>,
"David S. Miller" <davem@davemloft.net>,
Saeed Mahameed <saeedm@nvidia.com>,
Leon Romanovsky <leon@kernel.org>, Mark Bloch <mbloch@nvidia.com>,
netdev@vger.kernel.org, linux-rdma@vger.kernel.org,
linux-kernel@vger.kernel.org, Gal Pressman <gal@nvidia.com>,
Dragos Tatulea <dtatulea@nvidia.com>,
Cosmin Ratiu <cratiu@nvidia.com>
Subject: Re: [PATCH net] net/mlx5: Don't zero user_count when destroying FDB tables
Date: Tue, 28 Oct 2025 16:57:35 +0000 [thread overview]
Message-ID: <aQD1_13OxXT16XPR@horms.kernel.org> (raw)
In-Reply-To: <1761510019-938772-1-git-send-email-tariqt@nvidia.com>
On Sun, Oct 26, 2025 at 10:20:19PM +0200, Tariq Toukan wrote:
> From: Cosmin Ratiu <cratiu@nvidia.com>
>
> esw->user_count tracks how many TC rules are added on an esw via
> mlx5e_configure_flower -> mlx5_esw_get -> atomic64_inc(&esw->user_count)
>
> esw.user_count was unconditionally set to 0 in
> esw_destroy_legacy_fdb_table and esw_destroy_offloads_fdb_tables.
>
> These two together can lead to the following sequence of events:
> 1. echo 1 > /sys/class/net/eth2/device/sriov_numvfs
> - mlx5_core_sriov_configure -...-> esw_create_legacy_table ->
> atomic64_set(&esw->user_count, 0)
> 2. tc qdisc add dev eth2 ingress && \
> tc filter replace dev eth2 pref 1 protocol ip chain 0 ingress \
> handle 1 flower action ct nat zone 64000 pipe
> - mlx5e_configure_flower -> mlx5_esw_get ->
> atomic64_inc(&esw->user_count)
> 3. echo 0 > /sys/class/net/eth2/device/sriov_numvfs
> - mlx5_core_sriov_configure -..-> esw_destroy_legacy_fdb_table
> -> atomic64_set(&esw->user_count, 0)
> 4. devlink dev eswitch set pci/0000:08:00.0 mode switchdev
> - mlx5_devlink_eswitch_mode_set -> mlx5_esw_try_lock ->
> atomic64_read(&esw->user_count) == 0
> - then proceed to a WARN_ON in:
> esw_offloads_start -> mlx5_eswitch_enable_locke -> esw_offloads_enable
> -> mlx5_esw_offloads_rep_load -> mlx5e_vport_rep_load ->
> mlx5e_netdev_change_profile -> mlx5e_detach_netdev ->
> mlx5e_cleanup_nic_rx -> mlx5e_tc_nic_cleanup ->
> mlx5e_mod_hdr_tbl_destroy
>
> Fix this by not clearing out the user_count when destroying FDB tables,
> so that the check in mlx5_esw_try_lock can prevent the mode change when
> there are TC rules configured, as originally intended.
>
> Fixes: 2318b8bb94a3 ("net/mlx5: E-switch, Destroy legacy fdb table when needed")
> Signed-off-by: Cosmin Ratiu <cratiu@nvidia.com>
> Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
> Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
next prev parent reply other threads:[~2025-10-28 16:57 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-26 20:20 [PATCH net] net/mlx5: Don't zero user_count when destroying FDB tables Tariq Toukan
2025-10-28 16:57 ` Simon Horman [this message]
2025-10-30 1:00 ` patchwork-bot+netdevbpf
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