netdev - Re: [PATCH net 7/9] mlxsw: spectrum_acl

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Date: Wed, 24 Apr 2024 15:52:32 +0100
From: Simon Horman <horms@...nel.org>
To: Petr Machata <petrm@...dia.com>
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, Ido Schimmel <idosch@...dia.com>,
	Jiri Pirko <jiri@...nulli.us>, Alexander Zubkov <green@...tor.net>,
	mlxsw@...dia.com
Subject: Re: [PATCH net 7/9] mlxsw: spectrum_acl_tcam: Fix warning during
 rehash

On Mon, Apr 22, 2024 at 05:26:00PM +0200, Petr Machata wrote:
> From: Ido Schimmel <idosch@...dia.com>
> 
> As previously explained, the rehash delayed work migrates filters from
> one region to another. This is done by iterating over all chunks (all
> the filters with the same priority) in the region and in each chunk
> iterating over all the filters.
> 
> When the work runs out of credits it stores the current chunk and entry
> as markers in the per-work context so that it would know where to resume
> the migration from the next time the work is scheduled.
> 
> Upon error, the chunk marker is reset to NULL, but without resetting the
> entry markers despite being relative to it. This can result in migration
> being resumed from an entry that does not belong to the chunk being
> migrated. In turn, this will eventually lead to a chunk being iterated
> over as if it is an entry. Because of how the two structures happen to
> be defined, this does not lead to KASAN splats, but to warnings such as
> [1].
> 
> Fix by creating a helper that resets all the markers and call it from
> all the places the currently only reset the chunk marker. For good
> measures also call it when starting a completely new rehash. Add a
> warning to avoid future cases.
> 
> [1]
> WARNING: CPU: 7 PID: 1076 at drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_keys.c:407 mlxsw_afk_encode+0x242/0x2f0
> Modules linked in:
> CPU: 7 PID: 1076 Comm: kworker/7:24 Tainted: G        W          6.9.0-rc3-custom-00880-g29e61d91b77b #29
> Hardware name: Mellanox Technologies Ltd. MSN3700/VMOD0005, BIOS 5.11 01/06/2019
> Workqueue: mlxsw_core mlxsw_sp_acl_tcam_vregion_rehash_work
> RIP: 0010:mlxsw_afk_encode+0x242/0x2f0
> [...]
> Call Trace:
>  <TASK>
>  mlxsw_sp_acl_atcam_entry_add+0xd9/0x3c0
>  mlxsw_sp_acl_tcam_entry_create+0x5e/0xa0
>  mlxsw_sp_acl_tcam_vchunk_migrate_all+0x109/0x290
>  mlxsw_sp_acl_tcam_vregion_rehash_work+0x6c/0x470
>  process_one_work+0x151/0x370
>  worker_thread+0x2cb/0x3e0
>  kthread+0xd0/0x100
>  ret_from_fork+0x34/0x50
>  </TASK>
> 
> Fixes: 6f9579d4e302 ("mlxsw: spectrum_acl: Remember where to continue rehash migration")
> Signed-off-by: Ido Schimmel <idosch@...dia.com>
> Tested-by: Alexander Zubkov <green@...tor.net>
> Reviewed-by: Petr Machata <petrm@...dia.com>
> Signed-off-by: Petr Machata <petrm@...dia.com>

Reviewed-by: Simon Horman <horms@...nel.org>