netdev - Re: [PATCH net] Revert "net/mlx5e: Update and set Xon/Xoff upon MTU set"

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Message-ID: <c5846bcd-0f78-4b9d-b765-529f4c985edb@gmail.com>
Date: Tue, 30 Sep 2025 08:28:51 +0300
From: Tariq Toukan <ttoukan.linux@...il.com>
To: Jakub Kicinski <kuba@...nel.org>, davem@...emloft.net
Cc: netdev@...r.kernel.org, edumazet@...gle.com, pabeni@...hat.com,
 andrew+netdev@...n.ch, horms@...nel.org, saeedm@...dia.com, leon@...nel.org,
 tariqt@...dia.com, mbloch@...dia.com, alazar@...dia.com,
 linux-rdma@...r.kernel.org
Subject: Re: [PATCH net] Revert "net/mlx5e: Update and set Xon/Xoff upon MTU
 set"



On 29/09/2025 21:15, Jakub Kicinski wrote:
> This reverts commit ceddedc969f0532b7c62ca971ee50d519d2bc0cb.
> 
> Commit in question breaks the mapping of PGs to pools for some SKUs.
> Specifically multi-host NICs seem to be shipped with a custom buffer
> configuration which maps the lossy PG to pool 4. But the bad commit
> overrides this with pool 0 which does not have sufficient buffer space
> reserved. Resulting in ~40% packet loss. The commit also breaks BMC /
> OOB connection completely (100% packet loss).
> 
> Revert, similarly to commit 3fbfe251cc9f ("Revert "net/mlx5e: Update and
> set Xon/Xoff upon port speed set""). The breakage is exactly the same,
> the only difference is that quoted commit would break the NIC immediately
> on boot, and the currently reverted commit only when MTU is changed.
> 
> Note: "good" kernels do not restore the configuration, so downgrade isn't
> enough to recover machines. A NIC power cycle seems to be necessary to
> return to a healthy state (or overriding the relevant registers using
> a custom patch).
> 
> Fixes: ceddedc969f0 ("net/mlx5e: Update and set Xon/Xoff upon MTU set")
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
> ---

Reviewed-by: Tariq Toukan <tariqt@...dia.com>

Thanks for your revert.
We'll post fixed versions when ready.

> CC: saeedm@...dia.com
> CC: leon@...nel.org
> CC: tariqt@...dia.com
> CC: mbloch@...dia.com
> CC: alazar@...dia.com
> CC: linux-rdma@...r.kernel.org
> ---