linux-kernel - Re: [PATCH net V2] amd-xgbe: Fix to ensure dependent features are toggled with RX checksum offload

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Message-ID: <c1d1ce25-8b5f-4638-bcd3-0d96c3139fd7@amd.com>
Date: Wed, 23 Apr 2025 13:27:16 +0530
From: "Badole, Vishal" <vishal.badole@....com>
To: Jacob Keller <jacob.e.keller@...el.com>, Shyam-sundar.S-k@....com,
 andrew+netdev@...n.ch, davem@...emloft.net, edumazet@...gle.com,
 kuba@...nel.org, pabeni@...hat.com, Thomas.Lendacky@....com,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: stable@...r.kernel.org, vishal.badole@....com, Raju.Rangoju@....com
Subject: Re: [PATCH net V2] amd-xgbe: Fix to ensure dependent features are
 toggled with RX checksum offload



On 4/23/2025 3:50 AM, Jacob Keller wrote:
> 
> 
> On 4/21/2025 7:04 AM, Vishal Badole wrote:
>> According to the XGMAC specification, enabling features such as Layer 3
>> and Layer 4 Packet Filtering, Split Header, Receive Side Scaling (RSS),
>> and Virtualized Network support automatically selects the IPC Full
>> Checksum Offload Engine on the receive side.
>>
>> When RX checksum offload is disabled, these dependent features must also
>> be disabled to prevent abnormal behavior caused by mismatched feature
>> dependencies.
>>
>> Ensure that toggling RX checksum offload (disabling or enabling) properly
>> disables or enables all dependent features, maintaining consistent and
>> expected behavior in the network device.
>>
> 
> My understanding based on previous changes I've made to Intel drivers,
> the netdev community opinion here is that the driver shouldn't
> automatically change user configuration like this. Instead, it should
> reject requests to disable a feature if that isn't possible due to the
> other requirements.
> 
> In this case, that means checking and rejecting disable of Rx checksum
> offload whenever the features which depend on it are enabled, and reject
> requests to enable the features when Rx checksum is disabled.

Thank you for sharing your perspective and experience with Intel 
drivers. From my understanding, the fix_features() callback in ethtool 
handles enabling and disabling the dependent features required for the 
requested feature to function correctly. It also ensures that the 
correct status is reflected in ethtool and notifies the user.

However, if the user wishes to enable or disable those dependent 
features again, they can do so using the appropriate ethtool settings.