netdev - Re: [RFC PATCH net-next 1/8] ethtool: Add ability to control transceiver modules' low power mode

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Date:   Tue, 10 Aug 2021 22:24:21 +0000
From:   "Keller, Jacob E" <jacob.e.keller@...el.com>
To:     Jakub Kicinski <kuba@...nel.org>
CC:     Ido Schimmel <idosch@...sch.org>, Andrew Lunn <andrew@...n.ch>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "mkubecek@...e.cz" <mkubecek@...e.cz>,
        "pali@...nel.org" <pali@...nel.org>,
        "vadimp@...dia.com" <vadimp@...dia.com>,
        "mlxsw@...dia.com" <mlxsw@...dia.com>,
        Ido Schimmel <idosch@...dia.com>
Subject: Re: [RFC PATCH net-next 1/8] ethtool: Add ability to control
 transceiver modules' low power mode

On 8/10/2021 3:06 PM, Jakub Kicinski wrote:
> On Tue, 10 Aug 2021 22:00:51 +0000 Keller, Jacob E wrote:
>>>> Jake do you know what the use cases for Intel are? Are they SFP, MAC,
>>>> or NC-SI related?  
>>>
>>> I went through all the Intel drivers that implement these operations and
>>> I believe you are talking about these commits:
>>>
>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c3880bd159d431d06b687b0b5ab22e24e6ef0070
>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=d5ec9e2ce41ac198de2ee18e0e529b7ebbc67408
>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ab4ab73fc1ec6dec548fa36c5e383ef5faa7b4c1
>>>
>>> There isn't too much information about the motivation, but maybe it has
>>> something to do with multi-host controllers where you want to prevent
>>> one host from taking the physical link down for all the other hosts
>>> sharing it? I remember such issues with mlx5.
>>>   
>>
>> Ok, I found some more information here. The primary motivation of the
>> changes in the i40e and ice drivers is from customer requests asking to
>> have the link go down when the port is administratively disabled. This
>> is because if the link is down then the switch on the other side will
>> see the port not having link and will stop trying to send traffic to it.
>>
>> As far as I can tell, the reason its a flag is because some users wanted
>> the behavior the other way.
>>
>> I'm not sure it's really related to the behavior here.
>>
>> For what it's worth, I'm in favor of containing things like this into
>> ethtool as well.
> 
> I think the question was the inverse - why not always shut down the
> port if the interface is brought down?
> 

So far the best I've found after digging is that forcing total shutdown
causes manageability and VF traffic to stop. Other customers want this
traffic to continue even when the PF port is brought down.

Thanks,
Jake