netdev - RE: [net-next 1/7] i40e: link_down_on

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Message-ID: <1F86EBA5C8668B468CEE1C33B96E862B368B9D15@IRSMSX104.ger.corp.intel.com>
Date:   Tue, 27 Feb 2018 10:44:18 +0000
From:   "Stachura, Mariusz" <mariusz.stachura@...el.com>
To:     Jakub Kicinski <kubakici@...pl>,
        "Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "nhorman@...hat.com" <nhorman@...hat.com>,
        "sassmann@...hat.com" <sassmann@...hat.com>,
        "jogreene@...hat.com" <jogreene@...hat.com>,
        "Williams, Mitch A" <mitch.a.williams@...el.com>
Subject: RE: [net-next 1/7] i40e: link_down_on_close private flag support

>> From: Mariusz Stachura <mariusz.stachura@...el.com>
>> 
>> This patch introduces new ethtool private flag used for forcing true 
>> link state. Function i40e_force_link_state that implements this 
>> functionality was added, it sets phy_type = 0 in order to work-around 
>> firmware's LESM. False positive error messages were suppressed.
>> 
>> The ndo_open() should not succeed if there were issues with forcing 
>> link state to be UP.
>> 
>> Added I40E_PHY_TYPES_BITMASK define with all phy types OR-ed together 
>> in one bitmask.  Added after phy type definition, so it will be hard 
>> to forget to include new phy types to the bitmask.
>> 
>> CC: Jakub Kicinski <kubakici@...pl>
>> Signed-off-by: Mariusz Stachura <mariusz.stachura@...el.com>
>> Signed-off-by: Mitch Williams <mitch.a.williams@...el.com>
>> Tested-by: Andrew Bowers <andrewx.bowers@...el.com>
>> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
> 
> Thanks, from functional perspective this looks reasonable AFAICT.
> 
> We may want to have a conversation about priv flags like this at later time, since I guess more NICs won't bring the link down when netdev is closed today..  Although it maybe a larger endeavour, perhaps it would be cool to communicate to the user the reason why MAC/PHY is on in some standard way..  NC-SI and multi-host comes to mind.  
> 

Yep, the main reason for not bringing the link down is NPAR and SRIOV functionality. Link is up by default, so I think it was assumed that there is no reason to inform the user about it. The operator can use private flag to force it down, assuming she/he knows it will disrupt any undergoing traffic. I get your idea, nonetheless it was designed to use slightly different approach.

>> @@ -7524,6 +7596,9 @@ int i40e_open(struct net_device *netdev)
>>  
>>  	netif_carrier_off(netdev);
>>  
>> +	if (i40e_force_link_state(pf, true))
>> +		return -EAGAIN;
> 
> There are some minor style issues with the rest of the patch, but here you may want to (a) propagate the actual error value;
> 

The actual error value is printed inside the i40e_force_link_state() function [with KERN_ERR severity], here I wanted to let the user know the generic information that the resource is temporarily unavailable.

>>  	err = i40e_vsi_open(vsi);
>>  	if (err)
>>  		return err;
> 
> (b) undo the link state if vsi_open() fails.
> 
> Maybe that's a bit of a nitpick...
> 

I think it is, in my humble opinion there is no need to force link back down if something went wrong during further setup. Of course I'm always open for discussion :)
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