netdev - Re: [RFC] hv_netvsc: automatically name slave VF network device

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Message-ID: <20171219155353.4aa0fe9b@cakuba.netronome.com>
Date:   Tue, 19 Dec 2017 15:53:53 -0800
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     "Samudrala, Sridhar" <sridhar.samudrala@...el.com>,
        netdev@...r.kernel.org, Stephen Hemminger <sthemmin@...rosoft.com>
Subject: Re: [RFC] hv_netvsc: automatically name slave VF network device

On Tue, 19 Dec 2017 15:44:05 -0800, Stephen Hemminger wrote:
> On Tue, 19 Dec 2017 15:20:57 -0800
> Jakub Kicinski <jakub.kicinski@...ronome.com> wrote:
> 
> > On Tue, 19 Dec 2017 14:50:17 -0800, Stephen Hemminger wrote:  
> > > On Tue, 19 Dec 2017 14:44:37 -0800
> > > "Samudrala, Sridhar" <sridhar.samudrala@...el.com> wrote:
> > >     
> > > >  -static void __netvsc_vf_setup(struct net_device *ndev,      
> > > > > -			      struct net_device *vf_netdev)
> > > > > -{
> > > > > -	int ret;
> > > > > +	/* set the name of VF device based on upper device name */
> > > > > +	snprintf(vf_name, IFNAMSIZ, "%s_vf", ndev->name);
> > > > > +	ret = dev_change_name(vf_netdev, vf_name);
> > > > > +	if (ret != 0)
> > > > > +		netdev_warn(vf_netdev,
> > > > > +			    "can not rename device: (%d)\n", ret);        
> > > > 
> > > > It is possible that upper device name can change after this call.  I 
> > > > noticed this
> > > > when i tried this approach with virtio_net.
> > > > 
> > > > Also, what should happen if the upper device is unloaded? Should we rename
> > > > the VF name?      
> > > 
> > > Yes upper device can change name. So sure, netdevice could trap that
> > > in callback (it already has notifier) and rename VF. Will add that in V2.
> > > 
> > > If upper device is unloaded then it is already decoupled from the VF.
> > > There is no good value to change it back to. The orignal name probably
> > > has been reused by then.    
> > 
> > Both of those issues would be solved by just exposing phys_port_name
> > from the VF driver, and letting systemd do its thing independent of 
> > magic bonds.
> > 
> > Reluctance to do driver work aside :/  
> 
> The port name for Mellanox driver is already set in the driver as a numeric value.
> It indicates which port is used.
> This won't work.

You must be looking at representor ndos.  I don't think MLX NIC drivers
are implementing phys_port_name for normal netdevs at all today.