netdev - Re: [PATCH intel-next v4] i40e: allow toggling loopback mode via ndo_set

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Date:   Tue, 22 Nov 2022 16:57:59 +0100
From:   Alexander Lobakin <alexandr.lobakin@...el.com>
To:     Leon Romanovsky <leon@...nel.org>
Cc:     Alexander Lobakin <alexandr.lobakin@...el.com>,
        Tirthendu Sarkar <tirthendu.sarkar@...el.com>,
        tirtha@...il.com, netdev@...r.kernel.org,
        intel-wired-lan@...ts.osuosl.org, magnus.karlsson@...el.com
Subject: Re: [PATCH intel-next v4] i40e: allow toggling loopback mode via ndo_set_features callback

From: Leon Romanovsky <leon@...nel.org>
Date: Tue, 22 Nov 2022 13:07:28 +0200

> On Fri, Nov 18, 2022 at 02:33:06PM +0530, Tirthendu Sarkar wrote:
> > Add support for NETIF_F_LOOPBACK. This feature can be set via:
> > $ ethtool -K eth0 loopback <on|off>
> > 
> > This sets the MAC Tx->Rx loopback.
> > 
> > This feature is used for the xsk selftests, and might have other uses
> > too.

[...]

> > @@ -12960,6 +12983,9 @@ static int i40e_set_features(struct net_device *netdev,
> >  	if (need_reset)
> >  		i40e_do_reset(pf, I40E_PF_RESET_FLAG, true);
> >  
> > +	if ((features ^ netdev->features) & NETIF_F_LOOPBACK)
> > +		return i40e_set_loopback(vsi, !!(features & NETIF_F_LOOPBACK));
> 
> Don't you need to disable loopback if NETIF_F_LOOPBACK was cleared?

0 ^ 1 == 1 -> call i40e_set_loopback()
!!(0) == 0 -> disable

> 
> > +
> >  	return 0;
> >  }
> >  
> > @@ -13722,7 +13748,7 @@ static int i40e_config_netdev(struct i40e_vsi *vsi)
> >  	if (!(pf->flags & I40E_FLAG_MFP_ENABLED))
> >  		hw_features |= NETIF_F_NTUPLE | NETIF_F_HW_TC;
> >  
> > -	netdev->hw_features |= hw_features;
> > +	netdev->hw_features |= hw_features | NETIF_F_LOOPBACK;
> >  

Reviewed-by: Alexander Lobakin <alexandr.lobakin@...el.com>

Thanks,
Olek