netdev - Re: [PATCH net-next 2/2] mlx4/en_netdev: call notifiers when hw_enc

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Date:   Thu, 25 Jul 2019 21:27:02 +0000
From:   Saeed Mahameed <saeedm@...lanox.com>
To:     "dcaratti@...hat.com" <dcaratti@...hat.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Tariq Toukan <tariqt@...lanox.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     Eran Ben Elisha <eranbe@...lanox.com>
Subject: Re: [PATCH net-next 2/2] mlx4/en_netdev: call notifiers when
 hw_enc_features change

On Thu, 2019-07-25 at 14:25 +0200, Davide Caratti wrote:
> On Wed, 2019-07-24 at 20:47 +0000, Saeed Mahameed wrote:
> > On Wed, 2019-07-24 at 16:02 +0200, Davide Caratti wrote:
> > > ensure to call netdev_features_change() when the driver flips its
> > > hw_enc_features bits.
> > > 
> > > Signed-off-by: Davide Caratti <dcaratti@...hat.com>
> > 
> > The patch is correct, 
> 
> hello Saeed, and thanks for looking at this!
> 
> > but can you explain how did you come to this ? 
> > did you encounter any issue with the current code ?
> > 
> > I am asking just because i think the whole dynamic changing of dev-
> > > hw_enc_features is redundant since mlx4 has the featutres_check
> > callback.
> 
> we need it to ensure that vlan_transfer_features() updates
> the (new) value of hw_enc_features in the overlying vlan: otherwise,
> segmentation will happen anyway when skb passes from vxlan to vlan,
> if the
> vxlan is added after the vlan device has been created (see:
> 7dad9937e064
> ("net: vlan: add support for tunnel offload") ).
> 

but in previous patch you made sure that the vlan always sees the
correct hw_enc_features on driver load, we don't need to have this
dynamic update mechanism, features_check ndo should take care of
protocols we don't support.

> thanks!