netdev - Re: [net-next 01/13] net/mlx5e: Print a warning when LRO feature is dropped or not allowed

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 30 Jul 2019 17:34:26 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Saeed Mahameed <saeedm@...lanox.com>
Cc:     Huy Nguyen <huyn@...lanox.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [net-next 01/13] net/mlx5e: Print a warning when LRO feature is
 dropped or not allowed

On Tue, Jul 30, 2019 at 4:08 PM Saeed Mahameed <saeedm@...lanox.com> wrote:
>
> On Tue, 2019-07-30 at 11:52 -0400, Willem de Bruijn wrote:
> > On Mon, Jul 29, 2019 at 7:50 PM Saeed Mahameed <saeedm@...lanox.com>
> > wrote:
> > > From: Huy Nguyen <huyn@...lanox.com>
> > >
> > > When user enables LRO via ethtool and if the RQ mode is legacy,
> > > mlx5e_fix_features drops the request without any explanation.
> > > Add netdev_warn to cover this case.
> > >
> > > Fixes: 6c3a823e1e9c ("net/mlx5e: RX, Remove HW LRO support in
> > > legacy RQ")
> > > Signed-off-by: Huy Nguyen <huyn@...lanox.com>
> > > Signed-off-by: Saeed Mahameed <saeedm@...lanox.com>
> > > ---
> > >  drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 5 +++--
> > >  1 file changed, 3 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> > > b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> > > index 47eea6b3a1c3..776eb46d263d 100644
> > > --- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> > > +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> > > @@ -3788,9 +3788,10 @@ static netdev_features_t
> > > mlx5e_fix_features(struct net_device *netdev,
> > >                         netdev_warn(netdev, "Dropping C-tag vlan
> > > stripping offload due to S-tag vlan\n");
> > >         }
> > >         if (!MLX5E_GET_PFLAG(params, MLX5E_PFLAG_RX_STRIDING_RQ)) {
> > > -               features &= ~NETIF_F_LRO;
> > > -               if (params->lro_en)
> > > +               if (features & NETIF_F_LRO) {
> > >                         netdev_warn(netdev, "Disabling LRO, not
> > > supported in legacy RQ\n");
> >
> > This warns about "Disabling LRO" on an enable request?
> >
>
> no, this warning appears only when lro is already enabled and might
> conflict with any other feature requested by user (hence
> mlx5e_fix_features), e.g when moving away from striding rq in this
> example, we will force lro to off.

Ok. The previous commit mentioned "totally remove LRO support in
Legacy RQ". This handles the additional case when moving a queue into
legacy mode that still had LRO enabled. I see.

>
>
> > More fundamentally, it appears that the device does not advertise
> > the feature as configurable in netdev_hw_features as of commit
> > 6c3a823e1e9c ("net/mlx5e: RX, Remove HW LRO support in
> > legacy RQ"), so shouldn't this be caught by the device driver
> > independent ethtool code?
>
> when hw doesn't support MLX5E_PFLAG_RX_STRIDING_RQ then yes, you will
> never hit this code path, but when hw does support
> MLX5E_PFLAG_RX_STRIDING_RQ and you want to turn striding rq off, then
> lro will be forced to off (if it was enabled in first space) and a
> warning msg will be shown.

Got it, thanks.