netdev - Re: [PATCH] net/mlx5e: Fix zero table prio set by user.

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Date:   Fri, 26 Jul 2019 15:19:11 +0300
From:   Or Gerlitz <gerlitz.or@...il.com>
To:     Saeed Mahameed <saeedm@...lanox.com>,
        "wenxu@...oud.cn" <wenxu@...oud.cn>
Cc:     Roi Dayan <roid@...lanox.com>, Mark Bloch <markb@...lanox.com>,
        Paul Blakey <paulb@...lanox.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH] net/mlx5e: Fix zero table prio set by user.

On Fri, Jul 26, 2019 at 12:24 AM Saeed Mahameed <saeedm@...lanox.com> wrote:
>
> On Thu, 2019-07-25 at 19:24 +0800, wenxu@...oud.cn wrote:
> > From: wenxu <wenxu@...oud.cn>
> >
> > The flow_cls_common_offload prio is zero
> >
> > It leads the invalid table prio in hw.
> >
> > Error: Could not process rule: Invalid argument
> >
> > kernel log:
> > mlx5_core 0000:81:00.0: E-Switch: Failed to create FDB Table err -22
> > (table prio: 65535, level: 0, size: 4194304)
> >
> > table_prio = (chain * FDB_MAX_PRIO) + prio - 1;
> > should check (chain * FDB_MAX_PRIO) + prio is not 0
> >
> > Signed-off-by: wenxu <wenxu@...oud.cn>
> > ---
> >  drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git
> > a/drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c
> > b/drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c
> > index 089ae4d..64ca90f 100644
> > --- a/drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c
> > +++ b/drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c
> > @@ -970,7 +970,9 @@ static int esw_add_fdb_miss_rule(struct
>
> this piece of code isn't in this function, weird how it got to the
> diff, patch applies correctly though !
>
> > mlx5_eswitch *esw)
> >               flags |= (MLX5_FLOW_TABLE_TUNNEL_EN_REFORMAT |
> >                         MLX5_FLOW_TABLE_TUNNEL_EN_DECAP);
> >
> > -     table_prio = (chain * FDB_MAX_PRIO) + prio - 1;
> > +     table_prio = (chain * FDB_MAX_PRIO) + prio;
> > +     if (table_prio)
> > +             table_prio = table_prio - 1;
> >
>
> This is black magic, even before this fix.
> this -1 seems to be needed in order to call
> create_next_size_table(table_prio) with the previous "table prio" ?
> (table_prio - 1)  ?
>
> The whole thing looks wrong to me since when prio is 0 and chain is 0,
> there is not such thing table_prio - 1.
>
> mlnx eswitch guys in the cc, please advise.

basically, prio 0 is not something we ever get in the driver, since if
user space
specifies 0, the kernel generates some random non-zero prio, and we support
only prios 1-16 -- Wenxu -- what do you run to get this error?



>
> Thanks,
> Saeed.
>
> >       /* create earlier levels for correct fs_core lookup when
> >        * connecting tables