netdev - Re: [PATCH net v1 1/3] taprio: Fix enabling offload with wrong number of traffic classes

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Message-ID: <CA+h21hob4SxGAprR5qXA+DP5VAQxmwEewP7GBfSGLSi18GdgMA@mail.gmail.com>
Date:   Sat, 25 Jan 2020 18:53:04 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Vinicius Costa Gomes <vinicius.gomes@...el.com>
Cc:     netdev <netdev@...r.kernel.org>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        "David S. Miller" <davem@...emloft.net>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Po Liu <po.liu@....com>
Subject: Re: [PATCH net v1 1/3] taprio: Fix enabling offload with wrong number
 of traffic classes

On Sat, 25 Jan 2020 at 02:53, Vinicius Costa Gomes
<vinicius.gomes@...el.com> wrote:
>
> If the driver implementing taprio offloading depends on the value of
> the network device number of traffic classes (dev->num_tc) for
> whatever reason, it was going to receive the value zero. The value was
> only set after the offloading function is called.
>
> So, moving setting the number of traffic classes to before the
> offloading function is called fixes this issue. This is safe because
> this only happens when taprio is instantiated (we don't allow this
> configuration to be changed without first removing taprio).
>
> Fixes: 9c66d1564676 ("taprio: Add support for hardware offloading")
> Reported-by: Po Liu <po.liu@....com>
> Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>
> ---

Acked-by: Vladimir Oltean <vladimir.oltean@....com>

>  net/sched/sch_taprio.c | 26 +++++++++++++-------------
>  1 file changed, 13 insertions(+), 13 deletions(-)
>
> diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
> index c609373c8661..ad0dadcfcdba 100644
> --- a/net/sched/sch_taprio.c
> +++ b/net/sched/sch_taprio.c
> @@ -1444,6 +1444,19 @@ static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
>
>         taprio_set_picos_per_byte(dev, q);
>
> +       if (mqprio) {
> +               netdev_set_num_tc(dev, mqprio->num_tc);
> +               for (i = 0; i < mqprio->num_tc; i++)
> +                       netdev_set_tc_queue(dev, i,
> +                                           mqprio->count[i],
> +                                           mqprio->offset[i]);
> +
> +               /* Always use supplied priority mappings */
> +               for (i = 0; i <= TC_BITMASK; i++)
> +                       netdev_set_prio_tc_map(dev, i,
> +                                              mqprio->prio_tc_map[i]);
> +       }
> +
>         if (FULL_OFFLOAD_IS_ENABLED(taprio_flags))
>                 err = taprio_enable_offload(dev, mqprio, q, new_admin, extack);
>         else
> @@ -1471,19 +1484,6 @@ static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
>                 q->advance_timer.function = advance_sched;
>         }
>
> -       if (mqprio) {
> -               netdev_set_num_tc(dev, mqprio->num_tc);
> -               for (i = 0; i < mqprio->num_tc; i++)
> -                       netdev_set_tc_queue(dev, i,
> -                                           mqprio->count[i],
> -                                           mqprio->offset[i]);
> -
> -               /* Always use supplied priority mappings */
> -               for (i = 0; i <= TC_BITMASK; i++)
> -                       netdev_set_prio_tc_map(dev, i,
> -                                              mqprio->prio_tc_map[i]);
> -       }
> -
>         if (FULL_OFFLOAD_IS_ENABLED(taprio_flags)) {
>                 q->dequeue = taprio_dequeue_offload;
>                 q->peek = taprio_peek_offload;
> --
> 2.25.0
>