Re: [PATCH net v2 2/5] net: mvneta: fix the removal of the mqprio offload

[Maxime Chevallier <maxime.chevallier@bootlin.com>]

Hi,

On 11/3/26 13:50, Josef Schlehofer wrote:
> Deleting an offloaded mqprio qdisc leaves its traffic classes and
> per-queue rate limits in place.
> 
> mqprio_disable_offload() passes an all-zero configuration, so qopt.hw
> is 0 and mvneta_setup_mqprio() returns before it reaches the teardown
> code.
> 
> Check qopt.hw only when traffic classes are set up.
> 
> A replacement qdisc is set up before the old one is torn down.
> Replacing an offloaded mqprio qdisc with another mqprio under a new
> handle therefore loses the new configuration, as with software mqprio.
> 
> Tested on a Turris Omnia (Armada 385) with 10 Mbit/s limits on a
> 100 Mbit/s link. After the qdisc was deleted, only TX queues 0-3 were
> used and the link carried 19 Mbit/s. With this patch and the previous
> one, the queues above 3 are used again and the link reaches 94 Mbit/s.
> 
> Fixes: e7ca75fe6662 ("net: mvneta: Don't force-set the offloading flag")
> Signed-off-by: Josef Schlehofer <pepe.schlehofer@gmail.com>

Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>

Maxime

> ---
>  drivers/net/ethernet/marvell/mvneta.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> index 9b9efac2846e..79711a117c39 100644
> --- a/drivers/net/ethernet/marvell/mvneta.c
> +++ b/drivers/net/ethernet/marvell/mvneta.c
> @@ -5251,11 +5251,12 @@ static int mvneta_setup_mqprio(struct net_device *dev,
>  	int rxq, txq, tc, ret;
>  	u8 num_tc;
>  
> -	if (mqprio->qopt.hw != TC_MQPRIO_HW_OFFLOAD_TCS)
> -		return 0;
> -
>  	num_tc = mqprio->qopt.num_tc;
>  
> +	/* On removal the qdisc passes an all-zero qopt, with hw 0 */
> +	if (num_tc && mqprio->qopt.hw != TC_MQPRIO_HW_OFFLOAD_TCS)
> +		return 0;
> +
>  	if (num_tc > rxq_number)
>  		return -EINVAL;
>