Re: [PATCH net-next] ethtool: tsconfig: always take rtnl_lock

[Jacob Keller <jacob.e.keller@intel.com>]

On 6/11/2026 1:03 PM, Jakub Kicinski wrote:
> mlx5 throws ASSERT_RTNL() warnings on timestamp config, because
> it tries to update features. mlx5e_hwtstamp_set() calls
> netdev_update_features().
> 
> I missed this while grepping the drivers because tsconfig goes
> through ndo_hwtstamp_set/get, not ethtool ops, even tho the new
> uAPI is in ethtool Netlink. We could add a dedicated opt out bit
> for mlx5, but NDOs were not supposed to be part of the ethtool locking
> conversion in the first place.

Makes sense, even if we have plans to improve that in the future we
didn't plan to change it right now.

Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>

> 
> The mlx5 features update is related to the "compressed CQE" format
> which lacks timestamp, apparently. See commit c0194e2d0ef0 ("net/mlx5e:
> Disable rxhash when CQE compress is enabled").
> 
> Fixes: 6e9e2eed4f39 ("net: ethtool: Add support for tsconfig command to get/set hwtstamp config")
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> ---
> CC: andrew@lunn.ch
> CC: gal@nvidia.com
> CC: jacob.e.keller@intel.com
> CC: sdf@fomichev.me
> CC: kory.maincent@bootlin.com
> ---
>  net/ethtool/common.h | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/net/ethtool/common.h b/net/ethtool/common.h
> index e3052972f953..2b3847f00801 100644
> --- a/net/ethtool/common.h
> +++ b/net/ethtool/common.h
> @@ -113,6 +113,13 @@ ethtool_nl_msg_needs_rtnl(const struct net_device *dev, u8 cmd)
>  		return ops->op_needs_rtnl & ETHTOOL_OP_NEEDS_RTNL_SPAUSEPARAM;
>  	case ETHTOOL_MSG_RSS_SET:
>  		return ops->op_needs_rtnl & ETHTOOL_OP_NEEDS_RTNL_RSS;
> +	case ETHTOOL_MSG_TSCONFIG_GET:
> +	case ETHTOOL_MSG_TSCONFIG_SET:
> +		/* tsconfig calls ndos (ndo_hwtstamp_set/get), not ethtool ops.
> +		 * Also, there is no corresponding ethtool ioctl, therefore
> +		 * these cases are Netlink-only.
> +		 */
> +		return true;
>  	}
>  	return false;
>  }