Subject: Re: [PATCH net-next v16 06/12] virtio_net: Create a FF group for ethtool steering

From: "Michael S. Tsirkin" <[email-masked]>
Date: Thu, 22 Jan 2026 16:51:56 -0500

On Wed, Jan 21, 2026 at 04:06:46PM -0600, Daniel Jurgens wrote:
> All ethtool steering rules will go in one group, create it during
> initialization.
> 
> Signed-off-by: Daniel Jurgens <[email-masked]>
> Reviewed-by: Parav Pandit <[email-masked]>
> Reviewed-by: Shahar Shitrit <[email-masked]>
> Reviewed-by: Xuan Zhuo <[email-masked]>
> 
> ---
> v4: Documented UAPI
> ---
> ---
>  drivers/net/virtio_net.c           | 29 +++++++++++++++++++++++++++++
>  include/uapi/linux/virtio_net_ff.h | 15 +++++++++++++++
>  2 files changed, 44 insertions(+)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 03bd3d2c2b0e..b406f5f1c75e 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -286,6 +286,9 @@ static const struct virtnet_stat_desc virtnet_stats_tx_speed_desc_qstat[] = {
>  	VIRTNET_STATS_DESC_TX_QSTAT(speed, ratelimit_packets, hw_drop_ratelimits),
>  };
>  
> +#define VIRTNET_FF_ETHTOOL_GROUP_PRIORITY 1
> +#define VIRTNET_FF_MAX_GROUPS 1
> +
>  struct virtnet_ff {
>  	struct virtio_device *vdev;
>  	bool ff_supported;
> @@ -5724,6 +5727,7 @@ static int virtnet_ff_init(struct virtnet_ff *ff, struct virtio_device *vdev)
>  	size_t ff_mask_size = sizeof(struct virtio_net_ff_cap_mask_data) +
>  			      sizeof(struct virtio_net_ff_selector) *
>  			      VIRTIO_NET_FF_MASK_TYPE_MAX;
> +	struct virtio_net_resource_obj_ff_group ethtool_group = {};
>  	struct virtio_admin_cmd_query_cap_id_result *cap_id_list;
>  	struct virtio_net_ff_selector *sel;
>  	unsigned long sel_types = 0;
> @@ -5808,6 +5812,12 @@ static int virtnet_ff_init(struct virtnet_ff *ff, struct virtio_device *vdev)
>  	if (err)
>  		goto err_ff_action;
>  
> +	if (le32_to_cpu(ff->ff_caps->groups_limit) < VIRTNET_FF_MAX_GROUPS) {
> +		err = -ENOSPC;
> +		goto err_ff_action;
> +	}
> +	ff->ff_caps->groups_limit = cpu_to_le32(VIRTNET_FF_MAX_GROUPS);
> +
>  	err = virtio_admin_cap_set(vdev,
>  				   VIRTIO_NET_FF_RESOURCE_CAP,
>  				   ff->ff_caps,
> @@ -5854,6 +5864,19 @@ static int virtnet_ff_init(struct virtnet_ff *ff, struct virtio_device *vdev)
>  	if (err)
>  		goto err_ff_action;
>  
> +	ethtool_group.group_priority = cpu_to_le16(VIRTNET_FF_ETHTOOL_GROUP_PRIORITY);
> +
> +	/* Use priority for the object ID. */
> +	err = virtio_admin_obj_create(vdev,
> +				      VIRTIO_NET_RESOURCE_OBJ_FF_GROUP,
> +				      VIRTNET_FF_ETHTOOL_GROUP_PRIORITY,

This (3rd param to virtio_admin_obj_create)
is the object ID actually. Setting this to 1 means it is outside
of range for group limit which should be 0...limit - 1 and limit is 1.

don't you mean 0?

> +				      VIRTIO_ADMIN_GROUP_TYPE_SELF,
> +				      0,
> +				      &ethtool_group,
> +				      sizeof(ethtool_group));
> +	if (err)
> +		goto err_ff_action;
> +
>  	ff->vdev = vdev;
>  	ff->ff_supported = true;
>  
> @@ -5881,6 +5904,12 @@ static void virtnet_ff_cleanup(struct virtnet_ff *ff)
>  	if (!ff->ff_supported)
>  		return;
>  
> +	virtio_admin_obj_destroy(ff->vdev,
> +				 VIRTIO_NET_RESOURCE_OBJ_FF_GROUP,
> +				 VIRTNET_FF_ETHTOOL_GROUP_PRIORITY,
> +				 VIRTIO_ADMIN_GROUP_TYPE_SELF,

same

> +				 0);
> +
>  	kfree(ff->ff_actions);
>  	kfree(ff->ff_mask);
>  	kfree(ff->ff_caps);
> diff --git a/include/uapi/linux/virtio_net_ff.h b/include/uapi/linux/virtio_net_ff.h
> index d025e252ee26..66af9ecdb674 100644
> --- a/include/uapi/linux/virtio_net_ff.h
> +++ b/include/uapi/linux/virtio_net_ff.h
> @@ -11,6 +11,8 @@
>  #define VIRTIO_NET_FF_SELECTOR_CAP 0x801
>  #define VIRTIO_NET_FF_ACTION_CAP 0x802
>  
> +#define VIRTIO_NET_RESOURCE_OBJ_FF_GROUP 0x0200
> +
>  /**
>   * struct virtio_net_ff_cap_data - Flow filter resource capability limits
>   * @groups_limit: maximum number of flow filter groups supported by the device
> @@ -87,4 +89,17 @@ struct virtio_net_ff_actions {
>  	__u8 reserved[7];
>  	__u8 actions[];
>  };
> +
> +/**
> + * struct virtio_net_resource_obj_ff_group - Flow filter group object
> + * @group_priority: priority of the group used to order evaluation
> + *
> + * This structure is the payload for the VIRTIO_NET_RESOURCE_OBJ_FF_GROUP
> + * administrative object. Devices use @group_priority to order flow filter
> + * groups. Multi-byte fields are little-endian.
> + */
> +struct virtio_net_resource_obj_ff_group {
> +	__le16 group_priority;
> +};
> +
>  #endif
> -- 
> 2.50.1