Re: [PATCH v3 2/6] vdpa: conditionally read STATUS in config space

[Eli Cohen <elic@nvidia.com>]

On 03/02/2023 7:01, Si-Wei Liu wrote:
> The spec says:
>      status only exists if VIRTIO_NET_F_STATUS is set
>
> Similar to MAC and MTU, vdpa_dev_net_config_fill() should read
> STATUS conditionally depending on the feature bits.
>
> Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
> Reviewed-by: Parav Pandit <parav@nvidia.com>
> ---
>   drivers/vdpa/vdpa.c | 20 +++++++++++++++-----
>   1 file changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
> index 3a82ca78..21c8aa3 100644
> --- a/drivers/vdpa/vdpa.c
> +++ b/drivers/vdpa/vdpa.c
> @@ -843,18 +843,25 @@ static int vdpa_dev_net_mac_config_fill(struct sk_buff *msg, u64 features,
>   			sizeof(config->mac), config->mac);
>   }
>   
> +static int vdpa_dev_net_status_config_fill(struct sk_buff *msg, u64 features,
> +					   const struct virtio_net_config *config)
> +{
> +	u16 val_u16;
> +
> +	if ((features & BIT_ULL(VIRTIO_NET_F_STATUS)) == 0)
> +		return 0;
Instead of returning 0 here, it would be better to explicitly put 0 in 
the message field for

VDPA_ATTR_DEV_NET_STATUS

> +
> +	val_u16 = __virtio16_to_cpu(true, config->status);
> +	return nla_put_u16(msg, VDPA_ATTR_DEV_NET_STATUS, val_u16);
> +}
> +
>   static int vdpa_dev_net_config_fill(struct vdpa_device *vdev, struct sk_buff *msg)
>   {
>   	struct virtio_net_config config = {};
>   	u64 features_device;
> -	u16 val_u16;
>   
>   	vdev->config->get_config(vdev, 0, &config, sizeof(config));
>   
> -	val_u16 = __virtio16_to_cpu(true, config.status);
> -	if (nla_put_u16(msg, VDPA_ATTR_DEV_NET_STATUS, val_u16))
> -		return -EMSGSIZE;
> -
>   	features_device = vdev->config->get_device_features(vdev);
>   
>   	if (nla_put_u64_64bit(msg, VDPA_ATTR_DEV_FEATURES, features_device,
> @@ -867,6 +874,9 @@ static int vdpa_dev_net_config_fill(struct vdpa_device *vdev, struct sk_buff *ms
>   	if (vdpa_dev_net_mac_config_fill(msg, features_device, &config))
>   		return -EMSGSIZE;
>   
> +	if (vdpa_dev_net_status_config_fill(msg, features_device, &config))
> +		return -EMSGSIZE;
> +
>   	return vdpa_dev_net_mq_config_fill(msg, features_device, &config);
>   }
>