Re: [PATCH 1/2] vDPA: allow userspace to query features of a vDPA device

[Si-Wei Liu <si-wei.liu@xxxxxxxxxx>]

On 8/15/2022 2:26 AM, Zhu Lingshan wrote:
> This commit adds a new vDPA netlink attribution
> VDPA_ATTR_VDPA_DEV_SUPPORTED_FEATURES. Userspace can query
> features of vDPA devices through this new attr.
>
> Signed-off-by: Zhu Lingshan <lingshan.zhu@xxxxxxxxx>
> ---
>   drivers/vdpa/vdpa.c       | 17 +++++++++++++----
>   include/uapi/linux/vdpa.h |  3 +++
>   2 files changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
> index c06c02704461..efb55a06e961 100644
> --- a/drivers/vdpa/vdpa.c
> +++ b/drivers/vdpa/vdpa.c
> @@ -491,6 +491,8 @@ static int vdpa_mgmtdev_fill(const struct vdpa_mgmt_dev *mdev, struct sk_buff *m
>   		err = -EMSGSIZE;
>   		goto msg_err;
>   	}
> +
> +	/* report features of a vDPA management device through VDPA_ATTR_DEV_SUPPORTED_FEATURES */
>   	if (nla_put_u64_64bit(msg, VDPA_ATTR_DEV_SUPPORTED_FEATURES,
>   			      mdev->supported_features, VDPA_ATTR_PAD)) {
>   		err = -EMSGSIZE;
> @@ -815,7 +817,7 @@ static int vdpa_dev_net_mq_config_fill(struct vdpa_device *vdev,
>   static int vdpa_dev_net_config_fill(struct vdpa_device *vdev, struct sk_buff *msg)
>   {
>   	struct virtio_net_config config = {};
> -	u64 features;
> +	u64 features_device, features_driver;
>   	u16 val_u16;
>   
>   	vdpa_get_config_unlocked(vdev, 0, &config, sizeof(config));
> @@ -832,12 +834,19 @@ static int vdpa_dev_net_config_fill(struct vdpa_device *vdev, struct sk_buff *ms
>   	if (nla_put_u16(msg, VDPA_ATTR_DEV_NET_CFG_MTU, val_u16))
>   		return -EMSGSIZE;
>   
> -	features = vdev->config->get_driver_features(vdev);
> -	if (nla_put_u64_64bit(msg, VDPA_ATTR_DEV_NEGOTIATED_FEATURES, features,
> +	features_driver = vdev->config->get_driver_features(vdev);
> +	if (nla_put_u64_64bit(msg, VDPA_ATTR_DEV_NEGOTIATED_FEATURES, features_driver,
> +			      VDPA_ATTR_PAD))
> +		return -EMSGSIZE;
> +
> +	features_device = vdev->config->get_device_features(vdev);
> +
> +	/* report features of a vDPA device through VDPA_ATTR_VDPA_DEV_SUPPORTED_FEATURES */
> +	if (nla_put_u64_64bit(msg, VDPA_ATTR_VDPA_DEV_SUPPORTED_FEATURES, features_device,
>   			      VDPA_ATTR_PAD))
>   		return -EMSGSIZE;
>   
> -	return vdpa_dev_net_mq_config_fill(vdev, msg, features, &config);
> +	return vdpa_dev_net_mq_config_fill(vdev, msg, features_driver, &config);
>   }
>   
>   static int
> diff --git a/include/uapi/linux/vdpa.h b/include/uapi/linux/vdpa.h
> index 25c55cab3d7c..d171b92ef522 100644
> --- a/include/uapi/linux/vdpa.h
> +++ b/include/uapi/linux/vdpa.h
> @@ -46,7 +46,10 @@ enum vdpa_attr {
>   
>   	VDPA_ATTR_DEV_NEGOTIATED_FEATURES,	/* u64 */
>   	VDPA_ATTR_DEV_MGMTDEV_MAX_VQS,		/* u32 */
> +	/* features of a vDPA management device */
>   	VDPA_ATTR_DEV_SUPPORTED_FEATURES,	/* u64 */
> +	/* features of a vDPA device, e.g., /dev/vhost-vdpa0 */
> +	VDPA_ATTR_VDPA_DEV_SUPPORTED_FEATURES,	/* u64 */
Append to the end, please. Otherwise it breaks userspace ABI.

-Siwei

>   
>   	VDPA_ATTR_DEV_QUEUE_INDEX,              /* u32 */
>   	VDPA_ATTR_DEV_VENDOR_ATTR_NAME,		/* string */

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