# Re: \[PATCH v2 07/10\] vdpa: Add support for returning device configuration information

- From: Si-Wei Liu \<hidden\>
- Date: 2021-12-13 23:49:33 
- List: virtualization
- Page: https://ratatoskr.run/virtualization/2021/12/15818550
- Thread: https://ratatoskr.run/virtualization/2021/12/15818550/t.md

```text


On 12/13/2021 6:42 AM, Eli Cohen wrote:
> Add netlink attribute to store flags indicating current state of the
> device.
> In addition, introduce a flag to indicate whether control virtqueue is
> used.
>
> This indication can be retrieved by:
>
> vdpa dev config show vdpa-a
> vdpa-a: mac 00:00:00:00:88:88 link up link_announce false max_vq_pairs 1
> 	mtu 1500 ctrl_vq yes
>
> Signed-off-by: Eli Cohen <redacted>
>
> ----
> V1 -> V2
> Patch was changed to return only an indication of ctrl VQ
> ---
>   drivers/vdpa/vdpa.c       | 17 +++++++++++++++++
>   include/uapi/linux/vdpa.h |  8 ++++++++
>   2 files changed, 25 insertions(+)
>
> diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
> index 7b7bef7673b4..130a8d4aeaed 100644
> --- a/drivers/vdpa/vdpa.c
> +++ b/drivers/vdpa/vdpa.c
> @@ -787,6 +787,19 @@ static int vdpa_nl_cmd_dev_get_dumpit(struct sk_buff *msg, struct netlink_callba
>   	return msg->len;
>   }
>   
> +static int vdpa_dev_net_ctrl_vq_fill(struct vdpa_device *vdev,
> +				     struct sk_buff *msg,
> +				     struct virtio_net_config *config,
> +				     u64 features)
> +{
> +	if (!(features & BIT_ULL(VIRTIO_NET_F_CTRL_VQ)))
> +		return 0;
> +
> +	/* currently the only flag can be returned */
> +	return nla_put_u64_64bit(msg, VDPA_ATTR_DEV_FLAGS,
> +				 BIT_ULL(VDPA_DEV_ATTR_CVQ), VDPA_ATTR_PAD);
> +}
> +
>   static int vdpa_dev_net_mq_config_fill(struct vdpa_device *vdev,
>   				       struct sk_buff *msg, u64 features,
>   				       const struct virtio_net_config *config)
> @@ -805,6 +818,7 @@ static int vdpa_dev_net_config_fill(struct vdpa_device *vdev, struct sk_buff *ms
>   	struct virtio_net_config config = {};
>   	u64 features;
>   	u16 val_u16;
> +	int err;
>   
>   	vdpa_get_config(vdev, 0, &config, sizeof(config));
>   
> @@ -821,6 +835,9 @@ static int vdpa_dev_net_config_fill(struct vdpa_device *vdev, struct sk_buff *ms
>   		return -EMSGSIZE;
>   
>   	features = vdev->config->get_driver_features(vdev);
> +	err = vdpa_dev_net_ctrl_vq_fill(vdev, msg, &config, features);
> +	if (err)
> +		return err;
>   
>   	return vdpa_dev_net_mq_config_fill(vdev, msg, features, &config);
>   }
> diff --git a/include/uapi/linux/vdpa.h b/include/uapi/linux/vdpa.h
> index a252f06f9dfd..23b854e3e5e2 100644
> --- a/include/uapi/linux/vdpa.h
> +++ b/include/uapi/linux/vdpa.h
> @@ -20,9 +20,16 @@ enum vdpa_command {
>   	VDPA_CMD_DEV_CONFIG_GET,	/* can dump */
>   };
>   
> +enum {
> +	VDPA_DEV_ATTR_CVQ,
> +};
> +
>   enum vdpa_attr {
>   	VDPA_ATTR_UNSPEC,
>   
> +	/* Pad attribute for 64b alignment */
> +	VDPA_ATTR_PAD = VDPA_ATTR_UNSPEC,
> +
>   	/* bus name (optional) + dev name together make the parent device handle */
>   	VDPA_ATTR_MGMTDEV_BUS_NAME,		/* string */
>   	VDPA_ATTR_MGMTDEV_DEV_NAME,		/* string */
> @@ -34,6 +41,7 @@ enum vdpa_attr {
>   	VDPA_ATTR_DEV_MAX_VQS,			/* u32 */
>   	VDPA_ATTR_DEV_MAX_VQ_SIZE,		/* u16 */
>   	VDPA_ATTR_DEV_MIN_VQ_SIZE,		/* u16 */
> +	VDPA_ATTR_DEV_FLAGS,			/* u64 */
Adding new attr here would break existing userspace that is compiled with the older value. Need to append to the end.

-Siwei
>   
>   	VDPA_ATTR_DEV_NET_CFG_MACADDR,		/* binary */
>   	VDPA_ATTR_DEV_NET_STATUS,		/* u8 */

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```