vdpa: Support reporting max device capabilities

Add max_supported_vqs and supported_features fields to struct
vdpa_mgmt_dev. Upstream drivers need to feel these values according to
the device capabilities.

These values are reported back in a netlink message when showing management
devices.

Examples:

$ auxiliary/mlx5_core.sf.1:
  supported_classes net
  max_supported_vqs 257
  dev_features CSUM GUEST_CSUM MTU HOST_TSO4 HOST_TSO6 STATUS CTRL_VQ MQ \
               CTRL_MAC_ADDR VERSION_1 ACCESS_PLATFORM

$ vdpa -j mgmtdev show
{"mgmtdev":{"auxiliary/mlx5_core.sf.1":{"supported_classes":["net"], \
  "max_supported_vqs":257,"dev_features":["CSUM","GUEST_CSUM","MTU", \
  "HOST_TSO4","HOST_TSO6","STATUS","CTRL_VQ","MQ","CTRL_MAC_ADDR", \
  "VERSION_1","ACCESS_PLATFORM"]}}}

$ vdpa -jp mgmtdev show
{
    "mgmtdev": {
        "auxiliary/mlx5_core.sf.1": {
            "supported_classes": [ "net" ],
            "max_supported_vqs": 257,
            "dev_features": ["CSUM","GUEST_CSUM","MTU","HOST_TSO4", \
                             "HOST_TSO6","STATUS","CTRL_VQ","MQ", \
                             "CTRL_MAC_ADDR","VERSION_1","ACCESS_PLATFORM"]
        }
    }
}

Signed-off-by: Eli Cohen <elic@nvidia.com>
Link: https://lore.kernel.org/r/20220105114646.577224-11-elic@nvidia.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Si-Wei Liu<si-wei.liu@oracle.com>

drivers/vdpa/vdpa.c

@@ -514,6 +514,16 @@ static int vdpa_mgmtdev_fill(const struct vdpa_mgmt_dev *mdev, struct sk_buff *m
 		err = -EMSGSIZE;
 		goto msg_err;
 	}
+	if (nla_put_u32(msg, VDPA_ATTR_DEV_MGMTDEV_MAX_VQS,
+			mdev->max_supported_vqs)) {
+		err = -EMSGSIZE;
+		goto msg_err;
+	}
+	if (nla_put_u64_64bit(msg, VDPA_ATTR_DEV_SUPPORTED_FEATURES,
+			      mdev->supported_features, VDPA_ATTR_PAD)) {
+		err = -EMSGSIZE;
+		goto msg_err;
+	}
 
 	genlmsg_end(msg, hdr);
 	return 0;

include/linux/vdpa.h

@@ -460,6 +460,8 @@ struct vdpa_mgmt_dev {
 	const struct virtio_device_id *id_table;
 	u64 config_attr_mask;
 	struct list_head list;
+	u64 supported_features;
+	u32 max_supported_vqs;
 };
 
 int vdpa_mgmtdev_register(struct vdpa_mgmt_dev *mdev);

include/uapi/linux/vdpa.h

@@ -44,6 +44,8 @@ enum vdpa_attr {
 	VDPA_ATTR_DEV_NET_CFG_MTU,		/* u16 */
 
 	VDPA_ATTR_DEV_NEGOTIATED_FEATURES,	/* u64 */
+	VDPA_ATTR_DEV_MGMTDEV_MAX_VQS,		/* u32 */
+	VDPA_ATTR_DEV_SUPPORTED_FEATURES,	/* u64 */
 	/* new attributes must be added above here */
 	VDPA_ATTR_MAX,
 };