virtscsi_config_get
num_queues = virtscsi_config_get(vdev, num_queues) ? : 1;
num_targets = virtscsi_config_get(vdev, max_target) + 1;
sg_elems = virtscsi_config_get(vdev, seg_max) ?: 1;
cmd_per_lun = virtscsi_config_get(vdev, cmd_per_lun) ?: 1;
shost->max_sectors = virtscsi_config_get(vdev, max_sectors) ?: 0xFFFF;
shost->max_lun = virtscsi_config_get(vdev, max_lun) + 1 + 0x4000;