Re: [Qemu-devel] [PATCH v1] virtio-net: enable configurable tx queue size

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Jun 05, 2017 at 04:57:29PM +0800, Wei Wang wrote:
> @@ -1910,6 +1958,17 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp)
>          return;
>      }
>  
> +    if (n->net_conf.tx_queue_size < VIRTIO_NET_TX_QUEUE_MIN_SIZE ||
> +        n->net_conf.tx_queue_size > VIRTQUEUE_MAX_SIZE ||
> +        (n->net_conf.tx_queue_size & (n->net_conf.tx_queue_size - 1))) {
> +        error_setg(errp, "Invalid tx_queue_size (= %" PRIu16 "), "
> +                   "must be a power of 2 between %d and %d.",
> +                   n->net_conf.tx_queue_size, VIRTIO_NET_TX_QUEUE_MIN_SIZE,
> +                   VIRTQUEUE_MAX_SIZE);
> +        virtio_cleanup(vdev);
> +        return;
> +    }
> +
>      n->max_queues = MAX(n->nic_conf.peers.queues, 1);
>      if (n->max_queues * 2 + 1 > VIRTIO_QUEUE_MAX) {
>          error_setg(errp, "Invalid number of queues (= %" PRIu32 "), "

Given that some configurations (e.g. legacy guest) ignore the value,
I'm inclined to say just force the value to be within a reasonable
limit.

-- 
MST