[Qemu-devel] ?????? ?????? someconfusion on qemu i/o pocess and the qcow2format

[??????]

I want to change the queue_size of virtio-blk ring from 128 to 1024, so I  
change here:
s->vq = virtio_add_queue(vdev, 128, virtio_blk_handle_output);
but the vm will not work. Are any thing i missed ?