Handling large VIRTIO_PCI_QUEUE_NUM values on Google Cloud Platform (GCP)

Hello experts,

Have a query on the following:

1) The number of descriptor count returned by the back-end through VIRTIO_PCI_QUEUE_NUM, is that negotiable with the backend? In some platforms like Google Cloud Platform (GCP) the value returned is 4096.

2) In case it is not negotiable with the back-end and unable to allocate data buffers on the Rx side for 4096 descriptors, is there a workaround to manage with fewer buffers like 256?

Additional info:

This is a FreeBSD VM running on GCP.

Please let me know. 

Regards,

Nirmal