how to change nic's tx/rx ring size inside vm

["longguang.yue" <libvirt@xxxxxxx>]

Hi, all:

my environment is qemu-kvm-6.0.0, 4.18.0-240, libvirt 7.4.0.  vm is configured like this   queues='4' rx_queue_size='1024' tx_queue_size='1024'.
inside vm  i can not change nic's ring size. 
changing tx leads to error  'Cannot set device ring parameters: Operation not supported'.  
changing rx leads to error 'rx unmodified, ignoring. no ring parameters changed, aborting'

how to make it work and confirm what current value is?

thanks