Hot extend libvirt qcow2 disk

gistfile1.txt

https://serverfault.com/a/743106/536603

virsh qemu-monitor-command ${vm_name?} block_resize  drive-${alias?}  200G --hmp

alias: something like 'virtio-disk0'. It comes from:
<disk type="file" device="disk">
  <driver name="qemu" type="qcow2" />
  <source file="/data/test.img" />
  <backingStore />
  <target dev="vda" bus="virtio" />
  <alias name="virtio-disk0" />
  <address type="pci" domain="0x0000" bus="0x00" slot="0x04" function="0x0" />
</disk>