Step 1 – Shutdown the VM
virsh shutdown hostname
Step 2 – Increase the qcow2 image
Find the qcow2 file of the VM and take a backup (just in case).
cp hostname.qcow2 hostname.qcow2.backup
qemu-img resize hostname.qcow2 +100GB
Step 3 – Start the VM
Now start the VM.
virsh start hostname
Step 4 – Extend the partition in Window
Windows has a really good partition management utility built into it. Search for “disk management”