I often have to restart my array for various reasons and since my family uses unRAID VMs as their go-to personal computers, this is a big hassle to close all work and shutdown. I've tried hibernation, either within the OS or using "virsh domsuspend" to disk. It appears to work, but the VMs show as "paused" not "stopped". I can resume them fine, but if I stop the array, the VMs crash and the hibernation state isn't preserved (one time, I've also encountered the qemu preventing array stop because of access to drives, in which case I had to kill the instance).
I've also tested this on a brand new Win10 VM install with qemu-agent running and virtio drivers installed.
[edit] Btw I can't use "virsh save" unfortunately because of GPU pass through.