How to save the machine state of a QEMU VM started using qemu-system-x86_64?

I have a VM running using: qemu-system-x86_64 -m 8192 -smp 3 \ -net user -net nic,model=virtio -boot menu=on \ -drive file=guixsd-usb-install-0.13.0.x86_64-linux \ -drive file=guixsd.img per the [GuixSD VM installation guide](https://www.gnu.org/software/guix/manual/html_node/Installing-GuixSD-in-a-VM.html) (with some slight modifications like the RAM usage, file names and CPU cores allocated). I would like to save the machine state so that I can restore it later (exactly as it was before I saved it, right in the middle of running the guix system init ... command. Sort of the equivalent to the "Save the machine state" option for VirtualBox VMs. I saw this answer https://unix.stackexchange.com/a/361015/27613 but it requires the name of the VM, running virsh list --all doesn't list the name of VMs started via this command. DuckDuckGo searching for answers hasn't revealed anything as most results related to if I had started the VM from virt-manager.