how to use exec:cat > /dev/null using libvirt

Hello community, I am trying to inspect a migration failure using the steps described here ( https://wiki.qemu.org/Features/Migration/Troubleshooting#:~:text=on%20gra....). In the fourth step, it suggests using migrate 'exec:cat > /dev/null' to try dumping vm state on the source node. Since the virtual machine is controlled by libvirt, I suppose I could using the following command, virsh qemu-monitor-command --hmp <instance-id> 'migrate "exec:cat > /dev/nulll" but it failed with 2023-02-24T02:56:07.347307Z qemu-system-x86_64: Unable to write to command: Broken pipe So my question is how to use this command using libvirt? Thank you very much for the help. -- Best Regards, Jiatong Shen