[libvirt] Regarding Migration Code

Greetings, I was trying to understand the flow of Migration Code in libvirt and have few doubts: 1) libvirt talks to QEMU/KVM guests via QEMU API. So overall, in order to manage QEMU/KVM guests I can either use libvirt (or tools based on libvirt like virsh) or QEMU monitor. Is it so? 2) Since libvirt is Hypervisor neutral so actual migration algorithm(precopy or postcopy) is present in the hypervisor ,i.e. in case of QEMU it should be present in QEMU code base . I was going through the code starting from libvirt-domain api and not able to follow after virDomainMigrateVersion3Full(.....) . Kindly help. 3) I want to determine the Migration Time, Downtime and other resource usage. What is the correct way to determine the same? Should I use libvirt API or directly virsh or something else? Which is fast and efficient way for the same? Thanks in advance. And sorry if that was too basic