[libvirt-users] Which functions call qemu_driver API?

Hi, Excuse me, I have watched qemu_driver.c where most of the libvirt API is overrided in order to connect qemu. But I am confused which functions then call those qemu_driver API? I mean where is the qemu_driver implementation? Libvirt.c? But how does the qemu_driver connect and control qemu? Thanks a lot! Regards, Corey