I have two stretch machines and --live migration with active --copy-storage-all won't work. I don't know if this refers to this (old) but not closed bug. There's nothing segfaulting when I try to migrate, but the migration won't start and got stuck on both machines. When starting a live migration, f.i. this way
virsh migrate --live --desturi qemu+tls://host2/system --copy-storage-all --verbose --persistent --undefinesource test2 the command doesn't come back. On the host2, the machine got created in "pause" mode. This process never ends and can only be canceld by restarting libvirtd on host2.