[libvirt] [libvirt-3.2] NBD-based storage migration fails with "error: invalid argument: monitor must not be NULL"

[Filed this bug -- https://bugzilla.redhat.com/show_bug.cgi?id=1439841] Easy reproducer: $ virsh migrate --verbose --copy-storage-all \ --p2p --live l2-f25 qemu+ssh://root@devstack-a/system error: invalid argument: monitor must not be NULL - - - This is a nested Fedora-25 environment. So, I'm trying to migrate a level-2 Fedora-25 guest. libvirt version: $ rpm -q libvirt-daemon-kvm libvirt-daemon-kvm-3.2.0-1.fc25.x86_64 The QEMU binary used to boot the nested guest (to be migrated) on source guest hypervisor (host from which migration originates) _and_ on the destination guest hypervisor is built from Git, with this specific patch from QEMU https://lists.nongnu.org/archive/html/qemu-block/2017-04/msg00085.html -- [RFC PATCH for-2.9] block: Ignore guest dev permissions during incoming migration So the built binary version (showing `git describe` output): $ /home/stack/build/build-qemu/x86_64-softmmu/qemu-system-x86_64 --version QEMU emulator version 2.8.93 (v2.9.0-rc3-3-g3a8624b) NB: However, the QEMU version is irrelevant, Michal Privoznik confirms on IRC that this is a clear libvirt bug. Steps to reproduce ------------------ (1) Setup two hosts: https://kashyapc.fedorapeople.org/virt/libvirt-migration-tests-with-qemu+... (2) Then, migrate the guest to the destination host: $ virsh migrate --verbose --copy-storage-all \ --p2p --live l2-f25 qemu+ssh://root@devstack-a/system Actual results -------------- $ virsh migrate --verbose --copy-storage-all \ --p2p --live l2-f25 qemu+ssh://root@devstack-a/system error: invalid argument: monitor must not be NULL -- /kashyap