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

[Kashyap Chamarthy]

[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+tcp.txt

(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