Moving to POST.
https://post-office.corp.redhat.com/archives/rhvirt-patches/2017-September/msg00758.html

Fix included in qemu-kvm-rhev-2.9.0-16.el7_4.9

Bug is verified pass for qemu-kvm-rhev-2.9.0-16.el7_4.9

Steps for verification:
1. boot guest on src
#!/bin/bash
/usr/libexec/qemu-kvm \
-name guest=test-virt \
-machine pc,usb=off,vmport=off,dump-guest-core=off \
-cpu SandyBridge \
-m 2G \
-smp 4,sockets=4,cores=1,threads=1 \
-boot strict=on \
-drive file=/home/test/nbd01/test.qcow2,if=none,cache=none,snapshot=off,format=qcow2,id=img0 \
-device virtio-blk-pci,bus=pci.0,addr=0x7,drive=img0,id=virtio-disk0,bootindex=1 \
-netdev tap,id=hostnet0,vhost=on \
-device virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:12:b3:20:61,bus=pci.0,addr=0x3 \
-device VGA \
-usbdevice tablet \
-vnc :1 \
-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x8 \
-monitor stdio \
-qmp tcp:0:4444,server,nowait

2. create dest mirror image 
# qemu-img create -f qcow2 mirror1.qcow2 20G

3. start dest guest and setup as NBD server
#!/bin/bash
/usr/libexec/qemu-kvm \
-name guest=test-virt \
-machine pc,accel=kvm,usb=off,vmport=off,dump-guest-core=off \
-cpu SandyBridge \
-m 2G \
-smp 4,sockets=4,cores=1,threads=1 \
-boot strict=on \
-drive file=/home/test/nbd01/mirror1.qcow2,if=none,cache=none,snapshot=off,format=qcow2,id=img0 \
-device virtio-blk-pci,bus=pci.0,addr=0x7,drive=img0,id=virtio-disk0,bootindex=1 \
-netdev tap,id=hostnet0,vhost=on \
-device virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:12:b3:20:61,bus=pci.0,addr=0x3 \
-device VGA \
-usbdevice tablet \
-vnc :3 \
-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x8 \
-monitor stdio \
-qmp tcp:0:5555,server,nowait \
-incoming tcp:0:6666 

{ "execute": "qmp_capabilities" }
{ "execute": "nbd-server-start", "arguments": { "addr": { "type": "inet", "data": { "host": "127.0.0.1", "port": "9999" } } } }
{ "execute": "nbd-server-add", "arguments": { "device": "img0", "writable": true } }

4. invoke drive-mirror on src to dest
{ "execute": "qmp_capabilities" }
{ "execute": "drive-mirror", "arguments": { "device": "img0", "target": "nbd://127.0.0.1:9999/img0", "sync": "full", "format": "raw", "mode": "existing" } }

5. reopen src to mirror when block mirror is ready
{"execute": "block-job-complete", "arguments": { "device": "img0"} }

6. invoke migration on src
(qemu) migrate -d tcp:0:6666

7. invoke nbd-server-stop when migration completes, and cont to start guest on dest
{ "execute" : "nbd-server-stop", "arguments" : {} }
(qemu) cont

After, the guest could run on dest. Both src and dest qemu could quit normally.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHSA-2017:3369