While working on the tripleo integration on this. Some results with the patch from thttps://review.openstack.org/625216 :

SRC compute:

2019-01-09 07:50:58.430+0000: 238166: info : qemuMonitorIOWrite:551 : QEMU_MONITOR_IO_WRITE: mon=0x7fa21001bc80 buf={"execute":"blockdev-add","arguments":{"driver":"nbd","server":{"type":"inet","host":"overcloud-novacompute-1.internalapi.ooo.test","port":"61153"},"export":"drive-vi
rtio-disk0","tls-creds":"objlibvirt_migrate_tls0","node-name":"migration-vda-storage","read-only":false,"discard":"unmap"},"id":"libvirt-26"} len=309 ret=309 errno=0
2019-01-09 07:50:58.562+0000: 238166: debug : qemuMonitorJSONIOProcessLine:197 : Line [{"return": {}, "id": "libvirt-26"}]
2019-01-09 07:50:58.562+0000: 238166: info : qemuMonitorJSONIOProcessLine:217 : QEMU_MONITOR_RECV_REPLY: mon=0x7fa21001bc80 reply={"return": {}, "id": "libvirt-26"}
2019-01-09 07:50:58.569+0000: 238183: debug : qemuMonitorJSONCommandWithFd:310 : Receive command reply ret=0 rxObject=0x560388a64150
2019-01-09 07:50:58.569+0000: 238183: debug : qemuMonitorBlockdevAdd:4336 : props=0x7fa2080138b0 (node-name=migration-vda-format)
2019-01-09 07:50:58.569+0000: 238183: debug : qemuMonitorBlockdevAdd:4338 : mon:0x7fa21001bc80 vm:0x7fa204003440 json:1 fd:29
2019-01-09 07:50:58.569+0000: 238183: debug : qemuMonitorJSONCommandWithFd:305 : Send command '{"execute":"blockdev-add","arguments":{"node-name":"migration-vda-format","read-only":false,"driver":"raw","file":"migration-vda-storage"},"id":"libvirt-27"}' for write with FD -1
2019-01-09 07:50:58.569+0000: 238183: info : qemuMonitorSend:1083 : QEMU_MONITOR_SEND_MSG: mon=0x7fa21001bc80 msg={"execute":"blockdev-add","arguments":{"node-name":"migration-vda-format","read-only":false,"driver":"raw","file":"migration-vda-storage"},"id":"libvirt-27"} fd=-1
2019-01-09 07:50:58.569+0000: 238166: info : qemuMonitorIOWrite:551 : QEMU_MONITOR_IO_WRITE: mon=0x7fa21001bc80 buf={"execute":"blockdev-add","arguments":{"node-name":"migration-vda-format","read-only":false,"driver":"raw","file":"migration-vda-storage"},"id":"libvirt-27"} len=159 ret=159 errno=0

2019-01-09 07:50:58.576+0000: 238183: debug : qemuMonitorJSONCommandWithFd:305 : Send command '{"execute":"blockdev-mirror","arguments":{"device":"drive-virtio-disk0","target":"migration-vda-format","speed":9223372036853727232,"sync":"top"},"id":"libvirt-28"}' for write with FD -1
2019-01-09 07:50:58.576+0000: 238183: info : qemuMonitorSend:1083 : QEMU_MONITOR_SEND_MSG: mon=0x7fa21001bc80 msg={"execute":"blockdev-mirror","arguments":{"device":"drive-virtio-disk0","target":"migration-vda-format","speed":9223372036853727232,"sync":"top"},"id":"libvirt-28"} fd=-1
2019-01-09 07:50:58.576+0000: 238166: info : qemuMonitorIOWrite:551 : QEMU_MONITOR_IO_WRITE: mon=0x7fa21001bc80 buf={"execute":"blockdev-mirror","arguments":{"device":"drive-virtio-disk0","target":"migration-vda-format","speed":9223372036853727232,"sync":"top"},"id":"libvirt-28"} len=166 ret=166 errno=0
2019-01-09 07:50:58.580+0000: 238166: debug : qemuMonitorJSONIOProcessLine:197 : Line [{"timestamp": {"seconds": 1547020258, "microseconds": 579521}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "drive-virtio-disk0"}}]
2019-01-09 07:50:58.582+0000: 238183: debug : qemuMonitorJSONCommandWithFd:305 : Send command '{"execute":"blockdev-add","arguments":{"driver":"nbd","server":{"type":"inet","host":"overcloud-novacompute-1.internalapi.ooo.test","port":"61153"},"export":"drive-virtio-disk1","tls-cred
s":"objlibvirt_migrate_tls0","node-name":"migration-vdb-storage","read-only":false,"discard":"unmap"},"id":"libvirt-29"}' for write with FD -1
2019-01-09 07:50:58.582+0000: 238183: info : qemuMonitorSend:1083 : QEMU_MONITOR_SEND_MSG: mon=0x7fa21001bc80 msg={"execute":"blockdev-add","arguments":{"driver":"nbd","server":{"type":"inet","host":"overcloud-novacompute-1.internalapi.ooo.test","port":"61153"},"export":"drive-virt
io-disk1","tls-creds":"objlibvirt_migrate_tls0","node-name":"migration-vdb-storage","read-only":false,"discard":"unmap"},"id":"libvirt-29"} fd=-1
2019-01-09 07:50:58.582+0000: 238166: info : qemuMonitorIOWrite:551 : QEMU_MONITOR_IO_WRITE: mon=0x7fa21001bc80 buf={"execute":"blockdev-add","arguments":{"driver":"nbd","server":{"type":"inet","host":"overcloud-novacompute-1.internalapi.ooo.test","port":"61153"},"export":"drive-virtio-disk1","tls-creds":"objlibvirt_migrate_tls0","node-name":"migration-vdb-storage","read-only":false,"discard":"unmap"},"id":"libvirt-29"} len=309 ret=309 errno=0
2019-01-09 07:50:58.717+0000: 238183: debug : qemuMonitorJSONCommandWithFd:305 : Send command '{"execute":"blockdev-add","arguments":{"node-name":"migration-vdb-format","read-only":false,"driver":"raw","file":"migration-vdb-storage"},"id":"libvirt-30"}' for write with FD -1
2019-01-09 07:50:58.717+0000: 238183: info : qemuMonitorSend:1083 : QEMU_MONITOR_SEND_MSG: mon=0x7fa21001bc80 msg={"execute":"blockdev-add","arguments":{"node-name":"migration-vdb-format","read-only":false,"driver":"raw","file":"migration-vdb-storage"},"id":"libvirt-30"} fd=-1
2019-01-09 07:50:58.717+0000: 238166: info : qemuMonitorIOWrite:551 : QEMU_MONITOR_IO_WRITE: mon=0x7fa21001bc80 buf={"execute":"blockdev-add","arguments":{"node-name":"migration-vdb-format","read-only":false,"driver":"raw","file":"migration-vdb-storage"},"id":"libvirt-30"} len=159 ret=159 errno=0
2019-01-09 07:50:58.720+0000: 238183: debug : qemuMonitorJSONCommandWithFd:305 : Send command '{"execute":"blockdev-mirror","arguments":{"device":"drive-virtio-disk1","target":"migration-vdb-format","speed":9223372036853727232,"sync":"top"},"id":"libvirt-31"}' for write with FD -1
2019-01-09 07:50:58.720+0000: 238183: info : qemuMonitorSend:1083 : QEMU_MONITOR_SEND_MSG: mon=0x7fa21001bc80 msg={"execute":"blockdev-mirror","arguments":{"device":"drive-virtio-disk1","target":"migration-vdb-format","speed":9223372036853727232,"sync":"top"},"id":"libvirt-31"} fd=-1
2019-01-09 07:50:58.720+0000: 238166: info : qemuMonitorIOWrite:551 : QEMU_MONITOR_IO_WRITE: mon=0x7fa21001bc80 buf={"execute":"blockdev-mirror","arguments":{"device":"drive-virtio-disk1","target":"migration-vdb-format","speed":9223372036853727232,"sync":"top"},"id":"libvirt-31"} len=166 ret=166 errno=0

2019-01-09 07:50:58.723+0000: 238166: info : qemuMonitorJSONIOProcessLine:212 : QEMU_MONITOR_RECV_EVENT: mon=0x7fa21001bc80 event={"timestamp": {"seconds": 1547020258, "microseconds": 721728}, "event": "BLOCK_JOB_READY", "data": {"device": "drive-virtio-disk0", "len": 917504, "offset": 917504, "speed": 9223372036853727232, "type": "mirror"}}

2019-01-09 07:50:58.731+0000: 238166: debug : qemuProcessHandleBlockJob:912 : Block job for device drive-virtio-disk1 (domain: 0x7fa204003440,instance-00000002) type 2 status 3
2019-01-09 07:50:58.731+0000: 238166: debug : qemuMonitorJSONIOProcessLine:197 : Line [{"return": [{"auto-finalize": true, "io-status": "ok", "device": "drive-virtio-disk1", "auto-dismiss": true, "busy": false, "len": 0, "offset": 0, "status": "ready", "paused": false, "speed": 9223372036853727232, "ready": true, "type": "mirror"}, {"auto-finalize": true, "io-status": "ok", "device": "drive-virtio-disk0", "auto-dismiss": true, "busy": false, "len": 917504, "offset": 917504, "status": "ready", "paused": false, "speed": 9223372036853727232, "ready": true, "type": "mirror"}], "id": "libvirt-32"}]
2019-01-09 07:50:58.731+0000: 238166: info : qemuMonitorJSONIOProcessLine:217 : QEMU_MONITOR_RECV_REPLY: mon=0x7fa21001bc80 reply={"return": [{"auto-finalize": true, "io-status": "ok", "device": "drive-virtio-disk1", "auto-dismiss": true, "busy": false, "len": 0, "offset": 0, "status": "ready", "paused": false, "speed": 9223372036853727232, "ready": true, "type": "mirror"}, {"auto-finalize": true, "io-status": "ok", "device": "drive-virtio-disk0", "auto-dismiss": true, "busy": false, "len": 917504, "offset": 917504, "status": "ready", "paused": false, "speed": 9223372036853727232, "ready": true, "type": "mirror"}], "id": "libvirt-32"}


DST compute:

2019-01-09 07:50:58.074+0000: 237733: debug : qemuMonitorJSONCommandWithFd:305 : Send command '{"execute":"object-add","arguments":{"qom-type":"tls-creds-x509","id":"objlibvirt_migrate_tls0","props":{"dir":"/etc/pki/qemu","endpoint":"server","verify-peer":false}},"id":"libvirt-17"}' for write with FD -1
2019-01-09 07:50:58.074+0000: 237733: info : qemuMonitorSend:1083 : QEMU_MONITOR_SEND_MSG: mon=0x7f865801d4b0 msg={"execute":"object-add","arguments":{"qom-type":"tls-creds-x509","id":"objlibvirt_migrate_tls0","props":{"dir":"/etc/pki/qemu","endpoint":"server","verify-peer":false}},"id":"libvirt-17"} fd=-1
2019-01-09 07:50:58.074+0000: 237714: info : qemuMonitorIOWrite:551 : QEMU_MONITOR_IO_WRITE: mon=0x7f865801d4b0 buf={"execute":"object-add","arguments":{"qom-type":"tls-creds-x509","id":"objlibvirt_migrate_tls0","props":{"dir":"/etc/pki/qemu","endpoint":"server","verify-peer":false}},"id":"libvirt-17"} len=189 ret=189 errno=0

2019-01-09 07:50:59.197+0000: 237732: debug : qemuMonitorJSONCommandWithFd:305 : Send command '{"execute":"migrate-set-parameters","arguments":{"compress-level":1,"compress-threads":8,"decompress-threads":2,"cpu-throttle-initial":20,"cpu-throttle-increment":10,"tls-creds":"","tls-hostname":"","max-bandwidth":33554432,"downtime-limit":300,"block-incremental":false,"xbzrle-cache-size":67108864},"id":"libvirt-31"}' for write with FD -1
2019-01-09 07:50:59.197+0000: 237732: info : qemuMonitorSend:1083 : QEMU_MONITOR_SEND_MSG: mon=0x7f865801d4b0 msg={"execute":"migrate-set-parameters","arguments":{"compress-level":1,"compress-threads":8,"decompress-threads":2,"cpu-throttle-initial":20,"cpu-throttle-increment":10,"tls-creds":"","tls-hostname":"","max-bandwidth":33554432,"downtime-limit":300,"block-incremental":false,"xbzrle-cache-size":67108864},"id":"libvirt-31"} fd=-1
2019-01-09 07:50:59.197+0000: 237714: info : qemuMonitorIOWrite:551 : QEMU_MONITOR_IO_WRITE: mon=0x7f865801d4b0 buf={"execute":"migrate-set-parameters","arguments":{"compress-level":1,"compress-threads":8,"decompress-threads":2,"cpu-throttle-initial":20,"cpu-throttle-increment":10,"tls-creds":"","tls-hostname":"","max-bandwidth":33554432,"downtime-limit":300,"block-incremental":false,"xbzrle-cache-size":67108864},"id":"libvirt-31"} len=321 ret=321 errno=0

Note:
"verify-peer":false => 'default_tls_x509_verify = 1' was not set in qemu.conf.