1. prepare a vm and do post-copy + NBD migration

# virsh migrate vm1 qemu+tcp://XXX/system --live --p2p --tls --postcopy --postcopy-after-precopy --copy-storage-all --migrate-disks vda --verbose 

2. cancel migration by Ctrl + C at the end of postcopy
# virsh migrate vm1 qemu+tcp://XXX/system --live --p2p --tls --postcopy --postcopy-after-precopy --copy-storage-all --migrate-disks vda --verbose 
Migration: [100.00 %]^C
Migration: [100.00 %]

Migration: [100.00 %]^C

3. migration cannot be finished and from gdb you can see that is block in the virtqemud not in the virsh command:

Thread 2 (Thread 0x7f2907bff640 (LWP 77856) "rpc-virtqemud"):
#0  0x00007f291668679a in __futex_abstimed_wait_common () from /lib64/libc.so.6
#1  0x00007f2916688fa0 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libc.so.6
#2  0x00007f2916d4b8fb in virCondWait (c=<optimized out>, m=<optimized out>) at ../src/util/virthread.c:171
#3  0x00007f2916d76c1b in virDomainObjWait (vm=0x7f28c0093840) at ../src/conf/domain_conf.c:4244
#4  0x00007f28ee4be481 in qemuDomainObjWait (vm=<optimized out>) at ../src/qemu/qemu_domain.c:12389
#5  0x00007f28ee5169b7 in qemuMigrationSrcRun (driver=driver@entry=0x7f28c00225a0, vm=vm@entry=0x7f28c0093840, xmlin=xmlin@entry=0x0, persist_xml=persist_xml@entry=0x0, cookiein=cookiein@entry=0x7f290003cb20 "<qemu-migration>\n  <name>vm1</name>\n  <uuid>2e2f2556-5500-47d3-87c6-278d00793c3c</uuid>\n  <hostname>TARGET_HOST</hostname>\n  <hostuuid>4c4c4544-0032-5010-8036-c2c04f344733</"..., cookieinlen=cookieinlen@entry=888, cookieout=0x7f2907bfe4b0, cookieoutlen=0x7f2907bfe48c, flags=98371, resource=0, spec=0x7f2907bfe2e0, dconn=0x7f28f800b610, graphicsuri=0x0, nmigrate_disks=1, migrate_disks=0x7f29000377c0, migParams=0x7f2900038e20, nbdURI=0x0) at ../src/qemu/qemu_migration.c:4987
#6  0x00007f28ee517eb7 in qemuMigrationSrcPerformNative (driver=driver@entry=0x7f28c00225a0, vm=vm@entry=0x7f28c0093840, xmlin=xmlin@entry=0x0, persist_xml=persist_xml@entry=0x0, uri=uri@entry=0x7f2900055af0 "tcp:TARGET_HOST:49152", cookiein=cookiein@entry=0x7f290003cb20 "<qemu-migration>\n  <name>vm1</name>\n  <uuid>2e2f2556-5500-47d3-87c6-278d00793c3c</uuid>\n  <hostname>TARGET_HOST</hostname>\n  <hostuuid>4c4c4544-0032-5010-8036-c2c04f344733</"..., cookieinlen=888, cookieout=0x7f2907bfe4b0, cookieoutlen=0x7f2907bfe48c, flags=98371, resource=0, dconn=0x7f28f800b610, graphicsuri=0x0, nmigrate_disks=1, migrate_disks=0x7f29000377c0, migParams=0x7f2900038e20, nbdURI=0x0) at ../src/qemu/qemu_migration.c:5247
#7  0x00007f28ee519fca in qemuMigrationSrcPerformPeer2Peer3 (flags=<optimized out>, useParams=<optimized out>, bandwidth=<optimized out>, migParams=<optimized--Type <RET> for more, q to quit, c to continue without paging--
 out>, nbdURI=<optimized out>, nbdPort=<optimized out>, migrate_disks=<optimized out>, nmigrate_disks=<optimized out>, listenAddress=<optimized out>, graphicsuri=<optimized out>, uri=<optimized out>, dname=<optimized out>, persist_xml=<optimized out>, xmlin=<optimized out>, vm=<optimized out>, dconnuri=<optimized out>, dconn=0x7f28f800b610, sconn=<optimized out>, driver=0x7f28c00225a0) at ../src/qemu/qemu_migration.c:5721
#8  qemuMigrationSrcPerformPeer2Peer (v3proto=<synthetic pointer>, resource=<optimized out>, dname=<optimized out>, flags=<optimized out>, migParams=<optimized out>, nbdURI=<optimized out>, nbdPort=<optimized out>, migrate_disks=<optimized out>, nmigrate_disks=<optimized out>, listenAddress=<optimized out>, graphicsuri=<optimized out>, uri=<optimized out>, dconnuri=<optimized out>, persist_xml=<optimized out>, xmlin=<optimized out>, vm=<optimized out>, sconn=<optimized out>, driver=0x7f28c00225a0) at ../src/qemu/qemu_migration.c:6022
#9  qemuMigrationSrcPerformJob (driver=driver@entry=0x7f28c00225a0, conn=conn@entry=0x7f28f800b510, vm=vm@entry=0x7f28c0093840, xmlin=xmlin@entry=0x0, persist_xml=persist_xml@entry=0x0, dconnuri=<optimized out>, uri=<optimized out>, graphicsuri=<optimized out>, listenAddress=<optimized out>, nmigrate_disks=<optimized out>, migrate_disks=<optimized out>, nbdPort=<optimized out>, nbdURI=<optimized out>, migParams=<optimized out>, cookiein=<optimized out>, cookieinlen=<optimized out>, cookieout=<optimized out>, cookieoutlen=<optimized out>, flags=<optimized out>, dname=<optimized out>, resource=<optimized out>, v3proto=<optimized out>) at ../src/qemu/qemu_migration.c:6111
#10 0x00007f28ee51a5ab in qemuMigrationSrcPerform (driver=0x7f28c00225a0, conn=0x7f28f800b510, vm=0x7f28c0093840, xmlin=0x0, persist_xml=0x0, dconnuri=0x7f2900005f80 "qemu+tcp://TARGET_HOST/system", uri=0x0, graphicsuri=0x0, listenAddress=0x0, nmigrate_disks=1, migrate_disks=0x7f29000377c0, nbdPort=0, nbdURI=0x0, migParams=0x7f2900038e20, cookiein=0x0, cookieinlen=0, cookieout=0x7f2907bfe8b8, cookieoutlen=0x7f2907bfe8ac, flags=98371, dname=0x0, resource=0, v3proto=true) at ../src/qemu/qemu_migration.c:6336
#11 0x00007f28ee4e0dd2 in qemuDomainMigratePerform3Params (dom=0x7f29000036e0, dconnuri=0x7f2900005f80 "qemu+tcp://TARGET_HOST/system", params=0x7f29000388c0, nparams=1, cookiein=0x0, cookieinlen=0, cookieout=0x7f2907bfe8b8, cookieoutlen=0x7f2907bfe8ac, flags=98371) at ../src/qemu/qemu_driver.c:11287
#12 0x00007f2916f1ff39 in virDomainMigratePerform3Params (domain=domain@entry=0x7f29000036e0, dconnuri=0x7f2900005f80 "qemu+tcp://TARGET_HOST/system", params=<optimized out>, nparams=1, cookiein=0x0, cookieinlen=0, cookieout=0x7f2907bfe8b8, cookieoutlen=0x7f2907bfe8ac, flags=98371) at ../src/libvirt-domain.c:5433
#13 0x0000564f0b935a37 in remoteDispatchDomainMigratePerform3Params (server=<optimized out>, msg=0x564f0d8dd080, ret=0x7f2900005fd0, args=0x7f290000ae60, rerr=0x7f2907bfe9a0, client=<optimized out>) at ../src/remote/remote_daemon_dispatch.c:5754
#14 remoteDispatchDomainMigratePerform3ParamsHelper (server=<optimized out>, client=<optimized out>, msg=0x564f0d8dd080, rerr=0x7f2907bfe9a0, args=0x7f290000ae60, ret=0x7f2900005fd0) at src/remote/remote_daemon_dispatch_stubs.h:8943
#15 0x00007f2916e1444c in virNetServerProgramDispatchCall (msg=0x564f0d8dd080, client=0x564f0d8dc560, server=0x564f0d8cd080, prog=0x564f0d8cf810) at ../src/rpc/virnetserverprogram.c:423
#16 virNetServerProgramDispatch (prog=0x564f0d8cf810, server=server@entry=0x564f0d8cd080, client=0x564f0d8dc560, msg=0x564f0d8dd080) at ../src/rpc/virnetserverprogram.c:299
#17 0x00007f2916e14758 in virNetServerProcessMsg (msg=<optimized out>, prog=<optimized out>, client=<optimized out>, srv=0x564f0d8cd080) at ../src/rpc/virnetserver.c:135
#18 virNetServerHandleJob (jobOpaque=0x564f0d8c8890, opaque=0x564f0d8cd080) at ../src/rpc/virnetserver.c:155
#19 0x00007f2916d50ef3 in virThreadPoolWorker (opaque=<optimized out>) at ../src/util/virthreadpool.c:164
#20 0x00007f2916d50149 in virThreadHelper (data=<optimized out>) at ../src/util/virthread.c:256
#21 0x00007f2916689c02 in start_thread () from /lib64/libc.so.6
--Type <RET> for more, q to quit, c to continue without paging--
#22 0x00007f291670ec40 in clone3 () from /lib64/libc.so.6