Description of problem:
Qemu core dump when do migration with rdma and multifs both enabled


Version-Release number of selected component (if applicable):
host info: 
kernel-4.18.0-108.el8.x86_64 & qemu-img-4.0.0-4.module+el8.1.0+3356+cda7f1ee.x86_64

Mellanox cards:
# lspci
01:00.0 Network controller: Mellanox Technologies MT27500 Family [ConnectX-3]

How reproducible:
3/3


Steps to Reproduce:
1.boot guest on src host with commands:
/usr/libexec/qemu-kvm \
-enable-kvm \
-machine q35  \
-m 4096 \
-smp 4 \
-cpu Skylake-Client \
-name debug-threads=on \
-device pcie-root-port,id=pcie.0-root-port-2,slot=2,chassis=2,addr=0x2,bus=pcie.0 \
-device pcie-root-port,id=pcie.0-root-port-3,slot=3,chassis=3,addr=0x3,bus=pcie.0 \
-device pcie-root-port,id=pcie.0-root-port-4,slot=4,chassis=4,addr=0x4,bus=pcie.0 \
-device virtio-scsi-pci,id=virtio_scsi_pci0,bus=pcie.0-root-port-2,addr=0x0 \
-blockdev driver=file,cache.direct=off,cache.no-flush=on,filename=/mnt/nfs/rhel810-64-virtio-scsi-2.qcow2,node-name=my_file \
-blockdev driver=qcow2,node-name=my_disk,file=my_file \
-device scsi-hd,drive=my_disk,bus=virtio_scsi_pci0.0 \
-netdev tap,id=hostnet0,vhost=on,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown,queues=4 \
-device virtio-net-pci,netdev=hostnet0,id=net0,mac=70:5a:0f:38:cd:1c,bus=pcie.0-root-port-3,vectors=10,mq=on \
-vnc :0 \
-device VGA \
-monitor stdio \
-qmp tcp:0:1234,server,nowait \
2.start listening port on dst host with commands:
/usr/libexec/qemu-kvm \
-enable-kvm \
-machine q35  \
-m 4096 \
-smp 4 \
-cpu Skylake-Client \
-name debug-threads=on \
-device pcie-root-port,id=pcie.0-root-port-2,slot=2,chassis=2,addr=0x2,bus=pcie.0 \
-device pcie-root-port,id=pcie.0-root-port-3,slot=3,chassis=3,addr=0x3,bus=pcie.0 \
-device pcie-root-port,id=pcie.0-root-port-4,slot=4,chassis=4,addr=0x4,bus=pcie.0 \
-device virtio-scsi-pci,id=virtio_scsi_pci0,bus=pcie.0-root-port-2,addr=0x0 \
-blockdev driver=file,cache.direct=off,cache.no-flush=on,filename=/mnt/nfs/rhel810-64-virtio-scsi-2.qcow2,node-name=my_file \
-blockdev driver=qcow2,node-name=my_disk,file=my_file \
-device scsi-hd,drive=my_disk,bus=virtio_scsi_pci0.0 \
-netdev tap,id=hostnet0,vhost=on,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown,queues=4 \
-device virtio-net-pci,netdev=hostnet0,id=net0,mac=70:5a:0f:38:cd:1c,bus=pcie.0-root-port-3,vectors=10,mq=on \
-vnc :0 \
-device VGA \
-monitor stdio \
-qmp tcp:0:1234,server,nowait \
-incoming rdma:0:5555 \
3.enable rdma on src host qemu, enable multifd on both src and dst host qemu:
(src qemu) migrate_set_capability rdma-pin-all on
(src qemu) migrate_set_capability multifd on
(dst qemu) migrate_set_capability multifd on


Actual results:
qemu core dump on src and dst host.
(src host):
(qemu) migrate rdma:192.168.0.21:5555
source_resolve_host RDMA Device opened: kernel name mlx4_0 uverbs device name uverbs0, infiniband_verbs class device path /sys/class/infiniband_verbs/uverbs0, infiniband class device path /sys/class/infiniband/mlx4_0, transport: (1) Infiniband
./start2.sh: line 21: 14612 Segmentation fault      (core dumped) /usr/libexec/qemu-kvm -enable-kvm ...

(dst host):
(qemu) dest_init RDMA Device opened: kernel name mlx4_0 uverbs device name uverbs0, infiniband_verbs class device path /sys/class/infiniband_verbs/uverbs0, infiniband class device path /sys/class/infiniband/mlx4_0, transport: (1) Infiniband
qemu-kvm: receive cm event, cm event is 10
qemu-kvm: rdma migration: recv polling control error!
qemu-kvm: RDMA is in an error state waiting migration to abort!
qemu-kvm: Not a migration stream
qemu-kvm: load of migration failed: Invalid argument
qemu-kvm: Early error. Sending error.
qemu-kvm: rdma migration: send polling control error
./start2.sh: line 22: 18542 Segmentation fault      (core dumped) /usr/libexec/qemu-kvm ...


Expected results:
no qemu core dump.


Additional info:
when do separate tests for rdma and multifd, they all work well, no qemu core dump.