Description of problem:
Qemu hit core dump when dump guest memory during live migration


Version-Release number of selected component (if applicable):
hosts info: kernel-5.14.0-0.rc4.35.el9.x86_64 & qemu-kvm-6.0.0-12.el9.x86_64
guest info: kernel-5.13.0-0.rc7.51.el9.x86_64


How reproducible:
not always, 67%


Steps to Reproduce:
1.Boot a vm with "-device vmcoreinfo" qemu cli[1]
2.Boot a vm with qemu cli[1] and append '-incoming defer'
3.Migrate vm from src to dst;
dst qmp:
{"execute": "migrate-incoming", "arguments": {"uri": "tcp:[::]:4000"}, "id": "ApNFq8XX"}
src qmp:
{"execute": "migrate", "arguments": {"uri": "tcp:$dst_host_ip:4000"}, "id": "XhomThrr"}
4.Dump guest memory at once after finishing step 3 to ensure dump happen during migration is active 
{"execute": "dump-guest-memory", "arguments": {"paging": false, "protocol": "file:/home/dump.elf", "format": "elf"}, "id": "1Xlxq06O"}


Actual results:
Dump file generated, but wait several minutes, qemu core dump after step 4:
[root@ibm-x3250m6-07 home]# coredumpctl info 10417
           PID: 10417 (qemu-kvm)
           UID: 0 (root)
           GID: 0 (root)
        Signal: 6 (ABRT)
     Timestamp: Mon 2021-08-23 07:39:43 UTC (6min ago)
  Command Line: /usr/libexec/qemu-kvm -name mouse-vm -sandbox off -machine q35 -cpu Skylak>
    Executable: /usr/libexec/qemu-kvm
 Control Group: /user.slice/user-0.slice/session-3.scope
          Unit: session-3.scope
         Slice: user-0.slice
       Session: 3
     Owner UID: 0 (root)
       Boot ID: 578f283d1e9c49308eff359d36a38c41
    Machine ID: 5815313cf4814dd18bb08b6a5552e5e2
      Hostname: ibm-x3250m6-07.lab.eng.pek2.redhat.com
       Storage: none
       Message: Process 10417 (qemu-kvm) of user 0 dumped core.
                
                Stack trace of thread 10573:
                #0  0x00007f90a8ab3763 pthread_kill.5 (libc.so.6 + 0x8f763)
                #1  0x00007f90a8a66686 raise (libc.so.6 + 0x42686)
                #2  0x00007f90a8a507d3 abort (libc.so.6 + 0x2c7d3)
                #3  0x00007f90a8a506fb __assert_fail_base.cold (libc.so.6 + 0x2c6fb)
                #4  0x00007f90a8a5f3a6 __assert_fail (libc.so.6 + 0x3b3a6)
                #5  0x000055d85ef82a24 virtio_net_pre_save (qemu-kvm + 0x5e5a24)
                #6  0x000055d85ecef406 vmstate_save_state_v (qemu-kvm + 0x352406)
                #7  0x000055d85ee95ea0 qemu_savevm_state_complete_precopy_non_iterable (qe>
                #8  0x000055d85ee967bc qemu_savevm_state_complete_precopy (qemu-kvm + 0x4f>
                #9  0x000055d85ed4d6a2 migration_thread (qemu-kvm + 0x3b06a2)
                #10 0x000055d85f30bf3a qemu_thread_start (qemu-kvm + 0x96ef3a)
                #11 0x00007f90a8ab1a8f start_thread (libc.so.6 + 0x8da8f)
                #12 0x00007f90a8b36480 __clone3 (libc.so.6 + 0x112480)
                
                Stack trace of thread 10418:
                #0  0x00007f90a8b2efbd syscall (libc.so.6 + 0x10afbd)
                #1  0x000055d85f30bcaf qemu_event_wait (qemu-kvm + 0x96ecaf)
                #2  0x000055d85f30476f call_rcu_thread (qemu-kvm + 0x96776f)
                #3  0x000055d85f30bf3a qemu_thread_start (qemu-kvm + 0x96ef3a)
                #4  0x00007f90a8ab1a8f start_thread (libc.so.6 + 0x8da8f)
                #5  0x00007f90a8b36480 __clone3 (libc.so.6 + 0x112480)
                
                Stack trace of thread 10437:
                #0  0x00007f90a8aae75a __futex_abstimed_wait_common (libc.so.6 + 0x8a75a)
                #1  0x00007f90a8ab0ed0 pthread_cond_wait@@GLIBC_2.3.2 (libc.so.6 + 0x8ced0)
                #2  0x000055d85f30b6df qemu_cond_wait_impl (qemu-kvm + 0x96e6df)
                #3  0x000055d85f069f87 qemu_wait_io_event (qemu-kvm + 0x6ccf87)
                #4  0x000055d85f033791 kvm_vcpu_thread_fn (qemu-kvm + 0x696791)
                #5  0x000055d85f30bf3a qemu_thread_start (qemu-kvm + 0x96ef3a)
                #6  0x00007f90a8ab1a8f start_thread (libc.so.6 + 0x8da8f)
                #7  0x00007f90a8b36480 __clone3 (libc.so.6 + 0x112480)
                
                Stack trace of thread 10434:
                #0  0x00007f90a8aae75a __futex_abstimed_wait_common (libc.so.6 + 0x8a75a)
                #1  0x00007f90a8ab0ed0 pthread_cond_wait@@GLIBC_2.3.2 (libc.so.6 + 0x8ced0)
                #2  0x000055d85f30b6df qemu_cond_wait_impl (qemu-kvm + 0x96e6df)
                #3  0x000055d85f069f87 qemu_wait_io_event (qemu-kvm + 0x6ccf87)
                #4  0x000055d85f033791 kvm_vcpu_thread_fn (qemu-kvm + 0x696791)
                #5  0x000055d85f30bf3a qemu_thread_start (qemu-kvm + 0x96ef3a)
                #6  0x00007f90a8ab1a8f start_thread (libc.so.6 + 0x8da8f)
                #7  0x00007f90a8b36480 __clone3 (libc.so.6 + 0x112480)
                
                Stack trace of thread 10436:
                #0  0x00007f90a8aae75a __futex_abstimed_wait_common (libc.so.6 + 0x8a75a)
                #1  0x00007f90a8ab0ed0 pthread_cond_wait@@GLIBC_2.3.2 (libc.so.6 + 0x8ced0)
                #2  0x000055d85f30b6df qemu_cond_wait_impl (qemu-kvm + 0x96e6df)
                #3  0x000055d85f069f87 qemu_wait_io_event (qemu-kvm + 0x6ccf87)
                #4  0x000055d85f033791 kvm_vcpu_thread_fn (qemu-kvm + 0x696791)
                #5  0x000055d85f30bf3a qemu_thread_start (qemu-kvm + 0x96ef3a)
                #6  0x00007f90a8ab1a8f start_thread (libc.so.6 + 0x8da8f)
                #7  0x00007f90a8b36480 __clone3 (libc.so.6 + 0x112480)
                
                Stack trace of thread 10430:
                #0  0x00007f90a8b2986f __poll (libc.so.6 + 0x10586f)
                #1  0x00007f90a91a758c g_main_context_iterate.constprop.0 (libglib-2.0.so.>
                #2  0x00007f90a9152563 g_main_loop_run (libglib-2.0.so.0 + 0x54563)
                #3  0x000055d85f118ffc iothread_run (qemu-kvm + 0x77bffc)
                #4  0x000055d85f30bf3a qemu_thread_start (qemu-kvm + 0x96ef3a)
                #5  0x00007f90a8ab1a8f start_thread (libc.so.6 + 0x8da8f)
                #6  0x00007f90a8b36480 __clone3 (libc.so.6 + 0x112480)
                
                Stack trace of thread 10446:
                #0  0x00007f90a8aae75a __futex_abstimed_wait_common (libc.so.6 + 0x8a75a)
                #1  0x00007f90a8ab0ed0 pthread_cond_wait@@GLIBC_2.3.2 (libc.so.6 + 0x8ced0)
                #2  0x000055d85f30b6df qemu_cond_wait_impl (qemu-kvm + 0x96e6df)
                #3  0x000055d85ed3f0f6 vnc_worker_thread (qemu-kvm + 0x3a20f6)
                #4  0x000055d85f30bf3a qemu_thread_start (qemu-kvm + 0x96ef3a)
                #5  0x00007f90a8ab1a8f start_thread (libc.so.6 + 0x8da8f)
                #6  0x00007f90a8b36480 __clone3 (libc.so.6 + 0x112480)
                
                Stack trace of thread 10431:
                #0  0x00007f90a8aae75a __futex_abstimed_wait_common (libc.so.6 + 0x8a75a)
                #1  0x00007f90a8ab0ed0 pthread_cond_wait@@GLIBC_2.3.2 (libc.so.6 + 0x8ced0)
                #2


Expected results:
Migrate completes successfully, dump file generate, vm works well after migration


Additional info:
Qemu core dump file please see attachment.