Info when qemu quit:
 (qemu) qemu: qemu_mutex_unlock_impl: Operation not permitted
blk_debug.txt: line 43:  4499 Aborted                 (core dumped) /usr/local/bin/qemu-system-x86_64 -name 'avocado-vt-vm1' -machine q35 -nodefaults -device VGA,bus=pcie.0,addr=0x1 -chardev socket,id=qmp_id_qmpmonitor1,path=/var/tmp/monitor-qmpmonitor1-20190602-221944-MrlxVzia,server,nowait

Test on qemu-kvm-4.1.0-4.module+el8.1.0+4020+16089f93.x86_64, also hit this issue.

Upstream patch proposed: https://lists.gnu.org/archive/html/qemu-devel/2019-09/msg03400.html
still needs iotest coverage

(In reply to Eric Blake from comment #6)
> Upstream patch proposed:
> https://lists.gnu.org/archive/html/qemu-devel/2019-09/msg03400.html
> still needs iotest coverage

iotest coverage posted as patch 2/1 in the same thread.

Downstream backport proposed:
http://post-office.corp.redhat.com/archives/rhvirt-patches/2019-October/msg00544.html

Test on qemu-kvm-4.1.0-14.module+el8.1.1+4632+a8269660, don't hit this issue any more, set bug's status to "Verified".

1.Start guest with qemu cmds:
   /usr/local/bin/qemu-system-x86_64 \
    -name 'avocado-vt-vm1' \
    -machine q35  \
    -nodefaults \
    -device VGA,bus=pcie.0,addr=0x1  \
    -chardev socket,id=qmp_id_qmpmonitor1,path=/var/tmp/monitor-qmpmonitor1-20190602-221944-MrlxVzia,server,nowait \
    -mon chardev=qmp_id_qmpmonitor1,mode=control  \
    -chardev socket,id=qmp_id_catch_monitor,path=/var/tmp/monitor-catch_monitor-20190602-221944-MrlxVzia,server,nowait \
    -mon chardev=qmp_id_catch_monitor,mode=control \
    -device pvpanic,ioport=0x505,id=idn20piu  \
    -chardev socket,id=serial_id_serial0,path=/var/tmp/serial-serial0-20190602-221944-MrlxVzia,server,nowait \
    -device isa-serial,chardev=serial_id_serial0  \
    -chardev socket,id=seabioslog_id_20190602-221944-MrlxVzia,path=/var/tmp/seabios-20190602-221944-MrlxVzia,server,nowait \
    -device isa-debugcon,chardev=seabioslog_id_20190602-221944-MrlxVzia,iobase=0x402 \
    -device pcie-root-port,id=pcie.0-root-port-2,slot=2,chassis=2,addr=0x2,bus=pcie.0 \
    -device qemu-xhci,id=usb1,bus=pcie.0-root-port-2,addr=0x0 \
    -object iothread,id=iothread0 \
    -object iothread,id=iothread1 \
    -device pcie-root-port,id=pcie.0-root-port-3,slot=3,chassis=3,addr=0x3,bus=pcie.0 \
    -drive driver=qcow2,id=drive_image1,file=/home/kvm_autotest_root/images/rhel810-64-virtio-scsi.qcow2,if=none,cache=none \
    -device virtio-blk-pci,id=image1,drive=drive_image1,bus=pcie.0,iothread=iothread0,bus=pcie.0-root-port-3,addr=0x0 \
    -device pcie-root-port,id=pcie.0-root-port-5,slot=5,chassis=5,addr=0x5,bus=pcie.0 \
    -blockdev driver=file,filename=/mnt/data.qcow2,node-name=file_node \
    -blockdev driver=qcow2,file=file_node,node-name=drive_data1 \
    -device virtio-blk-pci,id=data1,drive=drive_data1,bus=pcie.0-root-port-5,addr=0x0,iothread=iothread0 \
    -device pcie-root-port,id=pcie.0-root-port-6,slot=6,chassis=6,addr=0x6,bus=pcie.0 \
    -drive format=qcow2,file=/mnt/data2.qcow2,id=drive_data2,cache=none,if=none \
    -device virtio-blk-pci,id=data2,drive=drive_data2,bus=pcie.0-root-port-6,addr=0x0 \
    -device pcie-root-port,id=pcie.0-root-port-4,slot=4,chassis=4,addr=0x4,bus=pcie.0 \
    -device virtio-net-pci,mac=9a:33:34:35:36:37,id=idj01pFr,vectors=4,netdev=idMgbx8B,bus=pcie.0-root-port-4,addr=0x0  \
    -netdev tap,id=idMgbx8B,vhost=on \
    -m 4096  \
    -smp 4,maxcpus=4,cores=2,threads=1,sockets=2  \
    -cpu 'Skylake-Client',+kvm_pv_unhalt \
    -device usb-tablet,id=usb-tablet1,bus=usb1.0,port=1  \
    -vnc :0  \
    -rtc base=utc,clock=host,driftfix=slew  \
    -boot order=cdn,once=c,menu=off,strict=off \
    -enable-kvm \
    -monitor stdio \
    -qmp tcp:0:3000,server,nowait \

2.Start ndb server:
   {"execute":"nbd-server-start","arguments":{"addr":{"type":"inet","data":{"host":"10.73.224.68","port":"10809"}}}}

3.Create scratch.img and add it.
   #qemu-img create -f qcow2 -b /mnt/data.qcow2 -F qcow2 scratch.img
   {"execute":"blockdev-add","arguments":{"driver":"qcow2","node-name":"tmp","file":{"driver":"file","filename":"scratch.img"},"backing":"drive_data1"}}

4.Do full backup with sync "none" and add a bitmap
   { "execute": "transaction", "arguments": { "actions": [ {"type": "blockdev-backup", "data": { "device": "drive_data1", "target": "tmp", "sync": "none", "job-id":"j1" } }, {"type": "block-dirty-bitmap-add", "data": { "node": "drive_data1", "name": "bitmap0" } } ] } }

5.Expose full backup node and the bitmap
  {"execute": "nbd-server-add", "arguments": { "device": "tmp", "bitmap": "bitmap0" } }
  {"error": {"class": "GenericError", "desc": "Enabled bitmap 'bitmap0' incompatible with readonly export"}}

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/RHBA-2020:0404