[root@arch-zfs-test ~]# journalctl -f
-- Logs begin at Sat 2017-04-15 01:20:58 EEST. --
May 03 02:18:05 arch-zfs-test systemd[1493]: Starting D-Bus User Message Bus Socket.
May 03 02:18:05 arch-zfs-test systemd[1493]: Reached target Timers.
May 03 02:18:05 arch-zfs-test systemd[1493]: Listening on D-Bus User Message Bus Socket.
May 03 02:18:05 arch-zfs-test systemd[1493]: Reached target Sockets.
May 03 02:18:05 arch-zfs-test systemd[1493]: Reached target Basic System.
May 03 02:18:05 arch-zfs-test systemd[1493]: Reached target Default.
May 03 02:18:05 arch-zfs-test systemd[1493]: Startup finished in 25ms.
May 03 02:18:05 arch-zfs-test systemd[1]: Started User Manager for UID 0.
May 03 02:18:05 arch-zfs-test login[1489]: ROOT LOGIN ON hvc0
May 03 02:18:06 arch-zfs-test dhcpcd[1486]: eth0: no IPv6 Routers available

# After the 1st `xl block-attach` command:

May 03 02:25:53 arch-zfs-test kernel: xen-blkback: backend/vbd/0/51712: using 4 queues, protocol 1 (x86_64-abi) persistent grants
May 03 02:25:53 arch-zfs-test root[1550]: /etc/xen/scripts/block: add XENBUS_PATH=backend/vbd/0/51712
May 03 02:25:53 arch-zfs-test root[1602]: /etc/xen/scripts/block: Writing backend/vbd/0/51712/physical-device e6:0 to xenstore.
May 03 02:25:53 arch-zfs-test root[1604]: /etc/xen/scripts/block: Writing backend/vbd/0/51712/physical-device-path /dev/zd0 to xenstore.
May 03 02:25:53 arch-zfs-test root[1611]: /etc/xen/scripts/block: Writing backend/vbd/0/51712/hotplug-status connected to xenstore.

# After the 2nd `xl block-attach` command:

May 03 02:28:12 arch-zfs-test kernel: xen-blkback: backend/vbd/0/51728: using 1 queues, protocol 1 (x86_64-abi) persistent grants
May 03 02:28:12 arch-zfs-test kernel: xen-blkback: backend/vbd/0/51728: using 1 queues, protocol 1 (x86_64-abi) persistent grants
May 03 02:28:12 arch-zfs-test root[1637]: /etc/xen/scripts/block: add XENBUS_PATH=backend/vbd/0/51728
May 03 02:28:12 arch-zfs-test root[1691]: /etc/xen/scripts/block: Writing backend/vbd/0/51728/physical-device e6:20 to xenstore.
May 03 02:28:12 arch-zfs-test root[1693]: /etc/xen/scripts/block: Writing backend/vbd/0/51728/physical-device-path /dev/zd32 to xenstore.
May 03 02:28:12 arch-zfs-test root[1697]: /etc/xen/scripts/block: Writing backend/vbd/0/51728/hotplug-status connected to xenstore.

# After the 1st `xl block-detach` command:

May 03 02:29:21 arch-zfs-test root[1712]: /etc/xen/scripts/block: remove XENBUS_PATH=backend/vbd/0/51712

# After the 2nd `xl block-detach` command:

May 03 02:30:28 arch-zfs-test kernel: traps: xl[1403] general protection ip:7f49bf42519d sp:7ffc601e6dd0 error:0
May 03 02:30:28 arch-zfs-test kernel:  in libxenlight.so.4.8.0[7f49bf3f8000+dd000]
May 03 02:30:28 arch-zfs-test systemd[1]: Created slice system-systemd\x2dcoredump.slice.
May 03 02:30:28 arch-zfs-test systemd[1]: Started Process Core Dump (PID 1722/UID 0).
May 03 02:30:28 arch-zfs-test systemd[1]: xendriverdomain.service: Main process exited, code=dumped, status=11/SEGV
May 03 02:30:28 arch-zfs-test systemd[1]: xendriverdomain.service: Unit entered failed state.
May 03 02:30:28 arch-zfs-test systemd[1]: xendriverdomain.service: Failed with result 'core-dump'.
May 03 02:30:28 arch-zfs-test systemd-coredump[1725]: Process 1403 (xl) of user 0 dumped core.

                                                      Stack trace of thread 1403:
                                                      #0  0x00007f49bf42519d search_for_guest (libxenlight.so.4.8)
                                                      #1  0x00007f49bf425931 backend_watch_callback (libxenlight.so.4.8)
                                                      #2  0x00007f49bf4629da watchfd_callback (libxenlight.so.4.8)
                                                      #3  0x00007f49bf464612 fd_occurs (libxenlight.so.4.8)
                                                      #4  0x00007f49bf4646c4 afterpoll_internal (libxenlight.so.4.8)
                                                      #5  0x00007f49bf465dfd eventloop_iteration (libxenlight.so.4.8)
                                                      #6  0x00007f49bf466bb1 libxl__ao_inprogress (libxenlight.so.4.8)
                                                      #7  0x00007f49bf4261dc libxl_device_events_handler (libxenlight.so.4.8)
                                                      #8  0x0000000000423258 main_devd (xl)
                                                      #9  0x0000000000408e05 main (xl)
                                                      #10 0x00007f49bea49511 __libc_start_main (libc.so.6)
                                                      #11 0x000000000040800a _start (xl)

                                                      Stack trace of thread 1404:
                                                      #0  0x00007f49bedddf7d read (libpthread.so.0)
                                                      #1  0x00007f49be1b5c3d read_all (libxenstore.so.3.0)
                                                      #2  0x00007f49be1b76ca read_message (libxenstore.so.3.0)
                                                      #3  0x00007f49be1b7a1f read_thread (libxenstore.so.3.0)
                                                      #4  0x00007f49bedd42e7 start_thread (libpthread.so.0)
                                                      #5  0x00007f49beb1554f __clone (libc.so.6)