Description of problem:
 Qemu coredump after times reboot with info: qemu-kvm: /builddir/build/BUILD/qemu-4.1.0-rc4/hw/virtio/virtio.c:225: vring_get_region_caches: Assertion `caches != NULL' failed

Version-Release number of selected component (if applicable):
  kernel version:4.18.0-131.el8.x86_64
  qemu-kvm version:qemu-kvm-4.1.0-1.module+el8.1.0+3966+4a23dca1.x86_64

How reproducible:
 1/20

Steps to Reproduce:
 Run auto case:
   python3 ConfigTest.py --guestname=RHEL.8.1.0 --platform=x86_64 --driveformat=virtio_blk --testcase=system_reset_during_boot

Actual results:
 QEMU Coredump with info:
Context: Reset guest system for 20 times
03:49:54 DEBUG| (monitor avocado-vt-vm1.qmpmonitor1) Sending command 'system_reset'
03:49:54 DEBUG| Send command: {'execute': 'system_reset', 'id': 'J52fBt63'}
03:49:54 DEBUG| Reset the system by monitor cmd after 6.506secs
03:49:54 INFO | [qemu output] qemu-kvm: /builddir/build/BUILD/qemu-4.1.0-rc4/hw/virtio/virtio.c:225: vring_get_region_caches: Assertion `caches != NULL' failed.
03:50:00 INFO | Context: Try to login guest after reset
03:50:00 DEBUG| Attempting to log into 'avocado-vt-vm1' (timeout 360s)
03:50:00 DEBUG| Retry verifying IP address (0.000003 secs)
03:50:54 WARNI| avocado-vt-vm1 is not alive. Can't query the register status
03:50:54 INFO | [qemu output] /tmp/aexpect_11vLqXgz/aexpect-rnlv70s4.sh: line 1: 10702 Aborted                 (core dumped) MALLOC_PERTURB_=1 /usr/libexec/qemu-kvm -S -name 'avocado-vt-vm1' -machine pc -nodefaults -device VGA,bus=pci.0,addr=0x2 -chardev socket,id=qmp_id_qmpmonitor1,path=/var/tmp/avocado_prq6kc9u/monitor-qmpmonitor1-20190819-034410-dVPr2RwS,server,nowait -mon chardev=qmp_id_qmpmonitor1,mode=control -chardev socket,id=qmp_id_catch_monitor,path=/var/tmp/avocado_prq6kc9u/monitor-catch_monitor-20190819-034410-dVPr2RwS,server,nowait -mon chardev=qmp_id_catch_monitor,mode=control -device pvpanic,ioport=0x505,id=idQKdDpP -chardev socket,id=chardev_serial0,server,path=/var/tmp/avocado_prq6kc9u/serial-serial0-20190819-034410-dVPr2RwS,nowait -device isa-serial,id=serial0,chardev=chardev_serial0 -chardev socket,id=seabioslog_id_20190819-034410-dVPr2RwS,path=/var/tmp/avocado_prq6kc9u/seabios-20190819-034410-dVPr2RwS,server,nowait -device isa-debugcon,chardev=seabioslog_id_20190819-034410-dVPr2RwS,iobase=0x402 -device qemu-xhci,id=usb1,bus=pci.0,addr=0x3 -drive id=drive_image1,if=none,snapshot=off,cache=none,format=qcow2,file=/home/kvm_autotest_root/images/rhel810-64-virtio.qcow2 -device virtio-blk-pci,id=image1,drive=drive_image1,bootindex=0,bus=pci.0,addr=0x4 -device virtio-net-pci,mac=9a:fa:fd:23:3c:7b,id=id6aKPy5,netdev=idIJ8dby,bus=pci.0,addr=0x5 -netdev tap,id=idIJ8dby,vhost=on,vhostfd=24,fd=19 -m 7168 -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

Expected results:
 System reset executed successfully during vm reboot.

Additional info:
(gdb) bt
#0  0x00007f94645928df in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
#1  0x00007f946457ccf5 in __GI_abort () at abort.c:79
#2  0x00007f946457cbc9 in __assert_fail_base
    (fmt=0x7f94646e3300 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n", assertion=0x5631b257f246 "caches != NULL", file=0x5631b257ed68 "/builddir/build/BUILD/qemu-4.1.0-rc4/hw/virtio/virtio.c", line=225, function=<optimized out>) at assert.c:92
#3  0x00007f946458ae96 in __GI___assert_fail
    (assertion=assertion@entry=0x5631b257f246 "caches != NULL", file=file@entry=0x5631b257ed68 "/builddir/build/BUILD/qemu-4.1.0-rc4/hw/virtio/virtio.c", line=line@entry=225, function=function@entry=0x5631b257fb20 <__PRETTY_FUNCTION__.29391> "vring_get_region_caches") at assert.c:101
#4  0x00005631b221593a in vring_get_region_caches (vq=<optimized out>)
    at /usr/src/debug/qemu-kvm-4.1.0-1.module+el8.1.0+3966+4a23dca1.x86_64/hw/virtio/virtio.c:225
#5  0x00005631b221593a in vring_get_region_caches (vq=<optimized out>)
    at /usr/src/debug/qemu-kvm-4.1.0-1.module+el8.1.0+3966+4a23dca1.x86_64/hw/virtio/virtio.c:222
#6  0x00005631b22163b0 in vring_avail_flags (vq=0x7f945c00d010)
    at /usr/src/debug/qemu-kvm-4.1.0-1.module+el8.1.0+3966+4a23dca1.x86_64/hw/virtio/virtio.c:1667
#7  0x00005631b22163b0 in virtio_should_notify (vdev=vdev@entry=0x5631b51e3d50, vq=vq@entry=0x7f945c00d010)
    at /usr/src/debug/qemu-kvm-4.1.0-1.module+el8.1.0+3966+4a23dca1.x86_64/hw/virtio/virtio.c:1667
#8  0x00005631b2217913 in virtio_notify_irqfd (vdev=0x5631b51e3d50, vq=0x7f945c00d010)
    at /usr/src/debug/qemu-kvm-4.1.0-1.module+el8.1.0+3966+4a23dca1.x86_64/hw/virtio/virtio.c:1681
#9  0x00005631b21ecdd7 in notify_guest_bh (opaque=0x5631b51effa0)
    at /usr/src/debug/qemu-kvm-4.1.0-1.module+el8.1.0+3966+4a23dca1.x86_64/hw/block/dataplane/virtio-blk.c:75
#10 0x00005631b24c98e6 in aio_bh_call (bh=0x5631b51efff0) at util/async.c:117
#11 0x00005631b24c98e6 in aio_bh_poll (ctx=ctx@entry=0x5631b41abff0) at util/async.c:117
#12 0x00005631b24ccd24 in aio_dispatch (ctx=0x5631b41abff0) at util/aio-posix.c:459
#13 0x00005631b24c97c2 in aio_ctx_dispatch (source=<optimized out>, callback=<optimized out>, user_data=<optimized out>)
    at util/async.c:260
#14 0x00007f946940e67d in g_main_dispatch (context=0x5631b41ad440) at gmain.c:3176
#15 0x00007f946940e67d in g_main_context_dispatch (context=context@entry=0x5631b41ad440) at gmain.c:3829
#16 0x00005631b24cbdd8 in glib_pollfds_poll () at util/main-loop.c:218
#17 0x00005631b24cbdd8 in os_host_main_loop_wait (timeout=<optimized out>) at util/main-loop.c:241
#18 0x00005631b24cbdd8 in main_loop_wait (nonblocking=<optimized out>) at util/main-loop.c:517
--Type <RET> for more, q to quit, c to continue without paging--
#19 0x00005631b22b48c9 in main_loop () at vl.c:1809
#20 0x00005631b2164983 in main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at vl.c:4506