Comment 1 for bug 1859527

Thread 1 (Thread 0x7f2a00963640 (LWP 15030)):
#0 __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
#1 0x00007f29fabdd801 in __GI_abort () at abort.c:79
#2 0x00007f29fabcd39a in __assert_fail_base (fmt=0x7f29fad547d8 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n", assertion=assertion@entry=0x5624a8e2419e "caches != NULL", file=file@entry=0x5624a8e23b80 "/build/qemu-XrmZRw/qemu-2.11+dfsg/hw/virtio/virtio.c", line=line@entry=211, function=function@entry=0x5624a8e249f0 <__PRETTY_FUNCTION__.30338> "vring_get_region_caches") at assert.c:92
#3 0x00007f29fabcd412 in __GI___assert_fail (assertion=assertion@entry=0x5624a8e2419e "caches != NULL", file=file@entry=0x5624a8e23b80 "/build/qemu-XrmZRw/qemu-2.11+dfsg/hw/virtio/virtio.c", line=line@entry=211, function=function@entry=0x5624a8e249f0 <__PRETTY_FUNCTION__.30338> "vring_get_region_caches") at assert.c:101
#4 0x00005624a8a0bcbc in vring_get_region_caches (vq=<optimized out>) at ./hw/virtio/virtio.c:211
#5 0x00005624a8aa88d7 in vring_get_region_caches (vq=<optimized out>) at ./hw/virtio/virtio.c:1628
#6 vring_avail_flags (vq=<optimized out>) at ./hw/virtio/virtio.c:217
#7 virtio_should_notify (vdev=<optimized out>, vq=<optimized out>) at ./hw/virtio/virtio.c:1632
#8 0x00005624a8aaa0b5 in virtio_notify_irqfd (vdev=0x5624af9342b0, vq=0x7f26a0655110) at ./hw/virtio/virtio.c:1646
#9 0x00005624a8a7c05f in notify_guest_bh (opaque=0x5624af93f420) at ./hw/block/dataplane/virtio-blk.c:71
#10 0x00005624a8ded30e in aio_bh_call (bh=0x5624af93ebd0) at ./util/async.c:90
#11 aio_bh_poll (ctx=ctx@entry=0x5624aa267fb0) at ./util/async.c:118
#12 0x00005624a8df0200 in aio_dispatch (ctx=0x5624aa267fb0) at ./util/aio-posix.c:436
#13 0x00005624a8ded1ee in aio_ctx_dispatch (source=<optimized out>, callback=<optimized out>, user_data=<optimized out>) at ./util/async.c:261
#14 0x00007f29fb9b7417 in g_main_context_dispatch () from /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0
#15 0x00005624a8def457 in glib_pollfds_poll () at ./util/main-loop.c:214
#16 os_host_main_loop_wait (timeout=<optimized out>) at ./util/main-loop.c:261
#17 main_loop_wait (nonblocking=<optimized out>) at ./util/main-loop.c:515
#18 0x00005624a8a12ef6 in main_loop () at ./vl.c:1995
#19 main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at ./vl.c:4944