On master (13b7b188501) and v3.0.0, booting the OpenBSD install63.iso with a virtio-net (slirp backend) device gives this assertion failure:
(gdb) bt #0 0x00007f6f25703feb in raise () at /lib64/libc.so.6 #1 0x00007f6f256ee5c1 in abort () at /lib64/libc.so.6 #2 0x00007f6f256ee491 in _nl_load_domain.cold.0 () at /lib64/libc.so.6 #3 0x00007f6f256fc752 in () at /lib64/libc.so.6 #4 0x000055d966f5b5d6 in address_space_stw_le_cached (cache=0x7f6f040fd700, addr=516, val=1, attrs=..., result=0x0) at /stor/work/qemu/include/exec/memory_ldst_cached.inc.h:85 #5 0x000055d966f5b804 in stw_le_phys_cached (cache=0x7f6f040fd700, addr=516, val=1) at /stor/work/qemu/include/exec/memory_ldst_phys.inc.h:121 #6 0x000055d966f5c3e7 in virtio_stw_phys_cached (vdev=0x55d969aeeff0, cache=0x7f6f040fd700, pa=516, value=1) at /stor/work/qemu/include/hw/virtio/virtio-access.h:195 #7 0x000055d966f5cef8 in vring_set_avail_event (vq=0x7f6f181df110, val=1) at /stor/work/qemu/hw/virtio/virtio.c:324 #8 0x000055d966f5e1c8 in virtqueue_pop (vq=0x7f6f181df110, sz=48) at /stor/work/qemu/hw/virtio/virtio.c:883 #9 0x000055d966f2d69b in virtio_net_handle_ctrl (vdev=0x55d969aeeff0, vq=0x7f6f181df110) at /stor/work/qemu/hw/net/virtio-net.c:986 #10 0x000055d966f5ffb9 in virtio_queue_notify_vq (vq=0x7f6f181df110) at /stor/work/qemu/hw/virtio/virtio.c:1534 #11 0x000055d966f6224d in virtio_queue_host_notifier_read (n=0x7f6f181df178) at /stor/work/qemu/hw/virtio/virtio.c:2451 #12 0x000055d9673ef460 in aio_dispatch_handlers (ctx=0x55d96891af90) at /stor/work/qemu/util/aio-posix.c:406 #13 0x000055d9673ef5f3 in aio_dispatch (ctx=0x55d96891af90) at /stor/work/qemu/util/aio-posix.c:437 #14 0x000055d9673eae25 in aio_ctx_dispatch (source=0x55d96891af90, callback=0x0, user_data=0x0) at /stor/work/qemu/util/async.c:261 #15 0x00007f6f28b578ad in g_main_context_dispatch () at /lib64/libglib-2.0.so.0 #16 0x000055d9673ee040 in glib_pollfds_poll () at /stor/work/qemu/util/main-loop.c:215 #17 0x000055d9673ee0ae in os_host_main_loop_wait (timeout=0) at /stor/work/qemu/util/main-loop.c:238 #18 0x000055d9673ee167 in main_loop_wait (nonblocking=0) at /stor/work/qemu/util/main-loop.c:497 #19 0x000055d96702efd0 in main_loop () at /stor/work/qemu/vl.c:1866 #20 0x000055d9670368bd in main (argc=22, argv=0x7ffdef327638, envp=0x7ffdef3276f0) at /stor/work/qemu/vl.c:4644 No surprise, bisection points to commit 48564041a73adbbff52834f9edbe3806fceefab7 Author: Paolo Bonzini <pbonz...@redhat.com> Date: Sun Mar 18 18:26:36 2018 +0100 exec: reintroduce MemoryRegion caching Fam