QEMU currently abort()s if the user tries to specify the mmio_interface
device without parameters:

x86_64-softmmu/qemu-system-x86_64 -nographic -device mmio_interface
qemu-system-x86_64: /home/thuth/devel/qemu/util/error.c:57: error_setv:
 Assertion `*errp == ((void *)0)' failed.
Aborted (core dumped)

This happens because the realize function is trying to set the errp
twice in this case. After setting an error, the realize function
should immediately return instead.

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 hw/misc/mmio_interface.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/hw/misc/mmio_interface.c b/hw/misc/mmio_interface.c
index 6f004d2..da154e5 100644
--- a/hw/misc/mmio_interface.c
+++ b/hw/misc/mmio_interface.c
@@ -63,10 +63,12 @@ static void mmio_interface_realize(DeviceState *dev, Error **errp)
 
     if (!s->host_ptr) {
         error_setg(errp, "host_ptr property must be set");
+        return;
     }
 
     if (!s->subregion) {
         error_setg(errp, "subregion property must be set");
+        return;
     }
 
     memory_region_init_ram_ptr(&s->ram_mem, OBJECT(s), "ram",
-- 
1.8.3.1