[PATCH] hw/i386/vmmouse: Fix crash when using the vmmouse on a machine without vmport

[Thomas Huth]

QEMU currently crashes when the user tries to use the "vmmouse" on a
machine without vmport, e.g.:

 $ x86_64-softmmu/qemu-system-x86_64 -machine microvm -device vmmouse
 Segmentation fault (core dumped)

or:

 $ x86_64-softmmu/qemu-system-x86_64 -device vmmouse -M pc,vmport=off
 Segmentation fault (core dumped)

Let's avoid the crash by checking for the vmport device first.

Signed-off-by: Thomas Huth <th...@redhat.com>
---
 hw/i386/vmmouse.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/hw/i386/vmmouse.c b/hw/i386/vmmouse.c
index 7c2a375527..e8e62bd96b 100644
--- a/hw/i386/vmmouse.c
+++ b/hw/i386/vmmouse.c
@@ -23,6 +23,7 @@
  */
 
 #include "qemu/osdep.h"
+#include "qapi/error.h"
 #include "ui/console.h"
 #include "hw/i386/pc.h"
 #include "hw/input/i8042.h"
@@ -269,6 +270,11 @@ static void vmmouse_realizefn(DeviceState *dev, Error 
**errp)
 
     DPRINTF("vmmouse_init\n");
 
+    if (!object_resolve_path_type("", TYPE_VMPORT, NULL)) {
+        error_setg(errp, "vmmouse needs a machine with vmport");
+        return;
+    }
+
     vmport_register(VMMOUSE_STATUS, vmmouse_ioport_read, s);
     vmport_register(VMMOUSE_COMMAND, vmmouse_ioport_read, s);
     vmport_register(VMMOUSE_DATA, vmmouse_ioport_read, s);
-- 
2.18.1