s390: disallow memory hotplug for the s390-virtio machine

That machine type doesn't currently support memory hotplug, so let's abort
if it is requested. Reason is, that the virtio queues are allocated for now
at the end of the initial ram - extending the ram is therefore not possible.

Reviewed-by: Matthew Rosato <mjrosato@linux.vnet.ibm.com>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
diff --git a/hw/s390x/s390-virtio.c b/hw/s390x/s390-virtio.c
index 6cc6b5d..b0f339e 100644
--- a/hw/s390x/s390-virtio.c
+++ b/hw/s390x/s390-virtio.c
@@ -23,6 +23,7 @@
 
 #include "hw/hw.h"
 #include "qapi/qmp/qerror.h"
+#include "qemu/error-report.h"
 #include "sysemu/block-backend.h"
 #include "sysemu/blockdev.h"
 #include "sysemu/sysemu.h"
@@ -268,6 +269,10 @@
     hwaddr virtio_region_len;
     hwaddr virtio_region_start;
 
+    if (machine->ram_slots) {
+        error_report("Memory hotplug not supported by the selected machine.");
+        exit(EXIT_FAILURE);
+    }
     /*
      * The storage increment size is a multiple of 1M and is a power of 2.
      * The number of storage increments must be MAX_STORAGE_INCREMENTS or