hw/xen: only remove peers of PCI NICs on unplug

When the Xen guest asks to unplug *emulated* NICs, it's kind of unhelpful
also to unplug the peer of the *Xen* PV NIC.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>

hw/i386/xen/xen_platform.c

@@ -140,9 +140,14 @@ static void unplug_nic(PCIBus *b, PCIDevice *d, void *o)
 /* Remove the peer of the NIC device. Normally, this would be a tap device. */
 static void del_nic_peer(NICState *nic, void *opaque)
 {
-    NetClientState *nc;
+    NetClientState *nc = qemu_get_queue(nic);
+    ObjectClass *klass = module_object_class_by_name(nc->model);
+
+    /* Only delete peers of PCI NICs that we're about to delete */
+    if (!klass || !object_class_dynamic_cast(klass, TYPE_PCI_DEVICE)) {
+        return;
+    }
 
-    nc = qemu_get_queue(nic);
     if (nc->peer)
         qemu_del_net_client(nc->peer);
 }