migration: Allow "device add" options to only add migratable devices

Introduce checks for the unmigratable flag in the VMStateDescription
structs of respective devices when user attempts to add them. If the
"--only-migratable" was specified, all unmigratable devices will
rightly fail to add. This feature is made compatible for both "-device"
and "-usbdevice" command line options and covers their hmp and qmp
counterparts as well.

Signed-off-by: Ashijeet Acharya <ashijeetacharya@gmail.com>
Message-Id: <1484566314-3987-4-git-send-email-ashijeetacharya@gmail.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

hw/usb/bus.c

@@ -8,6 +8,7 @@
 #include "monitor/monitor.h"
 #include "trace.h"
 #include "qemu/cutils.h"
+#include "migration/migration.h"
 
 static void usb_bus_dev_print(Monitor *mon, DeviceState *qdev, int indent);
 
@@ -686,6 +687,8 @@ USBDevice *usbdevice_create(const char *cmdline)
     const char *params;
     int len;
     USBDevice *dev;
+    ObjectClass *klass;
+    DeviceClass *dc;
 
     params = strchr(cmdline,':');
     if (params) {
@@ -720,6 +723,22 @@ USBDevice *usbdevice_create(const char *cmdline)
         return NULL;
     }
 
+    klass = object_class_by_name(f->name);
+    if (klass == NULL) {
+        error_report("Device '%s' not found", f->name);
+        return NULL;
+    }
+
+    dc = DEVICE_CLASS(klass);
+
+    if (only_migratable) {
+        if (dc->vmsd->unmigratable) {
+            error_report("Device %s is not migratable, but --only-migratable "
+                         "was specified", f->name);
+            return NULL;
+        }
+    }
+
     if (f->usbdevice_init) {
         dev = f->usbdevice_init(bus, params);
     } else {

qdev-monitor.c

@@ -29,6 +29,7 @@
 #include "qemu/error-report.h"
 #include "qemu/help_option.h"
 #include "sysemu/block-backend.h"
+#include "migration/migration.h"
 
 /*
  * Aliases were a bad idea from the start.  Let's keep them
@@ -577,6 +578,14 @@ DeviceState *qdev_device_add(QemuOpts *opts, Error **errp)
         return NULL;
     }
 
+    if (only_migratable) {
+        if (dc->vmsd->unmigratable) {
+            error_setg(errp, "Device %s is not migratable, but "
+                       "--only-migratable was specified", driver);
+            return NULL;
+        }
+    }
+
     /* find bus */
     path = qemu_opt_get(opts, "bus");
     if (path != NULL) {