[Qemu-devel] [PATCH v3] migrate: Introduce a 'dc->vmsd' check to avoid segfault for --only-migratable

[Ashijeet Acharya]

Commit a3a3d8c7 introduced a segfault bug while checking for
'dc->vmsd->unmigratable' which caused QEMU to crash when trying to add
devices which do no set their 'dc->vmsd' yet while initialization.
Place a 'dc->vmsd' check prior to it so that we do not segfault for
such devices.

NOTE: This doesn't compromise the functioning of --only-migratable
option as all the unmigratable devices do set their 'dc->vmsd'.

Also, move the only_migratable check inside device_set_realized() to avoid
code duplication and fix the bug to display only_migratable error message
only if the device constructuon is right.

Signed-off-by: Ashijeet Acharya <address@hidden>
---
Changes is v3:
- move only_migratable check inside device_set_realized() to avoid code 
- duplication
- I have dropped Juan's R-b tag for this one
Changes in v2:
- place dc->vmsd check in hw/usb/bus.c as well
---
 hw/core/qdev.c | 10 ++++++++++
 hw/usb/bus.c   | 19 -------------------
 qdev-monitor.c |  9 ---------
 3 files changed, 10 insertions(+), 28 deletions(-)

diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index 5783442..4438cbf 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -37,6 +37,7 @@
 #include "hw/boards.h"
 #include "hw/sysbus.h"
 #include "qapi-event.h"
+#include "migration/migration.h"
 
 int qdev_hotplug = 0;
 static bool qdev_hot_added = false;
@@ -896,6 +897,15 @@ static void device_set_realized(Object *obj, bool value, 
Error **errp)
     }
 
     if (value && !dev->realized) {
+        if (only_migratable && dc->vmsd) {
+            if (dc->vmsd->unmigratable) {
+                error_setg(&local_err, "Device %s is not migratable, but "
+                           "--only-migratable was specified",
+                           object_get_typename(obj));
+                goto fail;
+            }
+        }
+
         if (!obj->parent) {
             gchar *name = g_strdup_printf("device[%d]", unattached_count++);
 
diff --git a/hw/usb/bus.c b/hw/usb/bus.c
index 1dcc35c..25913ad 100644
--- a/hw/usb/bus.c
+++ b/hw/usb/bus.c
@@ -8,7 +8,6 @@
 #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);
 
@@ -687,8 +686,6 @@ USBDevice *usbdevice_create(const char *cmdline)
     const char *params;
     int len;
     USBDevice *dev;
-    ObjectClass *klass;
-    DeviceClass *dc;
 
     params = strchr(cmdline,':');
     if (params) {
@@ -723,22 +720,6 @@ 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 {
diff --git a/qdev-monitor.c b/qdev-monitor.c
index 549f45f..5f2fcdf 100644
--- a/qdev-monitor.c
+++ b/qdev-monitor.c
@@ -29,7 +29,6 @@
 #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
@@ -579,14 +578,6 @@ 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) {
-- 
2.6.2