[Qemu-devel] [PATCH v4] migrate: Introduce a 'dc->vmsd' check to avoid segfault for --only-migratable

Ashijeet Acharya posted 1 patch 7 years, 1 month ago
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Test docker passed
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hw/core/qdev.c                |  7 +++++++
hw/usb/bus.c                  | 19 -------------------
include/migration/migration.h |  3 +++
migration/migration.c         | 15 +++++++++++++++
qdev-monitor.c                |  9 ---------
stubs/vmstate.c               |  6 ++++++
6 files changed, 31 insertions(+), 28 deletions(-)
[Qemu-devel] [PATCH v4] migrate: Introduce a 'dc->vmsd' check to avoid segfault for --only-migratable
Posted by Ashijeet Acharya 7 years, 1 month ago
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'.

Introduce a new function check_migratable() and move the
only_migratable check inside it, also use stubs to avoid user-mode qemu
build failures.

Signed-off-by: Ashijeet Acharya <ashijeetacharya@gmail.com>
---
Changes in v4:
- introduce new check_migratable() function and use stubs
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                |  7 +++++++
 hw/usb/bus.c                  | 19 -------------------
 include/migration/migration.h |  3 +++
 migration/migration.c         | 15 +++++++++++++++
 qdev-monitor.c                |  9 ---------
 stubs/vmstate.c               |  6 ++++++
 6 files changed, 31 insertions(+), 28 deletions(-)

diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index 5783442..4f49cfe 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;
@@ -889,6 +890,7 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
     Error *local_err = NULL;
     bool unattached_parent = false;
     static int unattached_count;
+    int ret;
 
     if (dev->hotplugged && !dc->hotpluggable) {
         error_setg(errp, QERR_DEVICE_NO_HOTPLUG, object_get_typename(obj));
@@ -896,6 +898,11 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
     }
 
     if (value && !dev->realized) {
+        ret = check_migratable(obj, &local_err);
+        if (ret < 0) {
+            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/include/migration/migration.h b/include/migration/migration.h
index af9135f..a6868cd 100644
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -22,6 +22,7 @@
 #include "qapi-types.h"
 #include "exec/cpu-common.h"
 #include "qemu/coroutine_int.h"
+#include "qom/object.h"
 
 #define QEMU_VM_FILE_MAGIC           0x5145564d
 #define QEMU_VM_FILE_VERSION_COMPAT  0x00000002
@@ -305,6 +306,8 @@ int migrate_add_blocker(Error *reason, Error **errp);
  */
 void migrate_del_blocker(Error *reason);
 
+int check_migratable(Object *obj, Error **err);
+
 bool migrate_postcopy_ram(void);
 bool migrate_zero_blocks(void);
 
diff --git a/migration/migration.c b/migration/migration.c
index 2766d2f..00b33f3 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1146,6 +1146,21 @@ void migrate_del_blocker(Error *reason)
     migration_blockers = g_slist_remove(migration_blockers, reason);
 }
 
+int check_migratable(Object *obj, Error **err)
+{
+    DeviceClass *dc = DEVICE_GET_CLASS(obj);
+    if (only_migratable && dc->vmsd) {
+        if (dc->vmsd->unmigratable) {
+            error_setg(err, "Device %s is not migratable, but "
+                       "--only-migratable was specified",
+                       object_get_typename(obj));
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
 void qmp_migrate_incoming(const char *uri, Error **errp)
 {
     Error *local_err = NULL;
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) {
diff --git a/stubs/vmstate.c b/stubs/vmstate.c
index 6590627..5a71770 100644
--- a/stubs/vmstate.c
+++ b/stubs/vmstate.c
@@ -1,6 +1,7 @@
 #include "qemu/osdep.h"
 #include "qemu-common.h"
 #include "migration/vmstate.h"
+#include "migration/migration.h"
 
 const VMStateDescription vmstate_dummy = {};
 
@@ -18,3 +19,8 @@ void vmstate_unregister(DeviceState *dev,
                         void *opaque)
 {
 }
+
+int check_migratable(Object *obj, Error **err)
+{
+    return 0;
+}
-- 
2.6.2


Re: [Qemu-devel] [PATCH v4] migrate: Introduce a 'dc->vmsd' check to avoid segfault for --only-migratable
Posted by Ashijeet Acharya 7 years, 1 month ago
On Mon, Feb 13, 2017 at 11:34 PM, Ashijeet Acharya
<ashijeetacharya@gmail.com> wrote:
> 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'.
>
> Introduce a new function check_migratable() and move the
> only_migratable check inside it, also use stubs to avoid user-mode qemu
> build failures.
>
> Signed-off-by: Ashijeet Acharya <ashijeetacharya@gmail.com>
> ---
> Changes in v4:
> - introduce new check_migratable() function and use stubs
> 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                |  7 +++++++
>  hw/usb/bus.c                  | 19 -------------------
>  include/migration/migration.h |  3 +++
>  migration/migration.c         | 15 +++++++++++++++
>  qdev-monitor.c                |  9 ---------
>  stubs/vmstate.c               |  6 ++++++
>  6 files changed, 31 insertions(+), 28 deletions(-)
>

Just a small reminder about this patch, although I am not available
actively until this weekend due to exams.

Thanks
Ashijeet

Re: [Qemu-devel] [PATCH v4] migrate: Introduce a 'dc->vmsd' check to avoid segfault for --only-migratable
Posted by Dr. David Alan Gilbert 7 years, 1 month ago
* Ashijeet Acharya (ashijeetacharya@gmail.com) wrote:
> 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'.
> 
> Introduce a new function check_migratable() and move the
> only_migratable check inside it, also use stubs to avoid user-mode qemu
> build failures.
> 
> Signed-off-by: Ashijeet Acharya <ashijeetacharya@gmail.com>

Yep, I think that should work.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
> Changes in v4:
> - introduce new check_migratable() function and use stubs
> 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                |  7 +++++++
>  hw/usb/bus.c                  | 19 -------------------
>  include/migration/migration.h |  3 +++
>  migration/migration.c         | 15 +++++++++++++++
>  qdev-monitor.c                |  9 ---------
>  stubs/vmstate.c               |  6 ++++++
>  6 files changed, 31 insertions(+), 28 deletions(-)
> 
> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> index 5783442..4f49cfe 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;
> @@ -889,6 +890,7 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
>      Error *local_err = NULL;
>      bool unattached_parent = false;
>      static int unattached_count;
> +    int ret;
>  
>      if (dev->hotplugged && !dc->hotpluggable) {
>          error_setg(errp, QERR_DEVICE_NO_HOTPLUG, object_get_typename(obj));
> @@ -896,6 +898,11 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
>      }
>  
>      if (value && !dev->realized) {
> +        ret = check_migratable(obj, &local_err);
> +        if (ret < 0) {
> +            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/include/migration/migration.h b/include/migration/migration.h
> index af9135f..a6868cd 100644
> --- a/include/migration/migration.h
> +++ b/include/migration/migration.h
> @@ -22,6 +22,7 @@
>  #include "qapi-types.h"
>  #include "exec/cpu-common.h"
>  #include "qemu/coroutine_int.h"
> +#include "qom/object.h"
>  
>  #define QEMU_VM_FILE_MAGIC           0x5145564d
>  #define QEMU_VM_FILE_VERSION_COMPAT  0x00000002
> @@ -305,6 +306,8 @@ int migrate_add_blocker(Error *reason, Error **errp);
>   */
>  void migrate_del_blocker(Error *reason);
>  
> +int check_migratable(Object *obj, Error **err);
> +
>  bool migrate_postcopy_ram(void);
>  bool migrate_zero_blocks(void);
>  
> diff --git a/migration/migration.c b/migration/migration.c
> index 2766d2f..00b33f3 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -1146,6 +1146,21 @@ void migrate_del_blocker(Error *reason)
>      migration_blockers = g_slist_remove(migration_blockers, reason);
>  }
>  
> +int check_migratable(Object *obj, Error **err)
> +{
> +    DeviceClass *dc = DEVICE_GET_CLASS(obj);
> +    if (only_migratable && dc->vmsd) {
> +        if (dc->vmsd->unmigratable) {
> +            error_setg(err, "Device %s is not migratable, but "
> +                       "--only-migratable was specified",
> +                       object_get_typename(obj));
> +            return -1;
> +        }
> +    }
> +
> +    return 0;
> +}
> +
>  void qmp_migrate_incoming(const char *uri, Error **errp)
>  {
>      Error *local_err = NULL;
> 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) {
> diff --git a/stubs/vmstate.c b/stubs/vmstate.c
> index 6590627..5a71770 100644
> --- a/stubs/vmstate.c
> +++ b/stubs/vmstate.c
> @@ -1,6 +1,7 @@
>  #include "qemu/osdep.h"
>  #include "qemu-common.h"
>  #include "migration/vmstate.h"
> +#include "migration/migration.h"
>  
>  const VMStateDescription vmstate_dummy = {};
>  
> @@ -18,3 +19,8 @@ void vmstate_unregister(DeviceState *dev,
>                          void *opaque)
>  {
>  }
> +
> +int check_migratable(Object *obj, Error **err)
> +{
> +    return 0;
> +}
> -- 
> 2.6.2
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

Re: [Qemu-devel] [PATCH v4] migrate: Introduce a 'dc->vmsd' check to avoid segfault for --only-migratable
Posted by Dr. David Alan Gilbert 7 years ago
* Dr. David Alan Gilbert (dgilbert@redhat.com) wrote:
> * Ashijeet Acharya (ashijeetacharya@gmail.com) wrote:
> > 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'.
> > 
> > Introduce a new function check_migratable() and move the
> > only_migratable check inside it, also use stubs to avoid user-mode qemu
> > build failures.
> > 
> > Signed-off-by: Ashijeet Acharya <ashijeetacharya@gmail.com>
> 
> Yep, I think that should work.
> 
> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Queued.

> 
> > ---
> > Changes in v4:
> > - introduce new check_migratable() function and use stubs
> > 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                |  7 +++++++
> >  hw/usb/bus.c                  | 19 -------------------
> >  include/migration/migration.h |  3 +++
> >  migration/migration.c         | 15 +++++++++++++++
> >  qdev-monitor.c                |  9 ---------
> >  stubs/vmstate.c               |  6 ++++++
> >  6 files changed, 31 insertions(+), 28 deletions(-)
> > 
> > diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> > index 5783442..4f49cfe 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;
> > @@ -889,6 +890,7 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
> >      Error *local_err = NULL;
> >      bool unattached_parent = false;
> >      static int unattached_count;
> > +    int ret;
> >  
> >      if (dev->hotplugged && !dc->hotpluggable) {
> >          error_setg(errp, QERR_DEVICE_NO_HOTPLUG, object_get_typename(obj));
> > @@ -896,6 +898,11 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
> >      }
> >  
> >      if (value && !dev->realized) {
> > +        ret = check_migratable(obj, &local_err);
> > +        if (ret < 0) {
> > +            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/include/migration/migration.h b/include/migration/migration.h
> > index af9135f..a6868cd 100644
> > --- a/include/migration/migration.h
> > +++ b/include/migration/migration.h
> > @@ -22,6 +22,7 @@
> >  #include "qapi-types.h"
> >  #include "exec/cpu-common.h"
> >  #include "qemu/coroutine_int.h"
> > +#include "qom/object.h"
> >  
> >  #define QEMU_VM_FILE_MAGIC           0x5145564d
> >  #define QEMU_VM_FILE_VERSION_COMPAT  0x00000002
> > @@ -305,6 +306,8 @@ int migrate_add_blocker(Error *reason, Error **errp);
> >   */
> >  void migrate_del_blocker(Error *reason);
> >  
> > +int check_migratable(Object *obj, Error **err);
> > +
> >  bool migrate_postcopy_ram(void);
> >  bool migrate_zero_blocks(void);
> >  
> > diff --git a/migration/migration.c b/migration/migration.c
> > index 2766d2f..00b33f3 100644
> > --- a/migration/migration.c
> > +++ b/migration/migration.c
> > @@ -1146,6 +1146,21 @@ void migrate_del_blocker(Error *reason)
> >      migration_blockers = g_slist_remove(migration_blockers, reason);
> >  }
> >  
> > +int check_migratable(Object *obj, Error **err)
> > +{
> > +    DeviceClass *dc = DEVICE_GET_CLASS(obj);
> > +    if (only_migratable && dc->vmsd) {
> > +        if (dc->vmsd->unmigratable) {
> > +            error_setg(err, "Device %s is not migratable, but "
> > +                       "--only-migratable was specified",
> > +                       object_get_typename(obj));
> > +            return -1;
> > +        }
> > +    }
> > +
> > +    return 0;
> > +}
> > +
> >  void qmp_migrate_incoming(const char *uri, Error **errp)
> >  {
> >      Error *local_err = NULL;
> > 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) {
> > diff --git a/stubs/vmstate.c b/stubs/vmstate.c
> > index 6590627..5a71770 100644
> > --- a/stubs/vmstate.c
> > +++ b/stubs/vmstate.c
> > @@ -1,6 +1,7 @@
> >  #include "qemu/osdep.h"
> >  #include "qemu-common.h"
> >  #include "migration/vmstate.h"
> > +#include "migration/migration.h"
> >  
> >  const VMStateDescription vmstate_dummy = {};
> >  
> > @@ -18,3 +19,8 @@ void vmstate_unregister(DeviceState *dev,
> >                          void *opaque)
> >  {
> >  }
> > +
> > +int check_migratable(Object *obj, Error **err)
> > +{
> > +    return 0;
> > +}
> > -- 
> > 2.6.2
> > 
> --
> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK