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[Qemu-devel] [PATCH 3/6] vmstate: Add support for alias ID


From: Jan Kiszka
Subject: [Qemu-devel] [PATCH 3/6] vmstate: Add support for alias ID
Date: Wed, 12 May 2010 23:19:10 +0200

From: Jan Kiszka <address@hidden>

Some legacy users (mostly PC devices) of vmstate_register manage
instance IDs on their own, and that unfortunately in a way that is
incompatible with automatically generated ones. This so far prevents
switching those users to vmstates that are registered by qdev.

To establish a migration path, this patch introduces the concept of
alias IDs. They can be passed to an extended vmstate registration
service, and qdev provides a set service to be used during device init.
find_se will consider the alias in addition to the default ID. We can
then start generating the default ID automatically and writing it on
vmsave, thus converting that format without breaking support for upward
migration.

Signed-off-by: Jan Kiszka <address@hidden>
---
 hw/hw.h   |    3 +++
 hw/qdev.c |   13 +++++++++++--
 hw/qdev.h |    2 ++
 savevm.c  |   16 +++++++++++++---
 4 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/hw/hw.h b/hw/hw.h
index 2d39724..d124716 100644
--- a/hw/hw.h
+++ b/hw/hw.h
@@ -758,5 +758,8 @@ extern void vmstate_save_state(QEMUFile *f, const 
VMStateDescription *vmsd,
                                void *opaque);
 extern int vmstate_register(int instance_id, const VMStateDescription *vmsd,
                             void *base);
+extern int vmstate_register_with_alias_id(int instance_id,
+                                          const VMStateDescription *vmsd,
+                                          void *base, int alias_id);
 void vmstate_unregister(const VMStateDescription *vmsd, void *opaque);
 #endif
diff --git a/hw/qdev.c b/hw/qdev.c
index d3bf0fa..445d4d7 100644
--- a/hw/qdev.c
+++ b/hw/qdev.c
@@ -93,6 +93,7 @@ static DeviceState *qdev_create_from_info(BusState *bus, 
DeviceInfo *info)
         assert(bus->allow_hotplug);
         dev->hotplugged = 1;
     }
+    dev->instance_id_alias = -1;
     dev->state = DEV_STATE_CREATED;
     return dev;
 }
@@ -278,12 +279,20 @@ int qdev_init(DeviceState *dev)
         return rc;
     }
     qemu_register_reset(qdev_reset, dev);
-    if (dev->info->vmsd)
-        vmstate_register(-1, dev->info->vmsd, dev);
+    if (dev->info->vmsd) {
+        vmstate_register_with_alias_id(-1, dev->info->vmsd, dev,
+                                       dev->instance_id_alias);
+    }
     dev->state = DEV_STATE_INITIALIZED;
     return 0;
 }
 
+void qdev_set_instance_id_alias(DeviceState *dev, int alias_id)
+{
+    assert(dev->state == DEV_STATE_CREATED);
+    dev->instance_id_alias = alias_id;
+}
+
 int qdev_unplug(DeviceState *dev)
 {
     if (!dev->parent_bus->allow_hotplug) {
diff --git a/hw/qdev.h b/hw/qdev.h
index d8fbc73..b7dbee4 100644
--- a/hw/qdev.h
+++ b/hw/qdev.h
@@ -44,6 +44,7 @@ struct DeviceState {
     QLIST_HEAD(, BusState) child_bus;
     int num_child_bus;
     QLIST_ENTRY(DeviceState) sibling;
+    int instance_id_alias;
 };
 
 typedef void (*bus_dev_printfn)(Monitor *mon, DeviceState *dev, int indent);
@@ -112,6 +113,7 @@ int qdev_device_help(QemuOpts *opts);
 DeviceState *qdev_device_add(QemuOpts *opts);
 int qdev_init(DeviceState *dev) QEMU_WARN_UNUSED_RESULT;
 void qdev_init_nofail(DeviceState *dev);
+void qdev_set_instance_id_alias(DeviceState *dev, int alias_id);
 int qdev_unplug(DeviceState *dev);
 void qdev_free(DeviceState *dev);
 int qdev_simple_unplug_cb(DeviceState *dev);
diff --git a/savevm.c b/savevm.c
index 74e553c..f155582 100644
--- a/savevm.c
+++ b/savevm.c
@@ -991,6 +991,7 @@ typedef struct SaveStateEntry {
     QTAILQ_ENTRY(SaveStateEntry) entry;
     char idstr[256];
     int instance_id;
+    int alias_id;
     int version_id;
     int section_id;
     SaveSetParamsHandler *set_params;
@@ -1079,8 +1080,9 @@ void unregister_savevm(const char *idstr, void *opaque)
     }
 }
 
-int vmstate_register(int instance_id, const VMStateDescription *vmsd,
-                     void *opaque)
+int vmstate_register_with_alias_id(int instance_id,
+                                   const VMStateDescription *vmsd,
+                                   void *opaque, int alias_id)
 {
     SaveStateEntry *se;
 
@@ -1093,6 +1095,7 @@ int vmstate_register(int instance_id, const 
VMStateDescription *vmsd,
     se->load_state = NULL;
     se->opaque = opaque;
     se->vmsd = vmsd;
+    se->alias_id = alias_id;
 
     if (instance_id == -1) {
         se->instance_id = calculate_new_instance_id(vmsd->name);
@@ -1104,6 +1107,12 @@ int vmstate_register(int instance_id, const 
VMStateDescription *vmsd,
     return 0;
 }
 
+int vmstate_register(int instance_id, const VMStateDescription *vmsd,
+                     void *opaque)
+{
+    return vmstate_register_with_alias_id(instance_id, vmsd, opaque, -1);
+}
+
 void vmstate_unregister(const VMStateDescription *vmsd, void *opaque)
 {
     SaveStateEntry *se, *new_se;
@@ -1433,7 +1442,8 @@ static SaveStateEntry *find_se(const char *idstr, int 
instance_id)
 
     QTAILQ_FOREACH(se, &savevm_handlers, entry) {
         if (!strcmp(se->idstr, idstr) &&
-            instance_id == se->instance_id)
+            (instance_id == se->instance_id ||
+             instance_id == se->alias_id))
             return se;
     }
     return NULL;
-- 
1.6.0.2




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