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vmstate: Add support for alias ID

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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.

The user is required specify the highest vmstate version for which the
alias is required. Once this version falls behind the minimum required
for a specific vmstate, an assertion triggers to motivate cleaning up
the obsolete alias.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
This commit is contained in:
Jan Kiszka 2010-05-15 13:32:40 +02:00 committed by Blue Swirl
parent ec86f3e1af
commit 4d2ffa08b6
4 changed files with 39 additions and 5 deletions
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4
hw/hw.h
View File

@ -758,5 +758,9 @@ 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,
int required_for_version);
void vmstate_unregister(const VMStateDescription *vmsd, void *opaque);
#endif

16
hw/qdev.c
View File

@ -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 +279,23 @@ 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->alias_required_for_version);
}
dev->state = DEV_STATE_INITIALIZED;
return 0;
}
void qdev_set_legacy_instance_id(DeviceState *dev, int alias_id,
int required_for_version)
{
assert(dev->state == DEV_STATE_CREATED);
dev->instance_id_alias = alias_id;
dev->alias_required_for_version = required_for_version;
}
int qdev_unplug(DeviceState *dev)
{
if (!dev->parent_bus->allow_hotplug) {

4
hw/qdev.h
View File

@ -44,6 +44,8 @@ struct DeviceState {
QLIST_HEAD(, BusState) child_bus;
int num_child_bus;
QLIST_ENTRY(DeviceState) sibling;
int instance_id_alias;
int alias_required_for_version;
};
typedef void (*bus_dev_printfn)(Monitor *mon, DeviceState *dev, int indent);
@ -112,6 +114,8 @@ 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_legacy_instance_id(DeviceState *dev, int alias_id,
int required_for_version);
int qdev_unplug(DeviceState *dev);
void qdev_free(DeviceState *dev);
int qdev_simple_unplug_cb(DeviceState *dev);

20
savevm.c
View File

@ -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;
@ -1079,11 +1080,16 @@ 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,
int required_for_version)
{
SaveStateEntry *se;
/* If this triggers, alias support can be dropped for the vmsd. */
assert(alias_id == -1 || required_for_version >= vmsd->minimum_version_id);
se = qemu_mallocz(sizeof(SaveStateEntry));
pstrcpy(se->idstr, sizeof(se->idstr), vmsd->name);
se->version_id = vmsd->version_id;
@ -1093,6 +1099,7 @@ 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 +1111,12 @@ 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, 0);
}
void vmstate_unregister(const VMStateDescription *vmsd, void *opaque)
{
SaveStateEntry *se, *new_se;
@ -1433,7 +1446,8 @@ 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;