From: Jianjun Duan <du...@linux.vnet.ibm.com>
Currently migrated Devices are identified with an idstr which is
calculated automatically using their path in the QOM composition
tree. In some cases these Devices may have a more reliable
identifier that may be preferable in situations where there's a
chance their path in the composition tree might change in the
future as a resulting of changes in how the device is modeled
in QEMU.
One such Device is the "spapr-dr-connector" used to handle hotplug
for various resources on pseries machine types, where the PAPR
specification mandates that each DRC have a 32-bit globally unique
identifier associated with it. As such, this identifier is also ideal
as a reliable way to identify a particular DRC in the migration
stream, so we introduce support here for using a caller-side supplied
instance_id for Devices in preparation for that.
register_savevm_live() and vmstate_register_with_alias_id() already
provide a means to let the caller supply an instance_id instead of
relying on the migration subsystem to generate one automatically,
but in cases where we're registering SaveVMHandlers or VMSDs
(respectively) that are associated with a Device, the instance_id is
ignored in favor of a string identifier based solely on the QOM path.
This patch generalizes this so that an instance_id can also be
supplied by the caller for Devices. Since VMSD registration for
Devices is generally handled automatically by qdev, we also introduce
a DeviceClass->dev_get_instance_id() method that, when set, is called
by qdev to obtain the corresponding instance_id that should be used
for a particular Device. Otherwise we maintain the original behavior
of passing instance_id == -1 and thus falling back to the previous
logic of using the QOM path.
Signed-off-by: Jianjun Duan <du...@linux.vnet.ibm.com>
* moved usage of DeviceClass->dev_get_instance_id() out of savevm.c
and into caller (qdev) instead
* clarified usage/intent in comments and commit msg
Signed-off-by: Michael Roth <mdr...@linux.vnet.ibm.com>
---
hw/core/qdev.c | 6 +++++-
include/hw/qdev-core.h | 9 +++++++++
migration/savevm.c | 4 ++--
3 files changed, 16 insertions(+), 3 deletions(-)
diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index 5783442..c8c0c44 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -933,7 +933,11 @@ static void device_set_realized(Object *obj, bool value,
Error **errp)
}
if (qdev_get_vmsd(dev)) {
- vmstate_register_with_alias_id(dev, -1, qdev_get_vmsd(dev), dev,
+ int instance_id = DEVICE_GET_CLASS(dev)->dev_get_instance_id
+ ? DEVICE_GET_CLASS(dev)->dev_get_instance_id(dev)
+ : -1;
+
+ vmstate_register_with_alias_id(dev, instance_id,
qdev_get_vmsd(dev), dev,
dev->instance_id_alias,
dev->alias_required_for_version);
}
diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
index 2c97347..8ba82af 100644
--- a/include/hw/qdev-core.h
+++ b/include/hw/qdev-core.h
@@ -139,6 +139,15 @@ typedef struct DeviceClass {
qdev_initfn init; /* TODO remove, once users are converted to realize */
qdev_event exit; /* TODO remove, once users are converted to unrealize */
const char *bus_type;
+
+ /* When this field is set, instead of using the device's QOM path,
+ * SaveStateEntry's for devices will be identified using a combination
+ * of the corresponding VMSD name and an instance_id returned by this
+ * function. This should only be necessary for situations where the
+ * QOM path is anticipated to change and a more stable identifier is
+ * desired to identify a device in the migration stream.
+ */
+ int (*dev_get_instance_id)(DeviceState *dev);
} DeviceClass;
typedef struct NamedGPIOList NamedGPIOList;
diff --git a/migration/savevm.c b/migration/savevm.c
index 0363372..a95fff9 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -556,7 +556,7 @@ int register_savevm_live(DeviceState *dev,
se->is_ram = 1;
}
- if (dev) {
+ if (dev && instance_id == -1) {
char *id = qdev_get_dev_path(dev);
if (id) {
pstrcpy(se->idstr, sizeof(se->idstr), id);
@@ -640,7 +640,7 @@ int vmstate_register_with_alias_id(DeviceState *dev, int
instance_id,
se->vmsd = vmsd;
se->alias_id = alias_id;
- if (dev) {
+ if (dev && instance_id == -1) {
char *id = qdev_get_dev_path(dev);
if (id) {
pstrcpy(se->idstr, sizeof(se->idstr), id);
--
1.9.1
