> On Jan 25, 2022, at 5:27 AM, Stefan Hajnoczi <stefa...@redhat.com> wrote:
>
> On Wed, Jan 19, 2022 at 04:41:54PM -0500, Jagannathan Raman wrote:
>> Signed-off-by: Elena Ufimtseva <elena.ufimts...@oracle.com>
>> Signed-off-by: John G Johnson <john.g.john...@oracle.com>
>> Signed-off-by: Jagannathan Raman <jag.ra...@oracle.com>
>> ---
>> include/hw/qdev-core.h | 5 +++++
>> softmmu/qdev-monitor.c | 35 +++++++++++++++++++++++++++++++++++
>> 2 files changed, 40 insertions(+)
>>
>> diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
>> index eed2983072..67df5e0081 100644
>> --- a/include/hw/qdev-core.h
>> +++ b/include/hw/qdev-core.h
>> @@ -193,6 +193,7 @@ struct DeviceState {
>> int instance_id_alias;
>> int alias_required_for_version;
>> ResettableState reset;
>> + GSList *unplug_blockers;
>> };
>>
>> struct DeviceListener {
>> @@ -433,6 +434,10 @@ typedef bool (QDevPutBusFunc)(BusState *bus, Error
>> **errp);
>> bool qdev_set_bus_cbs(QDevGetBusFunc *get_bus, QDevPutBusFunc *put_bus,
>> Error **errp);
>>
>> +int qdev_add_unplug_blocker(DeviceState *dev, Error *reason, Error **errp);
>> +void qdev_del_unplug_blocker(DeviceState *dev, Error *reason);
>> +bool qdev_unplug_blocked(DeviceState *dev, Error **errp);
>> +
>> /**
>> * GpioPolarity: Polarity of a GPIO line
>> *
>> diff --git a/softmmu/qdev-monitor.c b/softmmu/qdev-monitor.c
>> index 7306074019..1a169f89a2 100644
>> --- a/softmmu/qdev-monitor.c
>> +++ b/softmmu/qdev-monitor.c
>> @@ -978,10 +978,45 @@ void qmp_device_del(const char *id, Error **errp)
>> return;
>> }
>>
>> + if (qdev_unplug_blocked(dev, errp)) {
>> + return;
>> + }
>> +
>> qdev_unplug(dev, errp);
>> }
>> }
>>
>> +int qdev_add_unplug_blocker(DeviceState *dev, Error *reason, Error **errp)
>> +{
>> + ERRP_GUARD();
>> +
>> + if (!migration_is_idle()) {
>> + error_setg(errp, "migration is in progress");
>> + return -EBUSY;
>> + }
>
> Why can this function not be called during migration?
Since ‘unplug_blockers' is a member of the device, I thought it wouldn’t be
correct to
allow changes to the device's state during migration.
I did weigh the following reasons against adding this check:
- unplug_blockers is not migrated to the destination anyway, so it doesn’t
matter if
it changes after migration starts
- whichever code/object that needs to add the blocker could add it at the
destination
if needed
However, unlike qmp_device_add(), qmp_object_add() doesn’t reject during
migration. As such, an object could add a blocker for the device when migration
is
in progress.
Would you prefer to throw a warning, or fully remove this test?
--
Jag
>
>> +
>> + dev->unplug_blockers = g_slist_prepend(dev->unplug_blockers, reason);
>> +
>> + return 0;
>> +}
>> +
>> +void qdev_del_unplug_blocker(DeviceState *dev, Error *reason)
>> +{
>> + dev->unplug_blockers = g_slist_remove(dev->unplug_blockers, reason);
>> +}
>> +
>> +bool qdev_unplug_blocked(DeviceState *dev, Error **errp)
>> +{
>> + ERRP_GUARD();
>> +
>> + if (dev->unplug_blockers) {
>> + error_propagate(errp, error_copy(dev->unplug_blockers->data));
>> + return true;
>> + }
>> +
>> + return false;
>> +}
>> +
>> void hmp_device_add(Monitor *mon, const QDict *qdict)
>> {
>> Error *err = NULL;
>> --
>> 2.20.1
>>
