Re: [PATCH 1/2] qapi/run-state: Add a new shutdown cause 'migration-completed'

[Kunkun Jiang <jiangkunkun@huawei.com>]

Hi Daniel,

On 2021/7/5 20:48, Daniel P. Berrangé wrote:
> On Mon, Jul 05, 2021 at 08:36:52PM +0800, Kunkun Jiang wrote:
>> In the current version, the source QEMU process does not automatic
>> exit after a successful migration. Additional action is required,
>> such as sending { "execute": "quit" } or ctrl+c. For simplify, add
>> a new shutdown cause 'migration-completed' to exit the source QEMU
>> process after a successful migration.
> IIUC, 'STATUS_COMPLETED' state is entered on the source host
> once it has finished sending all VM state, and thus does not
> guarantee that the target host has successfully received and
> loaded all VM state.
Thanks for your reply.

If the target host doesn't successfully receive and load all VM state,
we can send { "execute": "cont" } to resume the soruce in time to
ensure that VM will not lost?
> Typically a mgmt app will need to directly confirm that the
> target host QEMU has succesfully started running, before it
> will tell the source QEMU to quit.
'a mgmt app', such as libvirt?

Thanks,
Kunkun Jiang
> So, AFAICT, this automatic exit after STATUS_COMPLETED is
> not safe and could lead to total loss of the running VM in
> error scenarios.
>
>
>
>> Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com>
>> ---
>>   migration/migration.c | 1 +
>>   qapi/run-state.json   | 4 +++-
>>   2 files changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/migration/migration.c b/migration/migration.c
>> index 4228635d18..16782c93c2 100644
>> --- a/migration/migration.c
>> +++ b/migration/migration.c
>> @@ -3539,6 +3539,7 @@ static void migration_iteration_finish(MigrationState *s)
>>       case MIGRATION_STATUS_COMPLETED:
>>           migration_calculate_complete(s);
>>           runstate_set(RUN_STATE_POSTMIGRATE);
>> +        qemu_system_shutdown_request(SHUTDOWN_CAUSE_MIGRATION_COMPLETED);
>>           break;
>>   
>>       case MIGRATION_STATUS_ACTIVE:
>> diff --git a/qapi/run-state.json b/qapi/run-state.json
>> index 43d66d700f..66aaef4e2b 100644
>> --- a/qapi/run-state.json
>> +++ b/qapi/run-state.json
>> @@ -86,12 +86,14 @@
>>   #                   ignores --no-reboot. This is useful for sanitizing
>>   #                   hypercalls on s390 that are used during kexec/kdump/boot
>>   #
>> +# @migration-completed: Reaction to the successful migration
>> +#
>>   ##
>>   { 'enum': 'ShutdownCause',
>>     # Beware, shutdown_caused_by_guest() depends on enumeration order
>>     'data': [ 'none', 'host-error', 'host-qmp-quit', 'host-qmp-system-reset',
>>               'host-signal', 'host-ui', 'guest-shutdown', 'guest-reset',
>> -            'guest-panic', 'subsystem-reset'] }
>> +            'guest-panic', 'subsystem-reset', 'migration-completed'] }
>>   
>>   ##
>>   # @StatusInfo:
>> -- 
>> 2.23.0
>>
>>
> Regards,
> Daniel