Re: [PATCH 1/3] qapi/vfio: Add VFIO device migration state change QAPI event

[Markus Armbruster <armbru@redhat.com>]

Avihai Horon <avihaih@nvidia.com> writes:

> On 06/05/2024 7:52, Markus Armbruster wrote:
>> Avihai Horon <avihaih@nvidia.com> writes:
>>
>>> On 01/05/2024 14:50, Joao Martins wrote:
>>>> On 30/04/2024 06:16, Avihai Horon wrote:
>>>>> Add a new QAPI event for VFIO device migration state change. This event
>>>>> will be emitted when a VFIO device changes its migration state, for
>>>>> example, during migration or when stopping/starting the guest.
>>>>>
>>>>> This event can be used by management applications to get updates on the
>>>>> current state of the VFIO device for their own purposes.
>>>>>
>>>>> Signed-off-by: Avihai Horon <avihaih@nvidia.com>

[...]

>>>>> diff --git a/qapi/vfio.json b/qapi/vfio.json
>>>>> new file mode 100644
>>>>> index 0000000000..a38f26bccd
>>>>> --- /dev/null
>>>>> +++ b/qapi/vfio.json
>>>>> @@ -0,0 +1,61 @@
>>>>> +# -*- Mode: Python -*-
>>>>> +# vim: filetype=python
>>>>> +#
>>>>> +
>>>>> +##
>>>>> +# = VFIO devices
>>>>> +##
>>>>> +
>>>>> +##
>>>>> +# @VFIODeviceMigState:
>>>>> +#
>>>>> +# An enumeration of the VFIO device migration states.
>>>>> +#
>>>>> +# @stop: The device is stopped.
>>>>> +#
>>>>> +# @running: The device is running.
>>>>> +#
>>>>> +# @stop-copy: The device is stopped and its internal state is available
>>>>> +#     for reading.
>>>>> +#
>>>>> +# @resuming: The device is stopped and its internal state is available
>>>>> +#     for writing.
>>>>> +#
>>>>> +# @running-p2p: The device is running in the P2P quiescent state.
>>>>> +#
>>>>> +# @pre-copy: The device is running, tracking its internal state and its
>>>>> +#     internal state is available for reading.
>>>>> +#
>>>>> +# @pre-copy-p2p: The device is running in the P2P quiescent state,
>>>>> +#     tracking its internal state and its internal state is available
>>>>> +#     for reading.
>>>>> +#
>>>>> +# Since: 9.1
>>>>> +##
>>>>> +{ 'enum': 'VFIODeviceMigState',
>>>>> +  'data': [ 'stop', 'running', 'stop-copy', 'resuming', 'running-p2p',
>>>>> +            'pre-copy', 'pre-copy-p2p' ],
>>>>> +  'prefix': 'QAPI_VFIO_DEVICE_MIG_STATE' }
>>
>> Without 'prefix', you get VFIO_DEVICE_MIG_STATE_STOP and so forth.  Why
>> do you need a QAPI_ prefix?
>
> VFIO uAPI already defines enum vfio_device_mig_state and its values 
> VFIO_DEVICE_STATE_STOP, VFIO_DEVICE_STATE_RUNNING, etc.
>
> I wanted to emphasize these are QAPI entities.

I see.

>>>>> +
>>>> Considering MIG can also be interpreted as Multi Instance GPU elsewhere
>>>> unrelated to this shouldn't we be explicit here? i.e.
>>>>
>>>>           VFIO_DEVICE_MIGRATION_STATE
>>>>
>>>> ... to avoid ambiguiosity.
>>>
>>> I used mig to avoid long names, but I don't mind changing it to migration if that's clearer.
>>>
>>> Thanks.
>>
>> We generally avoid abbreviations in QAPI/QMP.
>>
>> The event that reports general migration state change is called
>> MIGRATION, and its data type MigrationStatus.
>>
>> We could call this one VFIO_MIGRATION, and its data type
>> VfioMigrationStatus.
>
> Sounds good, but how about VFIOMigrationState (I'd like it to relate to 
> the VFIO state)?

No objection to "State" instead of "Status" then.

On VFIO vs. Vfio: several existing type names start with Vfio.

[...]