Re: [PATCH v2 15/17] vfio/migration: Multifd device state transfer support - receive side

["Cédric Le Goater" <clg@redhat.com>]

>>>>
>>>> -    return vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_RESUMING,
>>>> - vbasedev->migration->device_state, errp);
>>>> +    migration->load_bufs_thread_finished = false;
>>>> +    migration->load_bufs_thread_want_exit = false;
>>>> +    qemu_thread_create(&migration->load_bufs_thread, "vfio-load-bufs",
>>>> +                       vfio_load_bufs_thread, opaque, QEMU_THREAD_JOINABLE);
>>>
>>> The device state save threads are manged by migration core thread pool. Don't we want to apply the same thread management scheme for the load flow as well?
>>
>> I think that (in contrast with the device state saving threads)
>> the buffer loading / reordering thread is an implementation detail
>> of the VFIO driver, so I don't think it really makes sense for multifd code
>> to manage it.

Is it an optimisation then ? In that case, could the implementation not
use threads ?

VFIO is complex, migration is complex, VFIO migration is even more. TBH,
the idea of doing thread management in the VFIO subsystem makes me feel
uncomfortable.

Thanks,

C.