Virtualization - Jun 2021 - [PATCH v8 09/10] vduse: Introduce VDUSE - vDPA Device in Userspace

? 2021/6/25 ??12:19, Yongji Xie ??:
>> 2b) for set_status(): simply relay the message to userspace, reply is
no
>> needed. Userspace will use a command to update the status when the
>> datapath is stop. The the status could be fetched via get_stats().
>>
>> 2b looks more spec complaint.
>>
> Looks good to me. And I think we can use the reply of the message to
> update the status instead of introducing a new command.
>
Just notice this part in virtio_finalize_features():

 ??????? virtio_add_status(dev, VIRTIO_CONFIG_S_FEATURES_OK);
 ??????? status = dev->config->get_status(dev);
 ??????? if (!(status & VIRTIO_CONFIG_S_FEATURES_OK)) {

So we no reply doesn't work for FEATURES_OK.

So my understanding is:

1) We must not use noreply for set_status()
2) We can use noreply for get_status(), but it requires a new ioctl to 
update the status.

So it looks to me we need synchronize for both get_status() and 
set_status().

Thanks