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

[Jason Wang]

在 2021/6/25 下午12:19, Yongji Xie 写道:
> > 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