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

[Yongji Xie]

On Mon, Jun 28, 2021 at 12:40 PM Jason Wang <jasowang@xxxxxxxxxx> wrote:
>
>
> 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().
>

We should not send messages to userspace in the FEATURES_OK case. So
the synchronization is not necessary.

Thanks,
Yongji