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

On Mon, Jun 28, 2021 at 12:40 PM Jason Wang [off-list ref] wrote:

在 2021/6/25 下午12:19, Yongji Xie 写道:

quoted

quoted

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