在 2021/6/29 上午10:26, Yongji Xie 写道:
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.
As discussed previously, there could be a device that mandates some
features (VIRTIO_F_RING_PACKED). So it can choose to not accept
FEATURES_OK is packed virtqueue is not negotiated.
In this case we need to relay the message to userspace.
Thanks
Thanks,
Yongji
