Jason Wang
2021-Jun-29 04:03 UTC
[PATCH v8 09/10] vduse: Introduce VDUSE - vDPA Device in Userspace
? 2021/6/29 ??11:56, Yongji Xie ??:> On Tue, Jun 29, 2021 at 11:29 AM Jason Wang <jasowang at redhat.com> wrote: >> >> ? 2021/6/29 ??10:26, Yongji Xie ??: >>> On Mon, Jun 28, 2021 at 12:40 PM Jason Wang <jasowang at redhat.com> wrote: >>>> ? 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(). >>>> >>> 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. >> > OK, I see. If so, I prefer to only use noreply for set_status(). We do > not set the status bit if the message is failed. In this way, we don't > need to change lots of virtio core codes to handle the failure of > set_status()/get_status().It should work. Thanks> > Thanks, > Yongji >