On Wed, Oct 12, 2016 at 06:01:25PM +0200, Olivier MATZ wrote:
> Hello Yuanhan,
>
> On 10/12/2016 04:41 PM, Yuanhan Liu wrote:
> >On Mon, Oct 03, 2016 at 11:00:14AM +0200, Olivier Matz wrote:
> >>@@ -1344,6 +1347,7 @@ virtio_dev_configure(struct rte_eth_dev *dev)
> >> {
> >> const struct rte_eth_rxmode *rxmode = &dev->data->dev_conf.rxmode;
> >> struct virtio_hw *hw = dev->data->dev_private;
> >>+ uint64_t req_features;
> >> int ret;
> >>
> >> PMD_INIT_LOG(DEBUG, "configure");
> >>@@ -1353,6 +1357,14 @@ virtio_dev_configure(struct rte_eth_dev *dev)
> >> return -EINVAL;
> >> }
> >>
> >>+ req_features = VIRTIO_PMD_GUEST_FEATURES;
> >>+ /* if request features changed, reinit the device */
> >>+ if (req_features != hw->req_guest_features) {
> >>+ ret = virtio_init_device(dev, req_features);
> >>+ if (ret < 0)
> >>+ return ret;
> >>+ }
> >
> >Why do you have to reset virtio here? This doesn't make too much sense
> >to me.
> >
> >IIUC, you want to make sure those TSO related features being unset at
> >init time, and enable it (by doing reset) when it's asked to be enabled
> >(by rte_eth_dev_configure)?
> >
> >Why not always setting those features? We could do the actual offloads
> >when:
> >
> >- those features have been negoiated
> >
> >- they are enabled through rte_eth_dev_configure
> >
> >With that, I think we could avoid the reset here?
>
> It would work for TX, since you decide to use or not the feature. But I
> think this won't work for RX: if you negociate LRO at init, the host may
> send you large packets, even if LRO is disabled in dev_configure.
I see. Thanks.
Besides, I think you should return error when LRO is not negoiated
after the reset (say, when it's disabled through qemu command line)?
--yliu
