On Thu, Oct 20, 2016 at 10:37:20PM -0400, Jarod Wilson wrote:
> On Thu, Oct 20, 2016 at 11:23:54PM +0300, Michael S. Tsirkin wrote:
> > On Thu, Oct 20, 2016 at 01:55:21PM -0400, Jarod Wilson wrote:
> ...
> > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > index fad84f3..720809f 100644
> > > --- a/drivers/net/virtio_net.c
> > > +++ b/drivers/net/virtio_net.c
> > > @@ -1419,17 +1419,6 @@ static const struct ethtool_ops virtnet_ethtool_ops = {
> > > .set_settings = virtnet_set_settings,
> > > };
> > >
> > > -#define MIN_MTU 68
> > > -#define MAX_MTU 65535
> > > -
> > > -static int virtnet_change_mtu(struct net_device *dev, int new_mtu)
> > > -{
> > > - if (new_mtu < MIN_MTU || new_mtu > MAX_MTU)
> > > - return -EINVAL;
> > > - dev->mtu = new_mtu;
> > > - return 0;
> > > -}
> > > -
> > > static const struct net_device_ops virtnet_netdev = {
> > > .ndo_open = virtnet_open,
> > > .ndo_stop = virtnet_close,
> > > @@ -1437,7 +1426,6 @@ static const struct net_device_ops virtnet_netdev = {
> > > .ndo_validate_addr = eth_validate_addr,
> > > .ndo_set_mac_address = virtnet_set_mac_address,
> > > .ndo_set_rx_mode = virtnet_set_rx_mode,
> > > - .ndo_change_mtu = virtnet_change_mtu,
> > > .ndo_get_stats64 = virtnet_stats,
> > > .ndo_vlan_rx_add_vid = virtnet_vlan_rx_add_vid,
> > > .ndo_vlan_rx_kill_vid = virtnet_vlan_rx_kill_vid,
> > > @@ -1748,6 +1736,9 @@ static bool virtnet_validate_features(struct virtio_device *vdev)
> > > return true;
> > > }
> > >
> > > +#define MIN_MTU ETH_MIN_MTU
> > > +#define MAX_MTU ETH_MAX_MTU
> > > +
> >
> > Can we drop these btw?
>
> Bah. Yeah. Should have just used them directly. I didn't add ETH_MAX_MTU
> until after doing the virtio_net changes, so I missed that.
>
> > > static int virtnet_probe(struct virtio_device *vdev)
> > > {
> > > int i, err;
> > > @@ -1821,6 +1812,10 @@ static int virtnet_probe(struct virtio_device *vdev)
> > >
> > > dev->vlan_features = dev->features;
> > >
> > > + /* MTU range: 68 - 65535 */
> > > + dev->min_mtu = MIN_MTU;
> > > + dev->max_mtu = MAX_MTU;
> > > +
> > > /* Configuration may specify what MAC to use. Otherwise random. */
> > > if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC))
> > > virtio_cread_bytes(vdev,
> > > @@ -1875,8 +1870,10 @@ static int virtnet_probe(struct virtio_device *vdev)
> > > mtu = virtio_cread16(vdev,
> > > offsetof(struct virtio_net_config,
> > > mtu));
> > > - if (virtnet_change_mtu(dev, mtu))
> > > + if (mtu < dev->min_mtu || mtu > dev->max_mtu)
> >
> > In fact the > max_mtu branch does not make sense since a 16 bit
> > value can't exceed MAX_MTU.
>
> Hm. mtu is declared as an int, not sure if there's any sort of type
> promotion to be worried about (not an area I know much/anything about).
Not by design, that's for sure.
> Certainly something that could be looked into as a minor optimization,
> though it's only in a probe path and shouldn't hurt anything, so ... meh?
Right. Aaron said he's working on a patch that essentially does
dev->max_mtu = mtu after validation, so this part will look
a bit silly there.
> --
> Jarod Wilson
> jarod@xxxxxxxxxx
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