On Wed, Feb 25, 2026 at 05:11:42PM +0800, Xuan Zhuo wrote: > On Tue, 24 Feb 2026 12:28:50 +0530, Srujana Challa <[email protected]> > wrote: > > Since NETDEV_RSS_KEY_LEN was increased to 256 in net-next, use > > BUILD_BUG_ON to enforce the limit at compile time and remove the > > redundant runtime max check. > > > > Signed-off-by: Srujana Challa <[email protected]> > > --- > > drivers/net/virtio_net.c | 8 +------- > > 1 file changed, 1 insertion(+), 7 deletions(-) > > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > > index eeefe8abc122..768ad5523dfa 100644 > > --- a/drivers/net/virtio_net.c > > +++ b/drivers/net/virtio_net.c > > @@ -6639,13 +6639,7 @@ static int virtnet_validate(struct virtio_device > > *vdev) > > __virtio_clear_bit(vdev, VIRTIO_NET_F_RSS); > > __virtio_clear_bit(vdev, VIRTIO_NET_F_HASH_REPORT); > > } > > - if (key_sz > NETDEV_RSS_KEY_LEN) { > > - dev_warn(&vdev->dev, > > - "rss_max_key_size=%u exceeds driver limit %u, > > disabling RSS\n", > > - key_sz, NETDEV_RSS_KEY_LEN); > > - __virtio_clear_bit(vdev, VIRTIO_NET_F_RSS); > > - __virtio_clear_bit(vdev, VIRTIO_NET_F_HASH_REPORT); > > - } > > + BUILD_BUG_ON(type_max(key_sz) >= NETDEV_RSS_KEY_LEN); > > Do we really need this check? > > If I understand correctly, the intention is to cap key_sz at 256. However, > since > key_sz is of type u8, its maximum value is inherently 255, making this check > redundant. This is not only limited by this kernel code, the virtio-net spec > defines this.
That's why it's BUILD_BUG_ON. It checks it has the right type. We never *need* BUILD_BUG_ON by definition, what this does is document the assumption. > Moreover, if NETDEV_RSS_KEY_LEN is ever reduced to a value smaller than 256 in > the future, this check would no longer enforce the intended limit correctly. then it would fail build. > > Moreover, you should add a cover letter. > > Thanks. > > > > > > > } > > > > return 0; > > -- > > 2.25.1 > >
