On Wed, 25 Feb 2026 04:24:14 -0500, "Michael S. Tsirkin" <[email protected]> wrote: > 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.
So, does this mean we don't need to account for the case where NETDEV_RSS_KEY_LEN is 128, but the key_sz reported by the device is 64? Thanks. > > > > > Moreover, you should add a cover letter. > > > > Thanks. > > > > > > > > > > > > > } > > > > > > return 0; > > > -- > > > 2.25.1 > > > >
