> On Wed, Feb 11, 2026 at 07:44:54AM +0000, Srujana Challa wrote:
> > > On Fri, Feb 06, 2026 at 07:13:08PM -0800, Jakub Kicinski wrote:
> > > > On Fri, 6 Feb 2026 17:31:54 +0530 Srujana Challa wrote:
> > > > > Replace hardcoded RSS max key size limit with NETDEV_RSS_KEY_LEN
> > > > > to align with kernel's standard RSS key length. Add validation
> > > > > for RSS key size against spec minimum (40 bytes) and driver
> > > > > maximum. When validation fails, gracefully disable RSS features
> > > > > and continue initialization rather than failing completely.
> > > >
> > > > Hm, FWIW clang says:
> > > >
> > > > drivers/net/virtio_net.c:6841:31: warning: result of comparison of
> > > > constant
> > > 256 with expression of type 'u8' (aka 'unsigned char') is always
> > > false [- Wtautological-constant-out-of-range-compare]
> > > > 6841 | } else if (vi->rss_key_size >
> VIRTIO_NET_RSS_MAX_KEY_SIZE)
> > > {
> > > > | ~~~~~~~~~~~~~~~~ ^
> > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > >
> > > > Which is kinda annoying because the value was increased in net-next.
> > > > If Machael wants this backported then we need to keep the check
> > > > and follow up in net-next? We could try to cast the u32 away but
> > > > that feels dirty..
> > >
> > >
> > > I'd say yes. the warning is harmless.
> > > so
> > > patch 1 - this code
> > > patch 2 - replace with BUILD_BUG_ON
> > >
> > > but i ask then whether this code was actually tested against net-next.
> > Yes, tested against net-next (before NETDEV_RSS_KEY_LEN was changed to
> 256).
> > BUILD_BUG_ON would always fail as-is on net-next since rss_key_size is u8.
>
> BUILD_BUG_ON(type_max(vi->rss_key_size) >=
> VIRTIO_NET_RSS_MAX_KEY_SIZE)
>
> why would it fail?
I was assuming BUILD_BUG_ON was intended to catch the type mismatch
(when VIRTIO_NET_RSS_MAX_KEY_SIZE exceeds what u8 can hold). I understand
now - thanks for clarifying!
>
>
> > Can we cast the comparison to u32 instead?
> > Thanks!
> >
> > >
> > > --
> > > MST
> >
>
> forcing compiler to generate code where we do not need any really seems silly.
>
> --
> MST
