> On Fri, Feb 06, 2026 at 05:31:54PM +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.
> >
> > Signed-off-by: Srujana Challa <[email protected]>
>
> I'd CC stable on this actually. failing when device is more capable was a bad
> idea.
> can you add a Fixes: tag, too? Thanks!
Sure.
>
> > ---
> > drivers/net/virtio_net.c | 62
> > +++++++++++++++++++++++-----------------
> > 1 file changed, 36 insertions(+), 26 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index
> > db88dcaefb20..1fa4197dffc3 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -381,7 +381,8 @@ struct receive_queue {
> > struct xdp_buff **xsk_buffs;
> > };
> >
> > -#define VIRTIO_NET_RSS_MAX_KEY_SIZE 40
> > +#define VIRTIO_NET_RSS_MAX_KEY_SIZE NETDEV_RSS_KEY_LEN
> > +#define VIRTIO_NET_RSS_MIN_KEY_SIZE 40
> >
> > /* Control VQ buffers: protected by the rtnl lock */ struct
> > control_buf { @@ -6823,38 +6824,47 @@ static int virtnet_probe(struct
> > virtio_device *vdev)
> > if (virtio_has_feature(vdev, VIRTIO_NET_F_HASH_REPORT))
> > vi->has_rss_hash_report = true;
> >
> > - if (virtio_has_feature(vdev, VIRTIO_NET_F_RSS)) {
> > + if (virtio_has_feature(vdev, VIRTIO_NET_F_RSS))
> > vi->has_rss = true;
> >
> > - vi->rss_indir_table_size =
> > - virtio_cread16(vdev, offsetof(struct virtio_net_config,
> > - rss_max_indirection_table_length));
> > - }
> > - vi->rss_hdr = devm_kzalloc(&vdev->dev, virtnet_rss_hdr_size(vi),
> GFP_KERNEL);
> > - if (!vi->rss_hdr) {
> > - err = -ENOMEM;
> > - goto free;
> > - }
> > -
> > if (vi->has_rss || vi->has_rss_hash_report) {
> > vi->rss_key_size =
> > virtio_cread8(vdev, offsetof(struct virtio_net_config,
> rss_max_key_size));
> > - if (vi->rss_key_size > VIRTIO_NET_RSS_MAX_KEY_SIZE) {
> > - dev_err(&vdev->dev, "rss_max_key_size=%u exceeds
> the limit %u.\n",
> > - vi->rss_key_size,
> VIRTIO_NET_RSS_MAX_KEY_SIZE);
> > - err = -EINVAL;
> > - goto free;
> > - }
> >
> > - vi->rss_hash_types_supported =
> > - virtio_cread32(vdev, offsetof(struct virtio_net_config,
> supported_hash_types));
> > - vi->rss_hash_types_supported &=
> > - ~(VIRTIO_NET_RSS_HASH_TYPE_IP_EX |
> > - VIRTIO_NET_RSS_HASH_TYPE_TCP_EX |
> > - VIRTIO_NET_RSS_HASH_TYPE_UDP_EX);
> > + /* Spec requires at least 40 bytes */
> > + if (vi->rss_key_size < VIRTIO_NET_RSS_MIN_KEY_SIZE) {
> > + dev_warn(&vdev->dev,
> > + "rss_max_key_size=%u is less than spec
> minimum %u, disabling RSS\n",
> > + vi->rss_key_size,
> VIRTIO_NET_RSS_MIN_KEY_SIZE);
> > + vi->has_rss = false;
> > + vi->has_rss_hash_report = false;
> > + } else if (vi->rss_key_size > VIRTIO_NET_RSS_MAX_KEY_SIZE) {
> > + dev_warn(&vdev->dev,
> > + "rss_max_key_size=%u exceeds driver limit
> %u, disabling RSS\n",
> > + vi->rss_key_size,
> VIRTIO_NET_RSS_MAX_KEY_SIZE);
> > + vi->has_rss = false;
> > + vi->has_rss_hash_report = false;
> > + } else {
> > + vi->rss_indir_table_size =
> > + virtio_cread16(vdev, offsetof(struct
> virtio_net_config,
> > +
> rss_max_indirection_table_length));
> > + vi->rss_hash_types_supported =
> > + virtio_cread32(vdev, offsetof(struct
> virtio_net_config,
> > +
> supported_hash_types));
> > + vi->rss_hash_types_supported &=
> > +
> ~(VIRTIO_NET_RSS_HASH_TYPE_IP_EX |
> > +
> VIRTIO_NET_RSS_HASH_TYPE_TCP_EX |
> > +
> VIRTIO_NET_RSS_HASH_TYPE_UDP_EX);
> > +
> > + dev->hw_features |= NETIF_F_RXHASH;
> > + dev->xdp_metadata_ops =
> &virtnet_xdp_metadata_ops;
> > + }
> > + }
> >
> > - dev->hw_features |= NETIF_F_RXHASH;
> > - dev->xdp_metadata_ops = &virtnet_xdp_metadata_ops;
> > + vi->rss_hdr = devm_kzalloc(&vdev->dev, virtnet_rss_hdr_size(vi),
> GFP_KERNEL);
> > + if (!vi->rss_hdr) {
> > + err = -ENOMEM;
> > + goto free;
> > }
>
> I feel these checks belong in virtnet_validate. Then we can disable features
> e.g.
> by clearing VIRTIO_NET_F_RSS and host will have some visibility that RSS can't
> be used.
Sure, will move to virtnet_validate() and clear feature bits.
Thanks!
>
>
>
> >
> > if (virtio_has_feature(vdev,
> VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO) ||
> > --
> > 2.25.1
