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!
> ---
> 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.
>
> if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO) ||
> --
> 2.25.1
