On Tue, Feb 24, 2026 at 12:28:49PM +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.
>
> Cc: [email protected]
> Fixes: 3f7d9c1964fc ("virtio_net: Add hash_key_length check")
> Signed-off-by: Srujana Challa <[email protected]>
--- should come here before changelog.
> v3:
> - Moved RSS key validation checks to virtnet_validate.
> - Add fixes: tag and CC -stable
> v4:
> - Use NETDEV_RSS_KEY_LEN instead of type_max for the maximum rss key size.
> ---
> drivers/net/virtio_net.c | 34 ++++++++++++++++++++++++----------
> 1 file changed, 24 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index db88dcaefb20..eeefe8abc122 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -381,8 +381,6 @@ struct receive_queue {
> struct xdp_buff **xsk_buffs;
> };
>
> -#define VIRTIO_NET_RSS_MAX_KEY_SIZE 40
> -
> /* Control VQ buffers: protected by the rtnl lock */
> struct control_buf {
> struct virtio_net_ctrl_hdr hdr;
> @@ -486,7 +484,7 @@ struct virtnet_info {
>
> /* Must be last as it ends in a flexible-array member. */
> TRAILING_OVERLAP(struct virtio_net_rss_config_trailer, rss_trailer,
> hash_key_data,
> - u8 rss_hash_key_data[VIRTIO_NET_RSS_MAX_KEY_SIZE];
> + u8 rss_hash_key_data[NETDEV_RSS_KEY_LEN];
> );
> };
> static_assert(offsetof(struct virtnet_info, rss_trailer.hash_key_data) ==
> @@ -6627,6 +6625,29 @@ static int virtnet_validate(struct virtio_device *vdev)
> __virtio_clear_bit(vdev, VIRTIO_NET_F_STANDBY);
> }
>
> + if (virtio_has_feature(vdev, VIRTIO_NET_F_RSS) ||
> + virtio_has_feature(vdev, VIRTIO_NET_F_HASH_REPORT)) {
> + u8 key_sz = virtio_cread8(vdev,
> + offsetof(struct virtio_net_config,
> + rss_max_key_size));
> + /* Spec requires at least 40 bytes */
> +#define VIRTIO_NET_RSS_MIN_KEY_SIZE 40
> + if (key_sz < VIRTIO_NET_RSS_MIN_KEY_SIZE) {
> + dev_warn(&vdev->dev,
> + "rss_max_key_size=%u is less than spec minimum
> %u, disabling RSS\n",
> + key_sz, VIRTIO_NET_RSS_MIN_KEY_SIZE);
> + __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);
you flipped the logic here and it makes no sense now.
Did you test this path?
So if device is powerful and supports a very big key size then...
we disable the feature? how does this make sense?
> + }
> + }
> +
> return 0;
> }
>
> @@ -6839,13 +6860,6 @@ static int virtnet_probe(struct virtio_device *vdev)
> 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 &=
> --
> 2.25.1
