Re: [PATCH v2] virtio-net: Zero max_tx_vq field for VIRTIO_NET_CTRL_MQ_HASH_CONFIG case

[Xuan Zhuo]

On Thu, 10 Aug 2023 19:04:05 +0800, Hawkins Jiawei <yin31149@xxxxxxxxx> wrote:
> Kernel uses `struct virtio_net_ctrl_rss` to save command-specific-data
> for both the VIRTIO_NET_CTRL_MQ_HASH_CONFIG and
> VIRTIO_NET_CTRL_MQ_RSS_CONFIG commands.
>
> According to the VirtIO standard, "Field reserved MUST contain zeroes.
> It is defined to make the structure to match the layout of
> virtio_net_rss_config structure, defined in 5.1.6.5.7.".
>
> Yet for the VIRTIO_NET_CTRL_MQ_HASH_CONFIG command case, the `max_tx_vq`
> field in struct virtio_net_ctrl_rss, which corresponds to the
> `reserved` field in struct virtio_net_hash_config, is not zeroed,
> thereby violating the VirtIO standard.
>
> This patch solves this problem by zeroing this field in
> virtnet_init_default_rss().
>
> Cc: Andrew Melnychenko <andrew@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: c7114b1249fa ("drivers/net/virtio_net: Added basic RSS support.")
> Signed-off-by: Hawkins Jiawei <yin31149@xxxxxxxxx>
> Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
> Acked-by: Eugenio Pérez <eperezma@xxxxxxxxxx>
> Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>

Reviewed-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>

> ---
>  drivers/net/virtio_net.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 1270c8d23463..8db38634ae82 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -2761,7 +2761,7 @@ static void virtnet_init_default_rss(struct virtnet_info *vi)
>  		vi->ctrl->rss.indirection_table[i] = indir_val;
>  	}
>
> -	vi->ctrl->rss.max_tx_vq = vi->curr_queue_pairs;
> +	vi->ctrl->rss.max_tx_vq = vi->has_rss ? vi->curr_queue_pairs : 0;
>  	vi->ctrl->rss.hash_key_length = vi->rss_key_size;
>
>  	netdev_rss_key_fill(vi->ctrl->rss.key, vi->rss_key_size);
> --
> 2.34.1
>