Re: [PATCH net-next 3/4] virtio_net: Use new RSS config structs

[Jason Wang]

On Tue, Mar 18, 2025 at 5:57 PM Akihiko Odaki <akihiko.odaki@xxxxxxxxxx> wrote:
>
> The new RSS configuration structures allow easily constructing data for
> VIRTIO_NET_CTRL_MQ_RSS_CONFIG as they strictly follow the order of data
> for the command.
>
> Signed-off-by: Akihiko Odaki <akihiko.odaki@xxxxxxxxxx>
> ---
>  drivers/net/virtio_net.c | 117 +++++++++++++++++------------------------------
>  1 file changed, 43 insertions(+), 74 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index d1ed544ba03a..4153a0a5f278 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -360,24 +360,7 @@ struct receive_queue {
>         struct xdp_buff **xsk_buffs;
>  };
>
> -/* This structure can contain rss message with maximum settings for indirection table and keysize
> - * Note, that default structure that describes RSS configuration virtio_net_rss_config
> - * contains same info but can't handle table values.
> - * In any case, structure would be passed to virtio hw through sg_buf split by parts
> - * because table sizes may be differ according to the device configuration.
> - */
>  #define VIRTIO_NET_RSS_MAX_KEY_SIZE     40
> -struct virtio_net_ctrl_rss {
> -       __le32 hash_types;
> -       __le16 indirection_table_mask;
> -       __le16 unclassified_queue;
> -       __le16 hash_cfg_reserved; /* for HASH_CONFIG (see virtio_net_hash_config for details) */
> -       __le16 max_tx_vq;
> -       u8 hash_key_length;
> -       u8 key[VIRTIO_NET_RSS_MAX_KEY_SIZE];
> -
> -       __le16 *indirection_table;
> -};
>
>  /* Control VQ buffers: protected by the rtnl lock */
>  struct control_buf {
> @@ -421,7 +404,9 @@ struct virtnet_info {
>         u16 rss_indir_table_size;
>         u32 rss_hash_types_supported;
>         u32 rss_hash_types_saved;
> -       struct virtio_net_ctrl_rss rss;
> +       struct virtio_net_rss_config_hdr *rss_hdr;
> +       struct virtio_net_rss_config_trailer rss_trailer;
> +       u8 rss_hash_key_data[VIRTIO_NET_RSS_MAX_KEY_SIZE];
>
>         /* Has control virtqueue */
>         bool has_cvq;
> @@ -523,23 +508,16 @@ enum virtnet_xmit_type {
>         VIRTNET_XMIT_TYPE_XSK,
>  };
>
> -static int rss_indirection_table_alloc(struct virtio_net_ctrl_rss *rss, u16 indir_table_size)
> +static size_t virtnet_rss_hdr_size(const struct virtnet_info *vi)
>  {
> -       if (!indir_table_size) {
> -               rss->indirection_table = NULL;
> -               return 0;
> -       }
> +       u16 indir_table_size = vi->has_rss ? vi->rss_indir_table_size : 1;
>
> -       rss->indirection_table = kmalloc_array(indir_table_size, sizeof(u16), GFP_KERNEL);
> -       if (!rss->indirection_table)
> -               return -ENOMEM;
> -
> -       return 0;
> +       return struct_size(vi->rss_hdr, indirection_table, indir_table_size);
>  }
>
> -static void rss_indirection_table_free(struct virtio_net_ctrl_rss *rss)
> +static size_t virtnet_rss_trailer_size(const struct virtnet_info *vi)
>  {
> -       kfree(rss->indirection_table);
> +       return struct_size(&vi->rss_trailer, hash_key_data, vi->rss_key_size);
>  }
>
>  /* We use the last two bits of the pointer to distinguish the xmit type. */
> @@ -3576,15 +3554,16 @@ static void virtnet_rss_update_by_qpairs(struct virtnet_info *vi, u16 queue_pair
>
>         for (; i < vi->rss_indir_table_size; ++i) {
>                 indir_val = ethtool_rxfh_indir_default(i, queue_pairs);
> -               vi->rss.indirection_table[i] = cpu_to_le16(indir_val);
> +               vi->rss_hdr->indirection_table[i] = cpu_to_le16(indir_val);
>         }
> -       vi->rss.max_tx_vq = cpu_to_le16(queue_pairs);
> +       vi->rss_trailer.max_tx_vq = cpu_to_le16(queue_pairs);
>  }
>
>  static int virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs)
>  {
>         struct virtio_net_ctrl_mq *mq __free(kfree) = NULL;
> -       struct virtio_net_ctrl_rss old_rss;
> +       struct virtio_net_rss_config_hdr *old_rss_hdr;
> +       struct virtio_net_rss_config_trailer old_rss_trailer;
>         struct net_device *dev = vi->dev;
>         struct scatterlist sg;
>
> @@ -3599,24 +3578,28 @@ static int virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs)
>          * update (VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET below) and return directly.
>          */
>         if (vi->has_rss && !netif_is_rxfh_configured(dev)) {
> -               memcpy(&old_rss, &vi->rss, sizeof(old_rss));
> -               if (rss_indirection_table_alloc(&vi->rss, vi->rss_indir_table_size)) {
> -                       vi->rss.indirection_table = old_rss.indirection_table;
> +               old_rss_hdr = vi->rss_hdr;
> +               old_rss_trailer = vi->rss_trailer;
> +               vi->rss_hdr = kmalloc(virtnet_rss_hdr_size(vi), GFP_KERNEL);
> +               if (!vi->rss_hdr) {
> +                       vi->rss_hdr = old_rss_hdr;
>                         return -ENOMEM;
>                 }
>
> +               *vi->rss_hdr = *old_rss_hdr;
>                 virtnet_rss_update_by_qpairs(vi, queue_pairs);
>
>                 if (!virtnet_commit_rss_command(vi)) {
>                         /* restore ctrl_rss if commit_rss_command failed */
> -                       rss_indirection_table_free(&vi->rss);
> -                       memcpy(&vi->rss, &old_rss, sizeof(old_rss));
> +                       kfree(vi->rss_hdr);
> +                       vi->rss_hdr = old_rss_hdr;
> +                       vi->rss_trailer = old_rss_trailer;
>
>                         dev_warn(&dev->dev, "Fail to set num of queue pairs to %d, because committing RSS failed\n",
>                                  queue_pairs);
>                         return -EINVAL;
>                 }
> -               rss_indirection_table_free(&old_rss);
> +               kfree(old_rss_hdr);
>                 goto succ;
>         }
>
> @@ -4059,28 +4042,12 @@ static int virtnet_set_ringparam(struct net_device *dev,
>  static bool virtnet_commit_rss_command(struct virtnet_info *vi)
>  {
>         struct net_device *dev = vi->dev;
> -       struct scatterlist sgs[4];
> -       unsigned int sg_buf_size;
> +       struct scatterlist sgs[2];
>
>         /* prepare sgs */
> -       sg_init_table(sgs, 4);
> -
> -       sg_buf_size = offsetof(struct virtio_net_ctrl_rss, hash_cfg_reserved);
> -       sg_set_buf(&sgs[0], &vi->rss, sg_buf_size);
> -
> -       if (vi->has_rss) {
> -               sg_buf_size = sizeof(uint16_t) * vi->rss_indir_table_size;
> -               sg_set_buf(&sgs[1], vi->rss.indirection_table, sg_buf_size);
> -       } else {
> -               sg_set_buf(&sgs[1], &vi->rss.hash_cfg_reserved, sizeof(uint16_t));
> -       }
> -
> -       sg_buf_size = offsetof(struct virtio_net_ctrl_rss, key)
> -                       - offsetof(struct virtio_net_ctrl_rss, max_tx_vq);
> -       sg_set_buf(&sgs[2], &vi->rss.max_tx_vq, sg_buf_size);
> -
> -       sg_buf_size = vi->rss_key_size;
> -       sg_set_buf(&sgs[3], vi->rss.key, sg_buf_size);
> +       sg_init_table(sgs, 2);
> +       sg_set_buf(&sgs[0], vi->rss_hdr, virtnet_rss_hdr_size(vi));
> +       sg_set_buf(&sgs[1], &vi->rss_trailer, virtnet_rss_trailer_size(vi));

So I still see this:

        if (vi->has_rss || vi->has_rss_hash_report) {
                if (!virtnet_commit_rss_command(vi)) {

Should we introduce a hash config helper instead?

Thanks