Re: [RFC v1 02/22] net: ethtool: report max value for rx-buf-len

[Subbaraya Sundeep <sbhatta@marvell.com>]

LGTM.

Thanks,
Sundeep

On 2025-07-28 at 11:04:06, Pavel Begunkov (asml.silence@gmail.com) wrote:
> From: Jakub Kicinski <kuba@kernel.org>
> 
> Unlike most of our APIs the rx-buf-len param does not have an associated
> max value. In theory user could set this value pretty high, but in
> practice most NICs have limits due to the width of the length fields
> in the descriptors.
> 
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
> ---
>  Documentation/netlink/specs/ethtool.yaml                  | 4 ++++
>  Documentation/networking/ethtool-netlink.rst              | 1 +
>  drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c | 3 ++-
>  include/linux/ethtool.h                                   | 2 ++
>  include/uapi/linux/ethtool_netlink_generated.h            | 1 +
>  net/ethtool/rings.c                                       | 5 +++++
>  6 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/netlink/specs/ethtool.yaml b/Documentation/netlink/specs/ethtool.yaml
> index 72a076b0e1b5..cb96b4e7093f 100644
> --- a/Documentation/netlink/specs/ethtool.yaml
> +++ b/Documentation/netlink/specs/ethtool.yaml
> @@ -361,6 +361,9 @@ attribute-sets:
>        -
>          name: hds-thresh-max
>          type: u32
> +      -
> +        name: rx-buf-len-max
> +        type: u32
>  
>    -
>      name: mm-stat
> @@ -1811,6 +1814,7 @@ operations:
>              - rx-jumbo
>              - tx
>              - rx-buf-len
> +            - rx-buf-len-max
>              - tcp-data-split
>              - cqe-size
>              - tx-push
> diff --git a/Documentation/networking/ethtool-netlink.rst b/Documentation/networking/ethtool-netlink.rst
> index eaa9c17a3cb1..b7a99dfdffa9 100644
> --- a/Documentation/networking/ethtool-netlink.rst
> +++ b/Documentation/networking/ethtool-netlink.rst
> @@ -893,6 +893,7 @@ Kernel response contents:
>    ``ETHTOOL_A_RINGS_RX_JUMBO``              u32     size of RX jumbo ring
>    ``ETHTOOL_A_RINGS_TX``                    u32     size of TX ring
>    ``ETHTOOL_A_RINGS_RX_BUF_LEN``            u32     size of buffers on the ring
> +  ``ETHTOOL_A_RINGS_RX_BUF_LEN_MAX``        u32     max size of rx buffers
>    ``ETHTOOL_A_RINGS_TCP_DATA_SPLIT``        u8      TCP header / data split
>    ``ETHTOOL_A_RINGS_CQE_SIZE``              u32     Size of TX/RX CQE
>    ``ETHTOOL_A_RINGS_TX_PUSH``               u8      flag of TX Push mode
> diff --git a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c
> index 45b8c9230184..7bdef64926c8 100644
> --- a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c
> +++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c
> @@ -376,6 +376,7 @@ static void otx2_get_ringparam(struct net_device *netdev,
>  	ring->tx_max_pending = Q_COUNT(Q_SIZE_MAX);
>  	ring->tx_pending = qs->sqe_cnt ? qs->sqe_cnt : Q_COUNT(Q_SIZE_4K);
>  	kernel_ring->rx_buf_len = pfvf->hw.rbuf_len;
> +	kernel_ring->rx_buf_len_max = 32768;
>  	kernel_ring->cqe_size = pfvf->hw.xqe_size;
>  }
>  
> @@ -398,7 +399,7 @@ static int otx2_set_ringparam(struct net_device *netdev,
>  	/* Hardware supports max size of 32k for a receive buffer
>  	 * and 1536 is typical ethernet frame size.
>  	 */
> -	if (rx_buf_len && (rx_buf_len < 1536 || rx_buf_len > 32768)) {
> +	if (rx_buf_len && (rx_buf_len < 1536)) {
>  		netdev_err(netdev,
>  			   "Receive buffer range is 1536 - 32768");
>  		return -EINVAL;
> diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
> index 5e0dd333ad1f..dd9f253a56ae 100644
> --- a/include/linux/ethtool.h
> +++ b/include/linux/ethtool.h
> @@ -77,6 +77,7 @@ enum {
>  /**
>   * struct kernel_ethtool_ringparam - RX/TX ring configuration
>   * @rx_buf_len: Current length of buffers on the rx ring.
> + * @rx_buf_len_max: Max length of buffers on the rx ring.
>   * @tcp_data_split: Scatter packet headers and data to separate buffers
>   * @tx_push: The flag of tx push mode
>   * @rx_push: The flag of rx push mode
> @@ -89,6 +90,7 @@ enum {
>   */
>  struct kernel_ethtool_ringparam {
>  	u32	rx_buf_len;
> +	u32	rx_buf_len_max;
>  	u8	tcp_data_split;
>  	u8	tx_push;
>  	u8	rx_push;
> diff --git a/include/uapi/linux/ethtool_netlink_generated.h b/include/uapi/linux/ethtool_netlink_generated.h
> index aa8ab5227c1e..1a76e6789e33 100644
> --- a/include/uapi/linux/ethtool_netlink_generated.h
> +++ b/include/uapi/linux/ethtool_netlink_generated.h
> @@ -164,6 +164,7 @@ enum {
>  	ETHTOOL_A_RINGS_TX_PUSH_BUF_LEN_MAX,
>  	ETHTOOL_A_RINGS_HDS_THRESH,
>  	ETHTOOL_A_RINGS_HDS_THRESH_MAX,
> +	ETHTOOL_A_RINGS_RX_BUF_LEN_MAX,
>  
>  	__ETHTOOL_A_RINGS_CNT,
>  	ETHTOOL_A_RINGS_MAX = (__ETHTOOL_A_RINGS_CNT - 1)
> diff --git a/net/ethtool/rings.c b/net/ethtool/rings.c
> index aeedd5ec6b8c..5e872ceab5dd 100644
> --- a/net/ethtool/rings.c
> +++ b/net/ethtool/rings.c
> @@ -105,6 +105,9 @@ static int rings_fill_reply(struct sk_buff *skb,
>  			  ringparam->tx_pending)))  ||
>  	    (kr->rx_buf_len &&
>  	     (nla_put_u32(skb, ETHTOOL_A_RINGS_RX_BUF_LEN, kr->rx_buf_len))) ||
> +	    (kr->rx_buf_len_max &&
> +	     (nla_put_u32(skb, ETHTOOL_A_RINGS_RX_BUF_LEN_MAX,
> +			  kr->rx_buf_len_max))) ||
>  	    (kr->tcp_data_split &&
>  	     (nla_put_u8(skb, ETHTOOL_A_RINGS_TCP_DATA_SPLIT,
>  			 kr->tcp_data_split))) ||
> @@ -281,6 +284,8 @@ ethnl_set_rings(struct ethnl_req_info *req_info, struct genl_info *info)
>  		err_attr = tb[ETHTOOL_A_RINGS_TX];
>  	else if (kernel_ringparam.hds_thresh > kernel_ringparam.hds_thresh_max)
>  		err_attr = tb[ETHTOOL_A_RINGS_HDS_THRESH];
> +	else if (kernel_ringparam.rx_buf_len > kernel_ringparam.rx_buf_len_max)
> +		err_attr = tb[ETHTOOL_A_RINGS_RX_BUF_LEN];
>  	else
>  		err_attr = NULL;
>  	if (err_attr) {
> -- 
> 2.49.0
>