netdev - Re: [PATCH RFC v1 net-next 1/5] ethtool: Add support for configuring tx_push_buf

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Message-ID: <pj41zledq742hf.fsf@u570694869fb251.ant.amazon.com>
Date:   Thu, 2 Mar 2023 16:23:59 +0200
From:   Shay Agroskin <shayagr@...zon.com>
To:     Jakub Kicinski <kuba@...nel.org>
CC:     David Miller <davem@...emloft.net>, <netdev@...r.kernel.org>,
        "Woodhouse, David" <dwmw@...zon.com>,
        "Machulsky, Zorik" <zorik@...zon.com>,
        "Matushevsky, Alexander" <matua@...zon.com>,
        Saeed Bshara <saeedb@...zon.com>,
        "Wilson, Matt" <msw@...zon.com>,
        "Liguori, Anthony" <aliguori@...zon.com>,
        "Bshara, Nafea" <nafea@...zon.com>,
        "Belgazal, Netanel" <netanel@...zon.com>,
        "Saidi, Ali" <alisaidi@...zon.com>,
        "Herrenschmidt, Benjamin" <benh@...zon.com>,
        "Kiyanovski, Arthur" <akiyano@...zon.com>,
        "Dagan, Noam" <ndagan@...zon.com>,
        "Arinzon, David" <darinzon@...zon.com>,
        "Itzko, Shahar" <itzko@...zon.com>,
        "Abboud, Osama" <osamaabb@...zon.com>
Subject: Re: [PATCH RFC v1 net-next 1/5] ethtool: Add support for
 configuring tx_push_buf_len


Jakub Kicinski <kuba@...nel.org> writes:

> On Wed, 1 Mar 2023 19:59:12 +0200 Shay Agroskin wrote:
>> @@ -98,7 +100,12 @@ static int rings_fill_reply(struct sk_buff 
>> *skb,
>>  	    (kr->cqe_size &&
>>  	     (nla_put_u32(skb, ETHTOOL_A_RINGS_CQE_SIZE, 
>>  kr->cqe_size))) ||
>>  	    nla_put_u8(skb, ETHTOOL_A_RINGS_TX_PUSH, 
>>  !!kr->tx_push) ||
>> -	    nla_put_u8(skb, ETHTOOL_A_RINGS_RX_PUSH, 
>> !!kr->rx_push))
>> +	    nla_put_u8(skb, ETHTOOL_A_RINGS_RX_PUSH, 
>> !!kr->rx_push) ||
>> +	    (kr->tx_push_buf_len &&
>> +	     (nla_put_u32(skb, 
>> ETHTOOL_A_RINGS_TX_PUSH_BUF_LEN_MAX,
>> +			  kr->tx_push_buf_max_len) ||
>> +	      nla_put_u32(skb, ETHTOOL_A_RINGS_TX_PUSH_BUF_LEN,
>> +			  kr->tx_push_buf_len))))
>
> Why gate both on kr->tx_push_buf_len and not current and max 
> separately?
> Is kr->tx_push_buf_len == 0 never a valid setting?
>

Hi, thanks for reviewing it

There's actually no requirement that tx_push_buf_len needs to be > 
0. I'll drop this check.
It seems like the reply object gets zeroed at 
ethnl_init_reply_data() so ENA can simply not touch this field if 
no push buffer exists, leaving the values at 0.

> Otherwise LGTM!
>
> Could you add this chunk to expose the value in the YAML spec?
>
> diff --git a/Documentation/netlink/specs/ethtool.yaml 
> b/Documentation/netlink/specs/ethtool.yaml
> index 35c462bce56f..2dd6aef582e4 100644
> --- a/Documentation/netlink/specs/ethtool.yaml
> +++ b/Documentation/netlink/specs/ethtool.yaml
> @@ -163,6 +163,12 @@ doc: Partial family for Ethtool Netlink.
>        -
>          name: rx-push
>          type: u8
> +      -
> +        name: tx-push-buf-len
> +        type: u32
> +      -
> +        name: tx-push-buf-len-max
> +        type: u32
>  
>    -
>      name: mm-stat
> @@ -309,6 +315,8 @@ doc: Partial family for Ethtool Netlink.
>              - cqe-size
>              - tx-push
>              - rx-push
> +            - tx-push-buf-len
> +            - tx-push-buf-len-max
>        dump: *ring-get-op
>      -
>        name: rings-set

ack. I'll add it