netdev - Re: [PATCH V1 net-next 02/13] net: ena: avoid unnecessary admin command when RSS function set fails

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Message-ID: <20200422173941.5d43c2df@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 22 Apr 2020 17:39:41 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     <sameehj@...zon.com>
Cc:     <davem@...emloft.net>, <netdev@...r.kernel.org>,
        Arthur Kiyanovski <akiyano@...zon.com>, <dwmw@...zon.com>,
        <zorik@...zon.com>, <matua@...zon.com>, <saeedb@...zon.com>,
        <msw@...zon.com>, <aliguori@...zon.com>, <nafea@...zon.com>,
        <gtzalik@...zon.com>, <netanel@...zon.com>, <alisaidi@...zon.com>,
        <benh@...zon.com>, <ndagan@...zon.com>
Subject: Re: [PATCH V1 net-next 02/13] net: ena: avoid unnecessary admin
 command when RSS function set fails

On Wed, 22 Apr 2020 08:16:17 +0000 sameehj@...zon.com wrote:
> From: Arthur Kiyanovski <akiyano@...zon.com>
> 
> Currently when ena_set_hash_function() fails the hash function is
> restored to the previous value by calling an admin command to get
> the hash function from the device.

I don't see how. func argument is NULL. If I'm reading the code right
if this function is restoring anything it's restoring the rss key.

> In this commit we avoid the admin command, by saving the previous
> hash function before calling ena_set_hash_function() and using this
> previous value to restore the hash function in case of failure of
> ena_set_hash_function().
> 
> Signed-off-by: Sameeh Jubran <sameehj@...zon.com>
> Signed-off-by: Arthur Kiyanovski <akiyano@...zon.com>
> ---
>  drivers/net/ethernet/amazon/ena/ena_com.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/amazon/ena/ena_com.c b/drivers/net/ethernet/amazon/ena/ena_com.c
> index 07b0f396d3c2..66edc86c41c9 100644
> --- a/drivers/net/ethernet/amazon/ena/ena_com.c
> +++ b/drivers/net/ethernet/amazon/ena/ena_com.c
> @@ -2286,6 +2286,7 @@ int ena_com_fill_hash_function(struct ena_com_dev *ena_dev,
>  	struct ena_admin_get_feat_resp get_resp;
>  	struct ena_admin_feature_rss_flow_hash_control *hash_key =
>  		rss->hash_key;
> +	enum ena_admin_hash_functions old_func;
>  	int rc;
>  
>  	/* Make sure size is a mult of DWs */
> @@ -2325,12 +2326,13 @@ int ena_com_fill_hash_function(struct ena_com_dev *ena_dev,
>  		return -EINVAL;
>  	}
>  
> +	old_func = rss->hash_func;
>  	rss->hash_func = func;
>  	rc = ena_com_set_hash_function(ena_dev);
>  
>  	/* Restore the old function */
>  	if (unlikely(rc))
> -		ena_com_get_hash_function(ena_dev, NULL, NULL);
> +		rss->hash_func = old_func;

Please order your commits correctly.

>  	return rc;
>  }