netdev - Re: [PATCH iwl-next v4 3/3] igb: allow configuring RSS key via ethtool set

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Message-ID: <20260125131327.4469-1-kohei@enjuk.jp>
Date: Sun, 25 Jan 2026 13:12:37 +0000
From: Kohei Enju <kohei@...uk.jp>
To: takkozu@...zon.com
Cc: aleksandr.loktionov@...el.com, andrew+netdev@...n.ch,
        anthony.l.nguyen@...el.com, davem@...emloft.net, edumazet@...gle.com,
        enjuk@...zon.com, intel-wired-lan@...ts.osuosl.org, kuba@...nel.org,
        netdev@...r.kernel.org, pabeni@...hat.com, piotr.kwapulinski@...el.com,
        pmenzel@...gen.mpg.de, przemyslaw.kitszel@...el.com
Subject: Re: [PATCH iwl-next v4 3/3] igb: allow configuring RSS key via ethtool set_rxfh

On Tue, 20 Jan 2026 18:34:40 +0900, Takashi Kozu wrote:

> Change igc_set_rxfh() to accept and save a userspace-provided
> RSS key. When a key is provided, store it in the adapter and write the
> E1000 registers accordingly.
> 
> This can be tested using `ethtool -X <dev> hkey <key>`.
> 
> Signed-off-by: Takashi Kozu <takkozu@...zon.com>
> ---
>  drivers/net/ethernet/intel/igb/igb.h         |  1 +
>  drivers/net/ethernet/intel/igb/igb_ethtool.c | 49 +++++++++++---------
>  drivers/net/ethernet/intel/igb/igb_main.c    |  3 +-
>  3 files changed, 30 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/igb/igb.h b/drivers/net/ethernet/intel/igb/igb.h
> index 8c9b02058cec..2509ec30acf3 100644
> --- a/drivers/net/ethernet/intel/igb/igb.h
> +++ b/drivers/net/ethernet/intel/igb/igb.h
> @@ -657,6 +657,7 @@ struct igb_adapter {
>  	u32 rss_indir_tbl_init;
>  	u8 rss_indir_tbl[IGB_RETA_SIZE];
>  	u8 rss_key[IGB_RSS_KEY_SIZE];
> +	bool has_user_rss_key;

Hi Kozu-san.

While preparing for testing, I noticed that now 'has_user_rss_key' is
not necessary.

Since netdev_rss_key_fill() is called in igb_sw_init() and igb_sw_init()
is called only once for the adapter's lifetime, adapter->rss_key
wouldn't be changed except for user-intended change.

I'd drop that flag and related code (see below)

>  
>  	unsigned long link_check_timeout;
>  	int copper_tries;
> diff --git a/drivers/net/ethernet/intel/igb/igb_ethtool.c b/drivers/net/ethernet/intel/igb/igb_ethtool.c
> index b387121f0ea7..1db9c2447c91 100644
> --- a/drivers/net/ethernet/intel/igb/igb_ethtool.c
> +++ b/drivers/net/ethernet/intel/igb/igb_ethtool.c
> @@ -3357,35 +3357,40 @@ static int igb_set_rxfh(struct net_device *netdev,
>  	u32 num_queues;
>  
>  	/* We do not allow change in unsupported parameters */
> -	if (rxfh->key ||
> -	    (rxfh->hfunc != ETH_RSS_HASH_NO_CHANGE &&
> -	     rxfh->hfunc != ETH_RSS_HASH_TOP))
> +	if (rxfh->hfunc != ETH_RSS_HASH_NO_CHANGE &&
> +	    rxfh->hfunc != ETH_RSS_HASH_TOP)
>  		return -EOPNOTSUPP;
> -	if (!rxfh->indir)
> -		return 0;
>  
> -	num_queues = adapter->rss_queues;
> +	if (rxfh->indir) {
> +		num_queues = adapter->rss_queues;
>  
> -	switch (hw->mac.type) {
> -	case e1000_82576:
> -		/* 82576 supports 2 RSS queues for SR-IOV */
> -		if (adapter->vfs_allocated_count)
> -			num_queues = 2;
> -		break;
> -	default:
> -		break;
> -	}
> +		switch (hw->mac.type) {
> +		case e1000_82576:
> +			/* 82576 supports 2 RSS queues for SR-IOV */
> +			if (adapter->vfs_allocated_count)
> +				num_queues = 2;
> +			break;
> +		default:
> +			break;
> +		}
>  
> -	/* Verify user input. */
> -	for (i = 0; i < IGB_RETA_SIZE; i++)
> -		if (rxfh->indir[i] >= num_queues)
> -			return -EINVAL;
> +		/* Verify user input. */
> +		for (i = 0; i < IGB_RETA_SIZE; i++)
> +			if (rxfh->indir[i] >= num_queues)
> +				return -EINVAL;
>  
>  
> -	for (i = 0; i < IGB_RETA_SIZE; i++)
> -		adapter->rss_indir_tbl[i] = rxfh->indir[i];
> +		for (i = 0; i < IGB_RETA_SIZE; i++)
> +			adapter->rss_indir_tbl[i] = rxfh->indir[i];
> +
> +		igb_write_rss_indir_tbl(adapter);
> +	}
>  
> -	igb_write_rss_indir_tbl(adapter);
> +	if (rxfh->key) {
> +		adapter->has_user_rss_key = true;

here

> +		memcpy(adapter->rss_key, rxfh->key, sizeof(adapter->rss_key));
> +		igb_write_rss_key(adapter);
> +	}
>  
>  	return 0;
>  }
> diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
> index c703011b19ec..8dab133296ca 100644
> --- a/drivers/net/ethernet/intel/igb/igb_main.c
> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> @@ -4051,7 +4051,8 @@ static int igb_sw_init(struct igb_adapter *adapter)
>  	pci_read_config_word(pdev, PCI_COMMAND, &hw->bus.pci_cmd_word);
>  
>  	/* init RSS key */
> -	netdev_rss_key_fill(adapter->rss_key, sizeof(adapter->rss_key));
> +	if (!adapter->has_user_rss_key)
> +		netdev_rss_key_fill(adapter->rss_key, sizeof(adapter->rss_key));

and this diff.

>  
>  	/* set default ring sizes */
>  	adapter->tx_ring_count = IGB_DEFAULT_TXD;
> -- 
> 2.52.0