netdev - Re: [PATCH iwl-next v1] ixgbe: preserve RSS indirection table across admin down/up

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Message-ID: <781791cb-b22f-4197-a4e6-ff11a6fba8d9@intel.com>
Date: Mon, 25 Aug 2025 11:48:21 +0200
From: Przemek Kitszel <przemyslaw.kitszel@...el.com>
To: Kohei Enju <enjuk@...zon.com>
CC: Tony Nguyen <anthony.l.nguyen@...el.com>,
	<intel-wired-lan@...ts.osuosl.org>, <netdev@...r.kernel.org>, Andrew Lunn
	<andrew+netdev@...n.ch>, "David S. Miller" <davem@...emloft.net>, "Eric
 Dumazet" <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>, <kohei.enju@...il.com>
Subject: Re: [PATCH iwl-next v1] ixgbe: preserve RSS indirection table across
 admin down/up

On 8/24/25 13:20, Kohei Enju wrote:
> Currently, the RSS indirection table configured by user via ethtool is
> reinitialized to default values during interface resets (e.g., admin
> down/up, MTU change). As for RSS hash key, commit 3dfbfc7ebb95 ("ixgbe:
> Check for RSS key before setting value") made it persistent across
> interface resets.
> 
> By adopting the same approach used in igc and igb drivers which
> reinitializes the RSS indirection table only when the queue count
> changes, let's make user configuration persistent as long as queue count
> remains unchanged.
> 
> Tested on Intel Corporation 82599ES 10-Gigabit SFI/SFP+ Network
> Connection.
> 
> Test:
> Set custom indirection table and check the value after interface down/up
> 
>    # ethtool --set-rxfh-indir ens5 equal 2
>    # ethtool --show-rxfh-indir ens5 | head -5
> 
>    RX flow hash indirection table for ens5 with 12 RX ring(s):
>        0:      0     1     0     1     0     1     0     1
>        8:      0     1     0     1     0     1     0     1
>       16:      0     1     0     1     0     1     0     1
>    # ip link set dev ens5 down && ip link set dev ens5 up
> 
> Without patch:
>    # ethtool --show-rxfh-indir ens5 | head -5
> 
>    RX flow hash indirection table for ens5 with 12 RX ring(s):
>        0:      0     1     2     3     4     5     6     7
>        8:      8     9    10    11     0     1     2     3
>       16:      4     5     6     7     8     9    10    11
> 
> With patch:
>    # ethtool --show-rxfh-indir ens5 | head -5
> 
>    RX flow hash indirection table for ens5 with 12 RX ring(s):
>        0:      0     1     0     1     0     1     0     1
>        8:      0     1     0     1     0     1     0     1
>       16:      0     1     0     1     0     1     0     1
> 
> Signed-off-by: Kohei Enju <enjuk@...zon.com>
> ---
>   drivers/net/ethernet/intel/ixgbe/ixgbe.h      |  1 +
>   drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 37 +++++++++++++------
>   2 files changed, 27 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe.h b/drivers/net/ethernet/intel/ixgbe/ixgbe.h
> index 14d275270123..d8b088c90b05 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe.h
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe.h
> @@ -838,6 +838,7 @@ struct ixgbe_adapter {
>    */
>   #define IXGBE_MAX_RETA_ENTRIES 512
>   	u8 rss_indir_tbl[IXGBE_MAX_RETA_ENTRIES];
> +	u16 last_rss_i;
>   
>   #define IXGBE_RSS_KEY_SIZE     40  /* size of RSS Hash Key in bytes */
>   	u32 *rss_key;
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> index 80e6a2ef1350..dc5a8373b0c3 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> @@ -4318,14 +4318,22 @@ static void ixgbe_setup_reta(struct ixgbe_adapter *adapter)
>   	/* Fill out hash function seeds */
>   	ixgbe_store_key(adapter);
>   
> -	/* Fill out redirection table */
> -	memset(adapter->rss_indir_tbl, 0, sizeof(adapter->rss_indir_tbl));
> +	/* Update redirection table in memory on first init or queue count
> +	 * change, otherwise preserve user configurations. Then always
> +	 * write to hardware.
> +	 */
> +	if (adapter->last_rss_i != rss_i) {
> +		memset(adapter->rss_indir_tbl, 0,
> +		       sizeof(adapter->rss_indir_tbl));

Thank you for the patch,
I see no point in the memset() above, especially given 0 as a valid
entry in the table.

> +
> +		for (i = 0, j = 0; i < reta_entries; i++, j++) {
> +			if (j == rss_i)
> +				j = 0;
>   
> -	for (i = 0, j = 0; i < reta_entries; i++, j++) {
> -		if (j == rss_i)
> -			j = 0;
> +			adapter->rss_indir_tbl[i] = j;
> +		}
>   
> -		adapter->rss_indir_tbl[i] = j;
> +		adapter->last_rss_i = rss_i;
>   	}
>   
>   	ixgbe_store_reta(adapter);
> @@ -4347,12 +4355,19 @@ static void ixgbe_setup_vfreta(struct ixgbe_adapter *adapter)
>   					*(adapter->rss_key + i));
>   	}
>   
> -	/* Fill out the redirection table */
> -	for (i = 0, j = 0; i < 64; i++, j++) {
> -		if (j == rss_i)
> -			j = 0;
> +	/* Update redirection table in memory on first init or queue count
> +	 * change, otherwise preserve user configurations. Then always
> +	 * write to hardware.
> +	 */
> +	if (adapter->last_rss_i != rss_i) {
> +		for (i = 0, j = 0; i < 64; i++, j++) {
> +			if (j == rss_i)
> +				j = 0;
> +
> +			adapter->rss_indir_tbl[i] = j;
> +		}
>   
> -		adapter->rss_indir_tbl[i] = j;
> +		adapter->last_rss_i = rss_i;
>   	}
>   
>   	ixgbe_store_vfreta(adapter);