netdev - Re: [PATCH iwl-next v4] ixgbe: preserve RSS indirection table across admin down/up

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Message-ID: <20250923092853.GG836419@horms.kernel.org>
Date: Tue, 23 Sep 2025 10:28:53 +0100
From: Simon Horman <horms@...nel.org>
To: Kohei Enju <enjuk@...zon.com>
Cc: intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
	Tony Nguyen <anthony.l.nguyen@...el.com>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>,
	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>,
	aleksandr.loktionov@...el.com, kohei.enju@...il.com
Subject: Re: [PATCH iwl-next v4] ixgbe: preserve RSS indirection table across
 admin down/up

On Sat, Sep 20, 2025 at 07:25:45PM +0900, 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.
> 
> Adopt the same approach used in igc and igb drivers which reinitializes
> the RSS indirection table only when the queue count changes. Since the
> number of RETA entries can also change in ixgbe, let's make user
> configuration persistent as long as both queue count and the number of
> RETA entries remain 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>
> ---
> Changes:
> v3->v4:
>   - ensure rss_i is non-zero to avoid zero-division

Reviewed-by: Simon Horman <horms@...nel.org>