netdev - Re: [PATCH iwl-net v2] i40e: Fix handling changed priv flags

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Message-ID: <03b7d4ef-1e1e-4b9e-84b6-1ff4a5b92b29@molgen.mpg.de>
Date: Wed, 30 Oct 2024 18:35:35 +0100
From: Paul Menzel <pmenzel@...gen.mpg.de>
To: Peter Große <pegro@...iks.de>
Cc: intel-wired-lan@...ts.osuosl.org, Tony Nguyen
 <anthony.l.nguyen@...el.com>, Przemek Kitszel
 <przemyslaw.kitszel@...el.com>, netdev@...r.kernel.org
Subject: Re: [PATCH iwl-net v2] i40e: Fix handling changed priv flags

Dear Peter,


Am 30.10.24 um 18:22 schrieb pegro@...iks.de:
> From: Peter Große <pegro@...iks.de>
> 
> After assembling the new private flags on a PF, the operation to determine
> the changed flags uses the wrong bitmaps. Instead of xor-ing orig_flags
> with new_flags, it uses the still unchanged pf->flags, thus changed_flags
> is always 0.
> 
> Fix it by using the correct bitmaps.
> 
> The issue was discovered while debugging why disabling source pruning
> stopped working with release 6.7. Although the new flags will be copied to
> pf->flags later on in that function, disabling source pruning requires
> a reset of the PF, which was skipped due to this bug.
> 
> Disabling source pruning:
> $ sudo ethtool --set-priv-flags eno1 disable-source-pruning on
> $ sudo ethtool --show-priv-flags eno1
> Private flags for eno1:
> MFP                   : off
> total-port-shutdown   : off
> LinkPolling           : off
> flow-director-atr     : on
> veb-stats             : off
> hw-atr-eviction       : off
> link-down-on-close    : off
> legacy-rx             : off
> disable-source-pruning: on
> disable-fw-lldp       : off
> rs-fec                : off
> base-r-fec            : off
> vf-vlan-pruning       : off
> 
> Regarding reproducing:
> 
> I observed the issue with a rather complicated lab setup, where
>   * two VLAN interfaces are created on eno1
>   * each with a different MAC address assigned
>   * each moved into a separate namespace
>   * both VLANs are bridged externally, so they form a single layer 2 network
> 
> The external bridge is done via a channel emulator adding packet loss and
> delay and the application in the namespaces tries to send/receive traffic
> and measure the performance. Sender and receiver are separated by
> namespaces, yet the network card "sees its own traffic" send back to it.
> To make that work, source pruning has to be disabled.

Thank you for taking the time to write this up.

> Fixes: 70756d0a4727 ("i40e: Use DECLARE_BITMAP for flags and hw_features fields in i40e_pf")
> Signed-off-by: Peter Große <pegro@...iks.de>
> ---
>   drivers/net/ethernet/intel/i40e/i40e_ethtool.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_ethtool.c b/drivers/net/ethernet/intel/i40e/i40e_ethtool.c
> index c841779713f6..016c0ae6b36f 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_ethtool.c
> +++ b/drivers/net/ethernet/intel/i40e/i40e_ethtool.c
> @@ -5306,7 +5306,7 @@ static int i40e_set_priv_flags(struct net_device *dev, u32 flags)
>   	}
>   
>   flags_complete:
> -	bitmap_xor(changed_flags, pf->flags, orig_flags, I40E_PF_FLAGS_NBITS);
> +	bitmap_xor(changed_flags, new_flags, orig_flags, I40E_PF_FLAGS_NBITS);
>   
>   	if (test_bit(I40E_FLAG_FW_LLDP_DIS, changed_flags))
>   		reset_needed = I40E_PF_RESET_AND_REBUILD_FLAG;

Reviewed-by: Paul Menzel <pmenzel@...gen.mpg.de>


Kind regards,

Paul