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

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Message-ID: <2d6b0d54-57d3-4f3b-833c-8490aa63490d@intel.com>
Date: Thu, 31 Oct 2024 08:34:36 +0100
From: Przemek Kitszel <przemyslaw.kitszel@...el.com>
To: Paul Menzel <pmenzel@...gen.mpg.de>, Peter Große
	<pegro@...iks.de>
CC: <intel-wired-lan@...ts.osuosl.org>, Tony Nguyen
	<anthony.l.nguyen@...el.com>, <netdev@...r.kernel.org>
Subject: Re: [PATCH iwl-net v2] i40e: Fix handling changed priv flags

On 10/30/24 18:35, Paul Menzel wrote:
> 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>

Both the code change and the Fixes: tag are correct, thank you!
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@...el.com>

BTW, we obey netdev rules on IWL ML - next revision only after 24-48h
and send as standalone series (instead of In-reply-to) - no need to
repost this time of course

>> ---
>>   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