netdev - Re: [PATCH net-next 1/5] net: ethtool: only allow set_rxnfc with rss + ring

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Message-ID: <6ab56991-1415-4009-a630-14a0b709583d@intel.com>
Date: Mon, 25 Nov 2024 07:20:53 -0700
From: Ahmed Zaki <ahmed.zaki@...el.com>
To: Gal Pressman <gal@...dia.com>, Edward Cree <ecree.xilinx@...il.com>,
	<edward.cree@....com>, <davem@...emloft.net>, <kuba@...nel.org>,
	<edumazet@...gle.com>, <pabeni@...hat.com>
CC: <netdev@...r.kernel.org>, <habetsm.xilinx@...il.com>,
	<linux-net-drivers@....com>, <horms@...nel.org>, <andrew+netdev@...n.ch>,
	<shuah@...nel.org>, <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH net-next 1/5] net: ethtool: only allow set_rxnfc with rss
 + ring_cookie if driver opts in



On 2024-11-25 7:10 a.m., Gal Pressman wrote:
> On 25/11/2024 15:21, Edward Cree wrote:
>> On 25/11/2024 07:11, Gal Pressman wrote:
>>> On 13/11/2024 14:13, edward.cree@....com wrote:
>>>> Ethtool ntuple filters with FLOW_RSS were originally defined as adding
>>>>   the base queue ID (ring_cookie) to the value from the indirection table,
>>>>   so that the same table could distribute over more than one set of queues
>>>>   when used by different filters.
>>>
>>> TBH, I'm not sure I understand the difference? Perhaps you can share an
>>> example?
>>
>> Something like this:
>>
>> ethtool -X $intf context new equal 2
>> # creates context ID 1, table filled with 0s and 1s
>> ethtool -N $intf <match fields...> context 1
>> # filter distributes traffic to queues 0 and 1
>> ethtool -N $intf <match fields...> context 1 action 2
>> # filter distributes traffic to queues 2 and 3
>>
>> See the selftest in patch 4 for a concrete example of this.
>> Some NICs were apparently sending the traffic from both filters to
>>   queues 0 and 1, and ignoring the 'action 2' on the second filter.
> 
> Thanks, I did not know it works that way, is it actually documented
> anywhere?
> 
>>
>>>> @@ -992,6 +992,11 @@ static noinline_for_stack int ethtool_set_rxnfc(struct net_device *dev,
>>>>   	if (rc)
>>>>   		return rc;
>>>>   
>>>> +	/* Nonzero ring with RSS only makes sense if NIC adds them together */
>>>> +	if (info.flow_type & FLOW_RSS && !ops->cap_rss_rxnfc_adds &&
>>>> +	    ethtool_get_flow_spec_ring(info.fs.ring_cookie))
>>>> +		return -EINVAL;
>>>
>>> I believe this check shouldn't happen when we do ETHTOOL_SRXCLSRLDEL as
>>> flow_type is garbage, WDYT?
>>
>> Agreed; this check should only apply to ETHTOOL_SRXCLSRLINS.  Do you want
>>   to send the fix or shall I?
> 
> I will do it.
> 
>>
>> Also, the check below it, dealing with sym-xor, looks like it's only
>>   relevant to ETHTOOL_SRXFH, since info.data is garbage for other commands.
>>   Ahmed, is my understanding correct there?
>>
> 
> Speaking of the below check, the sanity check depends on the order of
> operations, for example:
> 1. Enable symmetric xor
> 2. Request hash on src only
> = Error as expected, however:

Correct. The check below is to make sure that no ntuple that does not 
cover symmetric fields is added if symm-xor is enabled.

> 
> 1. Request hash on src only
> 2. Enable symmetric xor
> = Success :(.
> 
> I've been thinking of improving the situation, but that requires
> iterating over all flow types on symmetric xor enablement and that feels
> quite bad..

and delete/disable filters? may be just a warning to the user that some 
filters are not symmetric.