Re: [PATCH net-next 1/5] net: ethtool: only allow set_rxnfc with rss + ring_cookie if driver opts in

[Edward Cree <ecree.xilinx@gmail.com>]

On 25/11/2024 07:11, Gal Pressman wrote:
> On 13/11/2024 14:13, edward.cree@amd.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.

>> @@ -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?

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?