Re: [PATCH v4 2/3] common/sfc_efx/base: add support to enable VLAN stripping

[Artemii Morozov <Artemii.Morozov@arknetworks.am>]

Hello,

On 6/2/23 12:32, Andrew Rybchenko wrote:
> On 6/1/23 18:30, Artemii Morozov wrote:
>> To enable VLAN stripping, two conditions must be met:
>> the corresponding flag must be set and the appropriate
>> RX prefix should be requested.
>
> RX -> Rx
>
>> VLAN stripping is supported for ef100 datapath only.
>
> When you read below notes carefully, you'll understand that the
> patch is very raw yet. There are too many questions below.
>
> The major decision to be made is if libefx API should enforce
> device level offload or should just provide transparent API and
> driver must be responsible for consistency.
>
> If driver must be responsible for consistency, don't try to
> enforce VLAN stripping enable via filter table. RxQ flags
> should control stripped VLAN delivery. Filter flag and default
> RxQ set flag (API should be extended) should control VLAN
> stripping enabling.
>
> If libefx must guarantee consistency, we need a new way to
> enable device level offload early (efx_rx_init()-like, may
> be a new API). If so, it should be impossible to control
> VLAN stripping per Rx filter. It still could be possible
> to control stripped VLAN delivery per RxQ.
>
> Anyway current solution is really inconsistent.

How about the following concept:

1. Add a new negotiated flag for metadata: RTE_ETH_RX_METADATA_VLAN_INFO.

2. Extend the driver to allow requesting the delivery of stripped VLAN 
TCI through the metadata
     negotiation method. This request will internally affect the Rx 
prefix configuration via
     libefx EFX_RXQ_FLAG_VLAN_TCI (or something like that).

3.  Set the corresponding boolean flag in the sfc_port(strip_vlan = 
something like that please advice)
      structure if RTE_ETH_RX_OFFLOAD_VLAN_STRIP is received. Map this 
flag to the corresponding flag in
      efx_nic_t, Then, when generating specs for filters, use the 
boolean flag from efx_nic_t to determine
      the VLAN stripping behavior.

4. Users can request VLAN strip action. If a user does not request this 
action, but the driver detects that
    device-level stripping has been requested, it may implicitly enable 
VLAN stripping for that specific flow
    within the efx_mcdi_filter_op_add function.

In this concept, we allow the enabling of device-level VLAN stripping. 
Points 1 and 2 concern the delivery of stripped VLAN TCI, while points 3 
and 4 pertain to the request for VLAN tag stripping.