Re: [PATCH 1/1] net/sfc: stop misuse of Rx ingress m-port metadata on EF100

[Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>]

On 3/9/23 07:11, Ivan Malov wrote:
> The driver supports representor functionality. In it,
> packets coming from VFs to the dedicated back-end Rx
> queue get demultiplexed into front-end Rx queues of
> representor ethdevs as per the per-packet metadata
> indicating logical HW ingress ports. On transmit,
> packets are provided with symmetrical metadata
> by front-end Tx queues, and the back-end queue
> transforms the data into so-called Tx override
> descriptors. These let the packets bypass flow
> lookup and go directly to the represented VFs.
> 
> However, in the Rx part, the driver extracts
> the said metadata on every HW Rx queue, that
> is, not just on the one used by representors
> Doing so leads to a buggy behaviour. It is
> revealed by operating testpmd as follows:
> 
> dpdk-testpmd -a 0000:c6:00.0 -a 0000:c6:00.1 -- -i
> 
> testpmd> flow create 0 transfer pattern port_representor \
>   port_id is 0 / end actions port_representor port_id 1 / end
> Flow rule #0 created
> 
> testpmd> set fwd io
> testpmd> start tx_first
> 
> testpmd> flow destroy 0 rule 0
> Flow rule #0 destroyed
> 
> testpmd> stop
> 
>    ---------------------- Forward statistics for port 0  -----------------
>    RX-packets: 19196498       RX-dropped: 0             RX-total: 19196498
>    TX-packets: 19196535       TX-dropped: 0             TX-total: 19196535
>    -----------------------------------------------------------------------
> 
>    ---------------------- Forward statistics for port 1  -----------------
>    RX-packets: 19196503       RX-dropped: 0             RX-total: 19196503
>    TX-packets: 19196530       TX-dropped: 0             TX-total: 19196530
>    -----------------------------------------------------------------------
> 
> In this scenario, two physical functions of the adapter
> do not have any corresponding "back-to-back" forwarder
> on peer host. Packets transmitted from port 0 can only
> be forwarded to port 1 by means of a special flow rule.
> 
> The flow rule indeed works, but destroying it does not
> stop forwarding. Port statistics carry on incrementing.
> 
> Also, it is apparent that forwarding in the opposite
> direction must not have worked in this case as the
> flow is meant to target only one of the directions.
> 
> Because of the bug, the first 32 mbufs received
> as a result of the flow rule operation have the
> said metadata present. In io mode, testpmd does
> not tamper with mbufs and passes them directly
> to transmit path, so this data remains in them
> instructing the PMD to override destinations
> of the packets via Tx option descriptors.
> 
> Expected behaviour is as follows:
> 
>    ---------------------- Forward statistics for port 0  -----------------
>    RX-packets: 0              RX-dropped: 0             RX-total: 0
>    TX-packets: 15787496       TX-dropped: 0             TX-total: 15787496
>    -----------------------------------------------------------------------
> 
>    ---------------------- Forward statistics for port 1  -----------------
>    RX-packets: 15787464       RX-dropped: 0             RX-total: 15787464
>    TX-packets: 32             TX-dropped: 0             TX-total: 32
>    -----------------------------------------------------------------------
> 
> These figures show the rule work only for one direction.
> Also, removing the flow shall cause forwarding to cease.
> 
> Provided patch fixes the bug accordingly.
> 
> Fixes: d0f981a3efd8 ("net/sfc: handle ingress mport in EF100 Rx prefix")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Ivan Malov <ivan.malov@arknetworks.am>
> Reviewed-by: Andy Moreton <amoreton@xilinx.com>
> ---
>   drivers/net/sfc/sfc_dp_rx.h    | 3 +++
>   drivers/net/sfc/sfc_ef100_rx.c | 3 ++-
>   drivers/net/sfc/sfc_rx.c       | 3 +++
>   3 files changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/sfc/sfc_dp_rx.h b/drivers/net/sfc/sfc_dp_rx.h
> index 246adbd87c..51a44bd034 100644
> --- a/drivers/net/sfc/sfc_dp_rx.h
> +++ b/drivers/net/sfc/sfc_dp_rx.h
> @@ -10,6 +10,8 @@
>   #ifndef _SFC_DP_RX_H
>   #define _SFC_DP_RX_H
>   
> +#include <stdbool.h>
> +
>   #include <rte_mempool.h>
>   #include <ethdev_driver.h>
>   
> @@ -27,6 +29,7 @@ extern "C" {
>    */
>   struct sfc_dp_rxq {
>   	struct sfc_dp_queue	dpq;
> +	bool			need_ingress_mport;

May be I'm late, but it is a wrong location for the
information. The information is EF100-specific, but
the structure is a generic one.

I'd say that corresponding flag should be set in rxq->flag
upon creation based on request in qcreate info and
cleared if Rx prefix does not support it. May be it
should be an error if we need the information, but Rx prefix
does not provide it.

>   };
>   
>   /** Datapath receive queue descriptor number limitations */
> diff --git a/drivers/net/sfc/sfc_ef100_rx.c b/drivers/net/sfc/sfc_ef100_rx.c
> index 16cd8524d3..c4d256b40d 100644
> --- a/drivers/net/sfc/sfc_ef100_rx.c
> +++ b/drivers/net/sfc/sfc_ef100_rx.c
> @@ -876,7 +876,8 @@ sfc_ef100_rx_qstart(struct sfc_dp_rxq *dp_rxq, unsigned int evq_read_ptr,
>   	else
>   		rxq->flags &= ~SFC_EF100_RXQ_USER_MARK;
>   
> -	if ((unsup_rx_prefix_fields &
> +	if (dp_rxq->need_ingress_mport &&
> +	    (unsup_rx_prefix_fields &
>   	     (1U << EFX_RX_PREFIX_FIELD_INGRESS_MPORT)) == 0)
>   		rxq->flags |= SFC_EF100_RXQ_INGRESS_MPORT;
>   	else
> diff --git a/drivers/net/sfc/sfc_rx.c b/drivers/net/sfc/sfc_rx.c
> index 5ea98187c3..3d3d7d42e3 100644
> --- a/drivers/net/sfc/sfc_rx.c
> +++ b/drivers/net/sfc/sfc_rx.c
> @@ -1265,6 +1265,9 @@ sfc_rx_qinit(struct sfc_adapter *sa, sfc_sw_index_t sw_index,
>   	if (rc != 0)
>   		goto fail_dp_rx_qcreate;
>   
> +	rxq_info->dp->need_ingress_mport =
> +		((rxq_info->type_flags & EFX_RXQ_FLAG_INGRESS_MPORT) != 0);
> +
>   	evq->dp_rxq = rxq_info->dp;
>   
>   	rxq_info->state = SFC_RXQ_INITIALIZED;