Re: [PATCH net] ice: always add legacy 32byte RXDID in supported_rxdids

[Jacob Keller <jacob.e.keller@intel.com>]

On 9/20/2023 4:54 AM, Michal Schmidt wrote:
> When the PF and VF drivers both support flexible rx descriptors and have
> negotiated the VIRTCHNL_VF_OFFLOAD_RX_FLEX_DESC capability, the VF driver
> queries the PF for the list of supported descriptor formats
> (VIRTCHNL_OP_GET_SUPPORTED_RXDIDS). The PF driver is supposed to set the
> supported_rxdids bits that correspond to the descriptor formats the
> firmware implements. The legacy 32-byte rx desc format is always
> supported, even though it is not expressed in GLFLXP_RXDID_FLAGS.
> 
> The ice driver does not advertise the legacy 32-byte rx desc support,
> which leads to this failure to bring up the VF using the Intel
> out-of-tree iavf driver:
>  iavf 0000:41:01.0: PF does not list support for default Rx descriptor format
>  ...
>  iavf 0000:41:01.0: PF returned error -5 (VIRTCHNL_STATUS_ERR_PARAM) to our request 6
> 
> The in-tree iavf driver does not expose this bug, because it does not
> yet implement VIRTCHNL_VF_OFFLOAD_RX_FLEX_DESC.
> 
> The ice driver must always set the ICE_RXDID_LEGACY_1 bit in
> supported_rxdids. The Intel out-of-tree ice driver and the ice driver in
> DPDK both do this.
> 
> I copied this piece of the code and the comment text from the Intel
> out-of-tree driver.
> 
> Fixes: e753df8fbca5 ("ice: Add support Flex RXD")
> Signed-off-by: Michal Schmidt <mschmidt@redhat.com>

Yep, this happens because of the way the feature interacts with
VIRTHCNL_VF_OFFLOAD_RX_FLEX_DESC and how that wasn't enabled in upstream
yet. Not sure how this got missed with the mentioned fixed commit but
probably a gap because the upstream iAVF didn't implement changing
descriptor format.

Thanks for fixing this!

-Jake

> ---
>  drivers/net/ethernet/intel/ice/ice_virtchnl.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/ice/ice_virtchnl.c b/drivers/net/ethernet/intel/ice/ice_virtchnl.c
> index b03426ac932b..db97353efd06 100644
> --- a/drivers/net/ethernet/intel/ice/ice_virtchnl.c
> +++ b/drivers/net/ethernet/intel/ice/ice_virtchnl.c
> @@ -2617,12 +2617,14 @@ static int ice_vc_query_rxdid(struct ice_vf *vf)
>  		goto err;
>  	}
>  
> -	/* Read flexiflag registers to determine whether the
> -	 * corresponding RXDID is configured and supported or not.
> -	 * Since Legacy 16byte descriptor format is not supported,
> -	 * start from Legacy 32byte descriptor.
> +	/* RXDIDs supported by DDP package can be read from the register
> +	 * to get the supported RXDID bitmap. But the legacy 32byte RXDID
> +	 * is not listed in DDP package, add it in the bitmap manually.
> +	 * Legacy 16byte descriptor is not supported.
>  	 */
> -	for (i = ICE_RXDID_LEGACY_1; i < ICE_FLEX_DESC_RXDID_MAX_NUM; i++) {
> +	rxdid->supported_rxdids |= BIT(ICE_RXDID_LEGACY_1);
> +
> +	for (i = ICE_RXDID_FLEX_NIC; i < ICE_FLEX_DESC_RXDID_MAX_NUM; i++) {
>  		regval = rd32(hw, GLFLXP_RXDID_FLAGS(i, 0));
>  		if ((regval >> GLFLXP_RXDID_FLAGS_FLEXIFLAG_4N_S)
>  			& GLFLXP_RXDID_FLAGS_FLEXIFLAG_4N_M)