Subject: Re: [Intel-wired-lan] [PATCH iwl-next v5 09/12] iavf: refactor iavf_clean_rx_irq to support legacy and flex descriptors

From: Rahul Rameshbabu <[email-masked]>
Date: Thu, 18 Apr 2024 13:00:40 -0700

On Thu, 18 Apr, 2024 01:24:57 -0400 Mateusz Polchlopek <[email-masked]> wrote:
> From: Jacob Keller <[email-masked]>
>
> Using VIRTCHNL_VF_OFFLOAD_FLEX_DESC, the iAVF driver is capable of
> negotiating to enable the advanced flexible descriptor layout. Add the
> flexible NIC layout (RXDID=2) as a member of the Rx descriptor union.
>
> Also add bit position definitions for the status and error indications
> that are needed.
>
> The iavf_clean_rx_irq function needs to extract a few fields from the Rx
> descriptor, including the size, rx_ptype, and vlan_tag.
> Move the extraction to a separate function that decodes the fields into
> a structure. This will reduce the burden for handling multiple
> descriptor types by keeping the relevant extraction logic in one place.
>
> To support handling an additional descriptor format with minimal code
> duplication, refactor Rx checksum handling so that the general logic
> is separated from the bit calculations. Introduce an iavf_rx_desc_decoded
> structure which holds the relevant bits decoded from the Rx descriptor.
> This will enable implementing flexible descriptor handling without
> duplicating the general logic twice.
>
> Introduce an iavf_extract_flex_rx_fields, iavf_flex_rx_hash, and
> iavf_flex_rx_csum functions which operate on the flexible NIC descriptor
> format instead of the legacy 32 byte format. Based on the negotiated
> RXDID, select the correct function for processing the Rx descriptors.
>
> With this change, the Rx hot path should be functional when using either
> the default legacy 32byte format or when we switch to the flexible NIC
> layout.
>
> Modify the Rx hot path to add support for the flexible descriptor
> format and add request enabling Rx timestamps for all queues.
>
> As in ice, make sure we bump the checksum level if the hardware detected
> a packet type which could have an outer checksum. This is important
> because hardware only verifies the inner checksum.
>
> Reviewed-by: Wojciech Drewek <[email-masked]>
> Signed-off-by: Jacob Keller <[email-masked]>
> Co-developed-by: Mateusz Polchlopek <[email-masked]>
> Signed-off-by: Mateusz Polchlopek <[email-masked]>
> ---
>  drivers/net/ethernet/intel/iavf/iavf_txrx.c   | 354 +++++++++++++-----
>  drivers/net/ethernet/intel/iavf/iavf_txrx.h   |   8 +
>  drivers/net/ethernet/intel/iavf/iavf_type.h   | 149 ++++++--
>  .../net/ethernet/intel/iavf/iavf_virtchnl.c   |   5 +
>  4 files changed, 390 insertions(+), 126 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/iavf/iavf_txrx.c b/drivers/net/ethernet/intel/iavf/iavf_txrx.c
<snip>
> +/**
> + * iavf_flex_rx_hash - set the hash value in the skb
> + * @ring: descriptor ring
> + * @rx_desc: specific descriptor
> + * @skb: skb currently being received and modified
> + * @rx_ptype: Rx packet type
> + *
> + * This function only operates on the VIRTCHNL_RXDID_2_FLEX_SQ_NIC flexible
> + * descriptor writeback format.
> + **/
> +static void iavf_flex_rx_hash(struct iavf_ring *ring,
> +			      union iavf_rx_desc *rx_desc,
> +			      struct sk_buff *skb, u16 rx_ptype)
> +{
> +	__le16 status0;
> +
> +	if (!(ring->netdev->features & NETIF_F_RXHASH))
> +		return;
> +
> +	status0 = rx_desc->flex_wb.status_error0;

Any reason to not convert rx_desc->flex_wb.status_error0 to
CPU-endianness for the bit check?

> +	if (status0 & cpu_to_le16(IAVF_RX_FLEX_DESC_STATUS0_RSS_VALID_M)) {
> +		u32 hash = le32_to_cpu(rx_desc->flex_wb.rss_hash);
> +
> +		skb_set_hash(skb, hash, iavf_ptype_to_htype(rx_ptype));
> +	}
> +}
<snip>
> +/**
> + * iavf_extract_flex_rx_fields - Extract fields from the Rx descriptor
> + * @rx_ring: rx descriptor ring
> + * @rx_desc: the descriptor to process
> + * @fields: storage for extracted values
> + *
> + * Decode the Rx descriptor and extract relevant information including the
> + * size, VLAN tag, Rx packet type, end of packet field and RXE field value.
> + *
> + * This function only operates on the VIRTCHNL_RXDID_2_FLEX_SQ_NIC flexible
> + * descriptor writeback format.
> + */
> +static void iavf_extract_flex_rx_fields(struct iavf_ring *rx_ring,
> +					union iavf_rx_desc *rx_desc,
> +					struct iavf_rx_extracted *fields)
> +{
> +	__le16 status0, status1, flexi_flags0;
> +
> +	fields->size = FIELD_GET(IAVF_RX_FLEX_DESC_PKT_LEN_M,
> +				 le16_to_cpu(rx_desc->flex_wb.pkt_len));
> +
> +	flexi_flags0 = rx_desc->flex_wb.ptype_flexi_flags0;
> +
> +	fields->rx_ptype = FIELD_GET(IAVF_RX_FLEX_DESC_PTYPE_M,
> +				     le16_to_cpu(flexi_flags0));
> +
> +	status0 = rx_desc->flex_wb.status_error0;
> +	if (status0 & cpu_to_le16(IAVF_RX_FLEX_DESC_STATUS0_L2TAG1P_M) &&
> +	    rx_ring->flags & IAVF_TXRX_FLAGS_VLAN_TAG_LOC_L2TAG1)
> +		fields->vlan_tag = le16_to_cpu(rx_desc->flex_wb.l2tag1);
> +
> +	status1 = rx_desc->flex_wb.status_error1;

Similar comment to previous in this function.

> +	if (status1 & cpu_to_le16(IAVF_RX_FLEX_DESC_STATUS1_L2TAG2P_M) &&
> +	    rx_ring->flags & IAVF_RXR_FLAGS_VLAN_TAG_LOC_L2TAG2_2)
> +		fields->vlan_tag = le16_to_cpu(rx_desc->flex_wb.l2tag2_2nd);
> +
> +	fields->end_of_packet = FIELD_GET(IAVF_RX_FLEX_DESC_STATUS_ERR0_EOP_BIT,
> +					  le16_to_cpu(status0));
> +	fields->rxe = FIELD_GET(IAVF_RX_FLEX_DESC_STATUS_ERR0_RXE_BIT,
> +				le16_to_cpu(status0));
> +}
> +
> +static void iavf_extract_rx_fields(struct iavf_ring *rx_ring,
> +				   union iavf_rx_desc *rx_desc,
> +				   struct iavf_rx_extracted *fields)
> +{
> +	if (rx_ring->rxdid == VIRTCHNL_RXDID_1_32B_BASE)
> +		iavf_extract_legacy_rx_fields(rx_ring, rx_desc, fields);
> +	else
> +		iavf_extract_flex_rx_fields(rx_ring, rx_desc, fields);
> +}
> +
<snip>

--
Thanks,

Rahul Rameshbabu