Re: [dpdk-dev] [PATCH v6 3/3] ixgbe: Add LRO support

[Vlad Zolotarov <vladz@cloudius-systems.com>]

On 03/09/15 21:07, Vlad Zolotarov wrote:
>      - Only x540 and 82599 devices support LRO.
>      - Add the appropriate HW configuration.
>      - Add RSC aware rx_pkt_burst() handlers:
>         - Implemented bulk allocation and non-bulk allocation versions.
>         - Add LRO-specific fields to rte_eth_rxmode, to rte_eth_dev_data
>           and to igb_rx_queue.
>         - Use the appropriate handler when LRO is requested.
>
> Signed-off-by: Vlad Zolotarov <vladz@cloudius-systems.com>
> ---
> New in v5:
>     - Put the RTE_ETHDEV_HAS_LRO_SUPPORT definition at the beginning of rte_ethdev.h.
>     - Removed the "TODO: Remove me" comment near RTE_ETHDEV_HAS_LRO_SUPPORT.
>
> New in v4:
>     - Define RTE_ETHDEV_HAS_LRO_SUPPORT in rte_ethdev.h instead of
>       RTE_ETHDEV_LRO_SUPPORT defined in config/common_linuxapp.
>
> New in v2:
>     - Removed rte_eth_dev_data.lro_bulk_alloc.
>     - Fixed a few styling and spelling issues.
> ---
>   lib/librte_ether/rte_ethdev.h       |   9 +-
>   lib/librte_pmd_ixgbe/ixgbe_ethdev.c |   6 +
>   lib/librte_pmd_ixgbe/ixgbe_ethdev.h |   5 +
>   lib/librte_pmd_ixgbe/ixgbe_rxtx.c   | 562 +++++++++++++++++++++++++++++++++++-
>   lib/librte_pmd_ixgbe/ixgbe_rxtx.h   |   6 +
>   5 files changed, 581 insertions(+), 7 deletions(-)
>
> diff --git a/lib/librte_ether/rte_ethdev.h b/lib/librte_ether/rte_ethdev.h
> index 8db3127..44f081f 100644
> --- a/lib/librte_ether/rte_ethdev.h
> +++ b/lib/librte_ether/rte_ethdev.h
> @@ -172,6 +172,9 @@ extern "C" {
>   
>   #include <stdint.h>
>   
> +/* Use this macro to check if LRO API is supported */
> +#define RTE_ETHDEV_HAS_LRO_SUPPORT
> +
>   #include <rte_log.h>
>   #include <rte_interrupts.h>
>   #include <rte_pci.h>
> @@ -320,14 +323,15 @@ struct rte_eth_rxmode {
>   	enum rte_eth_rx_mq_mode mq_mode;
>   	uint32_t max_rx_pkt_len;  /**< Only used if jumbo_frame enabled. */
>   	uint16_t split_hdr_size;  /**< hdr buf size (header_split enabled).*/
> -	uint8_t header_split : 1, /**< Header Split enable. */
> +	uint16_t header_split : 1, /**< Header Split enable. */
>   		hw_ip_checksum   : 1, /**< IP/UDP/TCP checksum offload enable. */
>   		hw_vlan_filter   : 1, /**< VLAN filter enable. */
>   		hw_vlan_strip    : 1, /**< VLAN strip enable. */
>   		hw_vlan_extend   : 1, /**< Extended VLAN enable. */
>   		jumbo_frame      : 1, /**< Jumbo Frame Receipt enable. */
>   		hw_strip_crc     : 1, /**< Enable CRC stripping by hardware. */
> -		enable_scatter   : 1; /**< Enable scatter packets rx handler */
> +		enable_scatter   : 1, /**< Enable scatter packets rx handler */
> +		enable_lro       : 1; /**< Enable LRO */
>   };
>   
>   /**
> @@ -1515,6 +1519,7 @@ struct rte_eth_dev_data {
>   	uint8_t port_id;           /**< Device [external] port identifier. */
>   	uint8_t promiscuous   : 1, /**< RX promiscuous mode ON(1) / OFF(0). */
>   		scattered_rx : 1,  /**< RX of scattered packets is ON(1) / OFF(0) */
> +		lro          : 1,  /**< RX LRO is ON(1) / OFF(0) */
>   		all_multicast : 1, /**< RX all multicast mode ON(1) / OFF(0). */
>   		dev_started : 1;   /**< Device state: STARTED(1) / STOPPED(0). */
>   };
> diff --git a/lib/librte_pmd_ixgbe/ixgbe_ethdev.c b/lib/librte_pmd_ixgbe/ixgbe_ethdev.c
> index 9d3de1a..765174d 100644
> --- a/lib/librte_pmd_ixgbe/ixgbe_ethdev.c
> +++ b/lib/librte_pmd_ixgbe/ixgbe_ethdev.c
> @@ -1648,6 +1648,7 @@ ixgbe_dev_stop(struct rte_eth_dev *dev)
>   
>   	/* Clear stored conf */
>   	dev->data->scattered_rx = 0;
> +	dev->data->lro = 0;
>   	hw->rx_bulk_alloc_allowed = false;
>   	hw->rx_vec_allowed = false;
>   
> @@ -2018,6 +2019,11 @@ ixgbe_dev_info_get(struct rte_eth_dev *dev, struct rte_eth_dev_info *dev_info)
>   		DEV_RX_OFFLOAD_IPV4_CKSUM |
>   		DEV_RX_OFFLOAD_UDP_CKSUM  |
>   		DEV_RX_OFFLOAD_TCP_CKSUM;
> +
> +	if (hw->mac.type == ixgbe_mac_82599EB ||
> +	    hw->mac.type == ixgbe_mac_X540)
> +		dev_info->rx_offload_capa |= DEV_RX_OFFLOAD_TCP_LRO;
> +
>   	dev_info->tx_offload_capa =
>   		DEV_TX_OFFLOAD_VLAN_INSERT |
>   		DEV_TX_OFFLOAD_IPV4_CKSUM  |
> diff --git a/lib/librte_pmd_ixgbe/ixgbe_ethdev.h b/lib/librte_pmd_ixgbe/ixgbe_ethdev.h
> index a549f5c..e206584 100644
> --- a/lib/librte_pmd_ixgbe/ixgbe_ethdev.h
> +++ b/lib/librte_pmd_ixgbe/ixgbe_ethdev.h
> @@ -349,6 +349,11 @@ uint16_t ixgbe_recv_pkts_bulk_alloc(void *rx_queue, struct rte_mbuf **rx_pkts,
>   uint16_t ixgbe_recv_scattered_pkts(void *rx_queue,
>   		struct rte_mbuf **rx_pkts, uint16_t nb_pkts);
>   
> +uint16_t ixgbe_recv_pkts_lro(void *rx_queue,
> +		struct rte_mbuf **rx_pkts, uint16_t nb_pkts);
> +uint16_t ixgbe_recv_pkts_lro_bulk_alloc(void *rx_queue,
> +		struct rte_mbuf **rx_pkts, uint16_t nb_pkts);
> +
>   uint16_t ixgbe_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
>   		uint16_t nb_pkts);
>   
> diff --git a/lib/librte_pmd_ixgbe/ixgbe_rxtx.c b/lib/librte_pmd_ixgbe/ixgbe_rxtx.c
> index 58e619b..944c662 100644
> --- a/lib/librte_pmd_ixgbe/ixgbe_rxtx.c
> +++ b/lib/librte_pmd_ixgbe/ixgbe_rxtx.c
> @@ -1366,6 +1366,15 @@ ixgbe_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
>   }
>   
>   /**
> + * Detect an RSC descriptor.
> + */
> +static inline uint32_t ixgbe_rsc_count(union ixgbe_adv_rx_desc *rx)
> +{
> +	return (rte_le_to_cpu_32(rx->wb.lower.lo_dword.data) &
> +		IXGBE_RXDADV_RSCCNT_MASK) >> IXGBE_RXDADV_RSCCNT_SHIFT;
> +}
> +
> +/**
>    * Initialize the first mbuf of the returned packet:
>    *    - RX port identifier,
>    *    - hardware offload data, if any:
> @@ -1410,6 +1419,291 @@ static inline void ixgbe_fill_cluster_head_buf(
>   	}
>   }
>   
> +/**
> + * Bulk receive handler for and LRO case.
> + *
> + * @rx_queue Rx queue handle
> + * @rx_pkts table of received packets
> + * @nb_pkts size of rx_pkts table
> + * @bulk_alloc if TRUE bulk allocation is used for a HW ring refilling
> + *
> + * Handles the Rx HW ring completions when RSC feature is configured. Uses an
> + * additional ring of igb_rsc_entry's that will hold the relevant RSC info.
> + *
> + * We use the same logic as in Lunux and in FreeBSD ixgbe drivers:
> + * 1) When non-EOP RSC completion arrives:
> + *    a) Update the HEAD of the current RSC aggregation cluster with the new
> + *       segment's data length.
> + *    b) Set the "next" pointer of the current segment to point to the segment
> + *       at the NEXTP index.
> + *    c) Pass the HEAD of RSC aggregation cluster on to the next NEXTP entry
> + *       in the sw_rsc_ring.
> + * 2) When EOP arrives we just update the cluster's total length and offload
> + *    flags and deliver the cluster up to the upper layers. In our case - put it
> + *    in the rx_pkts table.
> + *
> + * Returns the number of received packets/clusters (according to the "bulk
> + * receive" interface).
> + */
> +static inline uint16_t
> +_recv_pkts_lro(void *rx_queue, struct rte_mbuf **rx_pkts, uint16_t nb_pkts,
> +	       bool bulk_alloc)
> +{
> +	struct igb_rx_queue *rxq = rx_queue;
> +	volatile union ixgbe_adv_rx_desc *rx_ring = rxq->rx_ring;
> +	struct igb_rx_entry *sw_ring = rxq->sw_ring;
> +	struct igb_rsc_entry *sw_rsc_ring = rxq->sw_rsc_ring;
> +	uint16_t rx_id = rxq->rx_tail;
> +	uint16_t nb_rx = 0;
> +	uint16_t nb_hold = rxq->nb_rx_hold;
> +	uint16_t prev_id = rxq->rx_tail;
> +
> +	while (nb_rx < nb_pkts) {
> +		bool eop;
> +		struct igb_rx_entry *rxe;
> +		struct igb_rsc_entry *rsc_entry;
> +		struct igb_rsc_entry *next_rsc_entry;
> +		struct igb_rx_entry *next_rxe;
> +		struct rte_mbuf *first_seg;
> +		struct rte_mbuf *rxm;
> +		struct rte_mbuf *nmb;
> +		union ixgbe_adv_rx_desc rxd;
> +		uint16_t data_len;
> +		uint16_t next_id;
> +		volatile union ixgbe_adv_rx_desc *rxdp;
> +		uint32_t staterr;
> +
> +next_desc:
> +		/*
> +		 * The code in this whole file uses the volatile pointer to
> +		 * ensure the read ordering of the status and the rest of the
> +		 * descriptor fields (on the compiler level only!!!). This is so
> +		 * UGLY - why not to just use the compiler barrier instead? DPDK
> +		 * even has the rte_compiler_barrier() for that.
> +		 *
> +		 * But most importantly this is just wrong because this doesn't
> +		 * ensure memory ordering in a general case at all. For
> +		 * instance, DPDK is supposed to work on Power CPUs where
> +		 * compiler barrier may just not be enough!
> +		 *
> +		 * I tried to write only this function properly to have a
> +		 * starting point (as a part of an LRO/RSC series) but the
> +		 * compiler cursed at me when I tried to cast away the
> +		 * "volatile" from rx_ring (yes, it's volatile too!!!). So, I'm
> +		 * keeping it the way it is for now.
> +		 *
> +		 * The code in this file is broken in so many other places and
> +		 * will just not work on a big endian CPU anyway therefore the
> +		 * lines below will have to be revisited together with the rest
> +		 * of the ixgbe PMD.
> +		 *
> +		 * TODO:
> +		 *    - Get rid of "volatile" crap and let the compiler do its
> +		 *      job.
> +		 *    - Use the proper memory barrier (rte_rmb()) to ensure the
> +		 *      memory ordering below.
> +		 */
> +		rxdp = &rx_ring[rx_id];
> +		staterr = rte_le_to_cpu_32(rxdp->wb.upper.status_error);
> +
> +		if (!(staterr & IXGBE_RXDADV_STAT_DD))
> +			break;
> +
> +		rxd = *rxdp;
> +
> +		PMD_RX_LOG(DEBUG, "port_id=%u queue_id=%u rx_id=%u "
> +				  "staterr=0x%x data_len=%u",
> +			   rxq->port_id, rxq->queue_id, rx_id, staterr,
> +			   rte_le_to_cpu_16(rxd.wb.upper.length));
> +
> +		if (!bulk_alloc) {
> +			nmb = rte_rxmbuf_alloc(rxq->mb_pool);
> +			if (nmb == NULL) {
> +				PMD_RX_LOG(DEBUG, "RX mbuf alloc failed "
> +						  "port_id=%u queue_id=%u",
> +					   rxq->port_id, rxq->queue_id);
> +
> +				rte_eth_devices[rxq->port_id].data->
> +							rx_mbuf_alloc_failed++;
> +				break;
> +			}
> +		} else if (nb_hold > rxq->rx_free_thresh) {
> +			uint16_t next_rdt = rxq->rx_free_trigger;
> +
> +			if (!ixgbe_rx_alloc_bufs(rxq, false)) {
> +				rte_wmb();
> +				IXGBE_PCI_REG_WRITE(rxq->rdt_reg_addr,
> +						    next_rdt);
> +				nb_hold -= rxq->rx_free_thresh;
> +			} else {
> +				PMD_RX_LOG(DEBUG, "RX bulk alloc failed "
> +						  "port_id=%u queue_id=%u",
> +					   rxq->port_id, rxq->queue_id);
> +
> +				rte_eth_devices[rxq->port_id].data->
> +							rx_mbuf_alloc_failed++;
> +				break;
> +			}
> +		}
> +
> +		nb_hold++;
> +		rxe = &sw_ring[rx_id];
> +		eop = staterr & IXGBE_RXDADV_STAT_EOP;
> +
> +		next_id = rx_id + 1;
> +		if (next_id == rxq->nb_rx_desc)
> +			next_id = 0;
> +
> +		/* Prefetch next mbuf while processing current one. */
> +		rte_ixgbe_prefetch(sw_ring[next_id].mbuf);
> +
> +		/*
> +		 * When next RX descriptor is on a cache-line boundary,
> +		 * prefetch the next 4 RX descriptors and the next 4 pointers
> +		 * to mbufs.
> +		 */
> +		if ((next_id & 0x3) == 0) {
> +			rte_ixgbe_prefetch(&rx_ring[next_id]);
> +			rte_ixgbe_prefetch(&sw_ring[next_id]);
> +		}
> +
> +		rxm = rxe->mbuf;
> +
> +		if (!bulk_alloc) {
> +			__le64 dma =
> +			  rte_cpu_to_le_64(RTE_MBUF_DATA_DMA_ADDR_DEFAULT(nmb));
> +			/*
> +			 * Update RX descriptor with the physical address of the
> +			 * new data buffer of the new allocated mbuf.
> +			 */
> +			rxe->mbuf = nmb;
> +
> +			rxm->data_off = RTE_PKTMBUF_HEADROOM;
> +			rxdp->read.hdr_addr = dma;
> +			rxdp->read.pkt_addr = dma;
> +		}
> +		/*
> +		 * Set data length & data buffer address of mbuf.
> +		 */
> +		data_len = rte_le_to_cpu_16(rxd.wb.upper.length);
> +		rxm->data_len = data_len;
> +
> +		if (!eop) {
> +			uint16_t nextp_id;
> +			/*
> +			 * Get next descriptor index:
> +			 *  - For RSC it's in the NEXTP field.
> +			 *  - For a scattered packet - it's just a following
> +			 *    descriptor.
> +			 */
> +			if (ixgbe_rsc_count(&rxd))
> +				nextp_id =
> +					(staterr & IXGBE_RXDADV_NEXTP_MASK) >>
> +						       IXGBE_RXDADV_NEXTP_SHIFT;
> +			else
> +				nextp_id = next_id;
> +
> +			next_rsc_entry = &sw_rsc_ring[nextp_id];
> +			next_rxe = &sw_ring[nextp_id];
> +			rte_ixgbe_prefetch(next_rxe);
> +		}
> +
> +		rsc_entry = &sw_rsc_ring[rx_id];
> +		first_seg = rsc_entry->fbuf;
> +		rsc_entry->fbuf = NULL;
> +
> +		/*
> +		 * If this is the first buffer of the received packet,
> +		 * set the pointer to the first mbuf of the packet and
> +		 * initialize its context.
> +		 * Otherwise, update the total length and the number of segments
> +		 * of the current scattered packet, and update the pointer to
> +		 * the last mbuf of the current packet.
> +		 */
> +		if (first_seg == NULL) {
> +			first_seg = rxm;
> +			first_seg->pkt_len = data_len;
> +			first_seg->nb_segs = 1;
> +		} else {
> +			first_seg->pkt_len += data_len;
> +			first_seg->nb_segs++;
> +		}
> +
> +		prev_id = rx_id;
> +		rx_id = next_id;
> +
> +		/*
> +		 * If this is not the last buffer of the received packet, update
> +		 * the pointer to the first mbuf at the NEXTP entry in the
> +		 * sw_rsc_ring and continue to parse the RX ring.
> +		 */
> +		if (!eop) {
> +			rxm->next = next_rxe->mbuf;
> +			next_rsc_entry->fbuf = first_seg;
> +			goto next_desc;
> +		}
> +
> +		/*
> +		 * This is the last buffer of the received packet - return
> +		 * the current cluster to the user.
> +		 */
> +		rxm->next = NULL;
> +
> +		/* Initialize the first mbuf of the returned packet */
> +		ixgbe_fill_cluster_head_buf(first_seg, &rxd, rxq->port_id,
> +					    staterr);
> +
> +		/* Prefetch data of first segment, if configured to do so. */
> +		rte_packet_prefetch((char *)first_seg->buf_addr +
> +			first_seg->data_off);
> +
> +		/*
> +		 * Store the mbuf address into the next entry of the array
> +		 * of returned packets.
> +		 */
> +		rx_pkts[nb_rx++] = first_seg;
> +	}
> +
> +	/*
> +	 * Record index of the next RX descriptor to probe.
> +	 */
> +	rxq->rx_tail = rx_id;
> +
> +	/*
> +	 * If the number of free RX descriptors is greater than the RX free
> +	 * threshold of the queue, advance the Receive Descriptor Tail (RDT)
> +	 * register.
> +	 * Update the RDT with the value of the last processed RX descriptor
> +	 * minus 1, to guarantee that the RDT register is never equal to the
> +	 * RDH register, which creates a "full" ring situtation from the
> +	 * hardware point of view...
> +	 */
> +	if (!bulk_alloc && nb_hold > rxq->rx_free_thresh) {
> +		PMD_RX_LOG(DEBUG, "port_id=%u queue_id=%u rx_tail=%u "
> +			   "nb_hold=%u nb_rx=%u",
> +			   rxq->port_id, rxq->queue_id, rx_id, nb_hold, nb_rx);
> +
> +		IXGBE_PCI_REG_WRITE(rxq->rdt_reg_addr, prev_id);
> +		nb_hold = 0;
> +	}
> +
> +	rxq->nb_rx_hold = nb_hold;
> +	return nb_rx;
> +}
> +
> +uint16_t
> +ixgbe_recv_pkts_lro(void *rx_queue, struct rte_mbuf **rx_pkts, uint16_t nb_pkts)
> +{
> +	return _recv_pkts_lro(rx_queue, rx_pkts, nb_pkts, false);
> +}
> +
> +uint16_t
> +ixgbe_recv_pkts_lro_bulk_alloc(void *rx_queue, struct rte_mbuf **rx_pkts,
> +			       uint16_t nb_pkts)
> +{
> +	return _recv_pkts_lro(rx_queue, rx_pkts, nb_pkts, true);
> +}
> +
>   uint16_t
>   ixgbe_recv_scattered_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
>   			  uint16_t nb_pkts)
> @@ -2024,6 +2318,7 @@ ixgbe_rx_queue_release(struct igb_rx_queue *rxq)
>   	if (rxq != NULL) {
>   		ixgbe_rx_queue_release_mbufs(rxq);
>   		rte_free(rxq->sw_ring);
> +		rte_free(rxq->sw_rsc_ring);
>   		rte_free(rxq);
>   	}
>   }
> @@ -2146,6 +2441,7 @@ ixgbe_reset_rx_queue(struct ixgbe_hw *hw, struct igb_rx_queue *rxq)
>   	rxq->nb_rx_hold = 0;
>   	rxq->pkt_first_seg = NULL;
>   	rxq->pkt_last_seg = NULL;
> +	rxq->rsc_en = 0;
>   }
>   
>   int
> @@ -2160,6 +2456,14 @@ ixgbe_dev_rx_queue_setup(struct rte_eth_dev *dev,
>   	struct igb_rx_queue *rxq;
>   	struct ixgbe_hw     *hw;
>   	uint16_t len;
> +	struct rte_eth_dev_info dev_info = { 0 };
> +	struct rte_eth_rxmode *dev_rx_mode = &dev->data->dev_conf.rxmode;
> +	bool rsc_requested = false;
> +
> +	dev->dev_ops->dev_infos_get(dev, &dev_info);
> +	if ((dev_info.rx_offload_capa & DEV_RX_OFFLOAD_TCP_LRO) &&
> +	    dev_rx_mode->enable_lro)
> +		rsc_requested = true;
>   
>   	PMD_INIT_FUNC_TRACE();
>   	hw = IXGBE_DEV_PRIVATE_TO_HW(dev->data->dev_private);
> @@ -2265,12 +2569,28 @@ ixgbe_dev_rx_queue_setup(struct rte_eth_dev *dev,
>   	rxq->sw_ring = rte_zmalloc_socket("rxq->sw_ring",
>   					  sizeof(struct igb_rx_entry) * len,
>   					  RTE_CACHE_LINE_SIZE, socket_id);
> -	if (rxq->sw_ring == NULL) {
> +	if (!rxq->sw_ring) {
>   		ixgbe_rx_queue_release(rxq);
>   		return (-ENOMEM);
>   	}
> -	PMD_INIT_LOG(DEBUG, "sw_ring=%p hw_ring=%p dma_addr=0x%"PRIx64,
> -		     rxq->sw_ring, rxq->rx_ring, rxq->rx_ring_phys_addr);
> +
> +	if (rsc_requested) {
> +		rxq->sw_rsc_ring =
> +			rte_zmalloc_socket("rxq->sw_rsc_ring",
> +					   sizeof(struct igb_rsc_entry) * len,
> +					   RTE_CACHE_LINE_SIZE, socket_id);
> +		if (!rxq->sw_rsc_ring) {
> +			ixgbe_rx_queue_release(rxq);
> +			return (-ENOMEM);
> +		}
> +	} else {
> +		rxq->sw_rsc_ring = NULL;
> +	}
> +
> +	PMD_INIT_LOG(DEBUG, "sw_ring=%p sw_rsc_ring=%p hw_ring=%p "
> +			    "dma_addr=0x%"PRIx64,
> +		     rxq->sw_ring, rxq->sw_rsc_ring, rxq->rx_ring,
> +		     rxq->rx_ring_phys_addr);
>   
>   	if (!rte_is_power_of_2(nb_desc)) {
>   		PMD_INIT_LOG(DEBUG, "queue[%d] doesn't meet Vector Rx "
> @@ -3515,6 +3835,84 @@ ixgbe_dev_mq_tx_configure(struct rte_eth_dev *dev)
>   	return 0;
>   }
>   
> +/**
> + * get_rscctl_maxdesc - Calculate the RSCCTL[n].MAXDESC for PF
> + *
> + * Return the RSCCTL[n].MAXDESC for 82599 and x540 PF devices according to the
> + * spec rev. 3.0 chapter 8.2.3.8.13.
> + *
> + * @pool Memory pool of the Rx queue
> + */
> +static inline uint32_t get_rscctl_maxdesc(struct rte_mempool *pool)
> +{
> +	struct rte_pktmbuf_pool_private *mp_priv = rte_mempool_get_priv(pool);
> +
> +	/* MAXDESC * SRRCTL.BSIZEPKT must not exceed 64 KB minus one */
> +	uint16_t maxdesc =
> +		65535 / (mp_priv->mbuf_data_room_size - RTE_PKTMBUF_HEADROOM);
> +
> +	if (maxdesc >= 16)
> +		return IXGBE_RSCCTL_MAXDESC_16;
> +	else if (maxdesc >= 8)
> +		return IXGBE_RSCCTL_MAXDESC_8;
> +	else if (maxdesc >= 4)
> +		return IXGBE_RSCCTL_MAXDESC_4;
> +	else
> +		return IXGBE_RSCCTL_MAXDESC_1;
> +}
> +
> +/* (Taken from FreeBSD tree)
> +** Setup the correct IVAR register for a particular MSIX interrupt
> +**   (yes this is all very magic and confusing :)
> +**  - entry is the register array entry
> +**  - vector is the MSIX vector for this queue
> +**  - type is RX/TX/MISC
> +*/
> +static void
> +ixgbe_set_ivar(struct rte_eth_dev *dev, u8 entry, u8 vector, s8 type)
> +{
> +	struct ixgbe_hw *hw = IXGBE_DEV_PRIVATE_TO_HW(dev->data->dev_private);
> +	u32 ivar, index;
> +
> +	vector |= IXGBE_IVAR_ALLOC_VAL;
> +
> +	switch (hw->mac.type) {
> +
> +	case ixgbe_mac_82598EB:
> +		if (type == -1)
> +			entry = IXGBE_IVAR_OTHER_CAUSES_INDEX;
> +		else
> +			entry += (type * 64);
> +		index = (entry >> 2) & 0x1F;
> +		ivar = IXGBE_READ_REG(hw, IXGBE_IVAR(index));
> +		ivar &= ~(0xFF << (8 * (entry & 0x3)));
> +		ivar |= (vector << (8 * (entry & 0x3)));
> +		IXGBE_WRITE_REG(hw, IXGBE_IVAR(index), ivar);
> +		break;
> +
> +	case ixgbe_mac_82599EB:
> +	case ixgbe_mac_X540:
> +		if (type == -1) { /* MISC IVAR */
> +			index = (entry & 1) * 8;
> +			ivar = IXGBE_READ_REG(hw, IXGBE_IVAR_MISC);
> +			ivar &= ~(0xFF << index);
> +			ivar |= (vector << index);
> +			IXGBE_WRITE_REG(hw, IXGBE_IVAR_MISC, ivar);
> +		} else {	/* RX/TX IVARS */
> +			index = (16 * (entry & 1)) + (8 * type);
> +			ivar = IXGBE_READ_REG(hw, IXGBE_IVAR(entry >> 1));
> +			ivar &= ~(0xFF << index);
> +			ivar |= (vector << index);
> +			IXGBE_WRITE_REG(hw, IXGBE_IVAR(entry >> 1), ivar);
> +		}
> +
> +		break;
> +
> +	default:
> +		break;
> +	}
> +}
> +
>   void set_rx_function(struct rte_eth_dev *dev)
>   {
>   	struct ixgbe_hw *hw = IXGBE_DEV_PRIVATE_TO_HW(dev->data->dev_private);
> @@ -3565,6 +3963,25 @@ void set_rx_function(struct rte_eth_dev *dev)
>   			dev->rx_pkt_burst = ixgbe_recv_scattered_pkts;
>   		}
>   	}
> +
> +	/*
> +	 * Initialize the appropriate LRO callback.
> +	 *
> +	 * If all queues satisfy the bulk allocation preconditions
> +	 * (hw->rx_bulk_alloc_allowed is TRUE) then we may use bulk allocation.
> +	 * Otherwise use a single allocation version.
> +	 */
> +	if (dev->data->lro) {
> +		if (hw->rx_bulk_alloc_allowed) {
> +			PMD_INIT_LOG(INFO, "LRO is requested. Using a bulk "
> +					   "allocation version");
> +			dev->rx_pkt_burst = ixgbe_recv_pkts_lro_bulk_alloc;
> +		} else {
> +			PMD_INIT_LOG(INFO, "LRO is requested. Using a single "
> +					   "allocation version");
> +			dev->rx_pkt_burst = ixgbe_recv_pkts_lro;
> +		}
> +	}
>   }
>   
>   /*
> @@ -3583,10 +4000,26 @@ ixgbe_dev_rx_init(struct rte_eth_dev *dev)
>   	uint32_t maxfrs;
>   	uint32_t srrctl;
>   	uint32_t rdrxctl;
> +	uint32_t rscctl;
> +	uint32_t psrtype;
> +	uint32_t rfctl;
>   	uint32_t rxcsum;
>   	uint16_t buf_size;
>   	uint16_t i;
>   	struct rte_eth_rxmode *rx_conf = &dev->data->dev_conf.rxmode;
> +	struct rte_eth_dev_info dev_info = { 0 };
> +	bool rsc_capable = false;
> +
> +	/* Sanity check */
> +	dev->dev_ops->dev_infos_get(dev, &dev_info);
> +	if (dev_info.rx_offload_capa & DEV_RX_OFFLOAD_TCP_LRO)
> +		rsc_capable = true;
> +
> +	if (!rsc_capable && rx_conf->enable_lro) {
> +		PMD_INIT_LOG(CRIT, "LRO is requested on HW that doesn't "
> +				   "support it");
> +		return -EINVAL;
> +	}
>   
>   	PMD_INIT_FUNC_TRACE();
>   	hw = IXGBE_DEV_PRIVATE_TO_HW(dev->data->dev_private);
> @@ -3606,13 +4039,44 @@ ixgbe_dev_rx_init(struct rte_eth_dev *dev)
>   	IXGBE_WRITE_REG(hw, IXGBE_FCTRL, fctrl);
>   
>   	/*
> +	 * RFCTL configuration
> +	 *
> +	 * Since NFS packets coalescing is not supported - clear RFCTL.NFSW_DIS
> +	 * and RFCTL.NFSR_DIS when RSC is enabled.
> +	 */
> +	if (rsc_capable) {
> +		rfctl = IXGBE_READ_REG(hw, IXGBE_RFCTL);
> +		if (rx_conf->enable_lro) {
> +			rfctl &= ~(IXGBE_RFCTL_RSC_DIS | IXGBE_RFCTL_NFSW_DIS |
> +				   IXGBE_RFCTL_NFSR_DIS);
> +		} else {
> +			rfctl |= IXGBE_RFCTL_RSC_DIS;
> +		}
> +
> +		IXGBE_WRITE_REG(hw, IXGBE_RFCTL, rfctl);
> +	}
> +
> +
> +	/*
>   	 * Configure CRC stripping, if any.
>   	 */
>   	hlreg0 = IXGBE_READ_REG(hw, IXGBE_HLREG0);
>   	if (rx_conf->hw_strip_crc)
>   		hlreg0 |= IXGBE_HLREG0_RXCRCSTRP;
> -	else
> +	else {
>   		hlreg0 &= ~IXGBE_HLREG0_RXCRCSTRP;
> +		if (rx_conf->enable_lro) {
> +			/*
> +			 * According to chapter of 4.6.7.2.1 of the Spec Rev.
> +			 * 3.0 RSC configuration requires HW CRC stripping being
> +			 * enabled. If user requested both HW CRC stripping off
> +			 * and RSC on - return an error.
> +			 */
> +			PMD_INIT_LOG(CRIT, "LRO can't be enabled when HW CRC "
> +					    "is disabled");
> +			return -EINVAL;
> +		}
> +	}
>   
>   	/*
>   	 * Configure jumbo frame support, if any.
> @@ -3664,9 +4128,18 @@ ixgbe_dev_rx_init(struct rte_eth_dev *dev)
>   		 * Configure Header Split
>   		 */
>   		if (rx_conf->header_split) {
> +			/*
> +			 * Print a warning if split_hdr_size is less
> +			 * than 128 bytes when RSC is requested.
> +			 */
> +			if (rx_conf->enable_lro &&
> +			    rx_conf->split_hdr_size < 128)
> +				PMD_INIT_LOG(INFO, "split_hdr_size less than "
> +						   "128 bytes (%d)!",
> +					     rx_conf->split_hdr_size);
> +
>   			if (hw->mac.type == ixgbe_mac_82599EB) {
>   				/* Must setup the PSRTYPE register */
> -				uint32_t psrtype;
>   				psrtype = IXGBE_PSRTYPE_TCPHDR |
>   					IXGBE_PSRTYPE_UDPHDR   |
>   					IXGBE_PSRTYPE_IPV4HDR  |
> @@ -3679,7 +4152,20 @@ ixgbe_dev_rx_init(struct rte_eth_dev *dev)
>   			srrctl |= IXGBE_SRRCTL_DESCTYPE_HDR_SPLIT_ALWAYS;
>   		} else
>   #endif
> +		{
>   			srrctl = IXGBE_SRRCTL_DESCTYPE_ADV_ONEBUF;
> +			/*
> +			 * Following the 4.6.7.2.1 chapter of the 82599/x540
> +			 * Spec if RSC is enabled the SRRCTL[n].BSIZEHEADER
> +			 * should be configured even if header split is not
> +			 * enabled. In the later case we will configure it 128
> +			 * bytes following the recommendation in the spec.
> +			 */
> +			if (rx_conf->enable_lro)
> +				srrctl |=
> +				     ((128 << IXGBE_SRRCTL_BSIZEHDRSIZE_SHIFT) &
> +						    IXGBE_SRRCTL_BSIZEHDR_MASK);
> +		}
>   
>   		/* Set if packets are dropped when no descriptors available */
>   		if (rxq->drop_en)
> @@ -3696,6 +4182,13 @@ ixgbe_dev_rx_init(struct rte_eth_dev *dev)
>   				       RTE_PKTMBUF_HEADROOM);
>   		srrctl |= ((buf_size >> IXGBE_SRRCTL_BSIZEPKT_SHIFT) &
>   			   IXGBE_SRRCTL_BSIZEPKT_MASK);
> +
> +		/*
> +		 * TODO: Consider setting the Receive Descriptor Minimum
> +		 * Threshold Size for and RSC case. This is not an obviously
> +		 * beneficiary option but the one worth considering...
> +		 */
> +
>   		IXGBE_WRITE_REG(hw, IXGBE_SRRCTL(rxq->reg_idx), srrctl);
>   
>   		buf_size = (uint16_t) ((srrctl & IXGBE_SRRCTL_BSIZEPKT_MASK) <<
> @@ -3705,11 +4198,57 @@ ixgbe_dev_rx_init(struct rte_eth_dev *dev)
>   		if (dev->data->dev_conf.rxmode.max_rx_pkt_len +
>   					    2 * IXGBE_VLAN_TAG_SIZE > buf_size)
>   			dev->data->scattered_rx = 1;
> +
> +		/* RSC per-queue configuration */
> +		if (rx_conf->enable_lro) {
> +			uint32_t eitr;
> +
> +			rscctl =
> +				IXGBE_READ_REG(hw, IXGBE_RSCCTL(rxq->reg_idx));
> +			psrtype =
> +				IXGBE_READ_REG(hw, IXGBE_PSRTYPE(rxq->reg_idx));
> +			eitr = IXGBE_READ_REG(hw, IXGBE_EITR(rxq->reg_idx));
> +
> +			rscctl |= IXGBE_RSCCTL_RSCEN;
> +			rscctl |= get_rscctl_maxdesc(rxq->mb_pool);
> +			psrtype |= IXGBE_PSRTYPE_TCPHDR;
> +
> +			/*
> +			 * RSC: Set ITR interval corresponding to 2K ints/s.
> +			 *
> +			 * Full-sized RSC aggregations for a 10Gb/s link will
> +			 * arrive at about 20K aggregation/s rate.
> +			 *
> +			 * 2K inst/s rate will make only 10% of the
> +			 * aggregations to be closed due to the interrupt timer
> +			 * expiration for a streaming at wire-speed case.
> +			 *
> +			 * For a sparse streaming case this setting will yield
> +			 * at most 500us latency for a single RSC aggregation.
> +			 */
> +			eitr   |= (2000 | IXGBE_EITR_CNT_WDIS);
> +
> +			IXGBE_WRITE_REG(hw, IXGBE_RSCCTL(rxq->reg_idx), rscctl);
> +			IXGBE_WRITE_REG(hw, IXGBE_PSRTYPE(rxq->reg_idx),
> +								       psrtype);
> +			IXGBE_WRITE_REG(hw, IXGBE_EITR(rxq->reg_idx), eitr);
> +
> +			/*
> +			 * RSC requires the mapping of the queue to the
> +			 * interrupt vector.
> +			 */
> +			ixgbe_set_ivar(dev, rxq->reg_idx, i, 0);
> +
> +			rxq->rsc_en = 1;
> +		}
>   	}
>   
>   	if (rx_conf->enable_scatter)
>   		dev->data->scattered_rx = 1;
>   
> +	if (rx_conf->enable_lro)
> +		dev->data->lro = 1;
> +
>   	set_rx_function(dev);
>   
>   	/*
> @@ -3742,6 +4281,19 @@ ixgbe_dev_rx_init(struct rte_eth_dev *dev)
>   		IXGBE_WRITE_REG(hw, IXGBE_RDRXCTL, rdrxctl);
>   	}
>   
> +	/* Finalize RSC configuration  */
> +	if (rx_conf->enable_lro) {
> +		/*
> +		 * Follow the instructions in the 4.6.7.2.1 of the Spec Rev. 3.0
> +		 */
> +		rdrxctl = IXGBE_READ_REG(hw, IXGBE_RDRXCTL);
> +		rdrxctl |= IXGBE_RDRXCTL_RSCACKC;
> +		IXGBE_WRITE_REG(hw, IXGBE_RDRXCTL, rdrxctl);
> +
> +		PMD_INIT_LOG(INFO, "enabling LRO mode");
> +	}
> +
> +
>   	return 0;
>   }

I've just noticed that RTE_HEADER_SPLIT_ENABLE used in 
ixgbe_dev_rx_init() is not enabled anywhere: neither in config_XXX files 
nor anywhere else.
It looks like this macro is used only in ixgbe_rxtx.c. Seems like this 
is some sort of a legacy leftovers, isn't it?

Konstantin, could u, pls., comment?

>   
> diff --git a/lib/librte_pmd_ixgbe/ixgbe_rxtx.h b/lib/librte_pmd_ixgbe/ixgbe_rxtx.h
> index bbe5ff3..389173f 100644
> --- a/lib/librte_pmd_ixgbe/ixgbe_rxtx.h
> +++ b/lib/librte_pmd_ixgbe/ixgbe_rxtx.h
> @@ -79,6 +79,10 @@ struct igb_rx_entry {
>   	struct rte_mbuf *mbuf; /**< mbuf associated with RX descriptor. */
>   };
>   
> +struct igb_rsc_entry {
> +	struct rte_mbuf *fbuf; /**< First segment of the fragmented packet. */
> +};
> +
>   /**
>    * Structure associated with each descriptor of the TX ring of a TX queue.
>    */
> @@ -105,6 +109,7 @@ struct igb_rx_queue {
>   	volatile uint32_t   *rdt_reg_addr; /**< RDT register address. */
>   	volatile uint32_t   *rdh_reg_addr; /**< RDH register address. */
>   	struct igb_rx_entry *sw_ring; /**< address of RX software ring. */
> +	struct igb_rsc_entry *sw_rsc_ring; /**< address of RSC software ring. */
>   	struct rte_mbuf *pkt_first_seg; /**< First segment of current packet. */
>   	struct rte_mbuf *pkt_last_seg; /**< Last segment of current packet. */
>   	uint64_t            mbuf_initializer; /**< value to init mbufs */
> @@ -126,6 +131,7 @@ struct igb_rx_queue {
>   	uint8_t             port_id;  /**< Device port identifier. */
>   	uint8_t             crc_len;  /**< 0 if CRC stripped, 4 otherwise. */
>   	uint8_t             drop_en;  /**< If not 0, set SRRCTL.Drop_En. */
> +	uint8_t             rsc_en;   /**< If not 0, RSC is enabled. */
>   	uint8_t             rx_deferred_start; /**< not in global dev start. */
>   #ifdef RTE_LIBRTE_IXGBE_RX_ALLOW_BULK_ALLOC
>   	/** need to alloc dummy mbuf, for wraparound when scanning hw ring */