RE: [RFC v3 06/10] net/gve: support basic Rx data path for DQO

["Guo, Junfeng" <junfeng.guo@intel.com>]

> -----Original Message-----
> From: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
> Sent: Friday, February 17, 2023 23:18
> To: Guo, Junfeng <junfeng.guo@intel.com>; Zhang, Qi Z
> <qi.z.zhang@intel.com>; Wu, Jingjing <jingjing.wu@intel.com>;
> ferruh.yigit@amd.com; Xing, Beilei <beilei.xing@intel.com>
> Cc: dev@dpdk.org; Li, Xiaoyun <xiaoyun.li@intel.com>; Zhang, Helin
> <helin.zhang@intel.com>; Rushil Gupta <rushilg@google.com>; Jordan
> Kimbrough <jrkim@google.com>; Jeroen de Borst
> <jeroendb@google.com>; nd <nd@arm.com>; Honnappa Nagarahalli
> <Honnappa.Nagarahalli@arm.com>; nd <nd@arm.com>
> Subject: RE: [RFC v3 06/10] net/gve: support basic Rx data path for DQO
> 
> 
> 
> > -----Original Message-----
> > From: Junfeng Guo <junfeng.guo@intel.com>
> > Sent: Friday, February 17, 2023 1:32 AM
> > To: qi.z.zhang@intel.com; jingjing.wu@intel.com;
> ferruh.yigit@amd.com;
> > beilei.xing@intel.com
> > Cc: dev@dpdk.org; xiaoyun.li@intel.com; helin.zhang@intel.com;
> Junfeng
> > Guo <junfeng.guo@intel.com>; Rushil Gupta <rushilg@google.com>;
> Jordan
> > Kimbrough <jrkim@google.com>; Jeroen de Borst
> <jeroendb@google.com>
> > Subject: [RFC v3 06/10] net/gve: support basic Rx data path for DQO
> >
> > Add basic Rx data path support for DQO.
> >
> > Signed-off-by: Junfeng Guo <junfeng.guo@intel.com>
> > Signed-off-by: Rushil Gupta <rushilg@google.com>
> > Signed-off-by: Jordan Kimbrough <jrkim@google.com>
> > Signed-off-by: Jeroen de Borst <jeroendb@google.com>
> > ---
> >  drivers/net/gve/gve_ethdev.c |   1 +
> >  drivers/net/gve/gve_ethdev.h |   3 +
> >  drivers/net/gve/gve_rx_dqo.c | 128
> > +++++++++++++++++++++++++++++++++++
> >  3 files changed, 132 insertions(+)
> >
> > diff --git a/drivers/net/gve/gve_ethdev.c
> b/drivers/net/gve/gve_ethdev.c
> > index 1197194e41..1c9d272c2b 100644
> > --- a/drivers/net/gve/gve_ethdev.c
> > +++ b/drivers/net/gve/gve_ethdev.c
> > @@ -766,6 +766,7 @@ gve_dev_init(struct rte_eth_dev *eth_dev)
> >  		eth_dev->tx_pkt_burst = gve_tx_burst;
> >  	} else {
> >  		eth_dev->dev_ops = &gve_eth_dev_ops_dqo;
> > +		eth_dev->rx_pkt_burst = gve_rx_burst_dqo;
> >  		eth_dev->tx_pkt_burst = gve_tx_burst_dqo;
> >  	}
> >
> > diff --git a/drivers/net/gve/gve_ethdev.h
> b/drivers/net/gve/gve_ethdev.h
> > index f39a0884f2..a8e0dd5f3d 100644
> > --- a/drivers/net/gve/gve_ethdev.h
> > +++ b/drivers/net/gve/gve_ethdev.h
> > @@ -377,6 +377,9 @@ gve_stop_tx_queues_dqo(struct rte_eth_dev
> *dev);
> > void  gve_stop_rx_queues_dqo(struct rte_eth_dev *dev);
> >
> > +uint16_t
> > +gve_rx_burst_dqo(void *rxq, struct rte_mbuf **rx_pkts, uint16_t
> > +nb_pkts);
> > +
> >  uint16_t
> >  gve_tx_burst_dqo(void *txq, struct rte_mbuf **tx_pkts, uint16_t
> nb_pkts);
> >
> > diff --git a/drivers/net/gve/gve_rx_dqo.c
> b/drivers/net/gve/gve_rx_dqo.c
> > index 8236cd7b50..a281b237a4 100644
> > --- a/drivers/net/gve/gve_rx_dqo.c
> > +++ b/drivers/net/gve/gve_rx_dqo.c
> > @@ -5,6 +5,134 @@
> >  #include "gve_ethdev.h"
> >  #include "base/gve_adminq.h"
> >
> > +static inline void
> > +gve_rx_refill_dqo(struct gve_rx_queue *rxq) {
> > +	volatile struct gve_rx_desc_dqo *rx_buf_ring;
> > +	volatile struct gve_rx_desc_dqo *rx_buf_desc;
> > +	struct rte_mbuf *nmb[rxq->free_thresh];
> > +	uint16_t nb_refill = rxq->free_thresh;
> > +	uint16_t nb_desc = rxq->nb_rx_desc;
> > +	uint16_t next_avail = rxq->bufq_tail;
> > +	struct rte_eth_dev *dev;
> > +	uint64_t dma_addr;
> > +	uint16_t delta;
> > +	int i;
> > +
> > +	if (rxq->nb_rx_hold < rxq->free_thresh)
> > +		return;
> > +
> > +	rx_buf_ring = rxq->rx_ring;
> > +	delta = nb_desc - next_avail;
> > +	if (unlikely(delta < nb_refill)) {
> > +		if (likely(rte_pktmbuf_alloc_bulk(rxq->mpool, nmb, delta)
> ==
> > 0)) {
> > +			for (i = 0; i < delta; i++) {
> > +				rx_buf_desc = &rx_buf_ring[next_avail +
> i];
> > +				rxq->sw_ring[next_avail + i] = nmb[i];
> > +				dma_addr =
> > rte_cpu_to_le_64(rte_mbuf_data_iova_default(nmb[i]));
> > +				rx_buf_desc->header_buf_addr = 0;
> > +				rx_buf_desc->buf_addr = dma_addr;
> > +			}
> > +			nb_refill -= delta;
> > +			next_avail = 0;
> > +			rxq->nb_rx_hold -= delta;
> > +		} else {
> > +			dev = &rte_eth_devices[rxq->port_id];
> > +			dev->data->rx_mbuf_alloc_failed += nb_desc -
> > next_avail;
> > +			PMD_DRV_LOG(DEBUG, "RX mbuf alloc failed
> > port_id=%u queue_id=%u",
> > +				    rxq->port_id, rxq->queue_id);
> > +			return;
> > +		}
> > +	}
> > +
> > +	if (nb_desc - next_avail >= nb_refill) {
> > +		if (likely(rte_pktmbuf_alloc_bulk(rxq->mpool, nmb,
> nb_refill)
> > == 0)) {
> > +			for (i = 0; i < nb_refill; i++) {
> > +				rx_buf_desc = &rx_buf_ring[next_avail +
> i];
> > +				rxq->sw_ring[next_avail + i] = nmb[i];
> > +				dma_addr =
> > rte_cpu_to_le_64(rte_mbuf_data_iova_default(nmb[i]));
> > +				rx_buf_desc->header_buf_addr = 0;
> > +				rx_buf_desc->buf_addr = dma_addr;
> > +			}
> > +			next_avail += nb_refill;
> > +			rxq->nb_rx_hold -= nb_refill;
> > +		} else {
> > +			dev = &rte_eth_devices[rxq->port_id];
> > +			dev->data->rx_mbuf_alloc_failed += nb_desc -
> > next_avail;
> > +			PMD_DRV_LOG(DEBUG, "RX mbuf alloc failed
> > port_id=%u queue_id=%u",
> > +				    rxq->port_id, rxq->queue_id);
> > +		}
> > +	}
> > +
> > +	rte_write32(next_avail, rxq->qrx_tail);
> > +
> > +	rxq->bufq_tail = next_avail;
> > +}
> > +
> > +uint16_t
> > +gve_rx_burst_dqo(void *rx_queue, struct rte_mbuf **rx_pkts, uint16_t
> > +nb_pkts) {
> > +	volatile struct gve_rx_compl_desc_dqo *rx_compl_ring;
> > +	volatile struct gve_rx_compl_desc_dqo *rx_desc;
> > +	struct gve_rx_queue *rxq;
> > +	struct rte_mbuf *rxm;
> > +	uint16_t rx_id_bufq;
> > +	uint16_t pkt_len;
> > +	uint16_t rx_id;
> > +	uint16_t nb_rx;
> > +
> > +	nb_rx = 0;
> > +	rxq = rx_queue;
> > +	rx_id = rxq->rx_tail;
> > +	rx_id_bufq = rxq->next_avail;
> > +	rx_compl_ring = rxq->compl_ring;
> > +
> > +	while (nb_rx < nb_pkts) {
> > +		rx_desc = &rx_compl_ring[rx_id];
> > +
> > +		/* check status */
> > +		if (rx_desc->generation != rxq->cur_gen_bit)
> > +			break;
> From my experience with other PMDs, I think an IO read barrier is needed
> here to ensure other parts of descriptors are not loaded before loading
> rx_desc->generation.

Yes, the memory barrier should be added here to prevent the code lines 
being reordered by the compiler for some optimizations.
We will refine this in the coming versions. Thanks a lot!

> 
> > +
> > +		if (unlikely(rx_desc->rx_error))
> > +			continue;
> > +
> > +		pkt_len = rx_desc->packet_len;
> > +
> > +		rx_id++;
> > +		if (rx_id == rxq->nb_rx_desc) {
> > +			rx_id = 0;
> > +			rxq->cur_gen_bit ^= 1;
> > +		}
> > +
> > +		rxm = rxq->sw_ring[rx_id_bufq];
> > +		rx_id_bufq++;
> > +		if (rx_id_bufq == rxq->nb_rx_desc)
> > +			rx_id_bufq = 0;
> > +		rxq->nb_rx_hold++;
> > +
> > +		rxm->pkt_len = pkt_len;
> > +		rxm->data_len = pkt_len;
> > +		rxm->port = rxq->port_id;
> > +		rxm->ol_flags = 0;
> > +
> > +		rxm->ol_flags |= RTE_MBUF_F_RX_RSS_HASH;
> > +		rxm->hash.rss = rte_be_to_cpu_32(rx_desc->hash);
> > +
> > +		rx_pkts[nb_rx++] = rxm;
> > +	}
> > +
> > +	if (nb_rx > 0) {
> > +		rxq->rx_tail = rx_id;
> > +		if (rx_id_bufq != rxq->next_avail)
> > +			rxq->next_avail = rx_id_bufq;
> > +
> > +		gve_rx_refill_dqo(rxq);
> > +	}
> > +
> > +	return nb_rx;
> > +}
> > +
> >  static inline void
> >  gve_release_rxq_mbufs_dqo(struct gve_rx_queue *rxq)  {
> > --
> > 2.34.1