Subject: Re: [PATCH net-next 3/4] gve: Add XDP REDIRECT support for GQI-QPL format

From: Maciej Fijalkowski <[email-masked]>
Date: Tue, 14 Feb 2023 02:03:34 +0100

On Tue, Feb 07, 2023 at 01:00:57PM -0800, Praveen Kaligineedi wrote:
> Add support for XDP REDIRECT action.
> 
> This patch contains the following changes:
> 1) Support for XDP REDIRECT action on rx
> 2) ndo_xdp_xmit callback support
> 
> Signed-off-by: Praveen Kaligineedi <[email-masked]>
> Reviewed-by: Jeroen de Borst <[email-masked]>
> ---
>  drivers/net/ethernet/google/gve/gve.h         | 13 ++++-
>  drivers/net/ethernet/google/gve/gve_ethtool.c | 26 ++++++----
>  drivers/net/ethernet/google/gve/gve_main.c    | 17 +++++++
>  drivers/net/ethernet/google/gve/gve_rx.c      | 45 +++++++++++++++--
>  drivers/net/ethernet/google/gve/gve_tx.c      | 48 +++++++++++++++++--
>  5 files changed, 132 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/net/ethernet/google/gve/gve.h b/drivers/net/ethernet/google/gve/gve.h
> index 8352f4c0e8d1..f89b1278db70 100644
> --- a/drivers/net/ethernet/google/gve/gve.h
> +++ b/drivers/net/ethernet/google/gve/gve.h
> @@ -236,6 +236,7 @@ struct gve_rx_ring {
>  	u64 rx_frag_alloc_cnt; /* free-running count of rx page allocations */
>  	u64 xdp_tx_errors;
>  	u64 xdp_redirect_errors;
> +	u64 xdp_alloc_fails;
>  	u64 xdp_actions[GVE_XDP_ACTIONS];
>  	u32 q_num; /* queue index */
>  	u32 ntfy_id; /* notification block index */
> @@ -247,6 +248,7 @@ struct gve_rx_ring {
>  
>  	/* XDP stuff */
>  	struct xdp_rxq_info xdp_rxq;
> +	struct page_frag_cache page_cache;

few words about why you need that would be helpful

>  };
>  
>  /* A TX desc ring entry */
> @@ -267,7 +269,10 @@ struct gve_tx_iovec {
>   * ring entry but only used for a pkt_desc not a seg_desc
>   */
>  struct gve_tx_buffer_state {
> -	struct sk_buff *skb; /* skb for this pkt */
> +	union {
> +		struct sk_buff *skb; /* skb for this pkt */
> +		struct xdp_frame *xdp_frame; /* xdp_frame */
> +	};
>  	struct {
>  		u16 size; /* size of xmitted xdp pkt */
>  	} xdp;
> @@ -464,6 +469,8 @@ struct gve_tx_ring {
>  	dma_addr_t q_resources_bus; /* dma address of the queue resources */
>  	dma_addr_t complq_bus_dqo; /* dma address of the dqo.compl_ring */
>  	struct u64_stats_sync statss; /* sync stats for 32bit archs */
> +	u64 xdp_xmit;
> +	u64 xdp_xmit_errors;
>  } ____cacheline_aligned;
>  
>  /* Wraps the info for one irq including the napi struct and the queues
> @@ -889,8 +896,10 @@ void gve_free_page(struct device *dev, struct page *page, dma_addr_t dma,
>  		   enum dma_data_direction);
>  /* tx handling */
>  netdev_tx_t gve_tx(struct sk_buff *skb, struct net_device *dev);
> +int gve_xdp_xmit(struct net_device *dev, int n, struct xdp_frame **frames,
> +		 u32 flags);
>  int gve_xdp_xmit_one(struct gve_priv *priv, struct gve_tx_ring *tx,
> -		     void *data, int len, u32 flags);
> +		     void *data, int len, void *frame_p, u32 flags);
>  bool gve_tx_poll(struct gve_notify_block *block, int budget);
>  bool gve_xdp_poll(struct gve_notify_block *block, int budget);
>  int gve_tx_alloc_rings(struct gve_priv *priv);
> diff --git a/drivers/net/ethernet/google/gve/gve_ethtool.c b/drivers/net/ethernet/google/gve/gve_ethtool.c
> index d2f0b53eacbb..57940f90c6be 100644
> --- a/drivers/net/ethernet/google/gve/gve_ethtool.c
> +++ b/drivers/net/ethernet/google/gve/gve_ethtool.c
> @@ -56,13 +56,14 @@ static const char gve_gstrings_rx_stats[][ETH_GSTRING_LEN] = {
>  	"rx_drops_packet_over_mru[%u]", "rx_drops_invalid_checksum[%u]",
>  	"rx_xdp_aborted[%u]", "rx_xdp_drop[%u]", "rx_xdp_pass[%u]",
>  	"rx_xdp_tx[%u]", "rx_xdp_redirect[%u]",
> -	"rx_xdp_tx_errors[%u]", "rx_xdp_redirect_errors[%u]",
> +	"rx_xdp_tx_errors[%u]", "rx_xdp_redirect_errors[%u]", "rx_xdp_alloc_fails[%u]",
>  };
>  
>  static const char gve_gstrings_tx_stats[][ETH_GSTRING_LEN] = {
>  	"tx_posted_desc[%u]", "tx_completed_desc[%u]", "tx_consumed_desc[%u]", "tx_bytes[%u]",
>  	"tx_wake[%u]", "tx_stop[%u]", "tx_event_counter[%u]",
>  	"tx_dma_mapping_error[%u]",
> +	"tx_xdp_xmit[%u]", "tx_xdp_xmit_errors[%u]"
>  };
>  
>  static const char gve_gstrings_adminq_stats[][ETH_GSTRING_LEN] = {
> @@ -312,9 +313,10 @@ gve_get_ethtool_stats(struct net_device *netdev,
>  					data[i + j] = rx->xdp_actions[j];
>  				data[i + j++] = rx->xdp_tx_errors;
>  				data[i + j++] = rx->xdp_redirect_errors;
> +				data[i + j++] = rx->xdp_alloc_fails;
>  			} while (u64_stats_fetch_retry(&priv->rx[ring].statss,
>  						       start));
> -			i += GVE_XDP_ACTIONS + 2; /* XDP rx counters */
> +			i += GVE_XDP_ACTIONS + 3; /* XDP rx counters */
>  		}
>  	} else {
>  		i += priv->rx_cfg.num_queues * NUM_GVE_RX_CNTS;
> @@ -370,13 +372,21 @@ gve_get_ethtool_stats(struct net_device *netdev,
>  			if (skip_nic_stats) {
>  				/* skip NIC tx stats */
>  				i += NIC_TX_STATS_REPORT_NUM;
> -				continue;
> -			}
> -			for (j = 0; j < NIC_TX_STATS_REPORT_NUM; j++) {
> -				u64 value =
> -				be64_to_cpu(report_stats[tx_qid_to_stats_idx[ring] + j].value);
> -				data[i++] = value;
> +			} else {
> +				stats_idx = tx_qid_to_stats_idx[ring];
> +				for (j = 0; j < NIC_TX_STATS_REPORT_NUM; j++) {
> +					u64 value =
> +						be64_to_cpu(report_stats[stats_idx + j].value);
> +					data[i++] = value;
> +				}
>  			}
> +			do {
> +				start = u64_stats_fetch_begin(&priv->tx[ring].statss);
> +				data[i] = tx->xdp_xmit;
> +				data[i + 1] = tx->xdp_xmit_errors;
> +			} while (u64_stats_fetch_retry(&priv->tx[ring].statss,
> +						       start));
> +			i += 2; /* XDP tx counters */
>  		}
>  	} else {
>  		i += num_tx_queues * NUM_GVE_TX_CNTS;
> diff --git a/drivers/net/ethernet/google/gve/gve_main.c b/drivers/net/ethernet/google/gve/gve_main.c
> index 5050aa3aa1c3..4398e5887f3b 100644
> --- a/drivers/net/ethernet/google/gve/gve_main.c
> +++ b/drivers/net/ethernet/google/gve/gve_main.c
> @@ -1015,6 +1015,21 @@ static void gve_unreg_xdp_info(struct gve_priv *priv)
>  	}
>  }
>  
> +static void gve_drain_page_cache(struct gve_priv *priv)
> +{
> +	struct page_frag_cache *nc;
> +	int i;
> +
> +	for (i = 0; i < priv->rx_cfg.num_queues; i++) {
> +		nc = &priv->rx[i].page_cache;
> +		if (nc->va) {
> +			__page_frag_cache_drain(virt_to_page(nc->va),
> +						nc->pagecnt_bias);
> +			nc->va = NULL;
> +		}
> +	}
> +}
> +
>  static int gve_open(struct net_device *dev)
>  {
>  	struct gve_priv *priv = netdev_priv(dev);
> @@ -1098,6 +1113,7 @@ static int gve_close(struct net_device *dev)
>  	netif_carrier_off(dev);
>  	if (gve_get_device_rings_ok(priv)) {
>  		gve_turndown(priv);
> +		gve_drain_page_cache(priv);
>  		err = gve_destroy_rings(priv);
>  		if (err)
>  			goto err;
> @@ -1409,6 +1425,7 @@ static const struct net_device_ops gve_netdev_ops = {
>  	.ndo_tx_timeout         =       gve_tx_timeout,
>  	.ndo_set_features	=	gve_set_features,
>  	.ndo_bpf		=	gve_xdp,
> +	.ndo_xdp_xmit		=	gve_xdp_xmit,
>  };
>  
>  static void gve_handle_status(struct gve_priv *priv, u32 status)
> diff --git a/drivers/net/ethernet/google/gve/gve_rx.c b/drivers/net/ethernet/google/gve/gve_rx.c
> index 3785bc150546..ea833388f895 100644
> --- a/drivers/net/ethernet/google/gve/gve_rx.c
> +++ b/drivers/net/ethernet/google/gve/gve_rx.c
> @@ -593,6 +593,35 @@ static struct sk_buff *gve_rx_skb(struct gve_priv *priv, struct gve_rx_ring *rx,
>  	return skb;
>  }
>  
> +static int gve_xdp_redirect(struct net_device *dev, struct gve_rx_ring *rx,
> +			    struct xdp_buff *orig, struct bpf_prog *xdp_prog)
> +{
> +	int total_len, len = orig->data_end - orig->data;
> +	int headroom = XDP_PACKET_HEADROOM;
> +	struct xdp_buff new;
> +	void *frame;
> +	int err;
> +
> +	total_len = headroom + SKB_DATA_ALIGN(len) +
> +		SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
> +	frame = page_frag_alloc(&rx->page_cache, total_len, GFP_ATOMIC);
> +	if (!frame) {
> +		u64_stats_update_begin(&rx->statss);
> +		rx->xdp_alloc_fails++;
> +		u64_stats_update_end(&rx->statss);
> +		return -ENOMEM;
> +	}
> +	xdp_init_buff(&new, total_len, &rx->xdp_rxq);
> +	xdp_prepare_buff(&new, frame, headroom, len, false);
> +	memcpy(new.data, orig->data, len);

can you explain why?

> +
> +	err = xdp_do_redirect(dev, &new, xdp_prog);
> +	if (err)
> +		page_frag_free(frame);
> +
> +	return err;
> +}
> +

(...)