gve: Add AF_XDP zero-copy support for GQI-QPL format

Adding AF_XDP zero-copy support.

Note: Although these changes support AF_XDP socket in zero-copy
mode, there is still a copy happening within the driver between
XSK buffer pool and QPL bounce buffers in GQI-QPL format.
In GQI-QPL queue format, the driver needs to allocate a fixed size
memory, the size specified by vNIC device, for RX/TX and register this
memory as a bounce buffer with the vNIC device when a queue is
created. The number of pages in the bounce buffer is limited and the
pages need to be made available to the vNIC by copying the RX data out
to prevent head-of-line blocking. Therefore, we cannot pass the XSK
buffer pool to the vNIC.

The number of copies on RX path from the bounce buffer to XSK buffer is 2
for AF_XDP copy mode (bounce buffer -> allocated page frag -> XSK buffer)
and 1 for AF_XDP zero-copy mode (bounce buffer -> XSK buffer).

This patch contains the following changes:
1) Enable and disable XSK buffer pool
2) Copy XDP packets from QPL bounce buffers to XSK buffer on rx
3) Copy XDP packets from XSK buffer to QPL bounce buffers and
   ring the doorbell as part of XDP TX napi poll
4) ndo_xsk_wakeup callback support

Signed-off-by: Praveen Kaligineedi <pkaligineedi@google.com>
Reviewed-by: Jeroen de Borst <jeroendb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/google/gve/gve.h

@@ -248,6 +248,8 @@ struct gve_rx_ring {
 
 	/* XDP stuff */
 	struct xdp_rxq_info xdp_rxq;
+	struct xdp_rxq_info xsk_rxq;
+	struct xsk_buff_pool *xsk_pool;
 	struct page_frag_cache page_cache; /* Page cache to allocate XDP frames */
 };
 
@@ -275,6 +277,7 @@ struct gve_tx_buffer_state {
 	};
 	struct {
 		u16 size; /* size of xmitted xdp pkt */
+		u8 is_xsk; /* xsk buff */
 	} xdp;
 	union {
 		struct gve_tx_iovec iov[GVE_TX_MAX_IOVEC]; /* segments of this pkt */
@@ -469,6 +472,10 @@ 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 */
+	struct xsk_buff_pool *xsk_pool;
+	u32 xdp_xsk_wakeup;
+	u32 xdp_xsk_done;
+	u64 xdp_xsk_sent;
 	u64 xdp_xmit;
 	u64 xdp_xmit_errors;
 } ____cacheline_aligned;

drivers/net/ethernet/google/gve/gve_ethtool.c

@@ -62,8 +62,8 @@ static const char gve_gstrings_rx_stats[][ETH_GSTRING_LEN] = {
 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]"
+	"tx_dma_mapping_error[%u]", "tx_xsk_wakeup[%u]",
+	"tx_xsk_done[%u]", "tx_xsk_sent[%u]", "tx_xdp_xmit[%u]", "tx_xdp_xmit_errors[%u]"
 };
 
 static const char gve_gstrings_adminq_stats[][ETH_GSTRING_LEN] = {
@@ -381,13 +381,17 @@ gve_get_ethtool_stats(struct net_device *netdev,
 					data[i++] = value;
 				}
 			}
+			/* XDP xsk counters */
+			data[i++] = tx->xdp_xsk_wakeup;
+			data[i++] = tx->xdp_xsk_done;
 			do {
 				start = u64_stats_fetch_begin(&priv->tx[ring].statss);
-				data[i] = tx->xdp_xmit;
-				data[i + 1] = tx->xdp_xmit_errors;
+				data[i] = tx->xdp_xsk_sent;
+				data[i + 1] = tx->xdp_xmit;
+				data[i + 2] = tx->xdp_xmit_errors;
 			} while (u64_stats_fetch_retry(&priv->tx[ring].statss,
 						       start));
-			i += 2; /* XDP tx counters */
+			i += 3; /* XDP tx counters */
 		}
 	} else {
 		i += num_tx_queues * NUM_GVE_TX_CNTS;

drivers/net/ethernet/google/gve/gve_main.c

@@ -17,6 +17,7 @@
 #include <linux/utsname.h>
 #include <linux/version.h>
 #include <net/sch_generic.h>
+#include <net/xdp_sock_drv.h>
 #include "gve.h"
 #include "gve_dqo.h"
 #include "gve_adminq.h"
@@ -1188,6 +1189,7 @@ static int gve_reg_xdp_info(struct gve_priv *priv, struct net_device *dev)
 	struct gve_rx_ring *rx;
 	int err = 0;
 	int i, j;
+	u32 tx_qid;
 
 	if (!priv->num_xdp_queues)
 		return 0;
@@ -1204,6 +1206,24 @@ static int gve_reg_xdp_info(struct gve_priv *priv, struct net_device *dev)
 						 MEM_TYPE_PAGE_SHARED, NULL);
 		if (err)
 			goto err;
+		rx->xsk_pool = xsk_get_pool_from_qid(dev, i);
+		if (rx->xsk_pool) {
+			err = xdp_rxq_info_reg(&rx->xsk_rxq, dev, i,
+					       napi->napi_id);
+			if (err)
+				goto err;
+			err = xdp_rxq_info_reg_mem_model(&rx->xsk_rxq,
+							 MEM_TYPE_XSK_BUFF_POOL, NULL);
+			if (err)
+				goto err;
+			xsk_pool_set_rxq_info(rx->xsk_pool,
+					      &rx->xsk_rxq);
+		}
+	}
+
+	for (i = 0; i < priv->num_xdp_queues; i++) {
+		tx_qid = gve_xdp_tx_queue_id(priv, i);
+		priv->tx[tx_qid].xsk_pool = xsk_get_pool_from_qid(dev, i);
 	}
 	return 0;
 
@@ -1212,13 +1232,15 @@ static int gve_reg_xdp_info(struct gve_priv *priv, struct net_device *dev)
 		rx = &priv->rx[j];
 		if (xdp_rxq_info_is_reg(&rx->xdp_rxq))
 			xdp_rxq_info_unreg(&rx->xdp_rxq);
+		if (xdp_rxq_info_is_reg(&rx->xsk_rxq))
+			xdp_rxq_info_unreg(&rx->xsk_rxq);
 	}
 	return err;
 }
 
 static void gve_unreg_xdp_info(struct gve_priv *priv)
 {
-	int i;
+	int i, tx_qid;
 
 	if (!priv->num_xdp_queues)
 		return;
@@ -1227,6 +1249,15 @@ static void gve_unreg_xdp_info(struct gve_priv *priv)
 		struct gve_rx_ring *rx = &priv->rx[i];
 
 		xdp_rxq_info_unreg(&rx->xdp_rxq);
+		if (rx->xsk_pool) {
+			xdp_rxq_info_unreg(&rx->xsk_rxq);
+			rx->xsk_pool = NULL;
+		}
+	}
+
+	for (i = 0; i < priv->num_xdp_queues; i++) {
+		tx_qid = gve_xdp_tx_queue_id(priv, i);
+		priv->tx[tx_qid].xsk_pool = NULL;
 	}
 }
 
@@ -1469,6 +1500,140 @@ static int gve_set_xdp(struct gve_priv *priv, struct bpf_prog *prog,
 	return err;
 }
 
+static int gve_xsk_pool_enable(struct net_device *dev,
+			       struct xsk_buff_pool *pool,
+			       u16 qid)
+{
+	struct gve_priv *priv = netdev_priv(dev);
+	struct napi_struct *napi;
+	struct gve_rx_ring *rx;
+	int tx_qid;
+	int err;
+
+	if (qid >= priv->rx_cfg.num_queues) {
+		dev_err(&priv->pdev->dev, "xsk pool invalid qid %d", qid);
+		return -EINVAL;
+	}
+	if (xsk_pool_get_rx_frame_size(pool) <
+	     priv->dev->max_mtu + sizeof(struct ethhdr)) {
+		dev_err(&priv->pdev->dev, "xsk pool frame_len too small");
+		return -EINVAL;
+	}
+
+	err = xsk_pool_dma_map(pool, &priv->pdev->dev,
+			       DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_WEAK_ORDERING);
+	if (err)
+		return err;
+
+	/* If XDP prog is not installed, return */
+	if (!priv->xdp_prog)
+		return 0;
+
+	rx = &priv->rx[qid];
+	napi = &priv->ntfy_blocks[rx->ntfy_id].napi;
+	err = xdp_rxq_info_reg(&rx->xsk_rxq, dev, qid, napi->napi_id);
+	if (err)
+		goto err;
+
+	err = xdp_rxq_info_reg_mem_model(&rx->xsk_rxq,
+					 MEM_TYPE_XSK_BUFF_POOL, NULL);
+	if (err)
+		goto err;
+
+	xsk_pool_set_rxq_info(pool, &rx->xsk_rxq);
+	rx->xsk_pool = pool;
+
+	tx_qid = gve_xdp_tx_queue_id(priv, qid);
+	priv->tx[tx_qid].xsk_pool = pool;
+
+	return 0;
+err:
+	if (xdp_rxq_info_is_reg(&rx->xsk_rxq))
+		xdp_rxq_info_unreg(&rx->xsk_rxq);
+
+	xsk_pool_dma_unmap(pool,
+			   DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_WEAK_ORDERING);
+	return err;
+}
+
+static int gve_xsk_pool_disable(struct net_device *dev,
+				u16 qid)
+{
+	struct gve_priv *priv = netdev_priv(dev);
+	struct napi_struct *napi_rx;
+	struct napi_struct *napi_tx;
+	struct xsk_buff_pool *pool;
+	int tx_qid;
+
+	pool = xsk_get_pool_from_qid(dev, qid);
+	if (!pool)
+		return -EINVAL;
+	if (qid >= priv->rx_cfg.num_queues)
+		return -EINVAL;
+
+	/* If XDP prog is not installed, unmap DMA and return */
+	if (!priv->xdp_prog)
+		goto done;
+
+	tx_qid = gve_xdp_tx_queue_id(priv, qid);
+	if (!netif_running(dev)) {
+		priv->rx[qid].xsk_pool = NULL;
+		xdp_rxq_info_unreg(&priv->rx[qid].xsk_rxq);
+		priv->tx[tx_qid].xsk_pool = NULL;
+		goto done;
+	}
+
+	napi_rx = &priv->ntfy_blocks[priv->rx[qid].ntfy_id].napi;
+	napi_disable(napi_rx); /* make sure current rx poll is done */
+
+	napi_tx = &priv->ntfy_blocks[priv->tx[tx_qid].ntfy_id].napi;
+	napi_disable(napi_tx); /* make sure current tx poll is done */
+
+	priv->rx[qid].xsk_pool = NULL;
+	xdp_rxq_info_unreg(&priv->rx[qid].xsk_rxq);
+	priv->tx[tx_qid].xsk_pool = NULL;
+	smp_mb(); /* Make sure it is visible to the workers on datapath */
+
+	napi_enable(napi_rx);
+	if (gve_rx_work_pending(&priv->rx[qid]))
+		napi_schedule(napi_rx);
+
+	napi_enable(napi_tx);
+	if (gve_tx_clean_pending(priv, &priv->tx[tx_qid]))
+		napi_schedule(napi_tx);
+
+done:
+	xsk_pool_dma_unmap(pool,
+			   DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_WEAK_ORDERING);
+	return 0;
+}
+
+static int gve_xsk_wakeup(struct net_device *dev, u32 queue_id, u32 flags)
+{
+	struct gve_priv *priv = netdev_priv(dev);
+	int tx_queue_id = gve_xdp_tx_queue_id(priv, queue_id);
+
+	if (queue_id >= priv->rx_cfg.num_queues || !priv->xdp_prog)
+		return -EINVAL;
+
+	if (flags & XDP_WAKEUP_TX) {
+		struct gve_tx_ring *tx = &priv->tx[tx_queue_id];
+		struct napi_struct *napi =
+			&priv->ntfy_blocks[tx->ntfy_id].napi;
+
+		if (!napi_if_scheduled_mark_missed(napi)) {
+			/* Call local_bh_enable to trigger SoftIRQ processing */
+			local_bh_disable();
+			napi_schedule(napi);
+			local_bh_enable();
+		}
+
+		tx->xdp_xsk_wakeup++;
+	}
+
+	return 0;
+}
+
 static int verify_xdp_configuration(struct net_device *dev)
 {
 	struct gve_priv *priv = netdev_priv(dev);
@@ -1512,6 +1677,11 @@ static int gve_xdp(struct net_device *dev, struct netdev_bpf *xdp)
 	switch (xdp->command) {
 	case XDP_SETUP_PROG:
 		return gve_set_xdp(priv, xdp->prog, xdp->extack);
+	case XDP_SETUP_XSK_POOL:
+		if (xdp->xsk.pool)
+			return gve_xsk_pool_enable(dev, xdp->xsk.pool, xdp->xsk.queue_id);
+		else
+			return gve_xsk_pool_disable(dev, xdp->xsk.queue_id);
 	default:
 		return -EINVAL;
 	}
@@ -1713,6 +1883,7 @@ static const struct net_device_ops gve_netdev_ops = {
 	.ndo_set_features	=	gve_set_features,
 	.ndo_bpf		=	gve_xdp,
 	.ndo_xdp_xmit		=	gve_xdp_xmit,
+	.ndo_xsk_wakeup		=	gve_xsk_wakeup,
 };
 
 static void gve_handle_status(struct gve_priv *priv, u32 status)
@@ -1838,6 +2009,7 @@ static void gve_set_netdev_xdp_features(struct gve_priv *priv)
 		priv->dev->xdp_features = NETDEV_XDP_ACT_BASIC;
 		priv->dev->xdp_features |= NETDEV_XDP_ACT_REDIRECT;
 		priv->dev->xdp_features |= NETDEV_XDP_ACT_NDO_XMIT;
+		priv->dev->xdp_features |= NETDEV_XDP_ACT_XSK_ZEROCOPY;
 	} else {
 		priv->dev->xdp_features = 0;
 	}

drivers/net/ethernet/google/gve/gve_rx.c

@@ -10,6 +10,7 @@
 #include <linux/etherdevice.h>
 #include <linux/filter.h>
 #include <net/xdp.h>
+#include <net/xdp_sock_drv.h>
 
 static void gve_rx_free_buffer(struct device *dev,
 			       struct gve_rx_slot_page_info *page_info,
@@ -593,6 +594,31 @@ static struct sk_buff *gve_rx_skb(struct gve_priv *priv, struct gve_rx_ring *rx,
 	return skb;
 }
 
+static int gve_xsk_pool_redirect(struct net_device *dev,
+				 struct gve_rx_ring *rx,
+				 void *data, int len,
+				 struct bpf_prog *xdp_prog)
+{
+	struct xdp_buff *xdp;
+	int err;
+
+	if (rx->xsk_pool->frame_len < len)
+		return -E2BIG;
+	xdp = xsk_buff_alloc(rx->xsk_pool);
+	if (!xdp) {
+		u64_stats_update_begin(&rx->statss);
+		rx->xdp_alloc_fails++;
+		u64_stats_update_end(&rx->statss);
+		return -ENOMEM;
+	}
+	xdp->data_end = xdp->data + len;
+	memcpy(xdp->data, data, len);
+	err = xdp_do_redirect(dev, xdp, xdp_prog);
+	if (err)
+		xsk_buff_free(xdp);
+	return err;
+}
+
 static int gve_xdp_redirect(struct net_device *dev, struct gve_rx_ring *rx,
 			    struct xdp_buff *orig, struct bpf_prog *xdp_prog)
 {
@@ -602,6 +628,10 @@ static int gve_xdp_redirect(struct net_device *dev, struct gve_rx_ring *rx,
 	void *frame;
 	int err;
 
+	if (rx->xsk_pool)
+		return gve_xsk_pool_redirect(dev, rx, orig->data,
+					     len, xdp_prog);
+
 	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);