Date:   Thu, 31 Oct 2019 10:23:23 +0000
From:   Charles McLachlan <cmclachlan@...arflare.com>
To:     <davem@...emloft.net>
CC:     <netdev@...r.kernel.org>, <linux-net-drivers@...arflare.com>,
        <brouer@...hat.com>
Subject: [PATCH net-next v4 2/6] sfc: perform XDP processing on received
 packets

Adds a field to hold an attached xdp_prog, but never populates it (see
following patch).  Also, XDP_TX support is deferred to a later patch
in the series.

Track failures of xdp_rxq_info_reg() via per-queue xdp_rxq_info_valid
flags and a per-nic xdp_rxq_info_failed flag. The per-queue flags are
needed to prevent attempts to xdp_rxq_info_unreg() structs that failed
to register.  Possibly the API could be changed in the future to avoid
the need for these flags.

Signed-off-by: Charles McLachlan <cmclachlan@...arflare.com>
---
 drivers/net/ethernet/sfc/efx.c        |   5 +-
 drivers/net/ethernet/sfc/net_driver.h |  12 +++
 drivers/net/ethernet/sfc/rx.c         | 130 +++++++++++++++++++++++++-
 3 files changed, 145 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/sfc/efx.c b/drivers/net/ethernet/sfc/efx.c
index 2fef7402233e..bd0424414781 100644
--- a/drivers/net/ethernet/sfc/efx.c
+++ b/drivers/net/ethernet/sfc/efx.c
@@ -340,6 +340,8 @@ static int efx_poll(struct napi_struct *napi, int budget)
 
 	spent = efx_process_channel(channel, budget);
 
+	xdp_do_flush_map();
+
 	if (spent < budget) {
 		if (efx_channel_has_rx_queue(channel) &&
 		    efx->irq_rx_adaptive &&
@@ -651,7 +653,7 @@ static void efx_start_datapath(struct efx_nic *efx)
 	efx->rx_dma_len = (efx->rx_prefix_size +
 			   EFX_MAX_FRAME_LEN(efx->net_dev->mtu) +
 			   efx->type->rx_buffer_padding);
-	rx_buf_len = (sizeof(struct efx_rx_page_state) +
+	rx_buf_len = (sizeof(struct efx_rx_page_state) + XDP_PACKET_HEADROOM +
 		      efx->rx_ip_align + efx->rx_dma_len);
 	if (rx_buf_len <= PAGE_SIZE) {
 		efx->rx_scatter = efx->type->always_rx_scatter;
@@ -774,6 +776,7 @@ static void efx_stop_datapath(struct efx_nic *efx)
 		efx_for_each_possible_channel_tx_queue(tx_queue, channel)
 			efx_fini_tx_queue(tx_queue);
 	}
+	efx->xdp_rxq_info_failed = false;
 }
 
 static void efx_remove_channel(struct efx_channel *channel)
diff --git a/drivers/net/ethernet/sfc/net_driver.h b/drivers/net/ethernet/sfc/net_driver.h
index 7394d901e021..a5a5055969fb 100644
--- a/drivers/net/ethernet/sfc/net_driver.h
+++ b/drivers/net/ethernet/sfc/net_driver.h
@@ -369,6 +369,8 @@ struct efx_rx_page_state {
  *	refill was triggered.
  * @recycle_count: RX buffer recycle counter.
  * @slow_fill: Timer used to defer efx_nic_generate_fill_event().
+ * @xdp_rxq_info: XDP specific RX queue information.
+ * @xdp_rxq_info_valid: Is xdp_rxq_info valid data?.
  */
 struct efx_rx_queue {
 	struct efx_nic *efx;
@@ -400,6 +402,8 @@ struct efx_rx_queue {
 	unsigned int slow_fill_count;
 	/* Statistics to supplement MAC stats */
 	unsigned long rx_packets;
+	struct xdp_rxq_info xdp_rxq_info;
+	bool xdp_rxq_info_valid;
 };
 
 enum efx_sync_events_state {
@@ -900,6 +904,7 @@ struct efx_async_filter_insertion {
  * @loopback_mode: Loopback status
  * @loopback_modes: Supported loopback mode bitmask
  * @loopback_selftest: Offline self-test private state
+ * @xdp_prog: Current XDP programme for this interface
  * @filter_sem: Filter table rw_semaphore, protects existence of @filter_state
  * @filter_state: Architecture-dependent filter table state
  * @rps_mutex: Protects RPS state of all channels
@@ -925,6 +930,8 @@ struct efx_async_filter_insertion {
  * @ptp_data: PTP state data
  * @ptp_warned: has this NIC seen and warned about unexpected PTP events?
  * @vpd_sn: Serial number read from VPD
+ * @xdp_rxq_info_failed: Have any of the rx queues failed to initialise their
+ *      xdp_rxq_info structures?
  * @monitor_work: Hardware monitor workitem
  * @biu_lock: BIU (bus interface unit) lock
  * @last_irq_cpu: Last CPU to handle a possible test interrupt.  This
@@ -1059,6 +1066,10 @@ struct efx_nic {
 	u64 loopback_modes;
 
 	void *loopback_selftest;
+	/* We access loopback_selftest immediately before running XDP,
+	 * so we want them next to each other.
+	 */
+	struct bpf_prog __rcu *xdp_prog;
 
 	struct rw_semaphore filter_sem;
 	void *filter_state;
@@ -1088,6 +1099,7 @@ struct efx_nic {
 	bool ptp_warned;
 
 	char *vpd_sn;
+	bool xdp_rxq_info_failed;
 
 	/* The following fields may be written more often */
 
diff --git a/drivers/net/ethernet/sfc/rx.c b/drivers/net/ethernet/sfc/rx.c
index 85ec07f5a674..644d157843c6 100644
--- a/drivers/net/ethernet/sfc/rx.c
+++ b/drivers/net/ethernet/sfc/rx.c
@@ -17,6 +17,8 @@
 #include <linux/iommu.h>
 #include <net/ip.h>
 #include <net/checksum.h>
+#include <net/xdp.h>
+#include <linux/bpf_trace.h>
 #include "net_driver.h"
 #include "efx.h"
 #include "filter.h"
@@ -27,6 +29,9 @@
 /* Preferred number of descriptors to fill at once */
 #define EFX_RX_PREFERRED_BATCH 8U
 
+/* Maximum rx prefix used by any architecture. */
+#define EFX_MAX_RX_PREFIX_SIZE 16
+
 /* Number of RX buffers to recycle pages for.  When creating the RX page recycle
  * ring, this number is divided by the number of buffers per page to calculate
  * the number of pages to store in the RX page recycle ring.
@@ -95,7 +100,7 @@ void efx_rx_config_page_split(struct efx_nic *efx)
 				      EFX_RX_BUF_ALIGNMENT);
 	efx->rx_bufs_per_page = efx->rx_buffer_order ? 1 :
 		((PAGE_SIZE - sizeof(struct efx_rx_page_state)) /
-		 efx->rx_page_buf_step);
+		(efx->rx_page_buf_step + XDP_PACKET_HEADROOM));
 	efx->rx_buffer_truesize = (PAGE_SIZE << efx->rx_buffer_order) /
 		efx->rx_bufs_per_page;
 	efx->rx_pages_per_batch = DIV_ROUND_UP(EFX_RX_PREFERRED_BATCH,
@@ -185,6 +190,9 @@ static int efx_init_rx_buffers(struct efx_rx_queue *rx_queue, bool atomic)
 		page_offset = sizeof(struct efx_rx_page_state);
 
 		do {
+			page_offset += XDP_PACKET_HEADROOM;
+			dma_addr += XDP_PACKET_HEADROOM;
+
 			index = rx_queue->added_count & rx_queue->ptr_mask;
 			rx_buf = efx_rx_buffer(rx_queue, index);
 			rx_buf->dma_addr = dma_addr + efx->rx_ip_align;
@@ -635,6 +643,104 @@ static void efx_rx_deliver(struct efx_channel *channel, u8 *eh,
 		netif_receive_skb(skb);
 }
 
+/** efx_do_xdp: perform XDP processing on a received packet
+ *
+ * Returns true if packet should still be delivered.
+ */
+static bool efx_do_xdp(struct efx_nic *efx, struct efx_channel *channel,
+		       struct efx_rx_buffer *rx_buf, u8 **ehp)
+{
+	u8 rx_prefix[EFX_MAX_RX_PREFIX_SIZE];
+	struct efx_rx_queue *rx_queue;
+	struct bpf_prog *xdp_prog;
+	struct xdp_buff xdp;
+	u32 xdp_act;
+	s16 offset;
+	int err;
+
+	rcu_read_lock();
+	xdp_prog = rcu_dereference(efx->xdp_prog);
+	if (!xdp_prog) {
+		rcu_read_unlock();
+		return true;
+	}
+
+	rx_queue = efx_channel_get_rx_queue(channel);
+
+	if (unlikely(channel->rx_pkt_n_frags > 1)) {
+		/* We can't do XDP on fragmented packets - drop. */
+		rcu_read_unlock();
+		efx_free_rx_buffers(rx_queue, rx_buf,
+				    channel->rx_pkt_n_frags);
+		if (net_ratelimit())
+			netif_err(efx, rx_err, efx->net_dev,
+				  "XDP is not possible with multiple receive fragments (%d)\n",
+				  channel->rx_pkt_n_frags);
+		return false;
+	}
+
+	dma_sync_single_for_cpu(&efx->pci_dev->dev, rx_buf->dma_addr,
+				rx_buf->len, DMA_FROM_DEVICE);
+
+	/* Save the rx prefix. */
+	EFX_WARN_ON_PARANOID(efx->rx_prefix_size > EFX_MAX_RX_PREFIX_SIZE);
+	memcpy(rx_prefix, *ehp - efx->rx_prefix_size,
+	       efx->rx_prefix_size);
+
+	xdp.data = *ehp;
+	xdp.data_hard_start = xdp.data - XDP_PACKET_HEADROOM;
+
+	/* No support yet for XDP metadata */
+	xdp_set_data_meta_invalid(&xdp);
+	xdp.data_end = xdp.data + rx_buf->len;
+	xdp.rxq = &rx_queue->xdp_rxq_info;
+
+	xdp_act = bpf_prog_run_xdp(xdp_prog, &xdp);
+	rcu_read_unlock();
+
+	offset = (u8 *)xdp.data - *ehp;
+
+	switch (xdp_act) {
+	case XDP_PASS:
+		/* Fix up rx prefix. */
+		if (offset) {
+			*ehp += offset;
+			rx_buf->page_offset += offset;
+			rx_buf->len -= offset;
+			memcpy(*ehp - efx->rx_prefix_size, rx_prefix,
+			       efx->rx_prefix_size);
+		}
+		break;
+
+	case XDP_TX:
+		return -EOPNOTSUPP;
+
+	case XDP_REDIRECT:
+		err = xdp_do_redirect(efx->net_dev, &xdp, xdp_prog);
+		if (unlikely(err)) {
+			efx_free_rx_buffers(rx_queue, rx_buf, 1);
+			if (net_ratelimit())
+				netif_err(efx, rx_err, efx->net_dev,
+					  "XDP redirect failed (%d)\n", err);
+		}
+		break;
+
+	default:
+		bpf_warn_invalid_xdp_action(xdp_act);
+		efx_free_rx_buffers(rx_queue, rx_buf, 1);
+		break;
+
+	case XDP_ABORTED:
+		trace_xdp_exception(efx->net_dev, xdp_prog, xdp_act);
+		/* Fall through */
+	case XDP_DROP:
+		efx_free_rx_buffers(rx_queue, rx_buf, 1);
+		break;
+	}
+
+	return xdp_act == XDP_PASS;
+}
+
 /* Handle a received packet.  Second half: Touches packet payload. */
 void __efx_rx_packet(struct efx_channel *channel)
 {
@@ -663,6 +769,9 @@ void __efx_rx_packet(struct efx_channel *channel)
 		goto out;
 	}
 
+	if (!efx_do_xdp(efx, channel, rx_buf, &eh))
+		goto out;
+
 	if (unlikely(!(efx->net_dev->features & NETIF_F_RXCSUM)))
 		rx_buf->flags &= ~EFX_RX_PKT_CSUMMED;
 
@@ -731,6 +840,7 @@ void efx_init_rx_queue(struct efx_rx_queue *rx_queue)
 {
 	struct efx_nic *efx = rx_queue->efx;
 	unsigned int max_fill, trigger, max_trigger;
+	int rc = 0;
 
 	netif_dbg(rx_queue->efx, drv, rx_queue->efx->net_dev,
 		  "initialising RX queue %d\n", efx_rx_queue_index(rx_queue));
@@ -764,6 +874,19 @@ void efx_init_rx_queue(struct efx_rx_queue *rx_queue)
 	rx_queue->fast_fill_trigger = trigger;
 	rx_queue->refill_enabled = true;
 
+	/* Initialise XDP queue information */
+	rc = xdp_rxq_info_reg(&rx_queue->xdp_rxq_info, efx->net_dev,
+			      rx_queue->core_index);
+
+	if (rc) {
+		netif_err(efx, rx_err, efx->net_dev,
+			  "Failure to initialise XDP queue information rc=%d\n",
+			  rc);
+		efx->xdp_rxq_info_failed = true;
+	} else {
+		rx_queue->xdp_rxq_info_valid = true;
+	}
+
 	/* Set up RX descriptor ring */
 	efx_nic_init_rx(rx_queue);
 }
@@ -805,6 +928,11 @@ void efx_fini_rx_queue(struct efx_rx_queue *rx_queue)
 	}
 	kfree(rx_queue->page_ring);
 	rx_queue->page_ring = NULL;
+
+	if (rx_queue->xdp_rxq_info_valid)
+		xdp_rxq_info_unreg(&rx_queue->xdp_rxq_info);
+
+	rx_queue->xdp_rxq_info_valid = false;
 }
 
 void efx_remove_rx_queue(struct efx_rx_queue *rx_queue)

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