ixgbe: Use watchdog check in favor of BPF for detecting latched timestamp

This patch removes ixgbe_ptp_match, and the corresponding packet filtering from
ixgbe driver. This code was previously causing some issues within the hotpath of
the driver. However the code also provided a check against possible frozen Rx
timestamp due to dropped packets when the Rx ring is full. This patch provides a
replacement solution based on the watchdog.

To this end, whenever a packet consumes the Rx timestamp it stores the jiffy
value in the rx_ring structure. Watchdog updates its own jiffy timer whenever
there is no valid timestamp in the registers.

If watchdog detects a valid timestamp in the registers, (meaning that no Rx
packet has consumed it yet) it will check which time is most recent, the last
time in the watchdog, or any time in the rx_rings. If the most recent "event"
was more than 5seconds ago, it will flush the Rx timestamp and print a warning
message to the syslog.

Reported-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/ixgbe/ixgbe.h

@@ -35,6 +35,7 @@
 #include <linux/cpumask.h>
 #include <linux/aer.h>
 #include <linux/if_vlan.h>
+#include <linux/jiffies.h>
 
 #include <linux/clocksource.h>
 #include <linux/net_tstamp.h>
@@ -231,6 +232,7 @@ struct ixgbe_ring {
 		struct ixgbe_tx_buffer *tx_buffer_info;
 		struct ixgbe_rx_buffer *rx_buffer_info;
 	};
+	unsigned long last_rx_timestamp;
 	unsigned long state;
 	u8 __iomem *tail;
 	dma_addr_t dma;			/* phys. address of descriptor ring */
@@ -581,10 +583,10 @@ struct ixgbe_adapter {
 	struct ptp_clock *ptp_clock;
 	struct ptp_clock_info ptp_caps;
 	unsigned long last_overflow_check;
+	unsigned long last_rx_ptp_check;
 	spinlock_t tmreg_lock;
 	struct cyclecounter cc;
 	struct timecounter tc;
-	int rx_hwtstamp_filter;
 	u32 base_incval;
 
 	/* SR-IOV */
@@ -749,9 +751,10 @@ static inline struct netdev_queue *txring_txq(const struct ixgbe_ring *ring)
 extern void ixgbe_ptp_init(struct ixgbe_adapter *adapter);
 extern void ixgbe_ptp_stop(struct ixgbe_adapter *adapter);
 extern void ixgbe_ptp_overflow_check(struct ixgbe_adapter *adapter);
+extern void ixgbe_ptp_rx_hang(struct ixgbe_adapter *adapter);
 extern void ixgbe_ptp_tx_hwtstamp(struct ixgbe_q_vector *q_vector,
 				  struct sk_buff *skb);
-extern void ixgbe_ptp_rx_hwtstamp(struct ixgbe_q_vector *q_vector,
+extern void ixgbe_ptp_rx_hwtstamp(struct ixgbe_ring *rx_ring,
 				  union ixgbe_adv_rx_desc *rx_desc,
 				  struct sk_buff *skb);
 extern int ixgbe_ptp_hwtstamp_ioctl(struct ixgbe_adapter *adapter,

drivers/net/ethernet/intel/ixgbe/ixgbe_main.c

@@ -1441,7 +1441,7 @@ static void ixgbe_process_skb_fields(struct ixgbe_ring *rx_ring,
 
 	ixgbe_rx_checksum(rx_ring, rx_desc, skb);
 
-	ixgbe_ptp_rx_hwtstamp(rx_ring->q_vector, rx_desc, skb);
+	ixgbe_ptp_rx_hwtstamp(rx_ring, rx_desc, skb);
 
 	if ((dev->features & NETIF_F_HW_VLAN_RX) &&
 	    ixgbe_test_staterr(rx_desc, IXGBE_RXD_STAT_VP)) {
@@ -5534,6 +5534,8 @@ static void ixgbe_watchdog_link_is_up(struct ixgbe_adapter *adapter)
 		break;
 	}
 
+	adapter->last_rx_ptp_check = jiffies;
+
 	if (adapter->flags2 & IXGBE_FLAG2_PTP_ENABLED)
 		ixgbe_ptp_start_cyclecounter(adapter);
 
@@ -5887,6 +5889,7 @@ static void ixgbe_service_task(struct work_struct *work)
 	ixgbe_fdir_reinit_subtask(adapter);
 	ixgbe_check_hang_subtask(adapter);
 	ixgbe_ptp_overflow_check(adapter);
+	ixgbe_ptp_rx_hang(adapter);
 
 	ixgbe_service_event_complete(adapter);
 }

drivers/net/ethernet/intel/ixgbe/ixgbe_ptp.c

@@ -101,10 +101,6 @@
 #define NSECS_PER_SEC 1000000000ULL
 #endif
 
-static struct sock_filter ptp_filter[] = {
-	PTP_FILTER
-};
-
 /**
  * ixgbe_ptp_setup_sdp
  * @hw: the hardware private structure
@@ -428,64 +424,44 @@ void ixgbe_ptp_overflow_check(struct ixgbe_adapter *adapter)
 }
 
 /**
- * ixgbe_ptp_match - determine if this skb matches a ptp packet
- * @skb: pointer to the skb
- * @hwtstamp: pointer to the hwtstamp_config to check
- *
- * Determine whether the skb should have been timestamped, assuming the
- * hwtstamp was set via the hwtstamp ioctl. Returns non-zero when the packet
- * should have a timestamp waiting in the registers, and 0 otherwise.
+ * ixgbe_ptp_rx_hang - detect error case when Rx timestamp registers latched
+ * @adapter: private network adapter structure
  *
- * V1 packets have to check the version type to determine whether they are
- * correct. However, we can't directly access the data because it might be
- * fragmented in the SKB, in paged memory. In order to work around this, we
- * use skb_copy_bits which will properly copy the data whether it is in the
- * paged memory fragments or not. We have to copy the IP header as well as the
- * message type.
+ * this watchdog task is scheduled to detect error case where hardware has
+ * dropped an Rx packet that was timestamped when the ring is full. The
+ * particular error is rare but leaves the device in a state unable to timestamp
+ * any future packets.
  */
-static int ixgbe_ptp_match(struct sk_buff *skb, int rx_filter)
+void ixgbe_ptp_rx_hang(struct ixgbe_adapter *adapter)
 {
-	struct iphdr iph;
-	u8 msgtype;
-	unsigned int type, offset;
-
-	if (rx_filter == HWTSTAMP_FILTER_NONE)
-		return 0;
-
-	type = sk_run_filter(skb, ptp_filter);
-
-	if (likely(rx_filter == HWTSTAMP_FILTER_PTP_V2_EVENT))
-		return type & PTP_CLASS_V2;
+	struct ixgbe_hw *hw = &adapter->hw;
+	struct ixgbe_ring *rx_ring;
+	u32 tsyncrxctl = IXGBE_READ_REG(hw, IXGBE_TSYNCRXCTL);
+	unsigned long rx_event;
+	int n;
 
-	/* For the remaining cases actually check message type */
-	switch (type) {
-	case PTP_CLASS_V1_IPV4:
-		skb_copy_bits(skb, OFF_IHL, &iph, sizeof(iph));
-		offset = ETH_HLEN + (iph.ihl << 2) + UDP_HLEN + OFF_PTP_CONTROL;
-		break;
-	case PTP_CLASS_V1_IPV6:
-		offset = OFF_PTP6 + OFF_PTP_CONTROL;
-		break;
-	default:
-		/* other cases invalid or handled above */
-		return 0;
+	/* if we don't have a valid timestamp in the registers, just update the
+	 * timeout counter and exit
+	 */
+	if (!(tsyncrxctl & IXGBE_TSYNCRXCTL_VALID)) {
+		adapter->last_rx_ptp_check = jiffies;
+		return;
 	}
 
-	/* Make sure our buffer is long enough */
-	if (skb->len < offset)
-		return 0;
+	/* determine the most recent watchdog or rx_timestamp event */
+	rx_event = adapter->last_rx_ptp_check;
+	for (n = 0; n < adapter->num_rx_queues; n++) {
+		rx_ring = adapter->rx_ring[n];
+		if (time_after(rx_ring->last_rx_timestamp, rx_event))
+			rx_event = rx_ring->last_rx_timestamp;
+	}
 
-	skb_copy_bits(skb, offset, &msgtype, sizeof(msgtype));
+	/* only need to read the high RXSTMP register to clear the lock */
+	if (time_is_before_jiffies(rx_event + 5*HZ)) {
+		IXGBE_READ_REG(hw, IXGBE_RXSTMPH);
+		adapter->last_rx_ptp_check = jiffies;
 
-	switch (rx_filter) {
-	case HWTSTAMP_FILTER_PTP_V1_L4_SYNC:
-		return (msgtype == IXGBE_RXMTRL_V1_SYNC_MSG);
-		break;
-	case HWTSTAMP_FILTER_PTP_V1_L4_DELAY_REQ:
-		return (msgtype == IXGBE_RXMTRL_V1_DELAY_REQ_MSG);
-		break;
-	default:
-		return 0;
+		e_warn(drv, "clearing RX Timestamp hang");
 	}
 }
 
@@ -545,7 +521,7 @@ void ixgbe_ptp_tx_hwtstamp(struct ixgbe_q_vector *q_vector,
  * value, then store that result into the shhwtstamps structure which
  * is passed up the network stack
  */
-void ixgbe_ptp_rx_hwtstamp(struct ixgbe_q_vector *q_vector,
+void ixgbe_ptp_rx_hwtstamp(struct ixgbe_ring *rx_ring,
 			   union ixgbe_adv_rx_desc *rx_desc,
 			   struct sk_buff *skb)
 {
@@ -557,43 +533,32 @@ void ixgbe_ptp_rx_hwtstamp(struct ixgbe_q_vector *q_vector,
 	unsigned long flags;
 
 	/* we cannot process timestamps on a ring without a q_vector */
-	if (!q_vector || !q_vector->adapter)
+	if (!rx_ring->q_vector || !rx_ring->q_vector->adapter)
 		return;
 
-	adapter = q_vector->adapter;
+	adapter = rx_ring->q_vector->adapter;
 	hw = &adapter->hw;
 
-	if (likely(!ixgbe_ptp_match(skb, adapter->rx_hwtstamp_filter)))
+	if (unlikely(!ixgbe_test_staterr(rx_desc, IXGBE_RXDADV_STAT_TS)))
 		return;
 
+	/*
+	 * Read the tsyncrxctl register afterwards in order to prevent taking an
+	 * I/O hit on every packet.
+	 */
 	tsyncrxctl = IXGBE_READ_REG(hw, IXGBE_TSYNCRXCTL);
-
-	/* Check if we have a valid timestamp and make sure the skb should
-	 * have been timestamped */
 	if (!(tsyncrxctl & IXGBE_TSYNCRXCTL_VALID))
 		return;
 
 	/*
-	 * Always read the registers, in order to clear a possible fault
-	 * because of stagnant RX timestamp values for a packet that never
-	 * reached the queue.
+	 * Update the last_rx_timestamp timer in order to enable watchdog check
+	 * for error case of latched timestamp on a dropped packet.
 	 */
+	rx_ring->last_rx_timestamp = jiffies;
+
 	regval |= (u64)IXGBE_READ_REG(hw, IXGBE_RXSTMPL);
 	regval |= (u64)IXGBE_READ_REG(hw, IXGBE_RXSTMPH) << 32;
 
-	/*
-	 * If the timestamp bit is set in the packet's descriptor, we know the
-	 * timestamp belongs to this packet. No other packet can be
-	 * timestamped until the registers for timestamping have been read.
-	 * Therefor only one packet with this bit can be in the queue at a
-	 * time, and the rx timestamp values that were in the registers belong
-	 * to this packet.
-	 *
-	 * If nothing went wrong, then it should have a skb_shared_tx that we
-	 * can turn into a skb_shared_hwtstamps.
-	 */
-	if (unlikely(!ixgbe_test_staterr(rx_desc, IXGBE_RXDADV_STAT_TS)))
-		return;
 
 	spin_lock_irqsave(&adapter->tmreg_lock, flags);
 	ns = timecounter_cyc2time(&adapter->tc, regval);
@@ -698,9 +663,6 @@ int ixgbe_ptp_hwtstamp_ioctl(struct ixgbe_adapter *adapter,
 		return 0;
 	}
 
-	/* Store filter value for later use */
-	adapter->rx_hwtstamp_filter = config.rx_filter;
-
 	/* define ethertype filter for timestamping L2 packets */
 	if (is_l2)
 		IXGBE_WRITE_REG(hw, IXGBE_ETQF(IXGBE_ETQF_FILTER_1588),
@@ -902,10 +864,6 @@ void ixgbe_ptp_init(struct ixgbe_adapter *adapter)
 		return;
 	}
 
-	/* initialize the ptp filter */
-	if (ptp_filter_init(ptp_filter, ARRAY_SIZE(ptp_filter)))
-		e_dev_warn("ptp_filter_init failed\n");
-
 	spin_lock_init(&adapter->tmreg_lock);
 
 	adapter->ptp_clock = ptp_clock_register(&adapter->ptp_caps,