net: ena: add detection and recovery mechanism for handling missed/misrouted MSI-X

A mechanism for detection of stuck Rx/Tx rings due to missed or
misrouted interrupts.
Check if there are unhandled completion descriptors before the first
MSI-X interrupt arrived.
The check is per queue and per interrupt vector.
Once such condition is detected, driver and device reset is scheduled.
Signed-off-by: Netanel Belgazal <netanel@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/amazon/ena/ena_eth_com.c

@@ -504,3 +504,14 @@ int ena_com_tx_comp_req_id_get(struct ena_com_io_cq *io_cq, u16 *req_id)
 
 	return 0;
 }
+
+bool ena_com_cq_empty(struct ena_com_io_cq *io_cq)
+{
+	struct ena_eth_io_rx_cdesc_base *cdesc;
+
+	cdesc = ena_com_get_next_rx_cdesc(io_cq);
+	if (cdesc)
+		return false;
+	else
+		return true;
+}

drivers/net/ethernet/amazon/ena/ena_eth_com.h

@@ -88,6 +88,8 @@ int ena_com_add_single_rx_desc(struct ena_com_io_sq *io_sq,
 
 int ena_com_tx_comp_req_id_get(struct ena_com_io_cq *io_cq, u16 *req_id);
 
+bool ena_com_cq_empty(struct ena_com_io_cq *io_cq);
+
 static inline void ena_com_unmask_intr(struct ena_com_io_cq *io_cq,
 				       struct ena_eth_io_intr_reg *intr_reg)
 {

drivers/net/ethernet/amazon/ena/ena_netdev.c

@@ -158,6 +158,8 @@ static void ena_init_io_rings_common(struct ena_adapter *adapter,
 	ring->per_napi_packets = 0;
 	ring->per_napi_bytes = 0;
 	ring->cpu = 0;
+	ring->first_interrupt = false;
+	ring->no_interrupt_event_cnt = 0;
 	u64_stats_init(&ring->syncp);
 }
 
@@ -1274,6 +1276,9 @@ static irqreturn_t ena_intr_msix_io(int irq, void *data)
 {
 	struct ena_napi *ena_napi = data;
 
+	ena_napi->tx_ring->first_interrupt = true;
+	ena_napi->rx_ring->first_interrupt = true;
+
 	napi_schedule_irqoff(&ena_napi->napi);
 
 	return IRQ_HANDLED;
@@ -2648,8 +2653,32 @@ static void ena_fw_reset_device(struct work_struct *work)
 	rtnl_unlock();
 }
 
-static int check_missing_comp_in_queue(struct ena_adapter *adapter,
-				       struct ena_ring *tx_ring)
+static int check_for_rx_interrupt_queue(struct ena_adapter *adapter,
+					struct ena_ring *rx_ring)
+{
+	if (likely(rx_ring->first_interrupt))
+		return 0;
+
+	if (ena_com_cq_empty(rx_ring->ena_com_io_cq))
+		return 0;
+
+	rx_ring->no_interrupt_event_cnt++;
+
+	if (rx_ring->no_interrupt_event_cnt == ENA_MAX_NO_INTERRUPT_ITERATIONS) {
+		netif_err(adapter, rx_err, adapter->netdev,
+			  "Potential MSIX issue on Rx side Queue = %d. Reset the device\n",
+			  rx_ring->qid);
+		adapter->reset_reason = ENA_REGS_RESET_MISS_INTERRUPT;
+		smp_mb__before_atomic();
+		set_bit(ENA_FLAG_TRIGGER_RESET, &adapter->flags);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static int check_missing_comp_in_tx_queue(struct ena_adapter *adapter,
+					  struct ena_ring *tx_ring)
 {
 	struct ena_tx_buffer *tx_buf;
 	unsigned long last_jiffies;
@@ -2659,8 +2688,27 @@ static int check_missing_comp_in_queue(struct ena_adapter *adapter,
 	for (i = 0; i < tx_ring->ring_size; i++) {
 		tx_buf = &tx_ring->tx_buffer_info[i];
 		last_jiffies = tx_buf->last_jiffies;
-		if (unlikely(last_jiffies &&
-			     time_is_before_jiffies(last_jiffies + adapter->missing_tx_completion_to))) {
+
+		if (last_jiffies == 0)
+			/* no pending Tx at this location */
+			continue;
+
+		if (unlikely(!tx_ring->first_interrupt && time_is_before_jiffies(last_jiffies +
+			     2 * adapter->missing_tx_completion_to))) {
+			/* If after graceful period interrupt is still not
+			 * received, we schedule a reset
+			 */
+			netif_err(adapter, tx_err, adapter->netdev,
+				  "Potential MSIX issue on Tx side Queue = %d. Reset the device\n",
+				  tx_ring->qid);
+			adapter->reset_reason = ENA_REGS_RESET_MISS_INTERRUPT;
+			smp_mb__before_atomic();
+			set_bit(ENA_FLAG_TRIGGER_RESET, &adapter->flags);
+			return -EIO;
+		}
+
+		if (unlikely(time_is_before_jiffies(last_jiffies +
+				adapter->missing_tx_completion_to))) {
 			if (!tx_buf->print_once)
 				netif_notice(adapter, tx_err, adapter->netdev,
 					     "Found a Tx that wasn't completed on time, qid %d, index %d.\n",
@@ -2689,9 +2737,10 @@ static int check_missing_comp_in_queue(struct ena_adapter *adapter,
 	return rc;
 }
 
-static void check_for_missing_tx_completions(struct ena_adapter *adapter)
+static void check_for_missing_completions(struct ena_adapter *adapter)
 {
 	struct ena_ring *tx_ring;
+	struct ena_ring *rx_ring;
 	int i, budget, rc;
 
 	/* Make sure the driver doesn't turn the device in other process */
@@ -2710,8 +2759,13 @@ static void check_for_missing_tx_completions(struct ena_adapter *adapter)
 
 	for (i = adapter->last_monitored_tx_qid; i < adapter->num_queues; i++) {
 		tx_ring = &adapter->tx_ring[i];
+		rx_ring = &adapter->rx_ring[i];
+
+		rc = check_missing_comp_in_tx_queue(adapter, tx_ring);
+		if (unlikely(rc))
+			return;
 
-		rc = check_missing_comp_in_queue(adapter, tx_ring);
+		rc = check_for_rx_interrupt_queue(adapter, rx_ring);
 		if (unlikely(rc))
 			return;
 
@@ -2870,7 +2924,7 @@ static void ena_timer_service(struct timer_list *t)
 
 	check_for_admin_com_state(adapter);
 
-	check_for_missing_tx_completions(adapter);
+	check_for_missing_completions(adapter);
 
 	check_for_empty_rx_ring(adapter);
 

drivers/net/ethernet/amazon/ena/ena_netdev.h

@@ -122,6 +122,7 @@
  * We wait for 6 sec just to be on the safe side.
  */
 #define ENA_DEVICE_KALIVE_TIMEOUT	(6 * HZ)
+#define ENA_MAX_NO_INTERRUPT_ITERATIONS 3
 
 #define ENA_MMIO_DISABLE_REG_READ	BIT(0)
 
@@ -236,6 +237,9 @@ struct ena_ring {
 	/* The maximum header length the device can handle */
 	u8 tx_max_header_size;
 
+	bool first_interrupt;
+	u16 no_interrupt_event_cnt;
+
 	/* cpu for TPH */
 	int cpu;
 	 /* number of tx/rx_buffer_info's entries */

drivers/net/ethernet/amazon/ena/ena_regs_defs.h

@@ -60,6 +60,8 @@ enum ena_regs_reset_reason_types {
 	ENA_REGS_RESET_USER_TRIGGER		= 12,
 
 	ENA_REGS_RESET_GENERIC			= 13,
+
+	ENA_REGS_RESET_MISS_INTERRUPT		= 14,
 };
 
 /* ena_registers offsets */