3 files changed, 58 insertions, 0 deletions

diff --git a/drivers/net/ethernet/amazon/ena/ena_ethtool.c b/drivers/net/ethernet/amazon/ena/ena_ethtool.c
index 67b2338f8fb3..533b2fbdeef1 100644
--- a/drivers/net/ethernet/amazon/ena/ena_ethtool.c
+++ b/drivers/net/ethernet/amazon/ena/ena_ethtool.c
@@ -94,6 +94,7 @@ static const struct ena_stats ena_stats_rx_strings[] = {
         ENA_STAT_RX_ENTRY(dma_mapping_err),
         ENA_STAT_RX_ENTRY(bad_desc_num),
         ENA_STAT_RX_ENTRY(rx_copybreak_pkt),
+        ENA_STAT_RX_ENTRY(empty_rx_ring),
 };
 
 static const struct ena_stats ena_stats_ena_com_strings[] = {
diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.c b/drivers/net/ethernet/amazon/ena/ena_netdev.c
index 4e9fbddd3b47..3c366bfbbab1 100644
--- a/drivers/net/ethernet/amazon/ena/ena_netdev.c
+++ b/drivers/net/ethernet/amazon/ena/ena_netdev.c
@@ -190,6 +190,7 @@ static void ena_init_io_rings(struct ena_adapter *adapter)
                 rxr->sgl_size = adapter->max_rx_sgl_size;
                 rxr->smoothed_interval =
                         ena_com_get_nonadaptive_moderation_interval_rx(ena_dev);
+                rxr->empty_rx_queue = 0;
         }
 }
 
@@ -2619,6 +2620,58 @@ static void check_for_missing_tx_completions(struct ena_adapter *adapter)
         adapter->last_monitored_tx_qid = i % adapter->num_queues;
 }
 
+/* trigger napi schedule after 2 consecutive detections */
+#define EMPTY_RX_REFILL 2
+/* For the rare case where the device runs out of Rx descriptors and the
+ * napi handler failed to refill new Rx descriptors (due to a lack of memory
+ * for example).
+ * This case will lead to a deadlock:
+ * The device won't send interrupts since all the new Rx packets will be dropped
+ * The napi handler won't allocate new Rx descriptors so the device will be
+ * able to send new packets.
+ *
+ * This scenario can happen when the kernel's vm.min_free_kbytes is too small.
+ * It is recommended to have at least 512MB, with a minimum of 128MB for
+ * constrained environment).
+ *
+ * When such a situation is detected - Reschedule napi
+ */
+static void check_for_empty_rx_ring(struct ena_adapter *adapter)
+{
+        struct ena_ring *rx_ring;
+        int i, refill_required;
+
+        if (!test_bit(ENA_FLAG_DEV_UP, &adapter->flags))
+                return;
+
+        if (test_bit(ENA_FLAG_TRIGGER_RESET, &adapter->flags))
+                return;
+
+        for (i = 0; i < adapter->num_queues; i++) {
+                rx_ring = &adapter->rx_ring[i];
+
+                refill_required =
+                        ena_com_sq_empty_space(rx_ring->ena_com_io_sq);
+                if (unlikely(refill_required == (rx_ring->ring_size - 1))) {
+                        rx_ring->empty_rx_queue++;
+
+                        if (rx_ring->empty_rx_queue >= EMPTY_RX_REFILL) {
+                                u64_stats_update_begin(&rx_ring->syncp);
+                                rx_ring->rx_stats.empty_rx_ring++;
+                                u64_stats_update_end(&rx_ring->syncp);
+
+                                netif_err(adapter, drv, adapter->netdev,
+                                          "trigger refill for ring %d\n", i);
+
+                                napi_schedule(rx_ring->napi);
+                                rx_ring->empty_rx_queue = 0;
+                        }
+                } else {
+                        rx_ring->empty_rx_queue = 0;
+                }
+        }
+}
+
 /* Check for keep alive expiration */
 static void check_for_missing_keep_alive(struct ena_adapter *adapter)
 {
@@ -2673,6 +2726,8 @@ static void ena_timer_service(unsigned long data)
 
         check_for_missing_tx_completions(adapter);
 
+        check_for_empty_rx_ring(adapter);
+
         if (debug_area)
                 ena_dump_stats_to_buf(adapter, debug_area);
 
diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.h b/drivers/net/ethernet/amazon/ena/ena_netdev.h
index 0e22bce6239d..8828f1d6dd22 100644
--- a/drivers/net/ethernet/amazon/ena/ena_netdev.h
+++ b/drivers/net/ethernet/amazon/ena/ena_netdev.h
@@ -184,6 +184,7 @@ struct ena_stats_rx {
         u64 dma_mapping_err;
         u64 bad_desc_num;
         u64 rx_copybreak_pkt;
+        u64 empty_rx_ring;
 };
 
 struct ena_ring {
@@ -231,6 +232,7 @@ struct ena_ring {
                 struct ena_stats_tx tx_stats;
                 struct ena_stats_rx rx_stats;
         };
+        int empty_rx_queue;
 } ____cacheline_aligned;
 
 struct ena_stats_dev {