net/mlx5e: Recover Send Queue (SQ) from error state

An error TX completion (CQE) which arrived on a specific SQ indicates
that this SQ got moved by the hardware to error state, which means all
pending and incoming TX requests are dropped or will be dropped and no
further "Good" CQEs will be generated for that SQ.

Before this patch TX completions (CQEs) were not monitored and were
handled as a regular CQE. This caused the SQ to stay in an error state,
making it useless for xmiting new packets.

Mitigation plan:
In case of an error completion, schedule a recovery work which would do
the following:
- Mark the TXQ as DRV_XOFF to disable new packets to arrive from the
  stack
- NAPI to flush all pending SQ WQEs (via flush_in_error_en bit) to
  release SW and HW resources(SKB, DMA, etc) and have the SQ and CQ
  consumer/producer indices synced.
- Modify the SQ state ERR -> RST -> RDY (restart the SQ).
- Reactivate the SQ and reset SQ cc and pc

If we identify two consecutive requests for SQ recover in less than
500 msecs, drop the recover request to avoid CPU overload, as this
scenario most likely happened due to a severe repeated bug.

In addition, add SQ recover SW counter to monitor successful recoveries.
Signed-off-by: Eran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/en.h

@@ -122,6 +122,7 @@
 #define MLX5E_MAX_NUM_SQS              (MLX5E_MAX_NUM_CHANNELS * MLX5E_MAX_NUM_TC)
 #define MLX5E_TX_CQ_POLL_BUDGET        128
 #define MLX5E_UPDATE_STATS_INTERVAL    200 /* msecs */
+#define MLX5E_SQ_RECOVER_MIN_INTERVAL  500 /* msecs */
 
 #define MLX5E_ICOSQ_MAX_WQEBBS \
 	(DIV_ROUND_UP(sizeof(struct mlx5e_umr_wqe), MLX5_SEND_WQE_BB))
@@ -332,6 +333,7 @@ struct mlx5e_sq_dma {
 
 enum {
 	MLX5E_SQ_STATE_ENABLED,
+	MLX5E_SQ_STATE_RECOVERING,
 	MLX5E_SQ_STATE_IPSEC,
 };
 
@@ -378,6 +380,10 @@ struct mlx5e_txqsq {
 	struct mlx5e_channel      *channel;
 	int                        txq_ix;
 	u32                        rate_limit;
+	struct mlx5e_txqsq_recover {
+		struct work_struct         recover_work;
+		u64                        last_recover;
+	} recover;
 } ____cacheline_aligned_in_smp;
 
 struct mlx5e_xdpsq {

drivers/net/ethernet/mellanox/mlx5/core/en_main.c

@@ -956,6 +956,7 @@ static int mlx5e_alloc_txqsq_db(struct mlx5e_txqsq *sq, int numa)
 	return 0;
 }
 
+static void mlx5e_sq_recover(struct work_struct *work);
 static int mlx5e_alloc_txqsq(struct mlx5e_channel *c,
 			     int txq_ix,
 			     struct mlx5e_params *params,
@@ -974,6 +975,7 @@ static int mlx5e_alloc_txqsq(struct mlx5e_channel *c,
 	sq->txq_ix    = txq_ix;
 	sq->uar_map   = mdev->mlx5e_res.bfreg.map;
 	sq->min_inline_mode = params->tx_min_inline_mode;
+	INIT_WORK(&sq->recover.recover_work, mlx5e_sq_recover);
 	if (MLX5_IPSEC_DEV(c->priv->mdev))
 		set_bit(MLX5E_SQ_STATE_IPSEC, &sq->state);
 
@@ -1040,6 +1042,7 @@ static int mlx5e_create_sq(struct mlx5_core_dev *mdev,
 		MLX5_SET(sqc,  sqc, min_wqe_inline_mode, csp->min_inline_mode);
 
 	MLX5_SET(sqc,  sqc, state, MLX5_SQC_STATE_RST);
+	MLX5_SET(sqc,  sqc, flush_in_error_en, 1);
 
 	MLX5_SET(wq,   wq, wq_type,       MLX5_WQ_TYPE_CYCLIC);
 	MLX5_SET(wq,   wq, uar_page,      mdev->mlx5e_res.bfreg.index);
@@ -1158,9 +1161,20 @@ static int mlx5e_open_txqsq(struct mlx5e_channel *c,
 	return err;
 }
 
+static void mlx5e_reset_txqsq_cc_pc(struct mlx5e_txqsq *sq)
+{
+	WARN_ONCE(sq->cc != sq->pc,
+		  "SQ 0x%x: cc (0x%x) != pc (0x%x)\n",
+		  sq->sqn, sq->cc, sq->pc);
+	sq->cc = 0;
+	sq->dma_fifo_cc = 0;
+	sq->pc = 0;
+}
+
 static void mlx5e_activate_txqsq(struct mlx5e_txqsq *sq)
 {
 	sq->txq = netdev_get_tx_queue(sq->channel->netdev, sq->txq_ix);
+	clear_bit(MLX5E_SQ_STATE_RECOVERING, &sq->state);
 	set_bit(MLX5E_SQ_STATE_ENABLED, &sq->state);
 	netdev_tx_reset_queue(sq->txq);
 	netif_tx_start_queue(sq->txq);
@@ -1205,6 +1219,107 @@ static void mlx5e_close_txqsq(struct mlx5e_txqsq *sq)
 	mlx5e_free_txqsq(sq);
 }
 
+static int mlx5e_wait_for_sq_flush(struct mlx5e_txqsq *sq)
+{
+	unsigned long exp_time = jiffies + msecs_to_jiffies(2000);
+
+	while (time_before(jiffies, exp_time)) {
+		if (sq->cc == sq->pc)
+			return 0;
+
+		msleep(20);
+	}
+
+	netdev_err(sq->channel->netdev,
+		   "Wait for SQ 0x%x flush timeout (sq cc = 0x%x, sq pc = 0x%x)\n",
+		   sq->sqn, sq->cc, sq->pc);
+
+	return -ETIMEDOUT;
+}
+
+static int mlx5e_sq_to_ready(struct mlx5e_txqsq *sq, int curr_state)
+{
+	struct mlx5_core_dev *mdev = sq->channel->mdev;
+	struct net_device *dev = sq->channel->netdev;
+	struct mlx5e_modify_sq_param msp = {0};
+	int err;
+
+	msp.curr_state = curr_state;
+	msp.next_state = MLX5_SQC_STATE_RST;
+
+	err = mlx5e_modify_sq(mdev, sq->sqn, &msp);
+	if (err) {
+		netdev_err(dev, "Failed to move sq 0x%x to reset\n", sq->sqn);
+		return err;
+	}
+
+	memset(&msp, 0, sizeof(msp));
+	msp.curr_state = MLX5_SQC_STATE_RST;
+	msp.next_state = MLX5_SQC_STATE_RDY;
+
+	err = mlx5e_modify_sq(mdev, sq->sqn, &msp);
+	if (err) {
+		netdev_err(dev, "Failed to move sq 0x%x to ready\n", sq->sqn);
+		return err;
+	}
+
+	return 0;
+}
+
+static void mlx5e_sq_recover(struct work_struct *work)
+{
+	struct mlx5e_txqsq_recover *recover =
+		container_of(work, struct mlx5e_txqsq_recover,
+			     recover_work);
+	struct mlx5e_txqsq *sq = container_of(recover, struct mlx5e_txqsq,
+					      recover);
+	struct mlx5_core_dev *mdev = sq->channel->mdev;
+	struct net_device *dev = sq->channel->netdev;
+	u8 state;
+	int err;
+
+	err = mlx5_core_query_sq_state(mdev, sq->sqn, &state);
+	if (err) {
+		netdev_err(dev, "Failed to query SQ 0x%x state. err = %d\n",
+			   sq->sqn, err);
+		return;
+	}
+
+	if (state != MLX5_RQC_STATE_ERR) {
+		netdev_err(dev, "SQ 0x%x not in ERROR state\n", sq->sqn);
+		return;
+	}
+
+	netif_tx_disable_queue(sq->txq);
+
+	if (mlx5e_wait_for_sq_flush(sq))
+		return;
+
+	/* If the interval between two consecutive recovers per SQ is too
+	 * short, don't recover to avoid infinite loop of ERR_CQE -> recover.
+	 * If we reached this state, there is probably a bug that needs to be
+	 * fixed. let's keep the queue close and let tx timeout cleanup.
+	 */
+	if (jiffies_to_msecs(jiffies - recover->last_recover) <
+	    MLX5E_SQ_RECOVER_MIN_INTERVAL) {
+		netdev_err(dev, "Recover SQ 0x%x canceled, too many error CQEs\n",
+			   sq->sqn);
+		return;
+	}
+
+	/* At this point, no new packets will arrive from the stack as TXQ is
+	 * marked with QUEUE_STATE_DRV_XOFF. In addition, NAPI cleared all
+	 * pending WQEs.  SQ can safely reset the SQ.
+	 */
+	if (mlx5e_sq_to_ready(sq, state))
+		return;
+
+	mlx5e_reset_txqsq_cc_pc(sq);
+	sq->stats.recover++;
+	recover->last_recover = jiffies;
+	mlx5e_activate_txqsq(sq);
+}
+
 static int mlx5e_open_icosq(struct mlx5e_channel *c,
 			    struct mlx5e_params *params,
 			    struct mlx5e_sq_param *param,

drivers/net/ethernet/mellanox/mlx5/core/en_stats.c

@@ -61,6 +61,7 @@ static const struct counter_desc sw_stats_desc[] = {
 	{ MLX5E_DECLARE_STAT(struct mlx5e_sw_stats, tx_queue_dropped) },
 	{ MLX5E_DECLARE_STAT(struct mlx5e_sw_stats, tx_xmit_more) },
 	{ MLX5E_DECLARE_STAT(struct mlx5e_sw_stats, tx_cqe_err) },
+	{ MLX5E_DECLARE_STAT(struct mlx5e_sw_stats, tx_recover) },
 	{ MLX5E_DECLARE_STAT(struct mlx5e_sw_stats, rx_wqe_err) },
 	{ MLX5E_DECLARE_STAT(struct mlx5e_sw_stats, rx_mpwqe_filler) },
 	{ MLX5E_DECLARE_STAT(struct mlx5e_sw_stats, rx_buff_alloc_err) },
@@ -155,6 +156,7 @@ static void mlx5e_grp_sw_update_stats(struct mlx5e_priv *priv)
 			s->tx_queue_wake	+= sq_stats->wake;
 			s->tx_queue_dropped	+= sq_stats->dropped;
 			s->tx_cqe_err		+= sq_stats->cqe_err;
+			s->tx_recover		+= sq_stats->recover;
 			s->tx_xmit_more		+= sq_stats->xmit_more;
 			s->tx_csum_partial_inner += sq_stats->csum_partial_inner;
 			s->tx_csum_none		+= sq_stats->csum_none;
@@ -1106,6 +1108,7 @@ static const struct counter_desc sq_stats_desc[] = {
 	{ MLX5E_DECLARE_TX_STAT(struct mlx5e_sq_stats, dropped) },
 	{ MLX5E_DECLARE_TX_STAT(struct mlx5e_sq_stats, xmit_more) },
 	{ MLX5E_DECLARE_TX_STAT(struct mlx5e_sq_stats, cqe_err) },
+	{ MLX5E_DECLARE_TX_STAT(struct mlx5e_sq_stats, recover) },
 };
 
 static const struct counter_desc ch_stats_desc[] = {

drivers/net/ethernet/mellanox/mlx5/core/en_stats.h

@@ -79,6 +79,7 @@ struct mlx5e_sw_stats {
 	u64 tx_queue_dropped;
 	u64 tx_xmit_more;
 	u64 tx_cqe_err;
+	u64 tx_recover;
 	u64 rx_wqe_err;
 	u64 rx_mpwqe_filler;
 	u64 rx_buff_alloc_err;
@@ -199,6 +200,7 @@ struct mlx5e_sq_stats {
 	u64 wake;
 	u64 dropped;
 	u64 cqe_err;
+	u64 recover;
 };
 
 struct mlx5e_ch_stats {

drivers/net/ethernet/mellanox/mlx5/core/en_tx.c

@@ -469,9 +469,13 @@ bool mlx5e_poll_tx_cq(struct mlx5e_cq *cq, int napi_budget)
 		wqe_counter = be16_to_cpu(cqe->wqe_counter);
 
 		if (unlikely(cqe->op_own >> 4 == MLX5_CQE_REQ_ERR)) {
-			if (!sq->stats.cqe_err)
+			if (!test_and_set_bit(MLX5E_SQ_STATE_RECOVERING,
+					      &sq->state)) {
 				mlx5e_dump_error_cqe(sq,
 						     (struct mlx5_err_cqe *)cqe);
+				queue_work(cq->channel->priv->wq,
+					   &sq->recover.recover_work);
+			}
 			sq->stats.cqe_err++;
 		}
 
@@ -528,7 +532,9 @@ bool mlx5e_poll_tx_cq(struct mlx5e_cq *cq, int napi_budget)
 	netdev_tx_completed_queue(sq->txq, npkts, nbytes);
 
 	if (netif_tx_queue_stopped(sq->txq) &&
-	    mlx5e_wqc_has_room_for(&sq->wq, sq->cc, sq->pc, MLX5E_SQ_STOP_ROOM)) {
+	    mlx5e_wqc_has_room_for(&sq->wq, sq->cc, sq->pc,
+				   MLX5E_SQ_STOP_ROOM) &&
+	    !test_bit(MLX5E_SQ_STATE_RECOVERING, &sq->state)) {
 		netif_tx_wake_queue(sq->txq);
 		sq->stats.wake++;
 	}