From: Tariq Toukan <tariqt@mellanox.com>
Date: Sun, 2 Jul 2017 13:17:42 +0300
Subject: net/mlx5e: Stop NAPI when irq balancer changes affinity
Patch-mainline: v4.14-rc1
Git-commit: a8c2eb15797a0f0bf17734d365da7bdc3e263155
References: bsc#1046305 FATE#322943

NAPI context keeps rescheduling on same CPU as long as it's busy.
This doesn't give the oppurtunity for changes in irq affinities
to take effect.
Fix that by calling napi_complete_done() upon a change in affinity.
This would stop the NAPI and reschedule it on the new CPU.

Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/ethernet/mellanox/mlx5/core/en.h      |    3 +++
 drivers/net/ethernet/mellanox/mlx5/core/en_main.c |    5 +++++
 drivers/net/ethernet/mellanox/mlx5/core/en_txrx.c |   20 ++++++++++++++++++--
 3 files changed, 26 insertions(+), 2 deletions(-)

--- a/drivers/net/ethernet/mellanox/mlx5/core/en.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en.h
@@ -582,6 +582,9 @@ struct mlx5e_channel {
 	__be32                     mkey_be;
 	u8                         num_tc;
 
+	/* data path - accessed per napi poll */
+	struct irq_desc *irq_desc;
+
 	/* control */
 	struct mlx5e_priv         *priv;
 	struct mlx5_core_dev      *mdev;
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -1762,7 +1762,9 @@ static int mlx5e_open_channel(struct mlx
 	struct mlx5e_cq_moder icocq_moder = {0, 0};
 	struct net_device *netdev = priv->netdev;
 	struct mlx5e_channel *c;
+	unsigned int irq;
 	int err;
+	int eqn;
 
 	c = kzalloc_node(sizeof(*c), GFP_KERNEL, mlx5e_get_node(priv, ix));
 	if (!c)
@@ -1778,6 +1780,9 @@ static int mlx5e_open_channel(struct mlx
 	c->num_tc   = params->num_tc;
 	c->xdp      = !!params->xdp_prog;
 
+	mlx5_vector2eqn(priv->mdev, ix, &eqn, &irq);
+	c->irq_desc = irq_to_desc(irq);
+
 	netif_napi_add(netdev, &c->napi, mlx5e_napi_poll, 64);
 
 	err = mlx5e_open_cq(c, icocq_moder, &cparam->icosq_cq, &c->icosq.cq);
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_txrx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_txrx.c
@@ -30,8 +30,20 @@
  * SOFTWARE.
  */
 
+#include <linux/irq.h>
 #include "en.h"
 
+static inline bool mlx5e_channel_no_affinity_change(struct mlx5e_channel *c)
+{
+	int current_cpu = smp_processor_id();
+	const struct cpumask *aff;
+	struct irq_data *idata;
+
+	idata = irq_desc_get_irq_data(c->irq_desc);
+	aff = irq_data_get_affinity_mask(idata);
+	return cpumask_test_cpu(current_cpu, aff);
+}
+
 int mlx5e_napi_poll(struct napi_struct *napi, int budget)
 {
 	struct mlx5e_channel *c = container_of(napi, struct mlx5e_channel,
@@ -51,8 +63,12 @@ int mlx5e_napi_poll(struct napi_struct *
 
 	busy |= c->rq.post_wqes(&c->rq);
 
-	if (busy)
-		return budget;
+	if (busy) {
+		if (likely(mlx5e_channel_no_affinity_change(c)))
+			return budget;
+		if (work_done == budget)
+			work_done--;
+	}
 
 	if (unlikely(!napi_complete_done(napi, work_done)))
 		return work_done;