net/mlx5: Fix driver load with single msix vector

When a PCI device has just one msix vector available, we want to share
this vector between async and completion events. Current code fails to
do that assuming it will always have at least one dedicated vector for
completion events. Fix this by detecting when the pool contains just a
single vector.

Fixes: 3354822 ("net/mlx5: Use dynamic msix vectors allocation")
Signed-off-by: Eli Cohen <elic@nvidia.com>
Reviewed-by: Shay Drory <shayd@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

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

@@ -565,15 +565,21 @@ void mlx5_irqs_release_vectors(struct mlx5_irq **irqs, int nirqs)
 int mlx5_irqs_request_vectors(struct mlx5_core_dev *dev, u16 *cpus, int nirqs,
 			      struct mlx5_irq **irqs, struct cpu_rmap **rmap)
 {
+	struct mlx5_irq_table *table = mlx5_irq_table_get(dev);
+	struct mlx5_irq_pool *pool = table->pcif_pool;
 	struct irq_affinity_desc af_desc;
 	struct mlx5_irq *irq;
+	int offset = 1;
 	int i;
 
+	if (!pool->xa_num_irqs.max)
+		offset = 0;
+
 	af_desc.is_managed = false;
 	for (i = 0; i < nirqs; i++) {
 		cpumask_clear(&af_desc.mask);
 		cpumask_set_cpu(cpus[i], &af_desc.mask);
-		irq = mlx5_irq_request(dev, i + 1, &af_desc, rmap);
+		irq = mlx5_irq_request(dev, i + offset, &af_desc, rmap);
 		if (IS_ERR(irq))
 			break;
 		irqs[i] = irq;