net/mlx5: Fix get vector affinity helper function

mlx5_get_vector_affinity used to call pci_irq_get_affinity and after
reverting the patch that sets the device affinity via PCI_IRQ_AFFINITY
API, calling pci_irq_get_affinity becomes useless and it breaks RDMA
mlx5 users.  To fix this, this patch provides an alternative way to
retrieve IRQ vector affinity using legacy IRQ API, following
smp_affinity read procfs implementation.

Fixes: 231243c ("Revert mlx5: move affinity hints assignments to generic code")
Fixes: a435393 ("mlx5: move affinity hints assignments to generic code")
Cc: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

include/linux/mlx5/driver.h

@@ -36,6 +36,7 @@
 #include <linux/kernel.h>
 #include <linux/completion.h>
 #include <linux/pci.h>
+#include <linux/irq.h>
 #include <linux/spinlock_types.h>
 #include <linux/semaphore.h>
 #include <linux/slab.h>
@@ -1231,7 +1232,23 @@ enum {
 static inline const struct cpumask *
 mlx5_get_vector_affinity(struct mlx5_core_dev *dev, int vector)
 {
-	return pci_irq_get_affinity(dev->pdev, MLX5_EQ_VEC_COMP_BASE + vector);
+	const struct cpumask *mask;
+	struct irq_desc *desc;
+	unsigned int irq;
+	int eqn;
+	int err;
+
+	err = mlx5_vector2eqn(dev, vector, &eqn, &irq);
+	if (err)
+		return NULL;
+
+	desc = irq_to_desc(irq);
+#ifdef CONFIG_GENERIC_IRQ_EFFECTIVE_AFF_MASK
+	mask = irq_data_get_effective_affinity_mask(&desc->irq_data);
+#else
+	mask = desc->irq_common_data.affinity;
+#endif
+	return mask;
 }
 
 #endif /* MLX5_DRIVER_H */