[PATCH v4 4/5] net: mana: Allow irq_setup() to skip cpus for affinity

[Shradha Gupta]

In order to prepare the MANA driver to allocate the MSI-X IRQs
dynamically, we need to enhance irq_setup() to allow skipping
affinitizing IRQs to the first CPU sibling group.

This would be for cases when the number of IRQs is less than or equal
to the number of online CPUs. In such cases for dynamically added IRQs
the first CPU sibling group would already be affinitized with HWC IRQ.

Signed-off-by: Shradha Gupta <shradhagupta@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
Reviewed-by: Yury Norov [NVIDIA] <yury.norov@xxxxxxxxx>
---
 Changes in v4
 * fix commit description
 * avoided using next_cpumask: label in the irq_setup()
---
 drivers/net/ethernet/microsoft/mana/gdma_main.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/microsoft/mana/gdma_main.c b/drivers/net/ethernet/microsoft/mana/gdma_main.c
index f9e8d4d1ba3a..763a548c4a2b 100644
--- a/drivers/net/ethernet/microsoft/mana/gdma_main.c
+++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c
@@ -1329,7 +1329,8 @@ void mana_gd_free_res_map(struct gdma_resource *r)
  * do the same thing.
  */
 
-static int irq_setup(unsigned int *irqs, unsigned int len, int node)
+static int irq_setup(unsigned int *irqs, unsigned int len, int node,
+		     bool skip_first_cpu)
 {
 	const struct cpumask *next, *prev = cpu_none_mask;
 	cpumask_var_t cpus __free(free_cpumask_var);
@@ -1344,11 +1345,18 @@ static int irq_setup(unsigned int *irqs, unsigned int len, int node)
 		while (weight > 0) {
 			cpumask_andnot(cpus, next, prev);
 			for_each_cpu(cpu, cpus) {
+				cpumask_andnot(cpus, cpus, topology_sibling_cpumask(cpu));
+				--weight;
+
+				if (unlikely(skip_first_cpu)) {
+					skip_first_cpu = false;
+					continue;
+				}
+
 				if (len-- == 0)
 					goto done;
+
 				irq_set_affinity_and_hint(*irqs++, topology_sibling_cpumask(cpu));
-				cpumask_andnot(cpus, cpus, topology_sibling_cpumask(cpu));
-				--weight;
 			}
 		}
 		prev = next;
@@ -1444,7 +1452,7 @@ static int mana_gd_setup_irqs(struct pci_dev *pdev)
 		}
 	}
 
-	err = irq_setup(irqs, (nvec - start_irq_index), gc->numa_node);
+	err = irq_setup(irqs, nvec - start_irq_index, gc->numa_node, false);
 	if (err)
 		goto free_irq;
 
-- 
2.34.1