net: mana: Allow irq_setup() to skip cpus for affinity

JIRA: https://issues.redhat.com/browse/RHEL-109583

commit 845c62c
Author: Shradha Gupta <shradhagupta@linux.microsoft.com>
Date:   Wed Jun 11 07:10:42 2025 -0700

    net: mana: Allow irq_setup() to skip cpus for affinity

    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@linux.microsoft.com>
    Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
    Reviewed-by: Yury Norov [NVIDIA] <yury.norov@gmail.com>

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>

Author: Maxim Levitsky

drivers/net/ethernet/microsoft/mana/gdma_main.c

@@ -1409,7 +1409,8 @@ 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);
@@ -1424,11 +1425,18 @@ 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;
@@ -1524,7 +1532,7 @@ 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;