[PATCH v8 04/12] genirq/affinity: Add cpumask to struct irq_affinity

Daniel Wagner
2025-09-05T15:00:04Z

Pass a cpumask to irq_create_affinity_masks as an additional constraint
to consider when creating the affinity masks. This allows the caller to
exclude specific CPUs, e.g., isolated CPUs (see the 'isolcpus' kernel
command-line parameter).

Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Daniel Wagner <wagi@kernel.org>
---
include/linux/interrupt.h | 16 ++++++++++------
kernel/irq/affinity.c | 12 ++++++++++--
2 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 51b6484c049345c75816c4a63b4efa813f42f27b..b1a230953514da57e30e601727cd0e94796153d3 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -284,18 +284,22 @@ struct irq_affinity_notify {
* @nr_sets: The number of interrupt sets for which affinity
* spreading is required
* @set_size: Array holding the size of each interrupt set
+ * @mask: cpumask that constrains which CPUs to consider when
+ * calculating the number and size of the interrupt sets
* @calc_sets: Callback for calculating the number and size
* of interrupt sets
* @priv: Private data for usage by @calc_sets, usually a
* pointer to driver/device specific data.
*/
struct irq_affinity {
- unsigned int pre_vectors;
- unsigned int post_vectors;
- unsigned int nr_sets;
- unsigned int set_size[IRQ_AFFINITY_MAX_SETS];
- void (*calc_sets)(struct irq_affinity *, unsigned int nvecs);
- void *priv;
+ unsigned int pre_vectors;
+ unsigned int post_vectors;
+ unsigned int nr_sets;
+ unsigned int set_size[IRQ_AFFINITY_MAX_SETS];
+ const struct cpumask *mask;
+ void (*calc_sets)(struct irq_affinity *,
+ unsigned int nvecs);
+ void *priv;
};

/**
diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c
index 4013e6ad2b2f1cb91de12bb428b3281105f7d23b..c68156f7847a7920103e39124676d06191304ef6 100644
--- a/kernel/irq/affinity.c
+++ b/kernel/irq/affinity.c
@@ -70,7 +70,13 @@ irq_create_affinity_masks(unsigned int nvecs, struct irq_affinity *affd)
*/
for (i = 0, usedvecs = 0; i < affd->nr_sets; i++) {
unsigned int nr_masks, this_vecs = affd->set_size[i];
- struct cpumask *result = group_cpus_evenly(this_vecs, &nr_masks);
+ struct cpumask *result;
+
+ if (affd->mask)
+ result = group_mask_cpus_evenly(this_vecs, affd->mask,
+ &nr_masks);
+ else
+ result = group_cpus_evenly(this_vecs, &nr_masks);

if (!result) {
kfree(masks);
@@ -115,7 +121,9 @@ unsigned int irq_calc_affinity_vectors(unsigned int minvec, unsigned int maxvec,
if (resv > minvec)
return 0;

- if (affd->calc_sets) {
+ if (affd->mask) {
+ set_vecs = cpumask_weight(affd->mask);
+ } else if (affd->calc_sets) {
set_vecs = maxvec - resv;
} else {
cpus_read_lock();

--
2.51.0