From: Fushuai Wang When a sf is created after a CPU has been taken offline, the IRQ pool may contain IRQs with affinity masks that include the offline CPU. Since only online CPUs should be considered for IRQ placement, cpumask_subset() check would fail because the iter_mask contains offline CPUs that are not present in req_mask, causing sf creation to fail. This is an example: 1. When mlx5 driver loads, it initializes the IRQ pools. For sf_ctrl_pool with ≤64 sf: - xa_num_irqs = {N, N} (There is only one slot) 2. When the first SF is created: - The ctrl IRQ is allocated with mask=cpu_online_mask={0-191} 2. We take CPU 20 offline 3. Existing ctl irq still have mask={0-191} 4. Create a new SF: - req_mask={0-19,21-191} - iter_mask={0-191} - {0-191} is NOT a subset of {0-19,21-191} - least_loaded_irq=NULL 5. Try to allocate a new irq via irq_pool_request_irq() 6. xa_alloc() fails because the pool is full(There is only one slot) 7. sf creation fails with error Use irq_get_effective_affinity_mask() instead, which returns the IRQ's actual effective affinity that already excludes offline CPUs. Fixes: 061f5b23588a ("net/mlx5: SF, Use all available cpu for setting cpu affinity") Suggested-by: Shay Drory Signed-off-by: Fushuai Wang --- v2->v3: Separate the patchset to two patches, reverse xmas tree coding style fix. v1->v2: Use mlx5_irq_get_affinity_mask() api previous discussion: https://lore.kernel.org/all/20260603072657.10868-1-fushuai.wang@linux.dev/T/#u https://lore.kernel.org/all/20260604125705.21241-1-fushuai.wang@linux.dev/T/#u drivers/net/ethernet/mellanox/mlx5/core/irq_affinity.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/net/ethernet/mellanox/mlx5/core/irq_affinity.c b/drivers/net/ethernet/mellanox/mlx5/core/irq_affinity.c index 994fe83da4be..a0bb8ee44e35 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/irq_affinity.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/irq_affinity.c @@ -105,9 +105,12 @@ irq_pool_find_least_loaded(struct mlx5_irq_pool *pool, const struct cpumask *req lockdep_assert_held(&pool->lock); xa_for_each_range(&pool->irqs, index, iter, start, end) { - struct cpumask *iter_mask = mlx5_irq_get_affinity_mask(iter); int iter_refcount = mlx5_irq_read_locked(iter); + const struct cpumask *iter_mask; + iter_mask = irq_get_effective_affinity_mask(mlx5_irq_get_irq(iter)); + if (!iter_mask) + continue; if (!cpumask_subset(iter_mask, req_mask)) /* skip IRQs with a mask which is not subset of req_mask */ continue; -- 2.36.1