[PATCH v2 0/2] net/mlx5: Only consider online CPUs in affinity subset check

[PATCH v2 0/2] net/mlx5: Only consider online CPUs in affinity subset check

[Fushuai Wang]

From: Fushuai Wang <wangfushuai@baidu.com>

Hi all,

When an SF is created after a CPU has been taken offline, the IRQ affinity
check fails because existing IRQs in the pool may have affinity masks that
include the now-offline CPU. This causes SF creation to fail even though
suitable online CPUs are available.

This series fixes this issue and includes a small cleanup:

Patch 1 folds cpumask_copy() into cpumask_andnot() for better code clarity
in comp_irq_request_sf().

Patch 2 filters affinity masks to only consider effective CPUs before the
subset check, ensuring SF creation succeeds when CPUs have been taken offline.

--WANG

Fushuai Wang (2):
  net/mlx5: Simplify cpumask operations in comp_irq_request_sf()
  net/mlx5: Use effective affinity mask for IRQ selection

 drivers/net/ethernet/mellanox/mlx5/core/eq.c           | 3 +--
 drivers/net/ethernet/mellanox/mlx5/core/irq_affinity.c | 5 ++++-
 2 files changed, 5 insertions(+), 3 deletions(-)

-- 
2.36.1

[PATCH v2 1/2] net/mlx5: Simplify cpumask operations in comp_irq_request_sf()

[Fushuai Wang]

From: Fushuai Wang <wangfushuai@baidu.com>

Combine cpumask_copy() and cpumask_andnot() into a single
cpumask_andnot() since the function can take cpu_online_mask
directly as the source.

Signed-off-by: Fushuai Wang <wangfushuai@baidu.com>
Reviewed-by: Shay Drory <shayd@nvidia.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/eq.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/eq.c b/drivers/net/ethernet/mellanox/mlx5/core/eq.c
index 22a637111aa2..d11ec263d53c 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/eq.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/eq.c
@@ -886,8 +886,7 @@ static int comp_irq_request_sf(struct mlx5_core_dev *dev, u16 vecidx)
 		return -ENOMEM;
 
 	af_desc->is_managed = false;
-	cpumask_copy(&af_desc->mask, cpu_online_mask);
-	cpumask_andnot(&af_desc->mask, &af_desc->mask, &table->used_cpus);
+	cpumask_andnot(&af_desc->mask, cpu_online_mask, &table->used_cpus);
 	irq = mlx5_irq_affinity_request(dev, pool, af_desc);
 	if (IS_ERR(irq)) {
 		kvfree(af_desc);
-- 
2.36.1

[PATCH v2 2/2] net/mlx5: Use effective affinity mask for IRQ selection

[Fushuai Wang]

From: Fushuai Wang <wangfushuai@baidu.com>

When an 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.

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 <shayd@nvidia.com>
Signed-off-by: Fushuai Wang <wangfushuai@baidu.com>
---
 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..c5d784cbc8e4 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);
+		const struct cpumask *iter_mask;
 		int iter_refcount = mlx5_irq_read_locked(iter);
 
+		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

Re: [PATCH v2 2/2] net/mlx5: Use effective affinity mask for IRQ selection

[Shay Drori]

On 04/06/2026 15:57, Fushuai Wang wrote:
> External email: Use caution opening links or attachments
> 
> 
> From: Fushuai Wang <wangfushuai@baidu.com>
> 
> When an 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.

can you please add the example/repro from the prev discussion?
Sorry I wasn't clear I want it the commit message...

> 
> 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 <shayd@nvidia.com>
> Signed-off-by: Fushuai Wang <wangfushuai@baidu.com>
> ---
>   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..c5d784cbc8e4 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);
> +               const struct cpumask *iter_mask;
>                  int iter_refcount = mlx5_irq_read_locked(iter);

can you please keep revers xmas tree here as well?

> 
> +               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
> 

Re: [PATCH v2 0/2] net/mlx5: Only consider online CPUs in affinity subset check

[Shay Drori]

On 04/06/2026 15:57, Fushuai Wang wrote:
> External email: Use caution opening links or attachments
> 
> 
> From: Fushuai Wang <wangfushuai@baidu.com>
> 
> Hi all,
> 
> When an SF is created after a CPU has been taken offline, the IRQ affinity
> check fails because existing IRQs in the pool may have affinity masks that
> include the now-offline CPU. This causes SF creation to fail even though
> suitable online CPUs are available.
> 
> This series fixes this issue and includes a small cleanup:
> 
> Patch 1 folds cpumask_copy() into cpumask_andnot() for better code clarity
> in comp_irq_request_sf().
> 
> Patch 2 filters affinity masks to only consider effective CPUs before the
> subset check, ensuring SF creation succeeds when CPUs have been taken offline.

Thanks for the patches.
two points:
1) you need to add branch name to the title (PATCH net ...)
2) you need to keep a change-log.

The first patch is net-next material, and the second patch is net.
I think it would be better to send each one separately to its own branch.
sorry didn't notice on prev review...

> 
> --WANG
> 
> Fushuai Wang (2):
>    net/mlx5: Simplify cpumask operations in comp_irq_request_sf()
>    net/mlx5: Use effective affinity mask for IRQ selection
> 
>   drivers/net/ethernet/mellanox/mlx5/core/eq.c           | 3 +--
>   drivers/net/ethernet/mellanox/mlx5/core/irq_affinity.c | 5 ++++-
>   2 files changed, 5 insertions(+), 3 deletions(-)
> 
> --
> 2.36.1
>