Re: [PATCH 02/12] x86/apic: remove vector_allocation_cpumask hook

[Jan Beulich <jbeulich@xxxxxxxx>]

On 20.11.2025 10:06, Roger Pau Monne wrote:
> All implementations use the same hook which is a wrapper around
> cpumask_of(cpu).  Adjust callers to no longer use such dummy mask with a
> single CPU set, as the CPU is already known to the caller.  This removes a
> pair of usages of for_each_cpu().
> 
> No functional change intended.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
with one possible adjustment:

> @@ -688,12 +683,12 @@ next:
>                  release_old_vec(desc);
>          }
>  
> -        trace_irq_mask(TRC_HW_IRQ_ASSIGN_VECTOR, irq, vector, vec_mask);
> +        trace_irq_mask(TRC_HW_IRQ_ASSIGN_VECTOR, irq, vector, 
> cpumask_of(cpu));
>  
> -        for_each_cpu(new_cpu, vec_mask)
> -            per_cpu(vector_irq, new_cpu)[vector] = irq;
> +        per_cpu(vector_irq, cpu)[vector] = irq;
>          desc->arch.vector = vector;
> -        cpumask_copy(desc->arch.cpu_mask, vec_mask);
> +        cpumask_clear(desc->arch.cpu_mask);
> +        cpumask_set_cpu(cpu, desc->arch.cpu_mask);

This being a LOCKed operation, might we better use

        cpumask_copy(desc->arch.cpu_mask, cpumask_of(cpu));

here? Otoh I expect this to go away later in the series anyway, so possibly not
a big deal.

Jan