Re: [RFC PATCH] xen: Introduce extra IRQ count domain creation parameter

[Jan Beulich <jbeulich@xxxxxxxx>]

On 16.05.2025 15:50, Teddy Astie wrote:
> When doing PCI Passthrough with high-IRQ devices (e.g NVMe drives),
> the default limit may be unefficient as not all domains requires
> more IRQs.
> 
> Introduce a new parameter to allow the toolstack to tune the IRQ
> count if more is required.
> 
> Signed-off-by: Teddy Astie <teddy.astie@xxxxxxxxxx>

Sure, why not (suitably fleshed out, as e.g. you say ...

> ---
> 0 extra_irqs is meaningful, though I am not sure how to expose this
> special case.
> 
> This of course wants libxl support next.

... here).

> --- a/xen/common/domain.c
> +++ b/xen/common/domain.c
> @@ -912,10 +912,12 @@ struct domain *domain_create(domid_t domid,
>  
>  #ifdef CONFIG_HAS_PIRQ
>      if ( !is_hardware_domain(d) )
> -        d->nr_pirqs = nr_static_irqs + extra_domU_irqs;
> +        d->nr_pirqs = nr_static_irqs + config->extra_irqs ?: extra_domU_irqs;

I think you're missing parentheses here around the ?: expression.

Jan