Re: [PATCH v4 3/8] arm/irq: Keep track of irq affinities

[Julien Grall <julien@xxxxxxx>]

Hi Mykyta,

On 12/11/2025 10:51, Mykyta Poturai wrote:
> Currently on Arm the desc->affinity mask of an irq is never updated,
> which makes it hard to know the actual affinity of an interrupt.
>
> Fix this by updating the field in irq_set_affinity.
>
> Signed-off-by: Mykyta Poturai <mykyta_poturai@xxxxxxxx>
>
> v3->v4:
> * patch introduced
> ---
>   xen/arch/arm/irq.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/xen/arch/arm/irq.c b/xen/arch/arm/irq.c
> index 73e58a5108..28b40331f7 100644
> --- a/xen/arch/arm/irq.c
> +++ b/xen/arch/arm/irq.c
> @@ -219,7 +219,10 @@ static inline struct domain *irq_get_domain(struct 
> irq_desc *desc)
>   void irq_set_affinity(struct irq_desc *desc, const cpumask_t *mask)
>   {
>       if ( desc != NULL )
> +    {
> +        cpumask_copy(desc->affinity, mask);
irq_set_affinity() doesn't always seems to be called with ``desc->lock`` 
taken (see vgic_migrate_irq(), arch_move_irqs()). So I am not sure this 
is safe. You probably need to update the callers as well to always take 
the lock. irq_set_affinity() probably want to gain an 
ASSERT(spin_is_locked()) with some documentation on top of the function.
>           desc->handler->set_affinity(desc, mask);
> +    }
NIT: As there are multiple lines in the ``if``, I would consider 
reworking the logic so we return early when desc is NULL.
>   }
>   
>   int request_irq(unsigned int irq, unsigned int irqflags,
Cheers,

--
Julien Grall