ACK: [PATCH 1/1] UBUNTU: SAUCE: irqchip/gic-v3-its: Don't return errors in its_irq_domain_activate()

[Connor Kuehl]

On 1/8/20 2:41 PM, Sultan Alsawaf wrote:
> BugLink: https://bugs.launchpad.net/bugs/1857074
> 
> Commit bb9b428a5c83 ("genirq/irqdomain: Allow irq_domain_activate_irq() to fail")
> added error handling for when irq domain activation would fail. However,
> our irqchip driver was not written with the intention of handling domain
> activation failure. When an irqchip's domain activation function fails,
> __irq_domain_activate_irq() in kernel/irq/irqdomain.c parses the error
> and disables the parent irq domain in response. This is not what was
> intended to happen for ITS_FLAGS_WORKAROUND_CAVIUM_23144, which leaves
> IRQs erroneously disabled on some CPUs.
> 
> There is no legitimate failure case for its_irq_domain_activate(), so we
> don't need to subscribe to __irq_domain_activate_irq()'s error handling,
> and the current state of the driver cannot cope with the error handling
> anyway. To that end, always return 0 from its_irq_domain_activate() so
> that IRQs aren't erroneously disabled for machines with
> ITS_FLAGS_WORKAROUND_CAVIUM_23144.
> 
> Signed-off-by: Sultan Alsawaf <sultan.alsawaf at canonical.com>

Acked-by: Connor Kuehl <connor.kuehl at canonical.com>

> ---
>   drivers/irqchip/irq-gic-v3-its.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index 5cc27ad2abd1..67386413b907 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -2407,7 +2407,7 @@ static int its_irq_domain_activate(struct irq_domain *domain,
>   	cpu = cpumask_first_and(cpu_mask, cpu_online_mask);
>   	if (cpu >= nr_cpu_ids) {
>   		if (its_dev->its->flags & ITS_FLAGS_WORKAROUND_CAVIUM_23144)
> -			return -EINVAL;
> +			return 0;
>   
>   		cpu = cpumask_first(cpu_online_mask);
>   	}
>