Subject: Re: [PATCH v6 10/29] iommu/vt-d: Implement minor tweaks for NMI irqs

From: Thomas Gleixner <[email-masked]>
Date: Fri, 06 May 2022 23:23:23 +0200

On Thu, May 05 2022 at 16:59, Ricardo Neri wrote:
> The Intel IOMMU interrupt remapping driver already programs correctly the
> delivery mode of individual irqs as per their irq_data. Improve handling
> of NMIs. Allow only one irq per NMI. Also, it is not necessary to cleanup
> irq vectors after updating affinity.

Structuring a changelog in paragraphs might make it readable. New lines
exist for a reason.

> NMIs do not have associated vectors.

Again. NMI has an vector associated, but it is not subject to dynamic
vector management.

> diff --git a/drivers/iommu/intel/irq_remapping.c b/drivers/iommu/intel/irq_remapping.c
> index fb2d71bea98d..791a9331e257 100644
> --- a/drivers/iommu/intel/irq_remapping.c
> +++ b/drivers/iommu/intel/irq_remapping.c
> @@ -1198,8 +1198,12 @@ intel_ir_set_affinity(struct irq_data *data, const struct cpumask *mask,
>  	 * After this point, all the interrupts will start arriving
>  	 * at the new destination. So, time to cleanup the previous
>  	 * vector allocation.
> +	 *
> +	 * Do it only for non-NMI irqs. NMIs don't have associated
> +	 * vectors.

See above.

>  	 */
> -	send_cleanup_vector(cfg);
> +	if (cfg->delivery_mode != APIC_DELIVERY_MODE_NMI)
> +		send_cleanup_vector(cfg);

So this needs to be replicated for all invocations of
send_cleanup_vector(), right? Why can't you put it into that function?
  
>  	return IRQ_SET_MASK_OK_DONE;
>  }
> @@ -1352,6 +1356,9 @@ static int intel_irq_remapping_alloc(struct irq_domain *domain,
>  	if (info->type == X86_IRQ_ALLOC_TYPE_PCI_MSI)
>  		info->flags &= ~X86_IRQ_ALLOC_CONTIGUOUS_VECTORS;
>  
> +	if ((info->flags & X86_IRQ_ALLOC_AS_NMI) && nr_irqs != 1)
> +		return -EINVAL;

This cannot be reached when the vector allocation domain already
rejected it, but copy & pasta is wonderful and increases the line count.

Thanks,

        tglx