Re: [PATCH v1 2/8] iommu: Introduce a new iommu_group_replace_domain() API

[Baolu Lu <baolu.lu@linux.intel.com>]

On 2023/2/2 15:05, Nicolin Chen wrote:
> +/**
> + * iommu_group_replace_domain - replace the domain that a group is attached to
> + * @new_domain: new IOMMU domain to replace with
> + * @group: IOMMU group that will be attached to the new domain
> + *
> + * This API allows the group to switch domains without being forced to go to
> + * the blocking domain in-between.
> + *
> + * If the attached domain is a core domain (e.g. a default_domain), it will act
> + * just like the iommu_attach_group().

I am not following above two lines. Why and how could iommufd set a
core domain to an iommu_group?

> + */
> +int iommu_group_replace_domain(struct iommu_group *group,
> +			       struct iommu_domain *new_domain)
> +{
> +	int ret;
> +
> +	if (!new_domain)
> +		return -EINVAL;
> +
> +	mutex_lock(&group->mutex);
> +	ret = __iommu_group_set_domain(group, new_domain);
> +	if (ret) {
> +		if (__iommu_group_set_domain(group, group->domain))
> +			__iommu_group_set_core_domain(group);
> +	}
> +	mutex_unlock(&group->mutex);
> +	return ret;
> +}
> +EXPORT_SYMBOL_NS_GPL(iommu_group_replace_domain, IOMMUFD_INTERNAL);

Best regards,
baolu