Re: [PATCH] iommu: Implement deferred domain attachment

[Jerry Snitselaar]

On Mon May 18 20, Joerg Roedel wrote:
> On Fri, May 15, 2020 at 08:23:13PM +0100, Robin Murphy wrote:
> > But that's not what this is; this is (supposed to be) the exact same "don't
> > actually perform the attach yet" logic as before, just restricting it to
> > default domains in the one place that it actually needs to be, so as not to
> > fundamentally bugger up iommu_attach_device() in a way that prevents it from
> > working as expected at the correct point later.
>
> You are right, that is better. I tested it and it seems to work. Updated
> diff attached, with a minor cleanup included. Mind sending it as a
> proper patch I can send upstream?
>
> Thanks,
>
> 	Joerg
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 7b375421afba..a9d02bc3ab5b 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -693,6 +693,15 @@ static int iommu_group_create_direct_mappings(struct iommu_group *group,
> 	return ret;
> }
>
> +static bool iommu_is_attach_deferred(struct iommu_domain *domain,
> +				     struct device *dev)
> +{
> +	if (domain->ops->is_attach_deferred)
> +		return domain->ops->is_attach_deferred(domain, dev);
> +
> +	return false;
> +}
> +
> /**
>  * iommu_group_add_device - add a device to an iommu group
>  * @group: the group into which to add the device (reference should be held)
> @@ -705,6 +714,7 @@ int iommu_group_add_device(struct iommu_group *group, struct device *dev)
> {
> 	int ret, i = 0;
> 	struct group_device *device;
> +	struct iommu_domain *domain;
>
> 	device = kzalloc(sizeof(*device), GFP_KERNEL);
> 	if (!device)
> @@ -747,7 +757,8 @@ int iommu_group_add_device(struct iommu_group *group, struct device *dev)
>
> 	mutex_lock(&group->mutex);
> 	list_add_tail(&device->list, &group->devices);
> -	if (group->domain)
> +	domain = group->domain;
> +	if (domain  && !iommu_is_attach_deferred(domain, dev))
> 		ret = __iommu_attach_device(group->domain, dev);
> 	mutex_unlock(&group->mutex);
> 	if (ret)
> @@ -1653,9 +1664,6 @@ static int __iommu_attach_device(struct iommu_domain *domain,
> 				 struct device *dev)
> {
> 	int ret;
> -	if ((domain->ops->is_attach_deferred != NULL) &&
> -	    domain->ops->is_attach_deferred(domain, dev))
> -		return 0;
>
> 	if (unlikely(domain->ops->attach_dev == NULL))
> 		return -ENODEV;
> @@ -1727,8 +1735,7 @@ EXPORT_SYMBOL_GPL(iommu_sva_unbind_gpasid);
> static void __iommu_detach_device(struct iommu_domain *domain,
> 				  struct device *dev)
> {
> -	if ((domain->ops->is_attach_deferred != NULL) &&
> -	    domain->ops->is_attach_deferred(domain, dev))
> +	if (iommu_is_attach_deferred(domain, dev))
> 		return;
>
> 	if (unlikely(domain->ops->detach_dev == NULL))
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This worked for me as well.