iommu: Implement DOMAIN_ATTR_PAGING attribute

This attribute of a domain can be queried to find out if the
domain supports setting up page-tables using the iommu_map()
and iommu_unmap() functions.
Signed-off-by: Joerg Roedel <joro@8bytes.org>

drivers/iommu/iommu.c

@@ -869,6 +869,7 @@ int iommu_domain_get_attr(struct iommu_domain *domain,
 			  enum iommu_attr attr, void *data)
 {
 	struct iommu_domain_geometry *geometry;
+	bool *paging;
 	int ret = 0;
 
 	switch (attr) {
@@ -876,6 +877,10 @@ int iommu_domain_get_attr(struct iommu_domain *domain,
 		geometry  = data;
 		*geometry = domain->geometry;
 
+		break;
+	case DOMAIN_ATTR_PAGING:
+		paging  = data;
+		*paging = (domain->ops->pgsize_bitmap != 0UL);
 		break;
 	default:
 		if (!domain->ops->domain_get_attr)

include/linux/iommu.h

@@ -59,6 +59,7 @@ struct iommu_domain {
 
 enum iommu_attr {
 	DOMAIN_ATTR_GEOMETRY,
+	DOMAIN_ATTR_PAGING,
 	DOMAIN_ATTR_MAX,
 };