iommu: Add is_attach_deferred call-back to iommu-ops

This new call-back will be used to check if the domain attach need be
deferred for now. If yes, the domain attach/detach will return directly.
Signed-off-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/iommu.c

@@ -1283,6 +1283,10 @@ 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;
 
@@ -1324,6 +1328,10 @@ EXPORT_SYMBOL_GPL(iommu_attach_device);
 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))
+		return;
+
 	if (unlikely(domain->ops->detach_dev == NULL))
 		return;
 

include/linux/iommu.h

@@ -225,6 +225,7 @@ struct iommu_ops {
 	u32 (*domain_get_windows)(struct iommu_domain *domain);
 
 	int (*of_xlate)(struct device *dev, struct of_phandle_args *args);
+	bool (*is_attach_deferred)(struct iommu_domain *domain, struct device *dev);
 
 	unsigned long pgsize_bitmap;
 };