iommu/vt-d: Add attach_deferred() helper

Implement a helper function to check whether a device's attach process
is deferred.

Fixes: 1ee0186b9a ("iommu/vt-d: Refactor find_domain() helper")
Cc: stable@vger.kernel.org # v5.5
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Acked-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/intel-iommu.c

@@ -762,6 +762,11 @@ static int iommu_dummy(struct device *dev)
 	return dev->archdata.iommu == DUMMY_DEVICE_DOMAIN_INFO;
 }
 
+static bool attach_deferred(struct device *dev)
+{
+	return dev->archdata.iommu == DEFER_DEVICE_DOMAIN_INFO;
+}
+
 /**
  * is_downstream_to_pci_bridge - test if a device belongs to the PCI
  *				 sub-hierarchy of a candidate PCI-PCI bridge
@@ -2510,8 +2515,7 @@ struct dmar_domain *find_domain(struct device *dev)
 {
 	struct device_domain_info *info;
 
-	if (unlikely(dev->archdata.iommu == DEFER_DEVICE_DOMAIN_INFO ||
-		     dev->archdata.iommu == DUMMY_DEVICE_DOMAIN_INFO))
+	if (unlikely(attach_deferred(dev) || iommu_dummy(dev)))
 		return NULL;
 
 	if (dev_is_pci(dev))
@@ -2527,7 +2531,7 @@ struct dmar_domain *find_domain(struct device *dev)
 
 static struct dmar_domain *deferred_attach_domain(struct device *dev)
 {
-	if (unlikely(dev->archdata.iommu == DEFER_DEVICE_DOMAIN_INFO)) {
+	if (unlikely(attach_deferred(dev))) {
 		struct iommu_domain *domain;
 
 		dev->archdata.iommu = NULL;
@@ -6133,7 +6137,7 @@ intel_iommu_aux_get_pasid(struct iommu_domain *domain, struct device *dev)
 static bool intel_iommu_is_attach_deferred(struct iommu_domain *domain,
 					   struct device *dev)
 {
-	return dev->archdata.iommu == DEFER_DEVICE_DOMAIN_INFO;
+	return attach_deferred(dev);
 }
 
 static int