iommu/vt-d: Implement is_attach_deferred iommu ops entry

As a domain is now attached to a device earlier, we should
implement the is_attach_deferred call-back and use it to
defer the domain attach from iommu driver init to device
driver init when iommu is pre-enabled in kdump kernel.
Suggested-by: Tom Murphy <tmurphy@arista.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/intel-iommu.c

@@ -353,6 +353,8 @@ static void domain_context_clear(struct intel_iommu *iommu,
 static int domain_detach_iommu(struct dmar_domain *domain,
 			       struct intel_iommu *iommu);
 static bool device_is_rmrr_locked(struct device *dev);
+static int intel_iommu_attach_device(struct iommu_domain *domain,
+				     struct device *dev);
 
 #ifdef CONFIG_INTEL_IOMMU_DEFAULT_ON
 int dmar_disabled = 0;
@@ -378,6 +380,7 @@ int intel_iommu_gfx_mapped;
 EXPORT_SYMBOL_GPL(intel_iommu_gfx_mapped);
 
 #define DUMMY_DEVICE_DOMAIN_INFO ((struct device_domain_info *)(-1))
+#define DEFER_DEVICE_DOMAIN_INFO ((struct device_domain_info *)(-2))
 static DEFINE_SPINLOCK(device_domain_lock);
 static LIST_HEAD(device_domain_list);
 
@@ -2408,8 +2411,18 @@ static struct dmar_domain *find_domain(struct device *dev)
 {
 	struct device_domain_info *info;
 
+	if (unlikely(dev->archdata.iommu == DEFER_DEVICE_DOMAIN_INFO)) {
+		struct iommu_domain *domain;
+
+		dev->archdata.iommu = NULL;
+		domain = iommu_get_domain_for_dev(dev);
+		if (domain)
+			intel_iommu_attach_device(domain, dev);
+	}
+
 	/* No lock here, assumes no domain exit in normal case */
 	info = dev->archdata.iommu;
+
 	if (likely(info))
 		return info->domain;
 	return NULL;
@@ -5504,6 +5517,9 @@ static int intel_iommu_add_device(struct device *dev)
 
 	iommu_device_link(&iommu->iommu, dev);
 
+	if (translation_pre_enabled(iommu))
+		dev->archdata.iommu = DEFER_DEVICE_DOMAIN_INFO;
+
 	group = iommu_group_get_for_dev(dev);
 
 	if (IS_ERR(group))
@@ -5828,6 +5844,12 @@ intel_iommu_aux_get_pasid(struct iommu_domain *domain, struct device *dev)
 			dmar_domain->default_pasid : -EINVAL;
 }
 
+static bool intel_iommu_is_attach_deferred(struct iommu_domain *domain,
+					   struct device *dev)
+{
+	return dev->archdata.iommu == DEFER_DEVICE_DOMAIN_INFO;
+}
+
 const struct iommu_ops intel_iommu_ops = {
 	.capable		= intel_iommu_capable,
 	.domain_alloc		= intel_iommu_domain_alloc,
@@ -5850,6 +5872,7 @@ const struct iommu_ops intel_iommu_ops = {
 	.dev_feat_enabled	= intel_iommu_dev_feat_enabled,
 	.dev_enable_feat	= intel_iommu_dev_enable_feat,
 	.dev_disable_feat	= intel_iommu_dev_disable_feat,
+	.is_attach_deferred	= intel_iommu_is_attach_deferred,
 	.pgsize_bitmap		= INTEL_IOMMU_PGSIZES,
 };