iommu: Introduce iommu_get_nesting

Add iommu_get_nesting() which allow to retrieve whether a domain
uses nested stages.

Signed-off-by: Eric Auger <eric.auger@redhat.com>

drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c

@@ -2731,6 +2731,13 @@ static int arm_smmu_enable_nesting(struct iommu_domain *domain)
 	return ret;
 }
 
+static bool arm_smmu_get_nesting(struct iommu_domain *domain)
+{
+	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
+
+	return smmu_domain->stage == ARM_SMMU_DOMAIN_NESTED;
+}
+
 static int arm_smmu_of_xlate(struct device *dev, struct of_phandle_args *args)
 {
 	return iommu_fwspec_add_ids(dev, args->args, 1);
@@ -2845,6 +2852,7 @@ static struct iommu_ops arm_smmu_ops = {
 	.release_device		= arm_smmu_release_device,
 	.device_group		= arm_smmu_device_group,
 	.enable_nesting		= arm_smmu_enable_nesting,
+	.get_nesting		= arm_smmu_get_nesting,
 	.of_xlate		= arm_smmu_of_xlate,
 	.get_resv_regions	= arm_smmu_get_resv_regions,
 	.put_resv_regions	= generic_iommu_put_resv_regions,

drivers/iommu/arm/arm-smmu/arm-smmu.c

@@ -1522,6 +1522,13 @@ static int arm_smmu_enable_nesting(struct iommu_domain *domain)
 	return ret;
 }
 
+static bool arm_smmu_get_nesting(struct iommu_domain *domain)
+{
+	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
+
+	return smmu_domain->stage == ARM_SMMU_DOMAIN_NESTED;
+}
+
 static int arm_smmu_set_pgtable_quirks(struct iommu_domain *domain,
 		unsigned long quirks)
 {
@@ -1595,6 +1602,7 @@ static struct iommu_ops arm_smmu_ops = {
 	.probe_finalize		= arm_smmu_probe_finalize,
 	.device_group		= arm_smmu_device_group,
 	.enable_nesting		= arm_smmu_enable_nesting,
+	.get_nesting		= arm_smmu_get_nesting,
 	.set_pgtable_quirks	= arm_smmu_set_pgtable_quirks,
 	.of_xlate		= arm_smmu_of_xlate,
 	.get_resv_regions	= arm_smmu_get_resv_regions,

drivers/iommu/intel/iommu.c

@@ -5602,6 +5602,18 @@ intel_iommu_enable_nesting(struct iommu_domain *domain)
 	return ret;
 }
 
+static bool intel_iommu_get_nesting(struct iommu_domain *domain)
+{
+	struct dmar_domain *dmar_domain = to_dmar_domain(domain);
+	bool nesting;
+
+	spin_lock_irqsave(&device_domain_lock, flags);
+	nesting =  dmar_domain->flags & DOMAIN_FLAG_NESTING_MODE &&
+		   !(dmar_domain->flags & DOMAIN_FLAG_USE_FIRST_LEVEL);
+	spin_unlock_irqrestore(&device_domain_lock, flags);
+	return nesting;
+}
+
 /*
  * Check that the device does not live on an external facing PCI port that is
  * marked as untrusted. Such devices should not be able to apply quirks and
@@ -5639,6 +5651,7 @@ const struct iommu_ops intel_iommu_ops = {
 	.domain_alloc		= intel_iommu_domain_alloc,
 	.domain_free		= intel_iommu_domain_free,
 	.enable_nesting		= intel_iommu_enable_nesting,
+	.get_nesting		= intel_iommu_get_nesting,
 	.attach_dev		= intel_iommu_attach_device,
 	.detach_dev		= intel_iommu_detach_device,
 	.aux_attach_dev		= intel_iommu_aux_attach_device,

drivers/iommu/iommu.c

@@ -2842,6 +2842,16 @@ int iommu_enable_nesting(struct iommu_domain *domain)
 }
 EXPORT_SYMBOL_GPL(iommu_enable_nesting);
 
+bool iommu_get_nesting(struct iommu_domain *domain)
+{
+	if (domain->type != IOMMU_DOMAIN_UNMANAGED)
+		return false;
+	if (!domain->ops->enable_nesting)
+		return false;
+	return domain->ops->get_nesting(domain);
+}
+EXPORT_SYMBOL_GPL(iommu_get_nesting);
+
 int iommu_set_pgtable_quirks(struct iommu_domain *domain,
 		unsigned long quirk)
 {

include/linux/iommu.h

@@ -213,6 +213,7 @@ struct iommu_iotlb_gather {
  *                  group and attached to the groups domain
  * @device_group: find iommu group for a particular device
  * @enable_nesting: Enable nesting
+ * @get_nesting: get whether the domain uses nested stages
  * @set_pgtable_quirks: Set io page table quirks (IO_PGTABLE_QUIRK_*)
  * @get_resv_regions: Request list of reserved regions for a device
  * @put_resv_regions: Free list of reserved regions for a device
@@ -271,6 +272,7 @@ struct iommu_ops {
 	void (*probe_finalize)(struct device *dev);
 	struct iommu_group *(*device_group)(struct device *dev);
 	int (*enable_nesting)(struct iommu_domain *domain);
+	bool (*get_nesting)(struct iommu_domain *domain);
 	int (*set_pgtable_quirks)(struct iommu_domain *domain,
 				  unsigned long quirks);
 
@@ -690,6 +692,7 @@ struct iommu_sva *iommu_sva_bind_device(struct device *dev,
 					void *drvdata);
 void iommu_sva_unbind_device(struct iommu_sva *handle);
 u32 iommu_sva_get_pasid(struct iommu_sva *handle);
+bool iommu_get_nesting(struct iommu_domain *domain);
 
 #else /* CONFIG_IOMMU_API */
 
@@ -1108,6 +1111,11 @@ static inline struct iommu_fwspec *dev_iommu_fwspec_get(struct device *dev)
 {
 	return NULL;
 }
+
+static inline bool iommu_get_nesting(struct iommu_domain *domain)
+{
+	return false;
+}
 #endif /* CONFIG_IOMMU_API */
 
 /**