iommufd/selftest: Prepare for mock_viommu_alloc_domain_nested()

A nested domain now can be allocated for a parent domain or for a vIOMMU
object. Rework the existing allocators to prepare for the latter case.

Link: https://patch.msgid.link/r/f62894ad8ccae28a8a616845947fe4b76135d79b.1730836219.git.nicolinc@nvidia.com
Reviewed-by: Kevin Tian <[email protected]>
Reviewed-by: Jason Gunthorpe <[email protected]>
Signed-off-by: Nicolin Chen <[email protected]>
Signed-off-by: Jason Gunthorpe <[email protected]>

Author: nicolinc

drivers/iommu/iommufd/selftest.c

@@ -318,55 +318,39 @@ static struct iommu_domain *mock_domain_alloc_paging(struct device *dev)
 	return &mock->domain;
 }
 
-static struct iommu_domain *
-__mock_domain_alloc_nested(struct mock_iommu_domain *mock_parent,
-			   const struct iommu_hwpt_selftest *user_cfg)
+static struct mock_iommu_domain_nested *
+__mock_domain_alloc_nested(const struct iommu_user_data *user_data)
 {
 	struct mock_iommu_domain_nested *mock_nested;
-	int i;
+	struct iommu_hwpt_selftest user_cfg;
+	int rc, i;
+
+	if (user_data->type != IOMMU_HWPT_DATA_SELFTEST)
+		return ERR_PTR(-EOPNOTSUPP);
+
+	rc = iommu_copy_struct_from_user(&user_cfg, user_data,
+					 IOMMU_HWPT_DATA_SELFTEST, iotlb);
+	if (rc)
+		return ERR_PTR(rc);
 
 	mock_nested = kzalloc(sizeof(*mock_nested), GFP_KERNEL);
 	if (!mock_nested)
 		return ERR_PTR(-ENOMEM);
-	mock_nested->parent = mock_parent;
 	mock_nested->domain.ops = &domain_nested_ops;
 	mock_nested->domain.type = IOMMU_DOMAIN_NESTED;
 	for (i = 0; i < MOCK_NESTED_DOMAIN_IOTLB_NUM; i++)
-		mock_nested->iotlb[i] = user_cfg->iotlb;
-	return &mock_nested->domain;
+		mock_nested->iotlb[i] = user_cfg.iotlb;
+	return mock_nested;
 }
 
 static struct iommu_domain *
-mock_domain_alloc_user(struct device *dev, u32 flags,
-		       struct iommu_domain *parent,
-		       const struct iommu_user_data *user_data)
+mock_domain_alloc_nested(struct iommu_domain *parent, u32 flags,
+			 const struct iommu_user_data *user_data)
 {
+	struct mock_iommu_domain_nested *mock_nested;
 	struct mock_iommu_domain *mock_parent;
-	struct iommu_hwpt_selftest user_cfg;
-	int rc;
-
-	/* must be mock_domain */
-	if (!parent) {
-		struct mock_dev *mdev = to_mock_dev(dev);
-		bool has_dirty_flag = flags & IOMMU_HWPT_ALLOC_DIRTY_TRACKING;
-		bool no_dirty_ops = mdev->flags & MOCK_FLAGS_DEVICE_NO_DIRTY;
-		struct iommu_domain *domain;
-
-		if (flags & (~(IOMMU_HWPT_ALLOC_NEST_PARENT |
-			       IOMMU_HWPT_ALLOC_DIRTY_TRACKING)))
-			return ERR_PTR(-EOPNOTSUPP);
-		if (user_data || (has_dirty_flag && no_dirty_ops))
-			return ERR_PTR(-EOPNOTSUPP);
-		domain = mock_domain_alloc_paging(dev);
-		if (!domain)
-			return ERR_PTR(-ENOMEM);
-		if (has_dirty_flag)
-			domain->dirty_ops = &dirty_ops;
-		return domain;
-	}
 
-	/* must be mock_domain_nested */
-	if (user_data->type != IOMMU_HWPT_DATA_SELFTEST || flags)
+	if (flags)
 		return ERR_PTR(-EOPNOTSUPP);
 	if (!parent || parent->ops != mock_ops.default_domain_ops)
 		return ERR_PTR(-EINVAL);
@@ -375,12 +359,39 @@ mock_domain_alloc_user(struct device *dev, u32 flags,
 	if (!mock_parent)
 		return ERR_PTR(-EINVAL);
 
-	rc = iommu_copy_struct_from_user(&user_cfg, user_data,
-					 IOMMU_HWPT_DATA_SELFTEST, iotlb);
-	if (rc)
-		return ERR_PTR(rc);
+	mock_nested = __mock_domain_alloc_nested(user_data);
+	if (IS_ERR(mock_nested))
+		return ERR_CAST(mock_nested);
+	mock_nested->parent = mock_parent;
+	return &mock_nested->domain;
+}
+
+static struct iommu_domain *
+mock_domain_alloc_user(struct device *dev, u32 flags,
+		       struct iommu_domain *parent,
+		       const struct iommu_user_data *user_data)
+{
+	bool has_dirty_flag = flags & IOMMU_HWPT_ALLOC_DIRTY_TRACKING;
+	const u32 PAGING_FLAGS = IOMMU_HWPT_ALLOC_DIRTY_TRACKING |
+				 IOMMU_HWPT_ALLOC_NEST_PARENT;
+	bool no_dirty_ops = to_mock_dev(dev)->flags &
+			    MOCK_FLAGS_DEVICE_NO_DIRTY;
+	struct iommu_domain *domain;
+
+	if (parent)
+		return mock_domain_alloc_nested(parent, flags, user_data);
 
-	return __mock_domain_alloc_nested(mock_parent, &user_cfg);
+	if (user_data)
+		return ERR_PTR(-EOPNOTSUPP);
+	if ((flags & ~PAGING_FLAGS) || (has_dirty_flag && no_dirty_ops))
+		return ERR_PTR(-EOPNOTSUPP);
+
+	domain = mock_domain_alloc_paging(dev);
+	if (!domain)
+		return ERR_PTR(-ENOMEM);
+	if (has_dirty_flag)
+		domain->dirty_ops = &dirty_ops;
+	return domain;
 }
 
 static void mock_domain_free(struct iommu_domain *domain)