Implement the viommu alloc/free functions to increase/reduce refcount of
its dependent mock iommu device. User space can verify this loop via the
IOMMU_VIOMMU_TYPE_SELFTEST.

Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
---
 drivers/iommu/iommufd/iommufd_test.h |  2 ++
 drivers/iommu/iommufd/selftest.c     | 41 ++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/drivers/iommu/iommufd/iommufd_test.h b/drivers/iommu/iommufd/iommufd_test.h
index f4bc23a92f9a..edced4ac7cd3 100644
--- a/drivers/iommu/iommufd/iommufd_test.h
+++ b/drivers/iommu/iommufd/iommufd_test.h
@@ -180,4 +180,6 @@ struct iommu_hwpt_invalidate_selftest {
 	__u32 iotlb_id;
 };
 
+#define IOMMU_VIOMMU_TYPE_SELFTEST 0xdeadbeef
+
 #endif
diff --git a/drivers/iommu/iommufd/selftest.c b/drivers/iommu/iommufd/selftest.c
index dbd2a78c1074..04dd95fe24ca 100644
--- a/drivers/iommu/iommufd/selftest.c
+++ b/drivers/iommu/iommufd/selftest.c
@@ -132,6 +132,10 @@ struct mock_iommu_domain_nested {
 	u32 iotlb[MOCK_NESTED_DOMAIN_IOTLB_NUM];
 };
 
+struct mock_viommu {
+	struct iommufd_viommu core;
+};
+
 enum selftest_obj_type {
 	TYPE_IDEV,
 };
@@ -543,6 +547,42 @@ static int mock_dev_disable_feat(struct device *dev, enum iommu_dev_features fea
 	return 0;
 }
 
+static void mock_viommu_free(struct iommufd_viommu *viommu)
+{
+	struct mock_iommu_device *mock_iommu = container_of(
+		viommu->iommu_dev, struct mock_iommu_device, iommu_dev);
+
+	if (refcount_dec_and_test(&mock_iommu->users))
+		complete(&mock_iommu->complete);
+
+	/* iommufd core frees mock_viommu and viommu */
+}
+
+static struct iommufd_viommu_ops mock_viommu_ops = {
+	.free = mock_viommu_free,
+};
+
+static struct iommufd_viommu *mock_viommu_alloc(struct device *dev,
+						struct iommu_domain *domain,
+						struct iommufd_ctx *ictx,
+						unsigned int viommu_type)
+{
+	struct mock_iommu_device *mock_iommu =
+		iommu_get_iommu_dev(dev, struct mock_iommu_device, iommu_dev);
+	struct mock_viommu *mock_viommu;
+
+	if (viommu_type != IOMMU_VIOMMU_TYPE_SELFTEST)
+		return ERR_PTR(-EOPNOTSUPP);
+
+	mock_viommu =
+		iommufd_viommu_alloc(ictx, mock_viommu, core, &mock_viommu_ops);
+	if (IS_ERR(mock_viommu))
+		return ERR_CAST(mock_viommu);
+
+	refcount_inc(&mock_iommu->users);
+	return &mock_viommu->core;
+}
+
 static const struct iommu_ops mock_ops = {
 	/*
 	 * IOMMU_DOMAIN_BLOCKED cannot be returned from def_domain_type()
@@ -562,6 +602,7 @@ static const struct iommu_ops mock_ops = {
 	.dev_enable_feat = mock_dev_enable_feat,
 	.dev_disable_feat = mock_dev_disable_feat,
 	.user_pasid_table = true,
+	.viommu_alloc = mock_viommu_alloc,
 	.default_domain_ops =
 		&(struct iommu_domain_ops){
 			.free = mock_domain_free,
-- 
2.43.0