[PATCH v3 07/11] iommufd/selftest: Add refcount to mock_iommu_device

[Nicolin Chen]

For an iommu_dev that can unplug (so far only this selftest does so), the
viommu->iommu_dev pointer has no guarantee of its life cycle after it is
copied from the idev->dev->iommu->iommu_dev.

Track the user count of the iommu_dev. Delay the exit routine if refcount
is unbalanced. The refcount inc/dec will be added in the following patch.

Signed-off-by: Nicolin Chen <nicol...@nvidia.com>
---
 drivers/iommu/iommufd/selftest.c | 33 ++++++++++++++++++++++++--------
 1 file changed, 25 insertions(+), 8 deletions(-)

diff --git a/drivers/iommu/iommufd/selftest.c b/drivers/iommu/iommufd/selftest.c
index f4be87b49447..a89a865617db 100644
--- a/drivers/iommu/iommufd/selftest.c
+++ b/drivers/iommu/iommufd/selftest.c
@@ -508,14 +508,17 @@ static bool mock_domain_capable(struct device *dev, enum 
iommu_cap cap)
 
 static struct iopf_queue *mock_iommu_iopf_queue;
 
-static struct iommu_device mock_iommu_device = {
-};
+static struct mock_iommu_device {
+       struct iommu_device iommu_dev;
+       wait_queue_head_t wait;
+       refcount_t users;
+} mock_iommu;
 
 static struct iommu_device *mock_probe_device(struct device *dev)
 {
        if (dev->bus != &iommufd_mock_bus_type.bus)
                return ERR_PTR(-ENODEV);
-       return &mock_iommu_device;
+       return &mock_iommu.iommu_dev;
 }
 
 static void mock_domain_page_response(struct device *dev, struct iopf_fault 
*evt,
@@ -1537,24 +1540,27 @@ int __init iommufd_test_init(void)
        if (rc)
                goto err_platform;
 
-       rc = iommu_device_sysfs_add(&mock_iommu_device,
+       rc = iommu_device_sysfs_add(&mock_iommu.iommu_dev,
                                    &selftest_iommu_dev->dev, NULL, "%s",
                                    dev_name(&selftest_iommu_dev->dev));
        if (rc)
                goto err_bus;
 
-       rc = iommu_device_register_bus(&mock_iommu_device, &mock_ops,
+       rc = iommu_device_register_bus(&mock_iommu.iommu_dev, &mock_ops,
                                  &iommufd_mock_bus_type.bus,
                                  &iommufd_mock_bus_type.nb);
        if (rc)
                goto err_sysfs;
 
+       refcount_set(&mock_iommu.users, 1);
+       init_waitqueue_head(&mock_iommu.wait);
+
        mock_iommu_iopf_queue = iopf_queue_alloc("mock-iopfq");
 
        return 0;
 
 err_sysfs:
-       iommu_device_sysfs_remove(&mock_iommu_device);
+       iommu_device_sysfs_remove(&mock_iommu.iommu_dev);
 err_bus:
        bus_unregister(&iommufd_mock_bus_type.bus);
 err_platform:
@@ -1564,6 +1570,16 @@ int __init iommufd_test_init(void)
        return rc;
 }
 
+static void iommufd_test_wait_for_users(void)
+{
+       if (refcount_dec_and_test(&mock_iommu.users))
+               return;
+       /* Time out waiting for iommu device user count to become 0 */
+       WARN_ON(!wait_event_timeout(mock_iommu.wait,
+                                   refcount_read(&mock_iommu.users) == 0,
+                                   msecs_to_jiffies(10000)));
+}
+
 void iommufd_test_exit(void)
 {
        if (mock_iommu_iopf_queue) {
@@ -1571,8 +1587,9 @@ void iommufd_test_exit(void)
                mock_iommu_iopf_queue = NULL;
        }
 
-       iommu_device_sysfs_remove(&mock_iommu_device);
-       iommu_device_unregister_bus(&mock_iommu_device,
+       iommufd_test_wait_for_users();
+       iommu_device_sysfs_remove(&mock_iommu.iommu_dev);
+       iommu_device_unregister_bus(&mock_iommu.iommu_dev,
                                    &iommufd_mock_bus_type.bus,
                                    &iommufd_mock_bus_type.nb);
        bus_unregister(&iommufd_mock_bus_type.bus);
-- 
2.43.0