iommu: Add iommu_init/deinit_device() paired functions

Move the driver init and destruction code into two logically paired
functions.

There is a subtle ordering dependency in how the group's domains are
freed, the current code does the kobject_put() on the group which will
hopefully trigger the free of the domains before the module_put() that
protects the domain->ops.

Reorganize this to be explicit and documented. The domains are cleaned up
by iommu_deinit_device() if it is the last device to be deinit'd from the
group.  This must be done in a specific order - after
ops->release_device() and before the module_put(). Make it very clear and
obvious by putting the order directly in one function.

Leave WARN_ON's in case the refcounting gets messed up somehow.

This also moves the module_put() and dev_iommu_free() under the
group->mutex to keep the code simple.

Building paired functions like this helps ensure that error cleanup flows
in __iommu_probe_device() are correct because they share the same code
that handles the normal flow. These details become relavent as following
patches add more error unwind into __iommu_probe_device(), and ultimately
a following series adds fine-grained locking to __iommu_probe_device().
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/5-v3-328044aa278c+45e49-iommu_probe_jgg@nvidia.comSigned-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/iommu.c

@@ -332,10 +332,99 @@ static u32 dev_iommu_get_max_pasids(struct device *dev)
 	return min_t(u32, max_pasids, dev->iommu->iommu_dev->max_pasids);
 }
 
+/*
+ * Init the dev->iommu and dev->iommu_group in the struct device and get the
+ * driver probed
+ */
+static int iommu_init_device(struct device *dev, const struct iommu_ops *ops)
+{
+	struct iommu_device *iommu_dev;
+	struct iommu_group *group;
+	int ret;
+
+	if (!dev_iommu_get(dev))
+		return -ENOMEM;
+
+	if (!try_module_get(ops->owner)) {
+		ret = -EINVAL;
+		goto err_free;
+	}
+
+	iommu_dev = ops->probe_device(dev);
+	if (IS_ERR(iommu_dev)) {
+		ret = PTR_ERR(iommu_dev);
+		goto err_module_put;
+	}
+
+	group = ops->device_group(dev);
+	if (WARN_ON_ONCE(group == NULL))
+		group = ERR_PTR(-EINVAL);
+	if (IS_ERR(group)) {
+		ret = PTR_ERR(group);
+		goto err_release;
+	}
+	dev->iommu_group = group;
+
+	dev->iommu->iommu_dev = iommu_dev;
+	dev->iommu->max_pasids = dev_iommu_get_max_pasids(dev);
+	if (ops->is_attach_deferred)
+		dev->iommu->attach_deferred = ops->is_attach_deferred(dev);
+	return 0;
+
+err_release:
+	if (ops->release_device)
+		ops->release_device(dev);
+err_module_put:
+	module_put(ops->owner);
+err_free:
+	dev_iommu_free(dev);
+	return ret;
+}
+
+static void iommu_deinit_device(struct device *dev)
+{
+	struct iommu_group *group = dev->iommu_group;
+	const struct iommu_ops *ops = dev_iommu_ops(dev);
+
+	lockdep_assert_held(&group->mutex);
+
+	/*
+	 * release_device() must stop using any attached domain on the device.
+	 * If there are still other devices in the group they are not effected
+	 * by this callback.
+	 *
+	 * The IOMMU driver must set the device to either an identity or
+	 * blocking translation and stop using any domain pointer, as it is
+	 * going to be freed.
+	 */
+	if (ops->release_device)
+		ops->release_device(dev);
+
+	/*
+	 * If this is the last driver to use the group then we must free the
+	 * domains before we do the module_put().
+	 */
+	if (list_empty(&group->devices)) {
+		if (group->default_domain) {
+			iommu_domain_free(group->default_domain);
+			group->default_domain = NULL;
+		}
+		if (group->blocking_domain) {
+			iommu_domain_free(group->blocking_domain);
+			group->blocking_domain = NULL;
+		}
+		group->domain = NULL;
+	}
+
+	/* Caller must put iommu_group */
+	dev->iommu_group = NULL;
+	module_put(ops->owner);
+	dev_iommu_free(dev);
+}
+
 static int __iommu_probe_device(struct device *dev, struct list_head *group_list)
 {
 	const struct iommu_ops *ops = dev->bus->iommu_ops;
-	struct iommu_device *iommu_dev;
 	struct iommu_group *group;
 	static DEFINE_MUTEX(iommu_probe_device_lock);
 	int ret;
@@ -357,62 +446,30 @@ static int __iommu_probe_device(struct device *dev, struct list_head *group_list
 		goto out_unlock;
 	}
 
-	if (!dev_iommu_get(dev)) {
-		ret = -ENOMEM;
+	ret = iommu_init_device(dev, ops);
+	if (ret)
 		goto out_unlock;
-	}
-
-	if (!try_module_get(ops->owner)) {
-		ret = -EINVAL;
-		goto err_free;
-	}
-
-	iommu_dev = ops->probe_device(dev);
-	if (IS_ERR(iommu_dev)) {
-		ret = PTR_ERR(iommu_dev);
-		goto out_module_put;
-	}
-
-	dev->iommu->iommu_dev = iommu_dev;
-	dev->iommu->max_pasids = dev_iommu_get_max_pasids(dev);
-	if (ops->is_attach_deferred)
-		dev->iommu->attach_deferred = ops->is_attach_deferred(dev);
-
-	group = ops->device_group(dev);
-	if (WARN_ON_ONCE(group == NULL))
-		group = ERR_PTR(-EINVAL);
-	if (IS_ERR(group)) {
-		ret = PTR_ERR(group);
-		goto out_release;
-	}
 
+	group = dev->iommu_group;
 	ret = iommu_group_add_device(group, dev);
+	mutex_lock(&group->mutex);
 	if (ret)
 		goto err_put_group;
 
-	mutex_lock(&group->mutex);
 	if (group_list && !group->default_domain && list_empty(&group->entry))
 		list_add_tail(&group->entry, group_list);
 	mutex_unlock(&group->mutex);
 	iommu_group_put(group);
 
 	mutex_unlock(&iommu_probe_device_lock);
-	iommu_device_link(iommu_dev, dev);
+	iommu_device_link(dev->iommu->iommu_dev, dev);
 
 	return 0;
 
 err_put_group:
+	iommu_deinit_device(dev);
+	mutex_unlock(&group->mutex);
 	iommu_group_put(group);
-out_release:
-	if (ops->release_device)
-		ops->release_device(dev);
-
-out_module_put:
-	module_put(ops->owner);
-
-err_free:
-	dev_iommu_free(dev);
-
 out_unlock:
 	mutex_unlock(&iommu_probe_device_lock);
 
@@ -491,63 +548,45 @@ static void __iommu_group_free_device(struct iommu_group *group,
 
 	kfree(grp_dev->name);
 	kfree(grp_dev);
-	dev->iommu_group = NULL;
 }
 
-/*
- * Remove the iommu_group from the struct device. The attached group must be put
- * by the caller after releaseing the group->mutex.
- */
+/* Remove the iommu_group from the struct device. */
 static void __iommu_group_remove_device(struct device *dev)
 {
 	struct iommu_group *group = dev->iommu_group;
 	struct group_device *device;
 
-	lockdep_assert_held(&group->mutex);
+	mutex_lock(&group->mutex);
 	for_each_group_device(group, device) {
 		if (device->dev != dev)
 			continue;
 
 		list_del(&device->list);
 		__iommu_group_free_device(group, device);
-		/* Caller must put iommu_group */
-		return;
+		if (dev->iommu && dev->iommu->iommu_dev)
+			iommu_deinit_device(dev);
+		else
+			dev->iommu_group = NULL;
+		goto out;
 	}
 	WARN(true, "Corrupted iommu_group device_list");
+out:
+	mutex_unlock(&group->mutex);
+
+	/* Pairs with the get in iommu_group_add_device() */
+	iommu_group_put(group);
 }
 
 static void iommu_release_device(struct device *dev)
 {
 	struct iommu_group *group = dev->iommu_group;
-	const struct iommu_ops *ops;
 
 	if (!dev->iommu || !group)
 		return;
 
 	iommu_device_unlink(dev->iommu->iommu_dev, dev);
 
-	mutex_lock(&group->mutex);
 	__iommu_group_remove_device(dev);
-
-	/*
-	 * release_device() must stop using any attached domain on the device.
-	 * If there are still other devices in the group they are not effected
-	 * by this callback.
-	 *
-	 * The IOMMU driver must set the device to either an identity or
-	 * blocking translation and stop using any domain pointer, as it is
-	 * going to be freed.
-	 */
-	ops = dev_iommu_ops(dev);
-	if (ops->release_device)
-		ops->release_device(dev);
-	mutex_unlock(&group->mutex);
-
-	/* Pairs with the get in iommu_group_add_device() */
-	iommu_group_put(group);
-
-	module_put(ops->owner);
-	dev_iommu_free(dev);
 }
 
 static int __init iommu_set_def_domain_type(char *str)
@@ -808,10 +847,9 @@ static void iommu_group_release(struct kobject *kobj)
 
 	ida_free(&iommu_group_ida, group->id);
 
-	if (group->default_domain)
-		iommu_domain_free(group->default_domain);
-	if (group->blocking_domain)
-		iommu_domain_free(group->blocking_domain);
+	/* Domains are free'd by iommu_deinit_device() */
+	WARN_ON(group->default_domain);
+	WARN_ON(group->blocking_domain);
 
 	kfree(group->name);
 	kfree(group);
@@ -1109,12 +1147,7 @@ void iommu_group_remove_device(struct device *dev)
 
 	dev_info(dev, "Removing from iommu group %d\n", group->id);
 
-	mutex_lock(&group->mutex);
 	__iommu_group_remove_device(dev);
-	mutex_unlock(&group->mutex);
-
-	/* Pairs with the get in iommu_group_add_device() */
-	iommu_group_put(group);
 }
 EXPORT_SYMBOL_GPL(iommu_group_remove_device);