[PATCH v4 1/1] vfio/type1: Add vfio_group_iommu_domain()

[Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>]

Add the API for getting the domain from a vfio group. This could be used
by the physical device drivers which rely on the vfio/mdev framework for
mediated device user level access. The typical use case like below:

	unsigned int pasid;
	struct vfio_group *vfio_group;
	struct iommu_domain *iommu_domain;
	struct device *dev = mdev_dev(mdev);
	struct device *iommu_device = mdev_get_iommu_device(dev);

	if (!iommu_device ||
	    !iommu_dev_feature_enabled(iommu_device, IOMMU_DEV_FEAT_AUX))
		return -EINVAL;

	vfio_group = vfio_group_get_external_user_from_dev(dev);
	if (IS_ERR_OR_NULL(vfio_group))
		return -EFAULT;

	iommu_domain = vfio_group_iommu_domain(vfio_group);
	if (IS_ERR_OR_NULL(iommu_domain)) {
		vfio_group_put_external_user(vfio_group);
		return -EFAULT;
	}

	pasid = iommu_aux_get_pasid(iommu_domain, iommu_device);
	if (pasid < 0) {
		vfio_group_put_external_user(vfio_group);
		return -EFAULT;
	}

	/* Program device context with pasid value. */
	...

Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
 drivers/vfio/vfio.c             | 18 ++++++++++++++++++
 drivers/vfio/vfio_iommu_type1.c | 24 ++++++++++++++++++++++++
 include/linux/vfio.h            |  4 ++++
 3 files changed, 46 insertions(+)

Change log:
 - v3: https://lore.kernel.org/linux-iommu/20201201012328.2465735-1-baolu.lu@xxxxxxxxxxxxxxx/
 - Changed according to comments @ https://lore.kernel.org/linux-iommu/20201202144834.1dd0983e@xxxxxxxxx/
   - Rename group_domain to group_iommu_domain;
   - Remove an unnecessary else branch.

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 2151bc7f87ab..4ad8a35667a7 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -2331,6 +2331,24 @@ int vfio_unregister_notifier(struct device *dev, enum vfio_notify_type type,
 }
 EXPORT_SYMBOL(vfio_unregister_notifier);
 
+struct iommu_domain *vfio_group_iommu_domain(struct vfio_group *group)
+{
+	struct vfio_container *container;
+	struct vfio_iommu_driver *driver;
+
+	if (!group)
+		return ERR_PTR(-EINVAL);
+
+	container = group->container;
+	driver = container->iommu_driver;
+	if (likely(driver && driver->ops->group_iommu_domain))
+		return driver->ops->group_iommu_domain(container->iommu_data,
+						       group->iommu_group);
+
+	return ERR_PTR(-ENOTTY);
+}
+EXPORT_SYMBOL_GPL(vfio_group_iommu_domain);
+
 /**
  * Module/class support
  */
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 67e827638995..0b4dedaa9128 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -2980,6 +2980,29 @@ static int vfio_iommu_type1_dma_rw(void *iommu_data, dma_addr_t user_iova,
 	return ret;
 }
 
+static struct iommu_domain *
+vfio_iommu_type1_group_iommu_domain(void *iommu_data,
+				    struct iommu_group *iommu_group)
+{
+	struct iommu_domain *domain = ERR_PTR(-ENODEV);
+	struct vfio_iommu *iommu = iommu_data;
+	struct vfio_domain *d;
+
+	if (!iommu || !iommu_group)
+		return ERR_PTR(-EINVAL);
+
+	mutex_lock(&iommu->lock);
+	list_for_each_entry(d, &iommu->domain_list, next) {
+		if (find_iommu_group(d, iommu_group)) {
+			domain = d->domain;
+			break;
+		}
+	}
+	mutex_unlock(&iommu->lock);
+
+	return domain;
+}
+
 static const struct vfio_iommu_driver_ops vfio_iommu_driver_ops_type1 = {
 	.name			= "vfio-iommu-type1",
 	.owner			= THIS_MODULE,
@@ -2993,6 +3016,7 @@ static const struct vfio_iommu_driver_ops vfio_iommu_driver_ops_type1 = {
 	.register_notifier	= vfio_iommu_type1_register_notifier,
 	.unregister_notifier	= vfio_iommu_type1_unregister_notifier,
 	.dma_rw			= vfio_iommu_type1_dma_rw,
+	.group_iommu_domain	= vfio_iommu_type1_group_iommu_domain,
 };
 
 static int __init vfio_iommu_type1_init(void)
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 38d3c6a8dc7e..f45940b38a02 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -90,6 +90,8 @@ struct vfio_iommu_driver_ops {
 					       struct notifier_block *nb);
 	int		(*dma_rw)(void *iommu_data, dma_addr_t user_iova,
 				  void *data, size_t count, bool write);
+	struct iommu_domain *(*group_iommu_domain)(void *iommu_data,
+						   struct iommu_group *group);
 };
 
 extern int vfio_register_iommu_driver(const struct vfio_iommu_driver_ops *ops);
@@ -126,6 +128,8 @@ extern int vfio_group_unpin_pages(struct vfio_group *group,
 extern int vfio_dma_rw(struct vfio_group *group, dma_addr_t user_iova,
 		       void *data, size_t len, bool write);
 
+extern struct iommu_domain *vfio_group_iommu_domain(struct vfio_group *group);
+
 /* each type has independent events */
 enum vfio_notify_type {
 	VFIO_IOMMU_NOTIFY = 0,
-- 
2.25.1