[PATCH 5/7] vfio: Create interface for vfio bus drivers to register

[Alex Williamson]

Generally we don't know about vfio bus drivers until a device is
added to the vfio-core with vfio_add_group_dev(), this optional
registration with vfio_register_bus_driver() allows vfio-core to
track known drivers.  Our current use for this information is to
know whether a driver is vfio compatible during a bind operation.
For devices on buses with driver_override support, we can use this
linkage to block non-vfio drivers from binding to devices where
the iommu group state would trigger a BUG to avoid host/user
integrity issues.

Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
---
 drivers/vfio/vfio.c  |   55 ++++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/vfio.h |    3 +++
 2 files changed, 58 insertions(+)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index e6117de60f87..a25ee4930200 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -43,6 +43,8 @@
 	struct class			*class;
 	struct list_head		iommu_drivers_list;
 	struct mutex			iommu_drivers_lock;
+	struct list_head		bus_drivers_list;
+	struct mutex			bus_drivers_lock;
 	struct list_head		group_list;
 	struct idr			group_idr;
 	struct mutex			group_lock;
@@ -51,6 +53,11 @@
 	wait_queue_head_t		release_q;
 } vfio;
 
+struct vfio_bus_driver {
+	struct device_driver		*drv;
+	struct list_head		vfio_next;
+};
+
 struct vfio_iommu_driver {
 	const struct vfio_iommu_driver_ops	*ops;
 	struct list_head			vfio_next;
@@ -2243,6 +2250,52 @@ int vfio_unregister_notifier(struct device *dev, enum vfio_notify_type type,
 }
 EXPORT_SYMBOL(vfio_unregister_notifier);
 
+int vfio_register_bus_driver(struct device_driver *drv)
+{
+	struct vfio_bus_driver *driver, *tmp;
+
+	driver = kzalloc(sizeof(*driver), GFP_KERNEL);
+	if (!driver)
+		return -ENOMEM;
+
+	driver->drv = drv;
+
+	mutex_lock(&vfio.bus_drivers_lock);
+
+	/* Check for duplicates */
+	list_for_each_entry(tmp, &vfio.bus_drivers_list, vfio_next) {
+		if (tmp->drv == drv) {
+			mutex_unlock(&vfio.bus_drivers_lock);
+			kfree(driver);
+			return -EINVAL;
+		}
+	}
+
+	list_add(&driver->vfio_next, &vfio.bus_drivers_list);
+
+	mutex_unlock(&vfio.bus_drivers_lock);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(vfio_register_bus_driver);
+
+void vfio_unregister_bus_driver(struct device_driver *drv)
+{
+	struct vfio_bus_driver *driver;
+
+	mutex_lock(&vfio.bus_drivers_lock);
+	list_for_each_entry(driver, &vfio.bus_drivers_list, vfio_next) {
+		if (driver->drv == drv) {
+			list_del(&driver->vfio_next);
+			mutex_unlock(&vfio.bus_drivers_lock);
+			kfree(driver);
+			return;
+		}
+	}
+	mutex_unlock(&vfio.bus_drivers_lock);
+}
+EXPORT_SYMBOL_GPL(vfio_unregister_bus_driver);
+
 /**
  * Module/class support
  */
@@ -2266,8 +2319,10 @@ static int __init vfio_init(void)
 	idr_init(&vfio.group_idr);
 	mutex_init(&vfio.group_lock);
 	mutex_init(&vfio.iommu_drivers_lock);
+	mutex_init(&vfio.bus_drivers_lock);
 	INIT_LIST_HEAD(&vfio.group_list);
 	INIT_LIST_HEAD(&vfio.iommu_drivers_list);
+	INIT_LIST_HEAD(&vfio.bus_drivers_list);
 	init_waitqueue_head(&vfio.release_q);
 
 	ret = misc_register(&vfio_dev);
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 9b34d0af5d27..dab0f8105e4a 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -92,6 +92,9 @@ struct vfio_iommu_driver_ops {
 extern void vfio_unregister_iommu_driver(
 				const struct vfio_iommu_driver_ops *ops);
 
+extern int vfio_register_bus_driver(struct device_driver *drv);
+extern void vfio_unregister_bus_driver(struct device_driver *drv);
+
 /*
  * External user API
  */