[PATCH v3 1/9] s390: vfio_ap: link the vfio_ap devices to the vfio_ap bus subsystem

[Pierre Morel <pmorel@linux.ibm.com>]

Libudev relies on having a subsystem link for non-root devices. To
avoid libudev (and potentially other userspace tools) choking on the
matrix device let us introduce a vfio_ap bus and with that the vfio_ap
bus subsytem, and make the matrix device reside within it.

We restrict the number of allowed devices to a single one.

Doing this we need to suppress the forced link from the matrix device to
the vfio_ap driver and we suppress the device_type we do not need
anymore.

Since the associated matrix driver is not the vfio_ap driver any more,
we have to change the search for the devices on the vfio_ap driver in
the function vfio_ap_verify_queue_reserved.

Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_drv.c     | 63 +++++++++++++++++++++++++++++++----
 drivers/s390/crypto/vfio_ap_ops.c     |  4 +--
 drivers/s390/crypto/vfio_ap_private.h |  1 +
 3 files changed, 60 insertions(+), 8 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
index 31c6c84..1fd5fe6 100644
--- a/drivers/s390/crypto/vfio_ap_drv.c
+++ b/drivers/s390/crypto/vfio_ap_drv.c
@@ -24,8 +24,9 @@ MODULE_LICENSE("GPL v2");
 
 static struct ap_driver vfio_ap_drv;
 
-static struct device_type vfio_ap_dev_type = {
-	.name = VFIO_AP_DEV_TYPE_NAME,
+struct matrix_driver {
+	struct device_driver drv;
+	int device_count;
 };
 
 struct ap_matrix_dev *matrix_dev;
@@ -62,6 +63,41 @@ static void vfio_ap_matrix_dev_release(struct device *dev)
 	kfree(matrix_dev);
 }
 
+static int matrix_bus_match(struct device *dev, struct device_driver *drv)
+{
+	return 1;
+}
+
+static struct bus_type matrix_bus = {
+	.name = "vfio_ap",
+	.match = &matrix_bus_match,
+};
+
+static int matrix_probe(struct device *dev);
+static int matrix_remove(struct device *dev);
+static struct matrix_driver matrix_driver = {
+	.drv = {
+		.name = "vfio_ap",
+		.bus = &matrix_bus,
+		.probe = matrix_probe,
+		.remove = matrix_remove,
+	},
+};
+
+static int matrix_probe(struct device *dev)
+{
+	if (matrix_driver.device_count)
+		return -EEXIST;
+	matrix_driver.device_count++;
+	return 0;
+}
+
+static int matrix_remove(struct device *dev)
+{
+	matrix_driver.device_count--;
+	return 0;
+}
+
 static int vfio_ap_matrix_dev_create(void)
 {
 	int ret;
@@ -71,6 +107,10 @@ static int vfio_ap_matrix_dev_create(void)
 	if (IS_ERR(root_device))
 		return PTR_ERR(root_device);
 
+	ret = bus_register(&matrix_bus);
+	if (ret)
+		goto bus_register_err;
+
 	matrix_dev = kzalloc(sizeof(*matrix_dev), GFP_KERNEL);
 	if (!matrix_dev) {
 		ret = -ENOMEM;
@@ -87,30 +127,41 @@ static int vfio_ap_matrix_dev_create(void)
 	mutex_init(&matrix_dev->lock);
 	INIT_LIST_HEAD(&matrix_dev->mdev_list);
 
-	matrix_dev->device.type = &vfio_ap_dev_type;
 	dev_set_name(&matrix_dev->device, "%s", VFIO_AP_DEV_NAME);
 	matrix_dev->device.parent = root_device;
+	matrix_dev->device.bus = &matrix_bus;
 	matrix_dev->device.release = vfio_ap_matrix_dev_release;
-	matrix_dev->device.driver = &vfio_ap_drv.driver;
+	matrix_dev->vfio_ap_drv = &vfio_ap_drv;
 
 	ret = device_register(&matrix_dev->device);
 	if (ret)
 		goto matrix_reg_err;
 
+	ret = driver_register(&matrix_driver.drv);
+	if (ret)
+		goto matrix_drv_err;
+
 	return 0;
 
+matrix_drv_err:
+	device_unregister(&matrix_dev->device);
 matrix_reg_err:
 	put_device(&matrix_dev->device);
 matrix_alloc_err:
+	bus_unregister(&matrix_bus);
+bus_register_err:
 	root_device_unregister(root_device);
-
 	return ret;
 }
 
 static void vfio_ap_matrix_dev_destroy(void)
 {
+	struct device *root_device = matrix_dev->device.parent;
+
+	driver_unregister(&matrix_driver.drv);
 	device_unregister(&matrix_dev->device);
-	root_device_unregister(matrix_dev->device.parent);
+	bus_unregister(&matrix_bus);
+	root_device_unregister(root_device);
 }
 
 static int __init vfio_ap_init(void)
diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index 272ef42..900b9cf 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -198,8 +198,8 @@ static int vfio_ap_verify_queue_reserved(unsigned long *apid,
 	qres.apqi = apqi;
 	qres.reserved = false;
 
-	ret = driver_for_each_device(matrix_dev->device.driver, NULL, &qres,
-				     vfio_ap_has_queue);
+	ret = driver_for_each_device(&matrix_dev->vfio_ap_drv->driver, NULL,
+				     &qres, vfio_ap_has_queue);
 	if (ret)
 		return ret;
 
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index 5675492..76b7f98 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -40,6 +40,7 @@ struct ap_matrix_dev {
 	struct ap_config_info info;
 	struct list_head mdev_list;
 	struct mutex lock;
+	struct ap_driver  *vfio_ap_drv;
 };
 
 extern struct ap_matrix_dev *matrix_dev;
-- 
2.7.4