[PATCH V13 2/6] mdev: split out VFIO bus specific parent ops

[Jason Wang <jasowang@redhat.com>]

The only thing left for generalizing mdev is the VFIO specific parent
ops. This is basically the open/release/read/write/ioctl/mmap.

To support this, mdev core is extend to support a specific size
of structure during create, this will allow to compose mdev structure
into mdev vfio structure and place the VFIO specific callbacks there
like:

struct mdev_vfio {
       struct mdev_device mdev;
       const struct mdev_vfio_ops *ops;
};

Helpers for setting and getting the ops were introduced to support
mdev vfio device to set ops and vfio mdev driver to use the ops.

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 .../driver-api/vfio-mediated-device.rst       | 34 +++++++++------
 drivers/gpu/drm/i915/gvt/kvmgt.c              | 16 ++++---
 drivers/s390/cio/vfio_ccw_ops.c               | 17 +++++---
 drivers/s390/crypto/vfio_ap_ops.c             | 13 ++++--
 drivers/vfio/mdev/mdev_core.c                 |  5 ++-
 drivers/vfio/mdev/mdev_private.h              |  5 +++
 drivers/vfio/mdev/mdev_vfio.c                 | 30 ++++++++++++-
 drivers/vfio/mdev/vfio_mdev.c                 | 38 ++++++++--------
 include/linux/mdev.h                          | 37 ----------------
 include/linux/mdev_vfio.h                     | 43 +++++++++++++++++++
 samples/vfio-mdev/mbochs.c                    | 18 +++++---
 samples/vfio-mdev/mdpy.c                      | 19 +++++---
 samples/vfio-mdev/mtty.c                      | 16 ++++---
 13 files changed, 189 insertions(+), 102 deletions(-)

diff --git a/Documentation/driver-api/vfio-mediated-device.rst b/Documentation/driver-api/vfio-mediated-device.rst
index 1887d27a565e..9045584e4ea3 100644
--- a/Documentation/driver-api/vfio-mediated-device.rst
+++ b/Documentation/driver-api/vfio-mediated-device.rst
@@ -153,26 +153,36 @@ callbacks per mdev parent device, per mdev type, or any other categorization.
 Vendor drivers are expected to be fully asynchronous in this respect or
 provide their own internal resource protection.)
 
-The callbacks in the mdev_parent_ops structure are as follows:
+A driver should use the mdev_parent_ops structure in the function call
+to register itself with the mdev core driver::
 
-* open: open callback of mediated device
-* close: close callback of mediated device
-* ioctl: ioctl callback of mediated device
+	extern int mdev_vfio_register_device(struct device *dev,
+                                             const struct mdev_parent_ops *ops);
+
+However, the mdev_parent_ops structure is not required in the function call
+that a driver should use to unregister itself with the mdev core driver::
+
+	extern void mdev_vfio_unregister_device(struct device *dev);
+
+The VFIO specific callbacks is abstracted in mdev_vfio_ops structure
+are as follows:
+
+* open: open callback of VFIO mediated device
+* close: close callback of VFIO mediated device
+* ioctl: ioctl callback of VFIO mediated device
 * read : read emulation callback
 * write: write emulation callback
 * mmap: mmap emulation callback
 
-A driver should use the mdev_parent_ops structure and bus type in the
-function call to register itself with the mdev core driver::
+During the creation of VFIO mediated device, mdev_vfio_ops need to be
+specified::
 
-	extern int  mdev_register_device(struct device *dev,
-	                                 const struct mdev_parent_ops *ops,
-                                         struct bus_type *bus);
+	 void mdev_vfio_set_ops(struct mdev_device *mdev,
+                                const struct mdev_vfio_ops *ops);
 
-However, the mdev_parent_ops structure is not required in the function call
-that a driver should use to unregister itself with the mdev core driver::
+Those callbacks could be fetched by drivers through::
 
-	extern void mdev_unregister_device(struct device *dev);
+	 const struct mdev_vfio_ops *mdev_vfio_get_ops(struct mdev_device *mdev);
 
 
 Mediated Device Management Interface Through sysfs
diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
index afdb3de5ce2f..e72c36174035 100644
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -643,6 +643,8 @@ static void kvmgt_put_vfio_device(void *vgpu)
 	vfio_device_put(((struct intel_vgpu *)vgpu)->vdev.vfio_device);
 }
 
+static const struct mdev_vfio_ops intel_mdev_vfio_ops;
+
 static int intel_vgpu_create(struct kobject *kobj, struct mdev_device *mdev)
 {
 	struct intel_vgpu *vgpu = NULL;
@@ -678,6 +680,7 @@ static int intel_vgpu_create(struct kobject *kobj, struct mdev_device *mdev)
 		     dev_name(mdev_dev(mdev)));
 	ret = 0;
 
+	mdev_vfio_set_ops(mdev, &intel_mdev_vfio_ops);
 out:
 	return ret;
 }
@@ -1581,20 +1584,21 @@ static const struct attribute_group *intel_vgpu_groups[] = {
 	NULL,
 };
 
-static struct mdev_parent_ops intel_vgpu_ops = {
-	.mdev_attr_groups       = intel_vgpu_groups,
-	.create			= intel_vgpu_create,
-	.remove			= intel_vgpu_remove,
-
+static const struct mdev_vfio_ops intel_mdev_vfio_ops = {
 	.open			= intel_vgpu_open,
 	.release		= intel_vgpu_release,
-
 	.read			= intel_vgpu_read,
 	.write			= intel_vgpu_write,
 	.mmap			= intel_vgpu_mmap,
 	.ioctl			= intel_vgpu_ioctl,
 };
 
+static struct mdev_parent_ops intel_vgpu_ops = {
+	.mdev_attr_groups       = intel_vgpu_groups,
+	.create			= intel_vgpu_create,
+	.remove			= intel_vgpu_remove,
+};
+
 static int kvmgt_host_init(struct device *dev, void *gvt, const void *ops)
 {
 	struct attribute **kvm_type_attrs;
diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
index 791b8b0eb027..811f0a3b1903 100644
--- a/drivers/s390/cio/vfio_ccw_ops.c
+++ b/drivers/s390/cio/vfio_ccw_ops.c
@@ -110,6 +110,8 @@ static struct attribute_group *mdev_type_groups[] = {
 	NULL,
 };
 
+static const struct mdev_vfio_ops vfio_ccw_mdev_vfio_ops;
+
 static int vfio_ccw_mdev_create(struct kobject *kobj, struct mdev_device *mdev)
 {
 	struct vfio_ccw_private *private =
@@ -129,6 +131,8 @@ static int vfio_ccw_mdev_create(struct kobject *kobj, struct mdev_device *mdev)
 			   private->sch->schid.ssid,
 			   private->sch->schid.sch_no);
 
+	mdev_vfio_set_ops(mdev, &vfio_ccw_mdev_vfio_ops);
+
 	return 0;
 }
 
@@ -574,16 +578,19 @@ static ssize_t vfio_ccw_mdev_ioctl(struct mdev_device *mdev,
 	}
 }
 
-static const struct mdev_parent_ops vfio_ccw_mdev_ops = {
-	.owner			= THIS_MODULE,
-	.supported_type_groups  = mdev_type_groups,
-	.create			= vfio_ccw_mdev_create,
-	.remove			= vfio_ccw_mdev_remove,
+static const struct mdev_vfio_ops vfio_ccw_mdev_vfio_ops = {
 	.open			= vfio_ccw_mdev_open,
 	.release		= vfio_ccw_mdev_release,
 	.read			= vfio_ccw_mdev_read,
 	.write			= vfio_ccw_mdev_write,
 	.ioctl			= vfio_ccw_mdev_ioctl,
+}
+
+static const struct mdev_parent_ops vfio_ccw_mdev_ops = {
+	.owner			= THIS_MODULE,
+	.supported_type_groups  = mdev_type_groups,
+	.create			= vfio_ccw_mdev_create,
+	.remove			= vfio_ccw_mdev_remove,
 };
 
 int vfio_ccw_mdev_reg(struct subchannel *sch)
diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index 78048e670374..0649c68287d7 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -321,6 +321,8 @@ static void vfio_ap_matrix_init(struct ap_config_info *info,
 	matrix->adm_max = info->apxa ? info->Nd : 15;
 }
 
+static const struct mdev_vfio_ops vfio_ap_matrix_mdev_ops;
+
 static int vfio_ap_mdev_create(struct kobject *kobj, struct mdev_device *mdev)
 {
 	struct ap_matrix_mdev *matrix_mdev;
@@ -343,6 +345,8 @@ static int vfio_ap_mdev_create(struct kobject *kobj, struct mdev_device *mdev)
 	list_add(&matrix_mdev->node, &matrix_dev->mdev_list);
 	mutex_unlock(&matrix_dev->lock);
 
+	mdev_vfio_set_ops(mdev, &vfio_ap_matrix_mdev_ops);
+
 	return 0;
 }
 
@@ -1280,15 +1284,18 @@ static ssize_t vfio_ap_mdev_ioctl(struct mdev_device *mdev,
 	return ret;
 }
 
+static const struct mdev_vfio_ops vfio_ap_matrix_mdev_ops = {
+	.open			= vfio_ap_mdev_open,
+	.release		= vfio_ap_mdev_release,
+	.ioctl			= vfio_ap_mdev_ioctl,
+}
+
 static const struct mdev_parent_ops vfio_ap_matrix_ops = {
 	.owner			= THIS_MODULE,
 	.supported_type_groups	= vfio_ap_mdev_type_groups,
 	.mdev_attr_groups	= vfio_ap_mdev_attr_groups,
 	.create			= vfio_ap_mdev_create,
 	.remove			= vfio_ap_mdev_remove,
-	.open			= vfio_ap_mdev_open,
-	.release		= vfio_ap_mdev_release,
-	.ioctl			= vfio_ap_mdev_ioctl,
 };
 
 int vfio_ap_mdev_register(void)
diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
index e1272a40c521..c6bc67bf63fa 100644
--- a/drivers/vfio/mdev/mdev_core.c
+++ b/drivers/vfio/mdev/mdev_core.c
@@ -179,7 +179,7 @@ static struct class_compat *mdev_alloc_class_compat(struct bus_type *bus)
  * Returns a negative value on error, otherwise 0.
  */
 int mdev_register_device(struct device *dev, const struct mdev_parent_ops *ops,
-			 struct bus_type *bus)
+			 struct bus_type *bus, size_t dev_size)
 {
 	int ret;
 	struct mdev_parent *parent;
@@ -217,6 +217,7 @@ int mdev_register_device(struct device *dev, const struct mdev_parent_ops *ops,
 	parent->dev = dev;
 	parent->ops = ops;
 	parent->bus = bus;
+	parent->dev_size = dev_size;
 
 	mutex_lock(&compat_list_lock);
 	class_compat = mdev_alloc_class_compat(bus);
@@ -339,7 +340,7 @@ int mdev_device_create(struct kobject *kobj,
 		}
 	}
 
-	mdev = kzalloc(sizeof(*mdev), GFP_KERNEL);
+	mdev = kzalloc(parent->dev_size, GFP_KERNEL);
 	if (!mdev) {
 		mutex_unlock(&mdev_list_lock);
 		ret = -ENOMEM;
diff --git a/drivers/vfio/mdev/mdev_private.h b/drivers/vfio/mdev/mdev_private.h
index 298d7a0f493a..012ab80719e9 100644
--- a/drivers/vfio/mdev/mdev_private.h
+++ b/drivers/vfio/mdev/mdev_private.h
@@ -20,6 +20,7 @@ struct mdev_parent {
 	struct list_head type_list;
 	/* Synchronize device creation/removal with parent unregistration */
 	struct rw_semaphore unreg_sem;
+	size_t dev_size;
 };
 
 struct mdev_device {
@@ -66,4 +67,8 @@ int  mdev_device_create(struct kobject *kobj,
 			struct device *dev, const guid_t *uuid);
 int  mdev_device_remove(struct device *dev);
 
+int mdev_register_device(struct device *dev, const struct mdev_parent_ops *ops,
+			 struct bus_type *bus, size_t dev_size);
+void mdev_unregister_device(struct device *dev);
+
 #endif /* MDEV_PRIVATE_H */
diff --git a/drivers/vfio/mdev/mdev_vfio.c b/drivers/vfio/mdev/mdev_vfio.c
index f9d1191b9982..44e116074f88 100644
--- a/drivers/vfio/mdev/mdev_vfio.c
+++ b/drivers/vfio/mdev/mdev_vfio.c
@@ -4,6 +4,8 @@
 #include <linux/device.h>
 #include <linux/mdev_vfio.h>
 
+#include "mdev_private.h"
+
 #define DRIVER_VERSION		"0.1"
 #define DRIVER_AUTHOR		"Jason Wang"
 #define DRIVER_DESC		"Mediated VFIO bus"
@@ -15,6 +17,31 @@ struct bus_type mdev_vfio_bus_type = {
 };
 EXPORT_SYMBOL(mdev_vfio_bus_type);
 
+#define to_vfio_mdev_device(mdev) container_of(mdev, \
+					       struct mdev_vfio_device, mdev)
+
+struct mdev_vfio_device {
+	struct mdev_device mdev;
+	const struct mdev_vfio_ops *ops;
+};
+
+void mdev_vfio_set_ops(struct mdev_device *mdev,
+		       const struct mdev_vfio_ops *ops)
+{
+	struct mdev_vfio_device *mdev_vfio = to_vfio_mdev_device(mdev);
+
+	mdev_vfio->ops = ops;
+}
+EXPORT_SYMBOL(mdev_vfio_set_ops);
+
+const struct mdev_vfio_ops *mdev_vfio_get_ops(struct mdev_device *mdev)
+{
+	struct mdev_vfio_device *mdev_vfio = to_vfio_mdev_device(mdev);
+
+	return mdev_vfio->ops;
+}
+EXPORT_SYMBOL(mdev_vfio_get_ops);
+
 static int __init mdev_init(void)
 {
 	return mdev_register_bus(&mdev_vfio_bus_type);
@@ -28,7 +55,8 @@ static void __exit mdev_exit(void)
 int mdev_vfio_register_device(struct device *dev,
 			      const struct mdev_parent_ops *ops)
 {
-	return mdev_register_device(dev, ops, &mdev_vfio_bus_type);
+	return mdev_register_device(dev, ops, &mdev_vfio_bus_type,
+				    sizeof(struct mdev_vfio_device));
 }
 EXPORT_SYMBOL(mdev_vfio_register_device);
 
diff --git a/drivers/vfio/mdev/vfio_mdev.c b/drivers/vfio/mdev/vfio_mdev.c
index 16e9ebe30d4a..8b42a4b3f161 100644
--- a/drivers/vfio/mdev/vfio_mdev.c
+++ b/drivers/vfio/mdev/vfio_mdev.c
@@ -24,16 +24,16 @@
 static int vfio_mdev_open(void *device_data)
 {
 	struct mdev_device *mdev = device_data;
-	struct mdev_parent *parent = mdev->parent;
+	const struct mdev_vfio_ops *ops = mdev_vfio_get_ops(mdev);
 	int ret;
 
-	if (unlikely(!parent->ops->open))
+	if (unlikely(!ops->open))
 		return -EINVAL;
 
 	if (!try_module_get(THIS_MODULE))
 		return -ENODEV;
 
-	ret = parent->ops->open(mdev);
+	ret = ops->open(mdev);
 	if (ret)
 		module_put(THIS_MODULE);
 
@@ -43,10 +43,10 @@ static int vfio_mdev_open(void *device_data)
 static void vfio_mdev_release(void *device_data)
 {
 	struct mdev_device *mdev = device_data;
-	struct mdev_parent *parent = mdev->parent;
+	const struct mdev_vfio_ops *ops = mdev_vfio_get_ops(mdev);
 
-	if (likely(parent->ops->release))
-		parent->ops->release(mdev);
+	if (likely(ops->release))
+		ops->release(mdev);
 
 	module_put(THIS_MODULE);
 }
@@ -55,47 +55,47 @@ static long vfio_mdev_unlocked_ioctl(void *device_data,
 				     unsigned int cmd, unsigned long arg)
 {
 	struct mdev_device *mdev = device_data;
-	struct mdev_parent *parent = mdev->parent;
+	const struct mdev_vfio_ops *ops = mdev_vfio_get_ops(mdev);
 
-	if (unlikely(!parent->ops->ioctl))
+	if (unlikely(!ops->ioctl))
 		return -EINVAL;
 
-	return parent->ops->ioctl(mdev, cmd, arg);
+	return ops->ioctl(mdev, cmd, arg);
 }
 
 static ssize_t vfio_mdev_read(void *device_data, char __user *buf,
 			      size_t count, loff_t *ppos)
 {
 	struct mdev_device *mdev = device_data;
-	struct mdev_parent *parent = mdev->parent;
+	const struct mdev_vfio_ops *ops = mdev_vfio_get_ops(mdev);
 
-	if (unlikely(!parent->ops->read))
+	if (unlikely(!ops->read))
 		return -EINVAL;
 
-	return parent->ops->read(mdev, buf, count, ppos);
+	return ops->read(mdev, buf, count, ppos);
 }
 
 static ssize_t vfio_mdev_write(void *device_data, const char __user *buf,
 			       size_t count, loff_t *ppos)
 {
 	struct mdev_device *mdev = device_data;
-	struct mdev_parent *parent = mdev->parent;
+	const struct mdev_vfio_ops *ops = mdev_vfio_get_ops(mdev);
 
-	if (unlikely(!parent->ops->write))
+	if (unlikely(!ops->write))
 		return -EINVAL;
 
-	return parent->ops->write(mdev, buf, count, ppos);
+	return ops->write(mdev, buf, count, ppos);
 }
 
 static int vfio_mdev_mmap(void *device_data, struct vm_area_struct *vma)
 {
 	struct mdev_device *mdev = device_data;
-	struct mdev_parent *parent = mdev->parent;
+	const struct mdev_vfio_ops *ops = mdev_vfio_get_ops(mdev);
 
-	if (unlikely(!parent->ops->mmap))
+	if (unlikely(!ops->mmap))
 		return -EINVAL;
 
-	return parent->ops->mmap(mdev, vma);
+	return ops->mmap(mdev, vma);
 }
 
 static const struct vfio_device_ops vfio_mdev_dev_ops = {
@@ -110,7 +110,7 @@ static const struct vfio_device_ops vfio_mdev_dev_ops = {
 
 static int vfio_mdev_probe(struct device *dev)
 {
-	struct mdev_device *mdev = to_mdev_device(dev);
+	struct mdev_device *mdev = mdev_from_dev(dev, &mdev_vfio_bus_type);
 
 	return vfio_add_group_dev(dev, &vfio_mdev_dev_ops, mdev);
 }
diff --git a/include/linux/mdev.h b/include/linux/mdev.h
index ee2410246b3c..25554e55bcee 100644
--- a/include/linux/mdev.h
+++ b/include/linux/mdev.h
@@ -48,30 +48,6 @@ struct device *mdev_get_iommu_device(struct device *dev);
  *			@mdev: mdev_device device structure which is being
  *			       destroyed
  *			Returns integer: success (0) or error (< 0)
- * @open:		Open mediated device.
- *			@mdev: mediated device.
- *			Returns integer: success (0) or error (< 0)
- * @release:		release mediated device
- *			@mdev: mediated device.
- * @read:		Read emulation callback
- *			@mdev: mediated device structure
- *			@buf: read buffer
- *			@count: number of bytes to read
- *			@ppos: address.
- *			Retuns number on bytes read on success or error.
- * @write:		Write emulation callback
- *			@mdev: mediated device structure
- *			@buf: write buffer
- *			@count: number of bytes to be written
- *			@ppos: address.
- *			Retuns number on bytes written on success or error.
- * @ioctl:		IOCTL callback
- *			@mdev: mediated device structure
- *			@cmd: ioctl command
- *			@arg: arguments to ioctl
- * @mmap:		mmap callback
- *			@mdev: mediated device structure
- *			@vma: vma structure
  * Parent device that support mediated device should be registered with mdev
  * module with mdev_parent_ops structure.
  **/
@@ -83,15 +59,6 @@ struct mdev_parent_ops {
 
 	int     (*create)(struct kobject *kobj, struct mdev_device *mdev);
 	int     (*remove)(struct mdev_device *mdev);
-	int     (*open)(struct mdev_device *mdev);
-	void    (*release)(struct mdev_device *mdev);
-	ssize_t (*read)(struct mdev_device *mdev, char __user *buf,
-			size_t count, loff_t *ppos);
-	ssize_t (*write)(struct mdev_device *mdev, const char __user *buf,
-			 size_t count, loff_t *ppos);
-	long	(*ioctl)(struct mdev_device *mdev, unsigned int cmd,
-			 unsigned long arg);
-	int	(*mmap)(struct mdev_device *mdev, struct vm_area_struct *vma);
 };
 
 /* interface for exporting mdev supported type attributes */
@@ -133,10 +100,6 @@ void *mdev_get_drvdata(struct mdev_device *mdev);
 void mdev_set_drvdata(struct mdev_device *mdev, void *data);
 const guid_t *mdev_uuid(struct mdev_device *mdev);
 
-int mdev_register_device(struct device *dev, const struct mdev_parent_ops *ops,
-			 struct bus_type *bus);
-void mdev_unregister_device(struct device *dev);
-
 int mdev_register_driver(struct mdev_driver *drv, struct module *owner,
 			 struct bus_type *bus);
 void mdev_unregister_driver(struct mdev_driver *drv);
diff --git a/include/linux/mdev_vfio.h b/include/linux/mdev_vfio.h
index 446a7537e3fb..243ad85019a6 100644
--- a/include/linux/mdev_vfio.h
+++ b/include/linux/mdev_vfio.h
@@ -13,6 +13,45 @@
 
 extern struct bus_type mdev_vfio_bus_type;
 
+/* VFIO mdev ops
+ *
+ * @open:		Open mediated device.
+ *			@mdev: mediated device.
+ *			Returns integer: success (0) or error (< 0)
+ * @release:		release mediated device
+ *			@mdev: mediated device.
+ * @read:		Read emulation callback
+ *			@mdev: mediated device structure
+ *			@buf: read buffer
+ *			@count: number of bytes to read
+ *			@ppos: address.
+ *			Retuns number on bytes read on success or error.
+ * @write:		Write emulation callback
+ *			@mdev: mediated device structure
+ *			@buf: write buffer
+ *			@count: number of bytes to be written
+ *			@ppos: address.
+ *			Retuns number on bytes written on success or error.
+ * @ioctl:		IOCTL callback
+ *			@mdev: mediated device structure
+ *			@cmd: ioctl command
+ *			@arg: arguments to ioctl
+ * @mmap:		mmap callback
+ *			@mdev: mediated device structure
+ *			@vma: vma structure
+ */
+struct mdev_vfio_ops {
+	int     (*open)(struct mdev_device *mdev);
+	void    (*release)(struct mdev_device *mdev);
+	ssize_t (*read)(struct mdev_device *mdev, char __user *buf,
+			size_t count, loff_t *ppos);
+	ssize_t (*write)(struct mdev_device *mdev, const char __user *buf,
+			 size_t count, loff_t *ppos);
+	long	(*ioctl)(struct mdev_device *mdev, unsigned int cmd,
+			 unsigned long arg);
+	int	(*mmap)(struct mdev_device *mdev, struct vm_area_struct *vma);
+};
+
 int mdev_vfio_register_device(struct device *dev,
 			      const struct mdev_parent_ops *ops);
 void mdev_vfio_unregister_device(struct device *dev);
@@ -22,4 +61,8 @@ static inline struct mdev_device *vfio_mdev_from_dev(struct device *dev)
 	return mdev_from_dev(dev, &mdev_vfio_bus_type);
 }
 
+void mdev_vfio_set_ops(struct mdev_device *mdev,
+		       const struct mdev_vfio_ops *ops);
+const struct mdev_vfio_ops *mdev_vfio_get_ops(struct mdev_device *mdev);
+
 #endif
diff --git a/samples/vfio-mdev/mbochs.c b/samples/vfio-mdev/mbochs.c
index f041d58324b1..b2ba32b5fed2 100644
--- a/samples/vfio-mdev/mbochs.c
+++ b/samples/vfio-mdev/mbochs.c
@@ -516,6 +516,8 @@ static int mbochs_reset(struct mdev_device *mdev)
 	return 0;
 }
 
+static const struct mdev_vfio_ops mdev_ops;
+
 static int mbochs_create(struct kobject *kobj, struct mdev_device *mdev)
 {
 	const struct mbochs_type *type = mbochs_find_type(kobj);
@@ -561,6 +563,7 @@ static int mbochs_create(struct kobject *kobj, struct mdev_device *mdev)
 	mbochs_reset(mdev);
 
 	mbochs_used_mbytes += type->mbytes;
+	mdev_vfio_set_ops(mdev, &mdev_ops);
 	return 0;
 
 err_mem:
@@ -1418,12 +1421,7 @@ static struct attribute_group *mdev_type_groups[] = {
 	NULL,
 };
 
-static const struct mdev_parent_ops mdev_fops = {
-	.owner			= THIS_MODULE,
-	.mdev_attr_groups	= mdev_dev_groups,
-	.supported_type_groups	= mdev_type_groups,
-	.create			= mbochs_create,
-	.remove			= mbochs_remove,
+static const struct mdev_vfio_ops mdev_ops = {
 	.open			= mbochs_open,
 	.release		= mbochs_close,
 	.read			= mbochs_read,
@@ -1432,6 +1430,14 @@ static const struct mdev_parent_ops mdev_fops = {
 	.mmap			= mbochs_mmap,
 };
 
+static const struct mdev_parent_ops mdev_fops = {
+	.owner			= THIS_MODULE,
+	.mdev_attr_groups	= mdev_dev_groups,
+	.supported_type_groups	= mdev_type_groups,
+	.create			= mbochs_create,
+	.remove			= mbochs_remove,
+};
+
 static const struct file_operations vd_fops = {
 	.owner		= THIS_MODULE,
 };
diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
index 9c32fe3795ad..d26fd94b4783 100644
--- a/samples/vfio-mdev/mdpy.c
+++ b/samples/vfio-mdev/mdpy.c
@@ -226,6 +226,8 @@ static int mdpy_reset(struct mdev_device *mdev)
 	return 0;
 }
 
+static const struct mdev_vfio_ops mdev_ops;
+
 static int mdpy_create(struct kobject *kobj, struct mdev_device *mdev)
 {
 	const struct mdpy_type *type = mdpy_find_type(kobj);
@@ -269,6 +271,8 @@ static int mdpy_create(struct kobject *kobj, struct mdev_device *mdev)
 	mdpy_reset(mdev);
 
 	mdpy_count++;
+
+	mdev_vfio_set_ops(mdev, &mdev_ops);
 	return 0;
 }
 
@@ -725,12 +729,7 @@ static struct attribute_group *mdev_type_groups[] = {
 	NULL,
 };
 
-static const struct mdev_parent_ops mdev_fops = {
-	.owner			= THIS_MODULE,
-	.mdev_attr_groups	= mdev_dev_groups,
-	.supported_type_groups	= mdev_type_groups,
-	.create			= mdpy_create,
-	.remove			= mdpy_remove,
+static const struct mdev_vfio_ops mdev_ops = {
 	.open			= mdpy_open,
 	.release		= mdpy_close,
 	.read			= mdpy_read,
@@ -739,6 +738,14 @@ static const struct mdev_parent_ops mdev_fops = {
 	.mmap			= mdpy_mmap,
 };
 
+static const struct mdev_parent_ops mdev_fops = {
+	.owner			= THIS_MODULE,
+	.mdev_attr_groups	= mdev_dev_groups,
+	.supported_type_groups	= mdev_type_groups,
+	.create			= mdpy_create,
+	.remove			= mdpy_remove,
+};
+
 static const struct file_operations vd_fops = {
 	.owner		= THIS_MODULE,
 };
diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
index 6e4e6339e0f1..3f0c6506199a 100644
--- a/samples/vfio-mdev/mtty.c
+++ b/samples/vfio-mdev/mtty.c
@@ -708,6 +708,8 @@ static ssize_t mdev_access(struct mdev_device *mdev, u8 *buf, size_t count,
 	return ret;
 }
 
+static const struct mdev_vfio_ops mdev_ops;
+
 static int mtty_create(struct kobject *kobj, struct mdev_device *mdev)
 {
 	struct mdev_state *mdev_state;
@@ -755,6 +757,7 @@ static int mtty_create(struct kobject *kobj, struct mdev_device *mdev)
 	list_add(&mdev_state->next, &mdev_devices_list);
 	mutex_unlock(&mdev_list_lock);
 
+	mdev_vfio_set_ops(mdev, &mdev_ops);
 	return 0;
 }
 
@@ -1387,6 +1390,14 @@ static struct attribute_group *mdev_type_groups[] = {
 	NULL,
 };
 
+static const struct mdev_vfio_ops mdev_ops = {
+	.open                   = mtty_open,
+	.release                = mtty_close,
+	.read                   = mtty_read,
+	.write                  = mtty_write,
+	.ioctl		        = mtty_ioctl,
+};
+
 static const struct mdev_parent_ops mdev_fops = {
 	.owner                  = THIS_MODULE,
 	.dev_attr_groups        = mtty_dev_groups,
@@ -1394,11 +1405,6 @@ static const struct mdev_parent_ops mdev_fops = {
 	.supported_type_groups  = mdev_type_groups,
 	.create                 = mtty_create,
 	.remove			= mtty_remove,
-	.open                   = mtty_open,
-	.release                = mtty_close,
-	.read                   = mtty_read,
-	.write                  = mtty_write,
-	.ioctl		        = mtty_ioctl,
 };
 
 static void mtty_device_release(struct device *dev)
-- 
2.19.1