Re: [PATCH 04/15] vfio/mdev: embedd struct mdev_parent in the parent data structure

Vineeth Vijayan
2022-07-07T07:22:42Z

On Wed, Jul 06, 2022 at 11:08:28PM -0400, Eric Farman wrote:
> On Wed, 2022-07-06 at 09:42 +0200, Christoph Hellwig wrote:
> > Simplify mdev_{un}register_device by requiring the caller to pass in
> > a structure allocate as part of the parent device structure. This
> > removes the need for a list of parents and the separate mdev_parent
> > refcount as we can simplify rely on the reference to the parent
> > device.
> >
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> > Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
> > Reviewed-by: Kevin Tian <kevin.tian@intel.com>
> > ---
> > .../driver-api/vfio-mediated-device.rst | 12 +-
> > Documentation/s390/vfio-ap.rst | 2 +-
> > Documentation/s390/vfio-ccw.rst | 2 +-
> > drivers/gpu/drm/i915/gvt/gvt.h | 2 +
> > drivers/gpu/drm/i915/gvt/kvmgt.c | 5 +-
> > drivers/s390/cio/cio.h | 2 +
> > drivers/s390/cio/vfio_ccw_ops.c | 6 +-
>
> (@Vineeth, @Peter FYI regarding struct subchannel)
>
> I haven't had a chance to look at this series with enough focus, but
> the change to cio.h (here, and patch 5) caught my eye. I would've
> expected the "parent" to be struct vfio_ccw_private, instead of the
> subchannel.
>
> Eric
Thank you Eric for pointing it out. You are right. I think the struct
subchannel is obviously the wrong place.
Also, in this case, the mdev_parent should be in one of the vfio-ccw
io-subchannel structure, which as you mentioned should be in vfio-ccw*.

@Halil, Could you please have a look. I am not very familier with the
vfio yet.
>
> > drivers/s390/crypto/vfio_ap_ops.c | 5 +-
> > drivers/s390/crypto/vfio_ap_private.h | 1 +
> > drivers/vfio/mdev/mdev_core.c | 120 ++++----------
> > ----
> > drivers/vfio/mdev/mdev_private.h | 23 ----
> > drivers/vfio/mdev/mdev_sysfs.c | 4 +-
> > include/linux/mdev.h | 15 ++-
> > samples/vfio-mdev/mbochs.c | 5 +-
> > samples/vfio-mdev/mdpy.c | 5 +-
> > samples/vfio-mdev/mtty.c | 6 +-
> > 16 files changed, 69 insertions(+), 146 deletions(-)
> >
> > diff --git a/Documentation/driver-api/vfio-mediated-device.rst
> > b/Documentation/driver-api/vfio-mediated-device.rst
> > index 1c57815619fdf..62a82afce161b 100644
> > --- a/Documentation/driver-api/vfio-mediated-device.rst
> > +++ b/Documentation/driver-api/vfio-mediated-device.rst
> > @@ -60,19 +60,19 @@ devices as examples, as these devices are the
> > first devices to use this module::
> > | MDEV CORE |
> > | MODULE |
> > | mdev.ko |
> > - | +-----------+ | mdev_register_device() +--------------+
> > + | +-----------+ | mdev_register_parent() +--------------+
> > | | | +<------------------------+ |
> > | | | | | nvidia.ko |<->
> > physical
> > | | | +----------------------
> > -->+ | device
> > | | | | callbacks +--------------+
> > | | Physical | |
> > - | | device | | mdev_register_device() +--------------+
> > + | | device | | mdev_register_parent() +--------------+
> > | | interface | |<------------------------+ |
> > | | | | | i915.ko |<->
> > physical
> > | | | +----------------------
> > -->+ | device
> > | | | | callbacks +--------------+
> > | | | |
> > - | | | | mdev_register_device() +--------------+
> > + | | | | mdev_register_parent() +--------------+
> > | | | +<------------------------+ |
> > | | | | | ccw_device.ko|<->
> > physical
> > | | | +----------------------
> > -->+ | device
> > @@ -127,8 +127,8 @@ vfio_device_ops.
> > When a driver wants to add the GUID creation sysfs to an existing
> > device it has
> > probe'd to then it should call::
> >
> > - int mdev_register_device(struct device *dev,
> > - struct mdev_driver *mdev_driver);
> > + int mdev_register_parent(struct mdev_parent *parent, struct
> > device *dev,
> > + struct mdev_driver *mdev_driver);
> >
> > This will provide the 'mdev_supported_types/XX/create' files which
> > can then be
> > used to trigger the creation of a mdev_device. The created
> > mdev_device will be
> > @@ -136,7 +136,7 @@ attached to the specified driver.
> >
> > When the driver needs to remove itself it calls::
> >
> > - void mdev_unregister_device(struct device *dev);
> > + void mdev_unregister_parent(struct mdev_parent *parent);
> >
> > Which will unbind and destroy all the created mdevs and remove the
> > sysfs files.
> >
> > diff --git a/Documentation/s390/vfio-ap.rst
> > b/Documentation/s390/vfio-ap.rst
> > index f57ae621f33e8..37e16158c7fbf 100644
> > --- a/Documentation/s390/vfio-ap.rst
> > +++ b/Documentation/s390/vfio-ap.rst
> > @@ -299,7 +299,7 @@ of the VFIO AP mediated matrix device driver::
> > | MDEV CORE |
> > | MODULE |
> > | mdev.ko |
> > - | +---------+ | mdev_register_device() +--------------+
> > + | +---------+ | mdev_register_parent() +--------------+
> > | |Physical | +<-----------------------+ |
> > | | device | | | vfio_ap.ko |<-> matrix
> > | |interface| +----------------------->+ | device
> > diff --git a/Documentation/s390/vfio-ccw.rst
> > b/Documentation/s390/vfio-ccw.rst
> > index 8aad08a8b8a50..ea928a3806f43 100644
> > --- a/Documentation/s390/vfio-ccw.rst
> > +++ b/Documentation/s390/vfio-ccw.rst
> > @@ -156,7 +156,7 @@ Below is a high Level block diagram::
> > | MDEV CORE |
> > | MODULE |
> > | mdev.ko |
> > - | +---------+ | mdev_register_device() +--------------+
> > + | +---------+ | mdev_register_parent() +--------------+
> > | |Physical | +<-----------------------+ |
> > | | device | | | vfio_ccw.ko |<->
> > subchannel
> > | |interface| +----------------------->+ | device
> > diff --git a/drivers/gpu/drm/i915/gvt/gvt.h
> > b/drivers/gpu/drm/i915/gvt/gvt.h
> > index 392c2ad49d376..bbf0116671ecb 100644
> > --- a/drivers/gpu/drm/i915/gvt/gvt.h
> > +++ b/drivers/gpu/drm/i915/gvt/gvt.h
> > @@ -36,6 +36,7 @@
> > #include <uapi/linux/pci_regs.h>
> > #include <linux/kvm_host.h>
> > #include <linux/vfio.h>
> > +#include <linux/mdev.h>
> >
> > #include "i915_drv.h"
> > #include "intel_gvt.h"
> > @@ -338,6 +339,7 @@ struct intel_gvt {
> > struct intel_gvt_workload_scheduler scheduler;
> > struct notifier_block
> > shadow_ctx_notifier_block[I915_NUM_ENGINES];
> > DECLARE_HASHTABLE(cmd_table, GVT_CMD_HASH_BITS);
> > + struct mdev_parent parent;
> > struct intel_vgpu_type *types;
> > unsigned int num_types;
> > struct intel_vgpu *idle_vgpu;
> > diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c
> > b/drivers/gpu/drm/i915/gvt/kvmgt.c
> > index 85e1393d8e55c..e9dba4c0fe6b5 100644
> > --- a/drivers/gpu/drm/i915/gvt/kvmgt.c
> > +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
> > @@ -1958,7 +1958,7 @@ static void intel_gvt_clean_device(struct
> > drm_i915_private *i915)
> > if (drm_WARN_ON(&i915->drm, !gvt))
> > return;
> >
> > - mdev_unregister_device(i915->drm.dev);
> > + mdev_unregister_parent(&gvt->parent);
> > intel_gvt_cleanup_vgpu_type_groups(gvt);
> > intel_gvt_destroy_idle_vgpu(gvt->idle_vgpu);
> > intel_gvt_clean_vgpu_types(gvt);
> > @@ -2063,7 +2063,8 @@ static int intel_gvt_init_device(struct
> > drm_i915_private *i915)
> > if (ret)
> > goto out_destroy_idle_vgpu;
> >
> > - ret = mdev_register_device(i915->drm.dev,
> > &intel_vgpu_mdev_driver);
> > + ret = mdev_register_parent(&gvt->parent, i915->drm.dev,
> > + &intel_vgpu_mdev_driver);
> > if (ret)
> > goto out_cleanup_vgpu_type_groups;
> >
> > diff --git a/drivers/s390/cio/cio.h b/drivers/s390/cio/cio.h
> > index fa8df50bb49e3..22be5ac7d23c1 100644
> > --- a/drivers/s390/cio/cio.h
> > +++ b/drivers/s390/cio/cio.h
> > @@ -5,6 +5,7 @@
> > #include <linux/mutex.h>
> > #include <linux/device.h>
> > #include <linux/mod_devicetable.h>
> > +#include <linux/mdev.h>
> > #include <asm/chpid.h>
> > #include <asm/cio.h>
> > #include <asm/fcx.h>
> > @@ -108,6 +109,7 @@ struct subchannel {
> > * frees it. Use driver_set_override() to set or clear it.
> > */
> > const char *driver_override;
> > + struct mdev_parent parent;
> > } __attribute__ ((aligned(8)));
> >
> > DECLARE_PER_CPU_ALIGNED(struct irb, cio_irb);
> > diff --git a/drivers/s390/cio/vfio_ccw_ops.c
> > b/drivers/s390/cio/vfio_ccw_ops.c
> > index b49e2e9db2dc6..9192a21085ce4 100644
> > --- a/drivers/s390/cio/vfio_ccw_ops.c
> > +++ b/drivers/s390/cio/vfio_ccw_ops.c
> > @@ -11,7 +11,6 @@
> > */
> >
> > #include <linux/vfio.h>
> > -#include <linux/mdev.h>
> > #include <linux/nospec.h>
> > #include <linux/slab.h>
> >
> > @@ -660,10 +659,11 @@ struct mdev_driver vfio_ccw_mdev_driver = {
> >
> > int vfio_ccw_mdev_reg(struct subchannel *sch)
> > {
> > - return mdev_register_device(&sch->dev, &vfio_ccw_mdev_driver);
> > + return mdev_register_parent(&sch->parent, &sch->dev,
> > + &vfio_ccw_mdev_driver);
> > }
> >
> > void vfio_ccw_mdev_unreg(struct subchannel *sch)
> > {
> > - mdev_unregister_device(&sch->dev);
> > + mdev_unregister_parent(&sch->parent);
> > }
> > diff --git a/drivers/s390/crypto/vfio_ap_ops.c
> > b/drivers/s390/crypto/vfio_ap_ops.c
> > index a7d2a95796d36..834945150dc9f 100644
> > --- a/drivers/s390/crypto/vfio_ap_ops.c
> > +++ b/drivers/s390/crypto/vfio_ap_ops.c
> > @@ -1485,7 +1485,8 @@ int vfio_ap_mdev_register(void)
> > if (ret)
> > return ret;
> >
> > - ret = mdev_register_device(&matrix_dev->device,
> > &vfio_ap_matrix_driver);
> > + ret = mdev_register_parent(&matrix_dev->parent, &matrix_dev-
> > >device,
> > + &vfio_ap_matrix_driver);
> > if (ret)
> > goto err_driver;
> > return 0;
> > @@ -1497,6 +1498,6 @@ int vfio_ap_mdev_register(void)
> >
> > void vfio_ap_mdev_unregister(void)
> > {
> > - mdev_unregister_device(&matrix_dev->device);
> > + mdev_unregister_parent(&matrix_dev->parent);
> > mdev_unregister_driver(&vfio_ap_matrix_driver);
> > }
> > diff --git a/drivers/s390/crypto/vfio_ap_private.h
> > b/drivers/s390/crypto/vfio_ap_private.h
> > index 6616aa83347ad..0191f6bc973a4 100644
> > --- a/drivers/s390/crypto/vfio_ap_private.h
> > +++ b/drivers/s390/crypto/vfio_ap_private.h
> > @@ -45,6 +45,7 @@ struct ap_matrix_dev {
> > struct list_head mdev_list;
> > struct mutex lock;
> > struct ap_driver *vfio_ap_drv;
> > + struct mdev_parent parent;
> > };
> >
> > extern struct ap_matrix_dev *matrix_dev;
> > diff --git a/drivers/vfio/mdev/mdev_core.c
> > b/drivers/vfio/mdev/mdev_core.c
> > index 2c32923fbad27..fa05ac3396950 100644
> > --- a/drivers/vfio/mdev/mdev_core.c
> > +++ b/drivers/vfio/mdev/mdev_core.c
> > @@ -18,8 +18,6 @@
> > #define DRIVER_AUTHOR "NVIDIA Corporation"
> > #define DRIVER_DESC "Mediated device Core Driver"
> >
> > -static LIST_HEAD(parent_list);
> > -static DEFINE_MUTEX(parent_list_lock);
> > static struct class_compat *mdev_bus_compat_class;
> >
> > static LIST_HEAD(mdev_list);
> > @@ -61,28 +59,6 @@ struct device *mtype_get_parent_dev(struct
> > mdev_type *mtype)
> > }
> > EXPORT_SYMBOL(mtype_get_parent_dev);
> >
> > -/* Should be called holding parent_list_lock */
> > -static struct mdev_parent *__find_parent_device(struct device *dev)
> > -{
> > - struct mdev_parent *parent;
> > -
> > - list_for_each_entry(parent, &parent_list, next) {
> > - if (parent->dev == dev)
> > - return parent;
> > - }
> > - return NULL;
> > -}
> > -
> > -void mdev_release_parent(struct kref *kref)
> > -{
> > - struct mdev_parent *parent = container_of(kref, struct
> > mdev_parent,
> > - ref);
> > - struct device *dev = parent->dev;
> > -
> > - kfree(parent);
> > - put_device(dev);
> > -}
> > -
> > /* Caller must hold parent unreg_sem read or write lock */
> > static void mdev_device_remove_common(struct mdev_device *mdev)
> > {
> > @@ -105,125 +81,73 @@ static int mdev_device_remove_cb(struct device
> > *dev, void *data)
> > }
> >
> > /*
> > - * mdev_register_device : Register a device
> > + * mdev_register_parent: Register a device as parent for mdevs
> > + * @parent: parent structure registered
> > * @dev: device structure representing parent device.
> > * @mdev_driver: Device driver to bind to the newly created mdev
> > *
> > - * Add device to list of registered parent devices.
> > + * Registers the @parent stucture as a parent for mdev types and
> > thus mdev
> > + * devices. The caller needs to hold a reference on @dev that must
> > not be
> > + * released until after the call to mdev_unregister_parent().
> > + *
> > * Returns a negative value on error, otherwise 0.
> > */
> > -int mdev_register_device(struct device *dev, struct mdev_driver
> > *mdev_driver)
> > +int mdev_register_parent(struct mdev_parent *parent, struct device
> > *dev,
> > + struct mdev_driver *mdev_driver)
> > {
> > - int ret;
> > - struct mdev_parent *parent;
> > char *env_string = "MDEV_STATE=registered";
> > char *envp[] = { env_string, NULL };
> > + int ret;
> >
> > /* check for mandatory ops */
> > if (!mdev_driver->supported_type_groups)
> > return -EINVAL;
> >
> > - dev = get_device(dev);
> > - if (!dev)
> > - return -EINVAL;
> > -
> > - mutex_lock(&parent_list_lock);
> > -
> > - /* Check for duplicate */
> > - parent = __find_parent_device(dev);
> > - if (parent) {
> > - parent = NULL;
> > - ret = -EEXIST;
> > - goto add_dev_err;
> > - }
> > -
> > - parent = kzalloc(sizeof(*parent), GFP_KERNEL);
> > - if (!parent) {
> > - ret = -ENOMEM;
> > - goto add_dev_err;
> > - }
> > -
> > - kref_init(&parent->ref);
> > + memset(parent, 0, sizeof(*parent));
> > init_rwsem(&parent->unreg_sem);
> > -
> > parent->dev = dev;
> > parent->mdev_driver = mdev_driver;
> >
> > if (!mdev_bus_compat_class) {
> > mdev_bus_compat_class =
> > class_compat_register("mdev_bus");
> > - if (!mdev_bus_compat_class) {
> > - ret = -ENOMEM;
> > - goto add_dev_err;
> > - }
> > + if (!mdev_bus_compat_class)
> > + return -ENOMEM;
> > }
> >
> > ret = parent_create_sysfs_files(parent);
> > if (ret)
> > - goto add_dev_err;
> > + return ret;
> >
> > ret = class_compat_create_link(mdev_bus_compat_class, dev,
> > NULL);
> > if (ret)
> > dev_warn(dev, "Failed to create compatibility class
> > link\n");
> >
> > - list_add(&parent->next, &parent_list);
> > - mutex_unlock(&parent_list_lock);
> > -
> > dev_info(dev, "MDEV: Registered\n");
> > kobject_uevent_env(&dev->kobj, KOBJ_CHANGE, envp);
> > -
> > return 0;
> > -
> > -add_dev_err:
> > - mutex_unlock(&parent_list_lock);
> > - if (parent)
> > - mdev_put_parent(parent);
> > - else
> > - put_device(dev);
> > - return ret;
> > }
> > -EXPORT_SYMBOL(mdev_register_device);
> > +EXPORT_SYMBOL(mdev_register_parent);
> >
> > /*
> > - * mdev_unregister_device : Unregister a parent device
> > - * @dev: device structure representing parent device.
> > - *
> > - * Remove device from list of registered parent devices. Give a
> > chance to free
> > - * existing mediated devices for given device.
> > + * mdev_unregister_parent : Unregister a parent device
> > + * @parent: parent structure to unregister
> > */
> > -
> > -void mdev_unregister_device(struct device *dev)
> > +void mdev_unregister_parent(struct mdev_parent *parent)
> > {
> > - struct mdev_parent *parent;
> > char *env_string = "MDEV_STATE=unregistered";
> > char *envp[] = { env_string, NULL };
> >
> > - mutex_lock(&parent_list_lock);
> > - parent = __find_parent_device(dev);
> > -
> > - if (!parent) {
> > - mutex_unlock(&parent_list_lock);
> > - return;
> > - }
> > - dev_info(dev, "MDEV: Unregistering\n");
> > -
> > - list_del(&parent->next);
> > - mutex_unlock(&parent_list_lock);
> > + dev_info(parent->dev, "MDEV: Unregistering\n");
> >
> > down_write(&parent->unreg_sem);
> > -
> > - class_compat_remove_link(mdev_bus_compat_class, dev, NULL);
> > -
> > - device_for_each_child(dev, NULL, mdev_device_remove_cb);
> > -
> > + class_compat_remove_link(mdev_bus_compat_class, parent->dev,
> > NULL);
> > + device_for_each_child(parent->dev, NULL,
> > mdev_device_remove_cb);
> > parent_remove_sysfs_files(parent);
> > up_write(&parent->unreg_sem);
> >
> > - mdev_put_parent(parent);
> > -
> > - /* We still have the caller's reference to use for the uevent
> > */
> > - kobject_uevent_env(&dev->kobj, KOBJ_CHANGE, envp);
> > + kobject_uevent_env(&parent->dev->kobj, KOBJ_CHANGE, envp);
> > }
> > -EXPORT_SYMBOL(mdev_unregister_device);
> > +EXPORT_SYMBOL(mdev_unregister_parent);
> >
> > static void mdev_device_release(struct device *dev)
> > {
> > diff --git a/drivers/vfio/mdev/mdev_private.h
> > b/drivers/vfio/mdev/mdev_private.h
> > index 7c9fc79f3d838..297f911fdc890 100644
> > --- a/drivers/vfio/mdev/mdev_private.h
> > +++ b/drivers/vfio/mdev/mdev_private.h
> > @@ -13,17 +13,6 @@
> > int mdev_bus_register(void);
> > void mdev_bus_unregister(void);
> >
> > -struct mdev_parent {
> > - struct device *dev;
> > - struct mdev_driver *mdev_driver;
> > - struct kref ref;
> > - struct list_head next;
> > - struct kset *mdev_types_kset;
> > - struct list_head type_list;
> > - /* Synchronize device creation/removal with parent
> > unregistration */
> > - struct rw_semaphore unreg_sem;
> > -};
> > -
> > struct mdev_type {
> > struct kobject kobj;
> > struct kobject *devices_kobj;
> > @@ -48,16 +37,4 @@ void mdev_remove_sysfs_files(struct mdev_device
> > *mdev);
> > int mdev_device_create(struct mdev_type *kobj, const guid_t *uuid);
> > int mdev_device_remove(struct mdev_device *dev);
> >
> > -void mdev_release_parent(struct kref *kref);
> > -
> > -static inline void mdev_get_parent(struct mdev_parent *parent)
> > -{
> > - kref_get(&parent->ref);
> > -}
> > -
> > -static inline void mdev_put_parent(struct mdev_parent *parent)
> > -{
> > - kref_put(&parent->ref, mdev_release_parent);
> > -}
> > -
> > #endif /* MDEV_PRIVATE_H */
> > diff --git a/drivers/vfio/mdev/mdev_sysfs.c
> > b/drivers/vfio/mdev/mdev_sysfs.c
> > index 4bfbf49aaa66a..b71ffc5594870 100644
> > --- a/drivers/vfio/mdev/mdev_sysfs.c
> > +++ b/drivers/vfio/mdev/mdev_sysfs.c
> > @@ -81,7 +81,7 @@ static void mdev_type_release(struct kobject *kobj)
> >
> > pr_debug("Releasing group %s\n", kobj->name);
> > /* Pairs with the get in add_mdev_supported_type() */
> > - mdev_put_parent(type->parent);
> > + put_device(type->parent->dev);
> > kfree(type);
> > }
> >
> > @@ -110,7 +110,7 @@ static struct mdev_type
> > *add_mdev_supported_type(struct mdev_parent *parent,
> > type->kobj.kset = parent->mdev_types_kset;
> > type->parent = parent;
> > /* Pairs with the put in mdev_type_release() */
> > - mdev_get_parent(parent);
> > + get_device(parent->dev);
> > type->type_group_id = type_group_id;
> >
> > ret = kobject_init_and_add(&type->kobj, &mdev_type_ktype, NULL,
> > diff --git a/include/linux/mdev.h b/include/linux/mdev.h
> > index 555c1d015b5f0..327ce3e5c6b5f 100644
> > --- a/include/linux/mdev.h
> > +++ b/include/linux/mdev.h
> > @@ -23,6 +23,16 @@ struct mdev_device {
> > bool active;
> > };
> >
> > +/* embedded into the struct device that the mdev devices hang off */
> > +struct mdev_parent {
> > + struct device *dev;
> > + struct mdev_driver *mdev_driver;
> > + struct kset *mdev_types_kset;
> > + struct list_head type_list;
> > + /* Synchronize device creation/removal with parent
> > unregistration */
> > + struct rw_semaphore unreg_sem;
> > +};
> > +
> > static inline struct mdev_device *to_mdev_device(struct device *dev)
> > {
> > return container_of(dev, struct mdev_device, dev);
> > @@ -75,8 +85,9 @@ static inline const guid_t *mdev_uuid(struct
> > mdev_device *mdev)
> >
> > extern struct bus_type mdev_bus_type;
> >
> > -int mdev_register_device(struct device *dev, struct mdev_driver
> > *mdev_driver);
> > -void mdev_unregister_device(struct device *dev);
> > +int mdev_register_parent(struct mdev_parent *parent, struct device
> > *dev,
> > + struct mdev_driver *mdev_driver);
> > +void mdev_unregister_parent(struct mdev_parent *parent);
> >
> > int mdev_register_driver(struct mdev_driver *drv);
> > void mdev_unregister_driver(struct mdev_driver *drv);
> > diff --git a/samples/vfio-mdev/mbochs.c b/samples/vfio-mdev/mbochs.c
> > index d0d1bb7747240..30b3643b3b389 100644
> > --- a/samples/vfio-mdev/mbochs.c
> > +++ b/samples/vfio-mdev/mbochs.c
> > @@ -128,6 +128,7 @@ static dev_t mbochs_devt;
> > static struct class *mbochs_class;
> > static struct cdev mbochs_cdev;
> > static struct device mbochs_dev;
> > +static struct mdev_parent mbochs_parent;
> > static atomic_t mbochs_avail_mbytes;
> > static const struct vfio_device_ops mbochs_dev_ops;
> >
> > @@ -1456,7 +1457,7 @@ static int __init mbochs_dev_init(void)
> > if (ret)
> > goto err_class;
> >
> > - ret = mdev_register_device(&mbochs_dev, &mbochs_driver);
> > + ret = mdev_register_parent(&mbochs_parent, &mbochs_dev,
> > &mbochs_driver);
> > if (ret)
> > goto err_device;
> >
> > @@ -1477,7 +1478,7 @@ static int __init mbochs_dev_init(void)
> > static void __exit mbochs_dev_exit(void)
> > {
> > mbochs_dev.bus = NULL;
> > - mdev_unregister_device(&mbochs_dev);
> > + mdev_unregister_parent(&mbochs_parent);
> >
> > device_unregister(&mbochs_dev);
> > mdev_unregister_driver(&mbochs_driver);
> > diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
> > index 0c4ca1f4be7ed..132bb055628a6 100644
> > --- a/samples/vfio-mdev/mdpy.c
> > +++ b/samples/vfio-mdev/mdpy.c
> > @@ -83,6 +83,7 @@ static dev_t mdpy_devt;
> > static struct class *mdpy_class;
> > static struct cdev mdpy_cdev;
> > static struct device mdpy_dev;
> > +static struct mdev_parent mdpy_parent;
> > static u32 mdpy_count;
> > static const struct vfio_device_ops mdpy_dev_ops;
> >
> > @@ -765,7 +766,7 @@ static int __init mdpy_dev_init(void)
> > if (ret)
> > goto err_class;
> >
> > - ret = mdev_register_device(&mdpy_dev, &mdpy_driver);
> > + ret = mdev_register_parent(&mdpy_parent, &mdpy_dev,
> > &mdpy_driver);
> > if (ret)
> > goto err_device;
> >
> > @@ -786,7 +787,7 @@ static int __init mdpy_dev_init(void)
> > static void __exit mdpy_dev_exit(void)
> > {
> > mdpy_dev.bus = NULL;
> > - mdev_unregister_device(&mdpy_dev);
> > + mdev_unregister_parent(&mdpy_parent);
> >
> > device_unregister(&mdpy_dev);
> > mdev_unregister_driver(&mdpy_driver);
> > diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
> > index 4f5a6f2d3629d..8ba5f6084a093 100644
> > --- a/samples/vfio-mdev/mtty.c
> > +++ b/samples/vfio-mdev/mtty.c
> > @@ -72,6 +72,7 @@ static struct mtty_dev {
> > struct cdev vd_cdev;
> > struct idr vd_idr;
> > struct device dev;
> > + struct mdev_parent parent;
> > } mtty_dev;
> >
> > struct mdev_region_info {
> > @@ -1350,7 +1351,8 @@ static int __init mtty_dev_init(void)
> > if (ret)
> > goto err_class;
> >
> > - ret = mdev_register_device(&mtty_dev.dev, &mtty_driver);
> > + ret = mdev_register_parent(&mtty_dev.parent, &mtty_dev.dev,
> > + &mtty_driver);
> > if (ret)
> > goto err_device;
> > return 0;
> > @@ -1370,7 +1372,7 @@ static int __init mtty_dev_init(void)
> > static void __exit mtty_dev_exit(void)
> > {
> > mtty_dev.dev.bus = NULL;
> > - mdev_unregister_device(&mtty_dev.dev);
> > + mdev_unregister_parent(&mtty_dev.parent);
> >
> > device_unregister(&mtty_dev.dev);
> > idr_destroy(&mtty_dev.vd_idr);
>