Re: [PATCH v2 15/15] vfio: Add struct device to vfio_device

[Eric Auger]

Hi Kevin,

On 9/1/22 16:37, Kevin Tian wrote:
> From: Yi Liu <yi.l.liu@xxxxxxxxx>
>
> and replace kref. With it a 'vfio-dev/vfioX' node is created under the
> sysfs path of the parent, indicating the device is bound to a vfio
> driver, e.g.:
>
> /sys/devices/pci0000\:6f/0000\:6f\:01.0/vfio-dev/vfio0
>
> It is also a preparatory step toward adding cdev for supporting future
> device-oriented uAPI.
>
> Add Documentation/ABI/testing/sysfs-devices-vfio-dev.
>
> Also take this chance to rename chardev 'vfio' to 'vfio-group' in
> /proc/devices.
>
> Suggested-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx>
> Signed-off-by: Kevin Tian <kevin.tian@xxxxxxxxx>
> Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> ---
>  .../ABI/testing/sysfs-devices-vfio-dev        |  8 +++
>  drivers/vfio/vfio_main.c                      | 67 +++++++++++++++----
>  include/linux/vfio.h                          |  6 +-
>  3 files changed, 66 insertions(+), 15 deletions(-)
>  create mode 100644 Documentation/ABI/testing/sysfs-devices-vfio-dev
>
> diff --git a/Documentation/ABI/testing/sysfs-devices-vfio-dev b/Documentation/ABI/testing/sysfs-devices-vfio-dev
> new file mode 100644
> index 000000000000..e21424fd9666
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-devices-vfio-dev
> @@ -0,0 +1,8 @@
> +What:		 /sys/.../<device>/vfio-dev/vfioX/
> +Date:		 September 2022
> +Contact:	 Yi Liu <yi.l.liu@xxxxxxxxx>
> +Description:
> +		 This directory is created when the device is bound to a
> +		 vfio driver. The layout under this directory matches what
> +		 exists for a standard 'struct device'. 'X' is a unique
> +		 index marking this device in vfio.
> diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
> index bfa675d314ab..141f55c3faf5 100644
> --- a/drivers/vfio/vfio_main.c
> +++ b/drivers/vfio/vfio_main.c
> @@ -46,6 +46,8 @@ static struct vfio {
>  	struct mutex			group_lock; /* locks group_list */
>  	struct ida			group_ida;
>  	dev_t				group_devt;
> +	struct class			*device_class;
> +	struct ida			device_ida;
>  } vfio;
>  
>  struct vfio_iommu_driver {
> @@ -483,12 +485,13 @@ static struct vfio_device *vfio_group_get_device(struct vfio_group *group,
>   * VFIO driver API
>   */
>  /* Release helper called by vfio_put_device() */
> -void vfio_device_release(struct kref *kref)
> +static void vfio_device_release(struct device *dev)
>  {
>  	struct vfio_device *device =
> -			container_of(kref, struct vfio_device, kref);
> +			container_of(dev, struct vfio_device, device);
>  
>  	vfio_release_device_set(device);
> +	ida_free(&vfio.device_ida, device->index);
>  
>  	/*
>  	 * kvfree() cannot be done here due to a life cycle mess in
> @@ -498,7 +501,6 @@ void vfio_device_release(struct kref *kref)
>  	 */
>  	device->ops->release(device);
>  }
> -EXPORT_SYMBOL_GPL(vfio_device_release);
>  
>  /*
>   * Alloc and initialize vfio_device so it can be registered to vfio
> @@ -546,6 +548,13 @@ int vfio_init_device(struct vfio_device *device, struct device *dev,
>  {
>  	int ret;
>  
> +	ret = ida_alloc_max(&vfio.device_ida, MINORMASK, GFP_KERNEL);
> +	if (ret < 0) {
> +		dev_dbg(dev, "Error to alloc index\n");
> +		return ret;
> +	}
> +
> +	device->index = ret;
>  	init_completion(&device->comp);
>  	device->dev = dev;
>  	device->ops = ops;
> @@ -556,11 +565,15 @@ int vfio_init_device(struct vfio_device *device, struct device *dev,
>  			goto out_uninit;
>  	}
>  
> -	kref_init(&device->kref);
> +	device_initialize(&device->device);
> +	device->device.release = vfio_device_release;
> +	device->device.class = vfio.device_class;
> +	device->device.parent = device->dev;
>  	return 0;
>  
>  out_uninit:
>  	vfio_release_device_set(device);
> +	ida_free(&vfio.device_ida, device->index);
>  	return ret;
>  }
>  EXPORT_SYMBOL_GPL(vfio_init_device);
> @@ -657,6 +670,7 @@ static int __vfio_register_dev(struct vfio_device *device,
>  		struct vfio_group *group)
>  {
>  	struct vfio_device *existing_device;
> +	int ret;
>  
>  	if (IS_ERR(group))
>  		return PTR_ERR(group);
> @@ -673,16 +687,21 @@ static int __vfio_register_dev(struct vfio_device *device,
>  		dev_WARN(device->dev, "Device already exists on group %d\n",
>  			 iommu_group_id(group->iommu_group));
>  		vfio_device_put_registration(existing_device);
> -		if (group->type == VFIO_NO_IOMMU ||
> -		    group->type == VFIO_EMULATED_IOMMU)
> -			iommu_group_remove_device(device->dev);
> -		vfio_group_put(group);
> -		return -EBUSY;
> +		ret = -EBUSY;
> +		goto err_out;
>  	}
>  
>  	/* Our reference on group is moved to the device */
>  	device->group = group;
>  
> +	ret = dev_set_name(&device->device, "vfio%d", device->index);
> +	if (ret)
> +		goto err_out;
> +
> +	ret = device_add(&device->device);
> +	if (ret)
> +		goto err_out;
> +
>  	/* Refcounting can't start until the driver calls register */
>  	refcount_set(&device->refcount, 1);
>  
> @@ -692,6 +711,12 @@ static int __vfio_register_dev(struct vfio_device *device,
>  	mutex_unlock(&group->device_lock);
>  
>  	return 0;
> +err_out:
> +	if (group->type == VFIO_NO_IOMMU ||
> +	    group->type == VFIO_EMULATED_IOMMU)
> +		iommu_group_remove_device(device->dev);
> +	vfio_group_put(group);
> +	return ret;
>  }
>  
>  int vfio_register_group_dev(struct vfio_device *device)
> @@ -779,6 +804,9 @@ void vfio_unregister_group_dev(struct vfio_device *device)
>  	group->dev_counter--;
>  	mutex_unlock(&group->device_lock);
>  
> +	/* Balances device_add in register path */
> +	device_del(&device->device);
> +
>  	if (group->type == VFIO_NO_IOMMU || group->type == VFIO_EMULATED_IOMMU)
>  		iommu_group_remove_device(device->dev);
>  
> @@ -2145,6 +2173,7 @@ static int __init vfio_init(void)
>  	int ret;
>  
>  	ida_init(&vfio.group_ida);
> +	ida_init(&vfio.device_ida);
>  	mutex_init(&vfio.group_lock);
>  	mutex_init(&vfio.iommu_drivers_lock);
>  	INIT_LIST_HEAD(&vfio.group_list);
> @@ -2160,12 +2189,20 @@ static int __init vfio_init(void)
>  	vfio.class = class_create(THIS_MODULE, "vfio");
>  	if (IS_ERR(vfio.class)) {
>  		ret = PTR_ERR(vfio.class);
> -		goto err_class;
> +		goto err_group_class;
>  	}
>  
>  	vfio.class->devnode = vfio_devnode;
>  
> -	ret = alloc_chrdev_region(&vfio.group_devt, 0, MINORMASK + 1, "vfio");
> +	/* /sys/class/vfio-dev/vfioX */
> +	vfio.device_class = class_create(THIS_MODULE, "vfio-dev");
> +	if (IS_ERR(vfio.device_class)) {
> +		ret = PTR_ERR(vfio.device_class);
> +		goto err_dev_class;
> +	}
> +
> +	ret = alloc_chrdev_region(&vfio.group_devt, 0, MINORMASK + 1,
> +				  "vfio-group");
>  	if (ret)
>  		goto err_alloc_chrdev;
>  
> @@ -2181,9 +2218,12 @@ static int __init vfio_init(void)
>  err_driver_register:
>  	unregister_chrdev_region(vfio.group_devt, MINORMASK + 1);
>  err_alloc_chrdev:
> +	class_destroy(vfio.device_class);
> +	vfio.device_class = NULL;
> +err_dev_class:
>  	class_destroy(vfio.class);
>  	vfio.class = NULL;
> -err_class:
> +err_group_class:
>  	misc_deregister(&vfio_dev);
>  	return ret;
>  }
> @@ -2195,8 +2235,11 @@ static void __exit vfio_cleanup(void)
>  #ifdef CONFIG_VFIO_NOIOMMU
>  	vfio_unregister_iommu_driver(&vfio_noiommu_ops);
>  #endif
> +	ida_destroy(&vfio.device_ida);
>  	ida_destroy(&vfio.group_ida);
>  	unregister_chrdev_region(vfio.group_devt, MINORMASK + 1);
> +	class_destroy(vfio.device_class);
> +	vfio.device_class = NULL;
>  	class_destroy(vfio.class);
>  	vfio.class = NULL;
>  	misc_deregister(&vfio_dev);
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index f03447c8774d..5c13f74da1bb 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -45,7 +45,8 @@ struct vfio_device {
>  	struct kvm *kvm;
>  
>  	/* Members below here are private, not for driver use */
> -	struct kref kref;	/* object life cycle */
> +	unsigned int index;
> +	struct device device;	/* device.kref covers object life circle */
>  	refcount_t refcount;	/* user count on registered device*/
>  	unsigned int open_count;
>  	struct completion comp;
I am not totally clear about remaining 'struct device *dev;' in
vfio_device struct. I see it used in some places. Is it supposed to
disappear at some point?
> @@ -154,10 +155,9 @@ struct vfio_device *_vfio_alloc_device(size_t size, struct device *dev,
>  int vfio_init_device(struct vfio_device *device, struct device *dev,
>  		     const struct vfio_device_ops *ops);
>  void vfio_free_device(struct vfio_device *device);
> -void vfio_device_release(struct kref *kref);
>  static inline void vfio_put_device(struct vfio_device *device)
>  {
> -	kref_put(&device->kref, vfio_device_release);
> +	put_device(&device->device);
>  }
>  
>  int vfio_register_group_dev(struct vfio_device *device);

Thanks

Eric