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

Eric Auger
2022-09-08T09:07:17Z

Hi Kevin,

On 9/1/22 16:37, Kevin Tian wrote:
> From: Yi Liu <yi.l.liu@intel.com>
>
> 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@nvidia.com>
> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
> Signed-off-by: Kevin Tian <kevin.tian@intel.com>
> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
> ---
> .../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@intel.com>
> +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