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

Yi Liu
2022-09-08T09:17:10Z

On 2022/9/8 17:06, Eric Auger wrote:
> 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?

no, Eric. *dev will not disappear, it stores the dev pointet passed in by
caller of vfio_init_device().

>> @@ -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
>

--
Regards,
Yi Liu