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Date:   Thu, 8 Sep 2022 17:17:03 +0800
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Subject: Re: [PATCH v2 15/15] vfio: Add struct device to vfio_device
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To:     <eric.auger@redhat.com>, Kevin Tian <kevin.tian@intel.com>,
        Zhenyu Wang <zhenyuw@linux.intel.com>,
        Zhi Wang <zhi.a.wang@intel.com>,
        Jani Nikula <jani.nikula@linux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Eric Farman <farman@linux.ibm.com>,
        Matthew Rosato <mjrosato@linux.ibm.com>,
        Halil Pasic <pasic@linux.ibm.com>,
        Vineeth Vijayan <vneethv@linux.ibm.com>,
        "Peter Oberparleiter" <oberpar@linux.ibm.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Alexander Gordeev <agordeev@linux.ibm.com>,
        Christian Borntraeger <borntraeger@linux.ibm.com>,
        Sven Schnelle <svens@linux.ibm.com>,
        Tony Krowiak <akrowiak@linux.ibm.com>,
        Jason Herne <jjherne@linux.ibm.com>,
        Harald Freudenberger <freude@linux.ibm.com>,
        Diana Craciun <diana.craciun@oss.nxp.com>,
        "Alex Williamson" <alex.williamson@redhat.com>,
        Cornelia Huck <cohuck@redhat.com>,
        Longfang Liu <liulongfang@huawei.com>,
        Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        Yishai Hadas <yishaih@nvidia.com>,
        Kirti Wankhede <kwankhede@nvidia.com>,
        Leon Romanovsky <leon@kernel.org>,
        Abhishek Sahu <abhsahu@nvidia.com>,
        <intel-gvt-dev@lists.freedesktop.org>,
        <intel-gfx@lists.freedesktop.org>,
        <dri-devel@lists.freedesktop.org>, <linux-kernel@vger.kernel.org>,
        <linux-s390@vger.kernel.org>, <kvm@vger.kernel.org>
References: <20220901143747.32858-1-kevin.tian@intel.com>
 <20220901143747.32858-16-kevin.tian@intel.com>
 <50d82b01-86a3-e6a3-06f7-7f98e60131eb@redhat.com>
From:   Yi Liu <yi.l.liu@intel.com>
In-Reply-To: <50d82b01-86a3-e6a3-06f7-7f98e60131eb@redhat.com>
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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