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

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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@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?

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



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