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

Kevin Tian
2022-09-01T07:23:11Z

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;
@@ -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);
--
2.21.3