Xu Yilun <yilun...@linux.intel.com> writes:
....
> +/**
> + * iommufd_device_tsm_bind - Move a device to TSM Bind state
> + * @idev: device to attach
> + * @vdev_id: Input a IOMMUFD_OBJ_VDEVICE
> + *
> + * This configures for device Confidential Computing(CC), and moves the
> device
> + * to the TSM Bind state. Once this completes the device is locked down
> (TDISP
> + * CONFIG_LOCKED or RUN), waiting for guest's attestation.
> + *
> + * This function is undone by calling iommufd_device_tsm_unbind().
> + */
> +int iommufd_device_tsm_bind(struct iommufd_device *idev, u32 vdevice_id)
> +{
> + struct iommufd_vdevice *vdev;
> + int rc;
> +
> + if (!dev_is_pci(idev->dev))
> + return -ENODEV;
> +
> + vdev = container_of(iommufd_get_object(idev->ictx, vdevice_id,
> IOMMUFD_OBJ_VDEVICE),
> + struct iommufd_vdevice, obj);
> + if (IS_ERR(vdev))
> + return PTR_ERR(vdev);
> +
> + if (vdev->dev != idev->dev) {
> + rc = -EINVAL;
> + goto out_put_vdev;
> + }
> +
> + mutex_lock(&idev->igroup->lock);
> + if (idev->vdev) {
> + rc = -EEXIST;
> + goto out_unlock;
> + }
> +
> + rc = iommufd_vdevice_tsm_bind(vdev);
> + if (rc)
> + goto out_unlock;
> +
> + idev->vdev = vdev;
> + refcount_inc(&vdev->obj.users);
> + mutex_unlock(&idev->igroup->lock);
> +
> + /*
> + * Pairs with iommufd_device_tsm_unbind() - catches caller bugs
> attempting
> + * to destroy a bound device.
> + */
> + refcount_inc(&idev->obj.users);
>
Do we really need this refcount_inc? As I understand it, the objects
aren't being pinned directly. Instead, the reference count seems to be
used more as a way to establish an object hierarchy, ensuring that
objects are freed in the correct order.
In vfio_pci_core_close_device(), you’re decrementing the reference, and
on the iommufd side, we’re covered because the VFIO bind operation takes
a file reference (fget)—so iommufd_fops_release() won’t be called
prematurely.
Wouldn’t it be simpler to skip the reference count increment altogether
and just call tsm_unbind in the virtual device’s destroy callback?
(iommufd_vdevice_destroy())
> + goto out_put_vdev;
> +
> +out_unlock:
> + mutex_unlock(&idev->igroup->lock);
> +out_put_vdev:
> + iommufd_put_object(idev->ictx, &vdev->obj);
> + return rc;
> +}
> +EXPORT_SYMBOL_NS_GPL(iommufd_device_tsm_bind, "IOMMUFD");
-aneesh
