Re: [PATCH v2 02/19] iommufd/viommu: Add IOMMUFD_OBJ_VIOMMU and IOMMU_VIOMMU_ALLOC ioctl

[Baolu Lu]

On 2024/8/28 0:59, Nicolin Chen wrote:
> +int iommufd_viommu_alloc_ioctl(struct iommufd_ucmd *ucmd)
> +{
> +	struct iommu_viommu_alloc *cmd = ucmd->cmd;
> +	struct iommufd_hwpt_paging *hwpt_paging;
> +	struct iommufd_viommu *viommu;
> +	struct iommufd_device *idev;
> +	int rc;
> +
> +	if (cmd->flags)
> +		return -EOPNOTSUPP;
> +
> +	idev = iommufd_get_device(ucmd, cmd->dev_id);

Why does a device reference count is needed here? When is this reference
count released after the VIOMMU is allocated?

> +	if (IS_ERR(idev))
> +		return PTR_ERR(idev);
> +
> +	hwpt_paging = iommufd_get_hwpt_paging(ucmd, cmd->hwpt_id);
> +	if (IS_ERR(hwpt_paging)) {
> +		rc = PTR_ERR(hwpt_paging);
> +		goto out_put_idev;
> +	}
> +
> +	if (!hwpt_paging->nest_parent) {
> +		rc = -EINVAL;
> +		goto out_put_hwpt;
> +	}
> +
> +	if (cmd->type != IOMMU_VIOMMU_TYPE_DEFAULT) {
> +		rc = -EOPNOTSUPP;
> +		goto out_put_hwpt;
> +	}
> +
> +	viommu = iommufd_object_alloc(ucmd->ictx, viommu, IOMMUFD_OBJ_VIOMMU);
> +	if (IS_ERR(viommu)) {
> +		rc = PTR_ERR(viommu);
> +		goto out_put_hwpt;
> +	}
> +
> +	viommu->type = cmd->type;
> +	viommu->ictx = ucmd->ictx;
> +	viommu->hwpt = hwpt_paging;
> +
> +	refcount_inc(&viommu->hwpt->common.obj.users);
> +
> +	cmd->out_viommu_id = viommu->obj.id;
> +	rc = iommufd_ucmd_respond(ucmd, sizeof(*cmd));
> +	if (rc)
> +		goto out_abort;
> +	iommufd_object_finalize(ucmd->ictx, &viommu->obj);
> +	goto out_put_hwpt;
> +
> +out_abort:
> +	iommufd_object_abort_and_destroy(ucmd->ictx, &viommu->obj);
> +out_put_hwpt:
> +	iommufd_put_object(ucmd->ictx, &hwpt_paging->common.obj);
> +out_put_idev:
> +	iommufd_put_object(ucmd->ictx, &idev->obj);
> +	return rc;
> +}

Thanks,
baolu