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

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