RE: [PATCH v2 06/11] iommufd: IOMMU_HWPT_ALLOC allocation with user data

From: Yi Liu yi.l.liu@intel.com Sent: Thursday, May 11, 2023 10:39 PM

• if (cmd->hwpt_type != IOMMU_HWPT_TYPE_DEFAULT) {

• if (!ops->domain_alloc_user_data_len) {
  

• 	rc = -EOPNOTSUPP;
  

• 	goto out_put_idev;
  

• }
  

• klen = ops->domain_alloc_user_data_len(cmd->hwpt_type);
  

• if (WARN_ON(klen < 0)) {
  

• 	rc = -EINVAL;
  

• 	goto out_put_pt;
  

• }
  

• }

What about passing the user pointer to the iommu driver which then does the copy so we don't need an extra @data_len() callback for every driver?

• switch (pt_obj->type) {
• case IOMMUFD_OBJ_IOAS:

• ioas = container_of(pt_obj, struct iommufd_ioas, obj);
  

• break;
  

this should fail if parent is specified.

• case IOMMUFD_OBJ_HW_PAGETABLE:

• /* pt_id points HWPT only when hwpt_type
  

is !IOMMU_HWPT_TYPE_DEFAULT */

• if (cmd->hwpt_type == IOMMU_HWPT_TYPE_DEFAULT) {
  

• 	rc = -EINVAL;
  

• 	goto out_put_pt;
  

• }
  

• parent = container_of(pt_obj, struct iommufd_hw_pagetable,
  

obj);

• /*
  

•  * Cannot allocate user-managed hwpt linking to
  

auto_created

•  * hwpt. If the parent hwpt is already a user-managed hwpt,
  

•  * don't allocate another user-managed hwpt linking to it.
  

•  */
  

• if (parent->auto_domain || parent->parent) {
  

• 	rc = -EINVAL;
  

• 	goto out_put_pt;
  

• }
  

• ioas = parent->ioas;
  

for nesting why is ioas required? In concept we can just pass NULL ioas to iommufd_hw_pagetable_alloc() for this hwpt. If within that function there is a need to toggle ioas for the parent it can always retrieve it from the parent hwpt.