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

Tian, Kevin
2023-05-19T09:46:25Z

> 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.