Re: [PATCH v2 04/11] iommufd: Pass parent hwpt and user_data to iommufd_hw_pagetable_alloc()

On Fri, May 19, 2023 at 09:06:20AM +0000, Tian, Kevin wrote:

...

@@ -73,14 +77,22 @@ int iommufd_hw_pagetable_enforce_cc(struct iommufd_hw_pagetable *hwpt) */ struct iommufd_hw_pagetable * iommufd_hw_pagetable_alloc(struct iommufd_ctx *ictx, struct iommufd_ioas *ioas,

•                    struct iommufd_device *idev, bool
  

immediate_attach)

•                    struct iommufd_device *idev,
  

•                    struct iommufd_hw_pagetable *parent,
  

•                    union iommu_domain_user_data *user_data,
  

•                    bool immediate_attach)
  

{ const struct iommu_ops *ops = dev_iommu_ops(idev->dev);

• struct iommu_domain *parent_domain = NULL;
  struct iommufd_hw_pagetable *hwpt;
  

• bool type_unmanaged, type_nested;
  int rc;
  
  lockdep_assert_held(&ioas->mutex);
  
  

• if ((user_data || parent) && !ops->domain_alloc_user)
  

•         return ERR_PTR(-EOPNOTSUPP);
  

Do we allow specifying parent w/o user_data?

I don't think so. Perhaps we should do a double check:

+ if (!!user_data ^ !!parent) + return ERR_PTR(-EINVAL); + if (user_data && !ops->domain_alloc_user) + return ERR_PTR(-EOPNOTSUPP);

...

@@ -99,6 +117,15 @@ iommufd_hw_pagetable_alloc(struct iommufd_ctx *ictx, struct iommufd_ioas *ioas, goto out_abort; }

• /* It must be either NESTED or UNMANAGED, depending on
  

parent_domain */

•   type_nested = hwpt->domain->type == IOMMU_DOMAIN_NESTED;
  

•   type_unmanaged = hwpt->domain->type ==
  

IOMMU_DOMAIN_UNMANAGED;

no need of one-time used variables. Just put the conditions directly in WARN_ON.

It is to improve the readability. Otherwise, we'd have:

if (WARN_ON((parent_domain && hwpt->domain->type != IOMMU_DOMAIN_NESTED) || (!parent_domain && hwpt->domain->type != IOMMU_DOMAIN_UNMANAGED)))

...

•   if (WARN_ON((parent_domain && !type_nested) ||
  

•               (!parent_domain && !type_unmanaged))) {
  

•         rc = -EINVAL;
  

•         goto out_abort;
  

• }
  

probably just WARN_ON_ONCE() to mark that driver has problem?

Yea. I think we could do that.

Thanks Nic