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

Nicolin Chen
2023-05-19T19:10:14Z

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