Re: [PATCH v4 10/17] iommufd: Support IOMMU_HWPT_ALLOC allocation with user data

[Nicolin Chen]

On Mon, Oct 16, 2023 at 08:59:07AM -0300, Jason Gunthorpe wrote:
> On Mon, Oct 16, 2023 at 03:03:04PM +0800, Yi Liu wrote:
> > Current nesting series actually extends HWPT_ALLOC ioctl to accept user
> > data for allocating domain with vendor specific data. Nested translation
> > happens to be the usage of it. But nesting requires invalidation. If we
> > want to do further split, then this new series would be just "extending
> > HWPT_ALLOC to accept vendor specific data from userspace". But it will
> > lack of a user if nesting is separated. Is this acceptable? @Jason
> 
> I'd still like to include the nesting allocation and attach parts
> though, even if they are not usable without invalidation ..

This is the latest series that I reworked (in bottom-up order):
 iommu: Add a pair of helper to copy struct iommu_user_data{_array}
 iommufd: Add IOMMU_HWPT_INVALIDATE
 iommufd: Add a nested HW pagetable object
 iommufd: Share iommufd_hwpt_alloc with IOMMUFD_OBJ_HWPT_NESTED
 iommufd: Derive iommufd_hwpt_paging from iommufd_hw_pagetable
 iommufd: Rename IOMMUFD_OBJ_HW_PAGETABLE to IOMMUFD_OBJ_HWPT_PAGING
 iommufd/device: Add helpers to enforce/remove device reserved regions
 iommu: Add IOMMU_DOMAIN_NESTED and cache_invalidate_user op
 iommu: Pass in parent domain with user_data to domain_alloc_user op

Perhaps we can have a preparatory series to merge first:
 iommufd: Share iommufd_hwpt_alloc with IOMMUFD_OBJ_HWPT_NESTED
 iommufd: Derive iommufd_hwpt_paging from iommufd_hw_pagetable
 iommufd: Rename IOMMUFD_OBJ_HW_PAGETABLE to IOMMUFD_OBJ_HWPT_PAGING
 iommufd/device: Add helpers to enforce/remove device reserved regions

Then next cycle would be basically 4 patches + selftests:
 iommufd: Add IOMMU_HWPT_INVALIDATE
 iommufd: Add a nested HW pagetable object
 iommu: Add IOMMU_DOMAIN_NESTED and cache_invalidate_user op
 iommu: Pass in parent domain with user_data to domain_alloc_user op

The preparatory series doesn't involve functional changes yet have
a good amount of pieces to simplify the "nested HW pagetable" that
is basically nested_alloc/abort/destroy.

> > BTW. Do we still have unsolved issue on the invalidation path?
> 
> I'm not sure, there were so many different versions of it we need to
> go back over it and check the dirver implementations again

Only this v4 has the latest array-based invalidation design. And
it should be straightforward for drivers to define entry/request
structures. It might be a bit rush to review/finalize it at the
stage of rc6 though.

Thanks
Nic