Re: [PATCH v2 01/11] iommu: Add new iommu op to create domains owned by userspace

[Nicolin Chen <nicolinc@nvidia.com>]

On Fri, May 19, 2023 at 08:47:45AM +0000, Tian, Kevin wrote:
> > From: Liu, Yi L <yi.l.liu@intel.com>
> > Sent: Thursday, May 11, 2023 10:39 PM
> > @@ -229,6 +238,15 @@ struct iommu_iotlb_gather {
> >   *           after use. Return the data buffer if success, or ERR_PTR on
> >   *           failure.
> >   * @domain_alloc: allocate iommu domain
> > + * @domain_alloc_user: allocate user iommu domain
> > + * @domain_alloc_user_data_len: return the required length of the user
> > data
> > + *                              to allocate a specific type user iommu domain.
> > + *                              @hwpt_type is defined as enum iommu_hwpt_type
> > + *                              in include/uapi/linux/iommufd.h. The returned
> > + *                              length is the corresponding sizeof driver data
> > + *                              structures in include/uapi/linux/iommufd.h.
> > + *                              -EOPNOTSUPP would be returned if the input
> > + *                              @hwpt_type is not supported by the driver.
> 
> Can this be merged with earlier @hw_info callback? That will already
> report a list of supported hwpt types. is there a problem to further
> describe the data length for each type in that interface?

Yi and I had a last minute talk before he sent this version
actually... This version of hw_info no longer reports a list
of supported hwpt types. We previously did that in a bitmap,
but we found that a bitmap will not be sufficient eventually
if there are more than 64 hwpt_types.

And this domain_alloc_user_data_len might not be necessary,
because in this version the IOMMUFD core doesn't really care
about the actual data_len since it copies the data into the
ucmd_buffer, i.e. we would probably only need a bool op like
"hwpt_type_is_supported".

Thanks
Nic