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

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