[1/6] iommu: Add new iommu op to create domains owned by userspace

Introduce a new iommu_domain op to create domains owned by userspace,
e.g. through IOMMUFD. These domains have a few different properties
compares to kernel owned domains:

 - They may be UNMANAGED domains, but created with special parameters.
   For instance aperture size changes/number of levels, different
   IOPTE formats, or other things necessary to make a vIOMMU work

 - We have to track all the memory allocations with GFP_KERNEL_ACCOUNT
   to make the cgroup sandbox stronger

 - Device-specialty domains, such as NESTED domains can be created by
   IOMMUFD.

The new op clearly says the domain is being created by IOMMUFD, that
the domain is intended for userspace use, and it provides a way to pass
user flags or a driver specific uAPI structure to customize the created
domain to exactly what the vIOMMU userspace driver requires.

iommu drivers that cannot support VFIO/IOMMUFD should not support this
op. This includes any driver that cannot provide a fully functional
UNMANAGED domain.

This new op for now is only supposed to be used by IOMMUFD, hence no
wrapper for it. IOMMUFD would call the callback directly. As for domain
free, IOMMUFD would use iommu_domain_free().

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Co-developed-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
---
 include/linux/iommu.h        |  8 ++++++++
 include/uapi/linux/iommufd.h | 12 +++++++++++-
 2 files changed, 19 insertions(+), 1 deletion(-)

> From: Liu, Yi L <yi.l.liu@intel.com>
> Sent: Tuesday, September 19, 2023 5:25 PM
> 
> @@ -235,6 +235,13 @@ struct iommu_iotlb_gather {
>   *           use. The information type is one of enum iommu_hw_info_type
> defined
>   *           in include/uapi/linux/iommufd.h.
>   * @domain_alloc: allocate iommu domain

Given now we have two @alloc ops it'd be clearer to also update the
comment here so the explanation for @domain_alloc_user() is easier
to be understood, e.g.:

@domain_alloc: allocate and return an iommu domain if success. Otherwise
               NULL is returned. The domain is not fully initialized until
               the caller iommu_domain_alloc() returns.

> + * @domain_alloc_user: Allocate an iommu domain corresponding to the
> input
> + *                     parameters like flags defined as enum
> iommufd_ioas_map_flags
> + *                     in include/uapi/linux/iommufd.h. Different from the

"to the input parameters as defined in include/uapi/linux/iommufd.h".

> + *                     domain_alloc op, it requires iommu driver to fully
> + *                     initialize a new domain including the generic iommu_domain

"Unlike @domain_alloc, it is called only by iommufd and must fully initialize
the new domain before return".

*domain* here already refers to the generic iommu_domain struct.

On 2023/9/26 13:28, Tian, Kevin wrote:
>> From: Liu, Yi L <yi.l.liu@intel.com>
>> Sent: Tuesday, September 19, 2023 5:25 PM
>>
>> @@ -235,6 +235,13 @@ struct iommu_iotlb_gather {
>>    *           use. The information type is one of enum iommu_hw_info_type
>> defined
>>    *           in include/uapi/linux/iommufd.h.
>>    * @domain_alloc: allocate iommu domain
> 
> Given now we have two @alloc ops it'd be clearer to also update the
> comment here so the explanation for @domain_alloc_user() is easier
> to be understood, e.g.:
> 
> @domain_alloc: allocate and return an iommu domain if success. Otherwise
>                 NULL is returned. The domain is not fully initialized until
>                 the caller iommu_domain_alloc() returns.
> 
>> + * @domain_alloc_user: Allocate an iommu domain corresponding to the
>> input
>> + *                     parameters like flags defined as enum
>> iommufd_ioas_map_flags
>> + *                     in include/uapi/linux/iommufd.h. Different from the
> 
> "to the input parameters as defined in include/uapi/linux/iommufd.h".
> 
>> + *                     domain_alloc op, it requires iommu driver to fully
>> + *                     initialize a new domain including the generic iommu_domain
> 
> "Unlike @domain_alloc, it is called only by iommufd and must fully initialize
> the new domain before return".
> 
> *domain* here already refers to the generic iommu_domain struct.
> 

above comment well received.