RE: [PATCH v2 1/6] iommu: Add new iommu op to create domains owned by userspace

[Tian, Kevin]

> From: Liu, Yi L <yi.l.liu@xxxxxxxxx>
> Sent: Thursday, September 28, 2023 3:15 PM
> 
> 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@xxxxxxxxxx>
> Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> Co-developed-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
> Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
> Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx>

Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>