Re: [PATCH v10 14/18] iommufd: Allow allocating PASID-compatible domain

[Jason Gunthorpe <jgg@nvidia.com>]

On Thu, Mar 20, 2025 at 06:47:40AM -0700, Yi Liu wrote:
> The underlying infrastructure has supported the PASID attach and related
> enforcement per the requirement of the IOMMU_HWPT_ALLOC_PASID flag. This
> extends iommufd to support PASID compatible domain requested by userspace.
> 
> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
> ---
> v9 -> v10: Dropped r-b tag as the uapi description for ALLOC_PASID is modified
> ---
>  drivers/iommu/iommufd/device.c       | 4 +++-
>  drivers/iommu/iommufd/hw_pagetable.c | 7 ++++---
>  include/uapi/linux/iommufd.h         | 3 +++
>  3 files changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
> index 54ffef9c17f7..f09dcddf777b 100644
> --- a/drivers/iommu/iommufd/device.c
> +++ b/drivers/iommu/iommufd/device.c
> @@ -973,7 +973,9 @@ iommufd_device_auto_get_domain(struct iommufd_device *idev, ioasid_t pasid,
>  	}
>  
>  	hwpt_paging = iommufd_hwpt_paging_alloc(idev->ictx, ioas, idev, pasid,
> -						0, immediate_attach, NULL);
> +						pasid != IOMMU_NO_PASID ?
> +						    IOMMU_HWPT_ALLOC_PASID : 0,
> +						immediate_attach, NULL);

I wonder if there is any point to this since userspace couldn't
actually just use autodomains and have something work since the RID
autodomain won't have PASID. I think if userspace wants to use pasid
it has to manually allocate the HWPT for the RID and then why not also
allocate for the PASID?

Anyhow, it doesn't matter much as it is so simple for autodomains..

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>

Jason