Re: [PATCH v3 03/12] iommu: Add new flag to explictly request PASID capable domain

[Jason Gunthorpe <jgg@ziepe.ca>]

On Fri, Oct 18, 2024 at 11:43:02AM +0800, Baolu Lu wrote:
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 9f6b0780f2ef..d7546ab18e18 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -3539,12 +3539,16 @@ intel_iommu_domain_alloc_user(struct device *dev,
> u32 flags,
>         }
> 
>         if (flags &
> -           (~(IOMMU_HWPT_ALLOC_NEST_PARENT |
> IOMMU_HWPT_ALLOC_DIRTY_TRACKING)))
> +           (~(IOMMU_HWPT_ALLOC_NEST_PARENT |
> +              IOMMU_HWPT_ALLOC_DIRTY_TRACKING) |
> +              IOMMU_HWPT_ALLOC_PASID))
>                 return ERR_PTR(-EOPNOTSUPP);
>         if (nested_parent && !nested_supported(iommu))
>                 return ERR_PTR(-EOPNOTSUPP);
>         if (user_data || (dirty_tracking && !ssads_supported(iommu)))
>                 return ERR_PTR(-EOPNOTSUPP);
> +       if ((flags & IOMMU_HWPT_ALLOC_PASID) && !pasid_supported(iommu))
> +               return ERR_PTR(-EOPNOTSUPP);

I think the decision here should only be about supported domain
type. Like on AMD if the iommu instance doesn't support v2 then it
should fail.

If there is some other thing that says the instance supports pasid,
that should be checked during attach time only.

IIRC intel can use either page table format for pasid, so it probably
doesn't need to do anything here?

Jason