Re: [PATCH 1/2] iommu: Store either domain or handle in group->pasid_array

[Jason Gunthorpe <jgg@nvidia.com>]

On Sun, Jan 19, 2025 at 07:08:39PM -0800, Yi Liu wrote:
> iommu_attach_device_pasid() only stores handle to group->pasid_array
> when there is a valid handle input. However, it makes the
> iommu_attach_device_pasid() unable to detect if the pasid has been
> attached or not. To be complete, let the iommu_attach_device_pasid()
> store the domain to group->pasid_array if no valid handle.
> 
> Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
> ---
>  drivers/iommu/iommu.c | 23 +++++++++++++++++------
>  1 file changed, 17 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 28ffd836592b..278c4eb8f225 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -45,6 +45,8 @@ static unsigned int iommu_def_domain_type __read_mostly;
>  static bool iommu_dma_strict __read_mostly = IS_ENABLED(CONFIG_IOMMU_DEFAULT_DMA_STRICT);
>  static u32 iommu_cmd_line __read_mostly;
>  
> +enum { IOMMU_PASID_ARRAY_DOMAIN, IOMMU_PASID_ARRAY_HANDLE };

Since xarray says:

 * @tag: Tag value (0, 1 or 3).

I would initialize those enums and add a small comment

/* tags used with xa_tag_pointer() */
enum { IOMMU_PASID_ARRAY_DOMAIN = 0, IOMMU_PASID_ARRAY_HANDLE = 1 };

> @@ -3397,10 +3400,14 @@ int iommu_attach_device_pasid(struct iommu_domain *domain,
>  		}
>  	}
>  
> -	if (handle)
> +	if (handle) {
>  		handle->domain = domain;
> +		xa_entry = xa_tag_pointer(handle, IOMMU_PASID_ARRAY_HANDLE);
> +	} else {
> +		xa_entry = xa_tag_pointer(domain, IOMMU_PASID_ARRAY_DOMAIN);
> +	}

What about iommu_attach_group_handle() ?

	mutex_lock(&group->mutex);
	ret = xa_insert(&group->pasid_array, IOMMU_NO_PASID, handle, GFP_KERNEL);
	if (ret)

And iommu_replace_group_handle() ?

	curr = xa_store(&group->pasid_array, IOMMU_NO_PASID, handle, GFP_KERNEL);

I think it should be consistent and it should call xa_tag_poiner() too
(even though it implicitly always is since the domain is stored in the
group)??

Jason