Re: [PATCH RFCv2 05/13] iommu: Turn fault_data to iommufd private pointer

[Eric Auger <eric.auger@redhat.com>]

On 1/11/25 4:32 AM, Nicolin Chen wrote:
> A "fault_data" was added exclusively for the iommufd_fault_iopf_handler()
> used by IOPF/PRI use cases, along with the attach_handle. Now, the iommufd
> version of sw_msi function will resue the attach_handle and fault_data for
reuse
> a non-fault case.
>
> Rename "fault_data" to "iommufd_hwpt" so as not to confine it to a "fault"
> case. Move it into a union to be the iommufd private pointer. A following
> patch will move the iova_cookie to the union for dma-iommu too, after the
> iommufd_sw_msi implementation is added.
>
> Since we have two unions now, add some simple comments for readability.
>
> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
> ---
>  include/linux/iommu.h                | 6 ++++--
>  drivers/iommu/iommufd/fault.c        | 2 +-
>  drivers/iommu/iommufd/hw_pagetable.c | 2 +-
>  3 files changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 423fdfa6b3bb..b6526d734f30 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -224,8 +224,10 @@ struct iommu_domain {
>  		      phys_addr_t msi_addr);
>  #endif
>  
> -	void *fault_data;
> -	union {
> +	union { /* Pointer usable by owner of the domain */
> +		struct iommufd_hw_pagetable *iommufd_hwpt; /* iommufd */
> +	};
> +	union { /* Fault handler */
>  		struct {
>  			iommu_fault_handler_t handler;
>  			void *handler_token;
> diff --git a/drivers/iommu/iommufd/fault.c b/drivers/iommu/iommufd/fault.c
> index 1fe804e28a86..06aa83a75e94 100644
> --- a/drivers/iommu/iommufd/fault.c
> +++ b/drivers/iommu/iommufd/fault.c
> @@ -431,7 +431,7 @@ int iommufd_fault_iopf_handler(struct iopf_group *group)
>  	struct iommufd_hw_pagetable *hwpt;
>  	struct iommufd_fault *fault;
>  
> -	hwpt = group->attach_handle->domain->fault_data;
> +	hwpt = group->attach_handle->domain->iommufd_hwpt;
>  	fault = hwpt->fault;
>  
>  	mutex_lock(&fault->mutex);
> diff --git a/drivers/iommu/iommufd/hw_pagetable.c b/drivers/iommu/iommufd/hw_pagetable.c
> index ce03c3804651..f7c0d7b214b6 100644
> --- a/drivers/iommu/iommufd/hw_pagetable.c
> +++ b/drivers/iommu/iommufd/hw_pagetable.c
> @@ -402,10 +402,10 @@ int iommufd_hwpt_alloc(struct iommufd_ucmd *ucmd)
>  		}
>  		hwpt->fault = fault;
>  		hwpt->domain->iopf_handler = iommufd_fault_iopf_handler;
> -		hwpt->domain->fault_data = hwpt;
>  		refcount_inc(&fault->obj.users);
>  		iommufd_put_object(ucmd->ictx, &fault->obj);
>  	}
> +	hwpt->domain->iommufd_hwpt = hwpt;
don't we want to reset this somewhere on release path?

Eric
>  
>  	cmd->out_hwpt_id = hwpt->obj.id;
>  	rc = iommufd_ucmd_respond(ucmd, sizeof(*cmd));