Re: [PATCH v7 19/28] iommu: Allow an input type in hw_info op

[Pranjal Shrivastava <praan@google.com>]

On Thu, Jun 26, 2025 at 12:34:50PM -0700, Nicolin Chen wrote:
> The hw_info uAPI will support a bidirectional data_type field that can be
> used as an input field for user space to request for a specific info data.
> 
> To prepare for the uAPI update, change the iommu layer first:
>  - Add a new IOMMU_HW_INFO_TYPE_DEFAULT as an input, for which driver can
>    output its only (or firstly) supported type
>  - Update the kdoc accordingly
>  - Roll out the type validation in the existing drivers
> 
> Reviewed-by: Kevin Tian <kevin.tian@intel.com>
> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
> Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
> ---
>  include/linux/iommu.h                               | 3 ++-
>  include/uapi/linux/iommufd.h                        | 4 +++-
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c | 4 ++++
>  drivers/iommu/intel/iommu.c                         | 4 ++++
>  drivers/iommu/iommufd/device.c                      | 3 +++
>  drivers/iommu/iommufd/selftest.c                    | 4 ++++
>  6 files changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index e06a0fbe4bc7..e8b59ef54e48 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -603,7 +603,8 @@ __iommu_copy_struct_to_user(const struct iommu_user_data *dst_data,
>   * @capable: check capability
>   * @hw_info: report iommu hardware information. The data buffer returned by this
>   *           op is allocated in the iommu driver and freed by the caller after
> - *           use.
> + *           use. @type can input a requested type and output a supported type.
> + *           Driver should reject an unsupported data @type input
>   * @domain_alloc: Do not use in new drivers
>   * @domain_alloc_identity: allocate an IDENTITY domain. Drivers should prefer to
>   *                         use identity_domain instead. This should only be used
> diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
> index f091ea072c5f..6ad361ff9b06 100644
> --- a/include/uapi/linux/iommufd.h
> +++ b/include/uapi/linux/iommufd.h
> @@ -593,13 +593,15 @@ struct iommu_hw_info_arm_smmuv3 {
>  
>  /**
>   * enum iommu_hw_info_type - IOMMU Hardware Info Types
> - * @IOMMU_HW_INFO_TYPE_NONE: Used by the drivers that do not report hardware
> + * @IOMMU_HW_INFO_TYPE_NONE: Output by the drivers that do not report hardware
>   *                           info
> + * @IOMMU_HW_INFO_TYPE_DEFAULT: Input to request for a default type
>   * @IOMMU_HW_INFO_TYPE_INTEL_VTD: Intel VT-d iommu info type
>   * @IOMMU_HW_INFO_TYPE_ARM_SMMUV3: ARM SMMUv3 iommu info type
>   */
>  enum iommu_hw_info_type {
>  	IOMMU_HW_INFO_TYPE_NONE = 0,
> +	IOMMU_HW_INFO_TYPE_DEFAULT = 0,
>  	IOMMU_HW_INFO_TYPE_INTEL_VTD = 1,
>  	IOMMU_HW_INFO_TYPE_ARM_SMMUV3 = 2,
>  };
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
> index 170d69162848..eb9fe1f6311a 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
> @@ -15,6 +15,10 @@ void *arm_smmu_hw_info(struct device *dev, u32 *length,
>  	u32 __iomem *base_idr;
>  	unsigned int i;
>  
> +	if (*type != IOMMU_HW_INFO_TYPE_DEFAULT &&
> +	    *type != IOMMU_HW_INFO_TYPE_ARM_SMMUV3)
> +		return ERR_PTR(-EOPNOTSUPP);
> +
>  	info = kzalloc(sizeof(*info), GFP_KERNEL);
>  	if (!info)
>  		return ERR_PTR(-ENOMEM);
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 850f1a6f548c..5f75faffca15 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -4098,6 +4098,10 @@ static void *intel_iommu_hw_info(struct device *dev, u32 *length,
>  	struct intel_iommu *iommu = info->iommu;
>  	struct iommu_hw_info_vtd *vtd;
>  
> +	if (*type != IOMMU_HW_INFO_TYPE_DEFAULT &&
> +	    *type != IOMMU_HW_INFO_TYPE_INTEL_VTD)
> +		return ERR_PTR(-EOPNOTSUPP);
> +
>  	vtd = kzalloc(sizeof(*vtd), GFP_KERNEL);
>  	if (!vtd)
>  		return ERR_PTR(-ENOMEM);
> diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
> index 8f078fda795a..64a51993e6a1 100644
> --- a/drivers/iommu/iommufd/device.c
> +++ b/drivers/iommu/iommufd/device.c
> @@ -1519,6 +1519,9 @@ int iommufd_get_hw_info(struct iommufd_ucmd *ucmd)
>  	    cmd->__reserved[2])
>  		return -EOPNOTSUPP;
>  
> +	/* Clear the type field since drivers don't support a random input */
> +	cmd->out_data_type = IOMMU_HW_INFO_TYPE_DEFAULT;
> +
>  	idev = iommufd_get_device(ucmd, cmd->dev_id);
>  	if (IS_ERR(idev))
>  		return PTR_ERR(idev);
> diff --git a/drivers/iommu/iommufd/selftest.c b/drivers/iommu/iommufd/selftest.c
> index 8b2c44b32530..a5dc36219a90 100644
> --- a/drivers/iommu/iommufd/selftest.c
> +++ b/drivers/iommu/iommufd/selftest.c
> @@ -310,6 +310,10 @@ static void *mock_domain_hw_info(struct device *dev, u32 *length,
>  {
>  	struct iommu_test_hw_info *info;
>  
> +	if (*type != IOMMU_HW_INFO_TYPE_DEFAULT &&
> +	    *type != IOMMU_HW_INFO_TYPE_SELFTEST)
> +		return ERR_PTR(-EOPNOTSUPP);
> +
>  	info = kzalloc(sizeof(*info), GFP_KERNEL);
>  	if (!info)
>  		return ERR_PTR(-ENOMEM);

Reviewed-by: Pranjal Shrivastava <praan@google.com>

> -- 
> 2.43.0
>