Re: [PATCH v5 2/4] iommu: Add new iommu op to get iommu hardware information

["Liu, Jingqi" <jingqi.liu@intel.com>]

On 8/3/2023 10:31 PM, Yi Liu wrote:
> From: Lu Baolu <baolu.lu@linux.intel.com>
>
> Introduce a new iommu op to get the IOMMU hardware capabilities for
> iommufd. This information will be used by any vIOMMU driver which is
> owned by userspace.
>
> This op chooses to make the special parameters opaque to the core. This
> suits the current usage model where accessing any of the IOMMU device
> special parameters does require a userspace driver that matches the kernel
> driver. If a need for common parameters, implemented similarly by several
> drivers, arises then there's room in the design to grow a generic parameter
> set as well. No wrapper API is added as it is supposed to be used by
> iommufd only.
>
> Different IOMMU hardware would have different hardware information. So the
> information reported differs as well. To let the external user understand
> the difference. enum iommu_hw_info_type is defined. For the iommu drivers
> that are capable to report hardware information, it should have a unique
> iommu_hw_info_type and return to caller. For the driver doesn't report
> hardware information, caller just uses IOMMU_HW_INFO_TYPE_NONE if a type
> is required.
>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> Co-developed-by: Nicolin Chen <nicolinc@nvidia.com>
> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
> ---
>   include/linux/iommu.h        | 9 +++++++++
>   include/uapi/linux/iommufd.h | 8 ++++++++
>   2 files changed, 17 insertions(+)
>
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index e0245aa82b75..f2d6a3989713 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -228,6 +228,14 @@ struct iommu_iotlb_gather {
>   /**
>    * struct iommu_ops - iommu ops and capabilities
>    * @capable: check capability
> + * @hw_info: IOMMU hardware information. The type of the returned data is
> + *           marked by the output type of this op. Type is one of
> + *           enum iommu_hw_info_type defined in include/uapi/linux/iommufd.h.
> + *           The drivers that support this op should define a unique type
> + *           in include/uapi/linux/iommufd.h. The data buffer returned by this
> + *           op is allocated in the IOMMU driver and the caller should free it
> + *           after use. Return the data buffer if success, or ERR_PTR on
> + *           failure.
>    * @domain_alloc: allocate iommu domain
>    * @probe_device: Add device to iommu driver handling
>    * @release_device: Remove device from iommu driver handling
> @@ -257,6 +265,7 @@ struct iommu_iotlb_gather {
>    */
>   struct iommu_ops {
>   	bool (*capable)(struct device *dev, enum iommu_cap);
> +	void *(*hw_info)(struct device *dev, u32 *length, u32 *type);
>   
>   	/* Domain allocation and freeing by the iommu driver */
>   	struct iommu_domain *(*domain_alloc)(unsigned iommu_domain_type);
> diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
> index 8245c01adca6..1f616b0f8ae0 100644
> --- a/include/uapi/linux/iommufd.h
> +++ b/include/uapi/linux/iommufd.h
> @@ -370,4 +370,12 @@ struct iommu_hwpt_alloc {
>   	__u32 __reserved;
>   };
>   #define IOMMU_HWPT_ALLOC _IO(IOMMUFD_TYPE, IOMMUFD_CMD_HWPT_ALLOC)
> +
> +/**
> + * enum iommu_hw_info_type - IOMMU Hardware Info Types
> + * @IOMMU_HW_INFO_TYPE_NONE: Used by the drivers that does not report hardware info
It looks like this:
/s/does/do

Thanks,
Jingqi