Re: [PATCH v9 3/7] iommu/uapi: Introduce enum type for PASID data format

Joerg Roedel
2020-09-18T09:45:01Z

On Fri, Sep 11, 2020 at 02:57:52PM -0700, Jacob Pan wrote:
> There can be multiple vendor-specific PASID data formats used in UAPI
> structures. This patch adds enum type with a last entry which makes
> range checking much easier.

But it also makes it much easier to screw up the numbers (which are ABI)
by inserting a new value into the middle. I prefer defines here, or
alternativly BUILD_BUG_ON() checks for the numbers.

Regards,

Joerg

>
> Suggested-by: Alex Williamson <alex.williamson@redhat.com>
> Reviewed-by: Eric Auger <eric.auger@redhat.com>
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> ---
> include/uapi/linux/iommu.h | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/include/uapi/linux/iommu.h b/include/uapi/linux/iommu.h
> index b42acc8fe007..7cc6ee6c41f7 100644
> --- a/include/uapi/linux/iommu.h
> +++ b/include/uapi/linux/iommu.h
> @@ -298,11 +298,16 @@ struct iommu_gpasid_bind_data_vtd {
> IOMMU_SVA_VTD_GPASID_PCD | \
> IOMMU_SVA_VTD_GPASID_PWT)
>
> +enum iommu_pasid_data_format {
> + IOMMU_PASID_FORMAT_INTEL_VTD = 1,
> + IOMMU_PASID_FORMAT_LAST,
> +};
> +
> /**
> * struct iommu_gpasid_bind_data - Information about device and guest PASID binding
> * @argsz: User filled size of this data
> * @version: Version of this data structure
> - * @format: PASID table entry format
> + * @format: PASID table entry format of enum iommu_pasid_data_format type
> * @flags: Additional information on guest bind request
> * @gpgd: Guest page directory base of the guest mm to bind
> * @hpasid: Process address space ID used for the guest mm in host IOMMU
> @@ -321,7 +326,6 @@ struct iommu_gpasid_bind_data {
> __u32 argsz;
> #define IOMMU_GPASID_BIND_VERSION_1 1
> __u32 version;
> -#define IOMMU_PASID_FORMAT_INTEL_VTD 1
> __u32 format;
> __u32 addr_width;
> #define IOMMU_SVA_GPASID_VAL (1 << 0) /* guest PASID valid */
> --
> 2.7.4