Messages in this thread Patch in this message | | | From | Jacob Pan <> | Subject | [PATCH v2 1/3] iommu/uapi: Define uapi version and capabilities | Date | Wed, 25 Mar 2020 16:17:05 -0700 |
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Having a single UAPI version to govern the user-kernel data structures makes compatibility check straightforward. On the contrary, supporting combinations of multiple versions of the data can be a nightmare to maintain.
This patch defines a unified UAPI version to be used for compatibility checks between user and kernel.
--- v2: Rewrite extension rules to disallow adding new members. Use padding and union extensions only. ---
Signed-off-by: Liu Yi L <yi.l.liu@intel.com> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com> Link: https://lkml.org/lkml/2020/2/3/1126 --- include/uapi/linux/iommu.h | 53 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 53 insertions(+)
diff --git a/include/uapi/linux/iommu.h b/include/uapi/linux/iommu.h index d7bcbc5f79b0..25dba9198d7f 100644 --- a/include/uapi/linux/iommu.h +++ b/include/uapi/linux/iommu.h @@ -8,6 +8,59 @@ #include <linux/types.h> +/** + * Current version of the IOMMU user API. This is intended for query + * between user and kernel to determine compatible data structures. + * + * UAPI version can be bumped up with the following rules: + * 1. All data structures passed between user and kernel space share + * the same version number. i.e. any extension to any structure + * results in version number increment. + * + * 2. Data structures are open to extension but closed to modification. + * Extensions are allowed in two places: + * - the padding bytes with a flag bit for each new member + * - new union members at the end of each structure + * + * No new members can be added after padding bytes are exhausted. + * The reason is that the union size can change when new members are + * added, having new member at the end would break backward + * compatibility. Expansion of the union would move the new member + * to different offset between versions. + * + * Flag bits can be added without size change but existing ones + * cannot be altered. + * + * 3. Versions are backward compatible. + * + * 4. Version to size lookup is supported by kernel internal API for each + * API function type. @version is mandatory for new data structures + * and must be at the beginning with type of __u32. + */ +#define IOMMU_UAPI_VERSION 1 +static inline int iommu_get_uapi_version(void) +{ + return IOMMU_UAPI_VERSION; +} + +/* + * Supported UAPI features that can be reported to user space. + * These types represent the capability available in the kernel. + * + * REVISIT: UAPI version also implies the capabilities. Should we + * report them explicitly? + */ +enum IOMMU_UAPI_DATA_TYPES { + IOMMU_UAPI_BIND_GPASID, + IOMMU_UAPI_CACHE_INVAL, + IOMMU_UAPI_PAGE_RESP, + NR_IOMMU_UAPI_TYPE, +}; + +#define IOMMU_UAPI_CAP_MASK ((1 << IOMMU_UAPI_BIND_GPASID) | \ + (1 << IOMMU_UAPI_CACHE_INVAL) | \ + (1 << IOMMU_UAPI_PAGE_RESP)) + #define IOMMU_FAULT_PERM_READ (1 << 0) /* read */ #define IOMMU_FAULT_PERM_WRITE (1 << 1) /* write */ #define IOMMU_FAULT_PERM_EXEC (1 << 2) /* exec */ -- 2.7.4
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