Hi Jacob, On 1/29/20 7:02 AM, Jacob Pan wrote: > Define a unified UAPI version to be used for compatibility > checks between user and kernel. > > Signed-off-by: Liu Yi L <[email protected]> > Signed-off-by: Jacob Pan <[email protected]> > --- > include/uapi/linux/iommu.h | 48 > ++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 48 insertions(+) > > diff --git a/include/uapi/linux/iommu.h b/include/uapi/linux/iommu.h > index fcafb6401430..65a26c2519ee 100644 > --- a/include/uapi/linux/iommu.h > +++ b/include/uapi/linux/iommu.h > @@ -8,6 +8,54 @@ > > #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. > + * > + * 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. I would rather put the above justification in the commit msg and not here. > + * > + * 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 to any structure s/to to/to > + * results in version bump up. in a version number increment? > + * > + * 2. Data structures are open to extension but closed to modification.> + * > New fields must be added at the end of each data structure with > + * 64bit alignment. 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 */ > Thanks
Eric _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
