Add UAPI definitions for userfaultfd working set tracking on anonymous memory:
- UFFD_FEATURE_MINOR_ANON: minor fault support for anonymous memory - UFFD_FEATURE_MINOR_ASYNC: auto-resolve minor faults without handler - UFFDIO_DEACTIVATE: mark pages as deactivated (protnone or PTE zap) Not yet added to UFFD_API_FEATURES or UFFD_API_RANGE_IOCTLS. Signed-off-by: Kiryl Shutsemau (Meta) <[email protected]> Assisted-by: Claude:claude-opus-4-6 --- include/uapi/linux/userfaultfd.h | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h index 2841e4ea8f2c..336d07e1b6de 100644 --- a/include/uapi/linux/userfaultfd.h +++ b/include/uapi/linux/userfaultfd.h @@ -79,6 +79,7 @@ #define _UFFDIO_WRITEPROTECT (0x06) #define _UFFDIO_CONTINUE (0x07) #define _UFFDIO_POISON (0x08) +#define _UFFDIO_DEACTIVATE (0x09) #define _UFFDIO_API (0x3F) /* userfaultfd ioctl ids */ @@ -103,6 +104,8 @@ struct uffdio_continue) #define UFFDIO_POISON _IOWR(UFFDIO, _UFFDIO_POISON, \ struct uffdio_poison) +#define UFFDIO_DEACTIVATE _IOR(UFFDIO, _UFFDIO_DEACTIVATE, \ + struct uffdio_range) /* read() structure */ struct uffd_msg { @@ -230,6 +233,18 @@ struct uffdio_api { * * UFFD_FEATURE_MOVE indicates that the kernel supports moving an * existing page contents from userspace. + * + * UFFD_FEATURE_MINOR_ANON indicates that minor fault interception + * is supported for anonymous private memory. Pages are made + * inaccessible via UFFDIO_DEACTIVATE (sets PROT_NONE while + * preserving the page) and faults are delivered when the pages + * are re-accessed. + * + * UFFD_FEATURE_MINOR_ASYNC indicates asynchronous minor fault + * mode. When set, faults on deactivated pages are auto-resolved + * by the kernel (PTE permissions restored immediately) without + * delivering a message to the userfaultfd handler. Use + * PAGEMAP_SCAN to find pages that were not re-accessed. */ #define UFFD_FEATURE_PAGEFAULT_FLAG_WP (1<<0) #define UFFD_FEATURE_EVENT_FORK (1<<1) @@ -248,6 +263,8 @@ struct uffdio_api { #define UFFD_FEATURE_POISON (1<<14) #define UFFD_FEATURE_WP_ASYNC (1<<15) #define UFFD_FEATURE_MOVE (1<<16) +#define UFFD_FEATURE_MINOR_ANON (1<<17) +#define UFFD_FEATURE_MINOR_ASYNC (1<<18) __u64 features; __u64 ioctls; -- 2.51.2
