[PATCH v3 5/6] mm: userfaultfd: add UFFD_FEATURE_MINOR_GUEST_MEMFD

[Nikita Kalyazin <kalyazin@amazon.com>]

Signed-off-by: Nikita Kalyazin <kalyazin@amazon.com>
---
 fs/userfaultfd.c                 | 3 ++-
 include/uapi/linux/userfaultfd.h | 8 +++++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 97c4d71115d8..32152bfa462a 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1954,7 +1954,8 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx,
 	uffdio_api.features = UFFD_API_FEATURES;
 #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR
 	uffdio_api.features &=
-		~(UFFD_FEATURE_MINOR_HUGETLBFS | UFFD_FEATURE_MINOR_SHMEM);
+		~(UFFD_FEATURE_MINOR_HUGETLBFS | UFFD_FEATURE_MINOR_SHMEM |
+		UFFD_FEATURE_MINOR_GUEST_MEMFD);
 #endif
 #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP
 	uffdio_api.features &= ~UFFD_FEATURE_PAGEFAULT_FLAG_WP;
diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h
index 2841e4ea8f2c..ed688797eba7 100644
--- a/include/uapi/linux/userfaultfd.h
+++ b/include/uapi/linux/userfaultfd.h
@@ -42,7 +42,8 @@
 			   UFFD_FEATURE_WP_UNPOPULATED |	\
 			   UFFD_FEATURE_POISON |		\
 			   UFFD_FEATURE_WP_ASYNC |		\
-			   UFFD_FEATURE_MOVE)
+			   UFFD_FEATURE_MOVE |			\
+			   UFFD_FEATURE_MINOR_GUEST_MEMFD)
 #define UFFD_API_IOCTLS				\
 	((__u64)1 << _UFFDIO_REGISTER |		\
 	 (__u64)1 << _UFFDIO_UNREGISTER |	\
@@ -230,6 +231,10 @@ struct uffdio_api {
 	 *
 	 * UFFD_FEATURE_MOVE indicates that the kernel supports moving an
 	 * existing page contents from userspace.
+	 *
+	 * UFFD_FEATURE_MINOR_GUEST_MEMFD indicates the same support as
+	 * UFFD_FEATURE_MINOR_HUGETLBFS, but for guest_memfd-backed pages
+	 * instead.
 	 */
 #define UFFD_FEATURE_PAGEFAULT_FLAG_WP		(1<<0)
 #define UFFD_FEATURE_EVENT_FORK			(1<<1)
@@ -248,6 +253,7 @@ 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_GUEST_MEMFD		(1<<17)
 	__u64 features;
 
 	__u64 ioctls;
-- 
2.47.1