Hello Andrew, On Wed, Jan 04, 2017 at 03:01:46PM -0800, Andrew Morton wrote: > On Fri, 16 Dec 2016 15:47:46 +0100 Andrea Arcangeli <aarcange@xxxxxxxxxx> wrote: > > > This will allow userland to probe all features available in the > > kernel. It will however only enable the requested features in the > > open userfaultfd context. > > Is the user-facing documentation updated somewhere? I guess that's The above is fully backwards compatible, in the current upstream the feature flags are empty. #define UFFD_API_FEATURES (0) So it behaves the same. > Documentation/vm/userfaultfd.txt. Does a manpage exist yet? The manpage is merged and in sync with the above comment, but it wasn't updated for hugetlbfs shmem and non cooperative features yet. It just documents the UFFD_API_FEATURES (0) behavior according to the above git commit message. Like Mike wrote below the manpage will be updated when the new features go upstream. https://marc.info/?l=linux-man&m=148299572702201&w=2 https://marc.info/?l=linux-man&m=148304176911503&w=2 Here the text in the current manpage relevant to the above commit, so again in full sync with upstream and in sync with the new patch too because upstream behaves the same with UFFD_API_FEATURES (0): The API ioctls are used to configure userfaultfd behavior. They allow to choose what features will be enabled and what kinds of events will be delivered to the application. The api field denotes the API version requested by the application. The kernel verifies that it can support the required API, and sets the features and ioctls fields to bit masks representing all the available features and the generic ioctls available. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>