Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx> --- Documentation/vm/userfaultfd.txt | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/Documentation/vm/userfaultfd.txt b/Documentation/vm/userfaultfd.txt index 3557edd..70a3c94 100644 --- a/Documentation/vm/userfaultfd.txt +++ b/Documentation/vm/userfaultfd.txt @@ -3,8 +3,8 @@ == Objective == Userfaults allow the implementation of on-demand paging from userland -and more generally they allow userland to take control various memory -page faults, something otherwise only the kernel code could do. +and more generally they allow userland to take control of various +memory page faults, something otherwise only the kernel code could do. For example userfaults allows a proper and more optimal implementation of the PROT_NONE+SIGSEGV trick. @@ -47,10 +47,10 @@ When first opened the userfaultfd must be enabled invoking the UFFDIO_API ioctl specifying a uffdio_api.api value set to UFFD_API (or a later API version) which will specify the read/POLLIN protocol userland intends to speak on the UFFD and the uffdio_api.features -userland needs to be enabled. The UFFDIO_API ioctl if successful -(i.e. if the requested uffdio_api.api is spoken also by the running -kernel and the requested features are going to be enabled) will return -into uffdio_api.features and uffdio_api.ioctls two 64bit bitmasks of +userland requires. The UFFDIO_API ioctl if successful (i.e. if the +requested uffdio_api.api is spoken also by the running kernel and the +requested features are going to be enabled) will return into +uffdio_api.features and uffdio_api.ioctls two 64bit bitmasks of respectively all the available features of the read(2) protocol and the generic ioctl available. @@ -77,7 +77,9 @@ The primary ioctl to resolve userfaults is UFFDIO_COPY. That atomically copies a page into the userfault registered range and wakes up the blocked userfaults (unless uffdio_copy.mode & UFFDIO_COPY_MODE_DONTWAKE is set). Other ioctl works similarly to -UFFDIO_COPY. +UFFDIO_COPY. They're atomic as in guaranteeing that nothing can see an +half copied page since it'll keep userfaulting until the copy has +finished. == QEMU/KVM == -- 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>