From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f70.google.com (mail-it0-f70.google.com [209.85.214.70]) by kanga.kvack.org (Postfix) with ESMTP id 2C6946B0273 for ; Fri, 16 Dec 2016 09:48:29 -0500 (EST) Received: by mail-it0-f70.google.com with SMTP id o141so21452203itc.1 for ; Fri, 16 Dec 2016 06:48:29 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id u78si6146369ioi.236.2016.12.16.06.48.28 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 16 Dec 2016 06:48:28 -0800 (PST) From: Andrea Arcangeli Subject: [PATCH 26/42] userfaultfd: hugetlbfs: UFFD_FEATURE_MISSING_HUGETLBFS Date: Fri, 16 Dec 2016 15:48:05 +0100 Message-Id: <20161216144821.5183-27-aarcange@redhat.com> In-Reply-To: <20161216144821.5183-1-aarcange@redhat.com> References: <20161216144821.5183-1-aarcange@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org, Andrew Morton Cc: Michael Rapoport , "Dr. David Alan Gilbert" , Mike Kravetz , Pavel Emelyanov , Hillf Danton Userland developers asked to be notified immediately by the UFFDIO_API ioctl if hugetlbfs missing mode is supported by userfaultfd in the running kernel. This avoids the need to run UFFDIO_REGISTER on a hugetlbfs virtual memory range to find out. Signed-off-by: Andrea Arcangeli --- include/uapi/linux/userfaultfd.h | 28 +++++++++++++++++++++++++--- 1 file changed, 25 insertions(+), 3 deletions(-) diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h index a3828a9..7293321 100644 --- a/include/uapi/linux/userfaultfd.h +++ b/include/uapi/linux/userfaultfd.h @@ -18,9 +18,10 @@ * means the userland is reading). */ #define UFFD_API ((__u64)0xAA) -#define UFFD_API_FEATURES (UFFD_FEATURE_EVENT_FORK | \ - UFFD_FEATURE_EVENT_REMAP | \ - UFFD_FEATURE_EVENT_MADVDONTNEED) +#define UFFD_API_FEATURES (UFFD_FEATURE_EVENT_FORK | \ + UFFD_FEATURE_EVENT_REMAP | \ + UFFD_FEATURE_EVENT_MADVDONTNEED | \ + UFFD_FEATURE_MISSING_HUGETLBFS) #define UFFD_API_IOCTLS \ ((__u64)1 << _UFFDIO_REGISTER | \ (__u64)1 << _UFFDIO_UNREGISTER | \ @@ -125,11 +126,32 @@ struct uffdio_api { * Note: UFFD_EVENT_PAGEFAULT and UFFD_PAGEFAULT_FLAG_WRITE * are to be considered implicitly always enabled in all kernels as * long as the uffdio_api.api requested matches UFFD_API. + * + * UFFD_FEATURE_MISSING_HUGETLBFS means an UFFDIO_REGISTER + * with UFFDIO_REGISTER_MODE_MISSING mode will succeed on + * hugetlbfs virtual memory ranges. Adding or not adding + * UFFD_FEATURE_MISSING_HUGETLBFS to uffdio_api.features has + * no real functional effect after UFFDIO_API returns, but + * it's only useful for an initial feature set probe at + * UFFDIO_API time. There are two ways to use it: + * + * 1) by adding UFFD_FEATURE_MISSING_HUGETLBFS to the + * uffdio_api.features before calling UFFDIO_API, an error + * will be returned by UFFDIO_API on a kernel without + * hugetlbfs missing support + * + * 2) the UFFD_FEATURE_MISSING_HUGETLBFS can not be added in + * uffdio_api.features and instead it will be set by the + * kernel in the uffdio_api.features if the kernel supports + * it, so userland can later check if the feature flag is + * present in uffdio_api.features after UFFDIO_API + * succeeded. */ #define UFFD_FEATURE_PAGEFAULT_FLAG_WP (1<<0) #define UFFD_FEATURE_EVENT_FORK (1<<1) #define UFFD_FEATURE_EVENT_REMAP (1<<2) #define UFFD_FEATURE_EVENT_MADVDONTNEED (1<<3) +#define UFFD_FEATURE_MISSING_HUGETLBFS (1<<4) __u64 features; __u64 ioctls; -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org