From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f200.google.com (mail-pf0-f200.google.com [209.85.192.200]) by kanga.kvack.org (Postfix) with ESMTP id 2DEC36B02E1 for ; Thu, 27 Apr 2017 10:14:52 -0400 (EDT) Received: by mail-pf0-f200.google.com with SMTP id c198so27061098pfc.19 for ; Thu, 27 Apr 2017 07:14:52 -0700 (PDT) Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com. [148.163.156.1]) by mx.google.com with ESMTPS id 1si2798405pgs.217.2017.04.27.07.14.51 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 27 Apr 2017 07:14:51 -0700 (PDT) Received: from pps.filterd (m0098409.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v3REELXj054074 for ; Thu, 27 Apr 2017 10:14:50 -0400 Received: from e06smtp10.uk.ibm.com (e06smtp10.uk.ibm.com [195.75.94.106]) by mx0a-001b2d01.pphosted.com with ESMTP id 2a3f7mspks-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 27 Apr 2017 10:14:50 -0400 Received: from localhost by e06smtp10.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 27 Apr 2017 15:14:46 +0100 From: Mike Rapoport Subject: [PATCH man-pages 2/2] ioctl_userfaultfd.2: start adding details about userfaultfd features Date: Thu, 27 Apr 2017 17:14:34 +0300 In-Reply-To: <1493302474-4701-1-git-send-email-rppt@linux.vnet.ibm.com> References: <1493302474-4701-1-git-send-email-rppt@linux.vnet.ibm.com> Message-Id: <1493302474-4701-3-git-send-email-rppt@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: "Michael Kerrisk (man-pages)" Cc: Andrea Arcangeli , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-man@vger.kernel.org, Mike Rapoport Signed-off-by: Mike Rapoport --- man2/ioctl_userfaultfd.2 | 53 ++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 51 insertions(+), 2 deletions(-) diff --git a/man2/ioctl_userfaultfd.2 b/man2/ioctl_userfaultfd.2 index 42bf7a7..cdc07e0 100644 --- a/man2/ioctl_userfaultfd.2 +++ b/man2/ioctl_userfaultfd.2 @@ -121,22 +121,70 @@ and explicitly enable userfaultfd features that are disabled by default. The kernel always reports all the available features in the .I features field. + +To enable userfaultfd features the application should set +a bit corresponding to each feature it wants to enable in the +.I features +field. +If the kernel supports all the requested features it will enable them. +Otherwise it will zero out the returned +.I uffdio_api +structure and return +.BR EINVAL . .\" FIXME add more details about feature negotiation and enablement Since Linux 4.11, the following feature bits may be set: .TP .B UFFD_FEATURE_EVENT_FORK +When this feature is enabled, +the userfaultfd objects associated with a parent process are duplicated +into the child process during +.BR fork (2) +system call and the +.I UFFD_EVENT_FORK +is delivered to the userfaultfd monitor .TP .B UFFD_FEATURE_EVENT_REMAP +If this feature is enabled, +when the faulting process invokes +.BR mremap (2) +system call +the userfaultfd monitor will receive an event of type +.I UFFD_EVENT_REMAP. .TP .B UFFD_FEATURE_EVENT_REMOVE +If this feature is enabled, +when the faulting process calls +.BR madvise(2) +system call with +.I MADV_DONTNEED +or +.I MADV_REMOVE +advice to free a virtual memory area +the userfaultfd monitor will receive an event of type +.I UFFD_EVENT_REMOVE. .TP .B UFFD_FEATURE_EVENT_UNMAP +If this feature is enabled, +when the faulting process unmaps virtual memory either explicitly with +.BR munmap (2) +system call, or implicitly either during +.BR mmap (2) +or +.BR mremap (2) +system call, +the userfaultfd monitor will receive an event of type +.I UFFD_EVENT_UNMAP .TP .B UFFD_FEATURE_MISSING_HUGETLBFS +If this feature bit is set, +the kernel supports registering userfaultfd ranges on hugetlbfs +virtual memory areas .TP .B UFFD_FEATURE_MISSING_SHMEM -.\" FIXME add feature description +If this feature bit is set, +the kernel supports registering userfaultfd ranges on tmpfs +virtual memory areas The returned .I ioctls @@ -182,7 +230,8 @@ The API version requested in the .I api field is not supported by this kernel, or the .I features -field was not zero. +field passed to the kernel includes feature bits that are not supported +by the current kernel version. .\" FIXME In the above error case, the returned 'uffdio_api' structure is .\" zeroed out. Why is this done? This should be explained in the manual page. .\" -- 1.9.1 -- 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