From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f71.google.com (mail-wm0-f71.google.com [74.125.82.71]) by kanga.kvack.org (Postfix) with ESMTP id 304C26B02EE for ; Thu, 27 Apr 2017 13:26:26 -0400 (EDT) Received: by mail-wm0-f71.google.com with SMTP id u65so1676427wmu.12 for ; Thu, 27 Apr 2017 10:26:26 -0700 (PDT) Received: from mail-wm0-x244.google.com (mail-wm0-x244.google.com. [2a00:1450:400c:c09::244]) by mx.google.com with ESMTPS id 141si65200wmr.5.2017.04.27.10.26.24 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 27 Apr 2017 10:26:24 -0700 (PDT) Received: by mail-wm0-x244.google.com with SMTP id u65so6022031wmu.3 for ; Thu, 27 Apr 2017 10:26:24 -0700 (PDT) Subject: Re: [PATCH man-pages 2/2] ioctl_userfaultfd.2: start adding details about userfaultfd features References: <1493302474-4701-1-git-send-email-rppt@linux.vnet.ibm.com> <1493302474-4701-3-git-send-email-rppt@linux.vnet.ibm.com> From: "Michael Kerrisk (man-pages)" Message-ID: <063f52b3-ca66-8196-80f4-a1b7fac90de5@gmail.com> Date: Thu, 27 Apr 2017 19:26:22 +0200 MIME-Version: 1.0 In-Reply-To: <1493302474-4701-3-git-send-email-rppt@linux.vnet.ibm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Mike Rapoport Cc: mtk.manpages@gmail.com, Andrea Arcangeli , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-man@vger.kernel.org On 04/27/2017 04:14 PM, Mike Rapoport wrote: > Signed-off-by: Mike Rapoport Thanks, Mike. Applied, and lightly edited. All changes now pushed to Git. Cheers, Michael > --- > 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. > .\" > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- 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