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[174.95.95.253]) by smtp.gmail.com with ESMTPSA id b7sm18610766qkj.115.2021.03.03.17.59.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Mar 2021 17:59:50 -0800 (PST) From: Peter Xu To: linux-man@vger.kernel.org Cc: Mike Rapoport , Nadav Amit , linux-kernel@vger.kernel.org, Linux MM Mailing List , peterx@redhat.com, Axel Rasmussen , Alejandro Colomar , Andrea Arcangeli , Andrew Morton , Michael Kerrisk Subject: [PATCH 1/4] userfaultfd.2: Add UFFD_FEATURE_THREAD_ID docs Date: Wed, 3 Mar 2021 20:59:44 -0500 Message-Id: <20210304015947.517713-2-peterx@redhat.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210304015947.517713-1-peterx@redhat.com> References: <20210304015947.517713-1-peterx@redhat.com> MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=peterx@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Stat-Signature: 1jp6k7mwks51isryj5gofi6kqupifb4s X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 60A26E0011E1 Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf30; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=216.205.24.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1614823193-334386 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: UFFD_FEATURE_THREAD_ID is supported since Linux 4.14. Signed-off-by: Peter Xu --- man2/userfaultfd.2 | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/man2/userfaultfd.2 b/man2/userfaultfd.2 index e7dc9f813..2d14effc6 100644 --- a/man2/userfaultfd.2 +++ b/man2/userfaultfd.2 @@ -77,6 +77,12 @@ When the last file descriptor referring to a userfaultfd object is closed, all memory ranges that were registered with the object are unregistered and unread events are flushed. .\" +.PP +Since Linux 4.14, userfaultfd page fault message can selectively embed fault +thread ID information into the fault message. One needs to enable this feature +explicitly using the +.BR UFFD_FEATURE_THREAD_ID +feature bit when initializing the userfaultfd context, otherwise disabled. .SS Usage The userfaultfd mechanism is designed to allow a thread in a multithreaded program to perform user-space paging for the other threads in the process. @@ -229,6 +235,9 @@ struct uffd_msg { struct { __u64 flags; /* Flags describing fault */ __u64 address; /* Faulting address */ + union { + __u32 ptid; /* Thread ID of the fault */ + } feat; } pagefault; struct { /* Since Linux 4.11 */ @@ -358,6 +367,9 @@ otherwise it is a read fault. .\" UFFD_PAGEFAULT_FLAG_WP is not yet supported. .RE .TP +.I pagefault.feat.pid +The thread ID that triggered the page fault. +.TP .I fork.ufd The file descriptor associated with the userfault object created for the child created by From patchwork Thu Mar 4 01:59:45 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Xu X-Patchwork-Id: 12115325 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5A946C433E6 for ; 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[174.95.95.253]) by smtp.gmail.com with ESMTPSA id b7sm18610766qkj.115.2021.03.03.17.59.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Mar 2021 17:59:52 -0800 (PST) From: Peter Xu To: linux-man@vger.kernel.org Cc: Mike Rapoport , Nadav Amit , linux-kernel@vger.kernel.org, Linux MM Mailing List , peterx@redhat.com, Axel Rasmussen , Alejandro Colomar , Andrea Arcangeli , Andrew Morton , Michael Kerrisk Subject: [PATCH 2/4] userfaultfd.2: Add write-protect mode Date: Wed, 3 Mar 2021 20:59:45 -0500 Message-Id: <20210304015947.517713-3-peterx@redhat.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210304015947.517713-1-peterx@redhat.com> References: <20210304015947.517713-1-peterx@redhat.com> MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=peterx@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Stat-Signature: gety31go6i5a9jk8qepyows8t3jiusbj X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: C53C3C0001EA Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf06; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=63.128.21.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1614823195-799370 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Write-protect mode is supported starting from Linux 5.7. Signed-off-by: Peter Xu --- man2/userfaultfd.2 | 88 ++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 86 insertions(+), 2 deletions(-) diff --git a/man2/userfaultfd.2 b/man2/userfaultfd.2 index 2d14effc6..8e1602d62 100644 --- a/man2/userfaultfd.2 +++ b/man2/userfaultfd.2 @@ -78,6 +78,28 @@ all memory ranges that were registered with the object are unregistered and unread events are flushed. .\" .PP +Currently, userfaultfd supports two modes of registration: +.TP +.BR UFFDIO_REGISTER_MODE_MISSING +When registered with +.BR UFFDIO_REGISTER_MODE_MISSING +mode, the userspace will receive a page fault message when a missing page is +accessed. The faulted thread will be stopped from execution until the page +fault is resolved from the userspace by either an +.BR UFFDIO_COPY +or an +.BR UFFDIO_ZEROPAGE +ioctl. +.TP +.BR UFFDIO_REGISTER_MODE_WP +When registered with +.BR UFFDIO_REGISTER_MODE_WP +mode, the userspace will receive a page fault message when a write-protected +page is written. The faulted thread will be stopped from execution until the +userspace un-write-protect the page using an +.BR UFFDIO_WRITEPROTECT +ioctl. +.PP Since Linux 4.14, userfaultfd page fault message can selectively embed fault thread ID information into the fault message. One needs to enable this feature explicitly using the @@ -143,6 +165,16 @@ single threaded non-cooperative userfaultfd manager implementations. .\" and limitations remaining in 4.11 .\" Maybe it's worth adding a dedicated sub-section... .\" +.PP +Starting from Linux 5.7, userfaultfd is able to do synchronous page dirty +tracking using the new write-protection register mode. One should check +against the feature bit +.B UFFD_FEATURE_PAGEFAULT_FLAG_WP +before using this feature. Similar to the original userfaultfd missing mode, +the write-protect mode will generate an userfaultfd message when the protected +page is written. The user needs to resolve the page fault by unprotecting the +faulted page and kick the faulted thread to continue. For more information, +please read the "Userfaultfd write-protect mode" section below. .SS Userfaultfd operation After the userfaultfd object is created with .BR userfaultfd (), @@ -218,6 +250,54 @@ userfaultfd can be used only with anonymous private memory mappings. Since Linux 4.11, userfaultfd can be also used with hugetlbfs and shared memory mappings. .\" +.SS Userfaultfd write-protect mode +Since Linux 5.7, userfaultfd started to support write-protect mode. The user +needs to first check availability of this feature using +.BR UFFDIO_API +ioctl against the feature bit +.BR UFFD_FEATURE_PAGEFAULT_FLAG_WP . +.PP +To register with userfaultfd write-protect mode, the user needs to send the +.BR UFFDIO_REGISTER +ioctl with mode +.BR UFFDIO_REGISTER_MODE_WP +set. Note that it's legal to monitor the same memory range with multiple +modes. For example, the user can do +.BR UFFDIO_REGISTER +with the mode set to +.BR UFFDIO_REGISTER_MODE_MISSING\ |\ UFFDIO_REGISTER_MODE_WP. +When there is only +.BR UFFDIO_REGISTER_MODE_WP +registered, the userspace will +.I not +receive any message when a missing page is written. Instead, the userspace +will only receive a write-protect page fault message when an existing but +write-protected page got written. +.PP +After the +.BR UFFDIO_REGISTER +ioctl completed with +.BR UFFDIO_REGISTER_MODE_WP +mode set, one can write-protect any existing memory within the range using the +ioctl +.BR UFFDIO_WRITEPROTECT +where +.I uffdio_writeprotect.mode +should be set to +.BR UFFDIO_WRITEPROTECT_MODE_WP . +.PP +When a write-protect event happens, the userspace will receive a page fault +message whose +.I uffd_msg.pagefault.flags +will be with +.BR UFFD_PAGEFAULT_FLAG_WP +flag set. Note: since only writes can trigger such kind of fault, +write-protect messages will always be with +.BR UFFD_PAGEFAULT_FLAG_WRITE +bit set too along with +.BR UFFD_PAGEFAULT_FLAG_WP . +.PP +Currently, write-protect mode only supports private anonymous memory. .SS Reading from the userfaultfd structure Each .BR read (2) @@ -363,8 +443,12 @@ flag (see .BR ioctl_userfaultfd (2)) and this flag is set, this a write fault; otherwise it is a read fault. -.\" -.\" UFFD_PAGEFAULT_FLAG_WP is not yet supported. +.TP +.B UFFD_PAGEFAULT_FLAG_WP +If the address is in a range that was registered with the +.B UFFDIO_REGISTER_MODE_WP +flag, when this bit is set it means it's a write-protect fault. Otherwise it's +a page missing fault. .RE .TP .I pagefault.feat.pid From patchwork Thu Mar 4 01:59:46 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Xu X-Patchwork-Id: 12115327 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8662DC433E0 for ; Thu, 4 Mar 2021 02:00:00 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0C699650DE for ; Thu, 4 Mar 2021 02:00:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0C699650DE Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 404BF6B0008; Wed, 3 Mar 2021 20:59:58 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 3DDA36B000A; Wed, 3 Mar 2021 20:59:58 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1E3416B000C; Wed, 3 Mar 2021 20:59:58 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0218.hostedemail.com [216.40.44.218]) by kanga.kvack.org (Postfix) with ESMTP id 0245F6B0008 for ; Wed, 3 Mar 2021 20:59:57 -0500 (EST) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id BA2EB181D863A for ; Thu, 4 Mar 2021 01:59:57 +0000 (UTC) X-FDA: 77880536034.16.B659BDC Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [63.128.21.124]) by imf03.hostedemail.com (Postfix) with ESMTP id E0533C0007C5 for ; Thu, 4 Mar 2021 01:59:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1614823196; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=67CmUKUe+TmQG3UkcCcwTlXVexG5QMLko4/9hpCBQsc=; b=U083sbMQccKYBOFqB3GUDC1r9F1VD31+A69FTAyip8/0KBG4EQHDxJDQqA+d506thUqq/e 0RCRvsD/n2OECqhQY985qTUM+dVfgtKC/87vA6japdI1BRiZyqGKYVEZQ3PsxgAuv2sU0z FHMedsPQwpCzQVbIarb8LAUOxSWhUIA= Received: from mail-qt1-f200.google.com (mail-qt1-f200.google.com [209.85.160.200]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-228-z_rJnAvkPbWfpvfpVbLyeg-1; Wed, 03 Mar 2021 20:59:55 -0500 X-MC-Unique: z_rJnAvkPbWfpvfpVbLyeg-1 Received: by mail-qt1-f200.google.com with SMTP id b7so17610443qtj.16 for ; Wed, 03 Mar 2021 17:59:55 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=67CmUKUe+TmQG3UkcCcwTlXVexG5QMLko4/9hpCBQsc=; b=oo4IKXf3NOqD4uokVXVrhs64yGH0IMrxDgYjLGjk3vkL9UjPEyeNoe+OHS0KOD8Ggq wG0Q7oinDnGrZXGyMKAc8rDrclZaN4E3PVBGhoyOXYx5hFKqmlUhSrhU9b29XEBG1c+U XG/T1Kv62jtTV0Tl2v2enGM6S0i5HX/xDPzVQS560oWBcWpzjns/dhmaWNZxwP9Vq+6g bMS6R929jFN9aHenYos/QFOWo5HkXjKz4VkKyzC1F/UkFtwTec9pXPkSMlUL+LQdngpk oWjIPFnP1d2PSf9vsj42zCHRt6cnAfalZhPAUt5qXvrORF0zI1jIYtrcncRq+/aAnRa0 wz0A== X-Gm-Message-State: AOAM5327VTRG3TUtN9YX1qIsbwVOA2eXUQpmVb9BUMvgOoKtmBO5cxtd OVM3pl/sXf/WLraqlzoC4p8IRTtZAMCG/KXSkWlW0/1EqW4pWw8zCahr/bkoL3vWK6QDdHT70zF xGkVVCsMUO6I= X-Received: by 2002:a05:620a:887:: with SMTP id b7mr1915869qka.215.1614823194811; Wed, 03 Mar 2021 17:59:54 -0800 (PST) X-Google-Smtp-Source: ABdhPJxo2VGf7bBuTU7j/MVXQgMA7Qwe9+C87OoGoXi+q2ohdE1GsIQSeuTM/aQKjlxmq66uapauvw== X-Received: by 2002:a05:620a:887:: with SMTP id b7mr1915861qka.215.1614823194633; Wed, 03 Mar 2021 17:59:54 -0800 (PST) Received: from xz-x1.redhat.com (bras-vprn-toroon474qw-lp130-25-174-95-95-253.dsl.bell.ca. [174.95.95.253]) by smtp.gmail.com with ESMTPSA id b7sm18610766qkj.115.2021.03.03.17.59.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Mar 2021 17:59:54 -0800 (PST) From: Peter Xu To: linux-man@vger.kernel.org Cc: Mike Rapoport , Nadav Amit , linux-kernel@vger.kernel.org, Linux MM Mailing List , peterx@redhat.com, Axel Rasmussen , Alejandro Colomar , Andrea Arcangeli , Andrew Morton , Michael Kerrisk Subject: [PATCH 3/4] ioctl_userfaultfd.2: Add UFFD_FEATURE_THREAD_ID docs Date: Wed, 3 Mar 2021 20:59:46 -0500 Message-Id: <20210304015947.517713-4-peterx@redhat.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210304015947.517713-1-peterx@redhat.com> References: <20210304015947.517713-1-peterx@redhat.com> MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=peterx@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: E0533C0007C5 X-Stat-Signature: 75gkmgqm9rbywkqjjobey49qogpd3wrg Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf03; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=63.128.21.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1614823195-791056 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: UFFD_FEATURE_THREAD_ID is supported in Linux 4.14. Signed-off-by: Peter Xu --- man2/ioctl_userfaultfd.2 | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/man2/ioctl_userfaultfd.2 b/man2/ioctl_userfaultfd.2 index 47ae5f473..1965d1932 100644 --- a/man2/ioctl_userfaultfd.2 +++ b/man2/ioctl_userfaultfd.2 @@ -208,6 +208,10 @@ signal will be sent to the faulting process. Applications using this feature will not require the use of a userfaultfd monitor for processing memory accesses to the regions registered with userfaultfd. +.BR UFFD_FEATURE_THREAD_ID " (since Linux 4.14)" +If this feature bit is set, +.I uffd_msg.pagefault.feat.ptid +Will be set .PP The returned .I ioctls From patchwork Thu Mar 4 01:59:47 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Xu X-Patchwork-Id: 12115329 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 77F6CC433DB for ; Thu, 4 Mar 2021 02:00:02 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0CE23650DF for ; Thu, 4 Mar 2021 02:00:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0CE23650DF Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 563F26B000A; Wed, 3 Mar 2021 21:00:00 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 53AB66B000C; Wed, 3 Mar 2021 21:00:00 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 390AD6B000D; Wed, 3 Mar 2021 21:00:00 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0093.hostedemail.com [216.40.44.93]) by kanga.kvack.org (Postfix) with ESMTP id 0D9676B000A for ; Wed, 3 Mar 2021 21:00:00 -0500 (EST) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id B6F4D181D3039 for ; Thu, 4 Mar 2021 01:59:59 +0000 (UTC) X-FDA: 77880536118.22.74BDCE4 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [63.128.21.124]) by imf06.hostedemail.com (Postfix) with ESMTP id 9438BC0007C5 for ; Thu, 4 Mar 2021 01:59:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1614823198; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=DK7INWloX9H1AWnOZWZTogB23KAtqlPeswE1LI5JIvE=; b=WKCKlWs1aT8e4cMSptPC47DvLyChDJUCSd35Zgsw1nJ0C9vhXI0CWbUH5HilgN9fhSQVGP nE43w4c55s2Yp12P98c4mp9HyDmSS9Ehvu+w5y/JiTWyLIMGXUiXqda5uM8M81J1cgJd34 O+zVY006BrGsRfTwEm1yv/6M+OfhBd8= Received: from mail-qk1-f200.google.com (mail-qk1-f200.google.com [209.85.222.200]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-182-9UhqIMKBOKKFfXFeTOf03w-1; Wed, 03 Mar 2021 20:59:57 -0500 X-MC-Unique: 9UhqIMKBOKKFfXFeTOf03w-1 Received: by mail-qk1-f200.google.com with SMTP id h21so21783672qkl.12 for ; Wed, 03 Mar 2021 17:59:57 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=DK7INWloX9H1AWnOZWZTogB23KAtqlPeswE1LI5JIvE=; b=r8l1dPm4kb3BabdJKgZqyps2o8JzhrdJLvlXV2igb0C4l7k8XfVDCuKaYU9IrLU4As cblzK5b5e7yqLtbj5Duz0Le9G0AIXR9Beo6f2MUdcTzMX8mTD89s2V1ifjYpXPYq2uhL qoim+4l/bCkYaZII9glMInbJg0PDyH2KbUUCxPVq/Hs85hF2FNyE7z6ir4MN9Z9nKvy1 wu0UaRqX7P2CP1ftN4F7EpkTw4uV1OXoLttOsLqD76pDTE/C9H4yCRJE6dBbJY03kqk4 A5uzLDiUDXp/eUWjcucFOzTnja56rmglSiAsLp8lGsDC/fXkzot/TCSgID3ERi+wwXcL 3ksA== X-Gm-Message-State: AOAM53268KGKsCZpbG8JshAcvCWARJABA6iNFv0knZ5WtnXLpaArKFiy /ScqDn/kVBKF8gfIZvK9oVtblcR7ET8yq6HHBhhQcciZ5SB3OPKXSlrNEbr+IR258+FGijrxXOM QsbWi4+yAttg= X-Received: by 2002:a0c:b617:: with SMTP id f23mr2163137qve.44.1614823196920; Wed, 03 Mar 2021 17:59:56 -0800 (PST) X-Google-Smtp-Source: ABdhPJwxeZ5a1mqjFCVuCtrVoLgbBF/ndMtcWPREu37qyYMGQmwQz48Q/q8ajeD2blfbJQfQ0Oti+w== X-Received: by 2002:a0c:b617:: with SMTP id f23mr2163126qve.44.1614823196691; Wed, 03 Mar 2021 17:59:56 -0800 (PST) Received: from xz-x1.redhat.com (bras-vprn-toroon474qw-lp130-25-174-95-95-253.dsl.bell.ca. [174.95.95.253]) by smtp.gmail.com with ESMTPSA id b7sm18610766qkj.115.2021.03.03.17.59.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Mar 2021 17:59:55 -0800 (PST) From: Peter Xu To: linux-man@vger.kernel.org Cc: Mike Rapoport , Nadav Amit , linux-kernel@vger.kernel.org, Linux MM Mailing List , peterx@redhat.com, Axel Rasmussen , Alejandro Colomar , Andrea Arcangeli , Andrew Morton , Michael Kerrisk Subject: [PATCH 4/4] ioctl_userfaultfd.2: Add write-protect mode docs Date: Wed, 3 Mar 2021 20:59:47 -0500 Message-Id: <20210304015947.517713-5-peterx@redhat.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210304015947.517713-1-peterx@redhat.com> References: <20210304015947.517713-1-peterx@redhat.com> MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=peterx@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 9438BC0007C5 X-Stat-Signature: t1parjopnjcedum9hc8rp9szhpq5bfgt Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf06; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=63.128.21.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1614823198-445945 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Userfaultfd write-protect mode is supported starting from Linux 5.7. Signed-off-by: Peter Xu --- man2/ioctl_userfaultfd.2 | 74 +++++++++++++++++++++++++++++++++++++--- 1 file changed, 70 insertions(+), 4 deletions(-) diff --git a/man2/ioctl_userfaultfd.2 b/man2/ioctl_userfaultfd.2 index 1965d1932..3feb888a8 100644 --- a/man2/ioctl_userfaultfd.2 +++ b/man2/ioctl_userfaultfd.2 @@ -208,10 +208,11 @@ signal will be sent to the faulting process. Applications using this feature will not require the use of a userfaultfd monitor for processing memory accesses to the regions registered with userfaultfd. +.TP .BR UFFD_FEATURE_THREAD_ID " (since Linux 4.14)" If this feature bit is set, .I uffd_msg.pagefault.feat.ptid -Will be set +will be set to the faulted thread ID for each page fault message. .PP The returned .I ioctls @@ -233,6 +234,11 @@ operation is supported. The .B UFFDIO_UNREGISTER operation is supported. +.TP +.B 1 << _UFFDIO_WRITEPROTECT +The +.B UFFDIO_WRITEPROTECT +operation is supported. .PP This .BR ioctl (2) @@ -321,9 +327,6 @@ Track page faults on missing pages. .B UFFDIO_REGISTER_MODE_WP Track page faults on write-protected pages. .PP -Currently, the only supported mode is -.BR UFFDIO_REGISTER_MODE_MISSING . -.PP If the operation is successful, the kernel modifies the .I ioctls bit-mask field to indicate which @@ -653,6 +656,69 @@ field of the structure was not a multiple of the system page size; or .I len was zero; or the specified range was otherwise invalid. +.SS UFFDIO_WRITEPROTECT +(Since Linux 5.7) Do write-protect or write-unprotect for an userfaultfd +registered memory range with mode +.BR UFFDIO_REGISTER_MODE_WP . +.PP +The +.I argp +argument is a pointer to a +.I uffdio_range +structure as shown below: +.PP +.in +4n +.EX +struct uffdio_writeprotect { + struct uffdio_range range; /* Range to change write permission */ + __u64 mode; /* Mode to change write permission */ +}; +.EE +.in +There're two modes that are supported in this structure: +.TP +.B UFFDIO_WRITEPROTECT_MODE_WP +When this mode bit is set, the ioctl will be a write-protect operation upon the +memory range specified by +.IR range . +Otherwise it'll be a write-unprotect operation upon the specified range. +.TP +.B UFFDIO_WRITEPROTECT_MODE_DONTWAKE +Do not wake up the thread that waits for page-fault resolution after the +operation. This could only be specified if +.B UFFDIO_WRITEPROTECT_MODE_WP +is not specified (in a resolving stage, not protecting stage). +.PP +This +.BR ioctl (2) +operation returns 0 on success. +On error, \-1 is returned and +.I errno +is set to indicate the error. +Possible errors include: +.TP +.B EINVAL +The +.I start +or the +.I len +field of the +.I ufdio_range +structure was not a multiple of the system page size; or +.I len +was zero; or the specified range was otherwise invalid. +.TP +.B EAGAIN +The process was interrupted and need to retry. +.TP +.B ENOENT +The range specified in +.I range +is not valid. E.g., the virtual address does not exist, or not registered with +userfaultfd write-protect mode. +.TP +.B EFAULT +Encountered a generic fault during processing. .SH RETURN VALUE See descriptions of the individual operations, above. .SH ERRORS