From patchwork Mon Mar 22 22:08:45 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Xu X-Patchwork-Id: 12156271 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 43432C433E0 for ; Mon, 22 Mar 2021 22:09:12 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id DCE4861879 for ; Mon, 22 Mar 2021 22:09:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DCE4861879 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 B15316B0116; Mon, 22 Mar 2021 18:09:10 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AC4DD6B0117; Mon, 22 Mar 2021 18:09:10 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 93E6B6B0119; Mon, 22 Mar 2021 18:09:10 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0154.hostedemail.com [216.40.44.154]) by kanga.kvack.org (Postfix) with ESMTP id 5707C6B0117 for ; Mon, 22 Mar 2021 18:09:10 -0400 (EDT) Received: from smtpin21.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 1704D8249980 for ; Mon, 22 Mar 2021 22:09:10 +0000 (UTC) X-FDA: 77948901660.21.F1FA5D1 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [63.128.21.124]) by imf11.hostedemail.com (Postfix) with ESMTP id D286220007C2 for ; Mon, 22 Mar 2021 22:08:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1616450936; 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=xTi7eK4FhauapOMog+x2j3yLdISM1j6yYqbUEE/lj8k=; b=RleaJcekkQC+lfHChgh+h3CIg+5nMjmnITCKyi+RJV96Y8vn4FUL/98vxoH7PDjCRcT3BQ atXAmxwZ0w9URjnOP05+AOInse9NlLmYSocyM3PjkvGlFUXcaXuKcUmwRDsyVNFu9wrumJ eDtNUBzkbsUKf8ZPJAVCwlXPh5nezus= Received: from mail-qt1-f198.google.com (mail-qt1-f198.google.com [209.85.160.198]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-466-c-Ei8C9nPBy8sWYbxW8AKQ-1; Mon, 22 Mar 2021 18:08:53 -0400 X-MC-Unique: c-Ei8C9nPBy8sWYbxW8AKQ-1 Received: by mail-qt1-f198.google.com with SMTP id d11so240641qth.3 for ; Mon, 22 Mar 2021 15:08:53 -0700 (PDT) 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=xTi7eK4FhauapOMog+x2j3yLdISM1j6yYqbUEE/lj8k=; b=uPiZj34eiUury4iVoeVAiFRN6YJEOK5dcRQrxuB2ueOoYqpPOolLuY1PanNLgcVE8Y OjyfyFOzSUuCbqNoOW6dHKHbejSdj3camH6rywshWas3E50/r5tXsWx2usC6ERsvQdEw 5rXN9EEpQgELeoXE2l1TsPgpeSorGfrW4xjJSb7a76PmY6CpWrUyMPN/zIRiG1LXOejH 86FopTUnfb6krd0S9QfCAgZG2DOYt6pV5hOLrOuGHF2ytZIEdcdZUX4EsOrDbfl8J/R8 9fPr3nqQNCSGysidFiCK4dekWH/ZgpiaPYTaNlkk0A76CWvq2u0vxL8UM81UStrsTvK+ 3ZiQ== X-Gm-Message-State: AOAM532fjUkin+nhAKaSvsaQA5FcQlR7vhjxhuFzksotYwy7yOOtsKV5 Ae8K/GG2UPtGZLPpDWuTcVWznXQVQxMw2WCPushGNcdEyRcREyuSRD4/NZLPmxykgcrHjjlknJW xLViR8tWExd0= X-Received: by 2002:a37:a54f:: with SMTP id o76mr2394698qke.95.1616450932649; Mon, 22 Mar 2021 15:08:52 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzvR5mojOQvg8OR/JFwX8IuACjNMK6k85LHvXAJT/PWMYtQY/hEXAcDMJRURNBcqov9dxUd3g== X-Received: by 2002:a37:a54f:: with SMTP id o76mr2394675qke.95.1616450932419; Mon, 22 Mar 2021 15:08:52 -0700 (PDT) Received: from xz-x1.redhat.com (bras-base-toroon474qw-grc-82-174-91-135-175.dsl.bell.ca. [174.91.135.175]) by smtp.gmail.com with ESMTPSA id x1sm9627850qtr.97.2021.03.22.15.08.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Mar 2021 15:08:51 -0700 (PDT) From: Peter Xu To: linux-man@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Andrea Arcangeli , Mike Rapoport , Axel Rasmussen , Alejandro Colomar , peterx@redhat.com, Michael Kerrisk , Nadav Amit , Andrew Morton Subject: [PATCH v4 1/4] userfaultfd.2: Add UFFD_FEATURE_THREAD_ID docs Date: Mon, 22 Mar 2021 18:08:45 -0400 Message-Id: <20210322220848.52162-2-peterx@redhat.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210322220848.52162-1-peterx@redhat.com> References: <20210322220848.52162-1-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: 4m6rugxe5dgbm8w6c54gptapho8g5zbj X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: D286220007C2 Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf11; 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: 1616450937-172556 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 | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/man2/userfaultfd.2 b/man2/userfaultfd.2 index e7dc9f813..555e37409 100644 --- a/man2/userfaultfd.2 +++ b/man2/userfaultfd.2 @@ -77,6 +77,13 @@ 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 faulting +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. +By default, thread ID reporting is diabled. .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 +236,9 @@ 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 +368,9 @@ 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 Mon Mar 22 22:08:46 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Xu X-Patchwork-Id: 12156275 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 A799DC433C1 for ; Mon, 22 Mar 2021 22:09:19 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4680861879 for ; Mon, 22 Mar 2021 22:09:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4680861879 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 C9C7A6B011A; Mon, 22 Mar 2021 18:09:18 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C24466B011C; Mon, 22 Mar 2021 18:09:18 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A79BA6B011D; Mon, 22 Mar 2021 18:09:18 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0242.hostedemail.com [216.40.44.242]) by kanga.kvack.org (Postfix) with ESMTP id 829CE6B011A for ; Mon, 22 Mar 2021 18:09:18 -0400 (EDT) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 3EEA5180255A9 for ; Mon, 22 Mar 2021 22:09:18 +0000 (UTC) X-FDA: 77948901996.03.C6AD81A Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by imf30.hostedemail.com (Postfix) with ESMTP id 72EC3E0011E3 for ; Mon, 22 Mar 2021 22:08:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1616450936; 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=OsBykH7rJZDyHmiXDUnOaeMRhfkxz6sA4fBXUYBd6g0=; b=eq5+cqCUjAmDHV6oa1csDKJT/6qZwp/4dUckV661Wk8XiOoSlgPFIp1R6+v1VwX7p2kBV7 RogzxJznU7EJBEOOutr4xtZr8haRf2uyJQS1uEuGNPh8oFtkqBTWWYKhef6CD53cpD0MC/ UMgHsVPzTfUANkPtdjzxmqVkVu3eJSU= Received: from mail-qv1-f70.google.com (mail-qv1-f70.google.com [209.85.219.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-557-hNCbQauMP1Gsj5vPWv2NbQ-1; Mon, 22 Mar 2021 18:08:55 -0400 X-MC-Unique: hNCbQauMP1Gsj5vPWv2NbQ-1 Received: by mail-qv1-f70.google.com with SMTP id k4so375655qvf.8 for ; Mon, 22 Mar 2021 15:08:54 -0700 (PDT) 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=OsBykH7rJZDyHmiXDUnOaeMRhfkxz6sA4fBXUYBd6g0=; b=THXOs7qeevb8N+Yw17d3yA9Pu8LOtNZQpm66xydlIWSfCZMv4faJ4fJfa7+xBVDdW4 QzgvFD2U+JO115iOD9SCDG3AsEZ1S+wxnQEjXvXBUXoKJqdy02XKZT1gk3TF2BlUzz1I tAmOwUXfD/52hRJmwwIy4hGn/XuGS5jtg2N/YDvMLMWlN0EFCcokd9SCY62XKOoVEqXo oMLIFjGSJjGJ9lkwI0aiLKzKFM+TDxpldxnWJlUXTVVEc82NjNkOGrnY6LtRdmjRYy2x lk7aq4S8d0dCl590Gl9/X+4Z8JYpvuFuCPky5T600Oiue5sRp6x8PJ5czoWjDj7Mo1RE zdog== X-Gm-Message-State: AOAM531uZgH4yHqAQ3oNsCQVJrG3agye1s8dBx9Ei/LebIdMyunvIEcX V3+VQ2pkEdoHSekYHc2IAvERt09gwpmZPGM2u+OznrO54WAHMU//oVZFm18RHHDQeAJPgupiusm Y799/8C2qNBo= X-Received: by 2002:a37:ef14:: with SMTP id j20mr2354868qkk.471.1616450934359; Mon, 22 Mar 2021 15:08:54 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwdNd7JnvxTCZHQOOSK2YFgFkS9VZ4sEhPpQHZKgxc0ZLk4kz5EmMkfsQezD0ATfy3Q2ZFLlw== X-Received: by 2002:a37:ef14:: with SMTP id j20mr2354842qkk.471.1616450934058; Mon, 22 Mar 2021 15:08:54 -0700 (PDT) Received: from xz-x1.redhat.com (bras-base-toroon474qw-grc-82-174-91-135-175.dsl.bell.ca. [174.91.135.175]) by smtp.gmail.com with ESMTPSA id x1sm9627850qtr.97.2021.03.22.15.08.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Mar 2021 15:08:53 -0700 (PDT) From: Peter Xu To: linux-man@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Andrea Arcangeli , Mike Rapoport , Axel Rasmussen , Alejandro Colomar , peterx@redhat.com, Michael Kerrisk , Nadav Amit , Andrew Morton Subject: [PATCH v4 2/4] userfaultfd.2: Add write-protect mode Date: Mon, 22 Mar 2021 18:08:46 -0400 Message-Id: <20210322220848.52162-3-peterx@redhat.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210322220848.52162-1-peterx@redhat.com> References: <20210322220848.52162-1-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: 72EC3E0011E3 X-Stat-Signature: fp5m3ftk5e9b5pcnp5mu33rj7jgwtump 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: 1616450937-521038 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 | 104 ++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 102 insertions(+), 2 deletions(-) diff --git a/man2/userfaultfd.2 b/man2/userfaultfd.2 index 555e37409..8ad4a71b5 100644 --- a/man2/userfaultfd.2 +++ b/man2/userfaultfd.2 @@ -78,6 +78,32 @@ all memory ranges that were registered with the object are unregistered and unread events are flushed. .\" .PP +Userfaultfd supports two modes of registration: +.TP +.BR UFFDIO_REGISTER_MODE_MISSING " (since 4.10)" +When registered with +.B 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 +.B UFFDIO_COPY +or an +.B UFFDIO_ZEROPAGE +ioctl. +.TP +.BR UFFDIO_REGISTER_MODE_WP " (since 5.7)" +When registered with +.B 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 +.B UFFDIO_WRITEPROTECT +ioctl. +.PP +Multiple modes can be enabled at the same time for the same memory range. +.PP Since Linux 4.14, userfaultfd page fault message can selectively embed faulting thread ID information into the fault message. One needs to enable this feature explicitly using the @@ -144,6 +170,17 @@ 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 refer to "Userfaultfd write-protect mode" section. .SS Userfaultfd operation After the userfaultfd object is created with .BR userfaultfd (), @@ -219,6 +256,65 @@ 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 5.7) +Since Linux 5.7, userfaultfd supports write-protect mode. +The user needs to first check availability of this feature using +.B UFFDIO_API +ioctl against the feature bit +.B UFFD_FEATURE_PAGEFAULT_FLAG_WP +before using this feature. +.PP +To register with userfaultfd write-protect mode, the user needs to initiate the +.B UFFDIO_REGISTER +ioctl with mode +.B 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 +.B UFFDIO_REGISTER +with the mode set to +.BR "UFFDIO_REGISTER_MODE_MISSING | UFFDIO_REGISTER_MODE_WP" . +When there is only +.B 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 +.B UFFDIO_REGISTER +ioctl completed with +.B UFFDIO_REGISTER_MODE_WP +mode set, +the user can write-protect any existing memory within the range using the ioctl +.B 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 +.B UFFD_PAGEFAULT_FLAG_WP +flag set. +Note: since only writes can trigger such kind of fault, +write-protect messages will always be with +.B UFFD_PAGEFAULT_FLAG_WRITE +bit set too along with bit +.BR UFFD_PAGEFAULT_FLAG_WP . +.PP +To resolve a write-protection page fault, the user should initiate another +.B UFFDIO_WRITEPROTECT +ioctl, whose +.I uffd_msg.pagefault.flags +should have the flag +.B UFFDIO_WRITEPROTECT_MODE_WP +cleared upon the faulted page or range. +.PP +Write-protect mode only supports private anonymous memory. .SS Reading from the userfaultfd structure Each .BR read (2) @@ -364,8 +460,12 @@ 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 Mon Mar 22 22:08:47 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Xu X-Patchwork-Id: 12156269 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 65FBEC433DB for ; Mon, 22 Mar 2021 22:09:11 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D2551619A9 for ; Mon, 22 Mar 2021 22:09:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D2551619A9 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 4D3206B0113; Mon, 22 Mar 2021 18:09:10 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 45A846B0116; Mon, 22 Mar 2021 18:09:10 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 287D56B0117; Mon, 22 Mar 2021 18:09:10 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0038.hostedemail.com [216.40.44.38]) by kanga.kvack.org (Postfix) with ESMTP id 09B526B0113 for ; Mon, 22 Mar 2021 18:09:10 -0400 (EDT) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id B49F3180AD83E for ; Mon, 22 Mar 2021 22:09:09 +0000 (UTC) X-FDA: 77948901618.16.D17F5D2 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf20.hostedemail.com (Postfix) with ESMTP id CADA3D5 for ; Mon, 22 Mar 2021 22:09:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1616450940; 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=BRu817/U099Z69O52DlP7850OjT0QzngDMzivy9vMy0=; b=h48XvD70Ytjv5kg8zR4NIxYbFacqZ6W2XI0g35M9aKIftZtvHvS2IClti2IOfT7Srrc2bC S40lOsYrlqLv0rXgkzQsNH9hIGC9XrpHVv8L5CXYBk9NDpFb2JzhqrYTnw/l1oTkZ6nYlW 2fQQvW3AYuMNCp3Uy60luqe95/hboTc= Received: from mail-qv1-f71.google.com (mail-qv1-f71.google.com [209.85.219.71]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-120-zCrHSFvqPcebC553TP0Fvg-1; Mon, 22 Mar 2021 18:08:56 -0400 X-MC-Unique: zCrHSFvqPcebC553TP0Fvg-1 Received: by mail-qv1-f71.google.com with SMTP id e10so357989qvr.17 for ; Mon, 22 Mar 2021 15:08:56 -0700 (PDT) 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=BRu817/U099Z69O52DlP7850OjT0QzngDMzivy9vMy0=; b=Ha2ZGNtCuiOMLMMnEvDEh32kHF2CCHSy2zbb20qi+JN0QUwP6F4Ba9QP5fXAEWEzlv wrKUn3iZngTMlmWyI7wFIOUGEG5twoHAUkHVxDbV1FpAlQsgbcwCZTlv2cou8sHwjWZ4 fe7bGgKaIrJcFQGEYdp0f9T1c/IA5URc4zHRIes/Z7oZBqTBQm54q4pXItlNnwoA1uPF 0a0CfF4sgFbN3CUxm17Q+3hXPGhK6WAA30kJ7GA48JygPLEKzmV07JBgOTE3UQrDHxhO sB5PBK2wrlgMRVMtgP2NmpJ5x9dC9XQ322Hs+S+F3beh0eJU2foFTZkpN2hZAtCICQ2+ DoWA== X-Gm-Message-State: AOAM533BvkbYsSfbaDzncu8gngOjuhFih2xSVQ1iztW6jR/k5cZ3mzSM r+u6fCiyPeQiwfVvbSEZC3vw9NjAvCRCodkArDRdAI4YMMm1qs+Qvrgmm+vzZJZPwqaavTSFkVo KZbQv6VU0dko= X-Received: by 2002:a0c:8365:: with SMTP id j92mr1838967qva.19.1616450935864; Mon, 22 Mar 2021 15:08:55 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwCbjzyxBUp80nxRyYOsjXe3EhMn6ViF263Myc1EobEUgW3DpX04+Jg+RKXYZDbze77kuVtcQ== X-Received: by 2002:a0c:8365:: with SMTP id j92mr1838955qva.19.1616450935685; Mon, 22 Mar 2021 15:08:55 -0700 (PDT) Received: from xz-x1.redhat.com (bras-base-toroon474qw-grc-82-174-91-135-175.dsl.bell.ca. [174.91.135.175]) by smtp.gmail.com with ESMTPSA id x1sm9627850qtr.97.2021.03.22.15.08.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Mar 2021 15:08:54 -0700 (PDT) From: Peter Xu To: linux-man@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Andrea Arcangeli , Mike Rapoport , Axel Rasmussen , Alejandro Colomar , peterx@redhat.com, Michael Kerrisk , Nadav Amit , Andrew Morton Subject: [PATCH v4 3/4] ioctl_userfaultfd.2: Add UFFD_FEATURE_THREAD_ID docs Date: Mon, 22 Mar 2021 18:08:47 -0400 Message-Id: <20210322220848.52162-4-peterx@redhat.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210322220848.52162-1-peterx@redhat.com> References: <20210322220848.52162-1-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: ri8x3ompuqmgukadek4t1jrothx6piw1 X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: CADA3D5 Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf20; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=170.10.133.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1616450945-610583 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 | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/man2/ioctl_userfaultfd.2 b/man2/ioctl_userfaultfd.2 index 47ae5f473..d4a8375b8 100644 --- a/man2/ioctl_userfaultfd.2 +++ b/man2/ioctl_userfaultfd.2 @@ -208,6 +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 to the faulted thread ID for each page fault message. .PP The returned .I ioctls From patchwork Mon Mar 22 22:08:48 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Xu X-Patchwork-Id: 12156277 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 B03F8C433DB for ; Mon, 22 Mar 2021 22:09:23 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 579D261879 for ; Mon, 22 Mar 2021 22:09:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 579D261879 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 E22AB6B011C; Mon, 22 Mar 2021 18:09:22 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id DAA606B011E; Mon, 22 Mar 2021 18:09:22 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BD6036B011F; Mon, 22 Mar 2021 18:09:22 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0250.hostedemail.com [216.40.44.250]) by kanga.kvack.org (Postfix) with ESMTP id 9D8246B011C for ; Mon, 22 Mar 2021 18:09:22 -0400 (EDT) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 5DDA5180AD83E for ; Mon, 22 Mar 2021 22:09:22 +0000 (UTC) X-FDA: 77948902164.27.D7DDBFD Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by imf28.hostedemail.com (Postfix) with ESMTP id 5022D200025F for ; Mon, 22 Mar 2021 22:09:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1616450940; 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=Kl3kFp9hTUBjJOfw0aybm+GM5kudzpR7W9bPcAyBKfY=; b=Z6GueklmOiNCehzKiT6ILQM0UP5W8SfomthfK2NMthFjrwi6A1sHje5h53QrrAxd64PRUT pPYMoK6NAZC1WFVtkxIyOJzvsYZuOWmNisqZVSOyq0tJJw6kodS51oAsQ/4RaHMG+09qps qshl/EFz32AWFLH4Q2TA8pcUdGeeCH8= Received: from mail-qt1-f197.google.com (mail-qt1-f197.google.com [209.85.160.197]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-29-lI6Zg6rAMkiI1tQ3nyL9BQ-1; Mon, 22 Mar 2021 18:08:58 -0400 X-MC-Unique: lI6Zg6rAMkiI1tQ3nyL9BQ-1 Received: by mail-qt1-f197.google.com with SMTP id c20so231222qtw.9 for ; Mon, 22 Mar 2021 15:08:58 -0700 (PDT) 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=Kl3kFp9hTUBjJOfw0aybm+GM5kudzpR7W9bPcAyBKfY=; b=QDzq75bUjxLNp01vdhVOVc1pVAyc4fIvRLNefrAttpVLcmOZ0ts2A0A8KWVFu0Yctv DDOEYJ5do3Uzx2S8iqvxAkKdAMqsVkWcge73aI952tgQTyws9NZRtt8NsNkkCHiz8cew qJAiOX5C6iyw2qhA/fnC4J2lH/pGQOGyvOgcXhEO9/w0gkFeK11XPaUnDGBrbRrK8IHk 6m2UWP1H2r7d+u6WbBGc9HxSQc6xyj/cWzk3uPe77I3CALthn7axYEP6ckFEtTTpJWWV l1JBExfOnihz5Xy2xt3P/8Wg7fAALO5+XR7vNPyTDGkx4o0CUf4y8BwuApWnu5dBKe4S MTZg== X-Gm-Message-State: AOAM532i22fry26DFr5aBNsZ/oq15YAthKwG2KckQWgMJk2fmqE3gWn0 E+Lder2o2me9Q+c3pCEM/pMk8C7wNuEgbp7sp/Sp7WlqJRwyLqIdMwGxdPtDwx+mERO6pb1+JkY 3/Kb+mL5Wf3Q= X-Received: by 2002:a05:620a:218e:: with SMTP id g14mr2318822qka.111.1616450937655; Mon, 22 Mar 2021 15:08:57 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxXQkjDlpEzfKxL2gVD4fm1+ph4tlOJXa1UzW5utW+yxjYVJwWLncDAwiuahCmShRLGbvdPJw== X-Received: by 2002:a05:620a:218e:: with SMTP id g14mr2318803qka.111.1616450937365; Mon, 22 Mar 2021 15:08:57 -0700 (PDT) Received: from xz-x1.redhat.com (bras-base-toroon474qw-grc-82-174-91-135-175.dsl.bell.ca. [174.91.135.175]) by smtp.gmail.com with ESMTPSA id x1sm9627850qtr.97.2021.03.22.15.08.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Mar 2021 15:08:56 -0700 (PDT) From: Peter Xu To: linux-man@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Andrea Arcangeli , Mike Rapoport , Axel Rasmussen , Alejandro Colomar , peterx@redhat.com, Michael Kerrisk , Nadav Amit , Andrew Morton Subject: [PATCH v4 4/4] ioctl_userfaultfd.2: Add write-protect mode docs Date: Mon, 22 Mar 2021 18:08:48 -0400 Message-Id: <20210322220848.52162-5-peterx@redhat.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210322220848.52162-1-peterx@redhat.com> References: <20210322220848.52162-1-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: 5022D200025F X-Stat-Signature: jigwjmo386fq7ct1m3e5u41ychazmcf5 Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf28; 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: 1616450941-830728 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 | 84 ++++++++++++++++++++++++++++++++++++++-- 1 file changed, 81 insertions(+), 3 deletions(-) diff --git a/man2/ioctl_userfaultfd.2 b/man2/ioctl_userfaultfd.2 index d4a8375b8..5419687a6 100644 --- a/man2/ioctl_userfaultfd.2 +++ b/man2/ioctl_userfaultfd.2 @@ -234,6 +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) @@ -322,9 +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 @@ -443,6 +445,16 @@ operation: .TP .B UFFDIO_COPY_MODE_DONTWAKE Do not wake up the thread that waits for page-fault resolution +.TP +.B UFFDIO_COPY_MODE_WP +Copy the page with read-only permission. +This allows the user to trap the next write to the page, +which will block and generate another write-protect userfault message. +This is only used when both +.B UFFDIO_REGISTER_MODE_MISSING +and +.B UFFDIO_REGISTER_MODE_WP +modes are enabled for the registered range. .PP The .I copy @@ -654,6 +666,72 @@ 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) +Write-protect or write-unprotect an userfaultfd registered memory range +registered 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 mode bits 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, +which can be used to resolve an userfaultfd write-protect page fault. +.TP +.B UFFDIO_WRITEPROTECT_MODE_DONTWAKE +When this mode bit is set, +do not wake up any thread that waits for page-fault resolution after the operation. +This could only be specified if +.B UFFDIO_WRITEPROTECT_MODE_WP +is not specified. +.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. +For example, 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