From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id C75C3C021B3 for ; Mon, 24 Feb 2025 09:27:38 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E96446B007B; Mon, 24 Feb 2025 04:27:37 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E20236B0083; Mon, 24 Feb 2025 04:27:37 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C4BDA6B0085; Mon, 24 Feb 2025 04:27:37 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id A72876B007B for ; Mon, 24 Feb 2025 04:27:37 -0500 (EST) Received: from smtpin05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 56B1E160F9F for ; Mon, 24 Feb 2025 09:27:37 +0000 (UTC) X-FDA: 83154310554.05.3DD5631 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf29.hostedemail.com (Postfix) with ESMTP id CFFB2120012 for ; Mon, 24 Feb 2025 09:27:34 +0000 (UTC) Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=SJxGMmQx; spf=pass (imf29.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1740389254; h=from:from:sender: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:dkim-signature; bh=7Zn6SZZblvU2KN6afeUfX6cSk2JfetNjQceFn+mshcA=; b=e4n7rSLJdxB4RewzkgY3GwM08fqruEUILrS/Dp8oG+wcfEvPZKTKA9s2xc7zmUq4B0cAVE uFkCgYMDh+KuEDcHrYlPXQXcZzC4C5R5qq0F1myRWoOvwZdF7tH5MB5fKh01bQ74DokvEM FLzuPSxzsqpfWh3b/uJX0GuYoT6q2q8= ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=SJxGMmQx; spf=pass (imf29.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1740389254; a=rsa-sha256; cv=none; b=dYSeOQR93tXLd4aHpnfAOEbZzoeLfqorskwUj29vWtJLhSVT3C3mnHIu0poNhm6hAzPGS9 ODisWcZmwjNosKO8X0OcaLAu3tyboNGo+pHwZ7EjhHL9pldFTfxww+T4uTPjWJsz0XfptB 8CdjIZy/hQC2d/21awxQl0txXVV0t+c= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1740389254; 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:autocrypt:autocrypt; bh=7Zn6SZZblvU2KN6afeUfX6cSk2JfetNjQceFn+mshcA=; b=SJxGMmQxPEZqkSp8d52n1bsCEjk6aWGXiL8xOaVmVwd50eHBT1UqVAOt0IpRSqGwhwTUJo SEoq5xLuGWdPO5D9VuhNV5faP4g2ua3dq+yGWHFrpWKeoBZ9TFvoUcH1BVgzkF9M+Vx6N3 zoSt3Of++JSGeBAqd/ZZWWgFaypBL3I= Received: from mail-wr1-f70.google.com (mail-wr1-f70.google.com [209.85.221.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-632-kinuo28jNs6GjYWWlYEoYw-1; Mon, 24 Feb 2025 04:27:32 -0500 X-MC-Unique: kinuo28jNs6GjYWWlYEoYw-1 X-Mimecast-MFC-AGG-ID: kinuo28jNs6GjYWWlYEoYw_1740389251 Received: by mail-wr1-f70.google.com with SMTP id ffacd0b85a97d-38f39352f1dso1524835f8f.0 for ; Mon, 24 Feb 2025 01:27:32 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1740389251; x=1740994051; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:cc:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=7Zn6SZZblvU2KN6afeUfX6cSk2JfetNjQceFn+mshcA=; b=pHb8b1ti8IicsBO+utw/SEBA6Xd+2nd3hbAKzqw34cWrt4kcFEYttk6QHLkyl73D5H skztGp1yHNR+3yNwxZ0T75y5laGDmOrPlpCoTYofIK73AgbsqhyKBBx7tSuldJmixvkz rEen1PDkzBctik89lKYZ4+3ijOOQ946jufnkP6pTyFsJiqFpoPMYYGI/99W4ArCR4spK jEl1dSOkoC4XGWSzUUmOFsLTMzvZ02ognBlyuARqjfT3KeR5oEK8EzQjiXGBpxWObVpm KxbAbh+69QU15csZQkQu5vzVd5GuR1EJeU5YEN4gTebqPG6GbA3KV5vyfe9RhNU8+RsB l3Mg== X-Forwarded-Encrypted: i=1; AJvYcCW/dzgb+fvBJ8TWrh+ZwdN69m4aEXq1D7f0acqTGtZVtlzbLygadk1YpwQHSpRM8IT5rpg3JSRg4Q==@kvack.org X-Gm-Message-State: AOJu0YwwJeuSOHm2HFI8NbC6NOhcySgtOdhG5yb+u9wxxwPZpVj/Vy8P knfHqwjlR6IpR2lWPXsYAVfbNMnqsokwshNsjfibbcHByJjfFmC6z5h5RGsa+nhPZzdf74kMeoT qpyOxLQC/rXzulxVmDggIbyatJllEiSl9+Zv9n/mwYDbzjn+a X-Gm-Gg: ASbGnctHP7rRM8fyCSFCAXbBzbT9DjZW065pvhF+ANPi2E0X5XTsNea+569MbbmwSR4 21c4/3Xj6L1iOrzTOD3fpVLvnVJ66bWKOmxx7FiNfsrnL/vA/W4+kCXHraRDBLYbo+KIkGn0TIi A5dpfR7C1GbMm3KO3hznxFWVAzl5Gr8faWEZULqtsnJSht2XK8htb1d51kRbG2ig4J6YYN3J7kY MAk3gp8z1wywg/7g8sUAeGbsqtWjlY2vM36sYMtAhpoqMuLezbSbBc1W/RO62nS0ouijmgfT7Ez va8RNVgaT3WwnUnIeC7tu7v+8M/Jsz0rZ/QkRpXM6zT9fg/gGhQXfTuKOAT4quSsgtlDnV2OqIU QUBNg4DZn1RfuSprwt1klz3kqeJeQrHSQtRRu/n2BodQ= X-Received: by 2002:a5d:59a7:0:b0:38d:e304:7478 with SMTP id ffacd0b85a97d-38f7082b185mr12874186f8f.38.1740389251248; Mon, 24 Feb 2025 01:27:31 -0800 (PST) X-Google-Smtp-Source: AGHT+IE5HbPThRylS4ilKU1oY0b9sapnTNZTmqh2oQkysSGqBLm2fMAB+eMOTjT2FNPL02czMER6nQ== X-Received: by 2002:a5d:59a7:0:b0:38d:e304:7478 with SMTP id ffacd0b85a97d-38f7082b185mr12874144f8f.38.1740389250835; Mon, 24 Feb 2025 01:27:30 -0800 (PST) Received: from ?IPV6:2003:cb:c735:1900:ac8b:7ae5:991f:54fc? (p200300cbc7351900ac8b7ae5991f54fc.dip0.t-ipconnect.de. [2003:cb:c735:1900:ac8b:7ae5:991f:54fc]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38f25a0fa38sm31629174f8f.98.2025.02.24.01.27.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 24 Feb 2025 01:27:30 -0800 (PST) Message-ID: <857b2c3f-7be7-44e8-a825-82a7353665fb@redhat.com> Date: Mon, 24 Feb 2025 10:27:28 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] fs/proc/task_mmu: add guard region bit to pagemap To: Lorenzo Stoakes , Andrew Morton Cc: Jonathan Corbet , Shuah Khan , Suren Baghdasaryan , Kalesh Singh , "Liam R . Howlett" , Matthew Wilcox , Vlastimil Babka , "Paul E . McKenney" , Jann Horn , Juan Yescas , linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org References: <521d99c08b975fb06a1e7201e971cc24d68196d1.1740139449.git.lorenzo.stoakes@oracle.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <521d99c08b975fb06a1e7201e971cc24d68196d1.1740139449.git.lorenzo.stoakes@oracle.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: kc-wxF-GEoYJhb8HvTlz_KrodcPW5OwhmjPy7WBpl6U_1740389251 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: CFFB2120012 X-Stat-Signature: sg11bkjzdqikrb7fnwot1afpn5kmf156 X-HE-Tag: 1740389254-101975 X-HE-Meta: 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 krE4PQG3 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 21.02.25 13:05, Lorenzo Stoakes wrote: > Currently there is no means by which users can determine whether a given > page in memory is in fact a guard region, that is having had the > MADV_GUARD_INSTALL madvise() flag applied to it. > > This is intentional, as to provide this information in VMA metadata would > contradict the intent of the feature (providing a means to change fault > behaviour at a page table level rather than a VMA level), and would require > VMA metadata operations to scan page tables, which is unacceptable. > > In many cases, users have no need to reflect and determine what regions > have been designated guard regions, as it is the user who has established > them in the first place. > > But in some instances, such as monitoring software, or software that relies > upon being able to ascertain the nature of mappings within a remote process > for instance, it becomes useful to be able to determine which pages have > the guard region marker applied. > > This patch makes use of an unused pagemap bit (58) to provide this > information. > > This patch updates the documentation at the same time as making the change > such that the implementation of the feature and the documentation of it are > tied together. > > Signed-off-by: Lorenzo Stoakes > --- Acked-by: David Hildenbrand Something that might be interesting is also extending the PAGEMAP_SCAN ioctl. See do_pagemap_scan(). The benefit here might be that one could effectively search/filter for guard regions without copying 64bit per base-page to user space. But the idea would be to indicate something like PAGE_IS_GUARD_REGION as a category when we hit a guard region entry in pagemap_page_category(). (the code is a bit complicated, and I am not sure why we indicate PAGE_IS_SWAPPED for non-swap entries, likely wrong ...) -- Cheers, David / dhildenb