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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 65C4ACCFA1A for ; Tue, 11 Nov 2025 13:06:36 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BF94B8E0005; Tue, 11 Nov 2025 08:06:35 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id BA9B88E0002; Tue, 11 Nov 2025 08:06:35 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id ABF668E0005; Tue, 11 Nov 2025 08:06:35 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 9C1EA8E0002 for ; Tue, 11 Nov 2025 08:06:35 -0500 (EST) Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 3FE3E13B347 for ; Tue, 11 Nov 2025 13:06:35 +0000 (UTC) X-FDA: 84098350350.20.31E2A44 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf16.hostedemail.com (Postfix) with ESMTP id 9E551180009 for ; Tue, 11 Nov 2025 13:06:33 +0000 (UTC) Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=Tg0OtVLz; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf16.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1762866393; a=rsa-sha256; cv=none; b=3YFSV7iMSX6ZaTO21bBEunz3+153V7q6mEIhok350jsh5+gKpVRjriGwxqjaT5KXA8+4PM wdvBzvABM4vAR0KWSy8eW5TIkUHZM/mU7JT8fGs2B8v7VhsqD5lXoVzUr3DQeLtlzPIdlv 0biF+Zo3jW8j31u3bBH5BS7dOHduopE= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=Tg0OtVLz; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf16.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1762866393; 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=QUuxZIIuJ+7a2uOXKUVW8bGDd4sgEnQiZHeUL+8j6cI=; b=euZpEjPkjF667QKfEI+CpCUXXfXEQHORZ93Qf5swNJ0zcV9wwZNLr6CpFUHySNz/2J3pQz rrY0WkSsNUhrG2Wlgxby7cT6tMthl2sN8LmtCche6dOfVrtG3VdvpATZ3c9Z+oMmUhxHrX yHMoZFacHIYz8UPFnuY7Lx8hMRiJf5g= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id B15426190F; Tue, 11 Nov 2025 13:06:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A6E9AC16AAE; Tue, 11 Nov 2025 13:06:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762866392; bh=ahDE0Hde9+gZsnP0JCOLdJBo8hGroTd4JJCH/jgFj/0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Tg0OtVLz3wAXRZo7tCvWTInHjKpVK4LV67NTO+lYAZ/bR93jyG2IyFgcvsue4SRjB 0h8QMWesGpk3qXoW3f/y5g5hNGaIhpu5ZvQWDGwHfLvH2QohrLgDnSv/T7XK5D98wL z5paZ8OThivObxShM274wdwZcvtkA9PuAU6b+qI29fKv1akghKWsQ9OqLPjtgfb1tU 4dhW8r72DwTtl22M6htocWaDV7hTEh5uNlGrHZ2wikbz5TAqNJgsCaWZxjg5IGzZHl e2ra3fX+DjamK0ohLsg2Y80OH6UCT/oI2TuutGRfJ5NWGrLux815QwhhypwuSp+iZj JUT65tT6i+w6g== Message-ID: <6c7c5f86-a9d5-4b7e-aa08-968077f66ace@kernel.org> Date: Tue, 11 Nov 2025 14:06:10 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 02/16] mm: introduce leaf entry type and use to simplify leaf entry logic To: Zi Yan , Lorenzo Stoakes Cc: Andrew Morton , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Sven Schnelle , Peter Xu , Alexander Viro , Christian Brauner , Jan Kara , Arnd Bergmann , Baolin Wang , "Liam R . Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Muchun Song , Oscar Salvador , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Axel Rasmussen , Yuanchu Xie , Wei Xu , Kemeng Shi , Kairui Song , Nhat Pham , Baoquan He , Chris Li , SeongJae Park , Matthew Wilcox , Jason Gunthorpe , Leon Romanovsky , Xu Xin , Chengming Zhou , Jann Horn , Miaohe Lin , Naoya Horiguchi , Pedro Falcato , Pasha Tatashin , Rik van Riel , Harry Yoo , Hugh Dickins , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-s390@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, damon@lists.linux.dev References: From: "David Hildenbrand (Red Hat)" Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 9E551180009 X-Stat-Signature: dwcrnxjt4t1f1u54bd54jyb4qczjx649 X-HE-Tag: 1762866393-36146 X-HE-Meta: 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 unLdM6ba Vwh7iXTkiPtLzByeoSQ8BKaSYB8asUCUeySpDANimTyhC91fYc0OGfAFYKIu6SFAeh2A/BPabDYMH40aEcayJhqBtMP6A75it1KsekosXy2z7+duSelqn7AXmiD/KXeNH4zvqTLv8orhnsLMspHvdPF1XvyJ0MjucXyvQceAj9h9kTEh477ni/1XuSAAFSZ+vwfJKaox0ZztIZwfVcJkhQJogWLw+W/0DtgJtit3lkcBmOPTcqh0Rj3CuOsSMCJmlRgb8damzM6md00uR8wHuQQy+5WWU6sR++R0VQYTuFhk/nLJzsS3slsPQuNrXkkDcLc9RO6AXoCtfPgg= 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: List-Subscribe: List-Unsubscribe: On 11.11.25 04:25, Zi Yan wrote: > On 10 Nov 2025, at 17:21, Lorenzo Stoakes wrote: > >> The kernel maintains leaf page table entries which contain either: >> >> - Nothing ('none' entries) >> - Present entries (that is stuff the hardware can navigate without fault) > > This is not true for: > > 1. pXX_protnone(), where _PAGE_PROTNONE flag also means pXX_present() is > true, but hardware would still trigger a fault. > 2. pmd_present() where _PAGE_PSE also means a present PMD (see the comment > in pmd_present()). I'll note that pte_present/pmd_present etc is always about "soft-present". For example, if the hardware does not have a hw-managed access bit, doing a pte_mkyoung() would also clear the hw-valid/hw-present bit because we have to catch any next access done by hardware. [fun fact: some hardware has an invalid bit instead of a valid/present bit :) IIRC s390x falls into that category] Similar things happen on ordinary PROT_NONE of course (independent of pte_protnone). A better description might be "there is a page/pfn mapped here, but it might not be accessible by the CPU right now". We have device-exclusive/device-private nonswap (before this series) entries that fall into the same category, unfortunately ("there is something mapped there that is not accessible by the CPU") -- Cheers David