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 ED041C54F51 for ; Wed, 29 Jul 2026 14:44:20 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id F33A76B00F8; Wed, 29 Jul 2026 10:44:19 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id F0AFB6B00FC; Wed, 29 Jul 2026 10:44:19 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E20486B010B; Wed, 29 Jul 2026 10:44:19 -0400 (EDT) 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 AC1436B00F8 for ; Wed, 29 Jul 2026 10:44:19 -0400 (EDT) Received: from smtpin12.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 26FED16066E for ; Wed, 29 Jul 2026 11:05:51 +0000 (UTC) X-FDA: 85041534102.12.060611C Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf31.hostedemail.com (Postfix) with ESMTP id 6C6B12000F for ; Wed, 29 Jul 2026 11:05:49 +0000 (UTC) Authentication-Results: imf31.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=b48irzvs; spf=pass (imf31.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1785323149; 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=36vCc8VcM+L87TfsrGnoD5hR3X1siACB/VnlnYWIbd4=; b=Z0h6rrxDg28r+0WDaKTnosI1eBkK/6gXxNosvc+IXFrv3BvyqUTwKzyCsQE+jvn+3AsUKM JGAyZIvAsZWtY9DnwejW3XteBIAJ+y9pKNWkyHdc6jBYznY9bmXEPa2YDsnfufZfNYoO9p zQLGpdtUvvd1M1fl5b53s0gecLOTOMM= ARC-Authentication-Results: i=1; imf31.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=b48irzvs; spf=pass (imf31.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1785323149; b=44MRTRMMsGgIb3u/M1f6xSXzjRjhU8YbicG6k7c0OoAQJaXfQkjJFJ4cAB84jA3sPioGI0 5TdNBm7LJapDkrGKSjBkdXS5rotuszejr0ww0paoidSApFFTaDgvFaRR9AWoBZmkihoBoW kFdP+8ggs9x5ra4P9KNDcrBpCoSR7S8= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 3BCDE60A5E; Wed, 29 Jul 2026 11:05:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A9E6C1F000E9; Wed, 29 Jul 2026 11:05:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785323147; bh=36vCc8VcM+L87TfsrGnoD5hR3X1siACB/VnlnYWIbd4=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=b48irzvsg0Rb9HPmpRz1cRt988CITLctIsdsmAzYoCGHcqqDXZ2gNYuTnHHIrJbj7 4H2B2eH12UqMFJgYMLsCy1KZ8q4b7/HtBh+ESujT8zNC3k4hQqfRfj+yc+rkURzE4h 70Dn1hj1howXlSwenX2dUF2/DWVG876GsmhZQP8m1Dia942tWYnyC3PKB5EAolTNmB CONyTksT7fwOidO2ekfK6pe1uDUU/xaLuhg3IVs/5z07rdUbVvn8YGTImADEAyTk9V +kH3OunfyfncZZV5MjIcpVdG3+JC+QgBBibA6vztnHMkc1m9JC4YLICz4dpEmla0Jm pExAKbv9xiF0g== Message-ID: <6db0a8c0-b500-4364-be3d-d3a537c61258@kernel.org> Date: Wed, 29 Jul 2026 13:05:35 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC 00/11] mm: distinguish PTE table storage from PTE values To: Alexander Gordeev Cc: Muhammad Usama Anjum , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Simona Vetter , Dimitri Sivanich , Arnd Bergmann , Greg Kroah-Hartman , "James E.J. Bottomley" , Helge Deller , Juergen Gross , Stefano Stabellini , Muchun Song , Oscar Salvador , Andrew Morton , "Liam R. Howlett" , Lorenzo Stoakes , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Peter Zijlstra , Andrey Ryabinin , Pasha Tatashin , Chris Li , Kairui Song , Uladzislau Rezki , Steven Rostedt , Masami Hiramatsu , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , SJ Park , "Matthew Wilcox (Oracle)" , Jan Kara , Jason Gunthorpe , Leon Romanovsky , Miaohe Lin , Dennis Zhou , Tejun Heo , Christoph Lameter , Mike Rapoport , Johannes Weiner , ziy@nvidia.com, pfalcato@suse.de, ryan.roberts@arm.com, linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-parisc@vger.kernel.org, xen-devel@lists.xenproject.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, kasan-dev@googlegroups.com, linux-trace-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-perf-users@vger.kernel.org, damon@lists.linux.dev References: <20260727164715.2866609-1-usama.anjum@arm.com> <2c19247e-bee6-45f4-a353-2fcc60db26e6@kernel.org> <7813b5fe-e767-442c-a356-afc1a5c567ad-agordeev@linux.ibm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: 6C6B12000F X-Rspamd-Server: rspam01 X-Stat-Signature: erkb65a9fxy9whhotmipaudap6ne5mph X-HE-Tag: 1785323149-903983 X-HE-Meta: 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 zgatMgb/ 8mMb9oJt77+hErBe+M1pmCT51BzDo4SeAQbw1PcNMM88vF9kSSse+CCk50jWMAYhwoy0/Aq7919VzGiGpzZurf5luU8vF4lNhyDCIM9nbkShh9ErfnfuTKbl1IwBAVSajYR9Zu+bn6TFswmXESqFC9n6jrguoa+4C1z5zgrd/UY77NJUoiF+4Z1CEnejyYELsdr1W89w8LgwAeDQpD+uQTk/BHGU8PN1f3JHKxyJBDYqiVdh4CMvPvgm6J/ycoyc1uPr7hUaZWLKnlsWBT0IlaVxQ2elAjSVZ3FRWVDvahQDi//GvEXcWukXj8lzZHQQyFRy0sRI1TThZnFk= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/29/26 12:13, Alexander Gordeev wrote: > On Tue, Jul 28, 2026 at 09:26:06PM +0200, David Hildenbrand (Arm) wrote: >>> The generic definition aliases hw_pte_t to pte_t, so this series preserves >>> the representation and behaviour of every architecture. ptep_get() keeps >>> its existing READ_ONCE() semantics and converts the stored element through >>> __pte_from_hw(). An architecture can later define a distinct hw_pte_t and >>> convert its PTE interfaces to make the distinction compiler-enforced. >>> Architecture PTE implementations and most architecture code are >>> deliberately left for those later opt-in conversions. > ... >> Do you have a pointer at the arm64 part, so people can get a feeling for how an >> actual hw_pte_t implementation can look like. > > May be we need the generic hw_pte_t implementation as { pte_t pte; } > right away? Indeed, that makes sense. We just need a way for the architecture to opt-in that it did the conversion. > > Also, can you envision a case when sizeof(pte_t) != sizeof(hw_pte_t)? > If not, the compile-time check is worth adding. That wouldn't work as is. We'd have to intercept ptep++ and instead have a helper to advance the ptep pointer. One idea for that would be to let the compiler catch that by marking hw_pte_t an undefined struct (unknown size), such that the compiler would indicate any usage of ptep++ properly. That can be done when it would actually required, so as a first step having a generic hw_pte_t would just work. -- Cheers, David