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 8F5EFC83F05 for ; Sun, 6 Jul 2025 09:14:08 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id F02AF6B03F7; Sun, 6 Jul 2025 05:14:07 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id EB2E96B03F8; Sun, 6 Jul 2025 05:14:07 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DA0CF6B03F9; Sun, 6 Jul 2025 05:14:07 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id BE8EB6B03F7 for ; Sun, 6 Jul 2025 05:14:07 -0400 (EDT) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 0B81A12E80E for ; Sun, 6 Jul 2025 09:14:07 +0000 (UTC) X-FDA: 83633278134.23.08F7A59 Received: from mail-wm1-f45.google.com (mail-wm1-f45.google.com [209.85.128.45]) by imf14.hostedemail.com (Postfix) with ESMTP id 0B694100008 for ; Sun, 6 Jul 2025 09:14:04 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=eqjjXwBC; spf=pass (imf14.hostedemail.com: domain of david.laight.linux@gmail.com designates 209.85.128.45 as permitted sender) smtp.mailfrom=david.laight.linux@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=eqjjXwBC; spf=pass (imf14.hostedemail.com: domain of david.laight.linux@gmail.com designates 209.85.128.45 as permitted sender) smtp.mailfrom=david.laight.linux@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1751793245; a=rsa-sha256; cv=none; b=0dsscH5HqElZQo+u3E1zhfrOOLsfAWe87nzM/TgC+VFJ5LBy27BD58Mscdz6y9V/CiLkQs gRKJMNMYfEoSlyfBFNHGKMfM5dCvg+ITEBaQZI/54dyfaHsNO3uRdH3Mm/Nw/xTxjMRMad z4BOp60TGFIoXhtPTN74vtS47vtlAqA= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1751793245; 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=q8hlSgBV1+bYygrl+ZccylfC3/K7ixgrATl9jQwn0YA=; b=pTWwbLYqoFAUyCgbGHfalyZMQKuu38Z/a/Y9z/m0DkQSxBDmQyYYHCXp/vJ51BmXS+rxcl tAyB5a7LFP4NSnAu33qdiz1D/ZwwstPOHh6WOvwb+qYuEud/CgkuSduWxpfhgcIJnaeHYk 0QW4QDZyw1FR5UPz7V3tknZ7fsJOgVQ= Received: by mail-wm1-f45.google.com with SMTP id 5b1f17b1804b1-451d6ade159so17727555e9.1 for ; Sun, 06 Jul 2025 02:14:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1751793243; x=1752398043; darn=kvack.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:from:to:cc:subject:date :message-id:reply-to; bh=q8hlSgBV1+bYygrl+ZccylfC3/K7ixgrATl9jQwn0YA=; b=eqjjXwBCBSybBu2MCIaZ3/5Jejngj3xav5YHnGR1VyeUq0nCeG1rQ2XihXIFTwecSb 3Na8Fzij38Lx0CXLXW5zHthVwZIpJlOCcTDAy7TQLI72NLONYL75Mxhv25sQUJn1L+tV 3ifJwA7AtsGtg3FNV6SI+aOKrrlqMRJcDeU52vBYvL6rX2JYTAynoQvv+YCh7s5cWHPu XuL79aj8yHkKs/Fz0jzcpJVchERX1pH+mtzEmsrM63zJ2l396f/HHQsSpMeJQJIUKzRX KR+qsJV45Aja2T6JorKPWIQLrU/tb0+LzR+f3iU5hcGVUQqWZXAt9/nr+I5nrNA5Tj+i Ay2A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1751793243; x=1752398043; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=q8hlSgBV1+bYygrl+ZccylfC3/K7ixgrATl9jQwn0YA=; b=G8OgLRXhJ13RW2OR+7cjctHdZ4coGzkW5ISK/7WbX+8J53kUwVJErxRTOjK61eJdcC UpEJjdHB63p2/QLT/G7ivwH1nH9a5Ys71vVX07ZcB5dDQ/7nS7Zipp9RYqfmIKp4qADR VhE4pYhjUjS9PV9pdpU4Wdqio6+MGSWn2ji3OMtowTRZ4/9TutFH6g1JGL6qlUorZiwj CYWqXRxvl6P3UfvpIOkbfANYh0ZYdvS7yNjCPhrLTfhuXY2sHzmmPo2gi5Kag95GiRFP bvrB59uN6EwTWjFQEM8ZRvLazW9OArqDlTlfuCwTRnXekmjUSx7fuCHyNdMXYdtHKSoq by1A== X-Forwarded-Encrypted: i=1; AJvYcCVWj1ZCpzOB+WxKNVWuzXCEtbLwyJ9DzwhVNoYgmLD9EH30V3rdGXcS37OCYHC1t3hiyQ+6yDT5ng==@kvack.org X-Gm-Message-State: AOJu0Yxb8pGxbd/IQVuMQjdfQmF3sO8JUIe8eqK45mh74LuCWbynr4I2 29v/MtBksIluEPHpkEd7EEF/KWeew/zMz98nF84o+TUVlNJa0jegkTPv X-Gm-Gg: ASbGncuzcF6vNhRvI3z7GNpXWBavGUGuTvmjqdLn2oNajJTZQWd4I00L5bpjObtoQcj WR8SMp6sKjXTdHwUTjkohgwMhvtX2qKUSv6Iuf7Ub9vZoYpJCwhkR+zWI1S3D2FgxIM+Dv5IM+3 mh34BSiZok6em2vTk1TSOQASFczQs9c5w5+KC5TilezW2wzcBnf2tppHKp9SgswYyUoTPfpRMbE LHyQjwpVV07LEH6pSZJVHf+9M67DcWr6ojhXd0uJEalhPZif/zY3YUziDJ1tOnyYpQdOhQTkOUu 55EwRvAtJLzqm+OCBngFVWF/zuTiln1/jG6WOMlKimGDUyi8PP3507NKeEv6T5G+lB+JV3lhlAm JnAUQ0vLaCbp4733ohg== X-Google-Smtp-Source: AGHT+IE/TXS+sz7Mby0dfZERmdqKJhVpm0cyrlWbJ+f/VwJHOVGQVE9NJpn97WFCi+JJaWJyaqs25w== X-Received: by 2002:a05:600c:4f45:b0:43d:abd:ad1c with SMTP id 5b1f17b1804b1-454b4e6849dmr63131615e9.6.1751793243088; Sun, 06 Jul 2025 02:14:03 -0700 (PDT) Received: from pumpkin (host-92-21-58-28.as13285.net. [92.21.58.28]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-454b1695577sm76992715e9.27.2025.07.06.02.14.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 06 Jul 2025 02:14:02 -0700 (PDT) Date: Sun, 6 Jul 2025 10:13:42 +0100 From: David Laight To: Dave Hansen Cc: "Kirill A. Shutemov" , Andy Lutomirski , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Ard Biesheuvel , "Paul E. McKenney" , Josh Poimboeuf , Xiongwei Song , Xin Li , "Mike Rapoport (IBM)" , Brijesh Singh , Michael Roth , Tony Luck , Alexey Kardashevskiy , Alexander Shishkin , Jonathan Corbet , Sohil Mehta , Ingo Molnar , Pawan Gupta , Daniel Sneddon , Kai Huang , Sandipan Das , Breno Leitao , Rick Edgecombe , Alexei Starovoitov , Hou Tao , Juergen Gross , Vegard Nossum , Kees Cook , Eric Biggers , Jason Gunthorpe , "Masami Hiramatsu (Google)" , Andrew Morton , Luis Chamberlain , Yuntao Wang , Rasmus Villemoes , Christophe Leroy , Tejun Heo , Changbin Du , Huang Shijie , Geert Uytterhoeven , Namhyung Kim , Arnaldo Carvalho de Melo , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCHv8 02/17] x86/asm: Introduce inline memcpy and memset Message-ID: <20250706101342.069b5068@pumpkin> In-Reply-To: <49f7c370-1e28-494b-96a9-f45e06ed4631@intel.com> References: <20250701095849.2360685-1-kirill.shutemov@linux.intel.com> <20250701095849.2360685-3-kirill.shutemov@linux.intel.com> <49f7c370-1e28-494b-96a9-f45e06ed4631@intel.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 0B694100008 X-Stat-Signature: ds9fhmzb5f7esfyh5fjpjwesameepp7i X-Rspam-User: X-HE-Tag: 1751793244-924904 X-HE-Meta: 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 LX9n+xB3 7iFAVydOamPtKFb+USVa82IxhewoVkwiFrQoxspfjOztg8q4xi3VT+gvodO4UrFCVExXiEDosaCKleMuERrUw8T9zlUdkea/1MXUF5f2YAiXJPystLdch5of4YPGeL35uDuDmzWu1OiZ2j5y3rzDW7K8qxCxie5he4k6wnJtS0FrDJDp2X5RG5ZFePtYzJkEOA4Lx91h1G5H3Sh0rBlB5YSWM3CA8qWVzlcyXmy1mzp8riLe3eeT2C4+edFusdCi+OKGcxBOqbNC5agshxM/RQg/jWjQbYQz+4dVuPAz/aDNYpLk8f+b7GIvgqvrR42p49Z5zkVjd7wFcuRWfPDe+S1xkh4EQ1JUAD1mrJxPQEfPy3VILt9aPXj6nxz7l/zhr6ulmJayPFMqZ5m1g+JolgyN5l7AQL6BezTYx6X13v1f9n+T2iAopxOWYf3gKxZfFjJ2zbofz4IAgMxuv6DfGUZDlwLyb7XLREs2BYMQG6rIJHoI= 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 Thu, 3 Jul 2025 10:13:44 -0700 Dave Hansen wrote: > On 7/1/25 02:58, Kirill A. Shutemov wrote: > > Extract memcpy and memset functions from copy_user_generic() and > > __clear_user(). > > > > They can be used as inline memcpy and memset instead of the GCC builtins > > whenever necessary. LASS requires them to handle text_poke. > > Why are we messing with the normal user copy functions? Code reuse is > great, but as you're discovering, the user copy code is highly > specialized and not that easy to reuse for other things. > > Don't we just need a dirt simple chunk of code that does (logically): > > stac(); > asm("rep stosq..."); > clac(); > > Performance doesn't matter for text poking, right? It could be stosq or > anything else that you can inline. It could be a for() loop for all I > care as long as the compiler doesn't transform it into some out-of-line > memset. Right? > It doesn't even really matter if there is an out-of-line memset. All you need to do is 'teach' objtool it isn't a problem. Is this for the boot-time asm-alternatives? In that case I wonder why a 'low' address is being used? With LASS enabled using a low address on a life kernel would make it harder for another cpu to leverage the writable code page, but that isn't a requirement of LASS. If it is being used for later instruction patching you need the very careful instruction sequences and cpu synchronisation. In that case I suspect you need to add conditional stac/clac to the existing patching code (and teach objtool it is all ok). David