[{"id":3682938,"web_url":"http://patchwork.ozlabs.org/comment/3682938/","msgid":"","list_archive_url":null,"date":"2026-04-27T20:12:55","subject":"Re: [RFC PATCH v1 9/9] uaccess: Convert small fixed size\n copy_{to/from}_user() to scoped user access","submitter":{"id":92516,"url":"http://patchwork.ozlabs.org/api/people/92516/","name":"Yury Norov","email":"ynorov@nvidia.com"},"content":"On Mon, Apr 27, 2026 at 07:13:50PM +0200, Christophe Leroy (CS GROUP) wrote:\n> copy_{to/from}_user() is a heavy function optimised for copy of large\n> blocs of memory between user and kernel space.\n> \n> When the number of bytes to be copied is known at build time and small,\n> using scoped user access removes the burden of that optimisation.\n> \n> Signed-off-by: Christophe Leroy (CS GROUP) \n> ---\n> include/linux/uaccess.h | 47 +++++++++++++++++++++++++++++++++++++++++\n> 1 file changed, 47 insertions(+)\n> \n> diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h\n> index 33b7d0f5f808..3ac544527af2 100644\n> --- a/include/linux/uaccess.h\n> +++ b/include/linux/uaccess.h\n> @@ -50,6 +50,8 @@\n> #define mask_user_address(src) (src)\n> #endif\n> \n> +#define SMALL_COPY_USER\t\t64\n\nLet's make it L1_CACHE_BYTES, and maybe configurable?","headers":{"Return-Path":"\n ","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n secure) header.d=lists.infradead.org header.i=@lists.infradead.org\n header.a=rsa-sha256 header.s=bombadil.20210309 header.b=TqIz00UY;\n\tdkim=fail reason=\"signature verification failed\" (2048-bit key;\n unprotected) header.d=Nvidia.com header.i=@Nvidia.com header.a=rsa-sha256\n header.s=selector2 header.b=hMJCquiW;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=none (no SPF record) smtp.mailfrom=lists.infradead.org\n (client-ip=2607:7c80:54:3::133; helo=bombadil.infradead.org;\n envelope-from=linux-snps-arc-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org;\n receiver=patchwork.ozlabs.org)","dkim=none (message not signed)\n header.d=none;dmarc=none action=none header.from=nvidia.com;"],"Received":["from bombadil.infradead.org (bombadil.infradead.org\n [IPv6:2607:7c80:54:3::133])\n\t(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)\n\t key-exchange x25519 server-signature ECDSA (secp384r1) server-digest SHA384)\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4g4FBD0cBGz1yJX\n\tfor ; Tue, 28 Apr 2026 06:13:19 +1000 (AEST)","from localhost ([::1] helo=bombadil.infradead.org)\n\tby bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux))\n\tid 1wHSKO-0000000069O-36rc;\n\tMon, 27 Apr 2026 20:13:12 +0000","from mail-centralusazlp170110009.outbound.protection.outlook.com\n ([2a01:111:f403:c111::9] helo=DM5PR21CU001.outbound.protection.outlook.com)\n\tby bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux))\n\tid 1wHSKL-0000000065y-23Yh;\n\tMon, 27 Apr 2026 20:13:10 +0000","from CY8PR12MB8300.namprd12.prod.outlook.com (2603:10b6:930:7d::16)\n by LV3PR12MB9166.namprd12.prod.outlook.com (2603:10b6:408:19c::13) with\n Microsoft SMTP Server (version=TLS1_2,\n cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9870.16; Mon, 27 Apr\n 2026 20:12:58 +0000","from CY8PR12MB8300.namprd12.prod.outlook.com\n ([fe80::ce75:8187:3ac3:c5de]) by CY8PR12MB8300.namprd12.prod.outlook.com\n ([fe80::ce75:8187:3ac3:c5de%3]) with mapi id 15.20.9870.013; Mon, 27 Apr 2026\n 20:12:57 +0000"],"DKIM-Signature":["v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed;\n\td=lists.infradead.org; s=bombadil.20210309; h=Sender:\n\tContent-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post:\n\tList-Archive:List-Unsubscribe:List-Id:MIME-Version:In-Reply-To:References:\n\tMessage-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:\n\tResent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:\n\tList-Owner; bh=xyWEB1py2H/uhjmogfbA5H27Qe7Ud9wOXDzdibZLO7A=; b=TqIz00UY/NJ5Ae\n\tDdP4jmFxsA7w0w9hHuBhdtzqoboxL2f3qiRMEGPMbjziwxlMYF6jCMJtGS2ZLvvFL+es1vo+zXEAr\n\tyMi/XhcuDQmzQKJ8BPIVvkkJBf6yNkMOkOy1rBPitfWHP/xM1pk5+fMaKVdjoKpgehqdLbJ6S5/jq\n\t/oqs7cfm1LSS1ZQbRkTndrSskEIX8sSlN83C6RfIdmh1lnNXLu8fprl3rhzoeSMqsI0mLg3mh1QyY\n\tHJxyU6w0DfiVfSPa3KsBjy2IznUQ9VXCKGwP/pnB/btr3nfY+CmKb5eEqz0fmTW7K3nchwONerSJt\n\ttrKFeVKn6jkUKaLk7v/w==;","v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com;\n s=selector2;\n h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck;\n bh=UKWQR0wFCYKwd7/WyoEVlZ7dAryoy8A/34DACb4Mweg=;\n b=hMJCquiWsKvsKPfnV6x+XewanJiprCXhKZ7l3EnI0mUQee6FHRXLrWa9OPoGIpSx+3ijfDDYf7rNW7PoM7DOSBnLPvsXAImaoD6B98Y7Upx4a9+jmx8qzSA1GldDlcxK8Pewp0jwDRy5JdWZd5Oq81ubXZq43utYi9tCvPcHtbJVcvLFWW/q7KgNksf7InTQ6smdi1OyjYpNmneI+Yx09fiTp08WMkqdpQGjsSSQVU9D7WqLP1BLpIUpVlAs267Rgj9nox2HtSQ5p5eE42gWq/zkifeODpWv1mo/3UxmRXJegCDfavI3oSRox5pAtdJxjEw5pvmed4+9e03qhtyLkg=="],"ARC-Seal":"i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none;\n b=BtrDbDcz6oik0VAePSzg5fGR+cooJsvCiqVpAkRyxjo7tVYcK6FTW120At87PvC2HmYqvF+zAYmUozmBiDpk3obvOrmRqnQu5b4NUoZkF4ujvP7nKdWKNRWeaLOXO5lx22JtfQpfCueE0stod3ZgwyZHZra4CSp8si7hhoGCGMHOU9NRGgQZvWgZxjvpiddt/5heAo5jaUAbusoeb6/N+ctwOqovcjGb3J/PDBJNthLIqytbew6CjsXMgRhp3uIkXxoc2xEaZ44Y9Ktv5ANbxXoHDUfrqejvOg1lxzqXzqzdTsDZXzt8mwjNLgfzVceatnj1bajoVfBGEPtevW6/ow==","ARC-Message-Signature":"i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com;\n s=arcselector10001;\n h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1;\n bh=UKWQR0wFCYKwd7/WyoEVlZ7dAryoy8A/34DACb4Mweg=;\n b=eIPokbumH3eDN+DqP5Ep1KaEMIWbZhTzgBKsNv19VF/W6X7jjPowB4UntDHWj76GVOLpVErRkTwf2pJ/YrDs45ZN6xDND6686ErEpWA2qQXwRCmtP46ysRgjHvM1NVSf8oin7VwsuXb30pKGJB4D4xu/biMyeV+73vzwzUrpYBXo7hdAidNUQHrxfYLBQEUhcH9MtIkFcqmeakpXHhSDEtl8blygh6QE25OuMpVAmZUWxT7paNvKfjp0MlyKuWB9S5BekJIjYVv4y8EE8wAO9HrTEKcIsKrwKajDUUZC4yUEssV8xNuhIqndzV8atExLn9UGWsZ3+sD76wTjiGaGgw==","ARC-Authentication-Results":"i=1; mx.microsoft.com 1; spf=pass\n smtp.mailfrom=nvidia.com; dmarc=pass action=none header.from=nvidia.com;\n dkim=pass header.d=nvidia.com; arc=none","Date":"Mon, 27 Apr 2026 16:12:55 -0400","From":"Yury Norov ","To":"\"Christophe Leroy (CS GROUP)\" ","Cc":"Andrew Morton ,\n\tLinus Torvalds ,\n\tDavid Laight ,\n\tThomas Gleixner , linux-alpha@vger.kernel.org,\n\tYury Norov , linux-kernel@vger.kernel.org,\n\tlinux-snps-arc@lists.infradead.org,\n\tlinux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org,\n\tlinuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org,\n\tlinux-riscv@lists.infradead.org, linux-s390@vger.kernel.org,\n\tsparclinux@vger.kernel.org, linux-um@lists.infradead.org,\n\tdmaengine@vger.kernel.org, linux-efi@vger.kernel.org,\n\tlinux-fsi@lists.ozlabs.org, amd-gfx@lists.freedesktop.org,\n\tdri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org,\n\tlinux-wpan@vger.kernel.org, netdev@vger.kernel.org,\n\tlinux-wireless@vger.kernel.org, linux-spi@vger.kernel.org,\n\tlinux-media@vger.kernel.org, linux-staging@lists.linux.dev,\n\tlinux-serial@vger.kernel.org, linux-usb@vger.kernel.org,\n\txen-devel@lists.xenproject.org, linux-fsdevel@vger.kernel.org,\n\tocfs2-devel@lists.linux.dev, bpf@vger.kernel.org,\n\tkasan-dev@googlegroups.com, linux-mm@kvack.org,\n\tlinux-x25@vger.kernel.org, rust-for-linux@vger.kernel.org,\n\tlinux-sound@vger.kernel.org, sound-open-firmware@alsa-project.org,\n\tlinux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org,\n\tloongarch@lists.linux.dev, linux-m68k@lists.linux-m68k.org,\n\tlinux-openrisc@vger.kernel.org, linux-parisc@vger.kernel.org,\n\tlinux-sh@vger.kernel.org, linux-arch@vger.kernel.org","Subject":"Re: [RFC PATCH v1 9/9] uaccess: Convert small fixed size\n copy_{to/from}_user() to scoped user access","Message-ID":"","References":"\n <8780eb2ef80575931a339e5225bc80eb13e9be6c.1777306795.git.chleroy@kernel.org>","Content-Disposition":"inline","In-Reply-To":"\n <8780eb2ef80575931a339e5225bc80eb13e9be6c.1777306795.git.chleroy@kernel.org>","X-ClientProxiedBy":"BN9PR03CA0683.namprd03.prod.outlook.com\n (2603:10b6:408:10e::28) To CY8PR12MB8300.namprd12.prod.outlook.com\n (2603:10b6:930:7d::16)","MIME-Version":"1.0","X-MS-PublicTrafficType":"Email","X-MS-TrafficTypeDiagnostic":"CY8PR12MB8300:EE_|LV3PR12MB9166:EE_","X-MS-Office365-Filtering-Correlation-Id":"bdfef69d-b376-4a04-fa4d-08dea4995fc0","X-MS-Exchange-SenderADCheck":"1","X-MS-Exchange-AntiSpam-Relay":"0","X-Microsoft-Antispam":"\n BCL:0;ARA:13230040|10070799003|1800799024|366016|7416014|376014|22082099003|18002099003|56012099003;","X-Microsoft-Antispam-Message-Info":"\n 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","X-Forefront-Antispam-Report":"\n CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:CY8PR12MB8300.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(10070799003)(1800799024)(366016)(7416014)(376014)(22082099003)(18002099003)(56012099003);DIR:OUT;SFP:1101;","X-MS-Exchange-AntiSpam-MessageData-ChunkCount":"1","X-MS-Exchange-AntiSpam-MessageData-0":"\n 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","X-OriginatorOrg":"Nvidia.com","X-MS-Exchange-CrossTenant-Network-Message-Id":"\n bdfef69d-b376-4a04-fa4d-08dea4995fc0","X-MS-Exchange-CrossTenant-AuthSource":"CY8PR12MB8300.namprd12.prod.outlook.com","X-MS-Exchange-CrossTenant-AuthAs":"Internal","X-MS-Exchange-CrossTenant-OriginalArrivalTime":"27 Apr 2026 20:12:57.8040\n (UTC)","X-MS-Exchange-CrossTenant-FromEntityHeader":"Hosted","X-MS-Exchange-CrossTenant-Id":"43083d15-7273-40c1-b7db-39efd9ccc17a","X-MS-Exchange-CrossTenant-MailboxType":"HOSTED","X-MS-Exchange-CrossTenant-UserPrincipalName":"\n L4Ck4zF95sPRkpw+1DBvmDDt+EvJGjHXhYAqkKsZVyTO5WLUeoARd7Y3XQH+qd9LnDnkEcQd9xWJtVVZZwcboA==","X-MS-Exchange-Transport-CrossTenantHeadersStamped":"LV3PR12MB9166","X-CRM114-Version":"20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 ","X-CRM114-CacheID":"sfid-20260427_131309_599578_34C18BDA ","X-CRM114-Status":"GOOD ( 13.34 )","X-Spam-Score":"-2.1 (--)","X-Spam-Report":"Spam detection software,\n running on the system \"bombadil.infradead.org\",\n has NOT identified this incoming email as spam. The original\n message has been attached to this so you can view it or label\n similar future email. If you have any questions, see\n the administrator of that system for details.\n Content preview: On Mon, Apr 27, 2026 at 07:13:50PM +0200, Christophe Leroy\n (CS GROUP) wrote: > copy_{to/from}_user() is a heavy function optimised\n for\n copy of large > blocs of memory between user and kernel space. > [...]\n Content analysis details: (-2.1 points, 5.0 required)\n pts rule name description\n ---- ----------------------\n --------------------------------------------------\n -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at https://www.dnswl.org/, no\n trust\n [2a01:111:f403:c111:0:0:0:9 listed in]\n [list.dnswl.org]\n -0.0 SPF_PASS SPF: sender matches SPF record\n -0.0 SPF_HELO_PASS SPF: HELO matches SPF record\n -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from\n envelope-from domain\n -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from\n author's\n domain\n -0.1 DKIM_VALID Message has at least one valid DKIM or DK\n signature\n 0.1 DKIM_SIGNED Message has a DKIM or DK signature,\n not necessarily valid\n -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1%\n [score: 0.0000]\n -0.0 DKIMWL_WL_HIGH DKIMwl.org - High trust sender","X-BeenThere":"linux-snps-arc@lists.infradead.org","X-Mailman-Version":"2.1.34","Precedence":"list","List-Id":"Linux on Synopsys ARC Processors ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Content-Type":"text/plain; charset=\"us-ascii\"","Content-Transfer-Encoding":"7bit","Sender":"\"linux-snps-arc\" ","Errors-To":"\n linux-snps-arc-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org"}}]