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Miller" , "linux-crypto@vger.kernel.org" , "linux-kernel@vger.kernel.org" References: <20200806163551.14395-1-andrei.botila@oss.nxp.com> <20200806163551.14395-2-andrei.botila@oss.nxp.com> <20200821034651.GA25442@gondor.apana.org.au> <20200908221019.GA23497@gondor.apana.org.au> <67159207-1082-48be-d085-971a84b525e0@nxp.com> <38f9904b-5bf7-ea99-ed8a-27cb49f405bd@nxp.com> From: =?UTF-8?Q?Horia_Geant=c4=83?= Message-ID: <4393bf96-30fd-0d1c-73fe-f5ef7c967f76@nxp.com> Date: Tue, 15 Sep 2020 13:02:41 +0300 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-ClientProxiedBy: AM0PR02CA0103.eurprd02.prod.outlook.com (2603:10a6:208:154::44) To VI1PR04MB4046.eurprd04.prod.outlook.com (2603:10a6:803:4d::29) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [192.168.0.129] (78.97.206.147) by AM0PR02CA0103.eurprd02.prod.outlook.com (2603:10a6:208:154::44) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3370.16 via Frontend Transport; Tue, 15 Sep 2020 10:02:50 +0000 X-Originating-IP: [78.97.206.147] X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-HT: Tenant X-MS-Office365-Filtering-Correlation-Id: 48aed4de-d68e-4a85-77a7-08d8595e81e5 X-MS-TrafficTypeDiagnostic: VI1PR04MB6142: X-MS-Exchange-Transport-Forked: True X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:8882; X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: n7vlaNG7yosW0vqXheXXPCW4nNZuh2CJK1ecYSmIUqzjjymdVriDz5+ChYenoGsa/HBVH3veEv/DLtR7jo/fad+wu/mqBIDy/6Y6pfOi+I2SmeT5RSPMxT1GS0Jb3rc7JEDDpEe7C1R2EEe4SAQj0IalMa1J0C8QxBb/XooTcgzouJzoa5GCdwXqeN///8SrRwl53YNzhO7c3MtXdT5LxrQTWgTDK/V9rZx5D491Yl71ZuHBB19bWubR0dqxEjZYc4B8Xh4y4Hn4lr1TZPAK5RVve65yh2ay5cYukSGhf69LPP6CRDBOMuVwrjzuLVFxNOCocK6cFHg8nj7w06bg8tLeyCClMxdKyYt1b5fShYhtHnn8NH+18zTDVQnimVJk X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:VI1PR04MB4046.eurprd04.prod.outlook.com;PTR:;CAT:NONE;SFS:(4636009)(376002)(346002)(366004)(39860400002)(136003)(396003)(8936002)(316002)(31696002)(186003)(5660300002)(6666004)(6486002)(66556008)(66476007)(66946007)(86362001)(16526019)(31686004)(2906002)(36756003)(8676002)(16576012)(956004)(6916009)(2616005)(4326008)(54906003)(83380400001)(53546011)(52116002)(478600001)(26005)(43740500002);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData: 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 X-OriginatorOrg: nxp.com X-MS-Exchange-CrossTenant-Network-Message-Id: 48aed4de-d68e-4a85-77a7-08d8595e81e5 X-MS-Exchange-CrossTenant-AuthSource: VI1PR04MB4046.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Sep 2020 10:02:51.7070 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 686ea1d3-bc2b-4c6f-a92c-d99c5c301635 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: S2B+Og7JuU6hPHhv5Z1xCT4FVkQGDyNWARfu85A5c2XX4FjDCq7gL8/nSv7IkqV2iUVO5T5zvz8yVaZJ34t1Gw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI1PR04MB6142 Sender: linux-crypto-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org On 9/14/2020 9:20 PM, Ard Biesheuvel wrote: > On Mon, 14 Sep 2020 at 20:12, Horia Geantă wrote: >> >> On 9/14/2020 7:28 PM, Ard Biesheuvel wrote: >>> On Mon, 14 Sep 2020 at 19:24, Horia Geantă wrote: >>>> >>>> On 9/9/2020 1:10 AM, Herbert Xu wrote: >>>>> On Tue, Sep 08, 2020 at 01:35:04PM +0300, Horia Geantă wrote: >>>>>> >>>>>>> Just go with the get_unaligned unconditionally. >>>>>> >>>>>> Won't this lead to sub-optimal code for ARMv7 >>>>>> in case the IV is aligned? >>>>> >>>>> If this should be optimised in ARMv7 then that should be done >>>>> in get_unaligned itself and not open-coded. >>>>> >>>> I am not sure what's wrong with avoiding using the unaligned accessors >>>> in case data is aligned. >>>> >>>> Documentation/core-api/unaligned-memory-access.rst clearly states: >>>> These macros work for memory accesses of any length (not just 32 bits as >>>> in the examples above). Be aware that when compared to standard access of >>>> aligned memory, using these macros to access unaligned memory can be costly in >>>> terms of performance. >>>> >>>> So IMO it makes sense to use get_unaligned() only when needed. >>>> There are several cases of users doing this, e.g. siphash. >>>> >>> >>> For ARMv7 code, using the unaligned accessors unconditionally is fine, >>> and it will not affect performance. >>> >>> In general, when CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is defined, >>> you can use the unaligned accessors. If it is not, it helps to have >>> different code paths. >>> >> arch/arm/include/asm/unaligned.h doesn't make use of >> linux/unaligned/access_ok.h, even if CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS >> is set. >> >> I understand the comment in the file, however using get_unaligned() >> unconditionally takes away the opportunity to generate optimized code >> (using ldrd/ldm) when data is aligned. >> > > But the minimal optimization that is possible here (one ldrd/ldm > instruction vs two ldr instructions) is defeated by the fact that you > are using a conditional branch to select between the two. And this is > not even a hot path to begin with, > This is actually on the hot path (encrypt/decrypt callbacks), but you're probably right that the conditional branching is going to offset the optimized code. To avoid branching, code could be rewritten as: #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS size = *(u64 *)(req->iv + (ivsize / 2)); #else size = get_unaligned((u64 *)(req->iv + (ivsize / 2))); #endif however in this case ARMv7 would suffer since CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y and ldrd/ldm for accesses not word-aligned are inefficient - lead to traps. Would it be ok to use: #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && !defined(CONFIG_ARM) to workaround the ARMv7 inconsistency? Thanks, Horia