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 X-Spam-Level: X-Spam-Status: No, score=-5.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MSGID_FROM_MTA_HEADER,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 047C8C47098 for ; Thu, 3 Jun 2021 10:30:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D8104613AD for ; Thu, 3 Jun 2021 10:29:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229854AbhFCKbm (ORCPT ); Thu, 3 Jun 2021 06:31:42 -0400 Received: from mx0a-0064b401.pphosted.com ([205.220.166.238]:31222 "EHLO mx0a-0064b401.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229746AbhFCKbl (ORCPT ); Thu, 3 Jun 2021 06:31:41 -0400 Received: from pps.filterd (m0250809.ppops.net [127.0.0.1]) by mx0a-0064b401.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 153AM85b023774; Thu, 3 Jun 2021 03:29:32 -0700 Received: from nam11-dm6-obe.outbound.protection.outlook.com (mail-dm6nam11lp2173.outbound.protection.outlook.com [104.47.57.173]) by mx0a-0064b401.pphosted.com with ESMTP id 38xd5c0nhg-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 03 Jun 2021 03:29:32 -0700 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=gdwz756m1X1vmLsDgyHQGHVJ4l1FKzviJ2hu4xgdzWybBLqh2M9tdkYRPAn21bmuV/S/heaRFBpufqHPFlXek1TEfsVjik2q5PID2qD3j2MuCBVcq9GrYx3xa9iW3MofyNRaDdQP36qiCYZ4M0AWQM+ZwzQApHw3N9ddiu3CoGgHSn0n2OTQak8NF6nOjiiZRIT5YyA8BDCVs5Tk1BcqKlkp7cfgQn6DcPnnj6DYYGGBBPVtKR3DjXV7/1nr1xJZvfYcgqW+YmTRjcMSNCnvSbftwoKIppRP/2UFe87+NZ74+JqaGftZOg5rtezVeaAi+n9Wdc41pgFwX9TK8SBlPQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=9L1t8jttGVAKsd3M81MHsSXrtXeZCcyUEfkz7eYUgEE=; b=mk4+N8zwpOswEI3DEFTF8i45tbIeszX0hXlxGYmZKcajk6O68bkUekxn1pMlZRpay6SDdbbIbjPgaWXq/qKuww7cuiNmd9eci6t7J1vLm+/9wUn/OvtEpcIqlPd0eaPPOda3QoEHXo7+Qi8eM3gc9quKEPy+BxlCYH/50/8ahNTgcjqqXL34DSo/NNyDuHnk5IGYmZ0qsYiArTLM9gKuEl8sKnvs8KwwBQtYTtLnrA3iX34g5nihitjhxk1qb6E4gGKcTWjPdYfeZTrRUqWT73vEEHO/70dv+ez9F4ozbklGLiXUMuBjZil5GKEGIQy5siBcNZXdrd/v9OYe65noFw== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=windriver.com; dmarc=pass action=none header.from=windriver.com; dkim=pass header.d=windriver.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=windriversystems.onmicrosoft.com; s=selector2-windriversystems-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=9L1t8jttGVAKsd3M81MHsSXrtXeZCcyUEfkz7eYUgEE=; b=Vp56ppawJb/+GfZ8V8pm7+Dk2nol9dPYtTze8Gq/BbjT+lEgH2NawHm0yTLyo+BPEnMrH1/2N99gZTjknJokS+/oOkjrETUZIL1LRm4NioRooFekzMNXgE7oIXF36fB9ThWdT1b04mDYubdrMLDBKYGXFMKTaXEfhgBekRJR3Cc= Authentication-Results: vger.kernel.org; dkim=none (message not signed) header.d=none;vger.kernel.org; dmarc=none action=none header.from=windriver.com; Received: from BY5PR11MB4241.namprd11.prod.outlook.com (2603:10b6:a03:1ca::13) by SJ0PR11MB4814.namprd11.prod.outlook.com (2603:10b6:a03:2d8::23) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4173.22; Thu, 3 Jun 2021 10:29:28 +0000 Received: from BY5PR11MB4241.namprd11.prod.outlook.com ([fe80::34b3:17c2:b1ad:286c]) by BY5PR11MB4241.namprd11.prod.outlook.com ([fe80::34b3:17c2:b1ad:286c%5]) with mapi id 15.20.4173.030; Thu, 3 Jun 2021 10:29:28 +0000 Subject: Re: [PATCH 1/1] bpf: avoid unnecessary IPI in bpf_flush_icache To: Will Deacon Cc: Daniel Borkmann , ast@kernel.org, zlim.lnx@gmail.com, catalin.marinas@arm.com, andrii@kernel.org, kafai@fb.com, songliubraving@fb.com, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20210601150625.37419-1-yanfei.xu@windriver.com> <20210601150625.37419-2-yanfei.xu@windriver.com> <56cc1e25-25c3-a3da-64e3-8a1c539d685b@iogearbox.net> <20210601174114.GA29130@willie-the-truck> <7637dcdf-12b4-2861-3c76-f8a8e240a05e@windriver.com> <20210602172603.GB31957@willie-the-truck> From: "Xu, Yanfei" Message-ID: <895953fd-d462-2696-0ab3-72a069ba5a75@windriver.com> Date: Thu, 3 Jun 2021 18:29:16 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 In-Reply-To: <20210602172603.GB31957@willie-the-truck> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [60.247.85.82] X-ClientProxiedBy: HK2PR04CA0080.apcprd04.prod.outlook.com (2603:1096:202:15::24) To BY5PR11MB4241.namprd11.prod.outlook.com (2603:10b6:a03:1ca::13) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [128.224.162.160] (60.247.85.82) by HK2PR04CA0080.apcprd04.prod.outlook.com (2603:1096:202:15::24) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4195.15 via Frontend Transport; Thu, 3 Jun 2021 10:29:24 +0000 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 2d36c869-b071-46f3-8fc2-08d9267a7782 X-MS-TrafficTypeDiagnostic: SJ0PR11MB4814: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:3044; X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: vnB6I2Vj6xevAIpkptkDBGmOf8boI7IzbrjQJ5Be4oyj3n2D3pFggVy8c6PNhiUs/Lq6fHg92llxtyAYAoLyvajgyZIgvjAGBQ+gmhB1/ADW/8jViSjcNvt6PEDUKYsoZpeJVXxv2nFnxanpZjzng9QdvOqAOwbYJp0hPx59spfhUG9L/kogwCx09zzbw46lJlahMHh02VnmJiPS0VooAckjn44YJha8J9SnAEMv3XJziZ9jkR4Y5xou2O9DtREB2xFuMuqx2TWAtRU1bbjL71gxNmJf0Ku4A+D9qEl0ksViNeUNrhXIMWyZfLuulfNF+CTs/K/FA9o+fp+5YEpBQQZHi73CDRzmJUy36FybIy2HDMnut0H+P8mZYN+0q9Swrwhu0DveAvsnV/yEkLyJQlAB12/CgXspxMyqg3vIoKAbg5M07olvzY0c30+bxMG8mFnMMlYh1Chkz2NU+ac7Iw/gVudh7b2qm/FPdB2l0aoA2oRmQrMdAWgZ1XA9oi6PyywbljZrb9iM3DCHbPUUD4Lp0c2PGjzNk0Soj0uJJlbA/qMWlVLUcNW3MqLDrbYVSGvxaW8h+ALHoqnIGNAOFTCbxg9C6EgY6sJNfmKWLy7uFE44BcqCUTglvDIX1bRoJhyyB/6deu5Jo9N4SIdnW7+F/tBqPzhWYoiOLQ4eHpO+axsBwr9CuSkgjGv38b7/jVUn/+H2xRc1Ysrbjz/8zZIMSHNoCPRdX72YMKGmMpk= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:BY5PR11MB4241.namprd11.prod.outlook.com;PTR:;CAT:NONE;SFS:(4636009)(136003)(396003)(366004)(346002)(376002)(39830400003)(2906002)(7416002)(52116002)(26005)(16576012)(6916009)(6706004)(316002)(16526019)(31686004)(186003)(36756003)(8676002)(4326008)(5660300002)(2616005)(956004)(6486002)(31696002)(6666004)(53546011)(478600001)(8936002)(38350700002)(38100700002)(86362001)(66556008)(66946007)(66476007)(78286007)(43740500002)(45980500001);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?ZmtPaWFHUkVJb21ISC9iTmEreDFPeHZ0akZTRGs1ZWdkVkdsbUR5aTNObUh0?= =?utf-8?B?cHBvNGpGR2ZlNHZRVjdkYTk4NUVMRkdyaStvL1lEVkdNQktVZ01Xb0w5UHpO?= =?utf-8?B?Z1lFQjRxZG1uSGNCcU1HRk5IYW5Rems1UktDcjRlVUYrblRsZytER3JhUzBC?= =?utf-8?B?TE9SZTBUNFpUdVNZVEtUdUVIK2FtZ0NpUm1xRk1pckNVaENDQXNUMjJQQytU?= =?utf-8?B?UnJTcE1MWnB2cnMzOUJGYmsyeS84N0NHYkY1WlUwMjl3UklMVjBEZXd2SUUr?= =?utf-8?B?TngrbDNSSnFaaGhDaktWSlZJbEREZ2dFMWlxQTBaeittNmwvcDBReEdCV0J3?= =?utf-8?B?dmdabXcxUDB4RnQ4Rjd1Nm1ySllrcXFQZFNndlppSFdRS3Y3UCtxOURtMk05?= =?utf-8?B?MXJISGx2ZE9naUpoS0Rua1U1WnhVUlo5UUExTXh3TkxWMXRXendWN3F1MGxV?= =?utf-8?B?WDFWbEtWdGZ5NGZOSHFiYk5HbVZUdXdoTi9OWElVQ25NVW0yRDdsV0pRNGQz?= =?utf-8?B?T0FlZlIwbWtoT0NseWlxYUxoYkwwZ0hIZy8rcnZXVlNVQ3VvR0VZZWR2czNv?= =?utf-8?B?L215MDBLYXFWTzhsNzg4TUJwSFQ1bGpKK0QzVTVNYTlSRkZxRHdnQzNDbmpY?= =?utf-8?B?WEZINzVhMGVPT3BKOG16QWxPZTlqMGJmOEQ2K01qVE14MlJpelZEWDk3WUhO?= =?utf-8?B?TmJWeVZIcklQbnFUVFpseDYxWGdiS3FlSXlDZ0h1OEVHZ3VmNVBFQm9mV0k3?= =?utf-8?B?bjBLYm10czY1aldpSG1ZS3Y0eHY1RkcycU9tb0tPQzFtK1grRFNzaTgwNTVU?= =?utf-8?B?UzBtOXF3TnYvYlRHaVdjV2dodW5ZQ3hmYXQ0OWl1eTF4NytJNXBpdkhaTFY0?= =?utf-8?B?MzdoWmZJQ3QxZzV2ekN6S2tkOFF0QUZUblhneGFoUndyZFhBZysxK2VucUZV?= =?utf-8?B?SjE4YW1pK1NCbGU3WFNBL0FiV2JqQWdpY1RPVlVnY1lsVmwxNE9kSGZud0RJ?= =?utf-8?B?YmZZRWNabzU1NEtjZ3NkZUFIdmdwOWlrdVdhNU5DNkswL1ZQY3FsdFQyWDNl?= =?utf-8?B?NGsrQk5iVG05ZlVEL0x1Tkx2UTNLd1dHSWE1ZHFFNlJuNDh3aUtrWDBjWURy?= =?utf-8?B?QUZMZXNUVTlkYnlYb0lyZXh0b0ZlS0ZnWHhrYWZvWFYvOTNyQWJQbnZmRnNn?= =?utf-8?B?cVhUQVNHZkp2cFRwd0lYWmVaNzVFSVdZR3hSYTlnS0tUd0tOTnZVVHl5TVBh?= =?utf-8?B?NlhvL3dDKzdvaGJhS2I4ZkJrbTJWVU9uZnlGaE4yamR6aktUZ3hxdlFGeVpD?= =?utf-8?B?QTJaTFFNeWZUVmUxdU83RkxVS3dwaytvdlJLYUxIYzZlRlIzNXcwMGxHUkVq?= =?utf-8?B?cnNGOVZQSWxNcGJ2T2hiV3Fyd3M0bUZuOTZuZXA3RTFPaGZ5S1JBQ0xQSEFW?= =?utf-8?B?Vk1TQjQwcTVvL0dvb3NwSnFLeTJpMjNSMHBSTURucWFjVU5IaCtRaGcvSEpF?= =?utf-8?B?STJZd2FWUzltby9iTWpJTWN0RitUYXB6MWZTdWVHSXhwM0ljOGlHa3Rsemgw?= =?utf-8?B?M1BPbXlKd1h4dFVEZFJRVVRxNERHR0dXRzFYR3lBWjl1NmNzdmh3eStRQ3Zv?= =?utf-8?B?TjVvNlpDN2dQUTBzTkw2QTIzN0YxSmtNcjYrN2V1ODRYSzZoNVJMNlpHdE8y?= =?utf-8?B?SXJYelZ0SjF4TVFpN1UycDZIWFM4YVNSSnUzdkdDM1lJc1MyRHF3dC9IWk1L?= =?utf-8?Q?Svi5ngUO6I2ghVZifkX9DssVFbV9HHq0FMgYBLn?= X-OriginatorOrg: windriver.com X-MS-Exchange-CrossTenant-Network-Message-Id: 2d36c869-b071-46f3-8fc2-08d9267a7782 X-MS-Exchange-CrossTenant-AuthSource: BY5PR11MB4241.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Jun 2021 10:29:28.7084 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 8ddb2873-a1ad-4a18-ae4e-4644631433be X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: k/deRI4XiinQEmFayn0y8/g/auDA6uV0lrQ/lKyfOlO/io0jce5ep9/Fbr+MvZZ1zSMzZgxU7RBC7mXhYGbdNg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR11MB4814 X-Proofpoint-ORIG-GUID: sPb9lkFH4kCSSiOPEgr7DDgoJY8OX4Hj X-Proofpoint-GUID: sPb9lkFH4kCSSiOPEgr7DDgoJY8OX4Hj X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.761 definitions=2021-06-03_06:2021-06-02,2021-06-03 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 mlxscore=0 suspectscore=0 malwarescore=0 spamscore=0 priorityscore=1501 impostorscore=0 adultscore=0 lowpriorityscore=0 mlxlogscore=999 phishscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2106030070 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/3/21 1:26 AM, Will Deacon wrote: > [Please note: This e-mail is from an EXTERNAL e-mail address] > > On Wed, Jun 02, 2021 at 07:26:03PM +0800, Xu, Yanfei wrote: >> >> >> On 6/2/21 1:41 AM, Will Deacon wrote: >>> [Please note: This e-mail is from an EXTERNAL e-mail address] >>> >>> On Tue, Jun 01, 2021 at 07:20:04PM +0200, Daniel Borkmann wrote: >>>> On 6/1/21 5:06 PM, Yanfei Xu wrote: >>>>> It's no need to trigger IPI for keeping pipeline fresh in bpf case. >>>> >>>> This needs a more concrete explanation/analysis on "why it is safe" to do so >>>> rather than just saying that it is not needed. >>> >>> Agreed. You need to show how the executing thread ends up going through a >>> context synchronizing operation before jumping to the generated code if >>> the IPI here is removed. >> >> This patch came out with I looked through ftrace codes. Ftrace modify >> the text code and don't send IPI in aarch64_insn_patch_text_nosync(). I >> mistakenly thought the bpf is same with ftrace. >> >> But now I'm still not sure why the ftrace don't need the IPI to go >> through context synchronizing, maybe the worst situation is omit a >> tracing event? > > I think ftrace handles this itself via ftrace_sync_ipi, no? Ah, Yes! I missed this... Anyway, thanks for your reminding and very sorry for my noise. Regards, Yanfei > > Will > 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 X-Spam-Level: X-Spam-Status: No, score=-6.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MSGID_FROM_MTA_HEADER,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A6871C47082 for ; Thu, 3 Jun 2021 10:32:09 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6B60961207 for ; Thu, 3 Jun 2021 10:32:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6B60961207 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=windriver.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:In-Reply-To:Date:Message-ID:From: References:Cc:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=qieiFbA/NaDmCF4yvAK3825PrnoOli4pmtTuqa+kpsQ=; b=RdkudNN/ymChXbxXnhema0wZ/s uSPUwCJeMa5f5n57/h3YARWNnCTgswPW/CTFmLps/UTWHl86meQCWqzUEZyLJ90Efs3I/8f78Ypqe XjySLE2GDyoq9rF9qSw6o6nA21nCVae5ZwJ1DRcPgzN6BJB3ZsEnncPpT3SbJ6AWKfIS5R9yrYpGl s7XcjmulVH10GPnaomabQYVqW4bPcrHZ5INDeArtNteatX1IShZ7AKWCzuHQQWdSAfELR1XbL9Rmv jSKKRcI1XEfXbzDXmuT//cadt06l6TbcjqerkpXwj9jhucFRpNFo0It9vglwugyHcuXjHtA80y4z+ OhdQy6Pg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1lokbv-0087BK-Uc; Thu, 03 Jun 2021 10:30:00 +0000 Received: from mx0a-0064b401.pphosted.com ([205.220.166.238]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1lokbr-0087An-MC for linux-arm-kernel@lists.infradead.org; Thu, 03 Jun 2021 10:29:57 +0000 Received: from pps.filterd (m0250809.ppops.net [127.0.0.1]) by mx0a-0064b401.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 153AM85b023774; Thu, 3 Jun 2021 03:29:32 -0700 Received: from nam11-dm6-obe.outbound.protection.outlook.com (mail-dm6nam11lp2173.outbound.protection.outlook.com [104.47.57.173]) by mx0a-0064b401.pphosted.com with ESMTP id 38xd5c0nhg-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 03 Jun 2021 03:29:32 -0700 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=gdwz756m1X1vmLsDgyHQGHVJ4l1FKzviJ2hu4xgdzWybBLqh2M9tdkYRPAn21bmuV/S/heaRFBpufqHPFlXek1TEfsVjik2q5PID2qD3j2MuCBVcq9GrYx3xa9iW3MofyNRaDdQP36qiCYZ4M0AWQM+ZwzQApHw3N9ddiu3CoGgHSn0n2OTQak8NF6nOjiiZRIT5YyA8BDCVs5Tk1BcqKlkp7cfgQn6DcPnnj6DYYGGBBPVtKR3DjXV7/1nr1xJZvfYcgqW+YmTRjcMSNCnvSbftwoKIppRP/2UFe87+NZ74+JqaGftZOg5rtezVeaAi+n9Wdc41pgFwX9TK8SBlPQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=9L1t8jttGVAKsd3M81MHsSXrtXeZCcyUEfkz7eYUgEE=; b=mk4+N8zwpOswEI3DEFTF8i45tbIeszX0hXlxGYmZKcajk6O68bkUekxn1pMlZRpay6SDdbbIbjPgaWXq/qKuww7cuiNmd9eci6t7J1vLm+/9wUn/OvtEpcIqlPd0eaPPOda3QoEHXo7+Qi8eM3gc9quKEPy+BxlCYH/50/8ahNTgcjqqXL34DSo/NNyDuHnk5IGYmZ0qsYiArTLM9gKuEl8sKnvs8KwwBQtYTtLnrA3iX34g5nihitjhxk1qb6E4gGKcTWjPdYfeZTrRUqWT73vEEHO/70dv+ez9F4ozbklGLiXUMuBjZil5GKEGIQy5siBcNZXdrd/v9OYe65noFw== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=windriver.com; dmarc=pass action=none header.from=windriver.com; dkim=pass header.d=windriver.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=windriversystems.onmicrosoft.com; s=selector2-windriversystems-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=9L1t8jttGVAKsd3M81MHsSXrtXeZCcyUEfkz7eYUgEE=; b=Vp56ppawJb/+GfZ8V8pm7+Dk2nol9dPYtTze8Gq/BbjT+lEgH2NawHm0yTLyo+BPEnMrH1/2N99gZTjknJokS+/oOkjrETUZIL1LRm4NioRooFekzMNXgE7oIXF36fB9ThWdT1b04mDYubdrMLDBKYGXFMKTaXEfhgBekRJR3Cc= Authentication-Results: vger.kernel.org; dkim=none (message not signed) header.d=none;vger.kernel.org; dmarc=none action=none header.from=windriver.com; Received: from BY5PR11MB4241.namprd11.prod.outlook.com (2603:10b6:a03:1ca::13) by SJ0PR11MB4814.namprd11.prod.outlook.com (2603:10b6:a03:2d8::23) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4173.22; Thu, 3 Jun 2021 10:29:28 +0000 Received: from BY5PR11MB4241.namprd11.prod.outlook.com ([fe80::34b3:17c2:b1ad:286c]) by BY5PR11MB4241.namprd11.prod.outlook.com ([fe80::34b3:17c2:b1ad:286c%5]) with mapi id 15.20.4173.030; Thu, 3 Jun 2021 10:29:28 +0000 Subject: Re: [PATCH 1/1] bpf: avoid unnecessary IPI in bpf_flush_icache To: Will Deacon Cc: Daniel Borkmann , ast@kernel.org, zlim.lnx@gmail.com, catalin.marinas@arm.com, andrii@kernel.org, kafai@fb.com, songliubraving@fb.com, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20210601150625.37419-1-yanfei.xu@windriver.com> <20210601150625.37419-2-yanfei.xu@windriver.com> <56cc1e25-25c3-a3da-64e3-8a1c539d685b@iogearbox.net> <20210601174114.GA29130@willie-the-truck> <7637dcdf-12b4-2861-3c76-f8a8e240a05e@windriver.com> <20210602172603.GB31957@willie-the-truck> From: "Xu, Yanfei" Message-ID: <895953fd-d462-2696-0ab3-72a069ba5a75@windriver.com> Date: Thu, 3 Jun 2021 18:29:16 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 In-Reply-To: <20210602172603.GB31957@willie-the-truck> Content-Language: en-US X-Originating-IP: [60.247.85.82] X-ClientProxiedBy: HK2PR04CA0080.apcprd04.prod.outlook.com (2603:1096:202:15::24) To BY5PR11MB4241.namprd11.prod.outlook.com (2603:10b6:a03:1ca::13) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [128.224.162.160] (60.247.85.82) by HK2PR04CA0080.apcprd04.prod.outlook.com (2603:1096:202:15::24) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4195.15 via Frontend Transport; Thu, 3 Jun 2021 10:29:24 +0000 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 2d36c869-b071-46f3-8fc2-08d9267a7782 X-MS-TrafficTypeDiagnostic: SJ0PR11MB4814: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:3044; X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255; CTRY:; LANG:en; SCL:1; SRV:; IPV:NLI; SFV:NSPM; H:BY5PR11MB4241.namprd11.prod.outlook.com; PTR:; CAT:NONE; SFS:(4636009)(136003)(396003)(366004)(346002)(376002)(39830400003)(2906002)(7416002)(52116002)(26005)(16576012)(6916009)(6706004)(316002)(16526019)(31686004)(186003)(36756003)(8676002)(4326008)(5660300002)(2616005)(956004)(6486002)(31696002)(6666004)(53546011)(478600001)(8936002)(38350700002)(38100700002)(86362001)(66556008)(66946007)(66476007)(78286007)(43740500002)(45980500001); DIR:OUT; SFP:1101; X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?ZmtPaWFHUkVJb21ISC9iTmEreDFPeHZ0akZTRGs1ZWdkVkdsbUR5aTNObUh0?= =?utf-8?B?cHBvNGpGR2ZlNHZRVjdkYTk4NUVMRkdyaStvL1lEVkdNQktVZ01Xb0w5UHpO?= =?utf-8?B?Z1lFQjRxZG1uSGNCcU1HRk5IYW5Rems1UktDcjRlVUYrblRsZytER3JhUzBC?= =?utf-8?B?TE9SZTBUNFpUdVNZVEtUdUVIK2FtZ0NpUm1xRk1pckNVaENDQXNUMjJQQytU?= =?utf-8?B?UnJTcE1MWnB2cnMzOUJGYmsyeS84N0NHYkY1WlUwMjl3UklMVjBEZXd2SUUr?= =?utf-8?B?TngrbDNSSnFaaGhDaktWSlZJbEREZ2dFMWlxQTBaeittNmwvcDBReEdCV0J3?= =?utf-8?B?dmdabXcxUDB4RnQ4Rjd1Nm1ySllrcXFQZFNndlppSFdRS3Y3UCtxOURtMk05?= =?utf-8?B?MXJISGx2ZE9naUpoS0Rua1U1WnhVUlo5UUExTXh3TkxWMXRXendWN3F1MGxV?= =?utf-8?B?WDFWbEtWdGZ5NGZOSHFiYk5HbVZUdXdoTi9OWElVQ25NVW0yRDdsV0pRNGQz?= =?utf-8?B?T0FlZlIwbWtoT0NseWlxYUxoYkwwZ0hIZy8rcnZXVlNVQ3VvR0VZZWR2czNv?= =?utf-8?B?L215MDBLYXFWTzhsNzg4TUJwSFQ1bGpKK0QzVTVNYTlSRkZxRHdnQzNDbmpY?= =?utf-8?B?WEZINzVhMGVPT3BKOG16QWxPZTlqMGJmOEQ2K01qVE14MlJpelZEWDk3WUhO?= =?utf-8?B?TmJWeVZIcklQbnFUVFpseDYxWGdiS3FlSXlDZ0h1OEVHZ3VmNVBFQm9mV0k3?= =?utf-8?B?bjBLYm10czY1aldpSG1ZS3Y0eHY1RkcycU9tb0tPQzFtK1grRFNzaTgwNTVU?= =?utf-8?B?UzBtOXF3TnYvYlRHaVdjV2dodW5ZQ3hmYXQ0OWl1eTF4NytJNXBpdkhaTFY0?= =?utf-8?B?MzdoWmZJQ3QxZzV2ekN6S2tkOFF0QUZUblhneGFoUndyZFhBZysxK2VucUZV?= =?utf-8?B?SjE4YW1pK1NCbGU3WFNBL0FiV2JqQWdpY1RPVlVnY1lsVmwxNE9kSGZud0RJ?= =?utf-8?B?YmZZRWNabzU1NEtjZ3NkZUFIdmdwOWlrdVdhNU5DNkswL1ZQY3FsdFQyWDNl?= =?utf-8?B?NGsrQk5iVG05ZlVEL0x1Tkx2UTNLd1dHSWE1ZHFFNlJuNDh3aUtrWDBjWURy?= =?utf-8?B?QUZMZXNUVTlkYnlYb0lyZXh0b0ZlS0ZnWHhrYWZvWFYvOTNyQWJQbnZmRnNn?= =?utf-8?B?cVhUQVNHZkp2cFRwd0lYWmVaNzVFSVdZR3hSYTlnS0tUd0tOTnZVVHl5TVBh?= =?utf-8?B?NlhvL3dDKzdvaGJhS2I4ZkJrbTJWVU9uZnlGaE4yamR6aktUZ3hxdlFGeVpD?= =?utf-8?B?QTJaTFFNeWZUVmUxdU83RkxVS3dwaytvdlJLYUxIYzZlRlIzNXcwMGxHUkVq?= =?utf-8?B?cnNGOVZQSWxNcGJ2T2hiV3Fyd3M0bUZuOTZuZXA3RTFPaGZ5S1JBQ0xQSEFW?= =?utf-8?B?Vk1TQjQwcTVvL0dvb3NwSnFLeTJpMjNSMHBSTURucWFjVU5IaCtRaGcvSEpF?= =?utf-8?B?STJZd2FWUzltby9iTWpJTWN0RitUYXB6MWZTdWVHSXhwM0ljOGlHa3Rsemgw?= =?utf-8?B?M1BPbXlKd1h4dFVEZFJRVVRxNERHR0dXRzFYR3lBWjl1NmNzdmh3eStRQ3Zv?= =?utf-8?B?TjVvNlpDN2dQUTBzTkw2QTIzN0YxSmtNcjYrN2V1ODRYSzZoNVJMNlpHdE8y?= =?utf-8?B?SXJYelZ0SjF4TVFpN1UycDZIWFM4YVNSSnUzdkdDM1lJc1MyRHF3dC9IWk1L?= =?utf-8?Q?Svi5ngUO6I2ghVZifkX9DssVFbV9HHq0FMgYBLn?= X-OriginatorOrg: windriver.com X-MS-Exchange-CrossTenant-Network-Message-Id: 2d36c869-b071-46f3-8fc2-08d9267a7782 X-MS-Exchange-CrossTenant-AuthSource: BY5PR11MB4241.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Jun 2021 10:29:28.7084 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 8ddb2873-a1ad-4a18-ae4e-4644631433be X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: k/deRI4XiinQEmFayn0y8/g/auDA6uV0lrQ/lKyfOlO/io0jce5ep9/Fbr+MvZZ1zSMzZgxU7RBC7mXhYGbdNg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR11MB4814 X-Proofpoint-ORIG-GUID: sPb9lkFH4kCSSiOPEgr7DDgoJY8OX4Hj X-Proofpoint-GUID: sPb9lkFH4kCSSiOPEgr7DDgoJY8OX4Hj X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391, 18.0.761 definitions=2021-06-03_06:2021-06-02, 2021-06-03 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 mlxscore=0 suspectscore=0 malwarescore=0 spamscore=0 priorityscore=1501 impostorscore=0 adultscore=0 lowpriorityscore=0 mlxlogscore=999 phishscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2106030070 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210603_032955_832660_E45AC6FA X-CRM114-Status: GOOD ( 19.35 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 6/3/21 1:26 AM, Will Deacon wrote: > [Please note: This e-mail is from an EXTERNAL e-mail address] > > On Wed, Jun 02, 2021 at 07:26:03PM +0800, Xu, Yanfei wrote: >> >> >> On 6/2/21 1:41 AM, Will Deacon wrote: >>> [Please note: This e-mail is from an EXTERNAL e-mail address] >>> >>> On Tue, Jun 01, 2021 at 07:20:04PM +0200, Daniel Borkmann wrote: >>>> On 6/1/21 5:06 PM, Yanfei Xu wrote: >>>>> It's no need to trigger IPI for keeping pipeline fresh in bpf case. >>>> >>>> This needs a more concrete explanation/analysis on "why it is safe" to do so >>>> rather than just saying that it is not needed. >>> >>> Agreed. You need to show how the executing thread ends up going through a >>> context synchronizing operation before jumping to the generated code if >>> the IPI here is removed. >> >> This patch came out with I looked through ftrace codes. Ftrace modify >> the text code and don't send IPI in aarch64_insn_patch_text_nosync(). I >> mistakenly thought the bpf is same with ftrace. >> >> But now I'm still not sure why the ftrace don't need the IPI to go >> through context synchronizing, maybe the worst situation is omit a >> tracing event? > > I think ftrace handles this itself via ftrace_sync_ipi, no? Ah, Yes! I missed this... Anyway, thanks for your reminding and very sorry for my noise. Regards, Yanfei > > Will > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel