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 338FAC433F5 for ; Tue, 5 Apr 2022 08:41:23 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BEA9F6B0071; Tue, 5 Apr 2022 04:41:12 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B99476B0073; Tue, 5 Apr 2022 04:41:12 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A130B6B0074; Tue, 5 Apr 2022 04:41:12 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.28]) by kanga.kvack.org (Postfix) with ESMTP id 91FAE6B0071 for ; Tue, 5 Apr 2022 04:41:12 -0400 (EDT) Received: from smtpin08.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 60B1E20EFE for ; Tue, 5 Apr 2022 08:41:02 +0000 (UTC) X-FDA: 79322180364.08.3599569 Received: from NAM11-CO1-obe.outbound.protection.outlook.com (mail-co1nam11on2072.outbound.protection.outlook.com [40.107.220.72]) by imf13.hostedemail.com (Postfix) with ESMTP id 87CB02001F for ; Tue, 5 Apr 2022 08:41:01 +0000 (UTC) ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=LZK02BCPoXxYY6I3Ak+MfByJrZ9yN5qnU8mQhupAISxha2DswCPMORNwdyq9b3XKaMotYj1g/BWqLKqo6si5z33WYMP6RlG550a/jh0uivxzvb6bu7T2tD0v1yb01+o3ao5Q0q3EiJJ81Rh6WOwed41xgKqquS2+5UODqD6dBhs94rIOsJPkqDqRA5XZV1q8tQSQyNZiXj/4j3tMeGrpQg89CXQEKApk2P3Pns7UkaZ4ry3GwaAOi8+FM8KknjUzUeBbFgjzVQ6X/bXy3UTsQJ5TNmdRt3/Qp3f+v6xwlzlxplAQ/jGGl4WrCoPQQ8xUM+tmG/GYr7YK1iRvLVpvJQ== 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-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=fifLUnxgvwwG3se9OpBNXDZnfpHHII4EU2/bYBBtEbY=; b=XdqqJTrIW8DX2dTHtT5QJeOFmQA9IvFwHKp29VTRfWGoKuKtPhvL2VIGzP8z0nKl8l5ROcAZQIFlJibxkL7/91nLvWHC/SUDRoCG7lMakzgK1L1HEx7kVX0oIPWQAeKhQyHEmgN8Jjg9NaM0Tbgti9cz0pgiMK2r/UCQYjWNkUt+JPQSTDYv4O/mBQcbwAI70CyCubUsoCiP+arvOY0lvB1s/7OxOOstWKP0/LI9QMFFb3S2BKwiGDoVJKwAdxFczg+YeZVsQKTfKf6HqMkBNcEul7L1/oSlJxk3cdjFLJ7MOt0xKdYfb4SI1ik881CiSoceT6mPXqfMqWzC5dSA0g== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=amd.com; dmarc=pass action=none header.from=amd.com; dkim=pass header.d=amd.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amd.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=fifLUnxgvwwG3se9OpBNXDZnfpHHII4EU2/bYBBtEbY=; b=C+C3nwptsfNfAnqTpDiIBR985dgMHgjUXCkx8w7grKuCnF+9amxoqPj/Nb9g10btvvTIUG4wnunDPF6zv4HnpIP7PDdBObIygkfddl+n6GbFT7IvHeCqhcAILZbvxZmdm/BS1nMm6DkPfRY2mOuR2KozyyoyVfNe1WD5eD9c+EA= Received: from BY5PR12MB4289.namprd12.prod.outlook.com (2603:10b6:a03:204::14) by CY4PR12MB1128.namprd12.prod.outlook.com (2603:10b6:903:3e::13) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5123.31; Tue, 5 Apr 2022 08:40:57 +0000 Received: from BY5PR12MB4289.namprd12.prod.outlook.com ([fe80::4843:222b:2955:543f]) by BY5PR12MB4289.namprd12.prod.outlook.com ([fe80::4843:222b:2955:543f%7]) with mapi id 15.20.5123.031; Tue, 5 Apr 2022 08:40:57 +0000 Message-ID: <7da72067-6196-932d-92d0-1ff2018cee7f@amd.com> Date: Tue, 5 Apr 2022 14:10:42 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Subject: Re: [RFC PATCH v0 0/6] x86/AMD: Userspace address tagging Content-Language: en-US To: Peter Zijlstra Cc: Andy Lutomirski , Linux Kernel Mailing List , linux-mm@kvack.org, the arch/x86 maintainers , "Kirill A. Shutemov" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , Catalin Marinas , Will Deacon , shuah@kernel.org, Oleg Nesterov , ananth.narayan@amd.com References: <20220310111545.10852-1-bharata@amd.com> <6a5076ad-405e-4e5e-af55-fe2a6b01467d@www.fastmail.com> <20220405081427.GD30877@worktop.programming.kicks-ass.net> From: Bharata B Rao In-Reply-To: <20220405081427.GD30877@worktop.programming.kicks-ass.net> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: PN3PR01CA0049.INDPRD01.PROD.OUTLOOK.COM (2603:1096:c01:98::12) To BY5PR12MB4289.namprd12.prod.outlook.com (2603:10b6:a03:204::14) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: f403a659-79e5-4497-b92c-08da16e000e9 X-MS-TrafficTypeDiagnostic: CY4PR12MB1128:EE_ X-Microsoft-Antispam-PRVS: X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: WzBYCE7xooZPh4LmCphwCk7hUqdzuPDw6pYgh7R1OOJE2oi0BtRiORyo1fmBj2bphVnJfMppux1Zq6+jIC8DTj4kQ8rRcbfuGM4xemaHbQ9mB+YPYbwrZ/rI+GMbt/sI93DzD6D/rv3WEmo4Fh9CNDWyXeXiZrvzUixk01GFEqaXdcipOe1gC0WZxQz6pH1m/f2CRY9zaddOzFHe3mhl4daRyqlruuhmYXQf0F1+GZFycuFoyt4KtH5Zi7h9/gZy/yv/4wiK3jv3YTMTpGqkL7EtL/bRYpumPm+g99hn1AOl/Nu58SN8wx8w1dAwSdYa9mmArg05P594raC1R66AjarINCGS5T2ISflfnAn53ArdK+phYS1RGpYrlunfo0+deLGyKsjkv3MtSPtDjhefGXL8ZsiKGHcvi/J1WjN9+iPXYPZSq46cvJ8GzsV6C/tJ5D5vn0WX5bxyNLdCrSRltrDAPqw6upuWFrKqDXCucJqeERrG4bmEf2ARMK19UgGYcbZ4puDyZ88V7UDmXVbJnjp376D8xey4f9iAxhBpCaB+QrT/pPOeiMgCC4nhYtiMs/zCtKW06apMuIju20jtwMVawNYrn1Xg7ZFzH38DDpdDoGb3R5Wz+dCXoJTMk3MQb7TuWEi/nKCPdhpdAJx2iWaDOTQczm2WQgC7f2A3dXStOrwXnIYskrvtuGpatj0BEnxqvhW3MG7Z4ArPdlmZ3imK+3CGbWOKVfdxZamvU4cDGOrRak4gD0WdSO56tmPC X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:BY5PR12MB4289.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230001)(4636009)(366004)(7416002)(316002)(6916009)(2616005)(186003)(53546011)(31696002)(26005)(6506007)(31686004)(6512007)(38100700002)(5660300002)(54906003)(86362001)(36756003)(83380400001)(8936002)(6486002)(8676002)(4326008)(2906002)(6666004)(66476007)(66946007)(66556008)(508600001)(43740500002)(45980500001);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?M3RYN0xNZWk4QTN3eG1XK2tpNXI3aDdYRTIxcUYwRlNYNFR4ZHVvOUtUV2lD?= =?utf-8?B?Rzk5SUtFcFlXMzB6NGxTV0pTaG9XVWNYTDNYdGVmRDg1ZkdUQ1ExYTlEM3FV?= =?utf-8?B?STN2WHRSZ2tBUCtiTTl1QnpGeUdXbnpzblJjempIdWdWRzh0d2RLU3AyOEdW?= =?utf-8?B?bzY0N3JTMkJpZkcrYzM1ZmJRQUY1MzNpK24yWDEyZVVLaWExOVBZN09XTXdl?= =?utf-8?B?b0srdVpIYXl3R2tmb0VRb0k3ODFybDJUK1FYdjVaa3lBdjU2R2Y1S0o1L013?= =?utf-8?B?N0FDMmNEWnEwMlR0ZmpSR2puTjhSbkN2b21Cd0V5NHRocjRzb21KeHpDNVc3?= =?utf-8?B?cGxYdkp0bjFYMFQwTkwxTHlacFdXQ3M0MG1OTG5rZHE3OHc1VGpCRnk4K3hj?= =?utf-8?B?ZzJHZEsva1V0MGo0VTNkeGdaZHRubHJ5RWNYaGd4V1VmSTRFVmluYnpMUjRY?= =?utf-8?B?NmRPWkh1S0o2WHFjQ05WdEdldjdTSzhqQVBQTFlnaHA4dW9RdFpIeGV6aDhH?= =?utf-8?B?azJob3ExOEE4d0VPSjVZVHpyT0kwS1BzWjhheldCU2JLS3BnbTcvZHduQ2t1?= =?utf-8?B?MDdQR3hyUGNEeVMzblZGMjN3RXpiVHRHRGQ4ak15d0dlWmg1dzJDQWhDSjBG?= =?utf-8?B?WVY3MWZGZHFkQzZ4MEU2bEQ0MUhTSnROSlZZZDl0UkFvY25wbC9NblBESk1J?= =?utf-8?B?MWJSWEMrT1BrdTNiTlA3NFRLeUw4NXBOczBraEhQa29obysxVmo3Rm9LMFlC?= =?utf-8?B?cCt5aGJUTmxsUzhqYUo5ZUVrd20ydTRwYkt4STZZN2pRb0FKeEppSU1ZcW9W?= =?utf-8?B?a0lNZFc1dUVsazczTVV2dnVTWG5JdHJ5TDlaSnE1WnpOQkZ3RzVuTmZpWlFC?= =?utf-8?B?T0Y5QnZ4enZ3REQ0cEtrOGNVS25HK29rcVp5UTlpdmZ2d1ZNWUx4RTB6WXhX?= =?utf-8?B?dnlaTUdFdlZrN0hLUEQxaHlOUW1lQVVlSnZ6VGxLSnlEWHNZd2xVbGZ1aURy?= =?utf-8?B?aWRwc2gxdk1zYUFOd3dGaFh5ZE40ZDhYZmtqbTBiNDY0bEZ5TWM0ZmJPcHhh?= =?utf-8?B?TUtmTDJSK2I1QWxTb2FWejVEODlLamd4UFZVVFZZY1JNQ293MUZDek16cVQ2?= =?utf-8?B?dityeGtiNHZIeGFhNlRrR0pDNGtkOW9BN0hNN2RLU2NhMnYzVlJic0FweXRx?= =?utf-8?B?WTFVY1BYNS9ZMzRhV1VWNmVydnc4NEJiNzV5OTI4Tyt3MkEvUDBDbFVpM0ZV?= =?utf-8?B?VERqc09pZ3dWenYvR2hCZ2Mva1RQQU9SMHRMcnV0QXNUL0ZlSDhqTnpnR2NI?= =?utf-8?B?K3FZZU1TS2NVcHpXNVdoU01BaEZhVWUyUnFPZzZybGR3MFFqQUVxczMxYzBq?= =?utf-8?B?NTFkL054WGtqbjJQWHptQUdSK2lJQy9GRENnUy9OeGVDOU5MZTh2NGxiQkJV?= =?utf-8?B?V3NURk05UzV3UzJCeld4V3JnVXlLdStjZlVESDFuL3ZXNVEwMWxqNUlUTHMy?= =?utf-8?B?ZFo4RmIxcFE5KzM4M3M4M1A2VkpqNHhnMTlaU0ZBZDhTV0wraExvc0F0U3hh?= =?utf-8?B?b1MySzlhcm82cDc2cVV6UTRvaHVUaDNMS2RZSzkrYzdwR0laNkVKamdLMlNq?= =?utf-8?B?YWswaTBBcUppN1lzRUE1dm1JRnlwZlUzTGRBcEtPSFNkdVV5cXNzTEgzSktB?= =?utf-8?B?b1RHMUVYcStONUxGU0czNXZPUGtKZHBPYi9weGhYaTY1SFF3L2k0blFDUExs?= =?utf-8?B?V3FkK2dVQ2V4ZXVESno2N1p1V3Z5blNwSCt4dUtBQ1hhWnlJL0FBRGZqdUt3?= =?utf-8?B?YXVEWHR2a1gvZlhRYjBER2dxTWtEbnhyQ096L1FGdnE0TzZKWXpuQkRqZVRD?= =?utf-8?B?VjlpZ0ZCdWFhYlhsemtla0ZZakxnYzdYQjFTM2x5RTlTU0M1dFFvUzQ3bXBC?= =?utf-8?B?Uk90bm82K2Z2MUhXWXdYNE5vZ0t6aVlVcW42aU4wSDdSR2c0aFFrUmJRMHF1?= =?utf-8?B?MVVVSkdNd3IyeExIUlF0M2dRUXVOdlNUbktuUlFOd1M1Q2FwY1RMZ3JweEpr?= =?utf-8?B?UGhGYTFwNDNnQ3kwdXlucU85Yjg0cVVOTEpsaGpLNEJhL1U0dVhlZnBQdW9o?= =?utf-8?B?dFNNcGxxbURZWmI1WEZudU8zVnc0OXRCR2dLT2IrYWJVZjFQazRqL25XM1h0?= =?utf-8?B?Vy8xMHlHSVpGWkVJdDNSVWVFcFNyaFhpc2Znd21XMy9teWw0U1RJN25nbEla?= =?utf-8?B?YjBuMFFEbTBaY1J4NUhRQXhDVmMzVHplRDFSazFIbGJJOWdaSXAraVVCYzgz?= =?utf-8?B?Qks0Tm54VS9wMDZhRERBSUpnVHk0TDc3SDcwNmtnTk5hMnY1Wm5aZz09?= X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: f403a659-79e5-4497-b92c-08da16e000e9 X-MS-Exchange-CrossTenant-AuthSource: BY5PR12MB4289.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 Apr 2022 08:40:57.3754 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: LKu1xaeCWRQN6ib/E/ffAKPlQ9ZxCvXwrO+potYZNLDMbyx7TfdEX/TdlKYe3Ffr5Bl8W5ArGLApRnv9oycyZw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY4PR12MB1128 X-Rspam-User: Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=amd.com header.s=selector1 header.b=C+C3nwpt; spf=pass (imf13.hostedemail.com: domain of bharata@amd.com designates 40.107.220.72 as permitted sender) smtp.mailfrom=bharata@amd.com; dmarc=pass (policy=quarantine) header.from=amd.com X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 87CB02001F X-Stat-Signature: znp94bu4e1ohrnrtyo8pxkd9x7pgjbzx X-HE-Tag: 1649148061-539695 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: On 4/5/2022 1:44 PM, Peter Zijlstra wrote: > On Wed, Mar 23, 2022 at 01:18:41PM +0530, Bharata B Rao wrote: >> On 3/22/2022 3:59 AM, Andy Lutomirski wrote: > >>> I hate to be a pain, but I'm really not convinced that this feature >>> is suitable for Linux. There are a few reasons: >>> >>> Right now, the concept that the high bit of an address determines >>> whether it's a user or a kernel address is fairly fundamental to the >>> x86_64 (and x86_32!) code. It may not be strictly necessary to >>> preserve this, but violating it would require substantial thought. >>> With UAI enabled, kernel and user addresses are, functionally, >>> interleaved. This makes things like access_ok checks, and more >>> generally anything that operates on a range of addresses, behave >>> potentially quite differently. A lot of auditing of existing code >>> would be needed to make it safe. >> >> Ok got that. However can you point to me a few instances in the current >> kernel code where such assumption of high bit being user/kernel address >> differentiator exists so that I get some idea of what it takes to >> audit all such cases? > > The fact that you have to ask and can't readily find them should be a > big honking clue on its own, no? > > Anyway, see here: > > arch/x86/events/perf_event.h:static inline bool kernel_ip(unsigned long ip) > arch/x86/events/perf_event.h:{ > arch/x86/events/perf_event.h:#ifdef CONFIG_X86_32 > arch/x86/events/perf_event.h: return ip > PAGE_OFFSET; > arch/x86/events/perf_event.h:#else > arch/x86/events/perf_event.h: return (long)ip < 0; > arch/x86/events/perf_event.h:#endif > arch/x86/events/perf_event.h:} That's a pretty good and clear example. Thanks Peter. I do now see that auditing all such instances would be an uphill task. Regards, Bharata.