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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 1A987CCFA13 for ; Tue, 11 Nov 2025 01:22:29 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2C7928E0003; Mon, 10 Nov 2025 20:22:29 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 29F938E0002; Mon, 10 Nov 2025 20:22:29 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 18E728E0003; Mon, 10 Nov 2025 20:22:29 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 0029D8E0002 for ; Mon, 10 Nov 2025 20:22:28 -0500 (EST) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 9A8C314033A for ; Tue, 11 Nov 2025 01:22:28 +0000 (UTC) X-FDA: 84096575976.30.E4A38F2 Received: from CH1PR05CU001.outbound.protection.outlook.com (mail-northcentralusazon11010069.outbound.protection.outlook.com [52.101.193.69]) by imf10.hostedemail.com (Postfix) with ESMTP id A9ED9C0009 for ; Tue, 11 Nov 2025 01:22:25 +0000 (UTC) Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=Nvidia.com header.s=selector2 header.b=YxluLoBE; arc=pass ("microsoft.com:s=arcselector10001:i=1"); spf=pass (imf10.hostedemail.com: domain of balbirs@nvidia.com designates 52.101.193.69 as permitted sender) smtp.mailfrom=balbirs@nvidia.com; dmarc=pass (policy=reject) header.from=nvidia.com ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1762824145; 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=duLeZCxOHMv5b9z5/m1C4wLTsgXl1hVjVPgUnU5O0uo=; b=L9L+op7idAj1B+j13kPOqvOpBPCPGLarx3y1j/KF8YKEvqy3t1DxcMS9FeqwKf2NnxFfSB EOwKYyhapKfMaPIC6y50WBLhoKdscvvxWwLLzYMf8Li4WbV7Hi6S1mVWzoSQ2kWM0S4Mfz X0Uidaw6L8W015aNzRiO0h7gKfHQbKo= ARC-Authentication-Results: i=2; imf10.hostedemail.com; dkim=pass header.d=Nvidia.com header.s=selector2 header.b=YxluLoBE; arc=pass ("microsoft.com:s=arcselector10001:i=1"); spf=pass (imf10.hostedemail.com: domain of balbirs@nvidia.com designates 52.101.193.69 as permitted sender) smtp.mailfrom=balbirs@nvidia.com; dmarc=pass (policy=reject) header.from=nvidia.com ARC-Seal: i=2; s=arc-20220608; d=hostedemail.com; t=1762824145; a=rsa-sha256; cv=pass; b=H/qOtvQ52lbrgE6GeYadPCmVeZNJYotDo/sr2FZU8aXbONXJmzTqrNcKUgSOy0hJa9q2Y1 /ruknjWseQbQb8v0pODZJWj35RP2uYCK0+Y0GKkWrwguqkTU5wNynIscTDle/eOlfpW5Rg 6QD0TFFZ/pEo6mqzrNfgRxY6XFZmWF0= ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=OdCHw9jxWcZSViFzM7sehki2WLtMqoOjki+SRtZdrhLn+Cyl7kTM9VTbvVxqmrAGCpLVIDG28A97DLdg9SohSl69V4NOHX7WhjXAhyExdzlPhKmTURreibr1VQyQf95Fi5g2O4QVcwOVZFbCpWjqdMrwrUa3vz9t+FxoE3BA8Ma7/t9X5ARltsSwMY03b1z/7XOzBC1siu+uku57y14CgbSA6ppNcaGqefhTATwmtt7fND7/UvEUawZH95RMcGH/TItXQlc4b+Gt6yPnBlPpcEO7ZKf9vXj6HN4rXrLVa7k2ildEWNCSrXcIyzXo/6gV/QDaAZeOKx96vrLJRFqy0Q== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; 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=duLeZCxOHMv5b9z5/m1C4wLTsgXl1hVjVPgUnU5O0uo=; b=WRy2jg0Wj6pogEqKOiwlMV7di1IINl+f62zAY5Jbss5VPX6/i0IIvoBTXdjdaCEETHL+HtcbSbcO6coJJdlXDyega/PTBXZl+i/nk9CjFQePz/u1UV/qOdhUvPCaohoCEWyroCv1ml1RM5mGfi5fFxuin6IZz9DwPtt3b5z50uJpBzTRt1MdYySzVCZnETYCnF00n1AP823NqY5qHZaRTGkkZswYWTwm5JJmTg9PEIVuhhhJuKfiGWz8kDvzXkh8DsMvv4PE1Tf0t8T8TXGx1cU/4KaD+5nZ2vZesc9qRcwbbIFf7uzqU+lMz+6uUTHBBYbDXsUXXf9WbpZvhRdkFg== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nvidia.com; dmarc=pass action=none header.from=nvidia.com; dkim=pass header.d=nvidia.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=duLeZCxOHMv5b9z5/m1C4wLTsgXl1hVjVPgUnU5O0uo=; b=YxluLoBEyT890AL5v8d2A+tFTR3nYkndgYbrE2nxlKijQFFYzXBF4tWT3Fioya3XRscHYsl/FQvqIhl6u+1rHkH/hrR2PJkkvPo6ETrPx+reSVCcmsjm31NBNXSYI8bIiLJKls5UZLCo/o4nBs3za6Hjl1Ue25YeCZVPS+mUrfoxhk4Y31oE9CWWQiACVfEk2kkQ+QHi79xijBDmnmOCDvtn9kkTaawK0ThrupeleK4YyDD/Jj6knzlX4zXsKUYkr2A24zJ7GmGW7f0utn094dIxSueorYLV19/26yrUHI0kJkUtnhg6904o6ghJmxLP3bQxbVJf8WK10dO/nLaINw== Received: from PH8PR12MB7277.namprd12.prod.outlook.com (2603:10b6:510:223::13) by LV8PR12MB9357.namprd12.prod.outlook.com (2603:10b6:408:1ff::14) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9298.16; Tue, 11 Nov 2025 01:22:22 +0000 Received: from PH8PR12MB7277.namprd12.prod.outlook.com ([fe80::3a4:70ea:ff05:1251]) by PH8PR12MB7277.namprd12.prod.outlook.com ([fe80::3a4:70ea:ff05:1251%7]) with mapi id 15.20.9298.015; Tue, 11 Nov 2025 01:22:22 +0000 Message-ID: <439c62a4-ddac-425c-b505-ed9a33aae289@nvidia.com> Date: Tue, 11 Nov 2025 12:22:15 +1100 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] x86/kaslr: P2PDMA is one of a class of ZONE_DEVICE-KASLR collisions To: Mike Rapoport , Dan Williams Cc: dave.hansen@linux.intel.com, peterz@infradead.org, linux-mm@kvack.org, linux-cxl@vger.kernel.org, linux-pci@vger.kernel.org, Ingo Molnar , Kees Cook , Bjorn Helgaas , Andy Lutomirski , Logan Gunthorpe , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , "Yasunori Gotou (Fujitsu)" References: <20251108023215.2984031-1-dan.j.williams@intel.com> Content-Language: en-US From: Balbir Singh In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BYAPR01CA0038.prod.exchangelabs.com (2603:10b6:a03:94::15) To PH8PR12MB7277.namprd12.prod.outlook.com (2603:10b6:510:223::13) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH8PR12MB7277:EE_|LV8PR12MB9357:EE_ X-MS-Office365-Filtering-Correlation-Id: 89eb87f8-8909-4c5c-6548-08de20c0c375 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|10070799003|366016|1800799024|7053199007; X-Microsoft-Antispam-Message-Info: =?utf-8?B?Y1ZGRXl0VXIyZ0sxL2V6dlRmdkFHRHJmTVJzVGRDeVd6ZXVEUE81b3dPSXlX?= =?utf-8?B?L2hPZkVNSTNZRjNqa3QxWllqV2lKcWxtcHVBa29ldU02L3RGMDNVUE5YUWwv?= =?utf-8?B?Njk4MlF0MkgwT3lJL1dwQ1pCNjMyUHUwS2duQTNNd1hkRitSVFN3dHltVytV?= =?utf-8?B?TWhvaDZ4NEhKMVZMeXZieGRRbGt3V3ZLQTBjTThSMVEwV1NEUlJMcHV1RFk5?= =?utf-8?B?R2VmM0pZV2k4bHVaaE1KcHp5WXYvMFVCOXBid0l3d2loaWpFYmxZWFh1UDZ5?= =?utf-8?B?eWlwNFplYkxkWHhuY3FZY3d3NjhVSGNIQlMzSldmT2dUcC9oWmN3K285ZUlL?= =?utf-8?B?bUpDNDA4Tk1yc0J5bDNlYTlZVE9QSXE3QU4rOTIzOFAvYTVNWUY4dnB3Q0Jl?= =?utf-8?B?dWpZWW1YdGJaemYwaXM1VVNmMVpZL3JCWkE3ZDd5ZlUzczQxdDJqcjlzS085?= =?utf-8?B?UW9wL0RsOWowU0lyUE13OGtEckpaWU42VzRTS09YaGpJV3BqdGVsTUlxMGdC?= =?utf-8?B?andlb2M2UmlLSEVkdC9DWFl2WlIzNEhSeDFVY2pMQTlyMFB0NXk1UmxSNW9J?= =?utf-8?B?c3pDL0s3dW9zMGJWZUx3dFFVY3ZwdFpPR2Jub0Nzbk5hYUhNMlhQeGVTd3Fl?= =?utf-8?B?V3BhWEl2S1VROHM1dE80bDJVRXRCbDlNdnlveThQYk9GNFBJb2NYUUQyMlhG?= =?utf-8?B?V2ZhN3B2dThLak5BY1V3OVpJNDZlbGVNeldqUWw0QkI3NjJrTDQyRVJPT2gx?= =?utf-8?B?YlJSam55aTRYZmxNZ2ZTeGhiaWxocWlRRzZjdTZIaW5zUThwbzhTWkFjaWNG?= =?utf-8?B?WS95eHk4WWVwUzVHZFFsamkyZ2JXTFdSYUJnRG9wNmdJYVpob2NzRU5wNmNq?= =?utf-8?B?RlNRMVJZdWQrSTVCa1JCdERjdGR6KzFKeGV0bDZOZXJuSFFJUDZ0b0h3OFAz?= =?utf-8?B?VU5Fb3NMUFJOOXl5cUNkOWRqMzB6U2FrT1VtQVV3b2J0MDZJKzBTZVJKM29I?= =?utf-8?B?TFMzenBlbWFSMnRyNnNkWStVelo0Yyt3eENldHFVSjFGWVQ5SE9NUGdpV0hm?= =?utf-8?B?RHR5bWhSbEtzRjNaK21KVU01UXUwdW5hR3ZHdlVuV3gwRnc1QWpQV25hcGV6?= =?utf-8?B?dWZtYTBTK0R5ZlVYc3R3dWhGWUVhbWE0ajFTdXQ2eXB5dGdxVUswKzV5WmNX?= =?utf-8?B?TnlCL3Bpa0p6TW5GY2lrOVJRajlqcy9tVXZNU0VrNWd1bmJZK0JvaE1VUURs?= =?utf-8?B?MzlaTHlKTVJoRkNXc3ZWWk9HVHNDRHAvQXNtRGd4SlNJdGNCeS9mMUE4OGJa?= =?utf-8?B?eWtQUkFDOEhoM01ITVl1VzNreDR1NGw1R3VCRmZGb0Q5Tkx3c3JaZVZOSnVl?= =?utf-8?B?ZDdKMXgyRWdNdTlPWXRQL2FLSG9iWFFlWklmNkJaK1dsZE02WEhzT0thd2k2?= =?utf-8?B?U3pVemxKNDk4VzdsK0xpRExtVlh6M3J6MkVQMFExNU9VNG9ldTJZUUxPYzA4?= =?utf-8?B?YlZZOEJTV2J2dUNLdGNQMit3RFFFYlpyc0dsNG5la3N3eEg2RE5aazcwR2l5?= =?utf-8?B?Z1VGK1dTV0p0SXVMeEdRNlk3aDlzUlh3aVhubjNKNjZERVVlQXpFUGJPdnNy?= =?utf-8?B?VktiRkluaXBVWDlkUTJWdGQ3NVRXTnR0NlBud2daLzVQQTBJV0FQYW41VHVo?= =?utf-8?B?Q1hJajZUcVJCT1hCMVN5MERwUjFuVnVqNXdTcjRYSUkraStmbVNYTjJlZ1ll?= =?utf-8?B?S3I2MWJJSDZQYzRiOHRFZ2tlKzNiYnBrc21SMHpjYWZURWVWZFJMYkxjdnlX?= =?utf-8?B?Mi9CWTRISnlyK2FiRXlsYlBzR1QycGxucTJHTTV0cVNCK3k0RlZzSFFXL0ZW?= =?utf-8?B?aEpNdWVCWFJtRTUzckVmOGx6alNIbHVxNjZOMk9IblVVTkliS0xCSUk1ZDFL?= =?utf-8?Q?5GoohHFUDBq7AL6cwmNQhUgh+O8ofsOo?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:PH8PR12MB7277.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(7416014)(376014)(10070799003)(366016)(1800799024)(7053199007);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?Q3liNklQTS9OVmhsTDhIUVVuS245VktFcjE3QTZqcWhIOTl6TmM5WUZyNjJu?= =?utf-8?B?RFUxZU5LdGRKZzh6SGEveWlZU09xNFFaZ3dGK3ppMnVTMlBmR1R2VyswTnBq?= =?utf-8?B?eklRWUR6YUZZK2VOaTVEdDcxd1FSUnNhdEpoNXdDY28xc0V3SUlwdms2aWdY?= =?utf-8?B?ajUvaGliOXdzWEh2Uk1zd1EyZStiRnQ5UFh2SEw4S3hBajI5MWViUmlNK21i?= =?utf-8?B?eWJkRW94SDRNT1Z0SWl5UG95UXhyMDdCSkFLZGJXR2t2UXJWVkxhTG9mTjR4?= =?utf-8?B?dWZjald5MUFuUlFmbXdrQmpzUENweXdEUi9nNVViT0xBTVJ3TytzUEhUNi9y?= =?utf-8?B?TVA1S3E5cGdRT2Vtb214WnhaRlQ5akp1SXZkSUc3YnZIQWVCLys0cFdnQlVa?= =?utf-8?B?NitpckVDeE8wcGdwTGdmbDlBakRzczg4V1daVDJBVXBLanExUVZJSElZamF6?= =?utf-8?B?R0RRVjRKSndOYzN1LzVBT1pQeCswNDBkRjAzeUNEZDZzVWRiQVhvek5uTWtm?= =?utf-8?B?bUFIUjRwMXB0NFpoTnBZTWp4NUNua3Fnak1JS05KUGRqU3ZHeHBOZWp5Q0I1?= =?utf-8?B?d0VxVHlRN0FRVHExQ1pEZXZTd2QzRmpOT3kvbEgwVlNKMmMrb0lVQXlBWnpV?= =?utf-8?B?MERjcHFvWFZoVHAra29Na1N4VE1HTzJRd2xpVVBueXJlSXpWQWF0M3NrcmIr?= =?utf-8?B?cnNWaTZoRG1ZMEM1QXZZVkR2SWFBbVFPdmNwZFpUZm81Z0VLbmFPOCtUd1Fh?= =?utf-8?B?ODdCV0NkcWZ6Ryt0M0wzQUxvNjB1dmd5aVVaRVloaS9MVGJSN0E2UzdVQjhK?= =?utf-8?B?YS9qaUN1WlRIenR6KzlFZHlhVzhEaTdQU0FGWFVYMzZhYmhXdlcxZXNSSjBE?= =?utf-8?B?M2dWVW93Tm02MjB3UlZZZHBTNmJ5d3ZzZE94SWRKcklINGRnZ3U2dWxvV3JN?= =?utf-8?B?TDFIS2R2aXVob2ZqeVQ1dDgxM3ZRRWdQZG5haGhFQmEzNHlmc3RsbVVWT1Nm?= =?utf-8?B?K2JUSFZwMVlHU2RiN1FBZ3JOWlNXb0tjck5VNlhuanlLSld4cU9KTVlEQWQx?= =?utf-8?B?VHpzYm0vVStWV0hVdjgzNzFDV3JjN2V4U0NxMnFCRllkbDNsRU13KzR1UktU?= =?utf-8?B?ei9FZ0RtRmh6cGNpN0NyTkxYM3NUNnFTOEhPTE84cklmZ2xxQmMrSUZ6UmU2?= =?utf-8?B?WHFYSmd0WVh1VkM4cm9tZXBmMzZwRExLNTlCeWQySGc0VzJFTm5yUVUxenQ0?= =?utf-8?B?cSswNXBjY3F5WjBIbmhlL2k1ajF0eDk4RmlDUkpkeVZ0andIejcvTnhQSG1k?= =?utf-8?B?aEZBakVvOUVCbHkzaTV0R2diekVOYndxOVByUHpQd3Y2bmZDVFJEZnRuYXlv?= =?utf-8?B?L0FRRzNJQXJreFNndUFzeVd0c1Y1MDUyT1NOVlBmSVU2SytjQUE0NGpSbmoy?= =?utf-8?B?ZG1MT2FZbG03VUFnT1NvaWN6UlBvTWQ1VGdGeFFwM2VNRWFwNDVlcFhXRkxz?= =?utf-8?B?dG5qdXFtMlNTTjBGdnA4M0IzQlpPbkV4L0FtNXVPQyt2TDZycHkwb2JtWEJq?= =?utf-8?B?a2J2UnhxUlBrbzNScThGSXphZmJ0dFRYTzlwTitCOXMyOWVZTTlJQkdKaXJS?= =?utf-8?B?OEFNd1pEbnhoTUR6eG1IWjd1VVoxWVowdmZkZEJ2VXZrSWJCdnhXNlFuSVlv?= =?utf-8?B?L2lIODdBdTlUYlRLc09sU0dKYUNvVzNyMzFZNTdURDI4L0dTNml1dllUc0Yv?= =?utf-8?B?TEpVMXVoaWFlOXlCVkJZc053dkxYdDV3M1BNL0FJU0pEWWMzcS9SL0pZWGxD?= =?utf-8?B?akNQU1RRQXlNTUJMWnFVbkVTcHlISEJETlNCU3Nvd1M5WmZ0US9JMTdtYkJQ?= =?utf-8?B?NUJVVVhVNVk2OU1iZHpQdi92ZGpNSWEvSk9XejhWbzNwZXdmd09JWkpwemZU?= =?utf-8?B?Ym1nMFlJbkdDNlh4T3ZrVjVNYlNPZnB6T3ZmbHdhby8xTXJZYTNjU0RCV0tD?= =?utf-8?B?QjAzeEhCU0dFdnNTWEdBWFdsbXhWVTFsZHA1WkI0Y29SUkpaK1MyNUoyRGk2?= =?utf-8?B?OUFYQmhFWGlzbUQvMlUrc3BzUGRqaGpEYzg0dkxUYVVYZmxRc01Ddm5BRVdu?= =?utf-8?B?bUx3OVVVRzRyRXZZSW1xMEVnSDMxL2hUb3NBTWFWWU1uMldrTmFMM1lUZ01Q?= =?utf-8?Q?e2CNrtJz4F3u3FMukpVYm2XkfxFarQ/3afFu6HLzRSAQ?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 89eb87f8-8909-4c5c-6548-08de20c0c375 X-MS-Exchange-CrossTenant-AuthSource: PH8PR12MB7277.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 11 Nov 2025 01:22:22.0119 (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: zXHZlLt09GmfV7MLMR9LaYfBiQJbxcOR8MGBXtvpA5J0MbgtoEVSrFMeTmgRYHhP1guO0KwEGEbhyRW6MBHndA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV8PR12MB9357 X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: A9ED9C0009 X-Stat-Signature: b59498hw9nd4dfytxb4zjn9gjy7b3srk X-Rspam-User: X-HE-Tag: 1762824145-703794 X-HE-Meta: U2FsdGVkX1/JdM2QDTnF1acZja+rMjIuMr49cEvGoTHc6tu8a0p+HyXl0L6ULdvtkSPa/BWLbsExgt4Sq2sVAKdgpu+Y5ORm60GXmuIEP2QAxaCEyoa4KMlePcJSMRfpgksZIoep4pkALAaAiF9kCMbxr+XbPUN2Fjn59WdMCngisZQntyBgrDNWtcHyJMbCsfHGxZH1cbeuOgU0PemVcv62jPVynEJpHwREwTcVHmgEm7UlcYci0RPJM2whmd2kLtE3uNpFRrwxdSKcqFnjuK7pAnd5dEkJW00F5d7gZfII+v3jaNoZix+npaWmjp/yU+2RKdbt4062c2XUQzOpUiTKnTiWqaQo16Dr0BMl1g84K6y+0X4hGinOnL/8d1yfGb359cda9o53KNmn2z3OxQYXxg02bIl9ttVWcY1A8lBXAMwIee9XiXdmyjFPJu3EWxlqFg4kotIAr45V5y99GOESpzm6Y9qmWt2dMVUMkILkUbhCDCi0KvQQoep2Zkv3heN7Lbv5F8zewCunV2i6gJP8UQ0SS0KXkb1K395scTyQkrcHDxI4xEYQf9URaBbHhSnL9WslmXvmL290ExTxFRnCV3xll4y3HjpO0+z38jDA+8XKTEDwQ/wNv+9ODaH0tgCuWnxqaNg1ZqieZmdG+wuhPG7ioSWrkJWTWMA0smICuVPO1yln2hBgcs7gJ4bbV5kDTaW5jSuBAqWE2JV8zKfaKcyvL232jYOzaNOEWGedTp/+IzDRCgY3WqCz9K8qMUDJWd5PeEH8n09eHwE9vSXB9k5OhC1BAC6hFKt9sWtYNscs8BuhjyhY89NMEhHuGDH5emmzPWe0m8hyB7t8aWznY8lBt7ji4ge9nEB4NVCsKrld0tHVCumAmbqq5gio/tz1GoG70GKYW4CbRvFd1ALzZQ1J4Kp7ejpOPJKVCYfNylzZP8cevnhwg6flzQrVOdZdVjPCPUfVIIM7/r7 7XSmrZfH 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 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 11/9/25 17:51, Mike Rapoport wrote: > On Fri, Nov 07, 2025 at 06:32:15PM -0800, Dan Williams wrote: >> Commit 7ffb791423c7 ("x86/kaslr: Reduce KASLR entropy on most x86 systems") >> is too narrow. ZONE_DEVICE, in general, lets any physical address be added >> to the direct-map. I.e. not only ACPI hotplug ranges, CXL Memory Windows, >> or EFI Specific Purpose Memory, but also any PCI MMIO range for the >> CONFIG_DEVICE_PRIVATE and CONFIG_PCI_P2PDMA cases. >> >> A potential path to recover entropy would be to walk ACPI and determine the >> limits for hotplug and PCI MMIO before kernel_randomize_memory(). On >> smaller systems that could yield some KASLR address bits. This needs >> additional investigation to determine if some limited ACPI table scanning >> can happen this early without an open coded solution like >> arch/x86/boot/compressed/acpi.c needs to deploy. >> >> Cc: Balbir Singh >> Cc: Ingo Molnar >> Cc: Kees Cook >> Cc: Bjorn Helgaas >> Cc: Peter Zijlstra >> Cc: Andy Lutomirski >> Cc: Logan Gunthorpe >> Cc: Andrew Morton >> Cc: David Hildenbrand >> Cc: Lorenzo Stoakes >> Cc: "Liam R. Howlett" >> Cc: Vlastimil Babka >> Cc: Mike Rapoport >> Cc: Suren Baghdasaryan >> Cc: Michal Hocko >> Cc: "Yasunori Gotou (Fujitsu)" >> Fixes: 7ffb791423c7 ("x86/kaslr: Reduce KASLR entropy on most x86 systems") >> Signed-off-by: Dan Williams >> --- >> drivers/pci/Kconfig | 6 ------ >> mm/Kconfig | 12 ++++++++---- >> arch/x86/mm/kaslr.c | 10 +++++----- >> 3 files changed, 13 insertions(+), 15 deletions(-) >> >> diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig >> index f94f5d384362..47e466946bed 100644 >> --- a/drivers/pci/Kconfig >> +++ b/drivers/pci/Kconfig >> @@ -207,12 +207,6 @@ config PCI_P2PDMA >> P2P DMA transactions must be between devices behind the same root >> port. >> >> - Enabling this option will reduce the entropy of x86 KASLR memory >> - regions. For example - on a 46 bit system, the entropy goes down >> - from 16 bits to 15 bits. The actual reduction in entropy depends >> - on the physical address bits, on processor features, kernel config >> - (5 level page table) and physical memory present on the system. >> - >> If unsure, say N. >> >> config PCI_LABEL >> diff --git a/mm/Kconfig b/mm/Kconfig >> index 0e26f4fc8717..d17ebcc1a029 100644 >> --- a/mm/Kconfig >> +++ b/mm/Kconfig >> @@ -1128,10 +1128,14 @@ config ZONE_DEVICE >> Device memory hotplug support allows for establishing pmem, >> or other device driver discovered memory regions, in the >> memmap. This allows pfn_to_page() lookups of otherwise >> - "device-physical" addresses which is needed for using a DAX >> - mapping in an O_DIRECT operation, among other things. >> - >> - If FS_DAX is enabled, then say Y. >> + "device-physical" addresses which is needed for DAX, PCI_P2PDMA, and >> + DEVICE_PRIVATE features among others. >> + >> + Enabling this option will reduce the entropy of x86 KASLR memory >> + regions. For example - on a 46 bit system, the entropy goes down >> + from 16 bits to 15 bits. The actual reduction in entropy depends >> + on the physical address bits, on processor features, kernel config >> + (5 level page table) and physical memory present on the system. >> >> # >> # Helpers to mirror range of the CPU page tables of a process into device page >> diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c >> index 3c306de52fd4..834641c6049a 100644 >> --- a/arch/x86/mm/kaslr.c >> +++ b/arch/x86/mm/kaslr.c >> @@ -115,12 +115,12 @@ void __init kernel_randomize_memory(void) >> >> /* >> * Adapt physical memory region size based on available memory, >> - * except when CONFIG_PCI_P2PDMA is enabled. P2PDMA exposes the >> - * device BAR space assuming the direct map space is large enough >> - * for creating a ZONE_DEVICE mapping in the direct map corresponding >> - * to the physical BAR address. >> + * except when CONFIG_ZONE_DEVICE is enabled. ZONE_DEVICE wants to map >> + * any physical address into the direct-map. KASLR wants to reliably >> + * steal some physical address bits. Those design choices are in direct >> + * conflict. >> */ >> - if (!IS_ENABLED(CONFIG_PCI_P2PDMA) && (memory_tb < kaslr_regions[0].size_tb)) >> + if (!IS_ENABLED(CONFIG_ZONE_DEVICE) && (memory_tb < kaslr_regions[0].size_tb)) >> kaslr_regions[0].size_tb = memory_tb; > > A stupid question, why we adjust virtual kaslr to actual physical memory > size at all rather than always use maximal addressable size? The original changelog that introduced the changes has a detailed explanation, IIRC. Balbir