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 EA013D1267A for ; Tue, 2 Dec 2025 22:20:45 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id F326F6B0010; Tue, 2 Dec 2025 17:20:44 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id F098A6B0011; Tue, 2 Dec 2025 17:20:44 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DF88D6B0012; Tue, 2 Dec 2025 17:20:44 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id CC7A96B0010 for ; Tue, 2 Dec 2025 17:20:44 -0500 (EST) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 8BAC3132A79 for ; Tue, 2 Dec 2025 22:20:44 +0000 (UTC) X-FDA: 84175951608.02.C526AC2 Received: from SN4PR0501CU005.outbound.protection.outlook.com (mail-southcentralusazon11011063.outbound.protection.outlook.com [40.93.194.63]) by imf14.hostedemail.com (Postfix) with ESMTP id 9739D10000E for ; Tue, 2 Dec 2025 22:20:41 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=Nvidia.com header.s=selector2 header.b=TCCaZw9t; arc=pass ("microsoft.com:s=arcselector10001:i=1"); spf=pass (imf14.hostedemail.com: domain of balbirs@nvidia.com designates 40.93.194.63 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=1764714041; 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=+7BRKgMa12mEyAcD4Gg+ZxUH5q/w1fresXx3e5ni2gg=; b=oHhMHcneZphpG/sQ7Mpw8lhq18bAvctaH28/jGiH1ytihJpTYKqIy5ywp+412zPLSaBl1k xfeob2/RqGBfMACyUwaExa8KTySOH5uObfHCBueSyDCHRs/jfTeSS4OAgfh5X8tyfdourQ 9a4mP2iZZ6SHftodXADQiUxMauLQPRI= ARC-Seal: i=2; s=arc-20220608; d=hostedemail.com; t=1764714041; a=rsa-sha256; cv=pass; b=4lzelBVX+cPU8MfgqnILoWLpVDM0gp8NIlHXHXZm0NVJXbaFt457HKwc3WOkPJCXL4msuV LqmImFZl22c1jsDId3cS62Og1oajRjBO3oPHhJZF6r1NcLB4iCJ0ZXZEghb36os6/1BdxI EL61v6S9Y0+SvjjTBXS38N7G1WmuV3w= ARC-Authentication-Results: i=2; imf14.hostedemail.com; dkim=pass header.d=Nvidia.com header.s=selector2 header.b=TCCaZw9t; arc=pass ("microsoft.com:s=arcselector10001:i=1"); spf=pass (imf14.hostedemail.com: domain of balbirs@nvidia.com designates 40.93.194.63 as permitted sender) smtp.mailfrom=balbirs@nvidia.com; dmarc=pass (policy=reject) header.from=nvidia.com ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=EAViGX7FH6L7irn1EhTvRjFUpQ2SJI7/RmD8TvZAkC204jcx77BMy92AvQhIGJLNdMmybpsJXRlzUTXOvO1swng8TRV496CHuNQhP29XPPRBFtgNryJYN1hjlS8OpFk/QlvAfGDDy21JTOXrSbyIAmRdiiSlQt2E13N2HggFtyeeA/2x/cOr6qA/rdfxrQgh7uXQ3deA1OtKSQIQUQDVc8u0ag59LrWztbD7DeJFnzqzcxHhTxLdTPkwnVhKLtgLXfX+Y2xFatDBv4Wukm5MIPP/DAN9DAu/Aq+quou4x46Ko6dIk9WeMhCJCFoAYjCzwQSQK6eVnvHUrJsXe4wFOw== 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=+7BRKgMa12mEyAcD4Gg+ZxUH5q/w1fresXx3e5ni2gg=; b=sdVbUteJbPqpIlN9qeW1mt/V+bmibMYKPRImiwvadUrYD/EeTKygF3SOlrg0I33m1sqalufNMFQ9WGMtLo4HgoLeoIjGGO9dDFPgVQGB2eTME9N80U7P8CSoZsecKFOkrZi9k9oIbex0rml59Cz2n73duLpDO9YezNTgf3ahaxsr2VY+4pK748CKnoJLczRezqOTWhWfFNhDuUEP1rWrBw6chsY410mlLmaQuR2KI3z1NW+0bmHrxJ27+ty7MZjjc0JZSV2Vd8B0cK4qROw2l/E3K54c3fBNNcm8gzjuyAAk0XrdPRiaAXLbPAfljyr5fzWq0ET90YPruDUlYTDEQg== 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=+7BRKgMa12mEyAcD4Gg+ZxUH5q/w1fresXx3e5ni2gg=; b=TCCaZw9tsC+UYMuCnpWzPNqrJKDRs7U8IJ3gbF4ukREymAPhxGk7t4j17gpNaMec8ztPzrpGIZqcMDXxS/UL9RdeWidM6yWWzWI/LvygcW7tTQ36OihY1JTDNBpzRu0HvDaB4XK8mKvmu1ZozamlOagDg7KGVPWE2a+zBpmawRIyNe9TgHVB0QOmMmDtlYpCZenVTgDIgC1Vxk3K0zniP1Qi+lQldw1Y/8tgKtoUigjdWqtrLYYx3SyR3Cm3ahj0uyG8g9AA4/qYfs6OvZs1E8ewf8LZHnwxwWGL6PKJOMXvIL0dy8tQ/Qhm8iyFMnUhNzHT45FYLiJyP9SWyjb31g== Received: from PH8PR12MB7277.namprd12.prod.outlook.com (2603:10b6:510:223::13) by SA1PR12MB5669.namprd12.prod.outlook.com (2603:10b6:806:237::6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9366.17; Tue, 2 Dec 2025 22:20:37 +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 15.20.9366.012; Tue, 2 Dec 2025 22:20:37 +0000 Message-ID: <8243f83c-6485-4632-816f-4cf103d0871f@nvidia.com> Date: Wed, 3 Dec 2025 09:20:31 +1100 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 0/6] Remove device private pages from physical address space To: Jordan Niethe , linux-mm@kvack.org Cc: matthew.brost@intel.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, david@redhat.com, ziy@nvidia.com, apopple@nvidia.com, lorenzo.stoakes@oracle.com, lyude@redhat.com, dakr@kernel.org, airlied@gmail.com, simona@ffwll.ch, rcampbell@nvidia.com, mpenttil@redhat.com, jgg@nvidia.com, willy@infradead.org References: <20251128044146.80050-1-jniethe@nvidia.com> Content-Language: en-US From: Balbir Singh In-Reply-To: <20251128044146.80050-1-jniethe@nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BYAPR05CA0073.namprd05.prod.outlook.com (2603:10b6:a03:e0::14) To PH8PR12MB7277.namprd12.prod.outlook.com (2603:10b6:510:223::13) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH8PR12MB7277:EE_|SA1PR12MB5669:EE_ X-MS-Office365-Filtering-Correlation-Id: 0d632118-05af-454a-5dd7-08de31f10515 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|10070799003|366016|1800799024; X-Microsoft-Antispam-Message-Info: =?utf-8?B?Nm5icW5MOC9aZjVXVUU4UmJkSnBnd2MvR1AyTzQ1N0ExYzB1RWxKTmEzRlc1?= =?utf-8?B?MFN1YTZRd0hzUFZuYWhNZ2RaVi85eGN6ZlFzRHFTMDdLSEpUY0dCZ3BOTHE5?= =?utf-8?B?VS83WENKU3AxdXBrdkRLS0lZVjV1QXhNQmZhZ0Jwd0JxMnQzcW42TGpmbEZW?= =?utf-8?B?Q0VaYzhKWmRiOWRtM2hZWWU4TFBGR2t6WDdtejRSazZUMWZNdzd0QTNUYjhy?= =?utf-8?B?YTZNSy96MmZ1cExDSlNwTDV4TXU4aU9aK1ZqeThOQ3lRajZzck43dUI5di8v?= =?utf-8?B?RG9WV2lackdTMGF5RzNndzIvanBqQisvUSs0VTg3ZVpFVjNXNVpBd1ZLQnY2?= =?utf-8?B?OHd4QXlCUTZ5N0V4QzNxYkJFM1NhSXRweS8wSmwvbFB1Z3Zoa0x5ZVV2TkNo?= =?utf-8?B?YXdDZGQxajQ2K1pkQmt0S0VrMmNrZkY5dWplbEFKSVZlamNqMGRGaGo4cVhB?= =?utf-8?B?aE1Ob2xMUHVBU2tqbzIwTHRFM3ZHOGY3UTdsVWJqaVZsbDhua1I2SExhOW1H?= =?utf-8?B?bmtBYWpsSnpkTjduRHh3K0gyY3UwTm1xSW5FQVAzTE9YQmE5bDhDUVFxQ3V2?= =?utf-8?B?eG5oS3dCTGlwdTJzam9LR3JXckJ6ZjZmSFRaV0h3eUJKTTRoSjBrbzBFVTVO?= =?utf-8?B?U2YwcHNUM1hmcUdUcExtQlIzNVFaNXdUaHpvUFNXZGJoZ1FhdlEwb0w0V3VM?= =?utf-8?B?NzVzZEtoSHpOTEIrMlRobDZqc09lcVlIaGFuMHhaT1lJZTZJbDNTQjJVMDY5?= =?utf-8?B?ZFVheFdqcHJrVXIxMmNyS1JkdGZtYUpWZ21uZVgwMmE3eTlhbnBETUYxVUlL?= =?utf-8?B?QXlpbzR4K2tGYU9RRzR3ZDNXZEpIT0ZmQkM0TWR6bnFUZ2tBYjZIcnR4WkJn?= =?utf-8?B?OFhxYnV2WEJkS0JYU1MyNjI1YzBaeVgxNHFYWEdMbTdYWkZDUUE2R0NMaUtV?= =?utf-8?B?R1JLa0NyeXJJNzhiTlNzNlgveVBRaHRGUUh4WTJsN2YvY25zKytwa2hNOVRC?= =?utf-8?B?RmhHb2hiZjVKY01sOURxYjZqQ3dBWGN5TjBhMFpUeWN5ZE40eXdpZFVkR2I4?= =?utf-8?B?ZFBXOFBaRm52ZHhob0RLdDFTOEllaWVCZy9KNUw4a3BPSzRQYjZXL0pvcGcx?= =?utf-8?B?c2Q3bWlGTU5hczhad3UvSkxVajZJUENrL2FOQzRsa3piZUVlWXpTdFhlTVVz?= =?utf-8?B?b1hZSS9BcjNQaXhNSTIvM3dPKy9kWGFjZ1pVK05lQVA0K3hvRS9POUU3b2NX?= =?utf-8?B?cUNyZGthU0hCSHh6RERSMWRtb0dBYW5YbUNuM1phSE1mSDJONytnbGVTSWJl?= =?utf-8?B?Qm83R0RMaml4R2VJdm1rei8vcFFaNC9DQS9ZVGlMb2JHTHdPY25nd0N4dVg2?= =?utf-8?B?aUlla2piRXNVeFE1SUF5YkJ4dE95eTNTS25DWE5JdytqNkk2SmZIckUyaElO?= =?utf-8?B?MUpXYlJwdi9ESDJyOGFaS2hVYXVGTC8yc1BGT3hhWlN5eG1SdXZ5VmVHSEly?= =?utf-8?B?cnV5Y09TaWplNWxBcjF5T1RIQi9vMTRqcTNLc2paa3BRRDg2VWZvMFd2cGgy?= =?utf-8?B?YTZ6aExLbVdMeE9kWldiWmtxaHlkNTZTWGxiNWRoN0pDdnIvb2x3dzNJZ3lG?= =?utf-8?B?V01Jd202S2thdFBSOFB3bndjTjY4U2I4YWlWQmRJcjZKalJ2M29RRGtGZkcy?= =?utf-8?B?ajR2WjhmRldLeXhwanB2WUkyM3ZoUHdVQy9nR1FHUk5VRjNnSDk3WVNVclEy?= =?utf-8?B?RzAvRmZ1cDJBNmZSWlFPSWhpR095N3lVSEJ0My9vZU84N0NPYmdsL2RVUWRR?= =?utf-8?B?NDJoRTJ0QVZybkZVNzltMzJ2VVF0ZDJYRXZFV0xJUHBMRk02RmRISkN4SWZo?= =?utf-8?B?OU1SUVBjcnFSQjJPU0Vocm1UbW9FZWY4dmEvanVWQ1RpNmFqOVl2VURja3R3?= =?utf-8?B?YldHa1gzS0c0RXJ2L2JOOGlNR3NuRlNuUk40aEYxVWtXZ1hIMjRQaThlRDhK?= =?utf-8?B?b1hKK2xHeXlRPT0=?= 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)(376014)(7416014)(10070799003)(366016)(1800799024);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?VzlpNEVXVnBaVFVhRnVjaG9ESUhWUGlQUEMyRXFZRWxma0hKMWZXTkJWUW1r?= =?utf-8?B?MmZIZzFhaG9CSWxkWHlHWndYbFREV09ZcndIVHlGVHkvNmhPdXJFY0JuZEdJ?= =?utf-8?B?b015RkdFMWlLVGl4UnhmK3BUSmxiaGozamUySjdtS1gwZ1hhUjlEbWJQVWVo?= =?utf-8?B?aDdNcG0vS2hzYjVlWDNESWRvU0xUWE5wcnp6MFZmTDRITGluaEF5ekE4KzBH?= =?utf-8?B?c29uK3VjNVoyb1g3NXNObmpkN2dXWjdXMnpEbDdsWEU2R0dkWmRNcDFzVkY1?= =?utf-8?B?RDUxUmVJZHdEakJYQVV6SzdLVHpHdDJDQWlZOVU0WEswZ3lqZDRpNWpNbXVj?= =?utf-8?B?bnMxSUlNWEl3M01KSjFxeE1NOEJwSUVnU2twN0RURHJlK3IrOXRCQXUwWWFY?= =?utf-8?B?VTFPeUZ3RjBXUy90VTVSSkFuU1NUcm9CS2M4SkxrMVRObE5BOUltbURaYkxv?= =?utf-8?B?OGlpRVZuU2hTZ0VBQ24vclBGL1h3YituMFNYcXVtZGRCZk9uaGNNTnVSQWJX?= =?utf-8?B?bGFUdWgzaUlZM0luUzBWcGdPbExYRHVyZi9sLzY4MFpvU3JzSDMyUWg2ZEFB?= =?utf-8?B?bnpnL1BjZjJROHVoazNmZEV6QUZQNmtMeEtBcERrb0Zvc3c2RGZYL0ZWVVpT?= =?utf-8?B?bjBzbjBwclNZd1ZjbWxsY0dvQWtCZ0U5RG8zaEdSRXp1T3R5MWJFNlFjdDY0?= =?utf-8?B?TXkwSzlvRlhNVU1sNE4vbjRXeU16K0IrSDBMMnc3RHRqUmQrK09ubmVWUTIr?= =?utf-8?B?aFpnNnlqQ0pNS215YVptRFZoN2hOdWh2dEY3djQ5ZzVaSXIvSU1TMnlWNG1X?= =?utf-8?B?dXV3SGZhd2hxd2ZlbEFDMys3b0JPRkZveWRqbEFTZlpWV0ZOaUhmbEplWkg3?= =?utf-8?B?bnRFRU9jcnpKNko1SFY5bTIrVnFXY05TVm94NVFJZGxMVjB0ZHBYUklsamYz?= =?utf-8?B?RWI2QUZ2OUkvbnNkQzdDajVZOHV1Wm5vK3JoRTlMOFJ3WGZ1a053QVhiNGFm?= =?utf-8?B?ZnE1c1NVWThxYXh1TC9DZEtkbWNlcDJlOC9tMEovb2xoV25reDF4Y1dkQWdH?= =?utf-8?B?clhwRURsRUVQSUZQWXp5UGNRSjBhUHMvMEo2NnJKK29zSWlVMThVa2MxU0hn?= =?utf-8?B?Q1h4TkhZNlpCVzdhdU1SOXFGbTYzdTBhY2I0SVVPV2NRZjBsamVycmVCSkt6?= =?utf-8?B?b2pGVFFXVlBxWmJRWWVMZkg0eEJXSE0zbDNNRFJ0V3hsVW0zWUlVTVU0UldK?= =?utf-8?B?RmZrWnQ2dnNiOFg5V3d4U1c0ZTZlR1RRZ3JnbGNTRmZPYm1hU01wWUFNcVJ0?= =?utf-8?B?QVNacU9JRVQyeWdNdDAwaGdJaDFZQ0ZRQW9Xa0lhSWt3WTRlRGg3VWg5M2g3?= =?utf-8?B?M3NtTTEwVURMdXl5a1VFQi9PRXRxUW5MSWNuNUZBd2duakNGSmp3TW1tSURC?= =?utf-8?B?ZjZ5UG15bWNiWnAreGJjT1htTVhvZGorNGdCejVPeUhKUzNRV0VxdWVaYzQv?= =?utf-8?B?ZVEzbUUwUktVOWs1czhTM2M2SGsvcUFXVG95VmF3dUFjeXpHSDB1ZDBoNTI5?= =?utf-8?B?YjVELytpYVIwcXlzRk1DQW55NDRjdFlKbG53SFh6NmErbk9NVmtuZUVHR0Qv?= =?utf-8?B?NWx0SjBMdW81SmphK212dHZiS2tuVmNXN3BHU2gzZDNqRXdOSXlLOVlKWGJ0?= =?utf-8?B?T1JoWkl3UHpCaWV2VWFDMk1kaDhuZ0wyU2FMTUplVUVRc0EybnY4Qm9HVDhG?= =?utf-8?B?OXNyc1BOVnpSSU1raS9GOG4xSmZPRHBPM2pxOUY4T2JHenVPMDhKVTVldG1Z?= =?utf-8?B?OFZEcExlcDIzamxhSjMxSnVLbG9YRXZSaU5FMTNBNFFMVW0wSEI3UHBhQkUw?= =?utf-8?B?aTRtbHp1dE5KNHJCSzFhS2IxNE8xNmw2U1hwbzhJeHMxYVlEY3NESU5DK0Rx?= =?utf-8?B?dUxRcTVISUd3L21WTis5alBCUnpmSjdXSkdoVFpjMG5YNjdhbWFwNyttbTh1?= =?utf-8?B?OU0xYWcxUXhUendmbGRUbmxBT3hRSkdCNy9vemo5a282TXA1MmtlWDc1RElW?= =?utf-8?B?WFF0ZW9PNnNTRFlGWWtzVTBsUUY2U0todFJKdlZHZU5lVEd1cEIzU1EwN1Zq?= =?utf-8?B?WVcvZmtrSlJaNUJNSmtBUy9YbWRxd21QTk9lanNlajJZaVJVMzQwVnBLMm1B?= =?utf-8?Q?KMU9z0df+YodZFzB1tu6kVW15o20YSSsSv6v2Ct73uAh?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 0d632118-05af-454a-5dd7-08de31f10515 X-MS-Exchange-CrossTenant-AuthSource: PH8PR12MB7277.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 02 Dec 2025 22:20:37.7447 (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: 1rq0fUc8P3f3zHjbt0e4wtwkZIMrAnDgQ20Xp4zn9UZlkDG0PoEdD4f81PhxZ7KJWZMpk7B0Gx5jQXBlvhFWNA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR12MB5669 X-Rspamd-Server: rspam12 X-Rspam-User: X-Rspamd-Queue-Id: 9739D10000E X-Stat-Signature: zhhk13zns7s5rgucqt9wne3xsioto35f X-HE-Tag: 1764714041-490758 X-HE-Meta: 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 YRPwNlVF /yFcDJhS08CJlxNNJNavufIgSsD6JaJHmdaY9+MJKhhxYDf9C3ih16PUPiUc9QVHNPt2KGl1lbfLHo4ot++6vGgp9lmuemKz2f5KGSJaCWH++qyQ1HzfW/jfd5rCtJjv0RL0gJcU/7jC0EVuEko6foh25xIEs8zy3h/mXEn/euS+vaZlIdFrbNz+YS5Sc++mcTva8X5djl/CIS5LPIJOV912VuWRpbAeQYog+IrFkO7VukmP6kt79E5aWisyVVeEKjMpSFY1e31/5sa6zIJcGRzCMfg/i5rwxHTbS0eUTrYW/NFz0fFADh78s37xfiQNao6tRyXElp4NU4j67upYDFstZcvngEMbJvvJUWjCLw+D+aKJua1Ex5zNQz7PxR5Jw65OeG2v7Akl+JrnaJm7wpDEY9IepDxun9IaWixSg+whAZC17/LRNK2Hq9vpatCSzDSK5xUZ7fH6KtvM= 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 11/28/25 15:41, Jordan Niethe wrote: > Today, when creating these device private struct pages, the first step > is to use request_free_mem_region() to get a range of physical address > space large enough to represent the devices memory. This allocated > physical address range is then remapped as device private memory using > memremap_pages. > > Needing allocation of physical address space has some problems: > > 1) There may be insufficient physical address space to represent the > device memory. KASLR reducing the physical address space and VM > configurations with limited physical address space increase the > likelihood of hitting this especially as device memory increases. This > has been observed to prevent device private from being initialized. > > 2) Attempting to add the device private pages to the linear map at > addresses beyond the actual physical memory causes issues on > architectures like aarch64 - meaning the feature does not work there [0]. > > This RFC changes device private memory so that it does not require > allocation of physical address space and these problems are avoided. > Instead of using the physical address space, we introduce a "device > private address space" and allocate from there. > > A consequence of placing the device private pages outside of the > physical address space is that they no longer have a PFN. However, it is > still necessary to be able to look up a corresponding device private > page from a device private PTE entry, which means that we still require > some way to index into this device private address space. This leads to > the idea of a device private PFN. This is like a PFN but instead of > associating memory in the physical address space with a struct page, it > associates device memory in the device private address space with a > device private struct page. > > The problem that then needs to be addressed is how to avoid confusing > these device private PFNs with the regular PFNs. It is the inherent > limited usage of the device private pages themselves which make this > possible. A device private page is only used for userspace mappings, we > do not need to be concerned with them being used within the mm more > broadly. This means that the only way that the core kernel looks up > these pages is via the page table, where their PTE already indicates if > they refer to a device private page via their swap type, e.g. > SWP_DEVICE_WRITE. We can use this information to determine if the PTE > contains a normal PFN which should be looked up in the page map, or a > device private PFN which should be looked up elsewhere. > > This applies when we are creating PTE entries for device private pages - > because they have their own type there are already must be handled > separately, so it is a small step to convert them to a device private > PFN now too. > It'll be important to distinguish between the two PFN's and ensure that they are not treated as being interchangable > The first part of the series updates callers where device private PFNs > might now be encountered to track this extra state. > > The last patch contains the bulk of the work where we change how we > convert between device private pages to device private PFNs and then use > a new interface for allocating device private pages without the need for > reserving physical address space. > > For the purposes of the RFC changes have been limited to test_hmm.c > updates to the other drivers will be included in the next revision. > > This would include updating existing users of memremap_pages() to use > memremap_device_private_pagemap() instead to allocate device private > pages. This also means they would no longer need to call > request_free_mem_region(). An equivalent of devm_memremap_pages() will > also be necessary. > > Users of the migrate_vma() interface will also need to be updated to be > aware these device private PFNs. > > By removing the device private pages from the physical address space, > this RFC also opens up the possibility to moving away from tracking > device private memory using struct pages in the future. This is > desirable as on systems with large amounts of memory these device > private struct pages use a signifiant amount of memory and take a > significant amount of time to initialize. > > Testing: > - selftests/mm/hmm-tests on an amd64 VM > > [0] https://lore.kernel.org/lkml/CAMj1kXFZ=4hLL1w6iCV5O5uVoVLHAJbc0rr40j24ObenAjXe9w@mail.gmail.com/ > > Jordan Niethe (6): > mm/hmm: Add flag to track device private PFNs > mm/migrate_device: Add migrate PFN flag to track device private PFNs > mm/page_vma_mapped: Add flags to page_vma_mapped_walk::pfn to track > device private PFNs > mm: Add a new swap type for migration entries with device private PFNs > mm/util: Add flag to track device private PFNs in page snapshots > mm: Remove device private pages from the physical address space > > Documentation/mm/hmm.rst | 9 +- > fs/proc/page.c | 6 +- > include/linux/hmm.h | 5 ++ > include/linux/memremap.h | 25 +++++- > include/linux/migrate.h | 5 ++ > include/linux/mm.h | 9 +- > include/linux/rmap.h | 33 +++++++- > include/linux/swap.h | 8 +- > include/linux/swapops.h | 102 +++++++++++++++++++++-- > lib/test_hmm.c | 66 ++++++++------- > mm/debug.c | 9 +- > mm/hmm.c | 2 +- > mm/memory.c | 9 +- > mm/memremap.c | 174 +++++++++++++++++++++++++++++---------- > mm/migrate.c | 6 +- > mm/migrate_device.c | 44 ++++++---- > mm/mm_init.c | 8 +- > mm/mprotect.c | 21 +++-- > mm/page_vma_mapped.c | 18 +++- > mm/pagewalk.c | 2 +- > mm/rmap.c | 68 ++++++++++----- > mm/util.c | 8 +- > mm/vmscan.c | 2 +- > 23 files changed, 485 insertions(+), 154 deletions(-) > > Balbir