From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from PH0PR06CU001.outbound.protection.outlook.com (mail-westus3azon11011002.outbound.protection.outlook.com [40.107.208.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7C8B5503BC7 for ; Fri, 18 Sep 2026 15:40:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=40.107.208.2 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789746014; cv=fail; b=PwKEPDg231PcB7MlxZA1/qSQjCJcAnIxIcn7ciQ1cX1xMPoHw5pu8+PUR/fwGlBLqpZOW+kgxXum9Np4UtjS88yLvpXjNelPapWCz9/1bTXyQHrKvMsRvYwNI6/bkQOlohTp5uHUkyqRCoQiZezWZlyEC602FGkYLADZvWTNm8U= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789746014; c=relaxed/simple; bh=4ydLx4xsBr5j0lmpJR5zCZVkiSjiB1fshoN7wZTladc=; h=Message-ID:Date:Subject:To:Cc:References:From:In-Reply-To: Content-Type:MIME-Version; b=HXNgxg5Rwwr0woyS+LscziLSElG/FwpMmFzJFbTPsD6Hc8W2i6UAAJB0DayUlskqlM7AZIL0M2o6gvNovx2h+zfFkBkMXHG3/jVBUtrZP4Ikxfw2+oQuVj7fAfGgwbytXAN3y4jN4k2Pd7uhCdjDZ/IFl6N40butV3l3PuF3LEA= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amd.com; spf=fail smtp.mailfrom=amd.com; dkim=pass (1024-bit key) header.d=amd.com header.i=@amd.com header.b=PxVg7uY7; arc=fail smtp.client-ip=40.107.208.2 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amd.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=amd.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=amd.com header.i=@amd.com header.b="PxVg7uY7" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=hgnyZWzxVCagYI0Whl+pgi66n4GHhRJhBbMqJ5Dz6xM/o1xneS+T+u46RVwLkDL+ryZhs0Os6JzhqakOF9ssZ4afa2DMnIJ3Y25A4e7SesqHjXT05ahyCX9g5lhFkbJFaeObZWAobxDE9FRBNM/C3JJODs8WSXmsShSckk/PFoAtNHlcRq7/lq/YeDaefVcL23y2TiyzTBpvu40KvJVcKDzVSa0aelD3DaQoNpAIUbu2+wh1wca1NjokpBh6+1vAW/o5AqxJAz9fdHCmJr/nrdvyrsu5fUglYkEt1Yh4RibeOHx/dcOi4vhEoCqCigYntsEX9vLyCzau4b4041maSA== 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=rFbBxOaScdg6xEZQzkaCwNVv4e/dbfNEJxqr2f2h0kE=; b=c/9K2k7LV1YsVkefWFUVPrDQXWEMfO7SiDKf6AC0IbmFejlld9t73sDZeH/OxumGjGlfCQq56+Ll4fCalCWamTXMTOuihXwfrkJ5YAQkopI9xcI8oromSju2sBvaOdtRdgO5AtsmzQKyXEd9h34Jfd0kJdnhzq+X6nNnAZI2+nH1zPJWlsuAWfzTbIreQSBp2dcpK7v1FCrB+AM1rdGm/2B2mB1GFDnniI7aJNLH7rMy4Tr/hNLfh4RknOJyKGpG6tEC9QQ1JGUaV8Qc28+WWXsRZogV9Xb98PJ4Li3wJU5f0u2z/DW+GmvxlDt9RWwzkZ8WzPO0f5d4VySiqyBXfA== 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=rFbBxOaScdg6xEZQzkaCwNVv4e/dbfNEJxqr2f2h0kE=; b=PxVg7uY7SHh9yWNo49lrjDllvG5uiaJTylEagW8xkdmSWDYJeh82bHuyrBXNq9356whlLrYaSWt3XbWdiuVnz+5cqAY+alkjuIJvu+rVf653DfgdPwG89k5XnKHxRo2tcYI1Ad5sTALvRaOaFKqBRLr6lQU/8N92+xRVI0Fczoc= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from PH7PR12MB5685.namprd12.prod.outlook.com (2603:10b6:510:13c::22) by PH7PR12MB6954.namprd12.prod.outlook.com (2603:10b6:510:1b7::21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.428.13; Fri, 18 Sep 2026 15:40:01 +0000 Received: from PH7PR12MB5685.namprd12.prod.outlook.com ([fe80::ce69:cfae:774d:a65c]) by PH7PR12MB5685.namprd12.prod.outlook.com ([fe80::ce69:cfae:774d:a65c%3]) with mapi id 15.21.0428.011; Fri, 18 Sep 2026 15:40:01 +0000 Message-ID: Date: Fri, 18 Sep 2026 17:39:55 +0200 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 7/9] dma-buf: system_heap: Enforce shared-granule alignment for cc-shared buffers To: Jason Gunthorpe Cc: Catalin Marinas , "Aneesh Kumar K.V (Arm)" , linux-coco@lists.linux.dev, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, iommu@lists.linux.dev, Marc Zyngier , Marek Szyprowski , Robin Murphy , Steven Price , Suzuki K Poulose , Thomas Gleixner , Will Deacon , Sumit Semwal , "T.J. Mercier" References: <97c30fce-9bda-4c61-b1b9-10297b89c8d9@amd.com> <20260918153642.GD11599@ziepe.ca> Content-Language: en-US From: =?UTF-8?Q?Christian_K=C3=B6nig?= In-Reply-To: <20260918153642.GD11599@ziepe.ca> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-ClientProxiedBy: FR4P281CA0198.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:e5::13) To PH7PR12MB5685.namprd12.prod.outlook.com (2603:10b6:510:13c::22) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH7PR12MB5685:EE_|PH7PR12MB6954:EE_ X-MS-Office365-Filtering-Correlation-Id: 4e5f8145-6547-4ea3-13e7-08df159b19f1 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|23010399003|1800799024|376014|7416014|18002099003|22082099003|4143699003|10067099003|56012099006|11063799006|6133799003; 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:PH7PR12MB5685.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(366016)(23010399003)(1800799024)(376014)(7416014)(18002099003)(22082099003)(4143699003)(10067099003)(56012099006)(11063799006)(6133799003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?ZFkwOVlEaUErUjJKTjVHT1diWm5zNkF3TUU1a1NaWEJrRzVmSUZGZWZHbXBF?= =?utf-8?B?Qnd1b1orRUxYYUhET0lUcC91cFRRcnBUZ1pzR1FTSkJHL0pWb2p2b1NBc01n?= =?utf-8?B?c3gxSFJiNmNDblBKZ3ViNkdGc0R5NXNFb0NSRTJjd1AzWnRQL2s5VEhUL0lh?= =?utf-8?B?anQrT0QyVVdPWlF3bStnb0lrOEZ3VUJidXh5ZTZFMy9PeTdtRHhIWUlhTlh6?= =?utf-8?B?Q3ZmS2RJSkdDSVJraXpPU2JzcmV6QThHdzM0NkxJM251QjNROWxLelZRSUVt?= =?utf-8?B?ZjZWelA1SEE0eENqVEZva0NUdUhMSEc3R1hiWG5wUUFrb0NTdjRRRjYweDE5?= =?utf-8?B?dTFENU9TOFg5djE3THVZZ1FlV29DcUhOaGdvRnFmcUlMR1RGS003aHM0TGxN?= =?utf-8?B?eXV6cjFINnJFK1hOMzhOOUtuT0xrT3FtRUZJeGhvbjFqUm1HQ0RxcnM1TXBp?= =?utf-8?B?Rm9IOHo1MDI3b09DRytOT3NIZ29scTBuVzhMQVUyS1JkL3NzL2VBMzQ4bzZt?= =?utf-8?B?ZEN1N3RxNVM1eDBDQnQxenYxbDVhenEwREx0WmNnUlpjTGthbDVYQVMyZUc3?= =?utf-8?B?cE96WDlLYXJ2SkVwWnlSWld2ZEYvd1I5YVpLNnBxeUpmTjlkZGZuV3dEWng3?= =?utf-8?B?YTR2ckNXbUF2VjdpNXhHRTI3VG91SnhXYXRqcnAvT0dvQlBZQ0FZdzl4Zmd5?= =?utf-8?B?VkNYZXEwbFpqVkdOMEtYWHl0SEhHQUZMbWpicWZRVHk4UGR6SVJCcUpsc2RP?= =?utf-8?B?REhCSHhHb3lWL2ZXVEVlSGhvaHZoVVc2WDBoQ2R4NVZKL3p6bUJ4V1EybnhV?= =?utf-8?B?L0NVL09tcTk4YVk0c2lYaGJESnFqQUZqbUk1TDBCcS9RTjBUdisrcTRyK2dP?= =?utf-8?B?Y3EwTEZ2eTNkSmZQQUQzSUJUbmxMQU91N2dpSUNkdDBQd2JRUGJRV2xySThu?= =?utf-8?B?M1dNUWt5NmpxS3JwU252UnBRencvTkxORmNpdUNLQ2o2Z2N4SExCUkhwamov?= =?utf-8?B?MVhjUjBpTW5XU0tTOGdsMUFzN044a2RjUk9OZmFSQlluVGdFaGx4aXcyQkw5?= =?utf-8?B?cG11L056VVN2aUljK0FDWEREVUUwRjhNenZWUmFrTklqeStLSEdtTDJqb3dE?= =?utf-8?B?ZVhveUZTQUNENUlwKzN1d0IzZ2V0enpOL3cxVi81N0JPYmpwZXlON2pTV3Yv?= =?utf-8?B?U1JOS3ZyTE5VT1BqZVk1MEtJYWpaTWRUWEZUYnYzaVlCWGdLM3NaTTB5MnZz?= =?utf-8?B?eFRDYU43eTBnTXBxajU5SHFmTzIrdCtjL0ZCNlNWVEU4SWorYmU3ZjloUkxr?= =?utf-8?B?d2tpblV6MmsrVmJnT0xOamd2dmhBYTFEZEtQeE80SWR4U2QyMkp0dVcrUk41?= =?utf-8?B?SEZwSUVxbVZQSjhvdVQxM1pjL1BNZC9JRDRMNXozSVdsVFMwQUprejgwckxn?= =?utf-8?B?SEZtUFZXdVg3bi8zREFuMW5pV2xvZmlYbUFNbHBGaFEvVFZlTXhwQjV0Z0Z4?= =?utf-8?B?aytDZ2hqRjVaL2xoc0hoTGxzNGZ1bWJPUUFzT2NJRkVZUi9ZWkpJUHVlZjZN?= =?utf-8?B?dDJianJ1dUthUkU1aHNFU2lndERvcEt5eUUrVGdTZUViYnZpam91bXZ5eUJE?= =?utf-8?B?UUJvSHlrNVdNNUFQempjQ3pETGQ0WnVJQ2lJeVZ0ckFlRnRrOTJPbFVIalEz?= =?utf-8?B?M0llNzZWUHNoS00xeC9XM21TYkNJVzNxUEpYNDhNSkM4UkJ4TEZwSXNWdzRB?= =?utf-8?B?Y2QrMWErU0lkRHZjVTh0YlVqRkVwd3VVeW5BcExMY2xReTRTVTBTRkdnTkxC?= =?utf-8?B?a0NXbjlIQnY1YzNDTFBzTEJzSXJWaEl0R1VBQmR2YmpaTVZFSWVxYnNxWUJ0?= =?utf-8?B?U09UT2pENGdJV0dHZU9QbHpFOHRPZ0RCN2dVdlo2bTlla1RKMElCQnhscUYx?= =?utf-8?B?VzM0VThBV1dtM1dZUFhEcjBtcHk2bFpzNUFmU3dFY0pWdm9ra0F1SFI3ak9w?= =?utf-8?B?TFhYWGZqSXFBQnBkenNiQTRPR3RuOWc5Mmk0OUJxTC8zYXdmTmlRMWV3cDB5?= =?utf-8?B?R2NzMUQyTXR2cHNhcDVwOC9DcVY5YjFaYmxQUHkvc2V0MURiRnFvWDRKYjZt?= =?utf-8?B?WHFoTTRGYUdlMTVRempyNHRWOFMxNFJuNDRFc21sUjQ5OVBWVVdjQTNQS2xP?= =?utf-8?B?V1lIdXVYaXNTSWdxQ3FFYkdqcnlGWTZRZjdSSDcwNUl5cUN1VFJ2UFE5cCt5?= =?utf-8?B?ckltM1BIL1FUVW9Wcm1ITjZleCtjd1lKeGxGSTRnYkllOFJtQTJmN2lIVVA0?= =?utf-8?Q?bjwNx0n6gInVqG3K4Q?= X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: 4e5f8145-6547-4ea3-13e7-08df159b19f1 X-MS-Exchange-CrossTenant-AuthSource: PH7PR12MB5685.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Sep 2026 15:40:01.0673 (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: WUwnyzJHxu5QKshFRMuQ90q34KRYn7MvnIAUVq7wBS3D3IvS6fhtfWGkdQdtqhJD X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB6954 On 9/18/26 17:36, Jason Gunthorpe wrote: > On Fri, Sep 18, 2026 at 05:23:32PM +0200, Christian König wrote: >> On 9/18/26 17:16, Catalin Marinas wrote: >>> First, none of the DMA-BUF maintainers have been cc'ed. It might be fine >>> for an RFC but this series got to version 6. We need their feedback. >> >> Yeah, thanks for doing this. >>> On Fri, Sep 04, 2026 at 04:04:50PM +0530, Aneesh Kumar K.V (Arm) wrote: >>>> The system heap can allocate buffers that are decrypted and shared with the >>>> host. For confidential-computing guests, those shared buffers must cover >>>> whole shared-buffer granule; otherwise a userspace mmap of the dma-buf may >>>> expose only part of a host-managed granule and allow unintended access to >>>> adjacent private memory. >>>> >>>> Require cc-shared system-heap allocations to have a size aligned to >>>> mem_cc_shared_granule_size(), and allocate pages at least as large as the >>>> required granule. Keep the allocation bounded by the existing heap orders, >>>> but fall back to an exact minimum-order allocation when the required >>>> granule is not one of the preferred heap orders. >> >> Uff, I don't think we can do that. >> >> That is massively platform specific behavior in a non platform >> specific code. > > What we really need is an allocator API that does all this for the caller. > > It has been pointed out a few times, Aneesh maybe you need to try to > tackle that? > > dmabuf heap just wants > > 'allocate me an array of shared folios totaling XX bytes' Yeah, I know at least two other use cases for that as well. > Arch code can figure out how to do it. If some ARM configs only give > order 4 folios or whatever then dmabuf heap doesn't care. The fundamental problem is that DMA allocations are highly architecture and device specific while Linux memory allocation APIs are generic. Christian. > > And solve the double/triple zeroing problem. > > Jason