From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from CH4PR04CU002.outbound.protection.outlook.com (mail-northcentralusazon11013013.outbound.protection.outlook.com [40.107.201.13]) (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 CE9A42C11F5; Fri, 17 Oct 2025 11:55:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=40.107.201.13 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760702135; cv=fail; b=reKxv91va3a2818iTUjNHhDtn+Kjmp7ALTJMdl/2ZlPEDR7iYGP/+eappluAgyNqlOQvPAwQkzvUA3mjEcUA9sGrp7vb1mazONJwTEp+wX/B12irFB0wr6N5OeoR6cXXcCEo/3jFrdR9NyLDvD98PWTnIdxYkpYFXFpRhxtN4r0= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760702135; c=relaxed/simple; bh=/nbCotrcrlNguseUTMPrWss2V9a2q2IXI9UKPymYkO8=; h=Date:From:To:Cc:Subject:Message-ID:References:Content-Type: Content-Disposition:In-Reply-To:MIME-Version; b=IWqbkAGKS13IwNgwhTqnKigtAtFLiTSo6QdVM/6GeQ7Lip5PZB4G3x7itkP13W4LntQbPktR1JRupkFmmRIqFKn0ADtk1E/Ap+mT3nw5QInlNJuCQCSX+GrbjEm3TE9tqEiFl8f58nnRkyAeGDkZWWPlHocGh+kGWnHEn06Hvfk= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com; spf=fail smtp.mailfrom=nvidia.com; dkim=pass (2048-bit key) header.d=Nvidia.com header.i=@Nvidia.com header.b=VXhdKugO; arc=fail smtp.client-ip=40.107.201.13 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=nvidia.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=Nvidia.com header.i=@Nvidia.com header.b="VXhdKugO" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=Oa+65+KY5htx5BInWyP/BPZzPKyiPiK+AHeoshTrfE7gxvWg/1qPQX9O55pMgbsnH9OLGPJk/rT9g/uErheo/BdQiRtHn1NBNaUDN8/SR4MF+IMQFjn8uXztMsCp6cxRIYNSpBf6VGRuMKBeQZ2NOHxSJoHGtDmpwrT/ErNe+iqCfCL6bDkVBl2R9pMxkHnRiXUq36LS6FO3v9KDk9wKtdpvRznabvIaIKo0lFjdMwe/UVt9CHtl5XV/8TgGbfD+RHy+BW/sZ6mvxe46+TLrwDA1xvOpiUP4L7hOCaRxIZPUU8OskxC3/R3q4+AZJgomYdYKVoKLkeLJBwUoUguazQ== 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=K74F9KGlgPlbL6DMmMBJ5agyEfEeQoSW0boygtkOuXE=; b=ckWorcjHpV57VdN5JMinqHVnqJOqZbjz/WNvzNNeEsAyLK/NpMqGm7D2BdbQFPKWChwmK66At07SK/NRUn7uRdzRqdHm3zTyPuQZex4AzvI3HTCJkVdeF3dDEW1hrR34BPs3Rv31pVredYL5+spFXtHiEbGXzIfcqOgGJGyi8uk3o8/TlpoM/4NIOCbif8Nyfc98WqcMkoc25PT/EPV8p43++NExF76FEo/eWdHkoQcGAqoQSNt/D+AFROOd3+Nkj3nelsoLaAUP8x+6Jdfww6Hl2FxcA+6fzLDd7BcHXgA9nRCR44U/aBqnqOyt0sRoYIgyWpxP8A/f7v5aff0kTg== 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=K74F9KGlgPlbL6DMmMBJ5agyEfEeQoSW0boygtkOuXE=; b=VXhdKugOGK49/nJxhfFvDNWdU2lUPUubcDePQlFjI+9uzFE62XjWkyK1RJvO4/Yf7LmvfXKH0qcFsclyjkf1UF3pKzXWFmWpouQmneb2tt3YTwWRkPIoqxa0wgmO5RKH75WlR4sWWeOM/mCRESQB+suDguRCajSQZxs6AUsxs0Pq/Ph6ai045Rq4tYqmORJG6rc1KUEjnbL6r1jWaXzDh67rnI/wl0x87ILYUYuEx5C5hCKEOtkNU/ur2wnI5+5h4jAa5OEG8wkGQq5U9HJIJpq9K74kCdsSAQI+SUMixMRYIEhgTJE4h4L4cEZLovvjyaQbBOOqbhvEorqLFsXxEQ== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from MN2PR12MB3613.namprd12.prod.outlook.com (2603:10b6:208:c1::17) by PH8PR12MB6938.namprd12.prod.outlook.com (2603:10b6:510:1bd::8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9203.11; Fri, 17 Oct 2025 11:55:29 +0000 Received: from MN2PR12MB3613.namprd12.prod.outlook.com ([fe80::1b3b:64f5:9211:608b]) by MN2PR12MB3613.namprd12.prod.outlook.com ([fe80::1b3b:64f5:9211:608b%4]) with mapi id 15.20.9228.010; Fri, 17 Oct 2025 11:55:26 +0000 Date: Fri, 17 Oct 2025 08:55:24 -0300 From: Jason Gunthorpe To: Christoph Hellwig Cc: Leon Romanovsky , Alex Williamson , Leon Romanovsky , Andrew Morton , Bjorn Helgaas , Christian =?utf-8?B?S8O2bmln?= , dri-devel@lists.freedesktop.org, iommu@lists.linux.dev, Jens Axboe , Joerg Roedel , kvm@vger.kernel.org, linaro-mm-sig@lists.linaro.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, linux-mm@kvack.org, linux-pci@vger.kernel.org, Logan Gunthorpe , Marek Szyprowski , Robin Murphy , Sumit Semwal , Vivek Kasireddy , Will Deacon Subject: Re: [PATCH v5 8/9] vfio/pci: Enable peer-to-peer DMA transactions by default Message-ID: <20251017115524.GG3901471@nvidia.com> References: Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: SA0PR12CA0012.namprd12.prod.outlook.com (2603:10b6:806:6f::17) To MN2PR12MB3613.namprd12.prod.outlook.com (2603:10b6:208:c1::17) Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MN2PR12MB3613:EE_|PH8PR12MB6938:EE_ X-MS-Office365-Filtering-Correlation-Id: 94c7a0aa-69f3-493a-297c-08de0d740f5c X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|7416014|366016|376014; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?Lk/JeJcORYBGeY9FyxwzDVo4VFIdFcb8dcteg0duQXkoW+a69ou4kyJZVzv9?= =?us-ascii?Q?7FKGl0ujRlOkGQClqet6FTmUlnOVMPCwReDyAA/PFhIk3wzOlucYw6sg5few?= =?us-ascii?Q?r3ASUeBbucsM6iCZr/3MvlSWdVV0qsiCyXAyNpnQ0m+5mEVhGzXvtlDWYmRI?= =?us-ascii?Q?kT38bne2gJ+mB2ych35ZsoC7RTFHeL/qF8vc2YfuGh25hpZMA2NrPe3TgVbQ?= =?us-ascii?Q?AevIGB1UbFpxcRAYNlhtRyqTVKHuuCfTmm3nZ7w749vy+rSnATQ5TqnN+aue?= =?us-ascii?Q?f6A2wD4/VJmxJpQgj0t0BlxWxLHThHeZNizqoPBV5m6y4iiHtf/Bxtk1Qv7A?= =?us-ascii?Q?Jy1rX1VFnCvvMMjgjxzoWKuqeKzMc8AfDAZveNZksX0VcCd9DSMfkLnHTxtC?= =?us-ascii?Q?4V93w4FBFn3EcimrRWUoQ8s+39EIj73nR0kKDP5HajO7AAF3qnrhSPlyKgQF?= =?us-ascii?Q?deAVIvF9BZETezFE5sKYEETeY1atUBxyecFtfuYMW5WxbjIbPAPUc5QCqp2y?= =?us-ascii?Q?J3U1XykK/idrjkwCeYrw++OYZ3Z1Mzrt7R1/f1L2DRC2TnuCaQjEL844RGAI?= =?us-ascii?Q?6/G/PGGcenE7aS1g5CFtSPyIttCWumVfP8fW73HdqH8WpzR4wSZmdJDF3AxP?= =?us-ascii?Q?dhIqtp9l1+7vEFo73yQQpbMZfUwtpvEYujRU/F9a058zfKdCHeQaynJcv1Ww?= =?us-ascii?Q?VTVbLN36LCseflqtEVfmqsZ6Juben+9NlJQnIzlA1hq4qcUOCf+ij9BfJgrY?= =?us-ascii?Q?jaI+SstNdmN+11hlu7peHidfF2koIDkE7MVCAsDRFqxLccFZwNdunFsjNGS+?= =?us-ascii?Q?m0zqNtEJXC91te0gmBlfWzT/9/sLBU/PKeNAwyZ8NfAC8/OJxJBr/07has6B?= =?us-ascii?Q?LJ8wikBNca8tGPhijPCDkLWIteFxlaKleExfusRfNBGGcjsDPirVCkY2MMsR?= =?us-ascii?Q?hZ+KEXUZBXfL2hwKss18s2GDe2rKMicIYVrGU2m5WxVpg+sOOdtj6LDSAnSR?= =?us-ascii?Q?oZkv/QeEUWyp13FHCmWHRsry+mkXlq/Wjpq7Duu6iRY3zxVPpSejlwIZO+HH?= =?us-ascii?Q?A7OH54VUp88kcqcRzkEHotDQZYoZ8hSRAl3wWOW/iPRJSUWR5SiBl9uiCjIZ?= =?us-ascii?Q?7hq89hJkApZFZo0M1augzImYdtDLg4Mi0H9EfN1kZ/Ar3RZcRsDpyIsMiZ99?= =?us-ascii?Q?rAhnpZdeHPHfQDwBUUgypB1nFymLnLv7XVaAzh5TQif7sWGQSq1MR7Jryqq5?= =?us-ascii?Q?l/warxM5BCqL5TiX13Op2VRre3TginqknwOEY4rTVPlMaTX9O38bNxpfbuHx?= =?us-ascii?Q?r300GK1bEUJaAs07Kl81UGVa3AlxU/Bx81Qgt+n2fBNy6+UvfjqC+qKk6MEG?= =?us-ascii?Q?++eJWV7jvnC2EAjL93s1xPvdtxO81FN/qhXplP+3BE8DiKAG6DIqEB1r0rrN?= =?us-ascii?Q?9FCpMIKxVcp8iZrLmXpH4tKHeUB1IA2u?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:MN2PR12MB3613.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(1800799024)(7416014)(366016)(376014);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?UE6AbP28Ked03KQKP0GrTGz9UMpYN96NE78+AIdpz2DYIoXcYJYxWlhZXbVH?= =?us-ascii?Q?l0mXMrriB9+IeDQ11VPByt/vTx2y0V+/2l5XzgM/b6DJLa1QFWS8jEzPQpFC?= =?us-ascii?Q?80zsEi59zXY9IUBAqss9S3eUSoVdAx37w+TzVrS+9SS3PDTsrIRSOmnWF0vi?= =?us-ascii?Q?z5I189qFlHJim7cyZUmX3bXG1y06o4I9jrhv1dgxIBJ1K2VrmYmE1f/0GReW?= =?us-ascii?Q?0NYLY6IBzpM1D1vmllW5I3owx9m/LV5n0RByWxc4PFpUvZMw4Fma5ex4DwuV?= =?us-ascii?Q?UlIouCePpa98LlTnH+Sj5uiZIQbCbEKXHbIZx8D6ZZoC7RFJpmwW0Q2RlLUQ?= =?us-ascii?Q?RezlROkpbW24mlC9OacVkXm9VYJrLK5OuBz31HP97moEKex4qf40G5+LGNbC?= =?us-ascii?Q?Vxb57ru5zQ3TiJkvHIQK70O60OQApQCZJy3c1VdVJcjB23yXfh8vTgE3Zjh1?= =?us-ascii?Q?LDOifzvALF44j0av0uJYd+6kAL9YVxrHJFubhKj4o5cyQZ+3XuhCR1sPiOgi?= =?us-ascii?Q?M7sYyXj4q/YsjJShFTz0545kH4zHDy5uIJ5lUFGH+8OqJRMZbIIIwTQldg4m?= =?us-ascii?Q?0tKl15ZBfE4aHyG2IuDD9xTGi0n+ZVaUWb2tTVIYUJtI/M091VTPiOT2XgqL?= =?us-ascii?Q?5q60G0UC25NtC4nSZOQy0i/+v4Tk4OTFflpUz3UUmg/a23iBL1sR6kw2SOZi?= =?us-ascii?Q?EgMayEfca4stjBHumrPYY37BAq2RWPpe1K3cJ72eKDWAIO/hjnT9UPvU1y79?= =?us-ascii?Q?jZwqKHIpx0k2RqCr4A7gBwK4vlstJ6sKasgTKBDLZldkBBkuHNRDfvQ0nMgH?= =?us-ascii?Q?KtfGIVf9zgRjJ5zDLOLB3QYhaCCHMiBq8gC0RoiqxOU9SnFf+mmutgJt6esQ?= =?us-ascii?Q?t2T6MRlZpsBvIaeYCCEpUI7PKGLiKLweY7JiAfUJ1DisFpjGQwp7P07LblQK?= =?us-ascii?Q?ChEjtmRVPsmexo3H0By/ObbFN57UePH66OOmV0rIxm20fERMqRkoRMIexr7/?= =?us-ascii?Q?F5rkw2QvBi6pdGY4ijfCqIkV1ZvJRoCW4iuKuZkCMZmALbkfdrM0n2HWveDU?= =?us-ascii?Q?K8zWRCpUuRZ6NNhuupyhE19kHEMOV2yKmXjtF7HfBIZN8a7M3VnqkKNllfGZ?= =?us-ascii?Q?kWcbWQd7T23EAjZpqcLgBkOgmxfddBtNon2dpKJloGYqsDxyabstbsbb0Ks0?= =?us-ascii?Q?8K8hWNtQPG3i91xVQOt+N6P8et/QL5dHmf6EuXAuEZupZ0eHhzgfLswUXkYx?= =?us-ascii?Q?V36J81ZkFI/TMdpDUI1mKHUHezipV29MTK0DlT/T6Ei0gWqytpSfE2ni8G2t?= =?us-ascii?Q?qX/TCtMR8Wm8gXQYlGQ3XkrT2zbCBAfM6r5a/FNKVcpP2NGY7KRr444Jvlp/?= =?us-ascii?Q?IRE14GY0ThFujKoQHu+UiMVpO4wSMrVAp81G70t4ahHHmL+IfvjUmyzJSYAs?= =?us-ascii?Q?iKTXNGWJxtheJMcdU2f1oYz+vgtFPt6DqJ8MkTIWeTuKlklwbNsybxGK1nQo?= =?us-ascii?Q?2YL5/miJGainpMLYVRPRpTIU/iXRJWbTA22BwuEbcjhXW0GArYnri6KVsIYT?= =?us-ascii?Q?cxIIXLdJuIK+BWefpty4xFXoz+gpjDwZ6V5+VBGH?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 94c7a0aa-69f3-493a-297c-08de0d740f5c X-MS-Exchange-CrossTenant-AuthSource: MN2PR12MB3613.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 17 Oct 2025 11:55:26.1596 (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: pOy9aCAjjLmz7OdYPH4lLeue18rXKogU4vpHUvLkh0XxBRw9bcWpmJw+enYz+cAB X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH8PR12MB6938 On Thu, Oct 16, 2025 at 11:32:59PM -0700, Christoph Hellwig wrote: > On Mon, Oct 13, 2025 at 06:26:10PM +0300, Leon Romanovsky wrote: > > From: Leon Romanovsky > > > > Make sure that all VFIO PCI devices have peer-to-peer capabilities > > enables, so we would be able to export their MMIO memory through DMABUF, > > How do you know that they are safe to use with P2P? All PCI devices are "safe" for P2P by spec. I've never heard of a non-complaint device causing problems in this area. The issue is always SOC support inside the CPU and that is delt with inside the P2P subsystem logic. If we ever see a problem it would be delt with by quirking the broken device through pci-quirks and having the p2p subsystem refuse any p2p with that device. Jason