From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from CH5PR02CU005.outbound.protection.outlook.com (mail-northcentralusazon11012038.outbound.protection.outlook.com [40.107.200.38]) (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 E92BA22DFA5; Fri, 20 Feb 2026 18:49:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=40.107.200.38 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771613379; cv=fail; b=QQLcgfKFcVr+DqDmW6D6YrLnMf0qSvdP0Mhr6i/VOXEBng3Cjg1B6doVf6wfP9V6Uz/SxyheVCv33rAP4c47PxthgR5+c97ACcpqkTAHgtBtADQI1DPmhRSNzlI5U1Dij3PKfB8IkdTkkNdv8FIuY7wAG9iY+Zd/i0PDdhPBAqw= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771613379; c=relaxed/simple; bh=VwaNWUkO2EmPwxsPrhzb8k9d1XccC0xvTxh9CwT9KKE=; h=Date:From:To:CC:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=FV1yD62bdFOFV3h2XQFlYrkMuGl4caJfCg0gjlg1MLo+VpZ9FiwxjYM1/BgsWy/Me1AGbJzZGwkyM3YA42OwXp/BDTyKbFjQhMGj4EkOyxjU7qh7kpK1N3OPFN/49Gw0KGbwAdqBJkI6hdnL0PV1hRg6sBCxaVgkFp0eYNnuGTk= 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=Tj5Ka/kh; arc=fail smtp.client-ip=40.107.200.38 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="Tj5Ka/kh" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=E4WeE4c8czsh+RrzQ0HqRZjaiUolsWX9hktR6uFM+xhwkVBFXyUcKDC6TxZE+H3l5iNdXowIl2HeagYmcPIcO/kGJcA26SPGG0/Afv60eIylCXH8//JE2B7j7QamnzHVmAdI6N8TBFzxkp2yh46Nhv+u9Xv6uHdSq3/8MLul2zeW4i9cD246JYwCcJN3U2STp3MlpLGby+c5HdX2j3A59mBP8XHK09R1HKqHaZ7BAGqq8EpI6Ti1WIMVT9uFBJgzTf4nJvS+M6EnEVVz6PMjrxvkqQHKL65g3/VbSwZacHpacyNA26b0gIV/pboGY+RzeMHo90nHvVRZ6/wp6ArICQ== 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=4PsBxUqvCGuYsoU3vfsMLDsvc5Udr3Xx3REiZHFm8wo=; b=aJUWZ3GjBBJtk/yodJbU6fw52rx5oxbNg5O3EPRVM9RZK3PIPfDX98e1Mnsr/EUM/BVIDWc7w1Za9u21PPMLpVSTblFW2iiBXYl5zLxXSEy9OxvoU6KSSOqr+dbN/uvfH/mLIdiFmsqsMt0eW1ScsyQLFKPE67k/MWYt+f3WNlE393QJAaWp4cz1+YRbs0e/pddUjTjdmEj+hVp0pajzxVPwyIuNHsDjJObj5O3lzIEop7+f+N+0QRKcIsRyU3nOYy9+3Qsq+0PHc4t/3aIhfXeBxuefQQj74LMx8aBPyozjkzRV8Q7AxPEHeFsLUZsZ/EhuHU5VxmS5nUXaXHstLQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass (sender ip is 216.228.117.160) smtp.rcpttodomain=intel.com smtp.mailfrom=nvidia.com; dmarc=pass (p=reject sp=reject pct=100) action=none header.from=nvidia.com; dkim=none (message not signed); arc=none (0) 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=4PsBxUqvCGuYsoU3vfsMLDsvc5Udr3Xx3REiZHFm8wo=; b=Tj5Ka/kh0mkFPR7XAamRlPmfXiAgJ2z2p4SjzAJtjznlwy/UgV9hZ17xx9FVrGUy4XchNkhpcIlAxc+CWnMzcGBD0bi2E5AcSQRBYHYWvSJOveVeTxfsVIY8cM9kk3gQz5OuYZhYOOrTnlv/GULsuo819zAiQ+Xudyx9dl37xkiFCO7g5rJGUo6kcZurRq72LjuDQBDZ8zPvKfVU0uQmmeCMHs2yG3ogcvND7AdSW7SFdTK6BXRh6MYofzHXc3H25R0fV5oRbQUe3dWgOsE/lk1R+feDZp1gZICuWkeVk641Y3ty+ltFnyLpPpMRVLf8mKErM1gnEVNlCqoFOzn1YQ== Received: from PH8PR15CA0012.namprd15.prod.outlook.com (2603:10b6:510:2d2::18) by CY8PR12MB7706.namprd12.prod.outlook.com (2603:10b6:930:85::18) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9632.15; Fri, 20 Feb 2026 18:49:33 +0000 Received: from CY4PEPF0000EDD2.namprd03.prod.outlook.com (2603:10b6:510:2d2:cafe::32) by PH8PR15CA0012.outlook.office365.com (2603:10b6:510:2d2::18) with Microsoft SMTP Server (version=TLS1_3, cipher=TLS_AES_256_GCM_SHA384) id 15.20.9632.17 via Frontend Transport; Fri, 20 Feb 2026 18:49:29 +0000 X-MS-Exchange-Authentication-Results: spf=pass (sender IP is 216.228.117.160) smtp.mailfrom=nvidia.com; dkim=none (message not signed) header.d=none;dmarc=pass action=none header.from=nvidia.com; Received-SPF: Pass (protection.outlook.com: domain of nvidia.com designates 216.228.117.160 as permitted sender) receiver=protection.outlook.com; client-ip=216.228.117.160; helo=mail.nvidia.com; pr=C Received: from mail.nvidia.com (216.228.117.160) by CY4PEPF0000EDD2.mail.protection.outlook.com (10.167.241.198) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9632.12 via Frontend Transport; Fri, 20 Feb 2026 18:49:33 +0000 Received: from rnnvmail202.nvidia.com (10.129.68.7) by mail.nvidia.com (10.129.200.66) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.20; Fri, 20 Feb 2026 10:49:14 -0800 Received: from rnnvmail205.nvidia.com (10.129.68.10) by rnnvmail202.nvidia.com (10.129.68.7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.20; Fri, 20 Feb 2026 10:49:14 -0800 Received: from nvidia.com (10.127.8.13) by mail.nvidia.com (10.129.68.10) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.20 via Frontend Transport; Fri, 20 Feb 2026 10:49:11 -0800 Date: Fri, 20 Feb 2026 10:49:09 -0800 From: Nicolin Chen To: Jason Gunthorpe CC: , "Tian, Kevin" , "Jonathan Cameron" , "will@kernel.org" , "robin.murphy@arm.com" , "bhelgaas@google.com" , "joro@8bytes.org" , "praan@google.com" , "baolu.lu@linux.intel.com" , "miko.lenczewski@arm.com" , "linux-arm-kernel@lists.infradead.org" , "iommu@lists.linux.dev" , "linux-kernel@vger.kernel.org" , "linux-pci@vger.kernel.org" , "linux-cxl@vger.kernel.org" Subject: Re: [PATCH RFCv1 1/3] PCI: Allow ATS to be always on for CXL.cache capable devices Message-ID: References: <20260203143348.GA3931454@nvidia.com> <20260203175540.GC3931454@nvidia.com> <20260219143737.GG723117@nvidia.com> <20260219174139.GI723117@nvidia.com> <20260220125044.GK723117@nvidia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260220125044.GK723117@nvidia.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CY4PEPF0000EDD2:EE_|CY8PR12MB7706:EE_ X-MS-Office365-Filtering-Correlation-Id: 247a4844-3ab7-4fad-ea0d-08de70b0c996 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|36860700013|82310400026|376014|7416014; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?S664xDXtqi5MuuSVUTHkDloMbBcOy55t/4frUgyYqrbJO2H2jAugiZZwq/7g?= =?us-ascii?Q?xskBG+qjhFNyJIEDLEfwu2lRE4ZXUTq27EYJ/30bADEiOKIjsuXetJPMpheM?= =?us-ascii?Q?HmzZo/NeCKIocB6tfDNH+Z/CQ+C4mKa2jvMHXIaorIbKStq9gW+0lUgh2/kT?= =?us-ascii?Q?5irO1OSH54qY4+MALEDmEZAEUpvZgFQE65JVunKQ401MQw2hoAE5kXwXxKVq?= =?us-ascii?Q?4ZKPWOUjt/Cm5KcB3jW7U8X7JRXdmnwaibIu+i3gjy1H8l2z2W5Go6G4HqWb?= =?us-ascii?Q?Cu5z7OlfvWxC2hHcqNl1Z83e1ehBcV56vtv6DwBmNoSHZDDPZ28IDRz+aVmB?= =?us-ascii?Q?11MxHHNzklJpD74tRTR6pEqnUluqfHirn2X6SNnGZ13g7mJU87Q7Q6S4IwZw?= =?us-ascii?Q?y7NbKz1dd6snXKCYRLu2PSOEbPCf3nsaZAfUuQ6prgORa0r0AprgE1VGFg5j?= =?us-ascii?Q?yY7ADmddkPN/UdCS4z7BrMaLC3JGc+cpXjH89F3ZXE7OTdWla5ojBGHlSVdQ?= =?us-ascii?Q?7EPj+hhbilnSQzz6QJGHohCnG1CV+XRJB4pFH6ZJiO05mWdlRBvD/mQzEwVl?= =?us-ascii?Q?f4FnjcHO+2/RVyMToUnJ+oUQ01bzfaWsZIwBjW4fxgg2IiIM4eEihAwvuFVr?= =?us-ascii?Q?mNSeCXDREwwFnJK7uG6/+5VN/vjInq8LiDeGPyXrXonW7nR+mZ+ie6jdmP1z?= =?us-ascii?Q?8kEO8Vi7EwGDvnN7hoHntIFSUQ9DPe5yZJ+EQC/it2Bd+qWcQ6SiHz51BoD1?= =?us-ascii?Q?9eY3GrAbVDCeYHVN00sR6Wok8CBnM1k4cWXCB0+iQdhicbMo4elczkaZyxI5?= =?us-ascii?Q?DCFxK5+PphtvFDpfWySnSRgWqIaPz/doa0VyIn+PZZsZteHyXxCD6kErmbZ+?= =?us-ascii?Q?ubysvlSzAD1YKJ7KETlicNy7IEkKtX6EvnteJTf4p38oCOWlXl9cWSIPCEPP?= =?us-ascii?Q?KehlsuFfrOXlKCKldsA5352SQbb8qPPu04uACuj64bfdUkbo+Zl588Tk/KoW?= =?us-ascii?Q?N53JwomM+dzlK6/IhVlkDtX16A8vPACZxV6Cry/TO8NXu9hifS6l2KlvV+N3?= =?us-ascii?Q?++/8KexNbD6wTRrd5JnkA1joVKKeXiwlb7U67jTTmWuYr6K8ye0x0jxpAoqk?= =?us-ascii?Q?pZRGt6jJ/Vrpqoftnuv7+ZJGoOGRrH8aCxkOAqYdb762MlCBJjhKEzWVH3B4?= =?us-ascii?Q?ngQ6n1LVcXt9Ms3rO6hnM6VlBX5jjSaUTBqq9Fr+MSN5ZPBdQCmv0wD0o2/N?= =?us-ascii?Q?aN03JwRRlRdEnPcpxEsen/NTpP/Jj+9aojSwm1TAN6UmI1++mNPWJ/X3c3Xh?= =?us-ascii?Q?ClU+P5veLADN5jcdU440nNfsjA2y2yz3jBW59rO7mj3Lu+0AFyHJvYfvyD5h?= =?us-ascii?Q?HyTxwXwMMlbaoh8HxesLr6nkxieWIwpwgpAWZqdKwW0UrrB5H8ySVydwChWn?= =?us-ascii?Q?ACGAbohJlypExsejrsle3MLLdVajv3VHKTWQjOSJgkW+wfdMgq+GAey47ytN?= =?us-ascii?Q?sb/EWaeswufbMuutPGaY5+nXRHgZUCNsbWhjJ9uJp1F5Y+H6i/LGRsW+GFFK?= =?us-ascii?Q?7tVfFmFSnQ6U+OrT+DQElS1KK9P5dCk0wJWJJx1HgD4JzYmy8Ajp6XbRn7JY?= =?us-ascii?Q?Aqk52vmlzeSQrfYYJknC21csvIctynYCu/RCLGMhRkKDyjBVKZmvjOltnWoI?= =?us-ascii?Q?Ke918A=3D=3D?= X-Forefront-Antispam-Report: CIP:216.228.117.160;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge1.nvidia.com;CAT:NONE;SFS:(13230040)(1800799024)(36860700013)(82310400026)(376014)(7416014);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: 5eBJLSaFc78f2QT9QENVIDMy6MQtmiAjyA74+ONRyOHUMmDRHBO+sfvprliV5/Mv1s7Q8kkU/wm/PJMqYuS2DaLgU0nmdLQD/yw1lsapzJm9z9V16Zm/X+/5tj6y4vuR6xRVMGRU/Hn3Ui2smLVev7t/BgwniHSWDUJhnnU6XPhuKw1LuvFuXgaqhT6IN3wPP/QPCCE0FRCjlYXCP/87XrY5amAGcl8UxluqifKyH4QOmu96ZfcYXQ7h1NWtK/myJAj0ij6DdIGgph8To8/yjDsKwITMpH82zC5xzcyH4HhPJpb2RNNMsQtbZEwHQu9YlKvBka9sNbzTfib+VJ4M/ZjITJ5QnFFv54Yawpsv4KqiUcwOzND/7yQQVNqR1zPchJ+Fo/qqSDBYZ8LqqJlCJ5RittkTU9NGifeqc/sYA7rwqdOgbtx77BKyXUC27PeB X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 20 Feb 2026 18:49:33.0412 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 247a4844-3ab7-4fad-ea0d-08de70b0c996 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.160];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CY4PEPF0000EDD2.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY8PR12MB7706 On Fri, Feb 20, 2026 at 08:50:44AM -0400, Jason Gunthorpe wrote: > On Thu, Feb 19, 2026 at 08:52:56PM -0800, Nicolin Chen wrote: > The next suggestion is to park the device in a real DMA domain with an > actual page table and DMA API hooked up. Now interrupts will work and > the domain is empty so there is no translation. The issue here is the > domain doesn't block ATS. We could fix this with some "disable ATS" > domain flag. > > In either case when the driver is bound and requests that the DMA API > start working if the user requested IDENTITY then it has to be > switched away from the parked domain to IDENTITY. Thanks for elaborating. This seems very orthogonal to the issue that driver_managed_dma skips iommu_device_use_default_domain(). (And I see you discussion with Robin.) Regarding the empty-DMA domain, I have an idea of accommodating ARM cases with an IOMMU_DOMAIN_MSI_ONLY, which is essentially a paging domain that only allows IOMMU_COOKIE_DMA_MSI but blocks everything else. > A final thought would be to change around the driver managed DMA > mechanism a bit to allow drivers to indicate they use IRQs but not > DMA, then the bind step could switch from a BLOCKED domain to an empty > DMA API domain to allow MSI to work. Yes, "driver_managed_dma" is so unclear in pcieport case, since its driver doesn't really manage DMA... A separate flag could be clear. And the IOMMU layer might do an AND operation between driver_uses_msi(?) flag and another IOMMU device-level flag msi_behind_iommu? Thank you Nicolin