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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8192AE9A048 for ; Thu, 19 Feb 2026 16:54:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:CC:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=4sL/2bwrtqZhmTX5mVWbCuOi8d8ue4yHY1JqsKLKDpI=; b=IynJcoXrpOA+eL6RnAgrFs75ZX M05u7Ya7/c7rTAFHp68XLgIR/TlW4X6BMGQ6rPOYq550a3M3fpDoVaatUWDyEBB/WFpuWRNGcXUAM PUomi3Hc/0GlxsP682Plj98qMlXjS2oilQ4IddvIEvDLJdhwCM2tFroQSr2iSMgpNZaNkTPKrmrDa X4DS5nmW9+k8gaUEI8ma/wpmWyEA+pSbG50EGVejOVYTUwdiVoLvuDvJtVd90ddqtuo9ewe5FmVhS Mfr8KrQfPENCE1KCR+poo2PSvxGqUu2QWKyXlHglCvSfea7Ivy4wRDRYV4ZUE25KKWRh6LHKBlp0r j/gQ5qOA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vt7Hq-0000000Bep2-100s; Thu, 19 Feb 2026 16:53:58 +0000 Received: from mail-westusazlp170120002.outbound.protection.outlook.com ([2a01:111:f403:c001::2] helo=SJ2PR03CU001.outbound.protection.outlook.com) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vt7Hn-0000000Beoa-2SF2 for linux-arm-kernel@lists.infradead.org; Thu, 19 Feb 2026 16:53:56 +0000 ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=U4hcm9eal8mBttY8z62SPYwcYVDT2Psb47feC1QD2pL8Bul0lD/sfeId8PE6+nP6OUGNSDsk/GQW5uKoVdHdc/tn24RHYvpCBpiZGG3MIzFOrqwrGU3M6NQC4LacMQgdrquwk2yr22/oqSnO4nJvvt9b8DGPzJVmovF/Ss7OlE1Nvvw1u71iffa2dt6gSbWLGfyRg18fRXogr6i55kx2yodvQo6MKBGH2B+DO1/D1Mz+Or8S0p+h9rQDdX51Gr7+swAuq6128jvQeWsOs+ShloQu0eKUm2kdmOa18ZqRjFCZ5xo2VAmymoC45N/5zBhXfOLunTFKv2J4L6P16MKBVg== 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=4sL/2bwrtqZhmTX5mVWbCuOi8d8ue4yHY1JqsKLKDpI=; b=kGwqSq92VwlVw4HbhcZTRaDFPhbKDZQWv4AOXJopjJc8VupuhLGOGNZPORbAATWNBDrxkCDbJKIUheIMV7ryKiMZyvGlbTMzVnDIEOdBvjbhrFrRCihhyEiG6o9S6gX7FeYXoo0x2omvYSPOULFrqZE30H3zrXFX3tyROUepjdVZZ829izyxtkj4kzJ9yxS3hdQNob/YIIzT2b/UP6LEAKVwzlM6MOgp1VWO0rzV/TGYI2AC3OThycotohgFMwIdxGXM2wIv4fDJpzejU4fnfXGIbdCs0XsqqO7ozPkPcun35UW/VBM7oj1rHqqr9uGL6gclv6FBs4sQ/BexwsuNFw== 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=4sL/2bwrtqZhmTX5mVWbCuOi8d8ue4yHY1JqsKLKDpI=; b=S0RhDY5j4FD+DZ1PnfJ2r2mVF/yx6QsNwQNHV8KO6S4b+HSEJ3vrp7M6o+TZAelqddEmnqzuRzyC/p+e/eiNsBN8KC4eUke61D9fC4TBmWCnA+fb38zQWDD3Oe2CODfqTKLtPuyyWbGsiLEINa18jdN6DjnM6h6K8dX+GNkTUsqSEmF4wkiV/c32dmeLNoCEHv8xukF1zf87w9NRDieEtcc/OQLBbVQVxYTSI6cXULMQewX2lm+Zu1Njnm6t35iSa5CVGdTTSaZnm6TxhQx1+BvUNSK4IWWdfkZzKwhgsbsvp6TVAvQ+eLg+iTbn4TNEawf1r+Su1I7GGIJ4yINyxA== Received: from CH2PR02CA0019.namprd02.prod.outlook.com (2603:10b6:610:4e::29) by MN0PR12MB5929.namprd12.prod.outlook.com (2603:10b6:208:37c::20) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9632.16; Thu, 19 Feb 2026 16:53:42 +0000 Received: from CH2PEPF0000009E.namprd02.prod.outlook.com (2603:10b6:610:4e:cafe::e) by CH2PR02CA0019.outlook.office365.com (2603:10b6:610:4e::29) with Microsoft SMTP Server (version=TLS1_3, cipher=TLS_AES_256_GCM_SHA384) id 15.20.9632.16 via Frontend Transport; Thu, 19 Feb 2026 16:53:41 +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 CH2PEPF0000009E.mail.protection.outlook.com (10.167.244.27) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9632.12 via Frontend Transport; Thu, 19 Feb 2026 16:53:41 +0000 Received: from rnnvmail203.nvidia.com (10.129.68.9) 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; Thu, 19 Feb 2026 08:53:23 -0800 Received: from rnnvmail202.nvidia.com (10.129.68.7) by rnnvmail203.nvidia.com (10.129.68.9) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.20; Thu, 19 Feb 2026 08:53:22 -0800 Received: from nvidia.com (10.127.8.14) by mail.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 via Frontend Transport; Thu, 19 Feb 2026 08:53:20 -0800 Date: Thu, 19 Feb 2026 08:53:19 -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: <20260127150440.GF1134360@nvidia.com> <69795d0366a9_1d33100d3@dwillia2-mobl4.notmuch> <20260128130520.GV1134360@nvidia.com> <20260203143348.GA3931454@nvidia.com> <20260203175540.GC3931454@nvidia.com> <20260219143737.GG723117@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260219143737.GG723117@nvidia.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH2PEPF0000009E:EE_|MN0PR12MB5929:EE_ X-MS-Office365-Filtering-Correlation-Id: a51f4d2f-276b-4bfc-cf89-08de6fd76fdb X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|82310400026|36860700013|376014|7416014; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?VVMPT6bxUBTviGJLZujJAiBt8eW8flFVjlPIXAyRUXIHNlUJNTUiq7ozIqC2?= =?us-ascii?Q?GhmZ0hE/gGuWqztnmL19xRRpcTIFyIPNctCJ9OLzmN2XKR13p8vb4qq/MeZH?= =?us-ascii?Q?nAI3qbd9lVfUl/aIePfVcFae9c5fSPTTic2c9BNF2DoI16KrVpoem7zeebp5?= =?us-ascii?Q?u3tImBUrifpLAy4bOxzlm5/kpCgoQ1HR2sa/wbz0iwSyiu45IvxgvvOzpLc6?= =?us-ascii?Q?EnuQv7RMs1XIXx7bx54s6F5HCyaWkPDxaJzTVDz0Ge3PX/Kqs7md6Q+EX1oV?= =?us-ascii?Q?GIGlVlJaQIi86mbD821JmQywCl6Xz2LvIiCXOQigCWds4PFqK2GyKKMRx2+C?= =?us-ascii?Q?4ZemQYPyZC6ERD5DQ68HgAk/qIeH9NxnaSGFCqcEipoP2Y3ryJ8ZWtyVhSx2?= =?us-ascii?Q?X4x0vZM5shpylXS2DwdyUW2Q6zl9UFaoh0nxEFWxjA8GNufY6wgpurZ3caO9?= =?us-ascii?Q?p/K0o1DH6Pv4O5Pny+RHz0Pv/IX6h+iTQXaT1w6IvPyhlo2rs+/YMT8V5YFk?= =?us-ascii?Q?EgFXgCT0LuuCrUGpEOHZe2Spvc1oEbAJZ0rhHiLcaXPxsOR9VbbqmubFvcmq?= =?us-ascii?Q?LTzkBJz7W4bQV/u3ZNazWev57QiuduGWb4TQ421374ZP0nSnsGugHdAKOCgZ?= =?us-ascii?Q?Gj1HbWpmZtcUTgsmacqr9bJUhNqwMDsH9HfLmAQVN4N+7Q6Xh/o7xW22xBJL?= =?us-ascii?Q?yZPzWpGBe32CPwXOri4iZGVaHCGBR77+wfaPczBGItzfQsGh27z/L42/Arwm?= =?us-ascii?Q?zvsckURQSAtkNEmgWC5tmTDt52AquZI1V0NX0UPlHQD+3FXjUDd7p4qr4DkV?= =?us-ascii?Q?80e39b6DorlrVAxQAoBlgb/ljJlFnL0JSrKPDyrQER58X177PyRTrEEOePoi?= =?us-ascii?Q?a+asGqZHDMNa5cLMYGF4jT2jC1sQyivasUJlVwI1fkt3v/AIwtu6+WIfvxfF?= =?us-ascii?Q?1YaLFlwg4ThrsPOvtXNcECr/u5sg900XGpNjiOf8d+BmyawEqi4nisXVfVxZ?= =?us-ascii?Q?lnsfgxo23GXFvpIXTNmZ3DbMjXUM/aAm8lBXBDwYgocQ+2Ck2z1tV/h/eTJA?= =?us-ascii?Q?nGQBAu96pnQNfvPEiwYrKiKLts1LgyWaif87yvGW8zCTPpXoY88KtqUNY3kh?= =?us-ascii?Q?BVFIYytR/7Gc/PfqNDwfnJqUC4o3TtwHB2RkALpjmjeVp15vnHV9TJPimsUb?= =?us-ascii?Q?mBDbaAYRTh4cLWCFNmDzMbjYaghrSeJqIbuHCQZtbEnEuXk6mnag7IDibt3Y?= =?us-ascii?Q?srqLLfbMtRKQKeU81en+wxW0O1On0xhNf5ELkEPEFEqvjDHDe0bPMRdd4KOa?= =?us-ascii?Q?waUKUYDZVkjgzz3nIjlqmwcOTojN4H1t7kdb0DMeB8tDN7cH2FzysYWcKe4X?= =?us-ascii?Q?aJ55CKZe00Gu+ewCakYeLSp5wFR+mAE9qzL39yBE78f3kIMia3E4efcxe93+?= =?us-ascii?Q?igbXMtXFtY70QyfV9N2LYAvJ1sV6mq5iVAqnMCIRTk0QJNhUGXqFR2phStRB?= =?us-ascii?Q?krSlVa9wxprrxub1sxSqE+jwNNYjcCb235xYmSAsxkauXz8Vb12PNB6AG4pN?= =?us-ascii?Q?YGX3mDngp1hf7SABNw3qkRhABi0Swvlc4sRJgNIj8jSLsNRFymYTo53NFOc1?= =?us-ascii?Q?M+T9LMIQYhRM8OgMalhZ5R73G+4VK2vVc4QAIST7MvMPaZjnz4fyPgSlAbZc?= =?us-ascii?Q?H+zKdA=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)(82310400026)(36860700013)(376014)(7416014);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: 3Y3K7sDVYneADcS+mwzWcdAWomna8O6cKrmK2PWKY4aoJzhQX7M5RXBN8mKW9gY1T8rSRbWAfxm0J8GAibVMNVHQErqE28paDTo3xctkxniNsgEZw714ITRynTcINgdWJKWHNgr4iRqnSJHqLEnvpXXZ8g9Wr5UjBECkTzqRPReyKq6XyZ54ji6C4QzHB7imtw9sqEG9RPmjPEo5QgRE/6V7C1VmxoDSQzOHtWIiJJB3YdPVhbjLUHqLirDAXIGfvHnyEv+D6eiRVaXv+DkDQfBdSRzljrbCs2pJutJAN2OPMyphuEmtUAh1DUoi2uCvt0GyPdy4W9E0Vu+Me5Ciwvwl70HhMTSvRADch9szaNxjoruW7EYcA0OJ0tmjJWXKOL/b+LBBnlJGMji7xdNKnUjGD6+o0d6Mxxo3rDoOMzD5fy7RNQMEqg+i9B5iTyRl X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 Feb 2026 16:53:41.6944 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: a51f4d2f-276b-4bfc-cf89-08de6fd76fdb 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: CH2PEPF0000009E.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN0PR12MB5929 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260219_085355_630294_C110836A X-CRM114-Status: GOOD ( 28.45 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Feb 19, 2026 at 10:37:37AM -0400, Jason Gunthorpe wrote: > On Wed, Feb 18, 2026 at 02:56:35PM -0800, Nicolin Chen wrote: > > On Tue, Feb 03, 2026 at 01:55:40PM -0400, Jason Gunthorpe wrote: > > > On Tue, Feb 03, 2026 at 09:45:17AM -0800, Nicolin Chen wrote: > > > > Btw, attaching to IOMMU_DOMAIN_BLOCKED/group->blocking_domain is not > > > > allowed in general if require_direct=true. I assume this case can be > > > > an exception since there's no point in allowing a device that has no > > > > driver yet to access any reserved region? > > > > > > If require_direct is set then we have to disable this mechanism.. > > > > I found a corner case, which might be another exception here? > > I don't think this blocking security work needs to be part of this > series. We just need to disable the mechanism for untrusted devices. Oh, I thought it should be a prerequisite. I'll separate the patch then. > > Most of dma_configure callback functions don't use default domain > > when driver_managed_dma is set. And this breaks MSI on pcieports. > > The ARM MSI aperture need is some special case here. Those drivers > don't use DMA at all so of course they don't have the DMA API setup, > but they do use the MSI aperture on ARM. > > Broadly here we were talking about blocked domains for unattached > drivers, but an empty DMA domain is the same thing and still continues > to allow the MSI vectors to work. I see. > So we can reframe this a little bit into more like > > if the user requests IDENTITY then the IDENTITY domain is not > installed until just before the driver binds. Up until then it is in > the DMA domain. Meaning if userspace controls driver binding then > unbound drivers have their DMA access blocked by an empty DMA domain. The thing is that those driver_managed_dma callbacks don't call iommu_device_use_default_domain(). So, the iommu core loses the trigger to switch domain from BLOCKED/empty-DMA to DMA/IDENTITY. The pcieports case via pci_dma_configure() is an example. My previous approach using BUS_NOTIFY could likely work, but it needed to adjust the timing between BUS_NOTIFY and dev->driver setting. Thanks Nicolin