From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from NAM12-BN8-obe.outbound.protection.outlook.com (mail-bn8nam12on2042.outbound.protection.outlook.com [40.107.237.42]) (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 BC04C28E8 for ; Wed, 19 Oct 2022 11:53:24 +0000 (UTC) ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=WoT6ZMYXf3ZRgE/dc4i5oQ+tZUE7v5EU0XcrPPRhUD2CihthYDnBSRfwdHKeYQTDG/9IuIU7scKqgIR+s7Jz7slyLP39M02+zbxgQYCx8Wg8FFZCXHRfoOruQcIfZHIJ6/71aLwXmw8EPSMJY6MZGJF9cabjMtTYlDm5UYg5PLleTc05xgJmdKba5F396sBTy9I8SQ7s4XZ5Q3IzWAp1o2e48C4MoQzbnzR8XVo0z/IEnMD0G6H3wzFM/Fe3S/OGJXaOBToOqgR9dHGjrpdqmrp3Sg6oMI4G4zT63B8f2YAWT4M/o8yzaLOXGy35ryl+wzlVFr17Am1h6SS7Zvbncg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; 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=SAIkjoKxC3pIOdcBlF9pfDE6MXcc9DZZ7LqpjGGjYnE=; b=FIwOdfUGTmdzvz6Y43C71vPBM96tN5aeeUCfyV+Kng4W+y3KY3SRIoEURDk3gBYDT8Z0fF3nH2sRj6kvHwrHHw2dMzqV/pG2kfQb6rTJuHPKJ96i2pJwbmZVcuQCwd10HPZ9d8HxRf652DCG1DcJm4RgcgUgMB/4EJmjvtMBunkjCOSNRAU7S2s3Ryw2vV4/YSTEKfCLv1wyc2udHD3zG0nrXoRk9LYq00iPEg4SHrdxqSjfD1h4P22+mMzVc1iSp5j085x3AZ1Y7SVU1h+LxOphL0LZEdapdER7jCmjYTK6fucvZBQiUcOXk6nByjnPtQEQqEQ1mb5m2ZsX1I5QrA== 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=SAIkjoKxC3pIOdcBlF9pfDE6MXcc9DZZ7LqpjGGjYnE=; b=P8CWsR5jIRgwpKAduJWiA7bxZhnQfAbxDH0rhC7kXnRnvZG1ELImYPnhyT248aTdb2rlr5nGOnteYPD9ax0gKUhtWci+B3m0/9AMs3KDiK3uYZjRUdV30DUvgGt3aGuB8YsahCO6JeM7kfDWKEKa74wTKQZrTgkTO89o0NXHBxtVsiyTC+bDYvMFOSq/JZU0vb8O179nKAM7sz1fsvkYc7Zcgbunh6V3HeizT2C+9QPstR3aw5m1558xhBEeEb3Xgywskbxqow2Y1N4TyAulyjlQze9YF6K9TT1koguf6nlZtOgWQ4l3zJg34K27j//XotcDq2F0e/AZLN8TSOPi5A== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from LV2PR12MB5869.namprd12.prod.outlook.com (2603:10b6:408:176::16) by PH7PR12MB7307.namprd12.prod.outlook.com (2603:10b6:510:20b::9) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5723.29; Wed, 19 Oct 2022 11:53:22 +0000 Received: from LV2PR12MB5869.namprd12.prod.outlook.com ([fe80::7a81:a4e4:bb9c:d1de]) by LV2PR12MB5869.namprd12.prod.outlook.com ([fe80::7a81:a4e4:bb9c:d1de%6]) with mapi id 15.20.5723.033; Wed, 19 Oct 2022 11:53:22 +0000 Date: Wed, 19 Oct 2022 08:53:20 -0300 From: Jason Gunthorpe To: Niklas Schnelle Cc: Matthew Rosato , iommu@lists.linux.dev, Joerg Roedel , Will Deacon , Robin Murphy , Gerd Bayer , Pierre Morel , linux-s390@vger.kernel.org, borntraeger@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, gerald.schaefer@linux.ibm.com, agordeev@linux.ibm.com, svens@linux.ibm.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/5] iommu/s390: Use RCU to allow concurrent domain_list iteration Message-ID: References: <20221018145132.998866-1-schnelle@linux.ibm.com> <20221018145132.998866-4-schnelle@linux.ibm.com> <8e268ab5e0dadf86be5fd7ffaa9debb76cea67f3.camel@linux.ibm.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8e268ab5e0dadf86be5fd7ffaa9debb76cea67f3.camel@linux.ibm.com> X-ClientProxiedBy: BL1PR13CA0433.namprd13.prod.outlook.com (2603:10b6:208:2c3::18) To LV2PR12MB5869.namprd12.prod.outlook.com (2603:10b6:408:176::16) Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LV2PR12MB5869:EE_|PH7PR12MB7307:EE_ X-MS-Office365-Filtering-Correlation-Id: 4077c7ec-a773-41d1-cacd-08dab1c8857e X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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:LV2PR12MB5869.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230022)(4636009)(366004)(39860400002)(346002)(396003)(136003)(376002)(451199015)(38100700002)(86362001)(41300700001)(6506007)(316002)(6512007)(6916009)(26005)(54906003)(5660300002)(8936002)(4326008)(6486002)(478600001)(7416002)(36756003)(66946007)(66476007)(8676002)(83380400001)(66556008)(4001150100001)(186003)(2906002)(2616005);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?ZgqiUD5hM+Axckl6sQ2yBizFLCEzXXNEVcMjgaTyYCn7zICWNsBppoxg3G1Z?= =?us-ascii?Q?XYdc8Rh/wGSi9HFKPq1tagGmtRNPHWfQ0i0krKu2ok5UHRPpwJKuEyo/WBUa?= =?us-ascii?Q?wh4xdPX/Th64gMjP1CTvx3pIbhsufZLiaSv4a4nxRLkyPqdnd7w3GLo6unG0?= =?us-ascii?Q?WYyHzHDYQU+5liKHY4nIhFk2aTmCPz3/ngikRg2fd/OBZtCqIQNlc6Le86gd?= =?us-ascii?Q?jGXvIwS2Np27acFFitxC6TSXY1mU24zk7IN4E5JCcfYwsQq3cHVmRodqtqrR?= =?us-ascii?Q?/y5A9HmmILrXoZgiwqRQWZUslv0+G2i5EDElOW/BJwgNCmVtiHWnz5+hzJXD?= =?us-ascii?Q?MUoPzLbtzo74+F1G0J3S2bxMQ/4ik7HyS3zWXcIYFYpZ1fjp3g9k490FJOhA?= =?us-ascii?Q?izediWHx1MBZGpskZ7sCiBu1hHPaTaIMSexp8Z9NS1Q0WNuqjXqjmq1OQFe5?= =?us-ascii?Q?FbuQiqFo1NwLuXYt4eM3UrhL/8Hxi87eHG24sPlmv3yDFf4TGDrWblTASKXV?= =?us-ascii?Q?dKLwwCtuTCICn8UaDjSKT3qESwYTq09VUSK/b7xRTJIh5e2WmT4ae6pGpcvZ?= =?us-ascii?Q?ZDhS3cuhZVK3n7DLvwwr9MEM/PluxkxN0UcW4xbAN3f5atWg/P2tAjRE6EAr?= =?us-ascii?Q?VM3jjAVzCqMKIEYlfCK4qXPt0Cae+6osQOFcpd1mM0AiXXiIYXUSudixp79s?= =?us-ascii?Q?9LcbaZaI31Bzr+xXjjqLOK8DQ9JXSPXYjjXD3kcjgaF5A7IPOg6zG6uFUMni?= =?us-ascii?Q?TgFi7rjAEFN37Oc8n7gga5E0WA96GTw90nZ+GPNZgixw+dq446nlqKV0YIQQ?= =?us-ascii?Q?yV8gnjpSdGPvNsq0KfvuHr5U9CvX5qUnvlzDUBwzCsEqlFhnhNypAB80xe/g?= =?us-ascii?Q?MWT3QefZ3n17EHb7ucmHA3P2epiAI87BhpVIXOG/o2muDhP+s53sQMOJTzhS?= =?us-ascii?Q?+kXV884DmGRaybJI2E9SYTwVPHqnDhSuG+8lzQVS8xzoLtzPlEyiEWkYqhVZ?= =?us-ascii?Q?8XAwcMTNyYJlZWmDbyq+2CHrHBKGE+FogblqGZXVYCEXo04RR/U/1lWIeKXk?= =?us-ascii?Q?kbVCkS0fl4Pg1TKTl1r7iYosE6nkMLeE1Y8SOxo809uwdC8uEo0MMKIjBV/G?= =?us-ascii?Q?Kl0UvYeW8lqfyqFC2XJa609iP6g7j+o0lunfoRhUPwLS0yD2Aj54d28Vhagh?= =?us-ascii?Q?MGENjfkIDPCvozGMUQbj4wVTFcohFrGkXMXa7CenQQ91LXMyGrtUWiqN59Eu?= =?us-ascii?Q?Ib8AXTyer+w3aoWz8o5faovnuoctkpQT8wvFAcikNf6tJpqrshixy7uL52aM?= =?us-ascii?Q?xBjeWaRFbNFk1Iyzguacmw+BgzQYaqyrV6pTPEBiEBn8LvBZujzopN7waBtu?= =?us-ascii?Q?k35ysnqbQxK8MZXnar87sv4CK3aCW6EGMpJ5Na16Z5jUFVxKJVOEKOIupmZC?= =?us-ascii?Q?Ax47xcwEB196WbFvsmlRT6V2Jm6AHZXyXimQ7ULsJNwOhAnVK8pfzJDrpuaI?= =?us-ascii?Q?jmnFlEiysDIelc6PZnlqF0OoOzWLUeCgP4xZgTdpTarDzQJGvnN52cD3OFZB?= =?us-ascii?Q?VbnmVOmWyc6PbNLmM1U=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 4077c7ec-a773-41d1-cacd-08dab1c8857e X-MS-Exchange-CrossTenant-AuthSource: LV2PR12MB5869.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 Oct 2022 11:53:21.9632 (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: 6lPcJ1aETTxaQo4UnF+9Kjbv+JEE2/LWmml/+gy3x9QKMD++6brib8kK0ymsFnEP X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB7307 On Wed, Oct 19, 2022 at 10:31:21AM +0200, Niklas Schnelle wrote: > On Tue, 2022-10-18 at 12:18 -0300, Jason Gunthorpe wrote: > > On Tue, Oct 18, 2022 at 04:51:30PM +0200, Niklas Schnelle wrote: > > > > > @@ -84,7 +88,7 @@ static void __s390_iommu_detach_device(struct zpci_dev *zdev) > > > return; > > > > > > spin_lock_irqsave(&s390_domain->list_lock, flags); > > > - list_del_init(&zdev->iommu_list); > > > + list_del_rcu(&zdev->iommu_list); > > > spin_unlock_irqrestore(&s390_domain->list_lock, flags); > > > > This doesn't seem obviously OK, the next steps remove the translation > > while we can still have concurrent RCU protected flushes going on. > > > > Is it OK to call the flushes when after the zpci_dma_exit_device()/etc? > > > > Jason > > Interesting point. So for the flushes themselves this should be fine, > once the zpci_unregister_ioat() is executed all subsequent and ongoing > IOTLB flushes should return an error code without further adverse > effects. Though I think we do still have an issue in the IOTLB ops for > this case as that error would skip the IOTLB flushes of other attached > devices. That sounds bad > The bigger question and that seems independent from RCU is how/if > detach is supposed to work if there are still DMAs ongoing. Once we do > the zpci_unregister_ioat() any DMA request coming from the PCI device > will be blocked and will lead to the PCI device being isolated (put > into an error state) for attempting an invalid DMA. So I had expected > that calls of detach/attach would happen without expected ongoing DMAs > and thus IOTLB flushes? "ongoing DMA" from this device shouuld be stopped, it doesn't mean that the other devices attached to the same domain are not also still operating and also still having flushes. So now that it is RCU a flush triggered by a different device will continue to see this now disabled device and try to flush it until the grace period. Jason