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Fri, 1 Apr 2022 06:20:49 +0000 Received: from PH0PR11MB5658.namprd11.prod.outlook.com ([fe80::bc9d:6f72:8bb1:ca36]) by PH0PR11MB5658.namprd11.prod.outlook.com ([fe80::bc9d:6f72:8bb1:ca36%8]) with mapi id 15.20.5123.025; Fri, 1 Apr 2022 06:20:48 +0000 Message-ID: <81ea9536-ba36-deef-b849-6b407b5409e0@intel.com> Date: Fri, 1 Apr 2022 14:20:23 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Firefox/91.0 Thunderbird/91.5.0 Subject: Re: [PATCH RFC v2 02/11] iommu: Add iommu_group_singleton_lockdown() Content-Language: en-US To: Jason Gunthorpe , "Tian, Kevin" References: <20220329053800.3049561-1-baolu.lu@linux.intel.com> <20220329053800.3049561-3-baolu.lu@linux.intel.com> <20220329114259.GB1716663@nvidia.com> From: Yi Liu In-Reply-To: <20220329114259.GB1716663@nvidia.com> X-ClientProxiedBy: HK0PR01CA0049.apcprd01.prod.exchangelabs.com (2603:1096:203:a6::13) To PH0PR11MB5658.namprd11.prod.outlook.com (2603:10b6:510:e2::23) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: b37f50f8-331d-47cf-9e0e-08da13a7c34d X-MS-TrafficTypeDiagnostic: SN6PR11MB3294:EE_ X-LD-Processed: 46c98d88-e344-4ed4-8496-4ed7712e255d,ExtAddr X-Microsoft-Antispam-PRVS: X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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charset="us-ascii"; Format="flowed" Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On 2022/3/29 19:42, Jason Gunthorpe wrote: > On Tue, Mar 29, 2022 at 08:42:13AM +0000, Tian, Kevin wrote: > >> btw I'm not sure whether this is what SVA requires. IIRC the problem with >> SVA is because PASID TLP prefix is not counted in PCI packet routing thus >> a DMA target address with PASID might be treated as P2P if the address >> falls into the MMIO BAR of other devices in the group. This is why the >> original code needs to strictly apply SVA in a group containing a single >> device, instead of a group attached by a single driver, unless we want to >> reserve those MMIO ranges in CPU VA space. > > I think it is not such a good idea to mix up group with this test > > Here you want to say that all TLPs from the RID route to the host > bridge - ie ACS is on/etc. This is subtly different from a group with > a single device. Specifically it is an immutable property of the > fabric and doesn't change after hot plug events. so the group size can be immutable for specific topology. right? I think for non-multi-function devices plugged behind an PCIE bridge which has enabled ACS, such devices should have their own groups. Under such topology the group size should be 1 constantly. May just enable SVA for such devices. > ie if we have a singleton group that doesn't have ACS and someone > hotplugs in another device on a bridge, then our SVA is completely > broken and we get data corruption. I think this may be a device plugged in a PCIE-to-PCI bridge, and then hotplug a device to this bridge. The group size is variable. right? Per my understanding, maybe such a bridge cannot support PASID Prefix at all, hence no SVA support for such devices. -- Regards, Yi Liu _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3A34CC433F5 for ; Fri, 1 Apr 2022 06:21:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245365AbiDAGWu (ORCPT ); Fri, 1 Apr 2022 02:22:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52658 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245361AbiDAGWq (ORCPT ); Fri, 1 Apr 2022 02:22:46 -0400 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 558B425FD42 for ; 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Fri, 1 Apr 2022 06:20:49 +0000 Received: from PH0PR11MB5658.namprd11.prod.outlook.com ([fe80::bc9d:6f72:8bb1:ca36]) by PH0PR11MB5658.namprd11.prod.outlook.com ([fe80::bc9d:6f72:8bb1:ca36%8]) with mapi id 15.20.5123.025; Fri, 1 Apr 2022 06:20:48 +0000 Message-ID: <81ea9536-ba36-deef-b849-6b407b5409e0@intel.com> Date: Fri, 1 Apr 2022 14:20:23 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Firefox/91.0 Thunderbird/91.5.0 Subject: Re: [PATCH RFC v2 02/11] iommu: Add iommu_group_singleton_lockdown() Content-Language: en-US To: Jason Gunthorpe , "Tian, Kevin" CC: Lu Baolu , Joerg Roedel , Christoph Hellwig , "Raj, Ashok" , Will Deacon , Robin Murphy , Jean-Philippe Brucker , Eric Auger , "Pan, Jacob jun" , "iommu@lists.linux-foundation.org" , "linux-kernel@vger.kernel.org" References: <20220329053800.3049561-1-baolu.lu@linux.intel.com> <20220329053800.3049561-3-baolu.lu@linux.intel.com> <20220329114259.GB1716663@nvidia.com> From: Yi Liu In-Reply-To: <20220329114259.GB1716663@nvidia.com> Content-Type: text/plain; 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IIRC the problem with >> SVA is because PASID TLP prefix is not counted in PCI packet routing thus >> a DMA target address with PASID might be treated as P2P if the address >> falls into the MMIO BAR of other devices in the group. This is why the >> original code needs to strictly apply SVA in a group containing a single >> device, instead of a group attached by a single driver, unless we want to >> reserve those MMIO ranges in CPU VA space. > > I think it is not such a good idea to mix up group with this test > > Here you want to say that all TLPs from the RID route to the host > bridge - ie ACS is on/etc. This is subtly different from a group with > a single device. Specifically it is an immutable property of the > fabric and doesn't change after hot plug events. so the group size can be immutable for specific topology. right? I think for non-multi-function devices plugged behind an PCIE bridge which has enabled ACS, such devices should have their own groups. Under such topology the group size should be 1 constantly. May just enable SVA for such devices. > ie if we have a singleton group that doesn't have ACS and someone > hotplugs in another device on a bridge, then our SVA is completely > broken and we get data corruption. I think this may be a device plugged in a PCIE-to-PCI bridge, and then hotplug a device to this bridge. The group size is variable. right? Per my understanding, maybe such a bridge cannot support PASID Prefix at all, hence no SVA support for such devices. -- Regards, Yi Liu