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Fri, 14 Mar 2025 12:04:12 +0000 Message-ID: <791efd0e-4e43-446e-b637-1f9ed49d0c32@intel.com> Date: Fri, 14 Mar 2025 20:09:37 +0800 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] iommu/amd: Add Secure ATS support To: Jason Gunthorpe , Vasant Hegde CC: "Tian, Kevin" , Robin Murphy , "iommu@lists.linux.dev" , "joro@8bytes.org" , "will@kernel.org" , "suravee.suthikulpanit@amd.com" References: <4fba254e-ca47-4e7b-baf3-0228d9605c2b@amd.com> <942a1a66-5c18-43e2-886e-df38cb3e7258@intel.com> <54db17d7-b150-4579-a33d-f1b5cc8943bc@amd.com> <6eb0ec90-5859-4605-8a2e-657f6f711d61@intel.com> <825ddadd-6770-46b5-936e-f17988534984@amd.com> <13e1e1d8-5870-44ea-a800-e5b25bafd344@intel.com> <20250303183801.GW5011@ziepe.ca> <391a2333-0373-4cd3-a858-349230bc7c90@amd.com> <20250304142402.GB5011@ziepe.ca> Content-Language: en-US From: Yi Liu In-Reply-To: <20250304142402.GB5011@ziepe.ca> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: KU1PR03CA0024.apcprd03.prod.outlook.com (2603:1096:802:18::36) To DS0PR11MB7529.namprd11.prod.outlook.com (2603:10b6:8:141::20) 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: DS0PR11MB7529:EE_|SJ2PR11MB7473:EE_ X-MS-Office365-Filtering-Correlation-Id: 00b749ab-d2bd-415f-0f83-08dd62f0557b X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|366016|1800799024; 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We may have to add more logic in >> sysfs store/show code path. But user will know what is supported and what they >> can pick. > > A sysfs type thing is what I'm thinking > > Just trying to understand what options we should be providing to > userspace.. > > I am sensitive that we'd like to disble ATS for identity modes in many > common cases and we get that implicitly today. > >> Also sysfs knob needs new domain ops to communicate changes to indivisual >> driver. Like in store path >> - validate the input >> - make sure driver is unbond so that its safe to modify the >> - New ops to communicate to indivisual driver >> something like ops->set_ats_mode(dev, mode) > > Yeah this needs to be considered.. I wonder if a flags input to attach > is the right way to go. Do we expect this flag to setup the SATS in the underlying iommu driver? If yes, I doubt if it is proper. My reason as below: he reason is more for the #4 case you summarized in earlier mails of this thread. Such HWs need to map the PA in the DPT/HPT table when a given PA is mapped to IOVA. We may just hook the DPT/HPT map/unmap to the map/unmap of a paging domain. Hence it's better to determine if the DPT/HPT is desired per allocation. Otherwise it may requires upper layer to replay the mapping. e.g. iommufd replay the mappings stored in IOAS->iopt " 4) TA is an full physical address and the IOMMU validates the full physical using some kind of permission structure (ARM calls this Device Permission Table) " > > That would be convenient for how SMMUv3 is structued now as it can just > switch modes hitlessly with its existing logic. I think all drivers > should have a similar design. I think this is more like we have done for the set_dev_pasid op. Now it supports replacing domain. But as I replied in above, add a flag in the attach op might not be a good idea. -- Regards, Yi Liu