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Thu, 29 Jan 2026 14:07:50 +0000 Date: Thu, 29 Jan 2026 22:07:37 +0800 From: Chao Gao To: Dave Hansen CC: , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v3 05/26] coco/tdx-host: Expose TDX Module version Message-ID: References: <20260123145645.90444-1-chao.gao@intel.com> <20260123145645.90444-6-chao.gao@intel.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: KU1PR03CA0044.apcprd03.prod.outlook.com (2603:1096:802:19::32) To CH3PR11MB8660.namprd11.prod.outlook.com (2603:10b6:610:1ce::13) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH3PR11MB8660:EE_|CO1PR11MB4916:EE_ X-MS-Office365-Filtering-Correlation-Id: 3cddc065-0744-415f-d633-08de5f3fc949 X-LD-Processed: 46c98d88-e344-4ed4-8496-4ed7712e255d,ExtAddr X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|366016|1800799024; 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AMD has a PCI device for the PSP for SEV which provides an >> existing place to hang their equivalent metadata. >> >> 2. ARM CCA will likely have a faux device (although it isn't obvious >> if they have a need to export version information there) [1] >> >> 3. Microcode revisions are exposed as CPU device attributes > >I kinda disagree with the idea that this follows existing patterns. It >uses a *NEW* pattern. > >AMD doesn't use a faux device because they *HAVE* a PCI device in their >architecture. TDX doesn't have a PCI device in its hardware architecture. > >ARM CCA doesn't exist in the tree. > >CPU microcode doesn't use a faux device. For good reason. The microcode >version is *actually* per-cpu. It can differ between CPU cores. The TDX >module version is not per-cpu. There's one and only one global module. >This is the reason that we need a global, unique device for TDX. > >I'm not saying that being new is a bad thing. But let's not pretend this >is following any kind of existing pattern. Let's explain *why* it needs >to be different. Thanks. I understand your point. The pattern I was referring to is: using a device (PCI device, virtual device, or faux device) and exposing versions/metadata as device attributes. You're right if we look at the details, they're not exactly the same pattern. I'll revise the changelog to make this clearer.