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Wed, 12 Aug 2026 21:02:45 +0000 Date: Wed, 12 Aug 2026 14:02:43 -0700 From: Peter Fang To: "Edgecombe, Rick P" CC: "seanjc@google.com" , "hpa@zytor.com" , "Li, Xiaoyao" , "bp@alien8.de" , "kas@kernel.org" , "binbin.wu@linux.intel.com" , "x86@kernel.org" , "sathyanarayanan.kuppuswamy@linux.intel.com" , "mingo@redhat.com" , "dave.hansen@linux.intel.com" , "linux-kernel@vger.kernel.org" , "Bityutskiy, Artem" , "tglx@kernel.org" , "linux-coco@lists.linux.dev" , "kvm@vger.kernel.org" Subject: Re: [PATCH v3 0/4] tdx-guest: Make Quote buffer size dynamic Message-ID: <20260812210243.GC1013044@pedri> References: <20260729122939.1340412-1-peter.fang@intel.com> <80b4ea89ebf17398c3bee21d157c7f97ea32aadf.camel@intel.com> <86d532f33816cd4fa3e29c40079a6003abf89324.camel@intel.com> Content-Type: text/plain; charset="utf-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <86d532f33816cd4fa3e29c40079a6003abf89324.camel@intel.com> X-ClientProxiedBy: SJ0PR13CA0059.namprd13.prod.outlook.com (2603:10b6:a03:2c2::34) To PH0PR11MB5643.namprd11.prod.outlook.com (2603:10b6:510:d5::21) 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: PH0PR11MB5643:EE_|MW3PR11MB4763:EE_ X-MS-Office365-Filtering-Correlation-Id: 15611715-f7c3-409c-ca43-08def8b50eac X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|376014|7416014|23010399003|22082099003|18002099003|56012099006|11063799006|4143699003|10067099003; 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But I kind of came to a different > conclusion on what went wrong. > > It seems to me that from the overall solution level, the report should never > have had the details in it. It should just be some nonce or some type of thing > that can tie the guest request to the quote that it ends up getting > back. Doesn't it seem weird to get a bunch of details from the TDX module, then > pass them from the guest to host KVM to host userspace then back to the TDX > module... which already had all those details? Yeah this has been a source of much debate internally. I feel that the directions boil down to: is now a good opportunity to design something that's more future looking (like can scale better wrt future attestation needs) or is it better to keep the old SGX design a little longer... > > My understanding was that the original SGX attestation was a complicator of the > design of this stuff. Because I'm not sure that SGX had all those details about > the TD. In fact I can't see how it could have. Is that right Peter? So it needs > them all to be passed in. All the extra validations etc of this shuffling is > TDX's problems to deal with, but for Linux, it would be at least a lot less > confusing if there was not two things that have the TD details in them. Yep this is correct IMO. Basically the report has lots of old SGX baggage. > > That said, from KVM POV, (1) kicks the attestation out of KVM. I see the > benefit. But a TD quote is a TD scoped operation in concept. To me at least.