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Wed, 16 Sep 2026 00:34:39 +0000 Date: Tue, 15 Sep 2026 17:34:37 -0700 From: Peter Fang To: "Edgecombe, Rick P" CC: "kvm@vger.kernel.org" , "linux-coco@lists.linux.dev" , "Li, Xiaoyao" , "dave.hansen@linux.intel.com" , "linux-kernel@vger.kernel.org" , "seanjc@google.com" , "binbin.wu@linux.intel.com" , "kas@kernel.org" , "mingo@redhat.com" , "tony.lindgren@linux.intel.com" , "hpa@zytor.com" , "tglx@kernel.org" , "bp@alien8.de" , "Bityutskiy, Artem" , "sathyanarayanan.kuppuswamy@linux.intel.com" , "x86@kernel.org" Subject: Re: [PATCH v4 0/4] tdx-guest: Make Quote buffer size dynamic Message-ID: References: <20260915092632.2822169-1-peter.fang@intel.com> <96c33d465635c1858b943960f09ebd3bf82d31f1.camel@intel.com> Content-Type: text/plain; charset="utf-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-ClientProxiedBy: BY3PR03CA0011.namprd03.prod.outlook.com (2603:10b6:a03:39a::16) To CH3PR11MB435924.namprd11.prod.outlook.com (2603:10b6:610:34a::8) 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: CH3PR11MB435924:EE_|SN7PR11MB6725:EE_ X-MS-Office365-Filtering-Correlation-Id: 368a68b1-3347-40b8-abbe-08df138a4af6 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|23010399003|376014|7416014|1800799024|56012099006|11063799006|4143699003|10067099003|22082099003|18002099003; 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Patch 4 added this: > > > >         if (quote_size) > >                 /* The reported size does not include the buffer header */ > >                 len = TDX_QUOTE_BUF_LEN(quote_size); > > > > And it is about adding the GHCI header to the buffer size. So if there > > is a design change and this header is no longer needed, this line could > > become redundant. The macro might cause the driver to allocate more > > memory than needed (up to one page), so things should still work and we > > could fix this up later. > > So this series uses a new ability to query the max size of the quote. This size > applies to SGX quotes too. > > Depending on the DICE design, the guest quoting code may need to change. Maybe > heavily. These changes could touch LOC in this series as well as other TDX guest > quoting code. But the code is still correct and useful based on non-DICE > existing quoting. > > Is it all correct? Yes. If a new TDX module decides to report this field on a non-DICE platform, this code still works [1]. And quotes in the DICE world will continue to get larger. This metadata reporting is useful regardless of how DICE is implemented in the end. I wanted to be upfront about what the potential impact may be if the guest did DICE differently. The guest would still need this reported size from the TDX module. [1] https://lore.kernel.org/kvm/apsxN4jYe3G3meNz@intel.com/