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Tue, 14 Jul 2026 06:18:12 +0000 Date: Mon, 13 Jul 2026 23:18:11 -0700 From: Peter Fang To: Binbin Wu CC: Dave Hansen , Kiryl Shutsemau , Rick Edgecombe , "Kuppuswamy Sathyanarayanan" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , , "H. Peter Anvin" , , , Subject: Re: [PATCH 2/2] virt: tdx-guest: Allocate Quote buffer dynamically Message-ID: <20260714061811.GD3178326@pedri> References: <20260612110853.3188196-1-peter.fang@intel.com> <20260612110853.3188196-3-peter.fang@intel.com> <62069ec6-b586-446a-a696-6aa3356ac665@linux.intel.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <62069ec6-b586-446a-a696-6aa3356ac665@linux.intel.com> X-ClientProxiedBy: SJ0PR05CA0078.namprd05.prod.outlook.com (2603:10b6:a03:332::23) To SJ0PR11MB5645.namprd11.prod.outlook.com (2603:10b6:a03:3b9::19) Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ0PR11MB5645:EE_|CO1PR11MB5106:EE_ X-MS-Office365-Filtering-Correlation-Id: dc49cd32-2dbc-419e-738f-08dee16faefd X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|23010399003|1800799024|376014|7416014|18002099003|22082099003|11063799006|56012099006|4143699003; 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This may be too small for Quotes using schemes > > such as post-quantum cryptography (PQC), where certificate chains can > > increase the Quote size to several megabytes. > > Nit: > I think the description here should be more accurate. > "Several megabytes" colloquially implies sizes that could easily exceed 4 MB. > And it's a slight contradiction VS the 4MB limitation below. Good point. I'll make this clearer. > > > > > Allocate the Quote buffer based on the size reported by the TDX module > > instead of always reserving a fixed-size buffer. This avoids wasting > > memory on platforms that do not require larger Quotes. Older platforms > > fall back to the default 128 KB buffer. > > > > Because the Quote buffer must be physically contiguous, its size is > > bound by the buddy allocator's maximum page order (4 MB), which should > > be sufficient for current attestation needs. > > > > struct tdx_quote_buf has a trailing flexible array, so use offsetof() > > instead of sizeof() to calculate the header size. > > > > Signed-off-by: Kuppuswamy Sathyanarayanan > > Assisted-by: Claude:claude-opus-4-7 > > Assisted-by: GitHub Copilot:gpt-5.4 > > Same issue as pointed by Kiryl in the first patch. There have been discussions about this recently [1]. I think perhaps I should drop the "Assisted-by" tags since I did not use AI to write the actual code. [1] https://lore.kernel.org/linux-coco/akxHbKbMyF7PZ0Av@google.com/ > > > Signed-off-by: Peter Fang > > Also the use of struct_size_t() instead of offsetof(). Yep. > > Otherwise looks okay to me: > > Reviewed-by: Binbin Wu Thanks for the review Binbin!