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Tue, 29 Sep 2026 10:32:25 +0000 Date: Tue, 29 Sep 2026 03:32:23 -0700 From: Peter Fang To: "Edgecombe, Rick P" CC: "sathyanarayanan.kuppuswamy@linux.intel.com" , "Hansen, Dave" , "kas@kernel.org" , "dave.hansen@linux.intel.com" , "seanjc@google.com" , "bp@alien8.de" , "x86@kernel.org" , "binbin.wu@linux.intel.com" , "hpa@zytor.com" , "mingo@redhat.com" , "linux-kernel@vger.kernel.org" , "Li, Xiaoyao" , "tglx@kernel.org" , "kvm@vger.kernel.org" , "linux-coco@lists.linux.dev" , "Bityutskiy, Artem" , "tony.lindgren@linux.intel.com" Subject: Re: [PATCH v5 4/6] virt: tdx-guest: Add a helper for the Quote buffer size Message-ID: References: <20260928100913.2265687-1-peter.fang@intel.com> <20260928100913.2265687-5-peter.fang@intel.com> <0c6bc71f-53fb-4240-83a3-c52d090044d3@intel.com> <42975a72efc3a0f96200c065cb86970e8f452625.camel@intel.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <42975a72efc3a0f96200c065cb86970e8f452625.camel@intel.com> X-ClientProxiedBy: SJ0PR03CA0095.namprd03.prod.outlook.com (2603:10b6:a03:333::10) 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_|IA1PR11MB8199:EE_ X-MS-Office365-Filtering-Correlation-Id: ffcad5ed-ddef-47e3-d266-08df1e14f433 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|23010399003|376014|7416014|10067099003|11063799006|56012099006|4143699003|18002099003|22082099003; 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Why is it doing what it is > > doing? This should also explain why it is page-aligning and caching things. > > I'm not sure it actually needs to be. It shortens the math in the places where > it needs to calculate the pages. And then in tdx_report_new_locked() it skips > zeroing the whole buffer (not sure why to zero the buffer actually. Seems it I talked to the TDX security folks and this seems to be a hygiene thing. Skipping the zeroing shouldn't pose a security risk. > could just zero the struct members, or maybe skip it). > > But actually, this series has a little bit of a change there? Because after this > helper is used, the whole page aligned buffer is zeroed regardless of the quote > size being aligned. Today the compile time constant buffer size happens to be > page aligned already though, so actually there is no change. That's a good point. I took Xiaoyao's suggestion to just always align [1], but maybe that was packing too much into one function. [1] https://lore.kernel.org/all/e6121cf3-83eb-4cc8-919e-2557fbcab3c9@intel.com/ > > But still, a more limited change would have get_quote_buf_size() return the un- > aligned size, like how the define is treated. Then leave the align logic alone > in the callers. Another patch (not in this series) could change that and maybe > make the memset() length in tdx_report_new_locked() make more sense. How about > it? Sounds good to me. > > I guess it just seems like this patch preps for the dynamic changes, while only > halfway addressing the align mysteries.