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Shutemov" , Juergen Gross , "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Ajay Kaher , Jan Kiszka , Paolo Bonzini , Andy Lutomirski , Peter Zijlstra , linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev, virtualization@lists.linux.dev, linux-hyperv@vger.kernel.org, kvm@vger.kernel.org, xen-devel@lists.xenproject.org, Nikunj A Dadhania References: <20250201021718.699411-1-seanjc@google.com> <20250201021718.699411-4-seanjc@google.com> <20250211173238.GDZ6uJtkVBi8_X7kia@fat_crate.local> <20250211203250.GHZ6uz8qs-bzcbi0_b@fat_crate.local> From: Tom Lendacky In-Reply-To: <20250211203250.GHZ6uz8qs-bzcbi0_b@fat_crate.local> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: SA9PR10CA0008.namprd10.prod.outlook.com (2603:10b6:806:a7::13) To DM4PR12MB5070.namprd12.prod.outlook.com (2603:10b6:5:389::22) 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: DM4PR12MB5070:EE_|DS7PR12MB8346:EE_ X-MS-Office365-Filtering-Correlation-Id: 58a9e2f9-fddd-4939-1484-08dd4b8546c0 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|1800799024|366016; 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For kernels that will never run in a VM, >> pulling in all the SEV guest code just to enable host-side support for SME (and >> SEV) is very undesirable. > > Well, that might've grown in the meantime... when we started it, it was all > small so it didn't really matter and we kept it simple. That's why I never > thought about it. And actually, we've been thinking of even ripping out SME > in favor of TSME which is transparent and doesn't need any SME glue. But there > was some reason why we didn't want to do it yet, Tom would know. I think it was because TSME is a BIOS setting and you don't trust BIOS to always expose the setting :) I do have a patch series to remove SME. I haven't updated it in a couple of releases, so would just need to dust it off and rebase it. Thanks, Tom > > As to carving it out now, meh, dunno how much savings that would be. Got > a student to put on that task? :-P > >> And in this case, because AMD_MEM_ENCRYPT gates both host and guest code, it >> can't depend on HYPERVISOR_GUEST like it should, because taking a dependency on >> HYPERVISOR_GUEST to enable SME is obviously wrong. > > Right. >