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Tue, 15 Sep 2026 00:14:36 +0000 Message-ID: <085c28db-31e3-4249-a9be-a2f9d7156719@intel.com> Date: Mon, 14 Sep 2026 17:14:32 -0700 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v2 2/4] KVM: x86: Add optional KVM_CAP_LIVE_MIGRATION and KVM_MIGRATE_CMD To: Tony Lindgren CC: Artem Bityutskiy , =?UTF-8?B?SsO2cmcgUsO2ZGVs?= , Paolo Bonzini , Sean Christopherson , Peter Xu , Fabiano Rosas , Jon Grimm , Pankaj Gupta , Tom Lendacky , Marc Zyngier , Oliver Upton , Steven Price , Anup Patel , Samuel Ortiz , =?UTF-8?B?SmFrdWIgUsWvxb5pxI1rYQ==?= , Vishal Annapurve , "Elena Reshetova" , Kai Huang , "Mika Westerberg" , Peter Fang , Rick Edgecombe , "Xiaoyao Li" , Xu Yilun , References: <20260831071304.762939-3-tony.lindgren@linux.intel.com> <4c07e70e-7639-4141-b602-1c09c9c7510c@intel.com> <0cf5b79e-521d-4c7c-97f2-673c51d42bbd@intel.com> Content-Language: en-US From: Kishen Maloor In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: MW4P223CA0024.NAMP223.PROD.OUTLOOK.COM (2603:10b6:303:80::29) To DS0PR11MB8050.namprd11.prod.outlook.com (2603:10b6:8:117::5) Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS0PR11MB8050:EE_|CYYPR11MB8357:EE_ X-MS-Office365-Filtering-Correlation-Id: a07fa553-c396-4998-7521-08df12be5311 X-LD-Processed: 46c98d88-e344-4ed4-8496-4ed7712e255d,ExtAddr X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|7416014|376014|1800799024|366016|22082099003|18002099003|3023799007|4143699003|11063799006|10067099003|56012099006; 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Yes we can set it on init, but would >>> be nice to have some generic way to do it for qemu -incoming. >> >> I'd separate these. >> >> On the role: it seems we agree on recording roles per-session. My only point >> then is that a VM created through the delayed_init flow doesn't additionally >> need a destination role recorded for it if SETUP will assert one when the >> migration is kicked off. >> >> On generic plumbing for -incoming: is this about KVM_TDX_INIT_VM_F_DELAY_INIT? >> A generic mechanism would make sense to me if the flag were consumed by generic >> KVM code, but that isn't the case here. Userspace has to make a >> vendor-specific VM-init call like KVM_TDX_INIT_VM anyway, with the flag passed >> on that call. So I'm not sure what a generic version would add, unless you have >> something else in mind. > > So we could add a SETUP subcommand SET_ROLE or SET_INCOMING. It might be better to pass the role as a parameter of the SETUP call rather than a separate SET_ROLE call. A separate SET_ROLE would bring its own ordering rules relative to the other SETUP sub-commands. The specific role (src or dst) still needs someplace to go, and flags is already the sub-command selector. An option is to carve out room in the __u32 reserved field to carry a role argument, something like 0=unset, 1=src, 2=dest so KVM can verify that a role was indeed set. It could further be written into a generic KVM struct (kvm_arch or kvm) which could be queried on KVM_TRANSFER_MEMORY, etc. to identify the relevant callback.