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Mon, 14 Jul 2025 08:44:25 +0000 Date: Mon, 14 Jul 2025 16:44:15 +0800 From: Chao Gao To: Kai Huang CC: , , , , , , , , , Subject: Re: [PATCH v2 1/2] KVM: x86: Reject KVM_SET_TSC_KHZ VM ioctl when vCPUs have been created Message-ID: References: <135a35223ce8d01cea06b6cef30bfe494ec85827.1752444335.git.kai.huang@intel.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <135a35223ce8d01cea06b6cef30bfe494ec85827.1752444335.git.kai.huang@intel.com> X-ClientProxiedBy: SG2PR03CA0093.apcprd03.prod.outlook.com (2603:1096:4:7c::21) To CH3PR11MB8660.namprd11.prod.outlook.com (2603:10b6:610:1ce::13) 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: CH3PR11MB8660:EE_|SA1PR11MB8857:EE_ X-MS-Office365-Filtering-Correlation-Id: 52114cec-b8e0-411c-f11e-08ddc2b2a2fe X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|376014|7053199007; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?XtjiPoA9+kdH2574ebTcbsep5x1r/Pal611RM1ucRilndWhTmDcdIu/V5BOG?= =?us-ascii?Q?4eDBTbjoHjQ4kbCQXYnSxaNM7YrYHooy/KiYyAvgdW3PqYE0FbAbxqqKdv6n?= =?us-ascii?Q?/mhNB9LU3tpXB4TODw8SXRd7P/BrVmrE6KBwNX8GasaVFOO0CUWsr5re+nhs?= =?us-ascii?Q?JR3mBRSGXsdFtGok8OeP2aNcvwonLmuVoSQCorxaIdJhqF31e83bsACmorL9?= =?us-ascii?Q?5F6jBsoycHZHlHav7xfC5SV3HfVoAA9TrYT03TkZw1cpW6Bhj0cuXn87aWYC?= =?us-ascii?Q?lTuz7r+7ha8ELmJNky2GSdJB4AwDJs45IE7JHbWMchLefc8ci79iwiHmftag?= =?us-ascii?Q?UCAiSP4DtFWWjS80n4lemhdSQxRRpEbuaUom6ZTKpZg3cnuHeyaPaJnDq2ox?= =?us-ascii?Q?DQxnwJPbMdRiUsuVvY8TdISAXYNq0WYUTw508X6f4sxXu2GPLkyWFC9Ja9lR?= =?us-ascii?Q?jUZTM6Tj33A05AWngh5WQubz8rDrto6CKBjhEWqVm+txBMi/z1ql7wYLeb3a?= =?us-ascii?Q?Ifpq4r1ERxC+DOWxy88seAVYEdQnLTU8g4RCS3AVAUlnnBcl4qmohuGHzwHP?= =?us-ascii?Q?ueyHgdS6ysP3cK6l2sYvi05pHIei054OpGbw8b3SY+rmrjLn1eQfMSOs/+10?= =?us-ascii?Q?0MPGS7LfwZ+lrIU5wQkUDC4LejXb/EN526DXHX47MyH8Us6n/rRDEHUWzeRg?= =?us-ascii?Q?bokmBtNrKkprfoS6722nZWMsvql2SzTYSiLiUJOFEgGRViV4zAoc4Ozreast?= =?us-ascii?Q?xn6nL2NpsScOJV9UUWlkQ9sVXQLYvu1/Yfy15wAFpJljHM9ZWjEn7ZtBX3oO?= =?us-ascii?Q?bEuVKlcKqPnvP70gaPoX/E0xPLqP1LR8jdE9Qhnn/QvLLJKQr3XLou0bqFhn?= =?us-ascii?Q?p/gaBSCfidYRscf8wBjx3XkHEBnoxnjotC0cVGRhMmQxUCfWSHCc94bSH0cZ?= =?us-ascii?Q?JJhXIstCfMzAn4WZT4+IAjnB4Z3h9wQoWkXiBIT1M3r420IQP8cJW8/ZgXFG?= =?us-ascii?Q?udCQMsuB3L7uqWpPaBIRhnv1HfSCYQ+hRNboYcZKyC3Li7UhdfwiJnJ/4PRE?= =?us-ascii?Q?hTKjYE5TTm/mLGpS/xbQzlUvmyUM8PmLqEBYhfjOVohmIBQGebsivckW6mHD?= =?us-ascii?Q?xpzdxvWlYa4ieU8KmHNNapYBfB6EO7noye+nQplklKQPg2syQcqxyb32N0z+?= =?us-ascii?Q?65npej4e3X7LdvUPPPoM5fknPp6na4ikl2n3Q2WDWYcNCgv5HeUtP/XPOti4?= =?us-ascii?Q?ShmSbp4Hh+BalZ1KVRevquV8alfSFvzFP4+0OauP69u6xXufkyD18TJ3Hg5F?= =?us-ascii?Q?TZ2ONCvhbwCzrWG6VMpfX7JJrfzDvgc6QsBikmHGb4P0g1HAMw4MtiR0p+L9?= =?us-ascii?Q?STkfXk58UmpTlkVMrS99hxyXdoF7MstuHZlYZYJUwWuxW49OIWGuNMrDtKvz?= =?us-ascii?Q?5HbtWHHweRZ4ACy7aE5/kKBFKBRwQ6gYmoBVyJvPHA1dK7xqms+igzASLfif?= =?us-ascii?Q?qFBdYH0Z3lIwwSugpr5vvCwReXLMCucUnFKfm4qKk6aZAO/pFcpsr6SZ+gBm?= =?us-ascii?Q?jWsUQdiVzqYj8gvYQPIlRsGDkF0H3vthIl+gqAHi?= X-MS-Exchange-CrossTenant-Network-Message-Id: 52114cec-b8e0-411c-f11e-08ddc2b2a2fe X-MS-Exchange-CrossTenant-AuthSource: CH3PR11MB8660.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 Jul 2025 08:44:25.2314 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: mgFOTzo5GD8WeBNTsQFumqjEisL76aqMT/HXPbP0pKwUm9IxfPMZIdZMhV882NE9YMY/u4qDGqOvugXi+gpEqQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR11MB8857 X-OriginatorOrg: intel.com On Mon, Jul 14, 2025 at 10:20:19AM +1200, Kai Huang wrote: >Reject the KVM_SET_TSC_KHZ VM ioctl when vCPUs have been created and >update the documentation to reflect it. > >The VM scope KVM_SET_TSC_KHZ ioctl is used to set up the default TSC >frequency that all subsequently created vCPUs can use. It is only >intended to be called before any vCPU is created. Allowing it to be >called after that only results in confusion but nothing good. > >Note this is an ABI change. But currently in Qemu (the de facto >userspace VMM) only TDX uses this VM ioctl, and it is only called once >before creating any vCPU, therefore the risk of breaking userspace is >pretty low. > >Suggested-by: Sean Christopherson >Signed-off-by: Kai Huang >Reviewed-by: Xiaoyao Li Reviewed-by: Chao Gao