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X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?VG11MHBEOG1nSHZ3a0FRbmkvaExDeGhob3A0RGZQS0thaVVKamI4VjNya2Nt?= =?utf-8?B?T1pDc0ZwWTErRUgxa2cwRld1Y0Y2L3hDTWpoSDJ1Vk9sSjdjMy9sN0tZT0NX?= =?utf-8?B?WlFONWVtMWNUSXJhRG1VZTN2NGY5dnNKZlczYTAzS3dUSCtwSHZSVmxBTSs0?= =?utf-8?B?OVZUZmE2NHdsejhBQ2NjR1pvWGhjanFtZTJjWTdNL3lhNUxiOXdwOU9abUcy?= =?utf-8?B?a1BrRUNCTTA0bXltZzNGUnpBa0FpS3RldjNidGdNU2JmOUxndkVUYng0R2p3?= =?utf-8?B?TG0wMTZHSXRqVk5uYlkrUytDdWhCaHRvaW10bXhvQnNoVjBXdVZJM2dScXlZ?= =?utf-8?B?Si8wM0xrVDd6c3JncFpoUmg5TTlGVVpWazlsMW1hSTZzb0lKWkdWb1VjTHZB?= =?utf-8?B?Z2ZlRWY2emliS1BVSm01cGlHelF5Vkk3NXNFZkJ5UXB1TTg5eXppSDBtZHds?= =?utf-8?B?bWR5KzNveWYxaHU0UlBUZGwyYjl1Y2ZJb05rOUNYaE9pd1pFd1RUS1c0UE5k?= =?utf-8?B?M0xEbmo1c3luM2dBemFvTmpFWG1VTkxuRGFtN3F6NWFMcGhhRm5vbWtZSGJN?= =?utf-8?B?ZUNmOThYRmx2ZDVxRFdqeXBJaENFcEdwVnYxTjdMTGNvTDhnT3NIWXl0ZUxV?= =?utf-8?B?dzMzNWV6SHlEQ2tDZDZEWUJmblVGSXdIbGwyZjZ4dDlXYlB6Z2s5alhlb0tm?= =?utf-8?B?aUMrZ3hUVnZrQkFjZEYveFhkclBYMGNWSDBuL0ZjdUwrMU1LMFN2OWo4RXV5?= =?utf-8?B?L0U0ZW9sT05WSER6U1c1SnVVR3g0ejNjM1pTcDEzZ2RTaUtIQ3BDVnUxYlpt?= =?utf-8?B?YUQ2K3gxOE9RaExoTldvaHVyMXl5RXFnb09RaDMxaUVPMXpYUUc5cEEyT3BS?= =?utf-8?B?SVM1ZkYxc0JHWk54bHExRHg5cHlUb21SbnVIYVQ2OWFaNHFsSEdHSjhHL2l0?= =?utf-8?B?M1Y3YnZyWjQxcHVUdkU5ODRjTnhZMlBjcHZCS1RTWGJaSFZ2VlNVcktQNWU2?= =?utf-8?B?ZUlBQ3VMdE42OTRUQmhMZG5OSjIrTVNhV1J2Y0RuZ3RzM2o2VmJ3d2hBRjdi?= =?utf-8?B?WFJHbEx6UkVGLzdTOXFDZkJmQVVzVUtjdmpVcFdxZVpzRWg5a3BRSHUwOUNm?= =?utf-8?B?eFUyMUlUQURGTnpEY1YvRUQrRlF3ZlNJMjJRZ1lYTGNMNFBkc2hMNkxremky?= =?utf-8?B?WDhYQUZ0Ymg5dXFQTDZIVU1JU0d0aG9SL2tEWUJjRm5iakR1WnR0TXJpWEt4?= =?utf-8?B?K2I3bFJ3eGN5TkFLTTNZZWg1VkRXZTM2dzV0YVA4eTZyZnc3djh2eDRUck9t?= =?utf-8?B?bHRGZS9KMytIU3BBL1ZrSlhOSWpZMUN6REdMTWNibFZGMng5QnlwR2NvRXB3?= =?utf-8?B?Sitjaks3QU9hVEQwcGJPYkFNWVBSTk52UGdmK0IrQk5weDJlMzFTVzVMUHpW?= =?utf-8?B?ODRoZ2YzdXhwWENhb09DUVEwVzZtRTdjcEZUSklKRDBGRkhGODQ3dTlVUTdE?= =?utf-8?B?c0pGN1FnMEg5VUdPRXRVMy9ya3pzdmNNMkh2ellGVzlRVGtpMFI2M0p3b1Vs?= =?utf-8?B?eWljUnlkakJRNjh0TkdnT0dzL1ordjJXM25Pb0krSmxFRTNpVHlJRzA5Q0Qw?= =?utf-8?B?QlY5WDE0dk95K29aRUg0UjM0MTZnVW1PUm00VGZZWURqVTdCRDdWaVk5MjZY?= =?utf-8?B?WFhhVyt1K1kzcXpJRHNlTk11ajRwVGk5T05JNG5PUE1iUW93Z0FOazZwVDMv?= =?utf-8?Q?oXvI/kkNtCmj1CdndTlxoH5jPt3AAcj3/FhMioD?= X-MS-Exchange-CrossTenant-Network-Message-Id: f404b2e5-ac65-47ec-d4e2-08d8df200c53 X-MS-Exchange-CrossTenant-AuthSource: DS7PR03MB5608.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Mar 2021 15:13:21.8383 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 335836de-42ef-43a2-b145-348c2ee9ca5b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: oTXM9Els0B0DR8it4ti8jcjwpLO2CH9hv1fNcoT2qBrAE0vL2yLoJmE0WumYFvvDhhblScFlZNi0qUgTI7b12Q== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR03MB3146 X-OriginatorOrg: citrix.com On Thu, Mar 04, 2021 at 02:59:38PM +0000, Ian Jackson wrote: > Roger Pau Monne writes ("[PATCH v2 for-4.15] x86/msr: introduce an option for HVM relaxed rdmsr behavior"): > > Introduce an option to allow selecting a less strict behaviour for > > rdmsr accesses targeting a MSR not explicitly handled by Xen. Since > > commit 84e848fd7a162f669 accesses to MSRs not explicitly handled by > > Xen result in the injection of a #GP to the guest. This is a behavior > > change since previously a #GP was only injected if accessing the MSR > > on the real hardware will also trigger a #GP. > ... > > I wonder whether we need to to enable this option by default for > > guests being migrated from previous Xen versions? Maybe that's not > > required as the option is helpful mostly for early boot I would > > assume, afterwards an OS should already have the #GP handler setup > > when accessing MSRs. > > I think it's almost as bad to have guests which can be migrated in, > but which then cannot reboot. Ups, yes, right. > Historically we have taken the view that new Xen must support old > guests, even if that means being bug-compatible. So I am strongly in > favour of avoiding such a usability regression. I'm not a xl/libxl expert, but couldn't we set the option in a persistent way for migrated-in guests? IIRC at domain creation libxl knows whether it's a restore or a fresh domain, and hence we could set the option there? The part I'm not sure is about how to make it persistent. Thanks, Roger.