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To: Paul Durrant , CC: Paul Durrant , Jan Beulich , Ian Jackson , Wei Liu , George Dunlap , Julien Grall , Stefano Stabellini , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= References: <20201008185735.29875-1-paul@xen.org> <20201008185735.29875-7-paul@xen.org> From: Andrew Cooper Message-ID: Date: Mon, 25 Jan 2021 19:24:06 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 In-Reply-To: <20201008185735.29875-7-paul@xen.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Language: en-GB X-ClientProxiedBy: LO4P123CA0252.GBRP123.PROD.OUTLOOK.COM (2603:10a6:600:1a7::23) To BYAPR03MB4728.namprd03.prod.outlook.com (2603:10b6:a03:13a::24) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: e57a8831-d2f0-409b-551b-08d8c166cc03 X-MS-TrafficTypeDiagnostic: BY5PR03MB5126: X-MS-Exchange-Transport-Forked: True X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:10000; 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X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?cm5LOVFlRnpPd1hrM3Y1Qk8wSGZCeXhrdDdnSWo4UnFheUxFeUJLMkxIaTFu?= =?utf-8?B?L095QXI2TUEwdDR0M0FrNUpIVmJCYjV3Mm4xakFab3c2SElFOE40Z3V6SDh5?= =?utf-8?B?a29FQjZHdWt0dmo4alVjQ2FTZnVUUmRzY0VOeFV4UUg3Q2c5OWpMY0tHcCta?= =?utf-8?B?U2h1Ym15bjRLMEdwdlNqdHN0TW9iVEZDUUF1QXA3eWNZMWhhek1qZEFWRW53?= =?utf-8?B?NmxUVENOQlZsMXk0NzU0Y0ZBU3czdG1HOTlmWFNxbnI5azJ5dHp0Z1RPamth?= =?utf-8?B?enBzb3lPbFBTZE13VDdRVW9uU3V1T3VMWjE0QmlLbmRUbzNPTmdpSEtpUEVo?= =?utf-8?B?S2VnV2FaNmI5OXZZUXlHaVZhTDc0SndXSnhnTHdKZjlRd2s1K3NoR0ExUnNI?= =?utf-8?B?YytFNXdUbFc5ckdmZ0Q3MGQyWnJqK3dzKzBCZEQrMUVkcHBYZG5tT3pVYkdn?= =?utf-8?B?R0U3a2JmUlk4czRCZlMrVTFEUitLTGR3ek03aEJ2enJPRW1jdWRDQ1NwYkFk?= =?utf-8?B?YnhHRGZCUmgzZ1lNYk5qNWllTm9PWm1haVo4L3MyZ29GYXVhdkpJUUFtSFhB?= =?utf-8?B?WlB3L1VJa1BKcDRITGhTZVVpY3V1WFpYeEQ4SE5kblFYbkU1TzlOZUl3cnlL?= =?utf-8?B?NzJsKzBCNWoyWkxXNldiQ2VMVStIMGI3YTJ1UVFidGdCQTgwenZ5UCtpdjN6?= =?utf-8?B?M2hMUGRrc2NmT3VZYzJneXcreVFwcGlnTVVyZmlVZkVJZTMvbE9qWkh0UmZT?= =?utf-8?B?UG13cjJ5d2V5L1ZaRmduWmxtR3AwK0FmZEhKV3dwMVY2cS9zMmQ0MjBHc05R?= =?utf-8?B?OUxHekhYNXRoeWI3ZlpHY2RRMkNGcy90bC9WbE5xek1laDYvSWNSdFFvcElM?= =?utf-8?B?MFBacC9WYUdwZVYyVlhsZDJSU08yRlVnL2p5azFBeHdxZjRlTkJhU1pMbVJ0?= =?utf-8?B?RXpOY05ldVh5UGw5alNqY2FjRWhMUmY0OXRPZlRJRElOWTlIa2lzQ1gvdnlD?= =?utf-8?B?VVpPZm53cEVEbTNzeXlleVh3UWpQYmc4UGVBQk5WS1JkeFdQUVN6ZVZlMU9o?= =?utf-8?B?SXJ3N1Y4QmIxNE1qWHlKemFtejd5cmtkYjdadHRVcURYVGFjWEFrR1dhQVBk?= =?utf-8?B?dHY2RWdyek9ram4zRTUzM0pFT01IZU9KWGloZ255VkdDNE9FS0p0eHVzTE44?= =?utf-8?B?QjFCcjlEWS9LVzVTOHZDMDU0TGdDNmZBeTFxT2xZY0dveGtSd0RyQ29KS21i?= =?utf-8?B?T2doZUdUd3NaY0hyTzQxaEZhVXlsTFJ2ZGg1N1NzYXV0YmgvUFpvZ2xlNStt?= =?utf-8?B?NzlBb0FySWpYbUdDdnZxN0d2ckF4TGxQQzJxV1pSK3NVd2tDeUxHNldTWDEx?= =?utf-8?B?VlE1bllyRUFXdG9UUEFCWjdZd3JjenJSa2IzTmNCT2FBckJuVWQrTTBtdXZy?= =?utf-8?B?WmVhYzdoUUgzTThQVEJKeUNxREd1RS9jUEFkdVBBPT0=?= X-MS-Exchange-CrossTenant-Network-Message-Id: e57a8831-d2f0-409b-551b-08d8c166cc03 X-MS-Exchange-CrossTenant-AuthSource: BYAPR03MB4728.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 25 Jan 2021 19:24:12.7659 (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: uvDnaUEFwtHJISafQHcdJaoyiQnMdGGzoKgh7wIrWn5sjsx8Q4sFRiqdHnbKp4MsUbUz46z2zBqlw3FBLm94MHTKkpj/PdYZ2aqPn3LdbZQ= X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR03MB5126 X-OriginatorOrg: citrix.com On 08/10/2020 19:57, Paul Durrant wrote: > +The record body contains the following fields: > + > +| Field | Description | > +|---------------|-----------------------------------------------| > +| `mode` | 0x00000000: Default (emulate if necessary) | > +| | 0x00000001: Always emulate | > +| | 0x00000002: Never emulate | > +| | | > +| `khz` | The TSC frequency in kHz | > +| | | > +| `nsec` | Elapsed time in nanoseconds | > +| | | > +| `incarnation` | Incarnation (counter indicating how many | > +| | times the TSC value has been set) | It is how many set_tsc_info() (hyper)calls have been made, not how many times the guest has written to the TSC MSR. That said, it is totally useless now that PVRDTSCP mode has gone, other than the fact that it appears in guest CPUID as an approximation of "how many times has this domain been migrated". I.e. its a number you'll want to actively squash in your usecase. I'm not sure whether to suggest dropping the field entirely, or not.  I highly doubt any user exists - IIRC, it was specifically for PVRDTSCP userspace to notice that the frequency may have changed, and to re-adjust its calculations. > diff --git a/xen/include/public/save.h b/xen/include/public/save.h > index bccbaadd0b..86881864cf 100644 > --- a/xen/include/public/save.h > +++ b/xen/include/public/save.h > @@ -50,6 +50,7 @@ enum { > DOMAIN_CONTEXT_END, > DOMAIN_CONTEXT_START, > DOMAIN_CONTEXT_SHARED_INFO, > + DOMAIN_CONTEXT_TSC_INFO, At a minimum, this wants an /* x86 only */ comment.  Possibly an X86 infix. ~Andrew