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mx.microsoft.com 1; spf=pass smtp.mailfrom=citrix.com; dmarc=pass action=none header.from=citrix.com; dkim=pass header.d=citrix.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=citrix.onmicrosoft.com; s=selector2-citrix-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=BhXJwv1YbiixRQMPu9WCfwdzGSKbSp4J4vdDjkuUw2E=; b=s2A5ltrzmqa21Sk1B1jS78FDnjkoDc4ZvK5V+Yv60duiQCD1wawEr/svCTaDMTyU5jIyFtoiuWOEgtiJYBrvx9dbl0isHmxNPpnnePfI2gj297ka5HXpvzvUajJw4PMpfkpa4ZxM4rwRRtUFs+VZrrvkN3QZ2eDSWwqQYjL3t1o= To: Jan Beulich CC: Xen-devel , Wei Liu , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= References: <20210504213120.4179-1-andrew.cooper3@citrix.com> <8f6f339b-f025-2cd0-e666-a3083e79af3a@citrix.com> <38f5b74f-b005-784b-a92d-8ddb9e1b8d3c@citrix.com> <8d786331-0d9a-2ec7-0fe5-ba86d4a2547c@citrix.com> From: Andrew Cooper Subject: Re: [PATCH] libx86: Introduce x86_cpu_policy_calculate_compatible() with MSR_ARCH_CAPS handling Message-ID: <03b94402-6233-b6a9-6621-064b5c6bce26@citrix.com> Date: Wed, 5 May 2021 16:18:10 +0100 User-Agent: Mozilla/5.0 (X11; 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X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?QzNiRVBwaHN6ak5zTHF5bVNta1gwTng2WTVVQWZPUVFKYWcxSkQrOXhiSEZo?= =?utf-8?B?TTg5OXZsZnRWY2pGakdzenllY3FZZTJmRHRudHZmMnhuRWJUd2JmNFp1cURi?= =?utf-8?B?Z1czQlgwK1VKUTYvUUxJUktUYml0cXI3cnhOQ29lUHVFdksxYWlGdHUza0Yz?= =?utf-8?B?R2hIT1VMYkpsQnhvRU8ybGd6clBjTG5qelU0aEJqenZxMTgzbTN4Z0FJMkQ0?= =?utf-8?B?S0R4dnN2SGgwQU9sU2ZPUGF2YzFuUldsMkR1MXpsaWZnaDRHbDBFRlBJZjRH?= =?utf-8?B?WTBWQVZLWnVpY3crT0lRYzZCRUx6ZVJ5VkxSSWZoWEtWU0lzN0g0VWw1RWZo?= =?utf-8?B?ejFvczFuK0V6SFMrL3hhQmt6MjRNdyszZ3Q2RFBNOXRuUXZDeFgvUjRHMlFn?= =?utf-8?B?UC8va21uRjNRRDk4Y0hsaXhnMTFCOVQzQm9uTlRoa214MzN0bXR4ei84VmNY?= =?utf-8?B?SFN3M2M3ampZdmw2cXN5VFJtOTJ2TUJOYTFaSFVwSjI0eXJkZ2FOSmVPS21Y?= =?utf-8?B?em1QRWowdFBxQzlyS1NPb1RBcFhhOHhKYWZsNFZKVCtldnBPT2FvSFl2NEdU?= =?utf-8?B?clZRb2h4RzBkREhWNk1neHk0Qkp5L2hTeGU5R2hhTnZNUzNVMFpsUkRwNDFk?= =?utf-8?B?MUx4VkpFZ01LcnFNTUNtQlB0bDg4eEFhNHpEYkw5NHVSYnFWbXhEQ2N4dWNq?= =?utf-8?B?YmV2TDhXSzIremw1c1ZWd1dNd1VkVE5UK2lLNDArNVBIREpWQVA1bFNaU2g5?= =?utf-8?B?TEZqK3ptSGR1WkZNcXdSZkp6UFNRaVdZK1FDdnVDM0N4Y1BMcFpyNW9NcmJM?= =?utf-8?B?ekNaY2NIdWRaVmtjVEoxSzdyODltR29vWlpKUEFhamtQVktOMHA4WFp6cWFu?= =?utf-8?B?aG50SzFtUy9adEVVNUpJWGNNNkVNd3NCd1JOWFQyZXo3dmsvd0k4WURkV1Iy?= =?utf-8?B?QVU0Vm1mUXdTT1ZWN2V3NGpUQ29sU2F2dG9XYjJtTnZFakYzeUlTcGpKTlVs?= =?utf-8?B?SXRFd3JsUEFSeGdEVk5NMnJSSFdUN2cwc3dtSHNja3dOVXgxUmdSbGY5S0lT?= =?utf-8?B?WEFMK2JIYjNybGowUHRaVVg1bDVVUGVMa2pPTHRENEpxNmN2QWdSSC9LYUx5?= =?utf-8?B?SUlrbnE1K0o4Y2hoK2dGT2NMUHRjUFhBRmN3VStFRTVnMENuTGh0UzNTdlNY?= =?utf-8?B?SFJRRU5Ta3l1WEoxK2wwcmg4L0hwWWZtNFNSbWUrZnpsdklhZEpHL2l6ZUp6?= =?utf-8?B?NW1VNEk4aDVaZ2F3bytJNkVYL2Y4QTh4MXZuN3BhdW9yU1poN2UyMzdEQnpr?= =?utf-8?B?WDRuZkdZVERvdk5rMTlGdHJSczFGV2NVOUdPL21yNzlYRHFQb21zMWpvaGtC?= =?utf-8?B?U24xa0dkT1FKY05BZkgrWm52eTRUK3ltaUlsYWFGcXE0Q3lxSXo0TFVzZnAx?= =?utf-8?B?VEFIOVFqYXdtdTBZOWUzYkJUdWJKZEdveE9lcjhJRFhZUWlqalR2RFhRZ095?= =?utf-8?B?T1FWNTgyNjIwWHJ3SFBCZXNZdWcvOFVublozaDhwOEpIMFdyK3ZzTE1teElp?= =?utf-8?B?K1pMcjYzQVdtUTZJdzA3cEVoU3RXT3pzTzZtTldWKy83NnI5MUVKbEJpTGlD?= =?utf-8?B?QnMwUnhLdndxVENFaElUbVdNMTlhVVZQbm82RkFKV3YyRHZKNEdxQzlzM0FZ?= =?utf-8?B?UkdybS9lNHBjQnFoOUVSV2xnWGpHaDRjd24wWkN0K3lTYUl5N0hxWW0rZkUx?= =?utf-8?Q?Vz+rqBkjx+PnD90D5L3iK3EchA/EIrjJ4oFO3V0?= X-MS-Exchange-CrossTenant-Network-Message-Id: 69bdbe19-659d-4081-f29a-08d90fd901e8 X-MS-Exchange-CrossTenant-AuthSource: BYAPR03MB3623.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 May 2021 15:18:16.5648 (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: QIHHWISrSMhSQsOVY5ikojtEF662ndgqHeVPFWsDcqoGTYcA1egR3jfShACjy2eH+u8HjVDeeIYWW8iWLUB12BgE+pmx/Y4cFrusPQah4uU= X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR03MB3495 X-OriginatorOrg: citrix.com On 05/05/2021 16:00, Jan Beulich wrote: > On 05.05.2021 16:50, Andrew Cooper wrote: >> On 05/05/2021 15:48, Jan Beulich wrote: >>> On 05.05.2021 16:29, Andrew Cooper wrote: >>>> Technically, MCXSR_MASK is also a hard blocker to migration, but we >>>> don't even have that data in a consumable form, and we just might be >>>> extremely lucky and discover that it is restricted to non-64-bit CPUs. >>> "it" being what here? The value's presence / absence in an {F,}XSAVE >>> image? Or the precise value of it? >> The precise value of it. > Not sure whether DAZ is new enough, but relatively sure MM isn't. > >> =C2=A0 Migrating across the boundary where the >> default changed will cause {F,}RSTOR instructions to #GP. > That's understood. Is there actually anything standing in the way > of treating MXCSR_MASK like yet another feature flag group? Well - we'd need to find somewhere to put it.=C2=A0 It doesn't fit in architectural CPUID or MSR information. We could add a 3rd category of information in "a cpu policy", and that is always an option. However, this issue hasn't been a problem so far, is only for very legacy CPUs at this point, and isn't high on my list of worries. ~Andrew