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Feature #13963

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Add support for obtaining TSC frequency from VMWare

Added by Jason King 8 days ago.

Status:
New
Priority:
Normal
Assignee:
Category:
kernel
Start date:
Due date:
% Done:

0%

Estimated time:
Difficulty:
Medium
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Gerrit CR:

Description

When running as a VMWare guest, if CPUID leaf 0x40000010 exists, it provides:

EAX: TSC frequency (in kHz)
EBX: APIC frequency (in kHz)

Additionally, there is also a VMWare call VMWARE_HVCMD_GETTSCFREQ that returns the TSC frequency as a 64-bit int (split into two 32-bit values) for older VMWare versions.

See: https://lwn.net/Articles/301888/ and https://github.com/freebsd/freebsd-src/blob/main/sys/x86/x86/tsc.c#L121-L135

We should support using these mechanisms for setting the TSC frequency (when present)

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