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Bug #13375

closed

bhyve should expose invariant TSC

Added by Patrick Mooney over 1 year ago. Updated over 1 year ago.

Status:
Closed
Priority:
Normal
Category:
bhyve
Start date:
Due date:
% Done:

100%

Estimated time:
Difficulty:
Medium
Tags:
Gerrit CR:

Description

When bhyve was ported to illumos, the logic for exposing the invariant TSC property was skipped. A TSC is considered invariant when its frequency will not be effected by changes in CPU state such as P-state transitions. Presently, illumos has detection logic in the SpeedStep and PowerNow drivers to preclude their use if invariant TSC functionality is not present. Because of that, and because illumos bhyve does not support host suspend/resume, it should be a reasonable assumption that the TSC will run at its measured frequency without interruption. Any skew between CPU TSC values is measure during boot and available to bhyve to configure VMX/SVM TSC offsets so there is no perceived difference in the guest as a vCPU migrates between physical CPUs.

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