Hypervisor Timers

The hypervisor provides the following timer services. These services are based on a constant-rate reference time source (typically the ACPI timer on x64 systems).

• A per-partition reference time counter.

• Four synthetic timers per virtual processor. Each synthetic timer is a single-shot or periodic timer that delivers a message when the particular timer expires.

• One virtual APIC timer per virtual processor.

• Two timer assists: an emulated periodic timer assist and a Power Management (PM) timer assist.

• A partition reference time enlightenment that is based on the host platform's support for an Invariant Time Stamp Counter (iTSC).

The following sections describe the hypervisor's timer services:

Reference Time Counter

Synthetic Timers

Periodic Timers

Periodic Timer Assist

PM Timer Assist

Partition Reference Time Enlightenment

Ordering and Messages for Timer Expirations

Reference Counter MSR

Synthetic Timer MSRs

Reference TSC Page

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Build date: 11/16/2013