PM Timer Assist

The parent partition can request the hypervisor to assist the child partition's use of the ACPI Power Management (PM) timer. The parent specifies an I/O port and whether the child's ACPI PM timer is 24 or 32 bits wide. When the child partition performs an input operation from the specified port, the hypervisor will directly provide the value of the PM timer that is based on the partition's reference time. The returned ACPI PM timer value is computed as shown in the following calculation:

ACPI_PM_Timer = Modulus(Partition_Reference_Time * 0.3579545, 2**[24|32]);

This assist supports only input operations on the I/O port. Attempts to either output to the port or input from any of the three subsequent I/O ports (that is, ports n+1, n+2 or n+3) will follow the rules for I/O port accesses as described in I/O Port Accesses.

If both an intercept and the PM timer assist are installed for the same I/O port, the intercept will take precedence over the assist.

The caller specifies the PM timer property's port and whether the value returned is 24 or 32 bits wide by setting the members of a HV_PM_TIMER_INFO union.

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Build date: 11/16/2013