The HvlGetLpIndexFromApicId function gets the logical processor index for the processor that has the given APIC identifier.


ULONG HvlGetLpIndexFromApicId (ULONG ApicId);


The ApicId argument is the APIC identifier to look up.

Return Value

The function returns a logical processor index if successful, else 0xFFFFFFFF.


The HvlGetLpIndexFromApicId function is exported by name from the kernel in version 6.2 and higher.

Documentation Status

The HvlGetLpIndexFromApicId function is not documented.

Types and names in the declaration above are invented for this note, pending discovery of Microsoft’s.


The function depends on the CPU Management feature of the hypervisor. If this is not enabled, the function fails.

If the function cannot find the given ApicId in its array of logical processor control blocks, it fails. Otherwise, it returns the corresponding logical processor index.