class ApicIdDecoder

ApicIdDecoder is a utility for extracting particular topological level

IDs from an (x2)APIC ID.

In full generality, an APIC ID might decompose as follows:

[intel/vol3]: Figure 8-5. Generalized Seven Level Interpretation of the APIC ID.

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| CLUSTER ID | PACKAGE ID | DIE ID | TILE ID | MODULE ID | CORE ID | SMT ID |

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where the full ID width is 32-bit (if x2APIC) or 8-bit.

This, however, is higher fidelity than we are able to make use of. Since

CLUSTER ID and PACKAGE_ID are not directly enumerable from CPUID, we elide

the two IDs into a single PACKAGE ID, defined as the rest of the ID above

DIE. Moreover, the system currently has no use for enumerating tiles and

modules directly (which is also a practice that AMD does not do): we elide

the TILE and MODULE IDs into DIE ID alone. Accordingly, ApicIdDecoder

partitions up the APIC address space as

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| PACKAGE ID | DIE ID | CORE ID | SMT ID |

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