CPUID Instruction Multi-Level Processor Topology Enumeration
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Solution Overview
Problem
Multi-processor systems face challenges in efficiently enumerating and managing complex multi-level processor topologies, as existing processor identification instructions lack the capability to provide detailed information about various levels of processor grouping, such as SMT and multi-core environments.
Innovation Solution
Modifying the CPUID instruction to include a topological level number, allowing software to enumerate multi-level processor topologies by associating this number with the identification instruction, which returns information about processor identity, level type, mask, and processor count, enabling detailed topology enumeration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If existing processor identification instructions are used, then processor identification is simple, but detailed multi-level topology information cannot be obtained
Solution Approach 1:
The processor topology information is segmented into multiple hierarchical levels (level 0 for logical processors, level 1 for cores, level 2 for processor packages, etc.). Each level can be independently queried using the CPUID instruction with different input values, allowing software to obtain detailed information about each hierarchical level separately rather than requiring a single complex identification mechanism.
Solution Approach 2:
The existing CPUID instruction is enhanced to serve multiple functions: it can still perform traditional processor identification while simultaneously providing multi-level topology information. By adding level number input capability and corresponding output fields (processor count, core count, SMT count) to the existing instruction, the instruction becomes universal and can handle both simple identification and detailed topology enumeration without requiring separate specialized instructions.
2Loss of information
If processor topology enumeration is performed at multiple levels, then comprehensive topology information is obtained, but software complexity increases
Solution Approach 1:
The system performs preliminary organization of processor topology data at the hardware level, with each processor level (logical processors, cores, packages) pre-configured with identification information and hierarchical relationships. When software queries the topology, this pre-organized information is readily available through the CPUID instruction, eliminating the need for software to perform complex analysis or make multiple indirect queries to determine processor relationships.
Solution Approach 2:
The CPUID instruction implements a feedback mechanism where software can input a level number and receive structured topology information in return. The instruction outputs include processor count, core count, and SMT count fields that provide immediate feedback about the processor hierarchy. This allows software to iteratively query different levels and build a complete topology understanding through systematic feedback from the processor itself.
Data Source
AI summary
Embodiments of an invention for using a processor identification instruction to provide multi-level processor topology information are disclosed. In one embodiment, a processor includes decode logic and control logic. The decode logic is to receive an identification instruction having an associated topological level value. The control logic is to provide, in response to the decode logic receiving the identification instruction, processor identification information corresponding to the associated topological level value.