src/x86/topology.c

#include <stdint.h>
#include <stdbool.h>

#include <cpuinfo.h>
#include <cpuinfo/utils.h>
#include <cpuinfo/log.h>
#include <x86/api.h>
#include <x86/cpuid.h>


enum topology_type {
	topology_type_invalid = 0,
	topology_type_smt     = 1,
	topology_type_core    = 2,
};

void cpuinfo_x86_detect_topology(
	uint32_t max_base_index,
	uint32_t max_extended_index,
	struct cpuid_regs leaf1,
	struct cpuinfo_x86_topology* topology)
{
	/*
	 * HTT: indicates multi-core/hyper-threading support on this core.
	 * - Intel, AMD: edx[bit 28] in basic info.
	 */
	const bool htt = !!(leaf1.edx & UINT32_C(0x10000000));

	uint32_t apic_id = 0;
	if (htt) {
		apic_id = leaf1.ebx >> 24;
		bool amd_cmp_legacy = false;
		if (max_extended_index >= UINT32_C(0x80000001)) {
			const struct cpuid_regs leaf0x80000001 = cpuid(UINT32_C(0x80000001));
			/*
			 * CmpLegacy: core multi-processing legacy mode.
			 * - AMD: ecx[bit 1] in extended info (reserved bit on Intel CPUs).
			 */
			amd_cmp_legacy = !!(leaf0x80000001.ecx & UINT32_C(0x00000002));
		}
		if (amd_cmp_legacy) {
			if (max_extended_index >= UINT32_C(0x80000008)) {
				const struct cpuid_regs leaf0x80000008 = cpuid(UINT32_C(0x80000008));
				/*
				 * NC: number of physical cores - 1. The number of cores in the processor is NC+1.
				 * - AMD: ecx[bits 0-7] in leaf 0x80000008 (reserved zero bits on Intel CPUs).
				 */
				const uint32_t cores_per_processor = 1 + (leaf0x80000008.ecx & UINT32_C(0x000000FF));
				topology->core_bits_length = bit_length(cores_per_processor);
				cpuinfo_log_debug("HTT: APIC ID = %08"PRIx32", cores per processor = %"PRIu32, apic_id, cores_per_processor);
			} else {
				/*
				 * LogicalProcessorCount: the number of cores per processor.
				 * - AMD: ebx[bits 16-23] in basic info (different interpretation on Intel CPUs).
				 */
				const uint32_t cores_per_processor = (leaf1.ebx >> 16) & UINT32_C(0x000000FF);
				if (cores_per_processor != 0) {
					topology->core_bits_length = bit_length(cores_per_processor);
				}
				cpuinfo_log_debug("HTT: APIC ID = %08"PRIx32", cores per processor = %"PRIu32, apic_id, cores_per_processor);
			}
		} else {
			/*
			 * Maximum number of addressable IDs for logical processors in this physical package.
			 * - Intel: ebx[bits 16-23] in basic info (different interpretation on AMD CPUs).
			 */
			const uint32_t logical_processors = (leaf1.ebx >> 16) & UINT32_C(0x000000FF);
			if (logical_processors != 0) {
				const uint32_t log2_max_logical_processors = bit_length(logical_processors);
				const uint32_t log2_max_threads_per_core = log2_max_logical_processors - topology->core_bits_length;
				topology->core_bits_offset = log2_max_threads_per_core;
				topology->thread_bits_length = log2_max_threads_per_core;
			}
			cpuinfo_log_debug("HTT: APIC ID = %08"PRIx32", logical processors = %"PRIu32, apic_id, logical_processors);
		}
	}

	/*
	 * x2APIC: indicated support for x2APIC feature.
	 * - Intel: ecx[bit 21] in basic info (reserved bit on AMD CPUs).
	 */
	const bool x2apic = !!(leaf1.ecx & UINT32_C(0x00200000));
	if (x2apic && (max_base_index >= UINT32_C(0xB))) {
		uint32_t level = 0;
		uint32_t type;
		uint32_t total_shift = 0;
		topology->thread_bits_offset = topology->thread_bits_length  = 0;
		topology->core_bits_offset   = topology->core_bits_length = 0;
		do {
			const struct cpuid_regs leafB = cpuidex(UINT32_C(0xB), level);
			type = (leafB.ecx >> 8) & UINT32_C(0x000000FF);
			const uint32_t level_shift = leafB.eax & UINT32_C(0x0000001F);
			const uint32_t x2apic_id   = leafB.edx;
			apic_id = x2apic_id;
			switch (type) {
				case topology_type_invalid:
					break;
				case topology_type_smt:
					cpuinfo_log_debug("x2 level %"PRIu32": APIC ID = %08"PRIx32", "
						"type SMT, shift %"PRIu32", total shift %"PRIu32,
						level, apic_id, level_shift, total_shift);
					topology->thread_bits_offset = total_shift;
					topology->thread_bits_length = level_shift;
					break;
				case topology_type_core:
					cpuinfo_log_debug("x2 level %"PRIu32": APIC ID = %08"PRIx32", "
						"type core, shift %"PRIu32", total shift %"PRIu32,
						level, apic_id, level_shift, total_shift);
					topology->core_bits_offset = total_shift;
					topology->core_bits_length = level_shift;
					break;
				default:
					cpuinfo_log_warning("unexpected topology type %"PRIu32" (offset %"PRIu32", length %"PRIu32") "
						"reported in leaf 0x0000000B is ignored", type, total_shift, level_shift);
					break;
			}
			total_shift += level_shift;
			level += 1;
		} while (type != 0);
		cpuinfo_log_debug("x2APIC ID 0x%08"PRIx32", "
			"SMT offset %"PRIu32" length %"PRIu32", core offset %"PRIu32" length %"PRIu32, apic_id,
			topology->thread_bits_offset, topology->thread_bits_length,
			topology->core_bits_offset, topology->core_bits_length);
	}

	topology->apic_id = apic_id;
}