src/x86/topology.c

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

#include <cpuinfo.h>
#include <cpuinfo/log.h>
#include <cpuinfo/utils.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;
}