hyperthreading.c

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/* SPDX-License-Identifier: GPL-2.0-only */
 
#include <cpu/intel/common/common.h>
#include <arch/cpu.h>
#include <types.h>
 
bool intel_ht_supported(void)
{
        /* Is HyperThreading supported? */
        return !!(cpuid_edx(1) & CPUID_FEAURE_HTT);
}
 
/*
 * Return true if running thread does not have the smallest lapic ID
 * within a CPU core.
 */
bool intel_ht_sibling(void)
{
        struct cpuid_result result;
        unsigned int core_ids, apic_ids;
        unsigned int max_leaf;
        uint32_t initial_lapicid, threads;
 
        if (!intel_ht_supported())
                return false;
 
        max_leaf = cpuid_get_max_func();
 
        /* Detect from 32-bit X2APIC ID. */
        if (max_leaf >= 0xb) {
                result = cpuid_ext(0xb, 0);
                threads = 1 << (result.eax & 0x1f);
                initial_lapicid = result.edx;
                return initial_lapicid % threads > 0;
        }
 
        /* Detect from 8-bit XAPIC ID. */
        result = cpuid_ext(0x1, 0);
        initial_lapicid = result.ebx >> 24;
        apic_ids = (result.ebx >> 16) & 0xff;
        if (apic_ids == 0)
                apic_ids = 1;
 
        core_ids = 1;
        if (max_leaf >= 4) {
                result = cpuid_ext(4, 0);
                core_ids += (result.eax >> 26) & 0x3f;
        }
 
        threads = (apic_ids / core_ids);
        return initial_lapicid % threads > 0;
}