src/cpu/intel/common/hyperthreading.c

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2
   3 #include <cpu/cpu.h>
   4 #include <cpu/intel/common/common.h>
   5 #include <types.h>
   6
   7 bool intel_ht_supported(void)
   8 {
   9         /* Is HyperThreading supported? */
  10         return !!(cpuid_edx(1) & CPUID_FEATURE_HTT);
  11 }
  12
  13 /*
  14  * Return true if running thread does not have the smallest lapic ID
  15  * within a CPU core.
  16  */
  17 bool intel_ht_sibling(void)
  18 {
  19         struct cpuid_result result;
  20         unsigned int core_ids, apic_ids;
  21         unsigned int max_leaf;
  22         uint32_t initial_lapicid, threads;
  23
  24         if (!intel_ht_supported())
  25                 return false;
  26
  27         max_leaf = cpuid_get_max_func();
  28
  29         /* Detect from 32-bit X2APIC ID. */
  30         if (max_leaf >= 0xb) {
  31                 result = cpuid_ext(0xb, 0);
  32                 threads = 1 << (result.eax & 0x1f);
  33                 initial_lapicid = result.edx;
  34                 return initial_lapicid % threads > 0;
  35         }
  36
  37         /* Detect from 8-bit XAPIC ID. */
  38         result = cpuid_ext(0x1, 0);
  39         initial_lapicid = result.ebx >> 24;
  40         apic_ids = (result.ebx >> 16) & 0xff;
  41         if (apic_ids == 0)
  42                 apic_ids = 1;
  43
  44         core_ids = 1;
  45         if (max_leaf >= 4) {
  46                 result = cpuid_ext(4, 0);
  47                 core_ids += (result.eax >> 26) & 0x3f;
  48         }
  49
  50         threads = (apic_ids / core_ids);
  51         return initial_lapicid % threads > 0;
  52 }