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/* SPDX-License-Identifier: GPL-2.0-only */
#include <console/console.h>
#include <cpu/intel/hyperthreading.h>
#include <device/device.h>
#include <option.h>
#include <smp/spinlock.h>
#if CONFIG(PARALLEL_CPU_INIT)
#error Intel hyper-threading requires serialized CPU init
#endif
static int first_time = 1;
static int disable_siblings = !CONFIG(LOGICAL_CPUS);
void intel_sibling_init(struct device *cpu)
{
unsigned int i, siblings;
struct cpuid_result result;
/* On the bootstrap processor see if I want sibling cpus enabled */
if (first_time) {
first_time = 0;
get_option(&disable_siblings, "hyper_threading");
}
result = cpuid(1);
/* Is hyperthreading supported */
if (!(result.edx & (1 << 28)))
return;
/* See how many sibling cpus we have */
siblings = (result.ebx >> 16) & 0xff;
if (siblings < 1)
siblings = 1;
printk(BIOS_DEBUG, "CPU: %u %d siblings\n",
cpu->path.apic.apic_id,
siblings);
/* See if I am a sibling cpu */
if (cpu->path.apic.apic_id & (siblings - 1)) {
if (disable_siblings)
cpu->enabled = 0;
return;
}
/* I am the primary CPU start up my siblings */
for (i = 1; i < siblings; i++) {
struct device_path cpu_path;
struct device *new;
/* Build the CPU device path */
cpu_path.type = DEVICE_PATH_APIC;
cpu_path.apic.apic_id = cpu->path.apic.apic_id + i;
/* Allocate new CPU device structure iff sibling CPU
* was not in static device tree.
*/
new = alloc_find_dev(cpu->bus, &cpu_path);
if (!new)
continue;
printk(BIOS_DEBUG, "CPU: %u has sibling %u\n",
cpu->path.apic.apic_id,
new->path.apic.apic_id);
}
}
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