Linux 内核中关于 CPU 编号和拓扑管理

CPU 拓扑结构定义

// topology.h
struct cpu_topology {int thread_id;    // SMT IDint core_id;      // 核心 IDint package_id;   // 物理 CPU IDint die_id;       // Die IDcpumask_t thread_sibling; // SMT 线程掩码cpumask_t core_sibling;   // 核心掩码
};

CPU 在线/离线管理

//cpu.c
/* CPU 热插拔核心函数 */
int cpu_up(unsigned int cpu)
{int err = 0;struct device *dev;struct device *parent;if (!cpu_possible(cpu)) {pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",cpu);return -EINVAL;}dev = get_cpu_device(cpu);if (!dev) {pr_err("can't online cpu %d as device does not exist\n", cpu);return -ENODEV;}/* 确保 CPU 已经完全离线 */cpu_maps_update_begin();if (cpu_online(cpu)) {err = -EEXIST;goto out;}/* 执行架构相关的 CPU 上线操作 */err = _cpu_up(cpu, 0, CPUHP_ONLINE);out:cpu_maps_update_done();return err;
}
EXPORT_SYMBOL_GPL(cpu_up);

CPU 设备注册

// cpu.c
static struct bus_type cpu_subsys = {.name = "cpu",.dev_name = "cpu",
};static int __init cpu_dev_init(void)
{int err;err = subsys_system_register(&cpu_subsys, cpu_root_attr_groups);if (err)return err;/* 创建 /sys/devices/system/cpu 目录 */cpu_dev_root = kzalloc(sizeof(*cpu_dev_root), GFP_KERNEL);if (!cpu_dev_root)return -ENOMEM;/* 注册每个 CPU 的 sysfs 接口 */for_each_possible_cpu(cpu) {struct device *dev;dev = get_cpu_device(cpu);if (dev) {err = device_register(dev);if (err)return err;}}return 0;
}

CPU 掩码管理

//cpumask.c
/* CPU 掩码操作函数 */
void cpumask_set_cpu(unsigned int cpu, struct cpumask *dstp)
{set_bit(cpu, cpumask_bits(dstp));
}void cpumask_clear_cpu(unsigned int cpu, struct cpumask *dstp)
{clear_bit(cpu, cpumask_bits(dstp));
}int cpumask_test_cpu(int cpu, const struct cpumask *cpumask)
{return test_bit(cpu, cpumask_bits((struct cpumask *)cpumask));
}

CPU 拓扑信息初始化

//tepology.c
/* 初始化 CPU 拓扑信息 */
void detect_extended_topology(struct cpuinfo_x86 *c)
{unsigned int eax, ebx, ecx, edx;if (c->extended_cpuid_level < 0xb)return;cpuid_count(0xb, 0, &eax, &ebx, &ecx, &edx);/* 如果 CPUID.0BH 不支持，返回 */if (ebx == 0 || (ecx & 0xff00) == 0)return;/* 解析 SMT 级别 */c->x86_max_cores = (ecx & 0xff00) >> 8;c->cpu_core_id = edx;/* 解析 Core 级别 */cpuid_count(0xb, 1, &eax, &ebx, &ecx, &edx);if ((ecx & 0xff00) != 0) {c->x86_max_cores = c->x86_max_cores / ((ecx & 0xff00) >> 8);c->phys_proc_id = edx;}
}

sysfs CPU 接口

//cpu.c
/* CPU 设备属性 */
static DEVICE_ATTR(online, 0644, show_online, store_online);
static DEVICE_ATTR(offline, 0444, show_offline, NULL);
static DEVICE_ATTR(possible, 0444, show_possible, NULL);
static DEVICE_ATTR(present, 0444, show_present, NULL);/* CPU 在线状态控制 */
static ssize_t store_online(struct device *dev,struct device_attribute *attr,const char *buf, size_t count)
{struct cpu *cpu = container_of(dev, struct cpu, dev);int ret;switch (buf[0]) {case '0':ret = cpu_down(cpu->dev.id);break;case '1':ret = cpu_up(cpu->dev.id);break;default:ret = -EINVAL;}return ret ? ret : count;
}

CPU 热插拔状态机

//cpu.c
/* CPU 热插拔状态定义 */
enum cpuhp_state {CPUHP_OFFLINE = 0,CPUHP_CREATE_THREADS,CPUHP_PERF_PREPARE,CPUHP_WORKQUEUE_PREP,/* ... 更多状态 ... */CPUHP_ONLINE,
};/* CPU 热插拔回调注册 */
int __cpuhp_setup_state(enum cpuhp_state state,const char *name,bool invoke,int (*startup)(unsigned int cpu),int (*teardown)(unsigned int cpu),bool multi_instance)
{int ret = 0;/* ... 实现代码 ... */return ret;
}';