linux/drivers/base/cpu.c

// SPDX-License-Identifier: GPL-2.0
/*
 * CPU subsystem support
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/cpu.h>
#include <linux/topology.h>
#include <linux/device.h>
#include <linux/node.h>
#include <linux/gfp.h>
#include <linux/slab.h>
#include <linux/percpu.h>
#include <linux/acpi.h>
#include <linux/of.h>
#include <linux/cpufeature.h>
#include <linux/tick.h>
#include <linux/pm_qos.h>
#include <linux/delay.h>
#include <linux/sched/isolation.h>

#include "base.h"

static DEFINE_PER_CPU(struct device *, cpu_sys_devices);

static int cpu_subsys_match(struct device *dev, struct device_driver *drv)
{
	/* ACPI style match is the only one that may succeed. */
	if (acpi_driver_match_device(dev, drv))
		return 1;

	return 0;
}

#ifdef CONFIG_HOTPLUG_CPU
static void change_cpu_under_node(struct cpu *cpu,
			unsigned int from_nid, unsigned int to_nid)
{
	int cpuid = cpu->dev.id;
	unregister_cpu_under_node(cpuid, from_nid);
	register_cpu_under_node(cpuid, to_nid);
	cpu->node_id = to_nid;
}

static int cpu_subsys_online(struct device *dev)
{
	struct cpu *cpu = container_of(dev, struct cpu, dev);
	int cpuid = dev->id;
	int from_nid, to_nid;
	int ret;
	int retries = 0;

	from_nid = cpu_to_node(cpuid);
	if (from_nid == NUMA_NO_NODE)
		return -ENODEV;

retry:
	ret = cpu_device_up(dev);

	/*
	 * If -EBUSY is returned, it is likely that hotplug is temporarily
	 * disabled when cpu_hotplug_disable() was called. This condition is
	 * transient. So we retry after waiting for an exponentially
	 * increasing delay up to a total of at least 620ms as some PCI
	 * device initialization can take quite a while.
	 */
	if (ret == -EBUSY) {
		retries++;
		if (retries > 5)
			return ret;
		msleep(10 * (1 << retries));
		goto retry;
	}

	/*
	 * When hot adding memory to memoryless node and enabling a cpu
	 * on the node, node number of the cpu may internally change.
	 */
	to_nid = cpu_to_node(cpuid);
	if (from_nid != to_nid)
		change_cpu_under_node(cpu, from_nid, to_nid);

	return ret;
}

static int cpu_subsys_offline(struct device *dev)
{
	return cpu_device_down(dev);
}

void unregister_cpu(struct cpu *cpu)
{
	int logical_cpu = cpu->dev.id;

	unregister_cpu_under_node(logical_cpu, cpu_to_node(logical_cpu));

	device_unregister(&cpu->dev);
	per_cpu(cpu_sys_devices, logical_cpu) = NULL;
	return;
}

#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
static ssize_t cpu_probe_store(struct device *dev,
			       struct device_attribute *attr,
			       const char *buf,
			       size_t count)
{
	ssize_t cnt;
	int ret;

	ret = lock_device_hotplug_sysfs();
	if (ret)
		return ret;

	cnt = arch_cpu_probe(buf, count);

	unlock_device_hotplug();
	return cnt;
}

static ssize_t cpu_release_store(struct device *dev,
				 struct device_attribute *attr,
				 const char *buf,
				 size_t count)
{
	ssize_t cnt;
	int ret;

	ret = lock_device_hotplug_sysfs();
	if (ret)
		return ret;

	cnt = arch_cpu_release(buf, count);

	unlock_device_hotplug();
	return cnt;
}

static DEVICE_ATTR(probe, S_IWUSR, NULL, cpu_probe_store);
static DEVICE_ATTR(release, S_IWUSR, NULL, cpu_release_store);
#endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */
#endif /* CONFIG_HOTPLUG_CPU */

#ifdef CONFIG_KEXEC_CORE
#include <linux/kexec.h>

static ssize_t crash_notes_show(struct device *dev,
				struct device_attribute *attr,
				char *buf)
{
	struct cpu *cpu = container_of(dev, struct cpu, dev);
	unsigned long long addr;
	int cpunum;

	cpunum = cpu->dev.id;

	/*
	 * Might be reading other cpu's data based on which cpu read thread
	 * has been scheduled. But cpu data (memory) is allocated once during
	 * boot up and this data does not change there after. Hence this
	 * operation should be safe. No locking required.
	 */
	addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpunum));

	return sysfs_emit(buf, "%llx\n", addr);
}
static DEVICE_ATTR_ADMIN_RO(crash_notes);

static ssize_t crash_notes_size_show(struct device *dev,
				     struct device_attribute *attr,
				     char *buf)
{
	return sysfs_emit(buf, "%zu\n", sizeof(note_buf_t));
}
static DEVICE_ATTR_ADMIN_RO(crash_notes_size);

static struct attribute *crash_note_cpu_attrs[] = {
	&dev_attr_crash_notes.attr,
	&dev_attr_crash_notes_size.attr,
	NULL
};

static const struct attribute_group crash_note_cpu_attr_group = {
	.attrs = crash_note_cpu_attrs,
};
#endif

static const struct attribute_group *common_cpu_attr_groups[] = {
#ifdef CONFIG_KEXEC_CORE
	&crash_note_cpu_attr_group,
#endif
	NULL
};

static const struct attribute_group *hotplugable_cpu_attr_groups[] = {
#ifdef CONFIG_KEXEC_CORE
	&crash_note_cpu_attr_group,
#endif
	NULL
};

/*
 * Print cpu online, possible, present, and system maps
 */

struct cpu_attr {
	struct device_attribute attr;
	const struct cpumask *const map;
};

static ssize_t show_cpus_attr(struct device *dev,
			      struct device_attribute *attr,
			      char *buf)
{
	struct cpu_attr *ca = container_of(attr, struct cpu_attr, attr);

	return cpumap_print_to_pagebuf(true, buf, ca->map);
}

#define _CPU_ATTR(name, map) \
	{ __ATTR(name, 0444, show_cpus_attr, NULL), map }

/* Keep in sync with cpu_subsys_attrs */
static struct cpu_attr cpu_attrs[] = {
	_CPU_ATTR(online, &__cpu_online_mask),
	_CPU_ATTR(possible, &__cpu_possible_mask),
	_CPU_ATTR(present, &__cpu_present_mask),
};

/*
 * Print values for NR_CPUS and offlined cpus
 */
static ssize_t print_cpus_kernel_max(struct device *dev,
				     struct device_attribute *attr, char *buf)
{
	return sysfs_emit(buf, "%d\n", NR_CPUS - 1);
}
static DEVICE_ATTR(kernel_max, 0444, print_cpus_kernel_max, NULL);

/* arch-optional setting to enable display of offline cpus >= nr_cpu_ids */
unsigned int total_cpus;

static ssize_t print_cpus_offline(struct device *dev,
				  struct device_attribute *attr, char *buf)
{
	int len = 0;
	cpumask_var_t offline;

	/* display offline cpus < nr_cpu_ids */
	if (!alloc_cpumask_var(&offline, GFP_KERNEL))
		return -ENOMEM;
	cpumask_andnot(offline, cpu_possible_mask, cpu_online_mask);
	len += sysfs_emit_at(buf, len, "%*pbl", cpumask_pr_args(offline));
	free_cpumask_var(offline);

	/* display offline cpus >= nr_cpu_ids */
	if (total_cpus && nr_cpu_ids < total_cpus) {
		len += sysfs_emit_at(buf, len, ",");

		if (nr_cpu_ids == total_cpus-1)
			len += sysfs_emit_at(buf, len, "%u", nr_cpu_ids);
		else
			len += sysfs_emit_at(buf, len, "%u-%d",
					     nr_cpu_ids, total_cpus - 1);
	}

	len += sysfs_emit_at(buf, len, "\n");

	return len;
}
static DEVICE_ATTR(offline, 0444, print_cpus_offline, NULL);

static ssize_t print_cpus_isolated(struct device *dev,
				  struct device_attribute *attr, char *buf)
{
	int len;
	cpumask_var_t isolated;

	if (!alloc_cpumask_var(&isolated, GFP_KERNEL))
		return -ENOMEM;

	cpumask_andnot(isolated, cpu_possible_mask,
		       housekeeping_cpumask(HK_TYPE_DOMAIN));
	len = sysfs_emit(buf, "%*pbl\n", cpumask_pr_args(isolated));

	free_cpumask_var(isolated);

	return len;
}
static DEVICE_ATTR(isolated, 0444, print_cpus_isolated, NULL);

#ifdef CONFIG_NO_HZ_FULL
static ssize_t print_cpus_nohz_full(struct device *dev,
				    struct device_attribute *attr, char *buf)
{
	return sysfs_emit(buf, "%*pbl\n", cpumask_pr_args(tick_nohz_full_mask));
}
static DEVICE_ATTR(nohz_full, 0444, print_cpus_nohz_full, NULL);
#endif

#ifdef CONFIG_CRASH_HOTPLUG
static ssize_t crash_hotplug_show(struct device *dev,
				     struct device_attribute *attr,
				     char *buf)
{
	return sysfs_emit(buf, "%d\n", crash_hotplug_cpu_support());
}
static DEVICE_ATTR_ADMIN_RO(crash_hotplug);
#endif

static void cpu_device_release(struct device *dev)
{
	/*
	 * This is an empty function to prevent the driver core from spitting a
	 * warning at us.  Yes, I know this is directly opposite of what the
	 * documentation for the driver core and kobjects say, and the author
	 * of this code has already been publically ridiculed for doing
	 * something as foolish as this.  However, at this point in time, it is
	 * the only way to handle the issue of statically allocated cpu
	 * devices.  The different architectures will have their cpu device
	 * code reworked to properly handle this in the near future, so this
	 * function will then be changed to correctly free up the memory held
	 * by the cpu device.
	 *
	 * Never copy this way of doing things, or you too will be made fun of
	 * on the linux-kernel list, you have been warned.
	 */
}

#ifdef CONFIG_GENERIC_CPU_AUTOPROBE
static ssize_t print_cpu_modalias(struct device *dev,
				  struct device_attribute *attr,
				  char *buf)
{
	int len = 0;
	u32 i;

	len += sysfs_emit_at(buf, len,
			     "cpu:type:" CPU_FEATURE_TYPEFMT ":feature:",
			     CPU_FEATURE_TYPEVAL);

	for (i = 0; i < MAX_CPU_FEATURES; i++)
		if (cpu_have_feature(i)) {
			if (len + sizeof(",XXXX\n") >= PAGE_SIZE) {
				WARN(1, "CPU features overflow page\n");
				break;
			}
			len += sysfs_emit_at(buf, len, ",%04X", i);
		}
	len += sysfs_emit_at(buf, len, "\n");
	return len;
}

static int cpu_uevent(const struct device *dev, struct kobj_uevent_env *env)
{
	char *buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
	if (buf) {
		print_cpu_modalias(NULL, NULL, buf);
		add_uevent_var(env, "MODALIAS=%s", buf);
		kfree(buf);
	}
	return 0;
}
#endif

struct bus_type cpu_subsys = {
	.name = "cpu",
	.dev_name = "cpu",
	.match = cpu_subsys_match,
#ifdef CONFIG_HOTPLUG_CPU
	.online = cpu_subsys_online,
	.offline = cpu_subsys_offline,
#endif
#ifdef CONFIG_GENERIC_CPU_AUTOPROBE
	.uevent = cpu_uevent,
#endif
};
EXPORT_SYMBOL_GPL(cpu_subsys);

/*
 * register_cpu - Setup a sysfs device for a CPU.
 * @cpu - cpu->hotpluggable field set to 1 will generate a control file in
 *	  sysfs for this CPU.
 * @num - CPU number to use when creating the device.
 *
 * Initialize and register the CPU device.
 */
int register_cpu(struct cpu *cpu, int num)
{
	int error;

	cpu->node_id = cpu_to_node(num);
	memset(&cpu->dev, 0x00, sizeof(struct device));
	cpu->dev.id = num;
	cpu->dev.bus = &cpu_subsys;
	cpu->dev.release = cpu_device_release;
	cpu->dev.offline_disabled = !cpu->hotpluggable;
	cpu->dev.offline = !cpu_online(num);
	cpu->dev.of_node = of_get_cpu_node(num, NULL);
	cpu->dev.groups = common_cpu_attr_groups;
	if (cpu->hotpluggable)
		cpu->dev.groups = hotplugable_cpu_attr_groups;
	error = device_register(&cpu->dev);
	if (error) {
		put_device(&cpu->dev);
		return error;
	}

	per_cpu(cpu_sys_devices, num) = &cpu->dev;
	register_cpu_under_node(num, cpu_to_node(num));
	dev_pm_qos_expose_latency_limit(&cpu->dev,
					PM_QOS_RESUME_LATENCY_NO_CONSTRAINT);

	return 0;
}

struct device *get_cpu_device(unsigned int cpu)
{
	if (cpu < nr_cpu_ids && cpu_possible(cpu))
		return per_cpu(cpu_sys_devices, cpu);
	else
		return NULL;
}
EXPORT_SYMBOL_GPL(get_cpu_device);

static void device_create_release(struct device *dev)
{
	kfree(dev);
}

__printf(4, 0)
static struct device *
__cpu_device_create(struct device *parent, void *drvdata,
		    const struct attribute_group **groups,
		    const char *fmt, va_list args)
{
	struct device *dev = NULL;
	int retval = -ENOMEM;

	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
	if (!dev)
		goto error;

	device_initialize(dev);
	dev->parent = parent;
	dev->groups = groups;
	dev->release = device_create_release;
	device_set_pm_not_required(dev);
	dev_set_drvdata(dev, drvdata);

	retval = kobject_set_name_vargs(&dev->kobj, fmt, args);
	if (retval)
		goto error;

	retval = device_add(dev);
	if (retval)
		goto error;

	return dev;

error:
	put_device(dev);
	return ERR_PTR(retval);
}

struct device *cpu_device_create(struct device *parent, void *drvdata,
				 const struct attribute_group **groups,
				 const char *fmt, ...)
{
	va_list vargs;
	struct device *dev;

	va_start(vargs, fmt);
	dev = __cpu_device_create(parent, drvdata, groups, fmt, vargs);
	va_end(vargs);
	return dev;
}
EXPORT_SYMBOL_GPL(cpu_device_create);

#ifdef CONFIG_GENERIC_CPU_AUTOPROBE
static DEVICE_ATTR(modalias, 0444, print_cpu_modalias, NULL);
#endif

static struct attribute *cpu_root_attrs[] = {
#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
	&dev_attr_probe.attr,
	&dev_attr_release.attr,
#endif
	&cpu_attrs[0].attr.attr,
	&cpu_attrs[1].attr.attr,
	&cpu_attrs[2].attr.attr,
	&dev_attr_kernel_max.attr,
	&dev_attr_offline.attr,
	&dev_attr_isolated.attr,
#ifdef CONFIG_NO_HZ_FULL
	&dev_attr_nohz_full.attr,
#endif
#ifdef CONFIG_CRASH_HOTPLUG
	&dev_attr_crash_hotplug.attr,
#endif
#ifdef CONFIG_GENERIC_CPU_AUTOPROBE
	&dev_attr_modalias.attr,
#endif
	NULL
};

static const struct attribute_group cpu_root_attr_group = {
	.attrs = cpu_root_attrs,
};

static const struct attribute_group *cpu_root_attr_groups[] = {
	&cpu_root_attr_group,
	NULL,
};

bool cpu_is_hotpluggable(unsigned int cpu)
{
	struct device *dev = get_cpu_device(cpu);
	return dev && container_of(dev, struct cpu, dev)->hotpluggable
		&& tick_nohz_cpu_hotpluggable(cpu);
}
EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);

#ifdef CONFIG_GENERIC_CPU_DEVICES
DEFINE_PER_CPU(struct cpu, cpu_devices);

bool __weak arch_cpu_is_hotpluggable(int cpu)
{
	return false;
}

int __weak arch_register_cpu(int cpu)
{
	struct cpu *c = &per_cpu(cpu_devices, cpu);

	c->hotpluggable = arch_cpu_is_hotpluggable(cpu);

	return register_cpu(c, cpu);
}

#ifdef CONFIG_HOTPLUG_CPU
void __weak arch_unregister_cpu(int num)
{
	unregister_cpu(&per_cpu(cpu_devices, num));
}
#endif /* CONFIG_HOTPLUG_CPU */
#endif /* CONFIG_GENERIC_CPU_DEVICES */

static void __init cpu_dev_register_generic(void)
{
	int i, ret;

	if (!IS_ENABLED(CONFIG_GENERIC_CPU_DEVICES))
		return;

	for_each_present_cpu(i) {
		ret = arch_register_cpu(i);
		if (ret)
			pr_warn("register_cpu %d failed (%d)\n", i, ret);
	}
}

#ifdef CONFIG_GENERIC_CPU_VULNERABILITIES
static ssize_t cpu_show_not_affected(struct device *dev,
			      struct device_attribute *attr, char *buf)
{
	return sysfs_emit(buf, "Not affected\n");
}

#define CPU_SHOW_VULN_FALLBACK(func)					\
	ssize_t cpu_show_##func(struct device *,			\
				  struct device_attribute *, char *)	\
		 __attribute__((weak, alias("cpu_show_not_affected")))

CPU_SHOW_VULN_FALLBACK(meltdown);
CPU_SHOW_VULN_FALLBACK(spectre_v1);
CPU_SHOW_VULN_FALLBACK(spectre_v2);
CPU_SHOW_VULN_FALLBACK(spec_store_bypass);
CPU_SHOW_VULN_FALLBACK(l1tf);
CPU_SHOW_VULN_FALLBACK(mds);
CPU_SHOW_VULN_FALLBACK(tsx_async_abort);
CPU_SHOW_VULN_FALLBACK(itlb_multihit);
CPU_SHOW_VULN_FALLBACK(srbds);
CPU_SHOW_VULN_FALLBACK(mmio_stale_data);
CPU_SHOW_VULN_FALLBACK(retbleed);
CPU_SHOW_VULN_FALLBACK(spec_rstack_overflow);
CPU_SHOW_VULN_FALLBACK(gds);

static DEVICE_ATTR(meltdown, 0444, cpu_show_meltdown, NULL);
static DEVICE_ATTR(spectre_v1, 0444, cpu_show_spectre_v1, NULL);
static DEVICE_ATTR(spectre_v2, 0444, cpu_show_spectre_v2, NULL);
static DEVICE_ATTR(spec_store_bypass, 0444, cpu_show_spec_store_bypass, NULL);
static DEVICE_ATTR(l1tf, 0444, cpu_show_l1tf, NULL);
static DEVICE_ATTR(mds, 0444, cpu_show_mds, NULL);
static DEVICE_ATTR(tsx_async_abort, 0444, cpu_show_tsx_async_abort, NULL);
static DEVICE_ATTR(itlb_multihit, 0444, cpu_show_itlb_multihit, NULL);
static DEVICE_ATTR(srbds, 0444, cpu_show_srbds, NULL);
static DEVICE_ATTR(mmio_stale_data, 0444, cpu_show_mmio_stale_data, NULL);
static DEVICE_ATTR(retbleed, 0444, cpu_show_retbleed, NULL);
static DEVICE_ATTR(spec_rstack_overflow, 0444, cpu_show_spec_rstack_overflow, NULL);
static DEVICE_ATTR(gather_data_sampling, 0444, cpu_show_gds, NULL);

static struct attribute *cpu_root_vulnerabilities_attrs[] = {
	&dev_attr_meltdown.attr,
	&dev_attr_spectre_v1.attr,
	&dev_attr_spectre_v2.attr,
	&dev_attr_spec_store_bypass.attr,
	&dev_attr_l1tf.attr,
	&dev_attr_mds.attr,
	&dev_attr_tsx_async_abort.attr,
	&dev_attr_itlb_multihit.attr,
	&dev_attr_srbds.attr,
	&dev_attr_mmio_stale_data.attr,
	&dev_attr_retbleed.attr,
	&dev_attr_spec_rstack_overflow.attr,
	&dev_attr_gather_data_sampling.attr,
	NULL
};

static const struct attribute_group cpu_root_vulnerabilities_group = {
	.name  = "vulnerabilities",
	.attrs = cpu_root_vulnerabilities_attrs,
};

static void __init cpu_register_vulnerabilities(void)
{
	struct device *dev = bus_get_dev_root(&cpu_subsys);

	if (dev) {
		if (sysfs_create_group(&dev->kobj, &cpu_root_vulnerabilities_group))
			pr_err("Unable to register CPU vulnerabilities\n");
		put_device(dev);
	}
}

#else
static inline void cpu_register_vulnerabilities(void) { }
#endif

void __init cpu_dev_init(void)
{
	if (subsys_system_register(&cpu_subsys, cpu_root_attr_groups))
		panic("Failed to register CPU subsystem");

	cpu_dev_register_generic();
	cpu_register_vulnerabilities();
}