drivers/base/cpu.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * CPU subsystem support
   4  */
   5
   6 #include <linux/kernel.h>
   7 #include <linux/module.h>
   8 #include <linux/init.h>
   9 #include <linux/sched.h>
  10 #include <linux/cpu.h>
  11 #include <linux/topology.h>
  12 #include <linux/device.h>
  13 #include <linux/node.h>
  14 #include <linux/gfp.h>
  15 #include <linux/slab.h>
  16 #include <linux/percpu.h>
  17 #include <linux/acpi.h>
  18 #include <linux/of.h>
  19 #include <linux/cpufeature.h>
  20 #include <linux/tick.h>
  21 #include <linux/pm_qos.h>
  22 #include <linux/delay.h>
  23 #include <linux/sched/isolation.h>
  24
  25 #include "base.h"
  26
  27 static DEFINE_PER_CPU(struct device *, cpu_sys_devices);
  28
  29 static int cpu_subsys_match(struct device *dev, struct device_driver *drv)
  30 {
  31         /* ACPI style match is the only one that may succeed. */
  32         if (acpi_driver_match_device(dev, drv))
  33                 return 1;
  34
  35         return 0;
  36 }
  37
  38 #ifdef CONFIG_HOTPLUG_CPU
  39 static void change_cpu_under_node(struct cpu *cpu,
  40                         unsigned int from_nid, unsigned int to_nid)
  41 {
  42         int cpuid = cpu->dev.id;
  43         unregister_cpu_under_node(cpuid, from_nid);
  44         register_cpu_under_node(cpuid, to_nid);
  45         cpu->node_id = to_nid;
  46 }
  47
  48 static int cpu_subsys_online(struct device *dev)
  49 {
  50         struct cpu *cpu = container_of(dev, struct cpu, dev);
  51         int cpuid = dev->id;
  52         int from_nid, to_nid;
  53         int ret;
  54         int retries = 0;
  55
  56         from_nid = cpu_to_node(cpuid);
  57         if (from_nid == NUMA_NO_NODE)
  58                 return -ENODEV;
  59
  60 retry:
  61         ret = cpu_device_up(dev);
  62
  63         /*
  64          * If -EBUSY is returned, it is likely that hotplug is temporarily
  65          * disabled when cpu_hotplug_disable() was called. This condition is
  66          * transient. So we retry after waiting for an exponentially
  67          * increasing delay up to a total of at least 620ms as some PCI
  68          * device initialization can take quite a while.
  69          */
  70         if (ret == -EBUSY) {
  71                 retries++;
  72                 if (retries > 5)
  73                         return ret;
  74                 msleep(10 * (1 << retries));
  75                 goto retry;
  76         }
  77
  78         /*
  79          * When hot adding memory to memoryless node and enabling a cpu
  80          * on the node, node number of the cpu may internally change.
  81          */
  82         to_nid = cpu_to_node(cpuid);
  83         if (from_nid != to_nid)
  84                 change_cpu_under_node(cpu, from_nid, to_nid);
  85
  86         return ret;
  87 }
  88
  89 static int cpu_subsys_offline(struct device *dev)
  90 {
  91         return cpu_device_down(dev);
  92 }
  93
  94 void unregister_cpu(struct cpu *cpu)
  95 {
  96         int logical_cpu = cpu->dev.id;
  97
  98         unregister_cpu_under_node(logical_cpu, cpu_to_node(logical_cpu));
  99
 100         device_unregister(&cpu->dev);
 101         per_cpu(cpu_sys_devices, logical_cpu) = NULL;
 102         return;
 103 }
 104
 105 #ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
 106 static ssize_t cpu_probe_store(struct device *dev,
 107                                struct device_attribute *attr,
 108                                const char *buf,
 109                                size_t count)
 110 {
 111         ssize_t cnt;
 112         int ret;
 113
 114         ret = lock_device_hotplug_sysfs();
 115         if (ret)
 116                 return ret;
 117
 118         cnt = arch_cpu_probe(buf, count);
 119
 120         unlock_device_hotplug();
 121         return cnt;
 122 }
 123
 124 static ssize_t cpu_release_store(struct device *dev,
 125                                  struct device_attribute *attr,
 126                                  const char *buf,
 127                                  size_t count)
 128 {
 129         ssize_t cnt;
 130         int ret;
 131
 132         ret = lock_device_hotplug_sysfs();
 133         if (ret)
 134                 return ret;
 135
 136         cnt = arch_cpu_release(buf, count);
 137
 138         unlock_device_hotplug();
 139         return cnt;
 140 }
 141
 142 static DEVICE_ATTR(probe, S_IWUSR, NULL, cpu_probe_store);
 143 static DEVICE_ATTR(release, S_IWUSR, NULL, cpu_release_store);
 144 #endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */
 145 #endif /* CONFIG_HOTPLUG_CPU */
 146
 147 #ifdef CONFIG_KEXEC
 148 #include <linux/kexec.h>
 149
 150 static ssize_t crash_notes_show(struct device *dev,
 151                                 struct device_attribute *attr,
 152                                 char *buf)
 153 {
 154         struct cpu *cpu = container_of(dev, struct cpu, dev);
 155         unsigned long long addr;
 156         int cpunum;
 157
 158         cpunum = cpu->dev.id;
 159
 160         /*
 161          * Might be reading other cpu's data based on which cpu read thread
 162          * has been scheduled. But cpu data (memory) is allocated once during
 163          * boot up and this data does not change there after. Hence this
 164          * operation should be safe. No locking required.
 165          */
 166         addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpunum));
 167
 168         return sysfs_emit(buf, "%llx\n", addr);
 169 }
 170 static DEVICE_ATTR_ADMIN_RO(crash_notes);
 171
 172 static ssize_t crash_notes_size_show(struct device *dev,
 173                                      struct device_attribute *attr,
 174                                      char *buf)
 175 {
 176         return sysfs_emit(buf, "%zu\n", sizeof(note_buf_t));
 177 }
 178 static DEVICE_ATTR_ADMIN_RO(crash_notes_size);
 179
 180 static struct attribute *crash_note_cpu_attrs[] = {
 181         &dev_attr_crash_notes.attr,
 182         &dev_attr_crash_notes_size.attr,
 183         NULL
 184 };
 185
 186 static const struct attribute_group crash_note_cpu_attr_group = {
 187         .attrs = crash_note_cpu_attrs,
 188 };
 189 #endif
 190
 191 static const struct attribute_group *common_cpu_attr_groups[] = {
 192 #ifdef CONFIG_KEXEC
 193         &crash_note_cpu_attr_group,
 194 #endif
 195         NULL
 196 };
 197
 198 static const struct attribute_group *hotplugable_cpu_attr_groups[] = {
 199 #ifdef CONFIG_KEXEC
 200         &crash_note_cpu_attr_group,
 201 #endif
 202         NULL
 203 };
 204
 205 /*
 206  * Print cpu online, possible, present, and system maps
 207  */
 208
 209 struct cpu_attr {
 210         struct device_attribute attr;
 211         const struct cpumask *const map;
 212 };
 213
 214 static ssize_t show_cpus_attr(struct device *dev,
 215                               struct device_attribute *attr,
 216                               char *buf)
 217 {
 218         struct cpu_attr *ca = container_of(attr, struct cpu_attr, attr);
 219
 220         return cpumap_print_to_pagebuf(true, buf, ca->map);
 221 }
 222
 223 #define _CPU_ATTR(name, map) \
 224         { __ATTR(name, 0444, show_cpus_attr, NULL), map }
 225
 226 /* Keep in sync with cpu_subsys_attrs */
 227 static struct cpu_attr cpu_attrs[] = {
 228         _CPU_ATTR(online, &__cpu_online_mask),
 229         _CPU_ATTR(possible, &__cpu_possible_mask),
 230         _CPU_ATTR(present, &__cpu_present_mask),
 231 };
 232
 233 /*
 234  * Print values for NR_CPUS and offlined cpus
 235  */
 236 static ssize_t print_cpus_kernel_max(struct device *dev,
 237                                      struct device_attribute *attr, char *buf)
 238 {
 239         return sysfs_emit(buf, "%d\n", NR_CPUS - 1);
 240 }
 241 static DEVICE_ATTR(kernel_max, 0444, print_cpus_kernel_max, NULL);
 242
 243 /* arch-optional setting to enable display of offline cpus >= nr_cpu_ids */
 244 unsigned int total_cpus;
 245
 246 static ssize_t print_cpus_offline(struct device *dev,
 247                                   struct device_attribute *attr, char *buf)
 248 {
 249         int len = 0;
 250         cpumask_var_t offline;
 251
 252         /* display offline cpus < nr_cpu_ids */
 253         if (!alloc_cpumask_var(&offline, GFP_KERNEL))
 254                 return -ENOMEM;
 255         cpumask_andnot(offline, cpu_possible_mask, cpu_online_mask);
 256         len += sysfs_emit_at(buf, len, "%*pbl", cpumask_pr_args(offline));
 257         free_cpumask_var(offline);
 258
 259         /* display offline cpus >= nr_cpu_ids */
 260         if (total_cpus && nr_cpu_ids < total_cpus) {
 261                 len += sysfs_emit_at(buf, len, ",");
 262
 263                 if (nr_cpu_ids == total_cpus-1)
 264                         len += sysfs_emit_at(buf, len, "%u", nr_cpu_ids);
 265                 else
 266                         len += sysfs_emit_at(buf, len, "%u-%d",
 267                                              nr_cpu_ids, total_cpus - 1);
 268         }
 269
 270         len += sysfs_emit_at(buf, len, "\n");
 271
 272         return len;
 273 }
 274 static DEVICE_ATTR(offline, 0444, print_cpus_offline, NULL);
 275
 276 static ssize_t print_cpus_isolated(struct device *dev,
 277                                   struct device_attribute *attr, char *buf)
 278 {
 279         int len;
 280         cpumask_var_t isolated;
 281
 282         if (!alloc_cpumask_var(&isolated, GFP_KERNEL))
 283                 return -ENOMEM;
 284
 285         cpumask_andnot(isolated, cpu_possible_mask,
 286                        housekeeping_cpumask(HK_TYPE_DOMAIN));
 287         len = sysfs_emit(buf, "%*pbl\n", cpumask_pr_args(isolated));
 288
 289         free_cpumask_var(isolated);
 290
 291         return len;
 292 }
 293 static DEVICE_ATTR(isolated, 0444, print_cpus_isolated, NULL);
 294
 295 #ifdef CONFIG_NO_HZ_FULL
 296 static ssize_t print_cpus_nohz_full(struct device *dev,
 297                                     struct device_attribute *attr, char *buf)
 298 {
 299         return sysfs_emit(buf, "%*pbl\n", cpumask_pr_args(tick_nohz_full_mask));
 300 }
 301 static DEVICE_ATTR(nohz_full, 0444, print_cpus_nohz_full, NULL);
 302 #endif
 303
 304 #ifdef CONFIG_CRASH_HOTPLUG
 305 static ssize_t crash_hotplug_show(struct device *dev,
 306                                      struct device_attribute *attr,
 307                                      char *buf)
 308 {
 309         return sysfs_emit(buf, "%d\n", crash_hotplug_cpu_support());
 310 }
 311 static DEVICE_ATTR_ADMIN_RO(crash_hotplug);
 312 #endif
 313
 314 static void cpu_device_release(struct device *dev)
 315 {
 316         /*
 317          * This is an empty function to prevent the driver core from spitting a
 318          * warning at us.  Yes, I know this is directly opposite of what the
 319          * documentation for the driver core and kobjects say, and the author
 320          * of this code has already been publically ridiculed for doing
 321          * something as foolish as this.  However, at this point in time, it is
 322          * the only way to handle the issue of statically allocated cpu
 323          * devices.  The different architectures will have their cpu device
 324          * code reworked to properly handle this in the near future, so this
 325          * function will then be changed to correctly free up the memory held
 326          * by the cpu device.
 327          *
 328          * Never copy this way of doing things, or you too will be made fun of
 329          * on the linux-kernel list, you have been warned.
 330          */
 331 }
 332
 333 #ifdef CONFIG_GENERIC_CPU_AUTOPROBE
 334 static ssize_t print_cpu_modalias(struct device *dev,
 335                                   struct device_attribute *attr,
 336                                   char *buf)
 337 {
 338         int len = 0;
 339         u32 i;
 340
 341         len += sysfs_emit_at(buf, len,
 342                              "cpu:type:" CPU_FEATURE_TYPEFMT ":feature:",
 343                              CPU_FEATURE_TYPEVAL);
 344
 345         for (i = 0; i < MAX_CPU_FEATURES; i++)
 346                 if (cpu_have_feature(i)) {
 347                         if (len + sizeof(",XXXX\n") >= PAGE_SIZE) {
 348                                 WARN(1, "CPU features overflow page\n");
 349                                 break;
 350                         }
 351                         len += sysfs_emit_at(buf, len, ",%04X", i);
 352                 }
 353         len += sysfs_emit_at(buf, len, "\n");
 354         return len;
 355 }
 356
 357 static int cpu_uevent(const struct device *dev, struct kobj_uevent_env *env)
 358 {
 359         char *buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
 360         if (buf) {
 361                 print_cpu_modalias(NULL, NULL, buf);
 362                 add_uevent_var(env, "MODALIAS=%s", buf);
 363                 kfree(buf);
 364         }
 365         return 0;
 366 }
 367 #endif
 368
 369 struct bus_type cpu_subsys = {
 370         .name = "cpu",
 371         .dev_name = "cpu",
 372         .match = cpu_subsys_match,
 373 #ifdef CONFIG_HOTPLUG_CPU
 374         .online = cpu_subsys_online,
 375         .offline = cpu_subsys_offline,
 376 #endif
 377 #ifdef CONFIG_GENERIC_CPU_AUTOPROBE
 378         .uevent = cpu_uevent,
 379 #endif
 380 };
 381 EXPORT_SYMBOL_GPL(cpu_subsys);
 382
 383 /*
 384  * register_cpu - Setup a sysfs device for a CPU.
 385  * @cpu - cpu->hotpluggable field set to 1 will generate a control file in
 386  *        sysfs for this CPU.
 387  * @num - CPU number to use when creating the device.
 388  *
 389  * Initialize and register the CPU device.
 390  */
 391 int register_cpu(struct cpu *cpu, int num)
 392 {
 393         int error;
 394
 395         cpu->node_id = cpu_to_node(num);
 396         memset(&cpu->dev, 0x00, sizeof(struct device));
 397         cpu->dev.id = num;
 398         cpu->dev.bus = &cpu_subsys;
 399         cpu->dev.release = cpu_device_release;
 400         cpu->dev.offline_disabled = !cpu->hotpluggable;
 401         cpu->dev.offline = !cpu_online(num);
 402         cpu->dev.of_node = of_get_cpu_node(num, NULL);
 403         cpu->dev.groups = common_cpu_attr_groups;
 404         if (cpu->hotpluggable)
 405                 cpu->dev.groups = hotplugable_cpu_attr_groups;
 406         error = device_register(&cpu->dev);
 407         if (error) {
 408                 put_device(&cpu->dev);
 409                 return error;
 410         }
 411
 412         per_cpu(cpu_sys_devices, num) = &cpu->dev;
 413         register_cpu_under_node(num, cpu_to_node(num));
 414         dev_pm_qos_expose_latency_limit(&cpu->dev,
 415                                         PM_QOS_RESUME_LATENCY_NO_CONSTRAINT);
 416
 417         return 0;
 418 }
 419
 420 struct device *get_cpu_device(unsigned int cpu)
 421 {
 422         if (cpu < nr_cpu_ids && cpu_possible(cpu))
 423                 return per_cpu(cpu_sys_devices, cpu);
 424         else
 425                 return NULL;
 426 }
 427 EXPORT_SYMBOL_GPL(get_cpu_device);
 428
 429 static void device_create_release(struct device *dev)
 430 {
 431         kfree(dev);
 432 }
 433
 434 __printf(4, 0)
 435 static struct device *
 436 __cpu_device_create(struct device *parent, void *drvdata,
 437                     const struct attribute_group **groups,
 438                     const char *fmt, va_list args)
 439 {
 440         struct device *dev = NULL;
 441         int retval = -ENOMEM;
 442
 443         dev = kzalloc(sizeof(*dev), GFP_KERNEL);
 444         if (!dev)
 445                 goto error;
 446
 447         device_initialize(dev);
 448         dev->parent = parent;
 449         dev->groups = groups;
 450         dev->release = device_create_release;
 451         device_set_pm_not_required(dev);
 452         dev_set_drvdata(dev, drvdata);
 453
 454         retval = kobject_set_name_vargs(&dev->kobj, fmt, args);
 455         if (retval)
 456                 goto error;
 457
 458         retval = device_add(dev);
 459         if (retval)
 460                 goto error;
 461
 462         return dev;
 463
 464 error:
 465         put_device(dev);
 466         return ERR_PTR(retval);
 467 }
 468
 469 struct device *cpu_device_create(struct device *parent, void *drvdata,
 470                                  const struct attribute_group **groups,
 471                                  const char *fmt, ...)
 472 {
 473         va_list vargs;
 474         struct device *dev;
 475
 476         va_start(vargs, fmt);
 477         dev = __cpu_device_create(parent, drvdata, groups, fmt, vargs);
 478         va_end(vargs);
 479         return dev;
 480 }
 481 EXPORT_SYMBOL_GPL(cpu_device_create);
 482
 483 #ifdef CONFIG_GENERIC_CPU_AUTOPROBE
 484 static DEVICE_ATTR(modalias, 0444, print_cpu_modalias, NULL);
 485 #endif
 486
 487 static struct attribute *cpu_root_attrs[] = {
 488 #ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
 489         &dev_attr_probe.attr,
 490         &dev_attr_release.attr,
 491 #endif
 492         &cpu_attrs[0].attr.attr,
 493         &cpu_attrs[1].attr.attr,
 494         &cpu_attrs[2].attr.attr,
 495         &dev_attr_kernel_max.attr,
 496         &dev_attr_offline.attr,
 497         &dev_attr_isolated.attr,
 498 #ifdef CONFIG_NO_HZ_FULL
 499         &dev_attr_nohz_full.attr,
 500 #endif
 501 #ifdef CONFIG_CRASH_HOTPLUG
 502         &dev_attr_crash_hotplug.attr,
 503 #endif
 504 #ifdef CONFIG_GENERIC_CPU_AUTOPROBE
 505         &dev_attr_modalias.attr,
 506 #endif
 507         NULL
 508 };
 509
 510 static const struct attribute_group cpu_root_attr_group = {
 511         .attrs = cpu_root_attrs,
 512 };
 513
 514 static const struct attribute_group *cpu_root_attr_groups[] = {
 515         &cpu_root_attr_group,
 516         NULL,
 517 };
 518
 519 bool cpu_is_hotpluggable(unsigned int cpu)
 520 {
 521         struct device *dev = get_cpu_device(cpu);
 522         return dev && container_of(dev, struct cpu, dev)->hotpluggable
 523                 && tick_nohz_cpu_hotpluggable(cpu);
 524 }
 525 EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);
 526
 527 #ifdef CONFIG_GENERIC_CPU_DEVICES
 528 static DEFINE_PER_CPU(struct cpu, cpu_devices);
 529 #endif
 530
 531 static void __init cpu_dev_register_generic(void)
 532 {
 533 #ifdef CONFIG_GENERIC_CPU_DEVICES
 534         int i;
 535
 536         for_each_possible_cpu(i) {
 537                 if (register_cpu(&per_cpu(cpu_devices, i), i))
 538                         panic("Failed to register CPU device");
 539         }
 540 #endif
 541 }
 542
 543 #ifdef CONFIG_GENERIC_CPU_VULNERABILITIES
 544 static ssize_t cpu_show_not_affected(struct device *dev,
 545                               struct device_attribute *attr, char *buf)
 546 {
 547         return sysfs_emit(buf, "Not affected\n");
 548 }
 549
 550 #define CPU_SHOW_VULN_FALLBACK(func)                                    \
 551         ssize_t cpu_show_##func(struct device *,                        \
 552                                   struct device_attribute *, char *)    \
 553                  __attribute__((weak, alias("cpu_show_not_affected")))
 554
 555 CPU_SHOW_VULN_FALLBACK(meltdown);
 556 CPU_SHOW_VULN_FALLBACK(spectre_v1);
 557 CPU_SHOW_VULN_FALLBACK(spectre_v2);
 558 CPU_SHOW_VULN_FALLBACK(spec_store_bypass);
 559 CPU_SHOW_VULN_FALLBACK(l1tf);
 560 CPU_SHOW_VULN_FALLBACK(mds);
 561 CPU_SHOW_VULN_FALLBACK(tsx_async_abort);
 562 CPU_SHOW_VULN_FALLBACK(itlb_multihit);
 563 CPU_SHOW_VULN_FALLBACK(srbds);
 564 CPU_SHOW_VULN_FALLBACK(mmio_stale_data);
 565 CPU_SHOW_VULN_FALLBACK(retbleed);
 566 CPU_SHOW_VULN_FALLBACK(spec_rstack_overflow);
 567 CPU_SHOW_VULN_FALLBACK(gds);
 568
 569 static DEVICE_ATTR(meltdown, 0444, cpu_show_meltdown, NULL);
 570 static DEVICE_ATTR(spectre_v1, 0444, cpu_show_spectre_v1, NULL);
 571 static DEVICE_ATTR(spectre_v2, 0444, cpu_show_spectre_v2, NULL);
 572 static DEVICE_ATTR(spec_store_bypass, 0444, cpu_show_spec_store_bypass, NULL);
 573 static DEVICE_ATTR(l1tf, 0444, cpu_show_l1tf, NULL);
 574 static DEVICE_ATTR(mds, 0444, cpu_show_mds, NULL);
 575 static DEVICE_ATTR(tsx_async_abort, 0444, cpu_show_tsx_async_abort, NULL);
 576 static DEVICE_ATTR(itlb_multihit, 0444, cpu_show_itlb_multihit, NULL);
 577 static DEVICE_ATTR(srbds, 0444, cpu_show_srbds, NULL);
 578 static DEVICE_ATTR(mmio_stale_data, 0444, cpu_show_mmio_stale_data, NULL);
 579 static DEVICE_ATTR(retbleed, 0444, cpu_show_retbleed, NULL);
 580 static DEVICE_ATTR(spec_rstack_overflow, 0444, cpu_show_spec_rstack_overflow, NULL);
 581 static DEVICE_ATTR(gather_data_sampling, 0444, cpu_show_gds, NULL);
 582
 583 static struct attribute *cpu_root_vulnerabilities_attrs[] = {
 584         &dev_attr_meltdown.attr,
 585         &dev_attr_spectre_v1.attr,
 586         &dev_attr_spectre_v2.attr,
 587         &dev_attr_spec_store_bypass.attr,
 588         &dev_attr_l1tf.attr,
 589         &dev_attr_mds.attr,
 590         &dev_attr_tsx_async_abort.attr,
 591         &dev_attr_itlb_multihit.attr,
 592         &dev_attr_srbds.attr,
 593         &dev_attr_mmio_stale_data.attr,
 594         &dev_attr_retbleed.attr,
 595         &dev_attr_spec_rstack_overflow.attr,
 596         &dev_attr_gather_data_sampling.attr,
 597         NULL
 598 };
 599
 600 static const struct attribute_group cpu_root_vulnerabilities_group = {
 601         .name  = "vulnerabilities",
 602         .attrs = cpu_root_vulnerabilities_attrs,
 603 };
 604
 605 static void __init cpu_register_vulnerabilities(void)
 606 {
 607         struct device *dev = bus_get_dev_root(&cpu_subsys);
 608
 609         if (dev) {
 610                 if (sysfs_create_group(&dev->kobj, &cpu_root_vulnerabilities_group))
 611                         pr_err("Unable to register CPU vulnerabilities\n");
 612                 put_device(dev);
 613         }
 614 }
 615
 616 #else
 617 static inline void cpu_register_vulnerabilities(void) { }
 618 #endif
 619
 620 void __init cpu_dev_init(void)
 621 {
 622         if (subsys_system_register(&cpu_subsys, cpu_root_attr_groups))
 623                 panic("Failed to register CPU subsystem");
 624
 625         cpu_dev_register_generic();
 626         cpu_register_vulnerabilities();
 627 }