arch/s390/kernel/smp.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  SMP related functions
   4  *
   5  *    Copyright IBM Corp. 1999, 2012
   6  *    Author(s): Denis Joseph Barrow,
   7  *               Martin Schwidefsky <schwidefsky@de.ibm.com>,
   8  *               Heiko Carstens <heiko.carstens@de.ibm.com>,
   9  *
  10  *  based on other smp stuff by
  11  *    (c) 1995 Alan Cox, CymruNET Ltd  <alan@cymru.net>
  12  *    (c) 1998 Ingo Molnar
  13  *
  14  * The code outside of smp.c uses logical cpu numbers, only smp.c does
  15  * the translation of logical to physical cpu ids. All new code that
  16  * operates on physical cpu numbers needs to go into smp.c.
  17  */
  18
  19 #define KMSG_COMPONENT "cpu"
  20 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
  21
  22 #include <linux/workqueue.h>
  23 #include <linux/memblock.h>
  24 #include <linux/export.h>
  25 #include <linux/init.h>
  26 #include <linux/mm.h>
  27 #include <linux/err.h>
  28 #include <linux/spinlock.h>
  29 #include <linux/kernel_stat.h>
  30 #include <linux/delay.h>
  31 #include <linux/interrupt.h>
  32 #include <linux/irqflags.h>
  33 #include <linux/cpu.h>
  34 #include <linux/slab.h>
  35 #include <linux/sched/hotplug.h>
  36 #include <linux/sched/task_stack.h>
  37 #include <linux/crash_dump.h>
  38 #include <linux/kprobes.h>
  39 #include <asm/asm-offsets.h>
  40 #include <asm/diag.h>
  41 #include <asm/switch_to.h>
  42 #include <asm/facility.h>
  43 #include <asm/ipl.h>
  44 #include <asm/setup.h>
  45 #include <asm/irq.h>
  46 #include <asm/tlbflush.h>
  47 #include <asm/vtimer.h>
  48 #include <asm/lowcore.h>
  49 #include <asm/sclp.h>
  50 #include <asm/vdso.h>
  51 #include <asm/debug.h>
  52 #include <asm/os_info.h>
  53 #include <asm/sigp.h>
  54 #include <asm/idle.h>
  55 #include <asm/nmi.h>
  56 #include <asm/stacktrace.h>
  57 #include <asm/topology.h>
  58 #include "entry.h"
  59
  60 enum {
  61         ec_schedule = 0,
  62         ec_call_function_single,
  63         ec_stop_cpu,
  64         ec_mcck_pending,
  65 };
  66
  67 enum {
  68         CPU_STATE_STANDBY,
  69         CPU_STATE_CONFIGURED,
  70 };
  71
  72 static DEFINE_PER_CPU(struct cpu *, cpu_device);
  73
  74 struct pcpu {
  75         struct lowcore *lowcore;        /* lowcore page(s) for the cpu */
  76         unsigned long ec_mask;          /* bit mask for ec_xxx functions */
  77         unsigned long ec_clk;           /* sigp timestamp for ec_xxx */
  78         signed char state;              /* physical cpu state */
  79         signed char polarization;       /* physical polarization */
  80         u16 address;                    /* physical cpu address */
  81 };
  82
  83 static u8 boot_core_type;
  84 static struct pcpu pcpu_devices[NR_CPUS];
  85
  86 unsigned int smp_cpu_mt_shift;
  87 EXPORT_SYMBOL(smp_cpu_mt_shift);
  88
  89 unsigned int smp_cpu_mtid;
  90 EXPORT_SYMBOL(smp_cpu_mtid);
  91
  92 #ifdef CONFIG_CRASH_DUMP
  93 __vector128 __initdata boot_cpu_vector_save_area[__NUM_VXRS];
  94 #endif
  95
  96 static unsigned int smp_max_threads __initdata = -1U;
  97
  98 static int __init early_nosmt(char *s)
  99 {
 100         smp_max_threads = 1;
 101         return 0;
 102 }
 103 early_param("nosmt", early_nosmt);
 104
 105 static int __init early_smt(char *s)
 106 {
 107         get_option(&s, &smp_max_threads);
 108         return 0;
 109 }
 110 early_param("smt", early_smt);
 111
 112 /*
 113  * The smp_cpu_state_mutex must be held when changing the state or polarization
 114  * member of a pcpu data structure within the pcpu_devices arreay.
 115  */
 116 DEFINE_MUTEX(smp_cpu_state_mutex);
 117
 118 /*
 119  * Signal processor helper functions.
 120  */
 121 static inline int __pcpu_sigp_relax(u16 addr, u8 order, unsigned long parm)
 122 {
 123         int cc;
 124
 125         while (1) {
 126                 cc = __pcpu_sigp(addr, order, parm, NULL);
 127                 if (cc != SIGP_CC_BUSY)
 128                         return cc;
 129                 cpu_relax();
 130         }
 131 }
 132
 133 static int pcpu_sigp_retry(struct pcpu *pcpu, u8 order, u32 parm)
 134 {
 135         int cc, retry;
 136
 137         for (retry = 0; ; retry++) {
 138                 cc = __pcpu_sigp(pcpu->address, order, parm, NULL);
 139                 if (cc != SIGP_CC_BUSY)
 140                         break;
 141                 if (retry >= 3)
 142                         udelay(10);
 143         }
 144         return cc;
 145 }
 146
 147 static inline int pcpu_stopped(struct pcpu *pcpu)
 148 {
 149         u32 status;
 150
 151         if (__pcpu_sigp(pcpu->address, SIGP_SENSE,
 152                         0, &status) != SIGP_CC_STATUS_STORED)
 153                 return 0;
 154         return !!(status & (SIGP_STATUS_CHECK_STOP|SIGP_STATUS_STOPPED));
 155 }
 156
 157 static inline int pcpu_running(struct pcpu *pcpu)
 158 {
 159         if (__pcpu_sigp(pcpu->address, SIGP_SENSE_RUNNING,
 160                         0, NULL) != SIGP_CC_STATUS_STORED)
 161                 return 1;
 162         /* Status stored condition code is equivalent to cpu not running. */
 163         return 0;
 164 }
 165
 166 /*
 167  * Find struct pcpu by cpu address.
 168  */
 169 static struct pcpu *pcpu_find_address(const struct cpumask *mask, u16 address)
 170 {
 171         int cpu;
 172
 173         for_each_cpu(cpu, mask)
 174                 if (pcpu_devices[cpu].address == address)
 175                         return pcpu_devices + cpu;
 176         return NULL;
 177 }
 178
 179 static void pcpu_ec_call(struct pcpu *pcpu, int ec_bit)
 180 {
 181         int order;
 182
 183         if (test_and_set_bit(ec_bit, &pcpu->ec_mask))
 184                 return;
 185         order = pcpu_running(pcpu) ? SIGP_EXTERNAL_CALL : SIGP_EMERGENCY_SIGNAL;
 186         pcpu->ec_clk = get_tod_clock_fast();
 187         pcpu_sigp_retry(pcpu, order, 0);
 188 }
 189
 190 static int pcpu_alloc_lowcore(struct pcpu *pcpu, int cpu)
 191 {
 192         unsigned long async_stack, nodat_stack;
 193         struct lowcore *lc;
 194
 195         if (pcpu != &pcpu_devices[0]) {
 196                 pcpu->lowcore = (struct lowcore *)
 197                         __get_free_pages(GFP_KERNEL | GFP_DMA, LC_ORDER);
 198                 nodat_stack = __get_free_pages(GFP_KERNEL, THREAD_SIZE_ORDER);
 199                 if (!pcpu->lowcore || !nodat_stack)
 200                         goto out;
 201         } else {
 202                 nodat_stack = pcpu->lowcore->nodat_stack - STACK_INIT_OFFSET;
 203         }
 204         async_stack = stack_alloc();
 205         if (!async_stack)
 206                 goto out;
 207         lc = pcpu->lowcore;
 208         memcpy(lc, &S390_lowcore, 512);
 209         memset((char *) lc + 512, 0, sizeof(*lc) - 512);
 210         lc->async_stack = async_stack + STACK_INIT_OFFSET;
 211         lc->nodat_stack = nodat_stack + STACK_INIT_OFFSET;
 212         lc->cpu_nr = cpu;
 213         lc->spinlock_lockval = arch_spin_lockval(cpu);
 214         lc->spinlock_index = 0;
 215         lc->br_r1_trampoline = 0x07f1;  /* br %r1 */
 216         lc->return_lpswe = gen_lpswe(__LC_RETURN_PSW);
 217         lc->return_mcck_lpswe = gen_lpswe(__LC_RETURN_MCCK_PSW);
 218         if (nmi_alloc_per_cpu(lc))
 219                 goto out_async;
 220         if (vdso_alloc_per_cpu(lc))
 221                 goto out_mcesa;
 222         lowcore_ptr[cpu] = lc;
 223         pcpu_sigp_retry(pcpu, SIGP_SET_PREFIX, (u32)(unsigned long) lc);
 224         return 0;
 225
 226 out_mcesa:
 227         nmi_free_per_cpu(lc);
 228 out_async:
 229         stack_free(async_stack);
 230 out:
 231         if (pcpu != &pcpu_devices[0]) {
 232                 free_pages(nodat_stack, THREAD_SIZE_ORDER);
 233                 free_pages((unsigned long) pcpu->lowcore, LC_ORDER);
 234         }
 235         return -ENOMEM;
 236 }
 237
 238 static void pcpu_free_lowcore(struct pcpu *pcpu)
 239 {
 240         unsigned long async_stack, nodat_stack, lowcore;
 241
 242         nodat_stack = pcpu->lowcore->nodat_stack - STACK_INIT_OFFSET;
 243         async_stack = pcpu->lowcore->async_stack - STACK_INIT_OFFSET;
 244         lowcore = (unsigned long) pcpu->lowcore;
 245
 246         pcpu_sigp_retry(pcpu, SIGP_SET_PREFIX, 0);
 247         lowcore_ptr[pcpu - pcpu_devices] = NULL;
 248         vdso_free_per_cpu(pcpu->lowcore);
 249         nmi_free_per_cpu(pcpu->lowcore);
 250         stack_free(async_stack);
 251         if (pcpu == &pcpu_devices[0])
 252                 return;
 253         free_pages(nodat_stack, THREAD_SIZE_ORDER);
 254         free_pages(lowcore, LC_ORDER);
 255 }
 256
 257 static void pcpu_prepare_secondary(struct pcpu *pcpu, int cpu)
 258 {
 259         struct lowcore *lc = pcpu->lowcore;
 260
 261         cpumask_set_cpu(cpu, &init_mm.context.cpu_attach_mask);
 262         cpumask_set_cpu(cpu, mm_cpumask(&init_mm));
 263         lc->cpu_nr = cpu;
 264         lc->spinlock_lockval = arch_spin_lockval(cpu);
 265         lc->spinlock_index = 0;
 266         lc->percpu_offset = __per_cpu_offset[cpu];
 267         lc->kernel_asce = S390_lowcore.kernel_asce;
 268         lc->user_asce = S390_lowcore.kernel_asce;
 269         lc->machine_flags = S390_lowcore.machine_flags;
 270         lc->user_timer = lc->system_timer =
 271                 lc->steal_timer = lc->avg_steal_timer = 0;
 272         __ctl_store(lc->cregs_save_area, 0, 15);
 273         lc->cregs_save_area[1] = lc->kernel_asce;
 274         lc->cregs_save_area[7] = lc->vdso_asce;
 275         save_access_regs((unsigned int *) lc->access_regs_save_area);
 276         memcpy(lc->stfle_fac_list, S390_lowcore.stfle_fac_list,
 277                sizeof(lc->stfle_fac_list));
 278         memcpy(lc->alt_stfle_fac_list, S390_lowcore.alt_stfle_fac_list,
 279                sizeof(lc->alt_stfle_fac_list));
 280         arch_spin_lock_setup(cpu);
 281 }
 282
 283 static void pcpu_attach_task(struct pcpu *pcpu, struct task_struct *tsk)
 284 {
 285         struct lowcore *lc = pcpu->lowcore;
 286
 287         lc->kernel_stack = (unsigned long) task_stack_page(tsk)
 288                 + THREAD_SIZE - STACK_FRAME_OVERHEAD - sizeof(struct pt_regs);
 289         lc->current_task = (unsigned long) tsk;
 290         lc->lpp = LPP_MAGIC;
 291         lc->current_pid = tsk->pid;
 292         lc->user_timer = tsk->thread.user_timer;
 293         lc->guest_timer = tsk->thread.guest_timer;
 294         lc->system_timer = tsk->thread.system_timer;
 295         lc->hardirq_timer = tsk->thread.hardirq_timer;
 296         lc->softirq_timer = tsk->thread.softirq_timer;
 297         lc->steal_timer = 0;
 298 }
 299
 300 static void pcpu_start_fn(struct pcpu *pcpu, void (*func)(void *), void *data)
 301 {
 302         struct lowcore *lc = pcpu->lowcore;
 303
 304         lc->restart_stack = lc->nodat_stack;
 305         lc->restart_fn = (unsigned long) func;
 306         lc->restart_data = (unsigned long) data;
 307         lc->restart_source = -1UL;
 308         pcpu_sigp_retry(pcpu, SIGP_RESTART, 0);
 309 }
 310
 311 /*
 312  * Call function via PSW restart on pcpu and stop the current cpu.
 313  */
 314 static void __pcpu_delegate(void (*func)(void*), void *data)
 315 {
 316         func(data);     /* should not return */
 317 }
 318
 319 static void __no_sanitize_address pcpu_delegate(struct pcpu *pcpu,
 320                                                 void (*func)(void *),
 321                                                 void *data, unsigned long stack)
 322 {
 323         struct lowcore *lc = lowcore_ptr[pcpu - pcpu_devices];
 324         unsigned long source_cpu = stap();
 325
 326         __load_psw_mask(PSW_KERNEL_BITS | PSW_MASK_DAT);
 327         if (pcpu->address == source_cpu)
 328                 CALL_ON_STACK(__pcpu_delegate, stack, 2, func, data);
 329         /* Stop target cpu (if func returns this stops the current cpu). */
 330         pcpu_sigp_retry(pcpu, SIGP_STOP, 0);
 331         /* Restart func on the target cpu and stop the current cpu. */
 332         mem_assign_absolute(lc->restart_stack, stack);
 333         mem_assign_absolute(lc->restart_fn, (unsigned long) func);
 334         mem_assign_absolute(lc->restart_data, (unsigned long) data);
 335         mem_assign_absolute(lc->restart_source, source_cpu);
 336         __bpon();
 337         asm volatile(
 338                 "0:     sigp    0,%0,%2 # sigp restart to target cpu\n"
 339                 "       brc     2,0b    # busy, try again\n"
 340                 "1:     sigp    0,%1,%3 # sigp stop to current cpu\n"
 341                 "       brc     2,1b    # busy, try again\n"
 342                 : : "d" (pcpu->address), "d" (source_cpu),
 343                     "K" (SIGP_RESTART), "K" (SIGP_STOP)
 344                 : "0", "1", "cc");
 345         for (;;) ;
 346 }
 347
 348 /*
 349  * Enable additional logical cpus for multi-threading.
 350  */
 351 static int pcpu_set_smt(unsigned int mtid)
 352 {
 353         int cc;
 354
 355         if (smp_cpu_mtid == mtid)
 356                 return 0;
 357         cc = __pcpu_sigp(0, SIGP_SET_MULTI_THREADING, mtid, NULL);
 358         if (cc == 0) {
 359                 smp_cpu_mtid = mtid;
 360                 smp_cpu_mt_shift = 0;
 361                 while (smp_cpu_mtid >= (1U << smp_cpu_mt_shift))
 362                         smp_cpu_mt_shift++;
 363                 pcpu_devices[0].address = stap();
 364         }
 365         return cc;
 366 }
 367
 368 /*
 369  * Call function on an online CPU.
 370  */
 371 void smp_call_online_cpu(void (*func)(void *), void *data)
 372 {
 373         struct pcpu *pcpu;
 374
 375         /* Use the current cpu if it is online. */
 376         pcpu = pcpu_find_address(cpu_online_mask, stap());
 377         if (!pcpu)
 378                 /* Use the first online cpu. */
 379                 pcpu = pcpu_devices + cpumask_first(cpu_online_mask);
 380         pcpu_delegate(pcpu, func, data, (unsigned long) restart_stack);
 381 }
 382
 383 /*
 384  * Call function on the ipl CPU.
 385  */
 386 void smp_call_ipl_cpu(void (*func)(void *), void *data)
 387 {
 388         struct lowcore *lc = pcpu_devices->lowcore;
 389
 390         if (pcpu_devices[0].address == stap())
 391                 lc = &S390_lowcore;
 392
 393         pcpu_delegate(&pcpu_devices[0], func, data,
 394                       lc->nodat_stack);
 395 }
 396
 397 int smp_find_processor_id(u16 address)
 398 {
 399         int cpu;
 400
 401         for_each_present_cpu(cpu)
 402                 if (pcpu_devices[cpu].address == address)
 403                         return cpu;
 404         return -1;
 405 }
 406
 407 void schedule_mcck_handler(void)
 408 {
 409         pcpu_ec_call(pcpu_devices + smp_processor_id(), ec_mcck_pending);
 410 }
 411
 412 bool notrace arch_vcpu_is_preempted(int cpu)
 413 {
 414         if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu))
 415                 return false;
 416         if (pcpu_running(pcpu_devices + cpu))
 417                 return false;
 418         return true;
 419 }
 420 EXPORT_SYMBOL(arch_vcpu_is_preempted);
 421
 422 void notrace smp_yield_cpu(int cpu)
 423 {
 424         if (!MACHINE_HAS_DIAG9C)
 425                 return;
 426         diag_stat_inc_norecursion(DIAG_STAT_X09C);
 427         asm volatile("diag %0,0,0x9c"
 428                      : : "d" (pcpu_devices[cpu].address));
 429 }
 430
 431 /*
 432  * Send cpus emergency shutdown signal. This gives the cpus the
 433  * opportunity to complete outstanding interrupts.
 434  */
 435 void notrace smp_emergency_stop(void)
 436 {
 437         cpumask_t cpumask;
 438         u64 end;
 439         int cpu;
 440
 441         cpumask_copy(&cpumask, cpu_online_mask);
 442         cpumask_clear_cpu(smp_processor_id(), &cpumask);
 443
 444         end = get_tod_clock() + (1000000UL << 12);
 445         for_each_cpu(cpu, &cpumask) {
 446                 struct pcpu *pcpu = pcpu_devices + cpu;
 447                 set_bit(ec_stop_cpu, &pcpu->ec_mask);
 448                 while (__pcpu_sigp(pcpu->address, SIGP_EMERGENCY_SIGNAL,
 449                                    0, NULL) == SIGP_CC_BUSY &&
 450                        get_tod_clock() < end)
 451                         cpu_relax();
 452         }
 453         while (get_tod_clock() < end) {
 454                 for_each_cpu(cpu, &cpumask)
 455                         if (pcpu_stopped(pcpu_devices + cpu))
 456                                 cpumask_clear_cpu(cpu, &cpumask);
 457                 if (cpumask_empty(&cpumask))
 458                         break;
 459                 cpu_relax();
 460         }
 461 }
 462 NOKPROBE_SYMBOL(smp_emergency_stop);
 463
 464 /*
 465  * Stop all cpus but the current one.
 466  */
 467 void smp_send_stop(void)
 468 {
 469         int cpu;
 470
 471         /* Disable all interrupts/machine checks */
 472         __load_psw_mask(PSW_KERNEL_BITS | PSW_MASK_DAT);
 473         trace_hardirqs_off();
 474
 475         debug_set_critical();
 476
 477         if (oops_in_progress)
 478                 smp_emergency_stop();
 479
 480         /* stop all processors */
 481         for_each_online_cpu(cpu) {
 482                 if (cpu == smp_processor_id())
 483                         continue;
 484                 pcpu_sigp_retry(pcpu_devices + cpu, SIGP_STOP, 0);
 485                 while (!pcpu_stopped(pcpu_devices + cpu))
 486                         cpu_relax();
 487         }
 488 }
 489
 490 /*
 491  * This is the main routine where commands issued by other
 492  * cpus are handled.
 493  */
 494 static void smp_handle_ext_call(void)
 495 {
 496         unsigned long bits;
 497
 498         /* handle bit signal external calls */
 499         bits = xchg(&pcpu_devices[smp_processor_id()].ec_mask, 0);
 500         if (test_bit(ec_stop_cpu, &bits))
 501                 smp_stop_cpu();
 502         if (test_bit(ec_schedule, &bits))
 503                 scheduler_ipi();
 504         if (test_bit(ec_call_function_single, &bits))
 505                 generic_smp_call_function_single_interrupt();
 506         if (test_bit(ec_mcck_pending, &bits))
 507                 s390_handle_mcck();
 508 }
 509
 510 static void do_ext_call_interrupt(struct ext_code ext_code,
 511                                   unsigned int param32, unsigned long param64)
 512 {
 513         inc_irq_stat(ext_code.code == 0x1202 ? IRQEXT_EXC : IRQEXT_EMS);
 514         smp_handle_ext_call();
 515 }
 516
 517 void arch_send_call_function_ipi_mask(const struct cpumask *mask)
 518 {
 519         int cpu;
 520
 521         for_each_cpu(cpu, mask)
 522                 pcpu_ec_call(pcpu_devices + cpu, ec_call_function_single);
 523 }
 524
 525 void arch_send_call_function_single_ipi(int cpu)
 526 {
 527         pcpu_ec_call(pcpu_devices + cpu, ec_call_function_single);
 528 }
 529
 530 /*
 531  * this function sends a 'reschedule' IPI to another CPU.
 532  * it goes straight through and wastes no time serializing
 533  * anything. Worst case is that we lose a reschedule ...
 534  */
 535 void smp_send_reschedule(int cpu)
 536 {
 537         pcpu_ec_call(pcpu_devices + cpu, ec_schedule);
 538 }
 539
 540 /*
 541  * parameter area for the set/clear control bit callbacks
 542  */
 543 struct ec_creg_mask_parms {
 544         unsigned long orval;
 545         unsigned long andval;
 546         int cr;
 547 };
 548
 549 /*
 550  * callback for setting/clearing control bits
 551  */
 552 static void smp_ctl_bit_callback(void *info)
 553 {
 554         struct ec_creg_mask_parms *pp = info;
 555         unsigned long cregs[16];
 556
 557         __ctl_store(cregs, 0, 15);
 558         cregs[pp->cr] = (cregs[pp->cr] & pp->andval) | pp->orval;
 559         __ctl_load(cregs, 0, 15);
 560 }
 561
 562 /*
 563  * Set a bit in a control register of all cpus
 564  */
 565 void smp_ctl_set_bit(int cr, int bit)
 566 {
 567         struct ec_creg_mask_parms parms = { 1UL << bit, -1UL, cr };
 568
 569         on_each_cpu(smp_ctl_bit_callback, &parms, 1);
 570 }
 571 EXPORT_SYMBOL(smp_ctl_set_bit);
 572
 573 /*
 574  * Clear a bit in a control register of all cpus
 575  */
 576 void smp_ctl_clear_bit(int cr, int bit)
 577 {
 578         struct ec_creg_mask_parms parms = { 0, ~(1UL << bit), cr };
 579
 580         on_each_cpu(smp_ctl_bit_callback, &parms, 1);
 581 }
 582 EXPORT_SYMBOL(smp_ctl_clear_bit);
 583
 584 #ifdef CONFIG_CRASH_DUMP
 585
 586 int smp_store_status(int cpu)
 587 {
 588         struct pcpu *pcpu = pcpu_devices + cpu;
 589         unsigned long pa;
 590
 591         pa = __pa(&pcpu->lowcore->floating_pt_save_area);
 592         if (__pcpu_sigp_relax(pcpu->address, SIGP_STORE_STATUS_AT_ADDRESS,
 593                               pa) != SIGP_CC_ORDER_CODE_ACCEPTED)
 594                 return -EIO;
 595         if (!MACHINE_HAS_VX && !MACHINE_HAS_GS)
 596                 return 0;
 597         pa = __pa(pcpu->lowcore->mcesad & MCESA_ORIGIN_MASK);
 598         if (MACHINE_HAS_GS)
 599                 pa |= pcpu->lowcore->mcesad & MCESA_LC_MASK;
 600         if (__pcpu_sigp_relax(pcpu->address, SIGP_STORE_ADDITIONAL_STATUS,
 601                               pa) != SIGP_CC_ORDER_CODE_ACCEPTED)
 602                 return -EIO;
 603         return 0;
 604 }
 605
 606 /*
 607  * Collect CPU state of the previous, crashed system.
 608  * There are four cases:
 609  * 1) standard zfcp/nvme dump
 610  *    condition: OLDMEM_BASE == NULL && is_ipl_type_dump() == true
 611  *    The state for all CPUs except the boot CPU needs to be collected
 612  *    with sigp stop-and-store-status. The boot CPU state is located in
 613  *    the absolute lowcore of the memory stored in the HSA. The zcore code
 614  *    will copy the boot CPU state from the HSA.
 615  * 2) stand-alone kdump for SCSI/NVMe (zfcp/nvme dump with swapped memory)
 616  *    condition: OLDMEM_BASE != NULL && is_ipl_type_dump() == true
 617  *    The state for all CPUs except the boot CPU needs to be collected
 618  *    with sigp stop-and-store-status. The firmware or the boot-loader
 619  *    stored the registers of the boot CPU in the absolute lowcore in the
 620  *    memory of the old system.
 621  * 3) kdump and the old kernel did not store the CPU state,
 622  *    or stand-alone kdump for DASD
 623  *    condition: OLDMEM_BASE != NULL && !is_kdump_kernel()
 624  *    The state for all CPUs except the boot CPU needs to be collected
 625  *    with sigp stop-and-store-status. The kexec code or the boot-loader
 626  *    stored the registers of the boot CPU in the memory of the old system.
 627  * 4) kdump and the old kernel stored the CPU state
 628  *    condition: OLDMEM_BASE != NULL && is_kdump_kernel()
 629  *    This case does not exist for s390 anymore, setup_arch explicitly
 630  *    deactivates the elfcorehdr= kernel parameter
 631  */
 632 static __init void smp_save_cpu_vxrs(struct save_area *sa, u16 addr,
 633                                      bool is_boot_cpu, unsigned long page)
 634 {
 635         __vector128 *vxrs = (__vector128 *) page;
 636
 637         if (is_boot_cpu)
 638                 vxrs = boot_cpu_vector_save_area;
 639         else
 640                 __pcpu_sigp_relax(addr, SIGP_STORE_ADDITIONAL_STATUS, page);
 641         save_area_add_vxrs(sa, vxrs);
 642 }
 643
 644 static __init void smp_save_cpu_regs(struct save_area *sa, u16 addr,
 645                                      bool is_boot_cpu, unsigned long page)
 646 {
 647         void *regs = (void *) page;
 648
 649         if (is_boot_cpu)
 650                 copy_oldmem_kernel(regs, (void *) __LC_FPREGS_SAVE_AREA, 512);
 651         else
 652                 __pcpu_sigp_relax(addr, SIGP_STORE_STATUS_AT_ADDRESS, page);
 653         save_area_add_regs(sa, regs);
 654 }
 655
 656 void __init smp_save_dump_cpus(void)
 657 {
 658         int addr, boot_cpu_addr, max_cpu_addr;
 659         struct save_area *sa;
 660         unsigned long page;
 661         bool is_boot_cpu;
 662
 663         if (!(OLDMEM_BASE || is_ipl_type_dump()))
 664                 /* No previous system present, normal boot. */
 665                 return;
 666         /* Allocate a page as dumping area for the store status sigps */
 667         page = memblock_phys_alloc_range(PAGE_SIZE, PAGE_SIZE, 0, 1UL << 31);
 668         if (!page)
 669                 panic("ERROR: Failed to allocate %lx bytes below %lx\n",
 670                       PAGE_SIZE, 1UL << 31);
 671
 672         /* Set multi-threading state to the previous system. */
 673         pcpu_set_smt(sclp.mtid_prev);
 674         boot_cpu_addr = stap();
 675         max_cpu_addr = SCLP_MAX_CORES << sclp.mtid_prev;
 676         for (addr = 0; addr <= max_cpu_addr; addr++) {
 677                 if (__pcpu_sigp_relax(addr, SIGP_SENSE, 0) ==
 678                     SIGP_CC_NOT_OPERATIONAL)
 679                         continue;
 680                 is_boot_cpu = (addr == boot_cpu_addr);
 681                 /* Allocate save area */
 682                 sa = save_area_alloc(is_boot_cpu);
 683                 if (!sa)
 684                         panic("could not allocate memory for save area\n");
 685                 if (MACHINE_HAS_VX)
 686                         /* Get the vector registers */
 687                         smp_save_cpu_vxrs(sa, addr, is_boot_cpu, page);
 688                 /*
 689                  * For a zfcp/nvme dump OLDMEM_BASE == NULL and the registers
 690                  * of the boot CPU are stored in the HSA. To retrieve
 691                  * these registers an SCLP request is required which is
 692                  * done by drivers/s390/char/zcore.c:init_cpu_info()
 693                  */
 694                 if (!is_boot_cpu || OLDMEM_BASE)
 695                         /* Get the CPU registers */
 696                         smp_save_cpu_regs(sa, addr, is_boot_cpu, page);
 697         }
 698         memblock_free(page, PAGE_SIZE);
 699         diag_dma_ops.diag308_reset();
 700         pcpu_set_smt(0);
 701 }
 702 #endif /* CONFIG_CRASH_DUMP */
 703
 704 void smp_cpu_set_polarization(int cpu, int val)
 705 {
 706         pcpu_devices[cpu].polarization = val;
 707 }
 708
 709 int smp_cpu_get_polarization(int cpu)
 710 {
 711         return pcpu_devices[cpu].polarization;
 712 }
 713
 714 int smp_cpu_get_cpu_address(int cpu)
 715 {
 716         return pcpu_devices[cpu].address;
 717 }
 718
 719 static void __ref smp_get_core_info(struct sclp_core_info *info, int early)
 720 {
 721         static int use_sigp_detection;
 722         int address;
 723
 724         if (use_sigp_detection || sclp_get_core_info(info, early)) {
 725                 use_sigp_detection = 1;
 726                 for (address = 0;
 727                      address < (SCLP_MAX_CORES << smp_cpu_mt_shift);
 728                      address += (1U << smp_cpu_mt_shift)) {
 729                         if (__pcpu_sigp_relax(address, SIGP_SENSE, 0) ==
 730                             SIGP_CC_NOT_OPERATIONAL)
 731                                 continue;
 732                         info->core[info->configured].core_id =
 733                                 address >> smp_cpu_mt_shift;
 734                         info->configured++;
 735                 }
 736                 info->combined = info->configured;
 737         }
 738 }
 739
 740 static int smp_add_present_cpu(int cpu);
 741
 742 static int smp_add_core(struct sclp_core_entry *core, cpumask_t *avail,
 743                         bool configured, bool early)
 744 {
 745         struct pcpu *pcpu;
 746         int cpu, nr, i;
 747         u16 address;
 748
 749         nr = 0;
 750         if (sclp.has_core_type && core->type != boot_core_type)
 751                 return nr;
 752         cpu = cpumask_first(avail);
 753         address = core->core_id << smp_cpu_mt_shift;
 754         for (i = 0; (i <= smp_cpu_mtid) && (cpu < nr_cpu_ids); i++) {
 755                 if (pcpu_find_address(cpu_present_mask, address + i))
 756                         continue;
 757                 pcpu = pcpu_devices + cpu;
 758                 pcpu->address = address + i;
 759                 if (configured)
 760                         pcpu->state = CPU_STATE_CONFIGURED;
 761                 else
 762                         pcpu->state = CPU_STATE_STANDBY;
 763                 smp_cpu_set_polarization(cpu, POLARIZATION_UNKNOWN);
 764                 set_cpu_present(cpu, true);
 765                 if (!early && smp_add_present_cpu(cpu) != 0)
 766                         set_cpu_present(cpu, false);
 767                 else
 768                         nr++;
 769                 cpumask_clear_cpu(cpu, avail);
 770                 cpu = cpumask_next(cpu, avail);
 771         }
 772         return nr;
 773 }
 774
 775 static int __smp_rescan_cpus(struct sclp_core_info *info, bool early)
 776 {
 777         struct sclp_core_entry *core;
 778         cpumask_t avail;
 779         bool configured;
 780         u16 core_id;
 781         int nr, i;
 782
 783         nr = 0;
 784         cpumask_xor(&avail, cpu_possible_mask, cpu_present_mask);
 785         /*
 786          * Add IPL core first (which got logical CPU number 0) to make sure
 787          * that all SMT threads get subsequent logical CPU numbers.
 788          */
 789         if (early) {
 790                 core_id = pcpu_devices[0].address >> smp_cpu_mt_shift;
 791                 for (i = 0; i < info->configured; i++) {
 792                         core = &info->core[i];
 793                         if (core->core_id == core_id) {
 794                                 nr += smp_add_core(core, &avail, true, early);
 795                                 break;
 796                         }
 797                 }
 798         }
 799         for (i = 0; i < info->combined; i++) {
 800                 configured = i < info->configured;
 801                 nr += smp_add_core(&info->core[i], &avail, configured, early);
 802         }
 803         return nr;
 804 }
 805
 806 void __init smp_detect_cpus(void)
 807 {
 808         unsigned int cpu, mtid, c_cpus, s_cpus;
 809         struct sclp_core_info *info;
 810         u16 address;
 811
 812         /* Get CPU information */
 813         info = memblock_alloc(sizeof(*info), 8);
 814         if (!info)
 815                 panic("%s: Failed to allocate %zu bytes align=0x%x\n",
 816                       __func__, sizeof(*info), 8);
 817         smp_get_core_info(info, 1);
 818         /* Find boot CPU type */
 819         if (sclp.has_core_type) {
 820                 address = stap();
 821                 for (cpu = 0; cpu < info->combined; cpu++)
 822                         if (info->core[cpu].core_id == address) {
 823                                 /* The boot cpu dictates the cpu type. */
 824                                 boot_core_type = info->core[cpu].type;
 825                                 break;
 826                         }
 827                 if (cpu >= info->combined)
 828                         panic("Could not find boot CPU type");
 829         }
 830
 831         /* Set multi-threading state for the current system */
 832         mtid = boot_core_type ? sclp.mtid : sclp.mtid_cp;
 833         mtid = (mtid < smp_max_threads) ? mtid : smp_max_threads - 1;
 834         pcpu_set_smt(mtid);
 835
 836         /* Print number of CPUs */
 837         c_cpus = s_cpus = 0;
 838         for (cpu = 0; cpu < info->combined; cpu++) {
 839                 if (sclp.has_core_type &&
 840                     info->core[cpu].type != boot_core_type)
 841                         continue;
 842                 if (cpu < info->configured)
 843                         c_cpus += smp_cpu_mtid + 1;
 844                 else
 845                         s_cpus += smp_cpu_mtid + 1;
 846         }
 847         pr_info("%d configured CPUs, %d standby CPUs\n", c_cpus, s_cpus);
 848
 849         /* Add CPUs present at boot */
 850         get_online_cpus();
 851         __smp_rescan_cpus(info, true);
 852         put_online_cpus();
 853         memblock_free_early((unsigned long)info, sizeof(*info));
 854 }
 855
 856 static void smp_init_secondary(void)
 857 {
 858         int cpu = raw_smp_processor_id();
 859
 860         S390_lowcore.last_update_clock = get_tod_clock();
 861         restore_access_regs(S390_lowcore.access_regs_save_area);
 862         set_cpu_flag(CIF_ASCE_PRIMARY);
 863         set_cpu_flag(CIF_ASCE_SECONDARY);
 864         cpu_init();
 865         rcu_cpu_starting(cpu);
 866         preempt_disable();
 867         init_cpu_timer();
 868         vtime_init();
 869         pfault_init();
 870         notify_cpu_starting(cpu);
 871         if (topology_cpu_dedicated(cpu))
 872                 set_cpu_flag(CIF_DEDICATED_CPU);
 873         else
 874                 clear_cpu_flag(CIF_DEDICATED_CPU);
 875         set_cpu_online(cpu, true);
 876         update_cpu_masks();
 877         inc_irq_stat(CPU_RST);
 878         local_irq_enable();
 879         cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 880 }
 881
 882 /*
 883  *      Activate a secondary processor.
 884  */
 885 static void __no_sanitize_address smp_start_secondary(void *cpuvoid)
 886 {
 887         S390_lowcore.restart_stack = (unsigned long) restart_stack;
 888         S390_lowcore.restart_fn = (unsigned long) do_restart;
 889         S390_lowcore.restart_data = 0;
 890         S390_lowcore.restart_source = -1UL;
 891         __ctl_load(S390_lowcore.cregs_save_area, 0, 15);
 892         __load_psw_mask(PSW_KERNEL_BITS | PSW_MASK_DAT);
 893         CALL_ON_STACK_NORETURN(smp_init_secondary, S390_lowcore.kernel_stack);
 894 }
 895
 896 /* Upping and downing of CPUs */
 897 int __cpu_up(unsigned int cpu, struct task_struct *tidle)
 898 {
 899         struct pcpu *pcpu;
 900         int base, i, rc;
 901
 902         pcpu = pcpu_devices + cpu;
 903         if (pcpu->state != CPU_STATE_CONFIGURED)
 904                 return -EIO;
 905         base = smp_get_base_cpu(cpu);
 906         for (i = 0; i <= smp_cpu_mtid; i++) {
 907                 if (base + i < nr_cpu_ids)
 908                         if (cpu_online(base + i))
 909                                 break;
 910         }
 911         /*
 912          * If this is the first CPU of the core to get online
 913          * do an initial CPU reset.
 914          */
 915         if (i > smp_cpu_mtid &&
 916             pcpu_sigp_retry(pcpu_devices + base, SIGP_INITIAL_CPU_RESET, 0) !=
 917             SIGP_CC_ORDER_CODE_ACCEPTED)
 918                 return -EIO;
 919
 920         rc = pcpu_alloc_lowcore(pcpu, cpu);
 921         if (rc)
 922                 return rc;
 923         pcpu_prepare_secondary(pcpu, cpu);
 924         pcpu_attach_task(pcpu, tidle);
 925         pcpu_start_fn(pcpu, smp_start_secondary, NULL);
 926         /* Wait until cpu puts itself in the online & active maps */
 927         while (!cpu_online(cpu))
 928                 cpu_relax();
 929         return 0;
 930 }
 931
 932 static unsigned int setup_possible_cpus __initdata;
 933
 934 static int __init _setup_possible_cpus(char *s)
 935 {
 936         get_option(&s, &setup_possible_cpus);
 937         return 0;
 938 }
 939 early_param("possible_cpus", _setup_possible_cpus);
 940
 941 int __cpu_disable(void)
 942 {
 943         unsigned long cregs[16];
 944
 945         /* Handle possible pending IPIs */
 946         smp_handle_ext_call();
 947         set_cpu_online(smp_processor_id(), false);
 948         update_cpu_masks();
 949         /* Disable pseudo page faults on this cpu. */
 950         pfault_fini();
 951         /* Disable interrupt sources via control register. */
 952         __ctl_store(cregs, 0, 15);
 953         cregs[0]  &= ~0x0000ee70UL;     /* disable all external interrupts */
 954         cregs[6]  &= ~0xff000000UL;     /* disable all I/O interrupts */
 955         cregs[14] &= ~0x1f000000UL;     /* disable most machine checks */
 956         __ctl_load(cregs, 0, 15);
 957         clear_cpu_flag(CIF_NOHZ_DELAY);
 958         return 0;
 959 }
 960
 961 void __cpu_die(unsigned int cpu)
 962 {
 963         struct pcpu *pcpu;
 964
 965         /* Wait until target cpu is down */
 966         pcpu = pcpu_devices + cpu;
 967         while (!pcpu_stopped(pcpu))
 968                 cpu_relax();
 969         pcpu_free_lowcore(pcpu);
 970         cpumask_clear_cpu(cpu, mm_cpumask(&init_mm));
 971         cpumask_clear_cpu(cpu, &init_mm.context.cpu_attach_mask);
 972 }
 973
 974 void __noreturn cpu_die(void)
 975 {
 976         idle_task_exit();
 977         __bpon();
 978         pcpu_sigp_retry(pcpu_devices + smp_processor_id(), SIGP_STOP, 0);
 979         for (;;) ;
 980 }
 981
 982 void __init smp_fill_possible_mask(void)
 983 {
 984         unsigned int possible, sclp_max, cpu;
 985
 986         sclp_max = max(sclp.mtid, sclp.mtid_cp) + 1;
 987         sclp_max = min(smp_max_threads, sclp_max);
 988         sclp_max = (sclp.max_cores * sclp_max) ?: nr_cpu_ids;
 989         possible = setup_possible_cpus ?: nr_cpu_ids;
 990         possible = min(possible, sclp_max);
 991         for (cpu = 0; cpu < possible && cpu < nr_cpu_ids; cpu++)
 992                 set_cpu_possible(cpu, true);
 993 }
 994
 995 void __init smp_prepare_cpus(unsigned int max_cpus)
 996 {
 997         /* request the 0x1201 emergency signal external interrupt */
 998         if (register_external_irq(EXT_IRQ_EMERGENCY_SIG, do_ext_call_interrupt))
 999                 panic("Couldn't request external interrupt 0x1201");
1000         /* request the 0x1202 external call external interrupt */
1001         if (register_external_irq(EXT_IRQ_EXTERNAL_CALL, do_ext_call_interrupt))
1002                 panic("Couldn't request external interrupt 0x1202");
1003 }
1004
1005 void __init smp_prepare_boot_cpu(void)
1006 {
1007         struct pcpu *pcpu = pcpu_devices;
1008
1009         WARN_ON(!cpu_present(0) || !cpu_online(0));
1010         pcpu->state = CPU_STATE_CONFIGURED;
1011         pcpu->lowcore = (struct lowcore *)(unsigned long) store_prefix();
1012         S390_lowcore.percpu_offset = __per_cpu_offset[0];
1013         smp_cpu_set_polarization(0, POLARIZATION_UNKNOWN);
1014 }
1015
1016 void __init smp_setup_processor_id(void)
1017 {
1018         pcpu_devices[0].address = stap();
1019         S390_lowcore.cpu_nr = 0;
1020         S390_lowcore.spinlock_lockval = arch_spin_lockval(0);
1021         S390_lowcore.spinlock_index = 0;
1022 }
1023
1024 /*
1025  * the frequency of the profiling timer can be changed
1026  * by writing a multiplier value into /proc/profile.
1027  *
1028  * usually you want to run this on all CPUs ;)
1029  */
1030 int setup_profiling_timer(unsigned int multiplier)
1031 {
1032         return 0;
1033 }
1034
1035 static ssize_t cpu_configure_show(struct device *dev,
1036                                   struct device_attribute *attr, char *buf)
1037 {
1038         ssize_t count;
1039
1040         mutex_lock(&smp_cpu_state_mutex);
1041         count = sprintf(buf, "%d\n", pcpu_devices[dev->id].state);
1042         mutex_unlock(&smp_cpu_state_mutex);
1043         return count;
1044 }
1045
1046 static ssize_t cpu_configure_store(struct device *dev,
1047                                    struct device_attribute *attr,
1048                                    const char *buf, size_t count)
1049 {
1050         struct pcpu *pcpu;
1051         int cpu, val, rc, i;
1052         char delim;
1053
1054         if (sscanf(buf, "%d %c", &val, &delim) != 1)
1055                 return -EINVAL;
1056         if (val != 0 && val != 1)
1057                 return -EINVAL;
1058         get_online_cpus();
1059         mutex_lock(&smp_cpu_state_mutex);
1060         rc = -EBUSY;
1061         /* disallow configuration changes of online cpus and cpu 0 */
1062         cpu = dev->id;
1063         cpu = smp_get_base_cpu(cpu);
1064         if (cpu == 0)
1065                 goto out;
1066         for (i = 0; i <= smp_cpu_mtid; i++)
1067                 if (cpu_online(cpu + i))
1068                         goto out;
1069         pcpu = pcpu_devices + cpu;
1070         rc = 0;
1071         switch (val) {
1072         case 0:
1073                 if (pcpu->state != CPU_STATE_CONFIGURED)
1074                         break;
1075                 rc = sclp_core_deconfigure(pcpu->address >> smp_cpu_mt_shift);
1076                 if (rc)
1077                         break;
1078                 for (i = 0; i <= smp_cpu_mtid; i++) {
1079                         if (cpu + i >= nr_cpu_ids || !cpu_present(cpu + i))
1080                                 continue;
1081                         pcpu[i].state = CPU_STATE_STANDBY;
1082                         smp_cpu_set_polarization(cpu + i,
1083                                                  POLARIZATION_UNKNOWN);
1084                 }
1085                 topology_expect_change();
1086                 break;
1087         case 1:
1088                 if (pcpu->state != CPU_STATE_STANDBY)
1089                         break;
1090                 rc = sclp_core_configure(pcpu->address >> smp_cpu_mt_shift);
1091                 if (rc)
1092                         break;
1093                 for (i = 0; i <= smp_cpu_mtid; i++) {
1094                         if (cpu + i >= nr_cpu_ids || !cpu_present(cpu + i))
1095                                 continue;
1096                         pcpu[i].state = CPU_STATE_CONFIGURED;
1097                         smp_cpu_set_polarization(cpu + i,
1098                                                  POLARIZATION_UNKNOWN);
1099                 }
1100                 topology_expect_change();
1101                 break;
1102         default:
1103                 break;
1104         }
1105 out:
1106         mutex_unlock(&smp_cpu_state_mutex);
1107         put_online_cpus();
1108         return rc ? rc : count;
1109 }
1110 static DEVICE_ATTR(configure, 0644, cpu_configure_show, cpu_configure_store);
1111
1112 static ssize_t show_cpu_address(struct device *dev,
1113                                 struct device_attribute *attr, char *buf)
1114 {
1115         return sprintf(buf, "%d\n", pcpu_devices[dev->id].address);
1116 }
1117 static DEVICE_ATTR(address, 0444, show_cpu_address, NULL);
1118
1119 static struct attribute *cpu_common_attrs[] = {
1120         &dev_attr_configure.attr,
1121         &dev_attr_address.attr,
1122         NULL,
1123 };
1124
1125 static struct attribute_group cpu_common_attr_group = {
1126         .attrs = cpu_common_attrs,
1127 };
1128
1129 static struct attribute *cpu_online_attrs[] = {
1130         &dev_attr_idle_count.attr,
1131         &dev_attr_idle_time_us.attr,
1132         NULL,
1133 };
1134
1135 static struct attribute_group cpu_online_attr_group = {
1136         .attrs = cpu_online_attrs,
1137 };
1138
1139 static int smp_cpu_online(unsigned int cpu)
1140 {
1141         struct device *s = &per_cpu(cpu_device, cpu)->dev;
1142
1143         return sysfs_create_group(&s->kobj, &cpu_online_attr_group);
1144 }
1145
1146 static int smp_cpu_pre_down(unsigned int cpu)
1147 {
1148         struct device *s = &per_cpu(cpu_device, cpu)->dev;
1149
1150         sysfs_remove_group(&s->kobj, &cpu_online_attr_group);
1151         return 0;
1152 }
1153
1154 static int smp_add_present_cpu(int cpu)
1155 {
1156         struct device *s;
1157         struct cpu *c;
1158         int rc;
1159
1160         c = kzalloc(sizeof(*c), GFP_KERNEL);
1161         if (!c)
1162                 return -ENOMEM;
1163         per_cpu(cpu_device, cpu) = c;
1164         s = &c->dev;
1165         c->hotpluggable = 1;
1166         rc = register_cpu(c, cpu);
1167         if (rc)
1168                 goto out;
1169         rc = sysfs_create_group(&s->kobj, &cpu_common_attr_group);
1170         if (rc)
1171                 goto out_cpu;
1172         rc = topology_cpu_init(c);
1173         if (rc)
1174                 goto out_topology;
1175         return 0;
1176
1177 out_topology:
1178         sysfs_remove_group(&s->kobj, &cpu_common_attr_group);
1179 out_cpu:
1180         unregister_cpu(c);
1181 out:
1182         return rc;
1183 }
1184
1185 int __ref smp_rescan_cpus(void)
1186 {
1187         struct sclp_core_info *info;
1188         int nr;
1189
1190         info = kzalloc(sizeof(*info), GFP_KERNEL);
1191         if (!info)
1192                 return -ENOMEM;
1193         smp_get_core_info(info, 0);
1194         get_online_cpus();
1195         mutex_lock(&smp_cpu_state_mutex);
1196         nr = __smp_rescan_cpus(info, false);
1197         mutex_unlock(&smp_cpu_state_mutex);
1198         put_online_cpus();
1199         kfree(info);
1200         if (nr)
1201                 topology_schedule_update();
1202         return 0;
1203 }
1204
1205 static ssize_t __ref rescan_store(struct device *dev,
1206                                   struct device_attribute *attr,
1207                                   const char *buf,
1208                                   size_t count)
1209 {
1210         int rc;
1211
1212         rc = lock_device_hotplug_sysfs();
1213         if (rc)
1214                 return rc;
1215         rc = smp_rescan_cpus();
1216         unlock_device_hotplug();
1217         return rc ? rc : count;
1218 }
1219 static DEVICE_ATTR_WO(rescan);
1220
1221 static int __init s390_smp_init(void)
1222 {
1223         int cpu, rc = 0;
1224
1225         rc = device_create_file(cpu_subsys.dev_root, &dev_attr_rescan);
1226         if (rc)
1227                 return rc;
1228         for_each_present_cpu(cpu) {
1229                 rc = smp_add_present_cpu(cpu);
1230                 if (rc)
1231                         goto out;
1232         }
1233
1234         rc = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "s390/smp:online",
1235                                smp_cpu_online, smp_cpu_pre_down);
1236         rc = rc <= 0 ? rc : 0;
1237 out:
1238         return rc;
1239 }
1240 subsys_initcall(s390_smp_init);