arch/x86/xen/smp.c

   1 /*
   2  * Xen SMP support
   3  *
   4  * This file implements the Xen versions of smp_ops.  SMP under Xen is
   5  * very straightforward.  Bringing a CPU up is simply a matter of
   6  * loading its initial context and setting it running.
   7  *
   8  * IPIs are handled through the Xen event mechanism.
   9  *
  10  * Because virtual CPUs can be scheduled onto any real CPU, there's no
  11  * useful topology information for the kernel to make use of.  As a
  12  * result, all CPUs are treated as if they're single-core and
  13  * single-threaded.
  14  */
  15 #include <linux/sched.h>
  16 #include <linux/err.h>
  17 #include <linux/slab.h>
  18 #include <linux/smp.h>
  19
  20 #include <asm/paravirt.h>
  21 #include <asm/desc.h>
  22 #include <asm/pgtable.h>
  23 #include <asm/cpu.h>
  24
  25 #include <xen/interface/xen.h>
  26 #include <xen/interface/vcpu.h>
  27
  28 #include <asm/xen/interface.h>
  29 #include <asm/xen/hypercall.h>
  30
  31 #include <xen/xen.h>
  32 #include <xen/page.h>
  33 #include <xen/events.h>
  34
  35 #include <xen/hvc-console.h>
  36 #include "xen-ops.h"
  37 #include "mmu.h"
  38
  39 cpumask_var_t xen_cpu_initialized_map;
  40
  41 static DEFINE_PER_CPU(int, xen_resched_irq);
  42 static DEFINE_PER_CPU(int, xen_callfunc_irq);
  43 static DEFINE_PER_CPU(int, xen_callfuncsingle_irq);
  44 static DEFINE_PER_CPU(int, xen_debug_irq) = -1;
  45
  46 static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id);
  47 static irqreturn_t xen_call_function_single_interrupt(int irq, void *dev_id);
  48
  49 /*
  50  * Reschedule call back.
  51  */
  52 static irqreturn_t xen_reschedule_interrupt(int irq, void *dev_id)
  53 {
  54         inc_irq_stat(irq_resched_count);
  55         scheduler_ipi();
  56
  57         return IRQ_HANDLED;
  58 }
  59
  60 static void __cpuinit cpu_bringup(void)
  61 {
  62         int cpu;
  63
  64         cpu_init();
  65         touch_softlockup_watchdog();
  66         preempt_disable();
  67
  68         xen_enable_sysenter();
  69         xen_enable_syscall();
  70
  71         cpu = smp_processor_id();
  72         smp_store_cpu_info(cpu);
  73         cpu_data(cpu).x86_max_cores = 1;
  74         set_cpu_sibling_map(cpu);
  75
  76         xen_setup_cpu_clockevents();
  77
  78         notify_cpu_starting(cpu);
  79
  80         ipi_call_lock();
  81         set_cpu_online(cpu, true);
  82         ipi_call_unlock();
  83
  84         this_cpu_write(cpu_state, CPU_ONLINE);
  85
  86         wmb();
  87
  88         /* We can take interrupts now: we're officially "up". */
  89         local_irq_enable();
  90
  91         wmb();                  /* make sure everything is out */
  92 }
  93
  94 static void __cpuinit cpu_bringup_and_idle(void)
  95 {
  96         cpu_bringup();
  97         cpu_idle();
  98 }
  99
 100 static int xen_smp_intr_init(unsigned int cpu)
 101 {
 102         int rc;
 103         const char *resched_name, *callfunc_name, *debug_name;
 104
 105         resched_name = kasprintf(GFP_KERNEL, "resched%d", cpu);
 106         rc = bind_ipi_to_irqhandler(XEN_RESCHEDULE_VECTOR,
 107                                     cpu,
 108                                     xen_reschedule_interrupt,
 109                                     IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
 110                                     resched_name,
 111                                     NULL);
 112         if (rc < 0)
 113                 goto fail;
 114         per_cpu(xen_resched_irq, cpu) = rc;
 115
 116         callfunc_name = kasprintf(GFP_KERNEL, "callfunc%d", cpu);
 117         rc = bind_ipi_to_irqhandler(XEN_CALL_FUNCTION_VECTOR,
 118                                     cpu,
 119                                     xen_call_function_interrupt,
 120                                     IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
 121                                     callfunc_name,
 122                                     NULL);
 123         if (rc < 0)
 124                 goto fail;
 125         per_cpu(xen_callfunc_irq, cpu) = rc;
 126
 127         debug_name = kasprintf(GFP_KERNEL, "debug%d", cpu);
 128         rc = bind_virq_to_irqhandler(VIRQ_DEBUG, cpu, xen_debug_interrupt,
 129                                      IRQF_DISABLED | IRQF_PERCPU | IRQF_NOBALANCING,
 130                                      debug_name, NULL);
 131         if (rc < 0)
 132                 goto fail;
 133         per_cpu(xen_debug_irq, cpu) = rc;
 134
 135         callfunc_name = kasprintf(GFP_KERNEL, "callfuncsingle%d", cpu);
 136         rc = bind_ipi_to_irqhandler(XEN_CALL_FUNCTION_SINGLE_VECTOR,
 137                                     cpu,
 138                                     xen_call_function_single_interrupt,
 139                                     IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
 140                                     callfunc_name,
 141                                     NULL);
 142         if (rc < 0)
 143                 goto fail;
 144         per_cpu(xen_callfuncsingle_irq, cpu) = rc;
 145
 146         return 0;
 147
 148  fail:
 149         if (per_cpu(xen_resched_irq, cpu) >= 0)
 150                 unbind_from_irqhandler(per_cpu(xen_resched_irq, cpu), NULL);
 151         if (per_cpu(xen_callfunc_irq, cpu) >= 0)
 152                 unbind_from_irqhandler(per_cpu(xen_callfunc_irq, cpu), NULL);
 153         if (per_cpu(xen_debug_irq, cpu) >= 0)
 154                 unbind_from_irqhandler(per_cpu(xen_debug_irq, cpu), NULL);
 155         if (per_cpu(xen_callfuncsingle_irq, cpu) >= 0)
 156                 unbind_from_irqhandler(per_cpu(xen_callfuncsingle_irq, cpu),
 157                                        NULL);
 158
 159         return rc;
 160 }
 161
 162 static void __init xen_fill_possible_map(void)
 163 {
 164         int i, rc;
 165
 166         if (xen_initial_domain())
 167                 return;
 168
 169         for (i = 0; i < nr_cpu_ids; i++) {
 170                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 171                 if (rc >= 0) {
 172                         num_processors++;
 173                         set_cpu_possible(i, true);
 174                 }
 175         }
 176 }
 177
 178 static void __init xen_filter_cpu_maps(void)
 179 {
 180         int i, rc;
 181         unsigned int subtract = 0;
 182
 183         if (!xen_initial_domain())
 184                 return;
 185
 186         num_processors = 0;
 187         disabled_cpus = 0;
 188         for (i = 0; i < nr_cpu_ids; i++) {
 189                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 190                 if (rc >= 0) {
 191                         num_processors++;
 192                         set_cpu_possible(i, true);
 193                 } else {
 194                         set_cpu_possible(i, false);
 195                         set_cpu_present(i, false);
 196                         subtract++;
 197                 }
 198         }
 199 #ifdef CONFIG_HOTPLUG_CPU
 200         /* This is akin to using 'nr_cpus' on the Linux command line.
 201          * Which is OK as when we use 'dom0_max_vcpus=X' we can only
 202          * have up to X, while nr_cpu_ids is greater than X. This
 203          * normally is not a problem, except when CPU hotplugging
 204          * is involved and then there might be more than X CPUs
 205          * in the guest - which will not work as there is no
 206          * hypercall to expand the max number of VCPUs an already
 207          * running guest has. So cap it up to X. */
 208         if (subtract)
 209                 nr_cpu_ids = nr_cpu_ids - subtract;
 210 #endif
 211
 212 }
 213
 214 static void __init xen_smp_prepare_boot_cpu(void)
 215 {
 216         BUG_ON(smp_processor_id() != 0);
 217         native_smp_prepare_boot_cpu();
 218
 219         /* We've switched to the "real" per-cpu gdt, so make sure the
 220            old memory can be recycled */
 221         make_lowmem_page_readwrite(xen_initial_gdt);
 222
 223         xen_filter_cpu_maps();
 224         xen_setup_vcpu_info_placement();
 225 }
 226
 227 static void __init xen_smp_prepare_cpus(unsigned int max_cpus)
 228 {
 229         unsigned cpu;
 230         unsigned int i;
 231
 232         if (skip_ioapic_setup) {
 233                 char *m = (max_cpus == 0) ?
 234                         "The nosmp parameter is incompatible with Xen; " \
 235                         "use Xen dom0_max_vcpus=1 parameter" :
 236                         "The noapic parameter is incompatible with Xen";
 237
 238                 xen_raw_printk(m);
 239                 panic(m);
 240         }
 241         xen_init_lock_cpu(0);
 242
 243         smp_store_cpu_info(0);
 244         cpu_data(0).x86_max_cores = 1;
 245
 246         for_each_possible_cpu(i) {
 247                 zalloc_cpumask_var(&per_cpu(cpu_sibling_map, i), GFP_KERNEL);
 248                 zalloc_cpumask_var(&per_cpu(cpu_core_map, i), GFP_KERNEL);
 249                 zalloc_cpumask_var(&per_cpu(cpu_llc_shared_map, i), GFP_KERNEL);
 250         }
 251         set_cpu_sibling_map(0);
 252
 253         if (xen_smp_intr_init(0))
 254                 BUG();
 255
 256         if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
 257                 panic("could not allocate xen_cpu_initialized_map\n");
 258
 259         cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));
 260
 261         /* Restrict the possible_map according to max_cpus. */
 262         while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
 263                 for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
 264                         continue;
 265                 set_cpu_possible(cpu, false);
 266         }
 267
 268         for_each_possible_cpu (cpu) {
 269                 struct task_struct *idle;
 270
 271                 if (cpu == 0)
 272                         continue;
 273
 274                 idle = fork_idle(cpu);
 275                 if (IS_ERR(idle))
 276                         panic("failed fork for CPU %d", cpu);
 277
 278                 set_cpu_present(cpu, true);
 279         }
 280 }
 281
 282 static int __cpuinit
 283 cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
 284 {
 285         struct vcpu_guest_context *ctxt;
 286         struct desc_struct *gdt;
 287         unsigned long gdt_mfn;
 288
 289         if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
 290                 return 0;
 291
 292         ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
 293         if (ctxt == NULL)
 294                 return -ENOMEM;
 295
 296         gdt = get_cpu_gdt_table(cpu);
 297
 298         ctxt->flags = VGCF_IN_KERNEL;
 299         ctxt->user_regs.ds = __USER_DS;
 300         ctxt->user_regs.es = __USER_DS;
 301         ctxt->user_regs.ss = __KERNEL_DS;
 302 #ifdef CONFIG_X86_32
 303         ctxt->user_regs.fs = __KERNEL_PERCPU;
 304         ctxt->user_regs.gs = __KERNEL_STACK_CANARY;
 305 #else
 306         ctxt->gs_base_kernel = per_cpu_offset(cpu);
 307 #endif
 308         ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
 309         ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
 310
 311         memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));
 312
 313         xen_copy_trap_info(ctxt->trap_ctxt);
 314
 315         ctxt->ldt_ents = 0;
 316
 317         BUG_ON((unsigned long)gdt & ~PAGE_MASK);
 318
 319         gdt_mfn = arbitrary_virt_to_mfn(gdt);
 320         make_lowmem_page_readonly(gdt);
 321         make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));
 322
 323         ctxt->gdt_frames[0] = gdt_mfn;
 324         ctxt->gdt_ents      = GDT_ENTRIES;
 325
 326         ctxt->user_regs.cs = __KERNEL_CS;
 327         ctxt->user_regs.esp = idle->thread.sp0 - sizeof(struct pt_regs);
 328
 329         ctxt->kernel_ss = __KERNEL_DS;
 330         ctxt->kernel_sp = idle->thread.sp0;
 331
 332 #ifdef CONFIG_X86_32
 333         ctxt->event_callback_cs     = __KERNEL_CS;
 334         ctxt->failsafe_callback_cs  = __KERNEL_CS;
 335 #endif
 336         ctxt->event_callback_eip    = (unsigned long)xen_hypervisor_callback;
 337         ctxt->failsafe_callback_eip = (unsigned long)xen_failsafe_callback;
 338
 339         per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
 340         ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir));
 341
 342         if (HYPERVISOR_vcpu_op(VCPUOP_initialise, cpu, ctxt))
 343                 BUG();
 344
 345         kfree(ctxt);
 346         return 0;
 347 }
 348
 349 static int __cpuinit xen_cpu_up(unsigned int cpu)
 350 {
 351         struct task_struct *idle = idle_task(cpu);
 352         int rc;
 353
 354         per_cpu(current_task, cpu) = idle;
 355 #ifdef CONFIG_X86_32
 356         irq_ctx_init(cpu);
 357 #else
 358         clear_tsk_thread_flag(idle, TIF_FORK);
 359         per_cpu(kernel_stack, cpu) =
 360                 (unsigned long)task_stack_page(idle) -
 361                 KERNEL_STACK_OFFSET + THREAD_SIZE;
 362 #endif
 363         xen_setup_runstate_info(cpu);
 364         xen_setup_timer(cpu);
 365         xen_init_lock_cpu(cpu);
 366
 367         per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;
 368
 369         /* make sure interrupts start blocked */
 370         per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
 371
 372         rc = cpu_initialize_context(cpu, idle);
 373         if (rc)
 374                 return rc;
 375
 376         if (num_online_cpus() == 1)
 377                 alternatives_smp_switch(1);
 378
 379         rc = xen_smp_intr_init(cpu);
 380         if (rc)
 381                 return rc;
 382
 383         rc = HYPERVISOR_vcpu_op(VCPUOP_up, cpu, NULL);
 384         BUG_ON(rc);
 385
 386         while(per_cpu(cpu_state, cpu) != CPU_ONLINE) {
 387                 HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
 388                 barrier();
 389         }
 390
 391         return 0;
 392 }
 393
 394 static void xen_smp_cpus_done(unsigned int max_cpus)
 395 {
 396 }
 397
 398 #ifdef CONFIG_HOTPLUG_CPU
 399 static int xen_cpu_disable(void)
 400 {
 401         unsigned int cpu = smp_processor_id();
 402         if (cpu == 0)
 403                 return -EBUSY;
 404
 405         cpu_disable_common();
 406
 407         load_cr3(swapper_pg_dir);
 408         return 0;
 409 }
 410
 411 static void xen_cpu_die(unsigned int cpu)
 412 {
 413         while (HYPERVISOR_vcpu_op(VCPUOP_is_up, cpu, NULL)) {
 414                 current->state = TASK_UNINTERRUPTIBLE;
 415                 schedule_timeout(HZ/10);
 416         }
 417         unbind_from_irqhandler(per_cpu(xen_resched_irq, cpu), NULL);
 418         unbind_from_irqhandler(per_cpu(xen_callfunc_irq, cpu), NULL);
 419         unbind_from_irqhandler(per_cpu(xen_debug_irq, cpu), NULL);
 420         unbind_from_irqhandler(per_cpu(xen_callfuncsingle_irq, cpu), NULL);
 421         xen_uninit_lock_cpu(cpu);
 422         xen_teardown_timer(cpu);
 423
 424         if (num_online_cpus() == 1)
 425                 alternatives_smp_switch(0);
 426 }
 427
 428 static void __cpuinit xen_play_dead(void) /* used only with HOTPLUG_CPU */
 429 {
 430         play_dead_common();
 431         HYPERVISOR_vcpu_op(VCPUOP_down, smp_processor_id(), NULL);
 432         cpu_bringup();
 433         /*
 434          * Balance out the preempt calls - as we are running in cpu_idle
 435          * loop which has been called at bootup from cpu_bringup_and_idle.
 436          * The cpucpu_bringup_and_idle called cpu_bringup which made a
 437          * preempt_disable() So this preempt_enable will balance it out.
 438          */
 439         preempt_enable();
 440 }
 441
 442 #else /* !CONFIG_HOTPLUG_CPU */
 443 static int xen_cpu_disable(void)
 444 {
 445         return -ENOSYS;
 446 }
 447
 448 static void xen_cpu_die(unsigned int cpu)
 449 {
 450         BUG();
 451 }
 452
 453 static void xen_play_dead(void)
 454 {
 455         BUG();
 456 }
 457
 458 #endif
 459 static void stop_self(void *v)
 460 {
 461         int cpu = smp_processor_id();
 462
 463         /* make sure we're not pinning something down */
 464         load_cr3(swapper_pg_dir);
 465         /* should set up a minimal gdt */
 466
 467         set_cpu_online(cpu, false);
 468
 469         HYPERVISOR_vcpu_op(VCPUOP_down, cpu, NULL);
 470         BUG();
 471 }
 472
 473 static void xen_stop_other_cpus(int wait)
 474 {
 475         smp_call_function(stop_self, NULL, wait);
 476 }
 477
 478 static void xen_smp_send_reschedule(int cpu)
 479 {
 480         xen_send_IPI_one(cpu, XEN_RESCHEDULE_VECTOR);
 481 }
 482
 483 static void xen_send_IPI_mask(const struct cpumask *mask,
 484                               enum ipi_vector vector)
 485 {
 486         unsigned cpu;
 487
 488         for_each_cpu_and(cpu, mask, cpu_online_mask)
 489                 xen_send_IPI_one(cpu, vector);
 490 }
 491
 492 static void xen_smp_send_call_function_ipi(const struct cpumask *mask)
 493 {
 494         int cpu;
 495
 496         xen_send_IPI_mask(mask, XEN_CALL_FUNCTION_VECTOR);
 497
 498         /* Make sure other vcpus get a chance to run if they need to. */
 499         for_each_cpu(cpu, mask) {
 500                 if (xen_vcpu_stolen(cpu)) {
 501                         HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
 502                         break;
 503                 }
 504         }
 505 }
 506
 507 static void xen_smp_send_call_function_single_ipi(int cpu)
 508 {
 509         xen_send_IPI_mask(cpumask_of(cpu),
 510                           XEN_CALL_FUNCTION_SINGLE_VECTOR);
 511 }
 512
 513 static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id)
 514 {
 515         irq_enter();
 516         generic_smp_call_function_interrupt();
 517         inc_irq_stat(irq_call_count);
 518         irq_exit();
 519
 520         return IRQ_HANDLED;
 521 }
 522
 523 static irqreturn_t xen_call_function_single_interrupt(int irq, void *dev_id)
 524 {
 525         irq_enter();
 526         generic_smp_call_function_single_interrupt();
 527         inc_irq_stat(irq_call_count);
 528         irq_exit();
 529
 530         return IRQ_HANDLED;
 531 }
 532
 533 static const struct smp_ops xen_smp_ops __initconst = {
 534         .smp_prepare_boot_cpu = xen_smp_prepare_boot_cpu,
 535         .smp_prepare_cpus = xen_smp_prepare_cpus,
 536         .smp_cpus_done = xen_smp_cpus_done,
 537
 538         .cpu_up = xen_cpu_up,
 539         .cpu_die = xen_cpu_die,
 540         .cpu_disable = xen_cpu_disable,
 541         .play_dead = xen_play_dead,
 542
 543         .stop_other_cpus = xen_stop_other_cpus,
 544         .smp_send_reschedule = xen_smp_send_reschedule,
 545
 546         .send_call_func_ipi = xen_smp_send_call_function_ipi,
 547         .send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
 548 };
 549
 550 void __init xen_smp_init(void)
 551 {
 552         smp_ops = xen_smp_ops;
 553         xen_fill_possible_map();
 554         xen_init_spinlocks();
 555 }
 556
 557 static void __init xen_hvm_smp_prepare_cpus(unsigned int max_cpus)
 558 {
 559         native_smp_prepare_cpus(max_cpus);
 560         WARN_ON(xen_smp_intr_init(0));
 561
 562         xen_init_lock_cpu(0);
 563 }
 564
 565 static int __cpuinit xen_hvm_cpu_up(unsigned int cpu)
 566 {
 567         int rc;
 568         rc = native_cpu_up(cpu);
 569         WARN_ON (xen_smp_intr_init(cpu));
 570         return rc;
 571 }
 572
 573 static void xen_hvm_cpu_die(unsigned int cpu)
 574 {
 575         unbind_from_irqhandler(per_cpu(xen_resched_irq, cpu), NULL);
 576         unbind_from_irqhandler(per_cpu(xen_callfunc_irq, cpu), NULL);
 577         unbind_from_irqhandler(per_cpu(xen_debug_irq, cpu), NULL);
 578         unbind_from_irqhandler(per_cpu(xen_callfuncsingle_irq, cpu), NULL);
 579         native_cpu_die(cpu);
 580 }
 581
 582 void __init xen_hvm_smp_init(void)
 583 {
 584         if (!xen_have_vector_callback)
 585                 return;
 586         smp_ops.smp_prepare_cpus = xen_hvm_smp_prepare_cpus;
 587         smp_ops.smp_send_reschedule = xen_smp_send_reschedule;
 588         smp_ops.cpu_up = xen_hvm_cpu_up;
 589         smp_ops.cpu_die = xen_hvm_cpu_die;
 590         smp_ops.send_call_func_ipi = xen_smp_send_call_function_ipi;
 591         smp_ops.send_call_func_single_ipi = xen_smp_send_call_function_single_ipi;
 592 }