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  * This does not handle HOTPLUG_CPU yet.
  16  */
  17 #include <linux/sched.h>
  18 #include <linux/kernel_stat.h>
  19 #include <linux/err.h>
  20 #include <linux/smp.h>
  21
  22 #include <asm/paravirt.h>
  23 #include <asm/desc.h>
  24 #include <asm/pgtable.h>
  25 #include <asm/cpu.h>
  26
  27 #include <xen/interface/xen.h>
  28 #include <xen/interface/vcpu.h>
  29
  30 #include <asm/xen/interface.h>
  31 #include <asm/xen/hypercall.h>
  32
  33 #include <xen/page.h>
  34 #include <xen/events.h>
  35
  36 #include "xen-ops.h"
  37 #include "mmu.h"
  38
  39 static void __cpuinit xen_init_lock_cpu(int cpu);
  40
  41 cpumask_t xen_cpu_initialized_map;
  42
  43 static DEFINE_PER_CPU(int, resched_irq);
  44 static DEFINE_PER_CPU(int, callfunc_irq);
  45 static DEFINE_PER_CPU(int, callfuncsingle_irq);
  46 static DEFINE_PER_CPU(int, debug_irq) = -1;
  47
  48 static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id);
  49 static irqreturn_t xen_call_function_single_interrupt(int irq, void *dev_id);
  50
  51 /*
  52  * Reschedule call back. Nothing to do,
  53  * all the work is done automatically when
  54  * we return from the interrupt.
  55  */
  56 static irqreturn_t xen_reschedule_interrupt(int irq, void *dev_id)
  57 {
  58 #ifdef CONFIG_X86_32
  59         __get_cpu_var(irq_stat).irq_resched_count++;
  60 #else
  61         add_pda(irq_resched_count, 1);
  62 #endif
  63
  64         return IRQ_HANDLED;
  65 }
  66
  67 static __cpuinit void cpu_bringup_and_idle(void)
  68 {
  69         int cpu = smp_processor_id();
  70
  71         cpu_init();
  72         preempt_disable();
  73
  74         xen_enable_sysenter();
  75         xen_enable_syscall();
  76
  77         cpu = smp_processor_id();
  78         smp_store_cpu_info(cpu);
  79         cpu_data(cpu).x86_max_cores = 1;
  80         set_cpu_sibling_map(cpu);
  81
  82         xen_setup_cpu_clockevents();
  83
  84         cpu_set(cpu, cpu_online_map);
  85         x86_write_percpu(cpu_state, CPU_ONLINE);
  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         cpu_idle();
  93 }
  94
  95 static int xen_smp_intr_init(unsigned int cpu)
  96 {
  97         int rc;
  98         const char *resched_name, *callfunc_name, *debug_name;
  99
 100         resched_name = kasprintf(GFP_KERNEL, "resched%d", cpu);
 101         rc = bind_ipi_to_irqhandler(XEN_RESCHEDULE_VECTOR,
 102                                     cpu,
 103                                     xen_reschedule_interrupt,
 104                                     IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
 105                                     resched_name,
 106                                     NULL);
 107         if (rc < 0)
 108                 goto fail;
 109         per_cpu(resched_irq, cpu) = rc;
 110
 111         callfunc_name = kasprintf(GFP_KERNEL, "callfunc%d", cpu);
 112         rc = bind_ipi_to_irqhandler(XEN_CALL_FUNCTION_VECTOR,
 113                                     cpu,
 114                                     xen_call_function_interrupt,
 115                                     IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
 116                                     callfunc_name,
 117                                     NULL);
 118         if (rc < 0)
 119                 goto fail;
 120         per_cpu(callfunc_irq, cpu) = rc;
 121
 122         debug_name = kasprintf(GFP_KERNEL, "debug%d", cpu);
 123         rc = bind_virq_to_irqhandler(VIRQ_DEBUG, cpu, xen_debug_interrupt,
 124                                      IRQF_DISABLED | IRQF_PERCPU | IRQF_NOBALANCING,
 125                                      debug_name, NULL);
 126         if (rc < 0)
 127                 goto fail;
 128         per_cpu(debug_irq, cpu) = rc;
 129
 130         callfunc_name = kasprintf(GFP_KERNEL, "callfuncsingle%d", cpu);
 131         rc = bind_ipi_to_irqhandler(XEN_CALL_FUNCTION_SINGLE_VECTOR,
 132                                     cpu,
 133                                     xen_call_function_single_interrupt,
 134                                     IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
 135                                     callfunc_name,
 136                                     NULL);
 137         if (rc < 0)
 138                 goto fail;
 139         per_cpu(callfuncsingle_irq, cpu) = rc;
 140
 141         return 0;
 142
 143  fail:
 144         if (per_cpu(resched_irq, cpu) >= 0)
 145                 unbind_from_irqhandler(per_cpu(resched_irq, cpu), NULL);
 146         if (per_cpu(callfunc_irq, cpu) >= 0)
 147                 unbind_from_irqhandler(per_cpu(callfunc_irq, cpu), NULL);
 148         if (per_cpu(debug_irq, cpu) >= 0)
 149                 unbind_from_irqhandler(per_cpu(debug_irq, cpu), NULL);
 150         if (per_cpu(callfuncsingle_irq, cpu) >= 0)
 151                 unbind_from_irqhandler(per_cpu(callfuncsingle_irq, cpu), NULL);
 152
 153         return rc;
 154 }
 155
 156 static void __init xen_fill_possible_map(void)
 157 {
 158         int i, rc;
 159
 160         for (i = 0; i < NR_CPUS; i++) {
 161                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
 162                 if (rc >= 0) {
 163                         num_processors++;
 164                         cpu_set(i, cpu_possible_map);
 165                 }
 166         }
 167 }
 168
 169 static void __init xen_smp_prepare_boot_cpu(void)
 170 {
 171         BUG_ON(smp_processor_id() != 0);
 172         native_smp_prepare_boot_cpu();
 173
 174         /* We've switched to the "real" per-cpu gdt, so make sure the
 175            old memory can be recycled */
 176         make_lowmem_page_readwrite(&per_cpu_var(gdt_page));
 177
 178         xen_setup_vcpu_info_placement();
 179 }
 180
 181 static void __init xen_smp_prepare_cpus(unsigned int max_cpus)
 182 {
 183         unsigned cpu;
 184
 185         xen_init_lock_cpu(0);
 186
 187         smp_store_cpu_info(0);
 188         cpu_data(0).x86_max_cores = 1;
 189         set_cpu_sibling_map(0);
 190
 191         if (xen_smp_intr_init(0))
 192                 BUG();
 193
 194         xen_cpu_initialized_map = cpumask_of_cpu(0);
 195
 196         /* Restrict the possible_map according to max_cpus. */
 197         while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
 198                 for (cpu = NR_CPUS - 1; !cpu_possible(cpu); cpu--)
 199                         continue;
 200                 cpu_clear(cpu, cpu_possible_map);
 201         }
 202
 203         for_each_possible_cpu (cpu) {
 204                 struct task_struct *idle;
 205
 206                 if (cpu == 0)
 207                         continue;
 208
 209                 idle = fork_idle(cpu);
 210                 if (IS_ERR(idle))
 211                         panic("failed fork for CPU %d", cpu);
 212
 213                 cpu_set(cpu, cpu_present_map);
 214         }
 215
 216         //init_xenbus_allowed_cpumask();
 217 }
 218
 219 static __cpuinit int
 220 cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
 221 {
 222         struct vcpu_guest_context *ctxt;
 223         struct desc_struct *gdt;
 224
 225         if (cpu_test_and_set(cpu, xen_cpu_initialized_map))
 226                 return 0;
 227
 228         ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
 229         if (ctxt == NULL)
 230                 return -ENOMEM;
 231
 232         gdt = get_cpu_gdt_table(cpu);
 233
 234         ctxt->flags = VGCF_IN_KERNEL;
 235         ctxt->user_regs.ds = __USER_DS;
 236         ctxt->user_regs.es = __USER_DS;
 237         ctxt->user_regs.ss = __KERNEL_DS;
 238 #ifdef CONFIG_X86_32
 239         ctxt->user_regs.fs = __KERNEL_PERCPU;
 240 #endif
 241         ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
 242         ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
 243
 244         memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));
 245
 246         xen_copy_trap_info(ctxt->trap_ctxt);
 247
 248         ctxt->ldt_ents = 0;
 249
 250         BUG_ON((unsigned long)gdt & ~PAGE_MASK);
 251         make_lowmem_page_readonly(gdt);
 252
 253         ctxt->gdt_frames[0] = virt_to_mfn(gdt);
 254         ctxt->gdt_ents      = GDT_ENTRIES;
 255
 256         ctxt->user_regs.cs = __KERNEL_CS;
 257         ctxt->user_regs.esp = idle->thread.sp0 - sizeof(struct pt_regs);
 258
 259         ctxt->kernel_ss = __KERNEL_DS;
 260         ctxt->kernel_sp = idle->thread.sp0;
 261
 262 #ifdef CONFIG_X86_32
 263         ctxt->event_callback_cs     = __KERNEL_CS;
 264         ctxt->failsafe_callback_cs  = __KERNEL_CS;
 265 #endif
 266         ctxt->event_callback_eip    = (unsigned long)xen_hypervisor_callback;
 267         ctxt->failsafe_callback_eip = (unsigned long)xen_failsafe_callback;
 268
 269         per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
 270         ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir));
 271
 272         if (HYPERVISOR_vcpu_op(VCPUOP_initialise, cpu, ctxt))
 273                 BUG();
 274
 275         kfree(ctxt);
 276         return 0;
 277 }
 278
 279 static int __cpuinit xen_cpu_up(unsigned int cpu)
 280 {
 281         struct task_struct *idle = idle_task(cpu);
 282         int rc;
 283
 284 #if 0
 285         rc = cpu_up_check(cpu);
 286         if (rc)
 287                 return rc;
 288 #endif
 289
 290 #ifdef CONFIG_X86_64
 291         /* Allocate node local memory for AP pdas */
 292         WARN_ON(cpu == 0);
 293         if (cpu > 0) {
 294                 rc = get_local_pda(cpu);
 295                 if (rc)
 296                         return rc;
 297         }
 298 #endif
 299
 300 #ifdef CONFIG_X86_32
 301         init_gdt(cpu);
 302         per_cpu(current_task, cpu) = idle;
 303         irq_ctx_init(cpu);
 304 #else
 305         cpu_pda(cpu)->pcurrent = idle;
 306         clear_tsk_thread_flag(idle, TIF_FORK);
 307 #endif
 308         xen_setup_timer(cpu);
 309         xen_init_lock_cpu(cpu);
 310
 311         per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;
 312
 313         /* make sure interrupts start blocked */
 314         per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
 315
 316         rc = cpu_initialize_context(cpu, idle);
 317         if (rc)
 318                 return rc;
 319
 320         if (num_online_cpus() == 1)
 321                 alternatives_smp_switch(1);
 322
 323         rc = xen_smp_intr_init(cpu);
 324         if (rc)
 325                 return rc;
 326
 327         rc = HYPERVISOR_vcpu_op(VCPUOP_up, cpu, NULL);
 328         BUG_ON(rc);
 329
 330         while(per_cpu(cpu_state, cpu) != CPU_ONLINE) {
 331                 HYPERVISOR_sched_op(SCHEDOP_yield, 0);
 332                 barrier();
 333         }
 334
 335         return 0;
 336 }
 337
 338 static void xen_smp_cpus_done(unsigned int max_cpus)
 339 {
 340 }
 341
 342 static void stop_self(void *v)
 343 {
 344         int cpu = smp_processor_id();
 345
 346         /* make sure we're not pinning something down */
 347         load_cr3(swapper_pg_dir);
 348         /* should set up a minimal gdt */
 349
 350         HYPERVISOR_vcpu_op(VCPUOP_down, cpu, NULL);
 351         BUG();
 352 }
 353
 354 static void xen_smp_send_stop(void)
 355 {
 356         smp_call_function(stop_self, NULL, 0);
 357 }
 358
 359 static void xen_smp_send_reschedule(int cpu)
 360 {
 361         xen_send_IPI_one(cpu, XEN_RESCHEDULE_VECTOR);
 362 }
 363
 364 static void xen_send_IPI_mask(cpumask_t mask, enum ipi_vector vector)
 365 {
 366         unsigned cpu;
 367
 368         cpus_and(mask, mask, cpu_online_map);
 369
 370         for_each_cpu_mask_nr(cpu, mask)
 371                 xen_send_IPI_one(cpu, vector);
 372 }
 373
 374 static void xen_smp_send_call_function_ipi(cpumask_t mask)
 375 {
 376         int cpu;
 377
 378         xen_send_IPI_mask(mask, XEN_CALL_FUNCTION_VECTOR);
 379
 380         /* Make sure other vcpus get a chance to run if they need to. */
 381         for_each_cpu_mask_nr(cpu, mask) {
 382                 if (xen_vcpu_stolen(cpu)) {
 383                         HYPERVISOR_sched_op(SCHEDOP_yield, 0);
 384                         break;
 385                 }
 386         }
 387 }
 388
 389 static void xen_smp_send_call_function_single_ipi(int cpu)
 390 {
 391         xen_send_IPI_mask(cpumask_of_cpu(cpu), XEN_CALL_FUNCTION_SINGLE_VECTOR);
 392 }
 393
 394 static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id)
 395 {
 396         irq_enter();
 397         generic_smp_call_function_interrupt();
 398 #ifdef CONFIG_X86_32
 399         __get_cpu_var(irq_stat).irq_call_count++;
 400 #else
 401         add_pda(irq_call_count, 1);
 402 #endif
 403         irq_exit();
 404
 405         return IRQ_HANDLED;
 406 }
 407
 408 static irqreturn_t xen_call_function_single_interrupt(int irq, void *dev_id)
 409 {
 410         irq_enter();
 411         generic_smp_call_function_single_interrupt();
 412 #ifdef CONFIG_X86_32
 413         __get_cpu_var(irq_stat).irq_call_count++;
 414 #else
 415         add_pda(irq_call_count, 1);
 416 #endif
 417         irq_exit();
 418
 419         return IRQ_HANDLED;
 420 }
 421
 422 struct xen_spinlock {
 423         unsigned char lock;             /* 0 -> free; 1 -> locked */
 424         unsigned short spinners;        /* count of waiting cpus */
 425 };
 426
 427 static int xen_spin_is_locked(struct raw_spinlock *lock)
 428 {
 429         struct xen_spinlock *xl = (struct xen_spinlock *)lock;
 430
 431         return xl->lock != 0;
 432 }
 433
 434 static int xen_spin_is_contended(struct raw_spinlock *lock)
 435 {
 436         struct xen_spinlock *xl = (struct xen_spinlock *)lock;
 437
 438         /* Not strictly true; this is only the count of contended
 439            lock-takers entering the slow path. */
 440         return xl->spinners != 0;
 441 }
 442
 443 static int xen_spin_trylock(struct raw_spinlock *lock)
 444 {
 445         struct xen_spinlock *xl = (struct xen_spinlock *)lock;
 446         u8 old = 1;
 447
 448         asm("xchgb %b0,%1"
 449             : "+q" (old), "+m" (xl->lock) : : "memory");
 450
 451         return old == 0;
 452 }
 453
 454 static DEFINE_PER_CPU(int, lock_kicker_irq) = -1;
 455 static DEFINE_PER_CPU(struct xen_spinlock *, lock_spinners);
 456
 457 static inline void spinning_lock(struct xen_spinlock *xl)
 458 {
 459         __get_cpu_var(lock_spinners) = xl;
 460         wmb();                  /* set lock of interest before count */
 461         asm(LOCK_PREFIX " incw %0"
 462             : "+m" (xl->spinners) : : "memory");
 463 }
 464
 465 static inline void unspinning_lock(struct xen_spinlock *xl)
 466 {
 467         asm(LOCK_PREFIX " decw %0"
 468             : "+m" (xl->spinners) : : "memory");
 469         wmb();                  /* decrement count before clearing lock */
 470         __get_cpu_var(lock_spinners) = NULL;
 471 }
 472
 473 static noinline int xen_spin_lock_slow(struct raw_spinlock *lock)
 474 {
 475         struct xen_spinlock *xl = (struct xen_spinlock *)lock;
 476         int irq = __get_cpu_var(lock_kicker_irq);
 477         int ret;
 478
 479         /* If kicker interrupts not initialized yet, just spin */
 480         if (irq == -1)
 481                 return 0;
 482
 483         /* announce we're spinning */
 484         spinning_lock(xl);
 485
 486         /* clear pending */
 487         xen_clear_irq_pending(irq);
 488
 489         /* check again make sure it didn't become free while
 490            we weren't looking  */
 491         ret = xen_spin_trylock(lock);
 492         if (ret)
 493                 goto out;
 494
 495         /* block until irq becomes pending */
 496         xen_poll_irq(irq);
 497         kstat_this_cpu.irqs[irq]++;
 498
 499 out:
 500         unspinning_lock(xl);
 501         return ret;
 502 }
 503
 504 static void xen_spin_lock(struct raw_spinlock *lock)
 505 {
 506         struct xen_spinlock *xl = (struct xen_spinlock *)lock;
 507         int timeout;
 508         u8 oldval;
 509
 510         do {
 511                 timeout = 1 << 10;
 512
 513                 asm("1: xchgb %1,%0\n"
 514                     "   testb %1,%1\n"
 515                     "   jz 3f\n"
 516                     "2: rep;nop\n"
 517                     "   cmpb $0,%0\n"
 518                     "   je 1b\n"
 519                     "   dec %2\n"
 520                     "   jnz 2b\n"
 521                     "3:\n"
 522                     : "+m" (xl->lock), "=q" (oldval), "+r" (timeout)
 523                     : "1" (1)
 524                     : "memory");
 525
 526         } while (unlikely(oldval != 0 && !xen_spin_lock_slow(lock)));
 527 }
 528
 529 static noinline void xen_spin_unlock_slow(struct xen_spinlock *xl)
 530 {
 531         int cpu;
 532
 533         for_each_online_cpu(cpu) {
 534                 /* XXX should mix up next cpu selection */
 535                 if (per_cpu(lock_spinners, cpu) == xl) {
 536                         xen_send_IPI_one(cpu, XEN_SPIN_UNLOCK_VECTOR);
 537                         break;
 538                 }
 539         }
 540 }
 541
 542 static void xen_spin_unlock(struct raw_spinlock *lock)
 543 {
 544         struct xen_spinlock *xl = (struct xen_spinlock *)lock;
 545
 546         smp_wmb();              /* make sure no writes get moved after unlock */
 547         xl->lock = 0;           /* release lock */
 548
 549         /* make sure unlock happens before kick */
 550         barrier();
 551
 552         if (unlikely(xl->spinners))
 553                 xen_spin_unlock_slow(xl);
 554 }
 555
 556 static __cpuinit void xen_init_lock_cpu(int cpu)
 557 {
 558         int irq;
 559         const char *name;
 560
 561         name = kasprintf(GFP_KERNEL, "spinlock%d", cpu);
 562         irq = bind_ipi_to_irqhandler(XEN_SPIN_UNLOCK_VECTOR,
 563                                      cpu,
 564                                      xen_reschedule_interrupt,
 565                                      IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
 566                                      name,
 567                                      NULL);
 568
 569         if (irq >= 0) {
 570                 disable_irq(irq); /* make sure it's never delivered */
 571                 per_cpu(lock_kicker_irq, cpu) = irq;
 572         }
 573
 574         printk("cpu %d spinlock event irq %d\n", cpu, irq);
 575 }
 576
 577 static void __init xen_init_spinlocks(void)
 578 {
 579         pv_lock_ops.spin_is_locked = xen_spin_is_locked;
 580         pv_lock_ops.spin_is_contended = xen_spin_is_contended;
 581         pv_lock_ops.spin_lock = xen_spin_lock;
 582         pv_lock_ops.spin_trylock = xen_spin_trylock;
 583         pv_lock_ops.spin_unlock = xen_spin_unlock;
 584 }
 585
 586 static const struct smp_ops xen_smp_ops __initdata = {
 587         .smp_prepare_boot_cpu = xen_smp_prepare_boot_cpu,
 588         .smp_prepare_cpus = xen_smp_prepare_cpus,
 589         .cpu_up = xen_cpu_up,
 590         .smp_cpus_done = xen_smp_cpus_done,
 591
 592         .smp_send_stop = xen_smp_send_stop,
 593         .smp_send_reschedule = xen_smp_send_reschedule,
 594
 595         .send_call_func_ipi = xen_smp_send_call_function_ipi,
 596         .send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
 597 };
 598
 599 void __init xen_smp_init(void)
 600 {
 601         smp_ops = xen_smp_ops;
 602         xen_fill_possible_map();
 603         xen_init_spinlocks();
 604 }