qemu-timer.c

   1 /*
   2  * QEMU System Emulator
   3  *
   4  * Copyright (c) 2003-2008 Fabrice Bellard
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a copy
   7  * of this software and associated documentation files (the "Software"), to deal
   8  * in the Software without restriction, including without limitation the rights
   9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10  * copies of the Software, and to permit persons to whom the Software is
  11  * furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included in
  14  * all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22  * THE SOFTWARE.
  23  */
  24
  25 #include "sysemu.h"
  26 #include "net.h"
  27 #include "monitor.h"
  28 #include "console.h"
  29
  30 #include "hw/hw.h"
  31
  32 #include "qemu-timer.h"
  33
  34 #ifdef _WIN32
  35 #include <mmsystem.h>
  36 #endif
  37
  38 /***********************************************************/
  39 /* timers */
  40
  41 #define QEMU_CLOCK_REALTIME 0
  42 #define QEMU_CLOCK_VIRTUAL  1
  43 #define QEMU_CLOCK_HOST     2
  44
  45 struct QEMUClock {
  46     QEMUTimer *active_timers;
  47
  48     NotifierList reset_notifiers;
  49     int64_t last;
  50
  51     int type;
  52     bool enabled;
  53 };
  54
  55 struct QEMUTimer {
  56     int64_t expire_time;        /* in nanoseconds */
  57     QEMUClock *clock;
  58     QEMUTimerCB *cb;
  59     void *opaque;
  60     QEMUTimer *next;
  61     int scale;
  62 };
  63
  64 struct qemu_alarm_timer {
  65     char const *name;
  66     int (*start)(struct qemu_alarm_timer *t);
  67     void (*stop)(struct qemu_alarm_timer *t);
  68     void (*rearm)(struct qemu_alarm_timer *t, int64_t nearest_delta_ns);
  69 #if defined(__linux__)
  70     timer_t timer;
  71     int fd;
  72 #elif defined(_WIN32)
  73     HANDLE timer;
  74 #endif
  75     bool expired;
  76     bool pending;
  77 };
  78
  79 static struct qemu_alarm_timer *alarm_timer;
  80
  81 static bool qemu_timer_expired_ns(QEMUTimer *timer_head, int64_t current_time)
  82 {
  83     return timer_head && (timer_head->expire_time <= current_time);
  84 }
  85
  86 static int64_t qemu_next_alarm_deadline(void)
  87 {
  88     int64_t delta = INT64_MAX;
  89     int64_t rtdelta;
  90
  91     if (!use_icount && vm_clock->enabled && vm_clock->active_timers) {
  92         delta = vm_clock->active_timers->expire_time -
  93                      qemu_get_clock_ns(vm_clock);
  94     }
  95     if (host_clock->enabled && host_clock->active_timers) {
  96         int64_t hdelta = host_clock->active_timers->expire_time -
  97                  qemu_get_clock_ns(host_clock);
  98         if (hdelta < delta) {
  99             delta = hdelta;
 100         }
 101     }
 102     if (rt_clock->enabled && rt_clock->active_timers) {
 103         rtdelta = (rt_clock->active_timers->expire_time -
 104                  qemu_get_clock_ns(rt_clock));
 105         if (rtdelta < delta) {
 106             delta = rtdelta;
 107         }
 108     }
 109
 110     return delta;
 111 }
 112
 113 static void qemu_rearm_alarm_timer(struct qemu_alarm_timer *t)
 114 {
 115     int64_t nearest_delta_ns = qemu_next_alarm_deadline();
 116     if (nearest_delta_ns < INT64_MAX) {
 117         t->rearm(t, nearest_delta_ns);
 118     }
 119 }
 120
 121 /* TODO: MIN_TIMER_REARM_NS should be optimized */
 122 #define MIN_TIMER_REARM_NS 250000
 123
 124 #ifdef _WIN32
 125
 126 static int mm_start_timer(struct qemu_alarm_timer *t);
 127 static void mm_stop_timer(struct qemu_alarm_timer *t);
 128 static void mm_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
 129
 130 static int win32_start_timer(struct qemu_alarm_timer *t);
 131 static void win32_stop_timer(struct qemu_alarm_timer *t);
 132 static void win32_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
 133
 134 #else
 135
 136 static int unix_start_timer(struct qemu_alarm_timer *t);
 137 static void unix_stop_timer(struct qemu_alarm_timer *t);
 138 static void unix_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
 139
 140 #ifdef __linux__
 141
 142 static int dynticks_start_timer(struct qemu_alarm_timer *t);
 143 static void dynticks_stop_timer(struct qemu_alarm_timer *t);
 144 static void dynticks_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
 145
 146 #endif /* __linux__ */
 147
 148 #endif /* _WIN32 */
 149
 150 static struct qemu_alarm_timer alarm_timers[] = {
 151 #ifndef _WIN32
 152 #ifdef __linux__
 153     {"dynticks", dynticks_start_timer,
 154      dynticks_stop_timer, dynticks_rearm_timer},
 155 #endif
 156     {"unix", unix_start_timer, unix_stop_timer, unix_rearm_timer},
 157 #else
 158     {"mmtimer", mm_start_timer, mm_stop_timer, mm_rearm_timer},
 159     {"dynticks", win32_start_timer, win32_stop_timer, win32_rearm_timer},
 160 #endif
 161     {NULL, }
 162 };
 163
 164 static void show_available_alarms(void)
 165 {
 166     int i;
 167
 168     printf("Available alarm timers, in order of precedence:\n");
 169     for (i = 0; alarm_timers[i].name; i++)
 170         printf("%s\n", alarm_timers[i].name);
 171 }
 172
 173 void configure_alarms(char const *opt)
 174 {
 175     int i;
 176     int cur = 0;
 177     int count = ARRAY_SIZE(alarm_timers) - 1;
 178     char *arg;
 179     char *name;
 180     struct qemu_alarm_timer tmp;
 181
 182     if (is_help_option(opt)) {
 183         show_available_alarms();
 184         exit(0);
 185     }
 186
 187     arg = g_strdup(opt);
 188
 189     /* Reorder the array */
 190     name = strtok(arg, ",");
 191     while (name) {
 192         for (i = 0; i < count && alarm_timers[i].name; i++) {
 193             if (!strcmp(alarm_timers[i].name, name))
 194                 break;
 195         }
 196
 197         if (i == count) {
 198             fprintf(stderr, "Unknown clock %s\n", name);
 199             goto next;
 200         }
 201
 202         if (i < cur)
 203             /* Ignore */
 204             goto next;
 205
 206         /* Swap */
 207         tmp = alarm_timers[i];
 208         alarm_timers[i] = alarm_timers[cur];
 209         alarm_timers[cur] = tmp;
 210
 211         cur++;
 212 next:
 213         name = strtok(NULL, ",");
 214     }
 215
 216     g_free(arg);
 217
 218     if (cur) {
 219         /* Disable remaining timers */
 220         for (i = cur; i < count; i++)
 221             alarm_timers[i].name = NULL;
 222     } else {
 223         show_available_alarms();
 224         exit(1);
 225     }
 226 }
 227
 228 QEMUClock *rt_clock;
 229 QEMUClock *vm_clock;
 230 QEMUClock *host_clock;
 231
 232 static QEMUClock *qemu_new_clock(int type)
 233 {
 234     QEMUClock *clock;
 235
 236     clock = g_malloc0(sizeof(QEMUClock));
 237     clock->type = type;
 238     clock->enabled = true;
 239     clock->last = INT64_MIN;
 240     notifier_list_init(&clock->reset_notifiers);
 241     return clock;
 242 }
 243
 244 void qemu_clock_enable(QEMUClock *clock, bool enabled)
 245 {
 246     bool old = clock->enabled;
 247     clock->enabled = enabled;
 248     if (enabled && !old) {
 249         qemu_rearm_alarm_timer(alarm_timer);
 250     }
 251 }
 252
 253 int64_t qemu_clock_has_timers(QEMUClock *clock)
 254 {
 255     return !!clock->active_timers;
 256 }
 257
 258 int64_t qemu_clock_expired(QEMUClock *clock)
 259 {
 260     return (clock->active_timers &&
 261             clock->active_timers->expire_time < qemu_get_clock_ns(clock));
 262 }
 263
 264 int64_t qemu_clock_deadline(QEMUClock *clock)
 265 {
 266     /* To avoid problems with overflow limit this to 2^32.  */
 267     int64_t delta = INT32_MAX;
 268
 269     if (clock->active_timers) {
 270         delta = clock->active_timers->expire_time - qemu_get_clock_ns(clock);
 271     }
 272     if (delta < 0) {
 273         delta = 0;
 274     }
 275     return delta;
 276 }
 277
 278 QEMUTimer *qemu_new_timer(QEMUClock *clock, int scale,
 279                           QEMUTimerCB *cb, void *opaque)
 280 {
 281     QEMUTimer *ts;
 282
 283     ts = g_malloc0(sizeof(QEMUTimer));
 284     ts->clock = clock;
 285     ts->cb = cb;
 286     ts->opaque = opaque;
 287     ts->scale = scale;
 288     return ts;
 289 }
 290
 291 void qemu_free_timer(QEMUTimer *ts)
 292 {
 293     g_free(ts);
 294 }
 295
 296 /* stop a timer, but do not dealloc it */
 297 void qemu_del_timer(QEMUTimer *ts)
 298 {
 299     QEMUTimer **pt, *t;
 300
 301     /* NOTE: this code must be signal safe because
 302        qemu_timer_expired() can be called from a signal. */
 303     pt = &ts->clock->active_timers;
 304     for(;;) {
 305         t = *pt;
 306         if (!t)
 307             break;
 308         if (t == ts) {
 309             *pt = t->next;
 310             break;
 311         }
 312         pt = &t->next;
 313     }
 314 }
 315
 316 /* modify the current timer so that it will be fired when current_time
 317    >= expire_time. The corresponding callback will be called. */
 318 void qemu_mod_timer_ns(QEMUTimer *ts, int64_t expire_time)
 319 {
 320     QEMUTimer **pt, *t;
 321
 322     qemu_del_timer(ts);
 323
 324     /* add the timer in the sorted list */
 325     /* NOTE: this code must be signal safe because
 326        qemu_timer_expired() can be called from a signal. */
 327     pt = &ts->clock->active_timers;
 328     for(;;) {
 329         t = *pt;
 330         if (!qemu_timer_expired_ns(t, expire_time)) {
 331             break;
 332         }
 333         pt = &t->next;
 334     }
 335     ts->expire_time = expire_time;
 336     ts->next = *pt;
 337     *pt = ts;
 338
 339     /* Rearm if necessary  */
 340     if (pt == &ts->clock->active_timers) {
 341         if (!alarm_timer->pending) {
 342             qemu_rearm_alarm_timer(alarm_timer);
 343         }
 344         /* Interrupt execution to force deadline recalculation.  */
 345         qemu_clock_warp(ts->clock);
 346         if (use_icount) {
 347             qemu_notify_event();
 348         }
 349     }
 350 }
 351
 352 void qemu_mod_timer(QEMUTimer *ts, int64_t expire_time)
 353 {
 354     qemu_mod_timer_ns(ts, expire_time * ts->scale);
 355 }
 356
 357 bool qemu_timer_pending(QEMUTimer *ts)
 358 {
 359     QEMUTimer *t;
 360     for (t = ts->clock->active_timers; t != NULL; t = t->next) {
 361         if (t == ts) {
 362             return true;
 363         }
 364     }
 365     return false;
 366 }
 367
 368 bool qemu_timer_expired(QEMUTimer *timer_head, int64_t current_time)
 369 {
 370     return qemu_timer_expired_ns(timer_head, current_time * timer_head->scale);
 371 }
 372
 373 void qemu_run_timers(QEMUClock *clock)
 374 {
 375     QEMUTimer *ts;
 376     int64_t current_time;
 377
 378     if (!clock->enabled)
 379         return;
 380
 381     current_time = qemu_get_clock_ns(clock);
 382     for(;;) {
 383         ts = clock->active_timers;
 384         if (!qemu_timer_expired_ns(ts, current_time)) {
 385             break;
 386         }
 387         /* remove timer from the list before calling the callback */
 388         clock->active_timers = ts->next;
 389         ts->next = NULL;
 390
 391         /* run the callback (the timer list can be modified) */
 392         ts->cb(ts->opaque);
 393     }
 394 }
 395
 396 int64_t qemu_get_clock_ns(QEMUClock *clock)
 397 {
 398     int64_t now, last;
 399
 400     switch(clock->type) {
 401     case QEMU_CLOCK_REALTIME:
 402         return get_clock();
 403     default:
 404     case QEMU_CLOCK_VIRTUAL:
 405         if (use_icount) {
 406             return cpu_get_icount();
 407         } else {
 408             return cpu_get_clock();
 409         }
 410     case QEMU_CLOCK_HOST:
 411         now = get_clock_realtime();
 412         last = clock->last;
 413         clock->last = now;
 414         if (now < last) {
 415             notifier_list_notify(&clock->reset_notifiers, &now);
 416         }
 417         return now;
 418     }
 419 }
 420
 421 void qemu_register_clock_reset_notifier(QEMUClock *clock, Notifier *notifier)
 422 {
 423     notifier_list_add(&clock->reset_notifiers, notifier);
 424 }
 425
 426 void qemu_unregister_clock_reset_notifier(QEMUClock *clock, Notifier *notifier)
 427 {
 428     notifier_remove(notifier);
 429 }
 430
 431 void init_clocks(void)
 432 {
 433     if (!rt_clock) {
 434         rt_clock = qemu_new_clock(QEMU_CLOCK_REALTIME);
 435         vm_clock = qemu_new_clock(QEMU_CLOCK_VIRTUAL);
 436         host_clock = qemu_new_clock(QEMU_CLOCK_HOST);
 437     }
 438 }
 439
 440 uint64_t qemu_timer_expire_time_ns(QEMUTimer *ts)
 441 {
 442     return qemu_timer_pending(ts) ? ts->expire_time : -1;
 443 }
 444
 445 void qemu_run_all_timers(void)
 446 {
 447     alarm_timer->pending = false;
 448
 449     /* vm time timers */
 450     qemu_run_timers(vm_clock);
 451     qemu_run_timers(rt_clock);
 452     qemu_run_timers(host_clock);
 453
 454     /* rearm timer, if not periodic */
 455     if (alarm_timer->expired) {
 456         alarm_timer->expired = false;
 457         qemu_rearm_alarm_timer(alarm_timer);
 458     }
 459 }
 460
 461 #ifdef _WIN32
 462 static void CALLBACK host_alarm_handler(PVOID lpParam, BOOLEAN unused)
 463 #else
 464 static void host_alarm_handler(int host_signum)
 465 #endif
 466 {
 467     struct qemu_alarm_timer *t = alarm_timer;
 468     if (!t)
 469         return;
 470
 471     t->expired = true;
 472     t->pending = true;
 473     qemu_notify_event();
 474 }
 475
 476 #if defined(__linux__)
 477
 478 #include "compatfd.h"
 479
 480 static int dynticks_start_timer(struct qemu_alarm_timer *t)
 481 {
 482     struct sigevent ev;
 483     timer_t host_timer;
 484     struct sigaction act;
 485
 486     sigfillset(&act.sa_mask);
 487     act.sa_flags = 0;
 488     act.sa_handler = host_alarm_handler;
 489
 490     sigaction(SIGALRM, &act, NULL);
 491
 492     /*
 493      * Initialize ev struct to 0 to avoid valgrind complaining
 494      * about uninitialized data in timer_create call
 495      */
 496     memset(&ev, 0, sizeof(ev));
 497     ev.sigev_value.sival_int = 0;
 498     ev.sigev_notify = SIGEV_SIGNAL;
 499 #ifdef SIGEV_THREAD_ID
 500     if (qemu_signalfd_available()) {
 501         ev.sigev_notify = SIGEV_THREAD_ID;
 502         ev._sigev_un._tid = qemu_get_thread_id();
 503     }
 504 #endif /* SIGEV_THREAD_ID */
 505     ev.sigev_signo = SIGALRM;
 506
 507     if (timer_create(CLOCK_REALTIME, &ev, &host_timer)) {
 508         perror("timer_create");
 509         return -1;
 510     }
 511
 512     t->timer = host_timer;
 513
 514     return 0;
 515 }
 516
 517 static void dynticks_stop_timer(struct qemu_alarm_timer *t)
 518 {
 519     timer_t host_timer = t->timer;
 520
 521     timer_delete(host_timer);
 522 }
 523
 524 static void dynticks_rearm_timer(struct qemu_alarm_timer *t,
 525                                  int64_t nearest_delta_ns)
 526 {
 527     timer_t host_timer = t->timer;
 528     struct itimerspec timeout;
 529     int64_t current_ns;
 530
 531     if (nearest_delta_ns < MIN_TIMER_REARM_NS)
 532         nearest_delta_ns = MIN_TIMER_REARM_NS;
 533
 534     /* check whether a timer is already running */
 535     if (timer_gettime(host_timer, &timeout)) {
 536         perror("gettime");
 537         fprintf(stderr, "Internal timer error: aborting\n");
 538         exit(1);
 539     }
 540     current_ns = timeout.it_value.tv_sec * 1000000000LL + timeout.it_value.tv_nsec;
 541     if (current_ns && current_ns <= nearest_delta_ns)
 542         return;
 543
 544     timeout.it_interval.tv_sec = 0;
 545     timeout.it_interval.tv_nsec = 0; /* 0 for one-shot timer */
 546     timeout.it_value.tv_sec =  nearest_delta_ns / 1000000000;
 547     timeout.it_value.tv_nsec = nearest_delta_ns % 1000000000;
 548     if (timer_settime(host_timer, 0 /* RELATIVE */, &timeout, NULL)) {
 549         perror("settime");
 550         fprintf(stderr, "Internal timer error: aborting\n");
 551         exit(1);
 552     }
 553 }
 554
 555 #endif /* defined(__linux__) */
 556
 557 #if !defined(_WIN32)
 558
 559 static int unix_start_timer(struct qemu_alarm_timer *t)
 560 {
 561     struct sigaction act;
 562
 563     /* timer signal */
 564     sigfillset(&act.sa_mask);
 565     act.sa_flags = 0;
 566     act.sa_handler = host_alarm_handler;
 567
 568     sigaction(SIGALRM, &act, NULL);
 569     return 0;
 570 }
 571
 572 static void unix_rearm_timer(struct qemu_alarm_timer *t,
 573                              int64_t nearest_delta_ns)
 574 {
 575     struct itimerval itv;
 576     int err;
 577
 578     if (nearest_delta_ns < MIN_TIMER_REARM_NS)
 579         nearest_delta_ns = MIN_TIMER_REARM_NS;
 580
 581     itv.it_interval.tv_sec = 0;
 582     itv.it_interval.tv_usec = 0; /* 0 for one-shot timer */
 583     itv.it_value.tv_sec =  nearest_delta_ns / 1000000000;
 584     itv.it_value.tv_usec = (nearest_delta_ns % 1000000000) / 1000;
 585     err = setitimer(ITIMER_REAL, &itv, NULL);
 586     if (err) {
 587         perror("setitimer");
 588         fprintf(stderr, "Internal timer error: aborting\n");
 589         exit(1);
 590     }
 591 }
 592
 593 static void unix_stop_timer(struct qemu_alarm_timer *t)
 594 {
 595     struct itimerval itv;
 596
 597     memset(&itv, 0, sizeof(itv));
 598     setitimer(ITIMER_REAL, &itv, NULL);
 599 }
 600
 601 #endif /* !defined(_WIN32) */
 602
 603
 604 #ifdef _WIN32
 605
 606 static MMRESULT mm_timer;
 607 static TIMECAPS mm_tc;
 608
 609 static void CALLBACK mm_alarm_handler(UINT uTimerID, UINT uMsg,
 610                                       DWORD_PTR dwUser, DWORD_PTR dw1,
 611                                       DWORD_PTR dw2)
 612 {
 613     struct qemu_alarm_timer *t = alarm_timer;
 614     if (!t) {
 615         return;
 616     }
 617     t->expired = true;
 618     t->pending = true;
 619     qemu_notify_event();
 620 }
 621
 622 static int mm_start_timer(struct qemu_alarm_timer *t)
 623 {
 624     timeGetDevCaps(&mm_tc, sizeof(mm_tc));
 625
 626     timeBeginPeriod(mm_tc.wPeriodMin);
 627
 628     mm_timer = timeSetEvent(mm_tc.wPeriodMin,   /* interval (ms) */
 629                             mm_tc.wPeriodMin,   /* resolution */
 630                             mm_alarm_handler,   /* function */
 631                             (DWORD_PTR)t,       /* parameter */
 632                             TIME_ONESHOT | TIME_CALLBACK_FUNCTION);
 633
 634     if (!mm_timer) {
 635         fprintf(stderr, "Failed to initialize win32 alarm timer\n");
 636         timeEndPeriod(mm_tc.wPeriodMin);
 637         return -1;
 638     }
 639
 640     return 0;
 641 }
 642
 643 static void mm_stop_timer(struct qemu_alarm_timer *t)
 644 {
 645     timeKillEvent(mm_timer);
 646     timeEndPeriod(mm_tc.wPeriodMin);
 647 }
 648
 649 static void mm_rearm_timer(struct qemu_alarm_timer *t, int64_t delta)
 650 {
 651     int64_t nearest_delta_ms = delta / 1000000;
 652     if (nearest_delta_ms < mm_tc.wPeriodMin) {
 653         nearest_delta_ms = mm_tc.wPeriodMin;
 654     } else if (nearest_delta_ms > mm_tc.wPeriodMax) {
 655         nearest_delta_ms = mm_tc.wPeriodMax;
 656     }
 657
 658     timeKillEvent(mm_timer);
 659     mm_timer = timeSetEvent((UINT)nearest_delta_ms,
 660                             mm_tc.wPeriodMin,
 661                             mm_alarm_handler,
 662                             (DWORD_PTR)t,
 663                             TIME_ONESHOT | TIME_CALLBACK_FUNCTION);
 664
 665     if (!mm_timer) {
 666         fprintf(stderr, "Failed to re-arm win32 alarm timer\n");
 667         timeEndPeriod(mm_tc.wPeriodMin);
 668         exit(1);
 669     }
 670 }
 671
 672 static int win32_start_timer(struct qemu_alarm_timer *t)
 673 {
 674     HANDLE hTimer;
 675     BOOLEAN success;
 676
 677     /* If you call ChangeTimerQueueTimer on a one-shot timer (its period
 678        is zero) that has already expired, the timer is not updated.  Since
 679        creating a new timer is relatively expensive, set a bogus one-hour
 680        interval in the dynticks case.  */
 681     success = CreateTimerQueueTimer(&hTimer,
 682                           NULL,
 683                           host_alarm_handler,
 684                           t,
 685                           1,
 686                           3600000,
 687                           WT_EXECUTEINTIMERTHREAD);
 688
 689     if (!success) {
 690         fprintf(stderr, "Failed to initialize win32 alarm timer: %ld\n",
 691                 GetLastError());
 692         return -1;
 693     }
 694
 695     t->timer = hTimer;
 696     return 0;
 697 }
 698
 699 static void win32_stop_timer(struct qemu_alarm_timer *t)
 700 {
 701     HANDLE hTimer = t->timer;
 702
 703     if (hTimer) {
 704         DeleteTimerQueueTimer(NULL, hTimer, NULL);
 705     }
 706 }
 707
 708 static void win32_rearm_timer(struct qemu_alarm_timer *t,
 709                               int64_t nearest_delta_ns)
 710 {
 711     HANDLE hTimer = t->timer;
 712     int64_t nearest_delta_ms;
 713     BOOLEAN success;
 714
 715     nearest_delta_ms = nearest_delta_ns / 1000000;
 716     if (nearest_delta_ms < 1) {
 717         nearest_delta_ms = 1;
 718     }
 719     /* ULONG_MAX can be 32 bit */
 720     if (nearest_delta_ms > ULONG_MAX) {
 721         nearest_delta_ms = ULONG_MAX;
 722     }
 723     success = ChangeTimerQueueTimer(NULL,
 724                                     hTimer,
 725                                     (unsigned long) nearest_delta_ms,
 726                                     3600000);
 727
 728     if (!success) {
 729         fprintf(stderr, "Failed to rearm win32 alarm timer: %ld\n",
 730                 GetLastError());
 731         exit(-1);
 732     }
 733
 734 }
 735
 736 #endif /* _WIN32 */
 737
 738 static void quit_timers(void)
 739 {
 740     struct qemu_alarm_timer *t = alarm_timer;
 741     alarm_timer = NULL;
 742     t->stop(t);
 743 }
 744
 745 int init_timer_alarm(void)
 746 {
 747     struct qemu_alarm_timer *t = NULL;
 748     int i, err = -1;
 749
 750     if (alarm_timer) {
 751         return 0;
 752     }
 753
 754     for (i = 0; alarm_timers[i].name; i++) {
 755         t = &alarm_timers[i];
 756
 757         err = t->start(t);
 758         if (!err)
 759             break;
 760     }
 761
 762     if (err) {
 763         err = -ENOENT;
 764         goto fail;
 765     }
 766
 767     atexit(quit_timers);
 768     alarm_timer = t;
 769     return 0;
 770
 771 fail:
 772     return err;
 773 }
 774