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;
 116     if (!rt_clock->active_timers &&
 117         !vm_clock->active_timers &&
 118         !host_clock->active_timers) {
 119         return;
 120     }
 121     nearest_delta_ns = qemu_next_alarm_deadline();
 122     t->rearm(t, nearest_delta_ns);
 123 }
 124
 125 /* TODO: MIN_TIMER_REARM_NS should be optimized */
 126 #define MIN_TIMER_REARM_NS 250000
 127
 128 #ifdef _WIN32
 129
 130 static int mm_start_timer(struct qemu_alarm_timer *t);
 131 static void mm_stop_timer(struct qemu_alarm_timer *t);
 132 static void mm_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
 133
 134 static int win32_start_timer(struct qemu_alarm_timer *t);
 135 static void win32_stop_timer(struct qemu_alarm_timer *t);
 136 static void win32_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
 137
 138 #else
 139
 140 static int unix_start_timer(struct qemu_alarm_timer *t);
 141 static void unix_stop_timer(struct qemu_alarm_timer *t);
 142 static void unix_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
 143
 144 #ifdef __linux__
 145
 146 static int dynticks_start_timer(struct qemu_alarm_timer *t);
 147 static void dynticks_stop_timer(struct qemu_alarm_timer *t);
 148 static void dynticks_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
 149
 150 #endif /* __linux__ */
 151
 152 #endif /* _WIN32 */
 153
 154 static struct qemu_alarm_timer alarm_timers[] = {
 155 #ifndef _WIN32
 156 #ifdef __linux__
 157     {"dynticks", dynticks_start_timer,
 158      dynticks_stop_timer, dynticks_rearm_timer},
 159 #endif
 160     {"unix", unix_start_timer, unix_stop_timer, unix_rearm_timer},
 161 #else
 162     {"mmtimer", mm_start_timer, mm_stop_timer, mm_rearm_timer},
 163     {"dynticks", win32_start_timer, win32_stop_timer, win32_rearm_timer},
 164 #endif
 165     {NULL, }
 166 };
 167
 168 static void show_available_alarms(void)
 169 {
 170     int i;
 171
 172     printf("Available alarm timers, in order of precedence:\n");
 173     for (i = 0; alarm_timers[i].name; i++)
 174         printf("%s\n", alarm_timers[i].name);
 175 }
 176
 177 void configure_alarms(char const *opt)
 178 {
 179     int i;
 180     int cur = 0;
 181     int count = ARRAY_SIZE(alarm_timers) - 1;
 182     char *arg;
 183     char *name;
 184     struct qemu_alarm_timer tmp;
 185
 186     if (is_help_option(opt)) {
 187         show_available_alarms();
 188         exit(0);
 189     }
 190
 191     arg = g_strdup(opt);
 192
 193     /* Reorder the array */
 194     name = strtok(arg, ",");
 195     while (name) {
 196         for (i = 0; i < count && alarm_timers[i].name; i++) {
 197             if (!strcmp(alarm_timers[i].name, name))
 198                 break;
 199         }
 200
 201         if (i == count) {
 202             fprintf(stderr, "Unknown clock %s\n", name);
 203             goto next;
 204         }
 205
 206         if (i < cur)
 207             /* Ignore */
 208             goto next;
 209
 210         /* Swap */
 211         tmp = alarm_timers[i];
 212         alarm_timers[i] = alarm_timers[cur];
 213         alarm_timers[cur] = tmp;
 214
 215         cur++;
 216 next:
 217         name = strtok(NULL, ",");
 218     }
 219
 220     g_free(arg);
 221
 222     if (cur) {
 223         /* Disable remaining timers */
 224         for (i = cur; i < count; i++)
 225             alarm_timers[i].name = NULL;
 226     } else {
 227         show_available_alarms();
 228         exit(1);
 229     }
 230 }
 231
 232 QEMUClock *rt_clock;
 233 QEMUClock *vm_clock;
 234 QEMUClock *host_clock;
 235
 236 static QEMUClock *qemu_new_clock(int type)
 237 {
 238     QEMUClock *clock;
 239
 240     clock = g_malloc0(sizeof(QEMUClock));
 241     clock->type = type;
 242     clock->enabled = true;
 243     clock->last = INT64_MIN;
 244     notifier_list_init(&clock->reset_notifiers);
 245     return clock;
 246 }
 247
 248 void qemu_clock_enable(QEMUClock *clock, bool enabled)
 249 {
 250     bool old = clock->enabled;
 251     clock->enabled = enabled;
 252     if (enabled && !old) {
 253         qemu_rearm_alarm_timer(alarm_timer);
 254     }
 255 }
 256
 257 int64_t qemu_clock_has_timers(QEMUClock *clock)
 258 {
 259     return !!clock->active_timers;
 260 }
 261
 262 int64_t qemu_clock_expired(QEMUClock *clock)
 263 {
 264     return (clock->active_timers &&
 265             clock->active_timers->expire_time < qemu_get_clock_ns(clock));
 266 }
 267
 268 int64_t qemu_clock_deadline(QEMUClock *clock)
 269 {
 270     /* To avoid problems with overflow limit this to 2^32.  */
 271     int64_t delta = INT32_MAX;
 272
 273     if (clock->active_timers) {
 274         delta = clock->active_timers->expire_time - qemu_get_clock_ns(clock);
 275     }
 276     if (delta < 0) {
 277         delta = 0;
 278     }
 279     return delta;
 280 }
 281
 282 QEMUTimer *qemu_new_timer(QEMUClock *clock, int scale,
 283                           QEMUTimerCB *cb, void *opaque)
 284 {
 285     QEMUTimer *ts;
 286
 287     ts = g_malloc0(sizeof(QEMUTimer));
 288     ts->clock = clock;
 289     ts->cb = cb;
 290     ts->opaque = opaque;
 291     ts->scale = scale;
 292     return ts;
 293 }
 294
 295 void qemu_free_timer(QEMUTimer *ts)
 296 {
 297     g_free(ts);
 298 }
 299
 300 /* stop a timer, but do not dealloc it */
 301 void qemu_del_timer(QEMUTimer *ts)
 302 {
 303     QEMUTimer **pt, *t;
 304
 305     /* NOTE: this code must be signal safe because
 306        qemu_timer_expired() can be called from a signal. */
 307     pt = &ts->clock->active_timers;
 308     for(;;) {
 309         t = *pt;
 310         if (!t)
 311             break;
 312         if (t == ts) {
 313             *pt = t->next;
 314             break;
 315         }
 316         pt = &t->next;
 317     }
 318 }
 319
 320 /* modify the current timer so that it will be fired when current_time
 321    >= expire_time. The corresponding callback will be called. */
 322 void qemu_mod_timer_ns(QEMUTimer *ts, int64_t expire_time)
 323 {
 324     QEMUTimer **pt, *t;
 325
 326     qemu_del_timer(ts);
 327
 328     /* add the timer in the sorted list */
 329     /* NOTE: this code must be signal safe because
 330        qemu_timer_expired() can be called from a signal. */
 331     pt = &ts->clock->active_timers;
 332     for(;;) {
 333         t = *pt;
 334         if (!qemu_timer_expired_ns(t, expire_time)) {
 335             break;
 336         }
 337         pt = &t->next;
 338     }
 339     ts->expire_time = expire_time;
 340     ts->next = *pt;
 341     *pt = ts;
 342
 343     /* Rearm if necessary  */
 344     if (pt == &ts->clock->active_timers) {
 345         if (!alarm_timer->pending) {
 346             qemu_rearm_alarm_timer(alarm_timer);
 347         }
 348         /* Interrupt execution to force deadline recalculation.  */
 349         qemu_clock_warp(ts->clock);
 350         if (use_icount) {
 351             qemu_notify_event();
 352         }
 353     }
 354 }
 355
 356 void qemu_mod_timer(QEMUTimer *ts, int64_t expire_time)
 357 {
 358     qemu_mod_timer_ns(ts, expire_time * ts->scale);
 359 }
 360
 361 bool qemu_timer_pending(QEMUTimer *ts)
 362 {
 363     QEMUTimer *t;
 364     for (t = ts->clock->active_timers; t != NULL; t = t->next) {
 365         if (t == ts) {
 366             return true;
 367         }
 368     }
 369     return false;
 370 }
 371
 372 bool qemu_timer_expired(QEMUTimer *timer_head, int64_t current_time)
 373 {
 374     return qemu_timer_expired_ns(timer_head, current_time * timer_head->scale);
 375 }
 376
 377 void qemu_run_timers(QEMUClock *clock)
 378 {
 379     QEMUTimer **ptimer_head, *ts;
 380     int64_t current_time;
 381
 382     if (!clock->enabled)
 383         return;
 384
 385     current_time = qemu_get_clock_ns(clock);
 386     ptimer_head = &clock->active_timers;
 387     for(;;) {
 388         ts = *ptimer_head;
 389         if (!qemu_timer_expired_ns(ts, current_time)) {
 390             break;
 391         }
 392         /* remove timer from the list before calling the callback */
 393         *ptimer_head = ts->next;
 394         ts->next = NULL;
 395
 396         /* run the callback (the timer list can be modified) */
 397         ts->cb(ts->opaque);
 398     }
 399 }
 400
 401 int64_t qemu_get_clock_ns(QEMUClock *clock)
 402 {
 403     int64_t now, last;
 404
 405     switch(clock->type) {
 406     case QEMU_CLOCK_REALTIME:
 407         return get_clock();
 408     default:
 409     case QEMU_CLOCK_VIRTUAL:
 410         if (use_icount) {
 411             return cpu_get_icount();
 412         } else {
 413             return cpu_get_clock();
 414         }
 415     case QEMU_CLOCK_HOST:
 416         now = get_clock_realtime();
 417         last = clock->last;
 418         clock->last = now;
 419         if (now < last) {
 420             notifier_list_notify(&clock->reset_notifiers, &now);
 421         }
 422         return now;
 423     }
 424 }
 425
 426 void qemu_register_clock_reset_notifier(QEMUClock *clock, Notifier *notifier)
 427 {
 428     notifier_list_add(&clock->reset_notifiers, notifier);
 429 }
 430
 431 void qemu_unregister_clock_reset_notifier(QEMUClock *clock, Notifier *notifier)
 432 {
 433     notifier_remove(notifier);
 434 }
 435
 436 void init_clocks(void)
 437 {
 438     rt_clock = qemu_new_clock(QEMU_CLOCK_REALTIME);
 439     vm_clock = qemu_new_clock(QEMU_CLOCK_VIRTUAL);
 440     host_clock = qemu_new_clock(QEMU_CLOCK_HOST);
 441 }
 442
 443 uint64_t qemu_timer_expire_time_ns(QEMUTimer *ts)
 444 {
 445     return qemu_timer_pending(ts) ? ts->expire_time : -1;
 446 }
 447
 448 void qemu_run_all_timers(void)
 449 {
 450     alarm_timer->pending = false;
 451
 452     /* vm time timers */
 453     qemu_run_timers(vm_clock);
 454     qemu_run_timers(rt_clock);
 455     qemu_run_timers(host_clock);
 456
 457     /* rearm timer, if not periodic */
 458     if (alarm_timer->expired) {
 459         alarm_timer->expired = false;
 460         qemu_rearm_alarm_timer(alarm_timer);
 461     }
 462 }
 463
 464 #ifdef _WIN32
 465 static void CALLBACK host_alarm_handler(PVOID lpParam, BOOLEAN unused)
 466 #else
 467 static void host_alarm_handler(int host_signum)
 468 #endif
 469 {
 470     struct qemu_alarm_timer *t = alarm_timer;
 471     if (!t)
 472         return;
 473
 474     t->expired = true;
 475     t->pending = true;
 476     qemu_notify_event();
 477 }
 478
 479 #if defined(__linux__)
 480
 481 #include "compatfd.h"
 482
 483 static int dynticks_start_timer(struct qemu_alarm_timer *t)
 484 {
 485     struct sigevent ev;
 486     timer_t host_timer;
 487     struct sigaction act;
 488
 489     sigfillset(&act.sa_mask);
 490     act.sa_flags = 0;
 491     act.sa_handler = host_alarm_handler;
 492
 493     sigaction(SIGALRM, &act, NULL);
 494
 495     /*
 496      * Initialize ev struct to 0 to avoid valgrind complaining
 497      * about uninitialized data in timer_create call
 498      */
 499     memset(&ev, 0, sizeof(ev));
 500     ev.sigev_value.sival_int = 0;
 501     ev.sigev_notify = SIGEV_SIGNAL;
 502 #ifdef SIGEV_THREAD_ID
 503     if (qemu_signalfd_available()) {
 504         ev.sigev_notify = SIGEV_THREAD_ID;
 505         ev._sigev_un._tid = qemu_get_thread_id();
 506     }
 507 #endif /* SIGEV_THREAD_ID */
 508     ev.sigev_signo = SIGALRM;
 509
 510     if (timer_create(CLOCK_REALTIME, &ev, &host_timer)) {
 511         perror("timer_create");
 512         return -1;
 513     }
 514
 515     t->timer = host_timer;
 516
 517     return 0;
 518 }
 519
 520 static void dynticks_stop_timer(struct qemu_alarm_timer *t)
 521 {
 522     timer_t host_timer = t->timer;
 523
 524     timer_delete(host_timer);
 525 }
 526
 527 static void dynticks_rearm_timer(struct qemu_alarm_timer *t,
 528                                  int64_t nearest_delta_ns)
 529 {
 530     timer_t host_timer = t->timer;
 531     struct itimerspec timeout;
 532     int64_t current_ns;
 533
 534     if (nearest_delta_ns < MIN_TIMER_REARM_NS)
 535         nearest_delta_ns = MIN_TIMER_REARM_NS;
 536
 537     /* check whether a timer is already running */
 538     if (timer_gettime(host_timer, &timeout)) {
 539         perror("gettime");
 540         fprintf(stderr, "Internal timer error: aborting\n");
 541         exit(1);
 542     }
 543     current_ns = timeout.it_value.tv_sec * 1000000000LL + timeout.it_value.tv_nsec;
 544     if (current_ns && current_ns <= nearest_delta_ns)
 545         return;
 546
 547     timeout.it_interval.tv_sec = 0;
 548     timeout.it_interval.tv_nsec = 0; /* 0 for one-shot timer */
 549     timeout.it_value.tv_sec =  nearest_delta_ns / 1000000000;
 550     timeout.it_value.tv_nsec = nearest_delta_ns % 1000000000;
 551     if (timer_settime(host_timer, 0 /* RELATIVE */, &timeout, NULL)) {
 552         perror("settime");
 553         fprintf(stderr, "Internal timer error: aborting\n");
 554         exit(1);
 555     }
 556 }
 557
 558 #endif /* defined(__linux__) */
 559
 560 #if !defined(_WIN32)
 561
 562 static int unix_start_timer(struct qemu_alarm_timer *t)
 563 {
 564     struct sigaction act;
 565
 566     /* timer signal */
 567     sigfillset(&act.sa_mask);
 568     act.sa_flags = 0;
 569     act.sa_handler = host_alarm_handler;
 570
 571     sigaction(SIGALRM, &act, NULL);
 572     return 0;
 573 }
 574
 575 static void unix_rearm_timer(struct qemu_alarm_timer *t,
 576                              int64_t nearest_delta_ns)
 577 {
 578     struct itimerval itv;
 579     int err;
 580
 581     if (nearest_delta_ns < MIN_TIMER_REARM_NS)
 582         nearest_delta_ns = MIN_TIMER_REARM_NS;
 583
 584     itv.it_interval.tv_sec = 0;
 585     itv.it_interval.tv_usec = 0; /* 0 for one-shot timer */
 586     itv.it_value.tv_sec =  nearest_delta_ns / 1000000000;
 587     itv.it_value.tv_usec = (nearest_delta_ns % 1000000000) / 1000;
 588     err = setitimer(ITIMER_REAL, &itv, NULL);
 589     if (err) {
 590         perror("setitimer");
 591         fprintf(stderr, "Internal timer error: aborting\n");
 592         exit(1);
 593     }
 594 }
 595
 596 static void unix_stop_timer(struct qemu_alarm_timer *t)
 597 {
 598     struct itimerval itv;
 599
 600     memset(&itv, 0, sizeof(itv));
 601     setitimer(ITIMER_REAL, &itv, NULL);
 602 }
 603
 604 #endif /* !defined(_WIN32) */
 605
 606
 607 #ifdef _WIN32
 608
 609 static MMRESULT mm_timer;
 610 static TIMECAPS mm_tc;
 611
 612 static void CALLBACK mm_alarm_handler(UINT uTimerID, UINT uMsg,
 613                                       DWORD_PTR dwUser, DWORD_PTR dw1,
 614                                       DWORD_PTR dw2)
 615 {
 616     struct qemu_alarm_timer *t = alarm_timer;
 617     if (!t) {
 618         return;
 619     }
 620     t->expired = true;
 621     t->pending = true;
 622     qemu_notify_event();
 623 }
 624
 625 static int mm_start_timer(struct qemu_alarm_timer *t)
 626 {
 627     timeGetDevCaps(&mm_tc, sizeof(mm_tc));
 628
 629     timeBeginPeriod(mm_tc.wPeriodMin);
 630
 631     mm_timer = timeSetEvent(mm_tc.wPeriodMin,   /* interval (ms) */
 632                             mm_tc.wPeriodMin,   /* resolution */
 633                             mm_alarm_handler,   /* function */
 634                             (DWORD_PTR)t,       /* parameter */
 635                             TIME_ONESHOT | TIME_CALLBACK_FUNCTION);
 636
 637     if (!mm_timer) {
 638         fprintf(stderr, "Failed to initialize win32 alarm timer\n");
 639         timeEndPeriod(mm_tc.wPeriodMin);
 640         return -1;
 641     }
 642
 643     return 0;
 644 }
 645
 646 static void mm_stop_timer(struct qemu_alarm_timer *t)
 647 {
 648     timeKillEvent(mm_timer);
 649     timeEndPeriod(mm_tc.wPeriodMin);
 650 }
 651
 652 static void mm_rearm_timer(struct qemu_alarm_timer *t, int64_t delta)
 653 {
 654     int64_t nearest_delta_ms = delta / 1000000;
 655     if (nearest_delta_ms < mm_tc.wPeriodMin) {
 656         nearest_delta_ms = mm_tc.wPeriodMin;
 657     } else if (nearest_delta_ms > mm_tc.wPeriodMax) {
 658         nearest_delta_ms = mm_tc.wPeriodMax;
 659     }
 660
 661     timeKillEvent(mm_timer);
 662     mm_timer = timeSetEvent((UINT)nearest_delta_ms,
 663                             mm_tc.wPeriodMin,
 664                             mm_alarm_handler,
 665                             (DWORD_PTR)t,
 666                             TIME_ONESHOT | TIME_CALLBACK_FUNCTION);
 667
 668     if (!mm_timer) {
 669         fprintf(stderr, "Failed to re-arm win32 alarm timer\n");
 670         timeEndPeriod(mm_tc.wPeriodMin);
 671         exit(1);
 672     }
 673 }
 674
 675 static int win32_start_timer(struct qemu_alarm_timer *t)
 676 {
 677     HANDLE hTimer;
 678     BOOLEAN success;
 679
 680     /* If you call ChangeTimerQueueTimer on a one-shot timer (its period
 681        is zero) that has already expired, the timer is not updated.  Since
 682        creating a new timer is relatively expensive, set a bogus one-hour
 683        interval in the dynticks case.  */
 684     success = CreateTimerQueueTimer(&hTimer,
 685                           NULL,
 686                           host_alarm_handler,
 687                           t,
 688                           1,
 689                           3600000,
 690                           WT_EXECUTEINTIMERTHREAD);
 691
 692     if (!success) {
 693         fprintf(stderr, "Failed to initialize win32 alarm timer: %ld\n",
 694                 GetLastError());
 695         return -1;
 696     }
 697
 698     t->timer = hTimer;
 699     return 0;
 700 }
 701
 702 static void win32_stop_timer(struct qemu_alarm_timer *t)
 703 {
 704     HANDLE hTimer = t->timer;
 705
 706     if (hTimer) {
 707         DeleteTimerQueueTimer(NULL, hTimer, NULL);
 708     }
 709 }
 710
 711 static void win32_rearm_timer(struct qemu_alarm_timer *t,
 712                               int64_t nearest_delta_ns)
 713 {
 714     HANDLE hTimer = t->timer;
 715     int64_t nearest_delta_ms;
 716     BOOLEAN success;
 717
 718     nearest_delta_ms = nearest_delta_ns / 1000000;
 719     if (nearest_delta_ms < 1) {
 720         nearest_delta_ms = 1;
 721     }
 722     /* ULONG_MAX can be 32 bit */
 723     if (nearest_delta_ms > ULONG_MAX) {
 724         nearest_delta_ms = ULONG_MAX;
 725     }
 726     success = ChangeTimerQueueTimer(NULL,
 727                                     hTimer,
 728                                     (unsigned long) nearest_delta_ms,
 729                                     3600000);
 730
 731     if (!success) {
 732         fprintf(stderr, "Failed to rearm win32 alarm timer: %ld\n",
 733                 GetLastError());
 734         exit(-1);
 735     }
 736
 737 }
 738
 739 #endif /* _WIN32 */
 740
 741 static void quit_timers(void)
 742 {
 743     struct qemu_alarm_timer *t = alarm_timer;
 744     alarm_timer = NULL;
 745     t->stop(t);
 746 }
 747
 748 int init_timer_alarm(void)
 749 {
 750     struct qemu_alarm_timer *t = NULL;
 751     int i, err = -1;
 752
 753     for (i = 0; alarm_timers[i].name; i++) {
 754         t = &alarm_timers[i];
 755
 756         err = t->start(t);
 757         if (!err)
 758             break;
 759     }
 760
 761     if (err) {
 762         err = -ENOENT;
 763         goto fail;
 764     }
 765
 766     /* first event is at time 0 */
 767     atexit(quit_timers);
 768     t->pending = true;
 769     alarm_timer = t;
 770
 771     return 0;
 772
 773 fail:
 774     return err;
 775 }
 776