[Qemu-devel] [PATCH] [RFC] aio/timers: Drop alarm timers; introduce QEMUClock to AioContext; run timers in aio_poll

[Alex Bligh]

[ This is a patch for RFC purposes only. It is compile tested on Linux x86_64 
only
and passes make check (or rather did before make check started dying in the
boot order test - different bug). I'd like to know whether I'm going in
the right direction ]

We no longer need alarm timers to trigger QEMUTimer as we'll be polling
them in aio_poll.

Remove static declaration from qemu_new_clock and introduce qemu_free_clock.

Maintain a list of QEMUClocks.

Introduce qemu_clock_deadline_ns and qemu_clock_deadine_all_ns which calculate 
how
long aio_poll etc. should wait, plus (for the time being) a conversion to 
milliseconds.

Make qemu_run_timers return a bool to indicate progress.

Add QEMUClock to AioContext.

Run timers attached to clock in aio_poll

Signed-off-by: Alex Bligh <address@hidden>
---
 aio-posix.c          |   16 +-
 aio-win32.c          |   20 +-
 async.c              |    2 +
 include/block/aio.h  |    5 +
 include/qemu/timer.h |   15 +-
 main-loop.c          |    9 +-
 qemu-timer.c         |  599 ++++++++------------------------------------------
 vl.c                 |    5 +-
 8 files changed, 150 insertions(+), 521 deletions(-)

diff --git a/aio-posix.c b/aio-posix.c
index b68eccd..6401259 100644
--- a/aio-posix.c
+++ b/aio-posix.c
@@ -173,6 +173,7 @@ bool aio_poll(AioContext *ctx, bool blocking)
 {
     AioHandler *node;
     int ret;
+    int timeout;
     bool busy, progress;
 
     progress = false;
@@ -195,6 +196,9 @@ bool aio_poll(AioContext *ctx, bool blocking)
         return true;
     }
 
+    /* Run our timers */
+    progress |= qemu_run_timers(ctx->clock);
+
     ctx->walking_handlers++;
 
     g_array_set_size(ctx->pollfds, 0);
@@ -232,9 +236,10 @@ bool aio_poll(AioContext *ctx, bool blocking)
     }
 
     /* wait until next event */
+    timeout = qemu_timeout_ns_to_ms(qemu_clock_deadline_all_ns());
     ret = g_poll((GPollFD *)ctx->pollfds->data,
                  ctx->pollfds->len,
-                 blocking ? -1 : 0);
+                 blocking ? timeout : 0);
 
     /* if we have any readable fds, dispatch event */
     if (ret > 0) {
@@ -250,6 +255,15 @@ bool aio_poll(AioContext *ctx, bool blocking)
         }
     }
 
+    if (blocking) {
+        /* Run the timers a second time. We do this because otherwise aio_wait
+         * will not note progress - and will stop a drain early - if we have
+         * a timer that was not ready to run entering g_poll but is ready
+         * after g_poll. This will only do anything if a timer has expired.
+         */
+        progress |= qemu_run_timers(ctx->clock);
+    }
+
     assert(progress || busy);
     return true;
 }
diff --git a/aio-win32.c b/aio-win32.c
index 38723bf..68343ba 100644
--- a/aio-win32.c
+++ b/aio-win32.c
@@ -98,6 +98,7 @@ bool aio_poll(AioContext *ctx, bool blocking)
     HANDLE events[MAXIMUM_WAIT_OBJECTS + 1];
     bool busy, progress;
     int count;
+    int timeout;
 
     progress = false;
 
@@ -111,6 +112,9 @@ bool aio_poll(AioContext *ctx, bool blocking)
         progress = true;
     }
 
+    /* Run timers */
+    progress |= qemu_run_timers(ctx->clock);
+
     /*
      * Then dispatch any pending callbacks from the GSource.
      *
@@ -174,8 +178,11 @@ bool aio_poll(AioContext *ctx, bool blocking)
 
     /* wait until next event */
     while (count > 0) {
-        int timeout = blocking ? INFINITE : 0;
-        int ret = WaitForMultipleObjects(count, events, FALSE, timeout);
+        int ret;
+
+        timeout = blocking ?
+            qemu_timeout_ns_to_ms(qemu_clock_deadline_all_ns()) : 0;
+        ret = WaitForMultipleObjects(count, events, FALSE, timeout);
 
         /* if we have any signaled events, dispatch event */
         if ((DWORD) (ret - WAIT_OBJECT_0) >= count) {
@@ -214,6 +221,15 @@ bool aio_poll(AioContext *ctx, bool blocking)
         events[ret - WAIT_OBJECT_0] = events[--count];
     }
 
+    if (blocking) {
+        /* Run the timers a second time. We do this because otherwise aio_wait
+         * will not note progress - and will stop a drain early - if we have
+         * a timer that was not ready to run entering g_poll but is ready
+         * after g_poll. This will only do anything if a timer has expired.
+         */
+        progress |= qemu_run_timers(ctx->clock);
+    }
+
     assert(progress || busy);
     return true;
 }
diff --git a/async.c b/async.c
index 90fe906..0d41431 100644
--- a/async.c
+++ b/async.c
@@ -177,6 +177,7 @@ aio_ctx_finalize(GSource     *source)
     aio_set_event_notifier(ctx, &ctx->notifier, NULL, NULL);
     event_notifier_cleanup(&ctx->notifier);
     g_array_free(ctx->pollfds, TRUE);
+    qemu_free_clock(ctx->clock);
 }
 
 static GSourceFuncs aio_source_funcs = {
@@ -215,6 +216,7 @@ AioContext *aio_context_new(void)
     aio_set_event_notifier(ctx, &ctx->notifier, 
                            (EventNotifierHandler *)
                            event_notifier_test_and_clear, NULL);
+    ctx->clock = qemu_new_clock(QEMU_CLOCK_REALTIME);
 
     return ctx;
 }
diff --git a/include/block/aio.h b/include/block/aio.h
index 1836793..0835a4d 100644
--- a/include/block/aio.h
+++ b/include/block/aio.h
@@ -41,6 +41,8 @@ typedef struct AioHandler AioHandler;
 typedef void QEMUBHFunc(void *opaque);
 typedef void IOHandler(void *opaque);
 
+typedef struct QEMUClock QEMUClock;
+
 typedef struct AioContext {
     GSource source;
 
@@ -69,6 +71,9 @@ typedef struct AioContext {
 
     /* Thread pool for performing work and receiving completion callbacks */
     struct ThreadPool *thread_pool;
+
+    /* Clock for calling timers */
+    QEMUClock *clock;
 } AioContext;
 
 /* Returns 1 if there are still outstanding AIO requests; 0 otherwise */
diff --git a/include/qemu/timer.h b/include/qemu/timer.h
index 9dd206c..0649064 100644
--- a/include/qemu/timer.h
+++ b/include/qemu/timer.h
@@ -11,6 +11,10 @@
 #define SCALE_US 1000
 #define SCALE_NS 1
 
+#define QEMU_CLOCK_REALTIME 0
+#define QEMU_CLOCK_VIRTUAL  1
+#define QEMU_CLOCK_HOST     2
+
 typedef struct QEMUClock QEMUClock;
 typedef void QEMUTimerCB(void *opaque);
 
@@ -32,10 +36,15 @@ extern QEMUClock *vm_clock;
    the virtual clock. */
 extern QEMUClock *host_clock;
 
+QEMUClock *qemu_new_clock(int type);
+void qemu_free_clock(QEMUClock *clock);
 int64_t qemu_get_clock_ns(QEMUClock *clock);
 int64_t qemu_clock_has_timers(QEMUClock *clock);
 int64_t qemu_clock_expired(QEMUClock *clock);
 int64_t qemu_clock_deadline(QEMUClock *clock);
+int64_t qemu_clock_deadline_ns(QEMUClock *clock);
+int64_t qemu_clock_deadline_all_ns(void);
+int qemu_timeout_ns_to_ms(int64_t ns);
 void qemu_clock_enable(QEMUClock *clock, bool enabled);
 void qemu_clock_warp(QEMUClock *clock);
 
@@ -53,11 +62,9 @@ bool qemu_timer_pending(QEMUTimer *ts);
 bool qemu_timer_expired(QEMUTimer *timer_head, int64_t current_time);
 uint64_t qemu_timer_expire_time_ns(QEMUTimer *ts);
 
-void qemu_run_timers(QEMUClock *clock);
-void qemu_run_all_timers(void);
-void configure_alarms(char const *opt);
+bool qemu_run_timers(QEMUClock *clock);
+bool qemu_run_all_timers(void);
 void init_clocks(void);
-int init_timer_alarm(void);
 
 int64_t cpu_get_ticks(void);
 void cpu_enable_ticks(void);
diff --git a/main-loop.c b/main-loop.c
index a44fff6..626eda2 100644
--- a/main-loop.c
+++ b/main-loop.c
@@ -131,10 +131,6 @@ int qemu_init_main_loop(void)
     GSource *src;
 
     init_clocks();
-    if (init_timer_alarm() < 0) {
-        fprintf(stderr, "could not initialize alarm timer\n");
-        exit(1);
-    }
 
     ret = qemu_signal_init();
     if (ret) {
@@ -449,6 +445,11 @@ int main_loop_wait(int nonblocking)
 {
     int ret;
     uint32_t timeout = UINT32_MAX;
+    int32_t timer_timeout = 
qemu_timeout_ns_to_ms(qemu_clock_deadline_all_ns());
+
+    if (timer_timeout >= 0) {
+        timeout = timer_timeout;
+    }
 
     if (nonblocking) {
         timeout = 0;
diff --git a/qemu-timer.c b/qemu-timer.c
index b2d95e2..e643d94 100644
--- a/qemu-timer.c
+++ b/qemu-timer.c
@@ -33,17 +33,9 @@
 #include <pthread.h>
 #endif
 
-#ifdef _WIN32
-#include <mmsystem.h>
-#endif
-
 /***********************************************************/
 /* timers */
 
-#define QEMU_CLOCK_REALTIME 0
-#define QEMU_CLOCK_VIRTUAL  1
-#define QEMU_CLOCK_HOST     2
-
 struct QEMUClock {
     QEMUTimer *active_timers;
 
@@ -52,6 +44,8 @@ struct QEMUClock {
 
     int type;
     bool enabled;
+
+    QLIST_ENTRY(QEMUClock) list;
 };
 
 struct QEMUTimer {
@@ -63,175 +57,19 @@ struct QEMUTimer {
     int scale;
 };
 
-struct qemu_alarm_timer {
-    char const *name;
-    int (*start)(struct qemu_alarm_timer *t);
-    void (*stop)(struct qemu_alarm_timer *t);
-    void (*rearm)(struct qemu_alarm_timer *t, int64_t nearest_delta_ns);
-#if defined(__linux__)
-    timer_t timer;
-    int fd;
-#elif defined(_WIN32)
-    HANDLE timer;
-#endif
-    bool expired;
-    bool pending;
-};
-
-static struct qemu_alarm_timer *alarm_timer;
+static QLIST_HEAD(, QEMUClock) qemu_clocks =
+    QLIST_HEAD_INITIALIZER(qemu_clocks);
 
 static bool qemu_timer_expired_ns(QEMUTimer *timer_head, int64_t current_time)
 {
     return timer_head && (timer_head->expire_time <= current_time);
 }
 
-static int64_t qemu_next_alarm_deadline(void)
-{
-    int64_t delta = INT64_MAX;
-    int64_t rtdelta;
-
-    if (!use_icount && vm_clock->enabled && vm_clock->active_timers) {
-        delta = vm_clock->active_timers->expire_time -
-                     qemu_get_clock_ns(vm_clock);
-    }
-    if (host_clock->enabled && host_clock->active_timers) {
-        int64_t hdelta = host_clock->active_timers->expire_time -
-                 qemu_get_clock_ns(host_clock);
-        if (hdelta < delta) {
-            delta = hdelta;
-        }
-    }
-    if (rt_clock->enabled && rt_clock->active_timers) {
-        rtdelta = (rt_clock->active_timers->expire_time -
-                 qemu_get_clock_ns(rt_clock));
-        if (rtdelta < delta) {
-            delta = rtdelta;
-        }
-    }
-
-    return delta;
-}
-
-static void qemu_rearm_alarm_timer(struct qemu_alarm_timer *t)
-{
-    int64_t nearest_delta_ns = qemu_next_alarm_deadline();
-    if (nearest_delta_ns < INT64_MAX) {
-        t->rearm(t, nearest_delta_ns);
-    }
-}
-
-/* TODO: MIN_TIMER_REARM_NS should be optimized */
-#define MIN_TIMER_REARM_NS 250000
-
-#ifdef _WIN32
-
-static int mm_start_timer(struct qemu_alarm_timer *t);
-static void mm_stop_timer(struct qemu_alarm_timer *t);
-static void mm_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
-
-static int win32_start_timer(struct qemu_alarm_timer *t);
-static void win32_stop_timer(struct qemu_alarm_timer *t);
-static void win32_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
-
-#else
-
-static int unix_start_timer(struct qemu_alarm_timer *t);
-static void unix_stop_timer(struct qemu_alarm_timer *t);
-static void unix_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
-
-#ifdef __linux__
-
-static int dynticks_start_timer(struct qemu_alarm_timer *t);
-static void dynticks_stop_timer(struct qemu_alarm_timer *t);
-static void dynticks_rearm_timer(struct qemu_alarm_timer *t, int64_t delta);
-
-#endif /* __linux__ */
-
-#endif /* _WIN32 */
-
-static struct qemu_alarm_timer alarm_timers[] = {
-#ifndef _WIN32
-#ifdef __linux__
-    {"dynticks", dynticks_start_timer,
-     dynticks_stop_timer, dynticks_rearm_timer},
-#endif
-    {"unix", unix_start_timer, unix_stop_timer, unix_rearm_timer},
-#else
-    {"mmtimer", mm_start_timer, mm_stop_timer, mm_rearm_timer},
-    {"dynticks", win32_start_timer, win32_stop_timer, win32_rearm_timer},
-#endif
-    {NULL, }
-};
-
-static void show_available_alarms(void)
-{
-    int i;
-
-    printf("Available alarm timers, in order of precedence:\n");
-    for (i = 0; alarm_timers[i].name; i++)
-        printf("%s\n", alarm_timers[i].name);
-}
-
-void configure_alarms(char const *opt)
-{
-    int i;
-    int cur = 0;
-    int count = ARRAY_SIZE(alarm_timers) - 1;
-    char *arg;
-    char *name;
-    struct qemu_alarm_timer tmp;
-
-    if (is_help_option(opt)) {
-        show_available_alarms();
-        exit(0);
-    }
-
-    arg = g_strdup(opt);
-
-    /* Reorder the array */
-    name = strtok(arg, ",");
-    while (name) {
-        for (i = 0; i < count && alarm_timers[i].name; i++) {
-            if (!strcmp(alarm_timers[i].name, name))
-                break;
-        }
-
-        if (i == count) {
-            fprintf(stderr, "Unknown clock %s\n", name);
-            goto next;
-        }
-
-        if (i < cur)
-            /* Ignore */
-            goto next;
-
-       /* Swap */
-        tmp = alarm_timers[i];
-        alarm_timers[i] = alarm_timers[cur];
-        alarm_timers[cur] = tmp;
-
-        cur++;
-next:
-        name = strtok(NULL, ",");
-    }
-
-    g_free(arg);
-
-    if (cur) {
-        /* Disable remaining timers */
-        for (i = cur; i < count; i++)
-            alarm_timers[i].name = NULL;
-    } else {
-        show_available_alarms();
-        exit(1);
-    }
-}
-
 QEMUClock *rt_clock;
 QEMUClock *vm_clock;
 QEMUClock *host_clock;
 
-static QEMUClock *qemu_new_clock(int type)
+QEMUClock *qemu_new_clock(int type)
 {
     QEMUClock *clock;
 
@@ -240,16 +78,19 @@ static QEMUClock *qemu_new_clock(int type)
     clock->enabled = true;
     clock->last = INT64_MIN;
     notifier_list_init(&clock->reset_notifiers);
+    QLIST_INSERT_HEAD(&qemu_clocks, clock, list);
     return clock;
 }
 
+void qemu_free_clock(QEMUClock *clock)
+{
+    QLIST_REMOVE(clock, list);
+    g_free(clock);
+}
+
 void qemu_clock_enable(QEMUClock *clock, bool enabled)
 {
-    bool old = clock->enabled;
     clock->enabled = enabled;
-    if (enabled && !old) {
-        qemu_rearm_alarm_timer(alarm_timer);
-    }
 }
 
 int64_t qemu_clock_has_timers(QEMUClock *clock)
@@ -268,7 +109,7 @@ int64_t qemu_clock_deadline(QEMUClock *clock)
     /* To avoid problems with overflow limit this to 2^32.  */
     int64_t delta = INT32_MAX;
 
-    if (clock->active_timers) {
+    if (clock->enabled && clock->active_timers) {
         delta = clock->active_timers->expire_time - qemu_get_clock_ns(clock);
     }
     if (delta < 0) {
@@ -277,6 +118,71 @@ int64_t qemu_clock_deadline(QEMUClock *clock)
     return delta;
 }
 
+/*
+ * As above, but return -1 for no deadline, and do not cap to 2^32
+ * as we know the result is always positive.
+ */
+
+int64_t qemu_clock_deadline_ns(QEMUClock *clock)
+{
+    int64_t delta;
+
+    if (!clock->enabled || !clock->active_timers) {
+        return -1;
+    }
+
+    delta = clock->active_timers->expire_time - qemu_get_clock_ns(clock);
+
+    if (delta <= 0) {
+        return 0;
+    }
+
+    return delta;
+}
+
+/* Return the minimum deadline across all clocks or -1 for no
+ * deadline
+ */
+int64_t qemu_clock_deadline_all_ns(void)
+{
+    QEMUClock *clock;
+    int64_t ret = -1;
+    QLIST_FOREACH(clock, &qemu_clocks, list) {
+        int64_t ns = qemu_clock_deadline_ns(clock);
+        if ((ns >= 0) && ((ret == -1) || (ns < ret))) {
+            ret = ns;
+        }
+    }
+    return ret;
+}
+
+/* Transition function to convert a nanosecond timeout to ms
+ * This will be deleted when we switch to ppoll
+ */
+int qemu_timeout_ns_to_ms(int64_t ns)
+{
+    int64_t ms;
+    if (ns < 0) {
+        return -1;
+    }
+
+    if (!ns) {
+        return 0;
+    }
+
+    /* Always round up, because it's better to wait too long than to wait too
+     * little and effectively busy-wait
+     */
+    ms = (ns + SCALE_MS - 1) / SCALE_MS;
+
+    /* To avoid overflow problems, limit this to 2^31, i.e. approx 25 days */
+    if (ms > (int64_t) INT32_MAX) {
+        ms = INT32_MAX;
+    }
+
+    return (int) ms;
+}
+
 QEMUTimer *qemu_new_timer(QEMUClock *clock, int scale,
                           QEMUTimerCB *cb, void *opaque)
 {
@@ -340,13 +246,10 @@ void qemu_mod_timer_ns(QEMUTimer *ts, int64_t expire_time)
 
     /* Rearm if necessary  */
     if (pt == &ts->clock->active_timers) {
-        if (!alarm_timer->pending) {
-            qemu_rearm_alarm_timer(alarm_timer);
-        }
         /* Interrupt execution to force deadline recalculation.  */
         qemu_clock_warp(ts->clock);
         if (use_icount) {
-            qemu_notify_event();
+            qemu_notify_event(); /* FIXME: do we need this now? */
         }
     }
 }
@@ -372,13 +275,14 @@ bool qemu_timer_expired(QEMUTimer *timer_head, int64_t 
current_time)
     return qemu_timer_expired_ns(timer_head, current_time * timer_head->scale);
 }
 
-void qemu_run_timers(QEMUClock *clock)
+bool qemu_run_timers(QEMUClock *clock)
 {
     QEMUTimer *ts;
     int64_t current_time;
+    bool progress = false;
    
     if (!clock->enabled)
-        return;
+        return progress;
 
     current_time = qemu_get_clock_ns(clock);
     for(;;) {
@@ -392,7 +296,9 @@ void qemu_run_timers(QEMUClock *clock)
 
         /* run the callback (the timer list can be modified) */
         ts->cb(ts->opaque);
+        progress = true;
     }
+    return progress;
 }
 
 int64_t qemu_get_clock_ns(QEMUClock *clock)
@@ -444,337 +350,12 @@ uint64_t qemu_timer_expire_time_ns(QEMUTimer *ts)
     return qemu_timer_pending(ts) ? ts->expire_time : -1;
 }
 
-void qemu_run_all_timers(void)
+bool qemu_run_all_timers(void)
 {
-    alarm_timer->pending = false;
-
     /* vm time timers */
-    qemu_run_timers(vm_clock);
-    qemu_run_timers(rt_clock);
-    qemu_run_timers(host_clock);
-
-    /* rearm timer, if not periodic */
-    if (alarm_timer->expired) {
-        alarm_timer->expired = false;
-        qemu_rearm_alarm_timer(alarm_timer);
-    }
-}
-
-#ifdef _WIN32
-static void CALLBACK host_alarm_handler(PVOID lpParam, BOOLEAN unused)
-#else
-static void host_alarm_handler(int host_signum)
-#endif
-{
-    struct qemu_alarm_timer *t = alarm_timer;
-    if (!t)
-       return;
-
-    t->expired = true;
-    t->pending = true;
-    qemu_notify_event();
-}
-
-#if defined(__linux__)
-
-#include "qemu/compatfd.h"
-
-static int dynticks_start_timer(struct qemu_alarm_timer *t)
-{
-    struct sigevent ev;
-    timer_t host_timer;
-    struct sigaction act;
-
-    sigfillset(&act.sa_mask);
-    act.sa_flags = 0;
-    act.sa_handler = host_alarm_handler;
-
-    sigaction(SIGALRM, &act, NULL);
-
-    /* 
-     * Initialize ev struct to 0 to avoid valgrind complaining
-     * about uninitialized data in timer_create call
-     */
-    memset(&ev, 0, sizeof(ev));
-    ev.sigev_value.sival_int = 0;
-    ev.sigev_notify = SIGEV_SIGNAL;
-#ifdef CONFIG_SIGEV_THREAD_ID
-    if (qemu_signalfd_available()) {
-        ev.sigev_notify = SIGEV_THREAD_ID;
-        ev._sigev_un._tid = qemu_get_thread_id();
-    }
-#endif /* CONFIG_SIGEV_THREAD_ID */
-    ev.sigev_signo = SIGALRM;
-
-    if (timer_create(CLOCK_REALTIME, &ev, &host_timer)) {
-        perror("timer_create");
-        return -1;
-    }
-
-    t->timer = host_timer;
-
-    return 0;
-}
-
-static void dynticks_stop_timer(struct qemu_alarm_timer *t)
-{
-    timer_t host_timer = t->timer;
-
-    timer_delete(host_timer);
-}
-
-static void dynticks_rearm_timer(struct qemu_alarm_timer *t,
-                                 int64_t nearest_delta_ns)
-{
-    timer_t host_timer = t->timer;
-    struct itimerspec timeout;
-    int64_t current_ns;
-
-    if (nearest_delta_ns < MIN_TIMER_REARM_NS)
-        nearest_delta_ns = MIN_TIMER_REARM_NS;
-
-    /* check whether a timer is already running */
-    if (timer_gettime(host_timer, &timeout)) {
-        perror("gettime");
-        fprintf(stderr, "Internal timer error: aborting\n");
-        exit(1);
-    }
-    current_ns = timeout.it_value.tv_sec * 1000000000LL + 
timeout.it_value.tv_nsec;
-    if (current_ns && current_ns <= nearest_delta_ns)
-        return;
-
-    timeout.it_interval.tv_sec = 0;
-    timeout.it_interval.tv_nsec = 0; /* 0 for one-shot timer */
-    timeout.it_value.tv_sec =  nearest_delta_ns / 1000000000;
-    timeout.it_value.tv_nsec = nearest_delta_ns % 1000000000;
-    if (timer_settime(host_timer, 0 /* RELATIVE */, &timeout, NULL)) {
-        perror("settime");
-        fprintf(stderr, "Internal timer error: aborting\n");
-        exit(1);
-    }
-}
-
-#endif /* defined(__linux__) */
-
-#if !defined(_WIN32)
-
-static int unix_start_timer(struct qemu_alarm_timer *t)
-{
-    struct sigaction act;
-
-    /* timer signal */
-    sigfillset(&act.sa_mask);
-    act.sa_flags = 0;
-    act.sa_handler = host_alarm_handler;
-
-    sigaction(SIGALRM, &act, NULL);
-    return 0;
-}
-
-static void unix_rearm_timer(struct qemu_alarm_timer *t,
-                             int64_t nearest_delta_ns)
-{
-    struct itimerval itv;
-    int err;
-
-    if (nearest_delta_ns < MIN_TIMER_REARM_NS)
-        nearest_delta_ns = MIN_TIMER_REARM_NS;
-
-    itv.it_interval.tv_sec = 0;
-    itv.it_interval.tv_usec = 0; /* 0 for one-shot timer */
-    itv.it_value.tv_sec =  nearest_delta_ns / 1000000000;
-    itv.it_value.tv_usec = (nearest_delta_ns % 1000000000) / 1000;
-    err = setitimer(ITIMER_REAL, &itv, NULL);
-    if (err) {
-        perror("setitimer");
-        fprintf(stderr, "Internal timer error: aborting\n");
-        exit(1);
-    }
-}
-
-static void unix_stop_timer(struct qemu_alarm_timer *t)
-{
-    struct itimerval itv;
-
-    memset(&itv, 0, sizeof(itv));
-    setitimer(ITIMER_REAL, &itv, NULL);
-}
-
-#endif /* !defined(_WIN32) */
-
-
-#ifdef _WIN32
-
-static MMRESULT mm_timer;
-static TIMECAPS mm_tc;
-
-static void CALLBACK mm_alarm_handler(UINT uTimerID, UINT uMsg,
-                                      DWORD_PTR dwUser, DWORD_PTR dw1,
-                                      DWORD_PTR dw2)
-{
-    struct qemu_alarm_timer *t = alarm_timer;
-    if (!t) {
-        return;
-    }
-    t->expired = true;
-    t->pending = true;
-    qemu_notify_event();
-}
-
-static int mm_start_timer(struct qemu_alarm_timer *t)
-{
-    timeGetDevCaps(&mm_tc, sizeof(mm_tc));
-    return 0;
-}
-
-static void mm_stop_timer(struct qemu_alarm_timer *t)
-{
-    if (mm_timer) {
-        timeKillEvent(mm_timer);
-    }
+    bool progress = false;
+    progress |= qemu_run_timers(vm_clock);
+    progress |= qemu_run_timers(rt_clock);
+    progress |= qemu_run_timers(host_clock);
+    return progress;
 }
-
-static void mm_rearm_timer(struct qemu_alarm_timer *t, int64_t delta)
-{
-    int64_t nearest_delta_ms = delta / 1000000;
-    if (nearest_delta_ms < mm_tc.wPeriodMin) {
-        nearest_delta_ms = mm_tc.wPeriodMin;
-    } else if (nearest_delta_ms > mm_tc.wPeriodMax) {
-        nearest_delta_ms = mm_tc.wPeriodMax;
-    }
-
-    if (mm_timer) {
-        timeKillEvent(mm_timer);
-    }
-    mm_timer = timeSetEvent((UINT)nearest_delta_ms,
-                            mm_tc.wPeriodMin,
-                            mm_alarm_handler,
-                            (DWORD_PTR)t,
-                            TIME_ONESHOT | TIME_CALLBACK_FUNCTION);
-
-    if (!mm_timer) {
-        fprintf(stderr, "Failed to re-arm win32 alarm timer\n");
-        timeEndPeriod(mm_tc.wPeriodMin);
-        exit(1);
-    }
-}
-
-static int win32_start_timer(struct qemu_alarm_timer *t)
-{
-    HANDLE hTimer;
-    BOOLEAN success;
-
-    /* If you call ChangeTimerQueueTimer on a one-shot timer (its period
-       is zero) that has already expired, the timer is not updated.  Since
-       creating a new timer is relatively expensive, set a bogus one-hour
-       interval in the dynticks case.  */
-    success = CreateTimerQueueTimer(&hTimer,
-                          NULL,
-                          host_alarm_handler,
-                          t,
-                          1,
-                          3600000,
-                          WT_EXECUTEINTIMERTHREAD);
-
-    if (!success) {
-        fprintf(stderr, "Failed to initialize win32 alarm timer: %ld\n",
-                GetLastError());
-        return -1;
-    }
-
-    t->timer = hTimer;
-    return 0;
-}
-
-static void win32_stop_timer(struct qemu_alarm_timer *t)
-{
-    HANDLE hTimer = t->timer;
-
-    if (hTimer) {
-        DeleteTimerQueueTimer(NULL, hTimer, NULL);
-    }
-}
-
-static void win32_rearm_timer(struct qemu_alarm_timer *t,
-                              int64_t nearest_delta_ns)
-{
-    HANDLE hTimer = t->timer;
-    int64_t nearest_delta_ms;
-    BOOLEAN success;
-
-    nearest_delta_ms = nearest_delta_ns / 1000000;
-    if (nearest_delta_ms < 1) {
-        nearest_delta_ms = 1;
-    }
-    /* ULONG_MAX can be 32 bit */
-    if (nearest_delta_ms > ULONG_MAX) {
-        nearest_delta_ms = ULONG_MAX;
-    }
-    success = ChangeTimerQueueTimer(NULL,
-                                    hTimer,
-                                    (unsigned long) nearest_delta_ms,
-                                    3600000);
-
-    if (!success) {
-        fprintf(stderr, "Failed to rearm win32 alarm timer: %ld\n",
-                GetLastError());
-        exit(-1);
-    }
-
-}
-
-#endif /* _WIN32 */
-
-static void quit_timers(void)
-{
-    struct qemu_alarm_timer *t = alarm_timer;
-    alarm_timer = NULL;
-    t->stop(t);
-}
-
-#ifdef CONFIG_POSIX
-static void reinit_timers(void)
-{
-    struct qemu_alarm_timer *t = alarm_timer;
-    t->stop(t);
-    if (t->start(t)) {
-        fprintf(stderr, "Internal timer error: aborting\n");
-        exit(1);
-    }
-    qemu_rearm_alarm_timer(t);
-}
-#endif /* CONFIG_POSIX */
-
-int init_timer_alarm(void)
-{
-    struct qemu_alarm_timer *t = NULL;
-    int i, err = -1;
-
-    if (alarm_timer) {
-        return 0;
-    }
-
-    for (i = 0; alarm_timers[i].name; i++) {
-        t = &alarm_timers[i];
-
-        err = t->start(t);
-        if (!err)
-            break;
-    }
-
-    if (err) {
-        err = -ENOENT;
-        goto fail;
-    }
-
-    atexit(quit_timers);
-#ifdef CONFIG_POSIX
-    pthread_atfork(NULL, NULL, reinit_timers);
-#endif
-    alarm_timer = t;
-    return 0;
-
-fail:
-    return err;
-}
-
diff --git a/vl.c b/vl.c
index 25b8f2f..612c609 100644
--- a/vl.c
+++ b/vl.c
@@ -3714,7 +3714,10 @@ int main(int argc, char **argv, char **envp)
                 old_param = 1;
                 break;
             case QEMU_OPTION_clock:
-                configure_alarms(optarg);
+                /* Once upon a time we did:
+                 *   configure_alarms(optarg);
+                 * here. This is stubbed out for compatibility.
+                 */
                 break;
             case QEMU_OPTION_startdate:
                 configure_rtc_date_offset(optarg, 1);
-- 
1.7.9.5