/***********************************************************/
/* guest cycle counter */
+/* Protected by TimersState seqlock */
+
+/* Compensate for varying guest execution speed. */
+static int64_t qemu_icount_bias;
+static int64_t vm_clock_warp_start;
/* Conversion factor from emulated instructions to virtual clock ticks. */
static int icount_time_shift;
/* Arbitrarily pick 1MIPS as the minimum allowable speed. */
#define MAX_ICOUNT_SHIFT 10
-/* Compensate for varying guest execution speed. */
-static int64_t qemu_icount_bias;
+
+/* Only written by TCG thread */
+static int64_t qemu_icount;
+
static QEMUTimer *icount_rt_timer;
static QEMUTimer *icount_vm_timer;
static QEMUTimer *icount_warp_timer;
-static int64_t vm_clock_warp_start;
-static int64_t qemu_icount;
typedef struct TimersState {
/* Protected by BQL. */
static TimersState timers_state;
/* Return the virtual CPU time, based on the instruction counter. */
-int64_t cpu_get_icount(void)
+static int64_t cpu_get_icount_locked(void)
{
int64_t icount;
CPUState *cpu = current_cpu;
return qemu_icount_bias + (icount << icount_time_shift);
}
+int64_t cpu_get_icount(void)
+{
+ int64_t icount;
+ unsigned start;
+
+ do {
+ start = seqlock_read_begin(&timers_state.vm_clock_seqlock);
+ icount = cpu_get_icount_locked();
+ } while (seqlock_read_retry(&timers_state.vm_clock_seqlock, start));
+
+ return icount;
+}
+
/* return the host CPU cycle counter and handle stop/restart */
/* Caller must hold the BQL */
int64_t cpu_get_ticks(void)
int64_t cur_time;
int64_t cur_icount;
int64_t delta;
+
+ /* Protected by TimersState mutex. */
static int64_t last_delta;
+
/* If the VM is not running, then do nothing. */
if (!runstate_is_running()) {
return;
}
- cur_time = cpu_get_clock();
- cur_icount = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+
+ seqlock_write_lock(&timers_state.vm_clock_seqlock);
+ cur_time = cpu_get_clock_locked();
+ cur_icount = cpu_get_icount_locked();
+
delta = cur_icount - cur_time;
/* FIXME: This is a very crude algorithm, somewhat prone to oscillation. */
if (delta > 0
}
last_delta = delta;
qemu_icount_bias = cur_icount - (qemu_icount << icount_time_shift);
+ seqlock_write_unlock(&timers_state.vm_clock_seqlock);
}
static void icount_adjust_rt(void *opaque)
static void icount_warp_rt(void *opaque)
{
- if (vm_clock_warp_start == -1) {
+ /* The icount_warp_timer is rescheduled soon after vm_clock_warp_start
+ * changes from -1 to another value, so the race here is okay.
+ */
+ if (atomic_read(&vm_clock_warp_start) == -1) {
return;
}
+ seqlock_write_lock(&timers_state.vm_clock_seqlock);
if (runstate_is_running()) {
int64_t clock = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
- int64_t warp_delta = clock - vm_clock_warp_start;
- if (use_icount == 1) {
- qemu_icount_bias += warp_delta;
- } else {
+ int64_t warp_delta;
+
+ warp_delta = clock - vm_clock_warp_start;
+ if (use_icount == 2) {
/*
* In adaptive mode, do not let QEMU_CLOCK_VIRTUAL run too
* far ahead of real time.
*/
- int64_t cur_time = cpu_get_clock();
- int64_t cur_icount = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+ int64_t cur_time = cpu_get_clock_locked();
+ int64_t cur_icount = cpu_get_icount_locked();
int64_t delta = cur_time - cur_icount;
- qemu_icount_bias += MIN(warp_delta, delta);
- }
- if (qemu_clock_expired(QEMU_CLOCK_VIRTUAL)) {
- qemu_clock_notify(QEMU_CLOCK_VIRTUAL);
+ warp_delta = MIN(warp_delta, delta);
}
+ qemu_icount_bias += warp_delta;
}
vm_clock_warp_start = -1;
+ seqlock_write_unlock(&timers_state.vm_clock_seqlock);
+
+ if (qemu_clock_expired(QEMU_CLOCK_VIRTUAL)) {
+ qemu_clock_notify(QEMU_CLOCK_VIRTUAL);
+ }
}
void qtest_clock_warp(int64_t dest)
while (clock < dest) {
int64_t deadline = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL);
int64_t warp = MIN(dest - clock, deadline);
+ seqlock_write_lock(&timers_state.vm_clock_seqlock);
qemu_icount_bias += warp;
+ seqlock_write_unlock(&timers_state.vm_clock_seqlock);
+
qemu_clock_run_timers(QEMU_CLOCK_VIRTUAL);
clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
}
void qemu_clock_warp(QEMUClockType type)
{
+ int64_t clock;
int64_t deadline;
/*
* the earliest QEMU_CLOCK_VIRTUAL timer.
*/
icount_warp_rt(NULL);
- if (!all_cpu_threads_idle() || !qemu_clock_has_timers(QEMU_CLOCK_VIRTUAL)) {
- timer_del(icount_warp_timer);
+ timer_del(icount_warp_timer);
+ if (!all_cpu_threads_idle()) {
return;
}
return;
}
- vm_clock_warp_start = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
/* We want to use the earliest deadline from ALL vm_clocks */
+ clock = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
deadline = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL);
-
- /* Maintain prior (possibly buggy) behaviour where if no deadline
- * was set (as there is no QEMU_CLOCK_VIRTUAL timer) or it is more than
- * INT32_MAX nanoseconds ahead, we still use INT32_MAX
- * nanoseconds.
- */
- if ((deadline < 0) || (deadline > INT32_MAX)) {
- deadline = INT32_MAX;
+ if (deadline < 0) {
+ return;
}
if (deadline > 0) {
* you will not be sending network packets continuously instead of
* every 100ms.
*/
- timer_mod(icount_warp_timer, vm_clock_warp_start + deadline);
+ seqlock_write_lock(&timers_state.vm_clock_seqlock);
+ if (vm_clock_warp_start == -1 || vm_clock_warp_start > clock) {
+ vm_clock_warp_start = clock;
+ }
+ seqlock_write_unlock(&timers_state.vm_clock_seqlock);
+ timer_mod_anticipate(icount_warp_timer, clock + deadline);
} else if (deadline == 0) {
qemu_clock_notify(QEMU_CLOCK_VIRTUAL);
}
projects / qemu.git / blobdiff