void qemu_clock_warp(QEMUClock *clock)
{
int64_t deadline;
/*
* There are too many global variables to make the "warp" behavior
* applicable to other clocks. But a clock argument removes the
* need for if statements all over the place.
*/
if (clock != vm_clock || !use_icount) {
return;
}
/*
* If the CPUs have been sleeping, advance the vm_clock timer now. This
* ensures that the deadline for the timer is computed correctly below.
* This also makes sure that the insn counter is synchronized before the
* CPU starts running, in case the CPU is woken by an event other than
* the earliest vm_clock timer.
*/
icount_warp_rt(NULL);
if (!all_cpu_threads_idle() || !qemu_clock_has_timers(vm_clock)) {
qemu_del_timer(icount_warp_timer);
return;
}
if (qtest_enabled()) {
/* When testing, qtest commands advance icount. */
return;
}
vm_clock_warp_start = qemu_get_clock_ns(rt_clock);
deadline = qemu_clock_deadline(vm_clock);
if (deadline > 0) {
/*
* Ensure the vm_clock proceeds even when the virtual CPU goes to
* sleep. Otherwise, the CPU might be waiting for a future timer
* interrupt to wake it up, but the interrupt never comes because
* the vCPU isn't running any insns and thus doesn't advance the
* vm_clock.
*
* An extreme solution for this problem would be to never let VCPUs
* sleep in icount mode if there is a pending vm_clock timer; rather
* time could just advance to the next vm_clock event. Instead, we
* do stop VCPUs and only advance vm_clock after some "real" time,
* (related to the time left until the next event) has passed. This
* rt_clock timer will do this. This avoids that the warps are too
* visible externally---for example, you will not be sending network
* packets continuously instead of every 100ms.
*/
qemu_mod_timer(icount_warp_timer, vm_clock_warp_start + deadline);
} else {
qemu_notify_event();
}
}
void qemu_clock_warp(QEMUClockType type)
{
int64_t deadline;
/*
* There are too many global variables to make the "warp" behavior
* applicable to other clocks. But a clock argument removes the
* need for if statements all over the place.
*/
if (type != QEMU_CLOCK_VIRTUAL || !use_icount) {
return;
}
/*
* If the CPUs have been sleeping, advance QEMU_CLOCK_VIRTUAL timer now.
* This ensures that the deadline for the timer is computed correctly below.
* This also makes sure that the insn counter is synchronized before the
* CPU starts running, in case the CPU is woken by an event other than
* 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);
return;
}
if (qtest_enabled()) {
/* When testing, qtest commands advance icount. */
return;
}
vm_clock_warp_start = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
/* We want to use the earliest deadline from ALL vm_clocks */
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) {
/*
* Ensure QEMU_CLOCK_VIRTUAL proceeds even when the virtual CPU goes to
* sleep. Otherwise, the CPU might be waiting for a future timer
* interrupt to wake it up, but the interrupt never comes because
* the vCPU isn't running any insns and thus doesn't advance the
* QEMU_CLOCK_VIRTUAL.
*
* An extreme solution for this problem would be to never let VCPUs
* sleep in icount mode if there is a pending QEMU_CLOCK_VIRTUAL
* timer; rather time could just advance to the next QEMU_CLOCK_VIRTUAL
* event. Instead, we do stop VCPUs and only advance QEMU_CLOCK_VIRTUAL
* after some e"real" time, (related to the time left until the next
* event) has passed. The QEMU_CLOCK_REALTIME timer will do this.
* This avoids that the warps are visible externally; for example,
* you will not be sending network packets continuously instead of
* every 100ms.
*/
timer_mod(icount_warp_timer, vm_clock_warp_start + deadline);
} else if (deadline == 0) {
qemu_clock_notify(QEMU_CLOCK_VIRTUAL);
}
}
