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cpus: allow cpu_get_ticks out of BQL

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Because of cpu_ticks_prev, we cannot use a seqlock.  But then the conversion
is even easier. :)

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2018-08-18 09:36:16 +02:00
parent 94377115b2
commit f2a4ad6d49
1 changed files with 20 additions and 15 deletions
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35
cpus.c
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@ -316,11 +316,26 @@ int64_t cpu_icount_to_ns(int64_t icount)
return icount << atomic_read(&timers_state.icount_time_shift);
}
static int64_t cpu_get_ticks_locked(void)
{
int64_t ticks = timers_state.cpu_ticks_offset;
if (timers_state.cpu_ticks_enabled) {
ticks += cpu_get_host_ticks();
}
if (timers_state.cpu_ticks_prev > ticks) {
/* Non increasing ticks may happen if the host uses software suspend. */
timers_state.cpu_ticks_offset += timers_state.cpu_ticks_prev - ticks;
ticks = timers_state.cpu_ticks_prev;
}
timers_state.cpu_ticks_prev = ticks;
return ticks;
}
/* return the time elapsed in VM between vm_start and vm_stop. Unless
* icount is active, cpu_get_ticks() uses units of the host CPU cycle
* counter.
*
* Caller must hold the BQL
*/
int64_t cpu_get_ticks(void)
{
@ -330,19 +345,9 @@ int64_t cpu_get_ticks(void)
return cpu_get_icount();
}
ticks = timers_state.cpu_ticks_offset;
if (timers_state.cpu_ticks_enabled) {
ticks += cpu_get_host_ticks();
}
if (timers_state.cpu_ticks_prev > ticks) {
/* Note: non increasing ticks may happen if the host uses
software suspend */
timers_state.cpu_ticks_offset += timers_state.cpu_ticks_prev - ticks;
ticks = timers_state.cpu_ticks_prev;
}
timers_state.cpu_ticks_prev = ticks;
qemu_spin_lock(&timers_state.vm_clock_lock);
ticks = cpu_get_ticks_locked();
qemu_spin_unlock(&timers_state.vm_clock_lock);
return ticks;
}