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vbox: periodic timer based on absolute timestamps

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Before timestamps where calculated as durations since current wakeup
which introduces a systematical drift.
This commit is contained in:
Christian Helmuth 2019-12-02 15:38:27 +01:00 committed by Norman Feske
parent 604f4c666b
commit 8d60bc11b5
1 changed files with 7 additions and 8 deletions
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15
repos/ports/src/virtualbox5/spec/nova/sup.cc
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@ -711,21 +711,20 @@ void genode_update_tsc(void (*update_func)(void), Genode::uint64_t update_us)
using namespace Genode;
using namespace Nova;
enum { TSC_FACTOR = 1000ULL };
Trace::Timestamp const ticks_per_us = genode_cpu_hz() / (1000*1000);
Trace::Timestamp const ticks_per_update = ticks_per_us * update_us;
Trace::Timestamp const ticks_min_sleep = ticks_per_us * 100;
Trace::Timestamp wakeup_absolute = Trace::timestamp();
Genode::addr_t sem = Thread::myself()->native_thread().exc_pt_sel + Nova::SM_SEL_EC;
unsigned long tsc_khz = (genode_cpu_hz() / 1000) / TSC_FACTOR;
Trace::Timestamp us_64 = update_us;
for (;;) {
update_func();
Trace::Timestamp now = Trace::timestamp();
wakeup_absolute = max(wakeup_absolute + ticks_per_update,
Trace::timestamp() + ticks_min_sleep);
/* block until timeout fires or it gets canceled */
unsigned long long tsc_absolute = now + us_64 * tsc_khz;
Genode::uint8_t res = sm_ctrl(sem, SEMAPHORE_DOWN, tsc_absolute);
Genode::uint8_t res = sm_ctrl(sem, SEMAPHORE_DOWN, wakeup_absolute);
if (res != Nova::NOVA_OK && res != Nova::NOVA_TIMEOUT)
nova_die();
}