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vbox: improve virtual time accuracy 

Fixes #1411
This commit is contained in:
Christian Prochaska 2015-02-09 17:06:28 +01:00 committed by Christian Helmuth
parent a31378476d
commit 679ae1dd14
1 changed files with 23 additions and 37 deletions
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60
repos/ports/src/virtualbox/sup.cc
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@ -15,6 +15,7 @@
#include <os/attached_ram_dataspace.h>
#include <base/semaphore.h>
#include <os/timed_semaphore.h>
#include <trace/timestamp.h>
/* Genode/Virtualbox includes */
#include "sup.h"
@ -22,6 +23,7 @@
/* VirtualBox includes */
#include <iprt/semaphore.h>
#include <iprt/ldr.h>
#include <iprt/uint128.h>
#include <VBox/err.h>
@ -53,47 +55,31 @@ class Periodic_GIP : public Genode::Alarm {
* instable results when the timer service is using the Genode PIC
* driver as done for base-nova currently.
*/
static unsigned long long tsc_last = 0;
Genode::uint32_t now_low, now_high;
asm volatile("rdtsc" : "=a"(now_low), "=d"(now_high) : : "memory");
static uint64_t tsc_reference = Genode::Trace::timestamp();
Genode::uint64_t tsc_current = now_high;
tsc_current <<= 32;
tsc_current |= now_low;
Genode::uint64_t tsc_current = Genode::Trace::timestamp() - tsc_reference;
Genode::uint64_t elapsed_tsc;
Genode::uint32_t elapsed_ms;
enum { BOGUS_MULTIPLIER = 10 };
/*
* Convert tsc to nanoseconds.
*
* There is no 'uint128_t' type on x86_32, so we use the 128-bit type
* and functions provided by VirtualBox.
*
* nanots128 = tsc_current * 1000*1000*1000 / genode_cpu_hz()
*
*/
/* handle wrap around, backwards running tsc and too bogus timeouts */
if (tsc_current < tsc_last ||
tsc_current - tsc_last > BOGUS_MULTIPLIER * UPDATE_MS * genode_cpu_hz() / 1000) {
/*
if (tsc_current < tsc_last)
PDBG("bogus timeout - set fixed to %lums - calculated ms %llu "
" - time wrapped", UPDATE_MS,
(tsc_current - tsc_last) * 1000 / genode_cpu_hz());
else
PDBG("bogus timeout - set fixed to %lums - calculated ms %llu "
" > %u * %lums", UPDATE_MS,
(tsc_current - tsc_last) * 1000 / genode_cpu_hz(),
BOGUS_MULTIPLIER, UPDATE_MS);
*/
elapsed_ms = UPDATE_MS;
elapsed_tsc = UPDATE_MS * genode_cpu_hz() / 1000;
} else {
elapsed_tsc = tsc_current - tsc_last;
elapsed_ms = elapsed_tsc * 1000 / genode_cpu_hz();
}
Genode::uint64_t elapsed_nanots = 1000ULL * 1000 * elapsed_ms;
tsc_last = tsc_current;
RTUINT128U nanots128;
RTUInt128AssignU64(&nanots128, tsc_current);
RTUINT128U multiplier;
RTUInt128AssignU32(&multiplier, 1000*1000*1000);
RTUInt128AssignMul(&nanots128, &multiplier);
RTUINT128U divisor;
RTUInt128AssignU64(&divisor, genode_cpu_hz());
RTUInt128AssignDiv(&nanots128, &divisor);
SUPGIPCPU *cpu = &g_pSUPGlobalInfoPage->aCPUs[0];
@ -103,8 +89,8 @@ class Periodic_GIP : public Genode::Alarm {
*/
ASMAtomicIncU32(&cpu->u32TransactionId);
cpu->u64NanoTS += elapsed_nanots;
cpu->u64TSC += elapsed_tsc;
cpu->u64TSC = tsc_current;
cpu->u64NanoTS = nanots128.s.Lo;
/*
* Transaction id must be incremented before and after update,