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/* $Id: timesupref.h $ */
/** @file
* IPRT - Time using SUPLib, the C Code Template.
*/
/*
* Copyright (C) 2006-2011 Oracle Corporation
*
* This file is part of VirtualBox Open Source Edition (OSE), as
* available from http://www.virtualbox.org. This file is free software;
* you can redistribute it and/or modify it under the terms of the GNU
* General Public License (GPL) as published by the Free Software
* Foundation, in version 2 as it comes in the "COPYING" file of the
* VirtualBox OSE distribution. VirtualBox OSE is distributed in the
* hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
*
* The contents of this file may alternatively be used under the terms
* of the Common Development and Distribution License Version 1.0
* (CDDL) only, as it comes in the "COPYING.CDDL" file of the
* VirtualBox OSE distribution, in which case the provisions of the
* CDDL are applicable instead of those of the GPL.
*
* You may elect to license modified versions of this file under the
* terms and conditions of either the GPL or the CDDL or both.
*/
/**
* The C reference implementation of the assembly routines.
*
* Calculate NanoTS using the information in the global information page (GIP)
* which the support library (SUPLib) exports.
*
* This function guarantees that the returned timestamp is later (in time) than
* any previous calls in the same thread.
*
* @remark The way the ever increasing time guarantee is currently implemented means
* that if you call this function at a frequency higher than 1GHz you're in for
* trouble. We currently assume that no idiot will do that for real life purposes.
*
* @returns Nanosecond timestamp.
* @param pData Pointer to the data structure.
*/
RTDECL(uint64_t) rtTimeNanoTSInternalRef(PRTTIMENANOTSDATA pData)
{
uint64_t u64Delta;
uint32_t u32NanoTSFactor0;
uint64_t u64TSC;
uint64_t u64NanoTS;
uint32_t u32UpdateIntervalTSC;
uint64_t u64PrevNanoTS;
/*
* Read the GIP data and the previous value.
*/
for (;;)
{
PSUPGLOBALINFOPAGE pGip = g_pSUPGlobalInfoPage;
#ifdef IN_RING3
if (RT_UNLIKELY(!pGip || pGip->u32Magic != SUPGLOBALINFOPAGE_MAGIC))
return pData->pfnRediscover(pData);
#endif
#ifdef ASYNC_GIP
uint8_t u8ApicId = ASMGetApicId();
PSUPGIPCPU pGipCpu = &pGip->aCPUs[pGip->aiCpuFromApicId[u8ApicId]];
#else
PSUPGIPCPU pGipCpu = &pGip->aCPUs[0];
#endif
#ifdef NEED_TRANSACTION_ID
uint32_t u32TransactionId = pGipCpu->u32TransactionId;
uint32_t volatile Tmp1;
ASMAtomicXchgU32(&Tmp1, u32TransactionId);
#endif
u32UpdateIntervalTSC = pGipCpu->u32UpdateIntervalTSC;
u64NanoTS = pGipCpu->u64NanoTS;
u64TSC = pGipCpu->u64TSC;
u32NanoTSFactor0 = pGip->u32UpdateIntervalNS;
u64Delta = ASMReadTSC();
u64PrevNanoTS = ASMAtomicReadU64(pData->pu64Prev);
#ifdef NEED_TRANSACTION_ID
# ifdef ASYNC_GIP
if (RT_UNLIKELY(u8ApicId != ASMGetApicId()))
continue;
# elif !defined(RT_ARCH_X86)
uint32_t volatile Tmp2;
ASMAtomicXchgU32(&Tmp2, u64Delta);
# endif
if (RT_UNLIKELY( pGipCpu->u32TransactionId != u32TransactionId
|| (u32TransactionId & 1)))
continue;
#endif
break;
}
/*
* Calc NanoTS delta.
*/
u64Delta -= u64TSC;
if (RT_UNLIKELY(u64Delta > u32UpdateIntervalTSC))
{
/*
* We've expired the interval, cap it. If we're here for the 2nd
* time without any GIP update in-between, the checks against
* *pu64Prev below will force 1ns stepping.
*/
pData->cExpired++;
u64Delta = u32UpdateIntervalTSC;
}
#if !defined(_MSC_VER) || defined(RT_ARCH_AMD64) /* GCC makes very pretty code from these two inline calls, while MSC cannot. */
u64Delta = ASMMult2xU32RetU64((uint32_t)u64Delta, u32NanoTSFactor0);
u64Delta = ASMDivU64ByU32RetU32(u64Delta, u32UpdateIntervalTSC);
#else
__asm
{
mov eax, dword ptr [u64Delta]
mul dword ptr [u32NanoTSFactor0]
div dword ptr [u32UpdateIntervalTSC]
mov dword ptr [u64Delta], eax
xor edx, edx
mov dword ptr [u64Delta + 4], edx
}
#endif
/*
* Calculate the time and compare it with the previously returned value.
*/
u64NanoTS += u64Delta;
uint64_t u64DeltaPrev = u64NanoTS - u64PrevNanoTS;
if (RT_LIKELY( u64DeltaPrev > 0
&& u64DeltaPrev < UINT64_C(86000000000000) /* 24h */))
/* Frequent - less than 24h since last call. */;
else if (RT_LIKELY( (int64_t)u64DeltaPrev <= 0
&& (int64_t)u64DeltaPrev + u32NanoTSFactor0 * 2 >= 0))
{
/* Occasional - u64NanoTS is in the recent 'past' relative the previous call. */
ASMAtomicIncU32(&pData->c1nsSteps);
u64NanoTS = u64PrevNanoTS + 1;
}
else if (!u64PrevNanoTS)
/* We're resuming (see TMVirtualResume). */;
else
{
/* Something has gone bust, if negative offset it's real bad. */
ASMAtomicIncU32(&pData->cBadPrev);
pData->pfnBad(pData, u64NanoTS, u64DeltaPrev, u64PrevNanoTS);
}
if (RT_UNLIKELY(!ASMAtomicCmpXchgU64(pData->pu64Prev, u64NanoTS, u64PrevNanoTS)))
{
/*
* Attempt updating the previous value, provided we're still ahead of it.
*
* There is no point in recalculating u64NanoTS because we got preempted or if
* we raced somebody while the GIP was updated, since these are events
* that might occur at any point in the return path as well.
*/
pData->cUpdateRaces++;
for (int cTries = 25; cTries > 0; cTries--)
{
u64PrevNanoTS = ASMAtomicReadU64(pData->pu64Prev);
if (u64PrevNanoTS >= u64NanoTS)
break;
if (ASMAtomicCmpXchgU64(pData->pu64Prev, u64NanoTS, u64PrevNanoTS))
break;
}
}
return u64NanoTS;
}
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