/**
* Gets the next deadline in host CPU clock ticks and the TSC offset if we can
* use the raw TSC.
*
* @returns The number of host CPU clock ticks to the next timer deadline.
* @param pVM The cross context VM structure.
* @param pVCpu The cross context virtual CPU structure of the calling EMT.
* @param poffRealTsc The offset against the TSC of the current host CPU,
* if pfOffsettedTsc is set to true.
* @param pfOffsettedTsc Where to return whether TSC offsetting can be used.
* @param pfParavirtTsc Where to return whether paravirt TSC is enabled.
*
* @thread EMT(pVCpu).
* @see TMCpuTickCanUseRealTSC().
*/
VMM_INT_DECL(uint64_t) TMCpuTickGetDeadlineAndTscOffset(PVM pVM, PVMCPU pVCpu, uint64_t *poffRealTsc,
bool *pfOffsettedTsc, bool *pfParavirtTsc)
{
Assert(pVCpu->tm.s.fTSCTicking || DBGFIsStepping(pVCpu));
*pfParavirtTsc = pVM->tm.s.fParavirtTscEnabled;
/*
* Same logic as in TMCpuTickCanUseRealTSC.
*/
if (pVM->tm.s.enmTSCMode == TMTSCMODE_REAL_TSC_OFFSET)
{
/** @todo We should negate both deltas! It's soo weird that we do the
* exact opposite of what the hardware implements. */
#ifdef IN_RING3
*poffRealTsc = 0 - pVCpu->tm.s.offTSCRawSrc - SUPGetTscDelta();
#else
*poffRealTsc = 0 - pVCpu->tm.s.offTSCRawSrc - SUPGetTscDeltaByCpuSetIndex(pVCpu->iHostCpuSet);
#endif
*pfOffsettedTsc = true;
return tmCpuCalcTicksToDeadline(pVCpu, TMVirtualSyncGetNsToDeadline(pVM));
}
/*
* Same logic as in TMCpuTickCanUseRealTSC.
*/
if ( pVM->tm.s.enmTSCMode == TMTSCMODE_DYNAMIC
&& !pVM->tm.s.fVirtualSyncCatchUp
&& RT_LIKELY(pVM->tm.s.fVirtualSyncTicking)
&& !pVM->tm.s.fVirtualWarpDrive)
{
/* The source is the timer synchronous virtual clock. */
uint64_t cNsToDeadline;
uint64_t u64NowVirtSync = TMVirtualSyncGetWithDeadlineNoCheck(pVM, &cNsToDeadline);
uint64_t u64Now = u64NowVirtSync != TMCLOCK_FREQ_VIRTUAL /* what's the use of this? */
? ASMMultU64ByU32DivByU32(u64NowVirtSync, pVM->tm.s.cTSCTicksPerSecond, TMCLOCK_FREQ_VIRTUAL)
: u64NowVirtSync;
u64Now -= pVCpu->tm.s.offTSCRawSrc;
*poffRealTsc = u64Now - ASMReadTSC();
*pfOffsettedTsc = u64Now >= pVCpu->tm.s.u64TSCLastSeen;
return tmCpuCalcTicksToDeadline(pVCpu, cNsToDeadline);
}
#ifdef VBOX_WITH_STATISTICS
tmCpuTickRecordOffsettedTscRefusal(pVM, pVCpu);
#endif
*pfOffsettedTsc = false;
*poffRealTsc = 0;
return tmCpuCalcTicksToDeadline(pVCpu, TMVirtualSyncGetNsToDeadline(pVM));
}
/**
* Checks if AMD-V / VT-x can use an offsetted hardware TSC or not.
*
* @returns true/false accordingly.
* @param pVM The cross context VM structure.
* @param pVCpu The cross context virtual CPU structure.
* @param poffRealTsc The offset against the TSC of the current host CPU,
* if pfOffsettedTsc is set to true.
* @param pfParavirtTsc Where to return whether paravirt TSC is enabled.
*
* @thread EMT(pVCpu).
* @see TMCpuTickGetDeadlineAndTscOffset().
*/
VMM_INT_DECL(bool) TMCpuTickCanUseRealTSC(PVM pVM, PVMCPU pVCpu, uint64_t *poffRealTsc, bool *pfParavirtTsc)
{
Assert(pVCpu->tm.s.fTSCTicking || DBGFIsStepping(pVCpu));
*pfParavirtTsc = pVM->tm.s.fParavirtTscEnabled;
/*
* In real TSC mode it's easy, we just need the delta & offTscRawSrc and
* the CPU will add them to RDTSC and RDTSCP at runtime.
*
* In tmCpuTickGetInternal we do:
* SUPReadTsc() - pVCpu->tm.s.offTSCRawSrc;
* Where SUPReadTsc() does:
* ASMReadTSC() - pGipCpu->i64TscDelta;
* Which means tmCpuTickGetInternal actually does:
* ASMReadTSC() - pGipCpu->i64TscDelta - pVCpu->tm.s.offTSCRawSrc;
* So, the offset to be ADDED to RDTSC[P] is:
* offRealTsc = -(pGipCpu->i64TscDelta + pVCpu->tm.s.offTSCRawSrc)
*/
if (pVM->tm.s.enmTSCMode == TMTSCMODE_REAL_TSC_OFFSET)
{
/** @todo We should negate both deltas! It's soo weird that we do the
* exact opposite of what the hardware implements. */
#ifdef IN_RING3
*poffRealTsc = 0 - pVCpu->tm.s.offTSCRawSrc - SUPGetTscDelta();
#else
*poffRealTsc = 0 - pVCpu->tm.s.offTSCRawSrc - SUPGetTscDeltaByCpuSetIndex(pVCpu->iHostCpuSet);
#endif
return true;
}
/*
* We require:
* 1. A fixed TSC, this is checked at init time.
* 2. That the TSC is ticking (we shouldn't be here if it isn't)
* 3. Either that we're using the real TSC as time source or
* a) we don't have any lag to catch up, and
* b) the virtual sync clock hasn't been halted by an expired timer, and
* c) we're not using warp drive (accelerated virtual guest time).
*/
if ( pVM->tm.s.enmTSCMode == TMTSCMODE_DYNAMIC
&& !pVM->tm.s.fVirtualSyncCatchUp
&& RT_LIKELY(pVM->tm.s.fVirtualSyncTicking)
&& !pVM->tm.s.fVirtualWarpDrive)
{
/* The source is the timer synchronous virtual clock. */
uint64_t u64Now = tmCpuTickGetRawVirtual(pVM, false /* don't check for pending timers */)
- pVCpu->tm.s.offTSCRawSrc;
/** @todo When we start collecting statistics on how much time we spend executing
* guest code before exiting, we should check this against the next virtual sync
* timer timeout. If it's lower than the avg. length, we should trap rdtsc to increase
* the chance that we'll get interrupted right after the timer expired. */
if (u64Now >= pVCpu->tm.s.u64TSCLastSeen)
{
*poffRealTsc = u64Now - ASMReadTSC();
return true; /** @todo count this? */
}
}
#ifdef VBOX_WITH_STATISTICS
tmCpuTickRecordOffsettedTscRefusal(pVM, pVCpu);
#endif
return false;
}