source: vbox/trunk/src/VBox/VMM/VMMAll/TMAllCpu.cpp@ 43667

/* $Id: TMAllCpu.cpp 41965 2012-06-29 02:52:49Z vboxsync $ */
/** @file
 * TM - Timeout Manager, CPU Time, All Contexts.
 */

/*
 * Copyright (C) 2006-2007 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.
 */


/*******************************************************************************
*   Header Files                                                               *
*******************************************************************************/
#define LOG_GROUP LOG_GROUP_TM
#include <VBox/vmm/tm.h>
#include <iprt/asm-amd64-x86.h> /* for SUPGetCpuHzFromGIP */
#include "TMInternal.h"
#include <VBox/vmm/vm.h>
#include <VBox/sup.h>

#include <VBox/param.h>
#include <VBox/err.h>
#include <iprt/asm-math.h>
#include <iprt/assert.h>
#include <VBox/log.h>


/**
 * Gets the raw cpu tick from current virtual time.
 */
DECLINLINE(uint64_t) tmCpuTickGetRawVirtual(PVM pVM, bool fCheckTimers)
{
    uint64_t u64;
    if (fCheckTimers)
        u64 = TMVirtualSyncGet(pVM);
    else
        u64 = TMVirtualSyncGetNoCheck(pVM);
    if (u64 != TMCLOCK_FREQ_VIRTUAL) /* what's the use of this test, document! */
        u64 = ASMMultU64ByU32DivByU32(u64, pVM->tm.s.cTSCTicksPerSecond, TMCLOCK_FREQ_VIRTUAL);
    return u64;
}


/**
 * Resumes the CPU timestamp counter ticking.
 *
 * @returns VBox status code.
 * @param   pVM         Pointer to the VM.
 * @param   pVCpu       Pointer to the VMCPU.
 * @internal
 */
int tmCpuTickResume(PVM pVM, PVMCPU pVCpu)
{
    if (!pVCpu->tm.s.fTSCTicking)
    {
        pVCpu->tm.s.fTSCTicking = true;
        if (pVM->tm.s.fTSCVirtualized)
        {
            /** @todo Test that pausing and resuming doesn't cause lag! (I.e. that we're
             *        unpaused before the virtual time and stopped after it. */
            if (pVM->tm.s.fTSCUseRealTSC)
                pVCpu->tm.s.offTSCRawSrc = ASMReadTSC() - pVCpu->tm.s.u64TSC;
            else
                pVCpu->tm.s.offTSCRawSrc = tmCpuTickGetRawVirtual(pVM, false /* don't check for pending timers */)
                                         - pVCpu->tm.s.u64TSC;
        }
        return VINF_SUCCESS;
    }
    AssertFailed();
    return VERR_TM_TSC_ALREADY_TICKING;
}


/**
 * Pauses the CPU timestamp counter ticking.
 *
 * @returns VBox status code.
 * @param   pVCpu       Pointer to the VMCPU.
 * @internal
 */
int tmCpuTickPause(PVMCPU pVCpu)
{
    if (pVCpu->tm.s.fTSCTicking)
    {
        pVCpu->tm.s.u64TSC = TMCpuTickGetNoCheck(pVCpu);
        pVCpu->tm.s.fTSCTicking = false;
        return VINF_SUCCESS;
    }
    AssertFailed();
    return VERR_TM_TSC_ALREADY_PAUSED;
}

/**
 * Record why we refused to use offsetted TSC.
 *
 * Used by TMCpuTickCanUseRealTSC and TMCpuTickGetDeadlineAndTscOffset.
 *
 * @param   pVM         Pointer to the VM.
 * @param   pVCpu       The current CPU.
 */
DECLINLINE(void) tmCpuTickRecordOffsettedTscRefusal(PVM pVM, PVMCPU pVCpu)
{

    /* Sample the reason for refusing. */
    if (!pVM->tm.s.fMaybeUseOffsettedHostTSC)
       STAM_COUNTER_INC(&pVM->tm.s.StatTSCNotFixed);
    else if (!pVCpu->tm.s.fTSCTicking)
       STAM_COUNTER_INC(&pVM->tm.s.StatTSCNotTicking);
    else if (!pVM->tm.s.fTSCUseRealTSC)
    {
        if (pVM->tm.s.fVirtualSyncCatchUp)
        {
           if (pVM->tm.s.u32VirtualSyncCatchUpPercentage <= 10)
               STAM_COUNTER_INC(&pVM->tm.s.StatTSCCatchupLE010);
           else if (pVM->tm.s.u32VirtualSyncCatchUpPercentage <= 25)
               STAM_COUNTER_INC(&pVM->tm.s.StatTSCCatchupLE025);
           else if (pVM->tm.s.u32VirtualSyncCatchUpPercentage <= 100)
               STAM_COUNTER_INC(&pVM->tm.s.StatTSCCatchupLE100);
           else
               STAM_COUNTER_INC(&pVM->tm.s.StatTSCCatchupOther);
        }
        else if (!pVM->tm.s.fVirtualSyncTicking)
           STAM_COUNTER_INC(&pVM->tm.s.StatTSCSyncNotTicking);
        else if (pVM->tm.s.fVirtualWarpDrive)
           STAM_COUNTER_INC(&pVM->tm.s.StatTSCWarp);
    }
}


/**
 * Checks if AMD-V / VT-x can use an offsetted hardware TSC or not.
 *
 * @returns true/false accordingly.
 * @param   pVCpu       Pointer to the VMCPU.
 * @param   poffRealTSC     The offset against the TSC of the current CPU.
 *                          Can be NULL.
 * @thread EMT.
 */
VMM_INT_DECL(bool) TMCpuTickCanUseRealTSC(PVMCPU pVCpu, uint64_t *poffRealTSC)
{
    PVM pVM = pVCpu->CTX_SUFF(pVM);

    /*
     * 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.fMaybeUseOffsettedHostTSC
        &&  RT_LIKELY(pVCpu->tm.s.fTSCTicking)
        &&  (   pVM->tm.s.fTSCUseRealTSC
             || (   !pVM->tm.s.fVirtualSyncCatchUp
                 && RT_LIKELY(pVM->tm.s.fVirtualSyncTicking)
                 && !pVM->tm.s.fVirtualWarpDrive))
       )
    {
        if (!pVM->tm.s.fTSCUseRealTSC)
        {
            /* The source is the timer synchronous virtual clock. */
            Assert(pVM->tm.s.fTSCVirtualized);

            if (poffRealTSC)
            {
                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. */
                *poffRealTSC = u64Now - ASMReadTSC();
            }
        }
        else if (poffRealTSC)
        {
            /* The source is the real TSC. */
            if (pVM->tm.s.fTSCVirtualized)
                *poffRealTSC = pVCpu->tm.s.offTSCRawSrc;
            else
                *poffRealTSC = 0;
        }
        /** @todo count this? */
        return true;
    }

#ifdef VBOX_WITH_STATISTICS
    tmCpuTickRecordOffsettedTscRefusal(pVM, pVCpu);
#endif
    return false;
}


/**
 * Calculates the number of host CPU ticks till the next virtual sync deadline.
 *
 * @note    To save work, this function will not bother calculating the accurate
 *          tick count for deadlines that are more than a second ahead.
 *
 * @returns The number of host cpu ticks to the next deadline.  Max one second.
 * @param   cNsToDeadline       The number of nano seconds to the next virtual
 *                              sync deadline.
 */
DECLINLINE(uint64_t) tmCpuCalcTicksToDeadline(uint64_t cNsToDeadline)
{
    AssertCompile(TMCLOCK_FREQ_VIRTUAL <= _4G);
    if (RT_UNLIKELY(cNsToDeadline >= TMCLOCK_FREQ_VIRTUAL))
        return SUPGetCpuHzFromGIP(g_pSUPGlobalInfoPage);
    uint64_t cTicks = ASMMultU64ByU32DivByU32(SUPGetCpuHzFromGIP(g_pSUPGlobalInfoPage),
                                              cNsToDeadline,
                                              TMCLOCK_FREQ_VIRTUAL);
    if (cTicks > 4000)
        cTicks -= 4000; /* fudge to account for overhead */
    else
        cTicks >>= 1;
    return cTicks;
}


/**
 * 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   pVCpu           The current CPU.
 * @param   poffRealTSC     The offset against the TSC of the current CPU.
 * @thread  EMT(pVCpu).
 * @remarks Superset of TMCpuTickCanUseRealTSC.
 */
VMM_INT_DECL(uint64_t) TMCpuTickGetDeadlineAndTscOffset(PVMCPU pVCpu, bool *pfOffsettedTsc, uint64_t *poffRealTSC)
{
    PVM         pVM = pVCpu->CTX_SUFF(pVM);
    uint64_t    cTicksToDeadline;

    /*
     * 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.fMaybeUseOffsettedHostTSC
        &&  RT_LIKELY(pVCpu->tm.s.fTSCTicking)
        &&  (   pVM->tm.s.fTSCUseRealTSC
             || (   !pVM->tm.s.fVirtualSyncCatchUp
                 && RT_LIKELY(pVM->tm.s.fVirtualSyncTicking)
                 && !pVM->tm.s.fVirtualWarpDrive))
       )
    {
        *pfOffsettedTsc = true;
        if (!pVM->tm.s.fTSCUseRealTSC)
        {
            /* The source is the timer synchronous virtual clock. */
            Assert(pVM->tm.s.fTSCVirtualized);

            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();
            cTicksToDeadline = tmCpuCalcTicksToDeadline(cNsToDeadline);
        }
        else
        {
            /* The source is the real TSC. */
            if (pVM->tm.s.fTSCVirtualized)
                *poffRealTSC = pVCpu->tm.s.offTSCRawSrc;
            else
                *poffRealTSC = 0;
            cTicksToDeadline = tmCpuCalcTicksToDeadline(TMVirtualSyncGetNsToDeadline(pVM));
        }
    }
    else
    {
#ifdef VBOX_WITH_STATISTICS
        tmCpuTickRecordOffsettedTscRefusal(pVM, pVCpu);
#endif
        *pfOffsettedTsc  = false;
        *poffRealTSC     = 0;
        cTicksToDeadline = tmCpuCalcTicksToDeadline(TMVirtualSyncGetNsToDeadline(pVM));
    }
    return cTicksToDeadline;
}


/**
 * Read the current CPU timestamp counter.
 *
 * @returns Gets the CPU tsc.
 * @param   pVCpu       Pointer to the VMCPU.
 */
DECLINLINE(uint64_t) tmCpuTickGetInternal(PVMCPU pVCpu, bool fCheckTimers)
{
    uint64_t u64;

    if (RT_LIKELY(pVCpu->tm.s.fTSCTicking))
    {
        PVM pVM = pVCpu->CTX_SUFF(pVM);
        if (pVM->tm.s.fTSCVirtualized)
        {
            if (pVM->tm.s.fTSCUseRealTSC)
                u64 = ASMReadTSC();
            else
                u64 = tmCpuTickGetRawVirtual(pVM, fCheckTimers);
            u64 -= pVCpu->tm.s.offTSCRawSrc;
        }
        else
            u64 = ASMReadTSC();

        /* Never return a value lower than what the guest has already seen. */
        if (u64 < pVCpu->tm.s.u64TSCLastSeen)
        {
            STAM_COUNTER_INC(&pVM->tm.s.StatTSCUnderflow);
            pVCpu->tm.s.u64TSCLastSeen += 64;   /* @todo choose a good increment here */
            u64 = pVCpu->tm.s.u64TSCLastSeen;
        }
    }
    else
        u64 = pVCpu->tm.s.u64TSC;
    return u64;
}


/**
 * Read the current CPU timestamp counter.
 *
 * @returns Gets the CPU tsc.
 * @param   pVCpu       Pointer to the VMCPU.
 */
VMMDECL(uint64_t) TMCpuTickGet(PVMCPU pVCpu)
{
    return tmCpuTickGetInternal(pVCpu, true /* fCheckTimers */);
}


/**
 * Read the current CPU timestamp counter, don't check for expired timers.
 *
 * @returns Gets the CPU tsc.
 * @param   pVCpu       Pointer to the VMCPU.
 */
VMM_INT_DECL(uint64_t) TMCpuTickGetNoCheck(PVMCPU pVCpu)
{
    return tmCpuTickGetInternal(pVCpu, false /* fCheckTimers */);
}


/**
 * Sets the current CPU timestamp counter.
 *
 * @returns VBox status code.
 * @param   pVM         Pointer to the VM.
 * @param   pVCpu       Pointer to the VMCPU.
 * @param   u64Tick     The new timestamp value.
 *
 * @thread  EMT which TSC is to be set.
 */
VMM_INT_DECL(int) TMCpuTickSet(PVM pVM, PVMCPU pVCpu, uint64_t u64Tick)
{
    VMCPU_ASSERT_EMT(pVCpu);
    STAM_COUNTER_INC(&pVM->tm.s.StatTSCSet);

    /*
     * This is easier to do when the TSC is paused since resume will
     * do all the calculations for us. Actually, we don't need to
     * call tmCpuTickPause here since we overwrite u64TSC anyway.
     */
    bool        fTSCTicking    = pVCpu->tm.s.fTSCTicking;
    pVCpu->tm.s.fTSCTicking    = false;
    pVCpu->tm.s.u64TSC         = u64Tick;
    pVCpu->tm.s.u64TSCLastSeen = u64Tick;
    if (fTSCTicking)
        tmCpuTickResume(pVM, pVCpu);
    /** @todo Try help synchronizing it better among the virtual CPUs? */

    return VINF_SUCCESS;
}

/**
 * Sets the last seen CPU timestamp counter.
 *
 * @returns VBox status code.
 * @param   pVCpu               Pointer to the VMCPU.
 * @param   u64LastSeenTick     The last seen timestamp value.
 *
 * @thread  EMT which TSC is to be set.
 */
VMM_INT_DECL(int) TMCpuTickSetLastSeen(PVMCPU pVCpu, uint64_t u64LastSeenTick)
{
    VMCPU_ASSERT_EMT(pVCpu);

    LogFlow(("TMCpuTickSetLastSeen %RX64\n", u64LastSeenTick));
    if (pVCpu->tm.s.u64TSCLastSeen < u64LastSeenTick)
        pVCpu->tm.s.u64TSCLastSeen = u64LastSeenTick;
    return VINF_SUCCESS;
}

/**
 * Gets the last seen CPU timestamp counter.
 *
 * @returns last seen TSC
 * @param   pVCpu               Pointer to the VMCPU.
 *
 * @thread  EMT which TSC is to be set.
 */
VMM_INT_DECL(uint64_t) TMCpuTickGetLastSeen(PVMCPU pVCpu)
{
    VMCPU_ASSERT_EMT(pVCpu);

    return pVCpu->tm.s.u64TSCLastSeen;
}


/**
 * Get the timestamp frequency.
 *
 * @returns Number of ticks per second.
 * @param   pVM     The VM.
 */
VMMDECL(uint64_t) TMCpuTicksPerSecond(PVM pVM)
{
    if (pVM->tm.s.fTSCUseRealTSC)
    {
        uint64_t cTSCTicksPerSecond = SUPGetCpuHzFromGIP(g_pSUPGlobalInfoPage);
        if (RT_LIKELY(cTSCTicksPerSecond != ~(uint64_t)0))
            return cTSCTicksPerSecond;
    }
    return pVM->tm.s.cTSCTicksPerSecond;
}