source: vbox/trunk/src/VBox/VMM/TM.cpp@ 34326

/* $Id: TM.cpp 34326 2010-11-24 14:03:55Z vboxsync $ */
/** @file
 * TM - Time Manager.
 */

/*
 * 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.
 */

/** @page pg_tm        TM - The Time Manager
 *
 * The Time Manager abstracts the CPU clocks and manages timers used by the VMM,
 * device and drivers.
 *
 * @see grp_tm
 *
 *
 * @section sec_tm_clocks   Clocks
 *
 * There are currently 4 clocks:
 *   - Virtual (guest).
 *   - Synchronous virtual (guest).
 *   - CPU Tick (TSC) (guest).  Only current use is rdtsc emulation. Usually a
 *     function of the virtual clock.
 *   - Real (host).  This is only used for display updates atm.
 *
 * The most important clocks are the three first ones and of these the second is
 * the most interesting.
 *
 *
 * The synchronous virtual clock is tied to the virtual clock except that it
 * will take into account timer delivery lag caused by host scheduling.  It will
 * normally never advance beyond the head timer, and when lagging too far behind
 * it will gradually speed up to catch up with the virtual clock.  All devices
 * implementing time sources accessible to and used by the guest is using this
 * clock (for timers and other things).  This ensures consistency between the
 * time sources.
 *
 * The virtual clock is implemented as an offset to a monotonic, high
 * resolution, wall clock.  The current time source is using the RTTimeNanoTS()
 * machinery based upon the Global Info Pages (GIP), that is, we're using TSC
 * deltas (usually 10 ms) to fill the gaps between GIP updates.  The result is
 * a fairly high res clock that works in all contexts and on all hosts.  The
 * virtual clock is paused when the VM isn't in the running state.
 *
 * The CPU tick (TSC) is normally virtualized as a function of the synchronous
 * virtual clock, where the frequency defaults to the host cpu frequency (as we
 * measure it). In this mode it is possible to configure the frequency. Another
 * (non-default) option is to use the raw unmodified host TSC values. And yet
 * another, to tie it to time spent executing guest code.  All these things are
 * configurable should non-default behavior be desirable.
 *
 * The real clock is a monotonic clock (when available) with relatively low
 * resolution, though this a bit host specific.  Note that we're currently not
 * servicing timers using the real clock when the VM is not running, this is
 * simply because it has not been needed yet therefore not implemented.
 *
 *
 * @subsection subsec_tm_timesync Guest Time Sync / UTC time
 *
 * Guest time syncing is primarily taken care of by the VMM device.  The
 * principle is very simple, the guest additions periodically asks the VMM
 * device what the current UTC time is and makes adjustments accordingly.
 *
 * A complicating factor is that the synchronous virtual clock might be doing
 * catchups and the guest perception is currently a little bit behind the world
 * but it will (hopefully) be catching up soon as we're feeding timer interrupts
 * at a slightly higher rate.  Adjusting the guest clock to the current wall
 * time in the real world would be a bad idea then because the guest will be
 * advancing too fast and run ahead of world time (if the catchup works out).
 * To solve this problem TM provides the VMM device with an UTC time source that
 * gets adjusted with the current lag, so that when the guest eventually catches
 * up the lag it will be showing correct real world time.
 *
 *
 * @section sec_tm_timers   Timers
 *
 * The timers can use any of the TM clocks described in the previous section.
 * Each clock has its own scheduling facility, or timer queue if you like.
 * There are a few factors which makes it a bit complex.  First, there is the
 * usual R0 vs R3 vs. RC thing.  Then there are multiple threads, and then there
 * is the timer thread that periodically checks whether any timers has expired
 * without EMT noticing.  On the API level, all but the create and save APIs
 * must be multithreaded.  EMT will always run the timers.
 *
 * The design is using a doubly linked list of active timers which is ordered
 * by expire date.  This list is only modified by the EMT thread.  Updates to
 * the list are batched in a singly linked list, which is then processed by the
 * EMT thread at the first opportunity (immediately, next time EMT modifies a
 * timer on that clock, or next timer timeout).  Both lists are offset based and
 * all the elements are therefore allocated from the hyper heap.
 *
 * For figuring out when there is need to schedule and run timers TM will:
 *    - Poll whenever somebody queries the virtual clock.
 *    - Poll the virtual clocks from the EM and REM loops.
 *    - Poll the virtual clocks from trap exit path.
 *    - Poll the virtual clocks and calculate first timeout from the halt loop.
 *    - Employ a thread which periodically (100Hz) polls all the timer queues.
 *
 *
 * @image html TMTIMER-Statechart-Diagram.gif
 *
 * @section sec_tm_timer    Logging
 *
 * Level 2: Logs a most of the timer state transitions and queue servicing.
 * Level 3: Logs a few oddments.
 * Level 4: Logs TMCLOCK_VIRTUAL_SYNC catch-up events.
 *
 */

/*******************************************************************************
*   Header Files                                                               *
*******************************************************************************/
#define LOG_GROUP LOG_GROUP_TM
#include <VBox/tm.h>
#include <VBox/vmm.h>
#include <VBox/mm.h>
#include <VBox/ssm.h>
#include <VBox/dbgf.h>
#include <VBox/rem.h>
#include <VBox/pdmapi.h>
#include <VBox/iom.h>
#include "TMInternal.h"
#include <VBox/vm.h>

#include <VBox/pdmdev.h>
#include <VBox/param.h>
#include <VBox/err.h>

#include <VBox/log.h>
#include <iprt/asm.h>
#include <iprt/asm-math.h>
#include <iprt/asm-amd64-x86.h>
#include <iprt/assert.h>
#include <iprt/thread.h>
#include <iprt/time.h>
#include <iprt/timer.h>
#include <iprt/semaphore.h>
#include <iprt/string.h>
#include <iprt/env.h>


/*******************************************************************************
*   Defined Constants And Macros                                               *
*******************************************************************************/
/** The current saved state version.*/
#define TM_SAVED_STATE_VERSION  3


/*******************************************************************************
*   Internal Functions                                                         *
*******************************************************************************/
static bool                 tmR3HasFixedTSC(PVM pVM);
static uint64_t             tmR3CalibrateTSC(PVM pVM);
static DECLCALLBACK(int)    tmR3Save(PVM pVM, PSSMHANDLE pSSM);
static DECLCALLBACK(int)    tmR3Load(PVM pVM, PSSMHANDLE pSSM, uint32_t uVersion, uint32_t uPass);
static DECLCALLBACK(void)   tmR3TimerCallback(PRTTIMER pTimer, void *pvUser, uint64_t iTick);
static void                 tmR3TimerQueueRun(PVM pVM, PTMTIMERQUEUE pQueue);
static void                 tmR3TimerQueueRunVirtualSync(PVM pVM);
static DECLCALLBACK(int)    tmR3SetWarpDrive(PVM pVM, uint32_t u32Percent);
#ifndef VBOX_WITHOUT_NS_ACCOUNTING
static DECLCALLBACK(void)   tmR3CpuLoadTimer(PVM pVM, PTMTIMER pTimer, void *pvUser);
#endif
static DECLCALLBACK(void)   tmR3TimerInfo(PVM pVM, PCDBGFINFOHLP pHlp, const char *pszArgs);
static DECLCALLBACK(void)   tmR3TimerInfoActive(PVM pVM, PCDBGFINFOHLP pHlp, const char *pszArgs);
static DECLCALLBACK(void)   tmR3InfoClocks(PVM pVM, PCDBGFINFOHLP pHlp, const char *pszArgs);


/**
 * Initializes the TM.
 *
 * @returns VBox status code.
 * @param   pVM         The VM to operate on.
 */
VMM_INT_DECL(int) TMR3Init(PVM pVM)
{
    LogFlow(("TMR3Init:\n"));

    /*
     * Assert alignment and sizes.
     */
    AssertCompileMemberAlignment(VM, tm.s, 32);
    AssertCompile(sizeof(pVM->tm.s) <= sizeof(pVM->tm.padding));
    AssertCompileMemberAlignment(TM, TimerCritSect, 8);
    AssertCompileMemberAlignment(TM, VirtualSyncLock, 8);

    /*
     * Init the structure.
     */
    void *pv;
    int rc = MMHyperAlloc(pVM, sizeof(pVM->tm.s.paTimerQueuesR3[0]) * TMCLOCK_MAX, 0, MM_TAG_TM, &pv);
    AssertRCReturn(rc, rc);
    pVM->tm.s.paTimerQueuesR3 = (PTMTIMERQUEUE)pv;
    pVM->tm.s.paTimerQueuesR0 = MMHyperR3ToR0(pVM, pv);
    pVM->tm.s.paTimerQueuesRC = MMHyperR3ToRC(pVM, pv);

    pVM->tm.s.offVM = RT_OFFSETOF(VM, tm.s);
    pVM->tm.s.idTimerCpu = pVM->cCpus - 1; /* The last CPU. */
    pVM->tm.s.paTimerQueuesR3[TMCLOCK_VIRTUAL].enmClock        = TMCLOCK_VIRTUAL;
    pVM->tm.s.paTimerQueuesR3[TMCLOCK_VIRTUAL].u64Expire       = INT64_MAX;
    pVM->tm.s.paTimerQueuesR3[TMCLOCK_VIRTUAL_SYNC].enmClock   = TMCLOCK_VIRTUAL_SYNC;
    pVM->tm.s.paTimerQueuesR3[TMCLOCK_VIRTUAL_SYNC].u64Expire  = INT64_MAX;
    pVM->tm.s.paTimerQueuesR3[TMCLOCK_REAL].enmClock           = TMCLOCK_REAL;
    pVM->tm.s.paTimerQueuesR3[TMCLOCK_REAL].u64Expire          = INT64_MAX;
    pVM->tm.s.paTimerQueuesR3[TMCLOCK_TSC].enmClock            = TMCLOCK_TSC;
    pVM->tm.s.paTimerQueuesR3[TMCLOCK_TSC].u64Expire           = INT64_MAX;


    /*
     * We directly use the GIP to calculate the virtual time. We map the
     * the GIP into the guest context so we can do this calculation there
     * as well and save costly world switches.
     */
    pVM->tm.s.pvGIPR3 = (void *)g_pSUPGlobalInfoPage;
    AssertMsgReturn(pVM->tm.s.pvGIPR3, ("GIP support is now required!\n"), VERR_INTERNAL_ERROR);
    RTHCPHYS HCPhysGIP;
    rc = SUPR3GipGetPhys(&HCPhysGIP);
    AssertMsgRCReturn(rc, ("Failed to get GIP physical address!\n"), rc);

    RTGCPTR GCPtr;
    rc = MMR3HyperMapHCPhys(pVM, pVM->tm.s.pvGIPR3, NIL_RTR0PTR, HCPhysGIP, PAGE_SIZE, "GIP", &GCPtr);
    if (RT_FAILURE(rc))
    {
        AssertMsgFailed(("Failed to map GIP into GC, rc=%Rrc!\n", rc));
        return rc;
    }
    pVM->tm.s.pvGIPRC = GCPtr;
    LogFlow(("TMR3Init: HCPhysGIP=%RHp at %RRv\n", HCPhysGIP, pVM->tm.s.pvGIPRC));
    MMR3HyperReserve(pVM, PAGE_SIZE, "fence", NULL);

    /* Check assumptions made in TMAllVirtual.cpp about the GIP update interval. */
    if (    g_pSUPGlobalInfoPage->u32Magic == SUPGLOBALINFOPAGE_MAGIC
        &&  g_pSUPGlobalInfoPage->u32UpdateIntervalNS >= 250000000 /* 0.25s */)
        return VMSetError(pVM, VERR_INTERNAL_ERROR, RT_SRC_POS,
                          N_("The GIP update interval is too big. u32UpdateIntervalNS=%RU32 (u32UpdateHz=%RU32)"),
                          g_pSUPGlobalInfoPage->u32UpdateIntervalNS, g_pSUPGlobalInfoPage->u32UpdateHz);
    LogRel(("TM: GIP - u32Mode=%d (%s) u32UpdateHz=%u\n", g_pSUPGlobalInfoPage->u32Mode,
            g_pSUPGlobalInfoPage->u32Mode == SUPGIPMODE_SYNC_TSC ? "SyncTSC"
            : g_pSUPGlobalInfoPage->u32Mode == SUPGIPMODE_ASYNC_TSC ? "AsyncTSC" : "Unknown",
            g_pSUPGlobalInfoPage->u32UpdateHz));

    /*
     * Setup the VirtualGetRaw backend.
     */
    pVM->tm.s.VirtualGetRawDataR3.pu64Prev = &pVM->tm.s.u64VirtualRawPrev;
    pVM->tm.s.VirtualGetRawDataR3.pfnBad = tmVirtualNanoTSBad;
    pVM->tm.s.VirtualGetRawDataR3.pfnRediscover = tmVirtualNanoTSRediscover;
    if (ASMCpuId_EDX(1) & X86_CPUID_FEATURE_EDX_SSE2)
    {
        if (g_pSUPGlobalInfoPage->u32Mode == SUPGIPMODE_SYNC_TSC)
            pVM->tm.s.pfnVirtualGetRawR3 = RTTimeNanoTSLFenceSync;
        else
            pVM->tm.s.pfnVirtualGetRawR3 = RTTimeNanoTSLFenceAsync;
    }
    else
    {
        if (g_pSUPGlobalInfoPage->u32Mode == SUPGIPMODE_SYNC_TSC)
            pVM->tm.s.pfnVirtualGetRawR3 = RTTimeNanoTSLegacySync;
        else
            pVM->tm.s.pfnVirtualGetRawR3 = RTTimeNanoTSLegacyAsync;
    }

    pVM->tm.s.VirtualGetRawDataRC.pu64Prev = MMHyperR3ToRC(pVM, (void *)&pVM->tm.s.u64VirtualRawPrev);
    pVM->tm.s.VirtualGetRawDataR0.pu64Prev = MMHyperR3ToR0(pVM, (void *)&pVM->tm.s.u64VirtualRawPrev);
    AssertReturn(pVM->tm.s.VirtualGetRawDataR0.pu64Prev, VERR_INTERNAL_ERROR);
    /* The rest is done in TMR3InitFinalize since it's too early to call PDM. */

    /*
     * Init the locks.
     */
    rc = PDMR3CritSectInit(pVM, &pVM->tm.s.TimerCritSect, RT_SRC_POS, "TM Timer Lock");
    if (RT_FAILURE(rc))
        return rc;
    rc = PDMR3CritSectInit(pVM, &pVM->tm.s.VirtualSyncLock, RT_SRC_POS, "TM VirtualSync Lock");
    if (RT_FAILURE(rc))
        return rc;

    /*
     * Get our CFGM node, create it if necessary.
     */
    PCFGMNODE pCfgHandle = CFGMR3GetChild(CFGMR3GetRoot(pVM), "TM");
    if (!pCfgHandle)
    {
        rc = CFGMR3InsertNode(CFGMR3GetRoot(pVM), "TM", &pCfgHandle);
        AssertRCReturn(rc, rc);
    }

    /*
     * Determine the TSC configuration and frequency.
     */
    /* mode */
    /** @cfgm{/TM/TSCVirtualized,bool,true}
     * Use a virtualize TSC, i.e. trap all TSC access. */
    rc = CFGMR3QueryBool(pCfgHandle, "TSCVirtualized", &pVM->tm.s.fTSCVirtualized);
    if (rc == VERR_CFGM_VALUE_NOT_FOUND)
        pVM->tm.s.fTSCVirtualized = true; /* trap rdtsc */
    else if (RT_FAILURE(rc))
        return VMSetError(pVM, rc, RT_SRC_POS,
                          N_("Configuration error: Failed to querying bool value \"UseRealTSC\""));

    /* source */
    /** @cfgm{/TM/UseRealTSC,bool,false}
     * Use the real TSC as time source for the TSC instead of the synchronous
     * virtual clock (false, default). */
    rc = CFGMR3QueryBool(pCfgHandle, "UseRealTSC", &pVM->tm.s.fTSCUseRealTSC);
    if (rc == VERR_CFGM_VALUE_NOT_FOUND)
        pVM->tm.s.fTSCUseRealTSC = false; /* use virtual time */
    else if (RT_FAILURE(rc))
        return VMSetError(pVM, rc, RT_SRC_POS,
                          N_("Configuration error: Failed to querying bool value \"UseRealTSC\""));
    if (!pVM->tm.s.fTSCUseRealTSC)
        pVM->tm.s.fTSCVirtualized = true;

    /* TSC reliability */
    /** @cfgm{/TM/MaybeUseOffsettedHostTSC,bool,detect}
     * Whether the CPU has a fixed TSC rate and may be used in offsetted mode with
     * VT-x/AMD-V execution.  This is autodetected in a very restrictive way by
     * default. */
    rc = CFGMR3QueryBool(pCfgHandle, "MaybeUseOffsettedHostTSC", &pVM->tm.s.fMaybeUseOffsettedHostTSC);
    if (rc == VERR_CFGM_VALUE_NOT_FOUND)
    {
        if (!pVM->tm.s.fTSCUseRealTSC)
            pVM->tm.s.fMaybeUseOffsettedHostTSC = tmR3HasFixedTSC(pVM);
        else
            pVM->tm.s.fMaybeUseOffsettedHostTSC = true;
    }

    /** @cfgm{TM/TSCTicksPerSecond, uint32_t, Current TSC frequency from GIP}
     * The number of TSC ticks per second (i.e. the TSC frequency). This will
     * override TSCUseRealTSC, TSCVirtualized and MaybeUseOffsettedHostTSC.
     */
    rc = CFGMR3QueryU64(pCfgHandle, "TSCTicksPerSecond", &pVM->tm.s.cTSCTicksPerSecond);
    if (rc == VERR_CFGM_VALUE_NOT_FOUND)
    {
        pVM->tm.s.cTSCTicksPerSecond = tmR3CalibrateTSC(pVM);
        if (    !pVM->tm.s.fTSCUseRealTSC
            &&  pVM->tm.s.cTSCTicksPerSecond >= _4G)
        {
            pVM->tm.s.cTSCTicksPerSecond = _4G - 1; /* (A limitation of our math code) */
            pVM->tm.s.fMaybeUseOffsettedHostTSC = false;
        }
    }
    else if (RT_FAILURE(rc))
        return VMSetError(pVM, rc, RT_SRC_POS,
                          N_("Configuration error: Failed to querying uint64_t value \"TSCTicksPerSecond\""));
    else if (   pVM->tm.s.cTSCTicksPerSecond < _1M
             || pVM->tm.s.cTSCTicksPerSecond >= _4G)
        return VMSetError(pVM, VERR_INVALID_PARAMETER, RT_SRC_POS,
                          N_("Configuration error: \"TSCTicksPerSecond\" = %RI64 is not in the range 1MHz..4GHz-1"),
                          pVM->tm.s.cTSCTicksPerSecond);
    else
    {
        pVM->tm.s.fTSCUseRealTSC = pVM->tm.s.fMaybeUseOffsettedHostTSC = false;
        pVM->tm.s.fTSCVirtualized = true;
    }

    /** @cfgm{TM/TSCTiedToExecution, bool, false}
     * Whether the TSC should be tied to execution. This will exclude most of the
     * virtualization overhead, but will by default include the time spent in the
     * halt state (see TM/TSCNotTiedToHalt). This setting will override all other
     * TSC settings except for TSCTicksPerSecond and TSCNotTiedToHalt, which should
     * be used avoided or used with great care. Note that this will only work right
     * together with VT-x or AMD-V, and with a single virtual CPU. */
    rc = CFGMR3QueryBoolDef(pCfgHandle, "TSCTiedToExecution", &pVM->tm.s.fTSCTiedToExecution, false);
    if (RT_FAILURE(rc))
        return VMSetError(pVM, rc, RT_SRC_POS,
                          N_("Configuration error: Failed to querying bool value \"TSCTiedToExecution\""));
    if (pVM->tm.s.fTSCTiedToExecution)
    {
        /* tied to execution, override all other settings. */
        pVM->tm.s.fTSCVirtualized = true;
        pVM->tm.s.fTSCUseRealTSC = true;
        pVM->tm.s.fMaybeUseOffsettedHostTSC = false;
    }

    /** @cfgm{TM/TSCNotTiedToHalt, bool, true}
     * For overriding the default of TM/TSCTiedToExecution, i.e. set this to false
     * to make the TSC freeze during HLT. */
    rc = CFGMR3QueryBoolDef(pCfgHandle, "TSCNotTiedToHalt", &pVM->tm.s.fTSCNotTiedToHalt, false);
    if (RT_FAILURE(rc))
        return VMSetError(pVM, rc, RT_SRC_POS,
                          N_("Configuration error: Failed to querying bool value \"TSCNotTiedToHalt\""));

    /* setup and report */
    if (pVM->tm.s.fTSCVirtualized)
        CPUMR3SetCR4Feature(pVM, X86_CR4_TSD, ~X86_CR4_TSD);
    else
        CPUMR3SetCR4Feature(pVM, 0, ~X86_CR4_TSD);
    LogRel(("TM: cTSCTicksPerSecond=%#RX64 (%'RU64) fTSCVirtualized=%RTbool fTSCUseRealTSC=%RTbool\n"
            "TM: fMaybeUseOffsettedHostTSC=%RTbool TSCTiedToExecution=%RTbool TSCNotTiedToHalt=%RTbool\n",
            pVM->tm.s.cTSCTicksPerSecond, pVM->tm.s.cTSCTicksPerSecond, pVM->tm.s.fTSCVirtualized, pVM->tm.s.fTSCUseRealTSC,
            pVM->tm.s.fMaybeUseOffsettedHostTSC, pVM->tm.s.fTSCTiedToExecution, pVM->tm.s.fTSCNotTiedToHalt));

    /*
     * Configure the timer synchronous virtual time.
     */
    /** @cfgm{TM/ScheduleSlack, uint32_t, ns, 0, UINT32_MAX, 100000}
     * Scheduling slack when processing timers. */
    rc = CFGMR3QueryU32(pCfgHandle, "ScheduleSlack", &pVM->tm.s.u32VirtualSyncScheduleSlack);
    if (rc == VERR_CFGM_VALUE_NOT_FOUND)
        pVM->tm.s.u32VirtualSyncScheduleSlack           =   100000; /* 0.100ms (ASSUMES virtual time is nanoseconds) */
    else if (RT_FAILURE(rc))
        return VMSetError(pVM, rc, RT_SRC_POS,
                          N_("Configuration error: Failed to querying 32-bit integer value \"ScheduleSlack\""));

    /** @cfgm{TM/CatchUpStopThreshold, uint64_t, ns, 0, UINT64_MAX, 500000}
     * When to stop a catch-up, considering it successful. */
    rc = CFGMR3QueryU64(pCfgHandle, "CatchUpStopThreshold", &pVM->tm.s.u64VirtualSyncCatchUpStopThreshold);
    if (rc == VERR_CFGM_VALUE_NOT_FOUND)
        pVM->tm.s.u64VirtualSyncCatchUpStopThreshold    =   500000; /* 0.5ms */
    else if (RT_FAILURE(rc))
        return VMSetError(pVM, rc, RT_SRC_POS,
                          N_("Configuration error: Failed to querying 64-bit integer value \"CatchUpStopThreshold\""));

    /** @cfgm{TM/CatchUpGiveUpThreshold, uint64_t, ns, 0, UINT64_MAX, 60000000000}
     * When to give up a catch-up attempt. */
    rc = CFGMR3QueryU64(pCfgHandle, "CatchUpGiveUpThreshold", &pVM->tm.s.u64VirtualSyncCatchUpGiveUpThreshold);
    if (rc == VERR_CFGM_VALUE_NOT_FOUND)
        pVM->tm.s.u64VirtualSyncCatchUpGiveUpThreshold  = UINT64_C(60000000000); /* 60 sec */
    else if (RT_FAILURE(rc))
        return VMSetError(pVM, rc, RT_SRC_POS,
                          N_("Configuration error: Failed to querying 64-bit integer value \"CatchUpGiveUpThreshold\""));


    /** @cfgm{TM/CatchUpPrecentage[0..9], uint32_t, %, 1, 2000, various}
     * The catch-up percent for a given period.  */
    /** @cfgm{TM/CatchUpStartThreshold[0..9], uint64_t, ns, 0, UINT64_MAX,
     * The catch-up period threshold, or if you like, when a period starts.  */
#define TM_CFG_PERIOD(iPeriod, DefStart, DefPct) \
    do \
    { \
        uint64_t u64; \
        rc = CFGMR3QueryU64(pCfgHandle, "CatchUpStartThreshold" #iPeriod, &u64); \
        if (rc == VERR_CFGM_VALUE_NOT_FOUND) \
            u64 = UINT64_C(DefStart); \
        else if (RT_FAILURE(rc)) \
            return VMSetError(pVM, rc, RT_SRC_POS, N_("Configuration error: Failed to querying 64-bit integer value \"CatchUpThreshold" #iPeriod "\"")); \
        if (    (iPeriod > 0 && u64 <= pVM->tm.s.aVirtualSyncCatchUpPeriods[iPeriod - 1].u64Start) \
            ||  u64 >= pVM->tm.s.u64VirtualSyncCatchUpGiveUpThreshold) \
            return VMSetError(pVM, VERR_INVALID_PARAMETER, RT_SRC_POS, N_("Configuration error: Invalid start of period #" #iPeriod ": %'RU64"), u64); \
        pVM->tm.s.aVirtualSyncCatchUpPeriods[iPeriod].u64Start = u64; \
        rc = CFGMR3QueryU32(pCfgHandle, "CatchUpPrecentage" #iPeriod, &pVM->tm.s.aVirtualSyncCatchUpPeriods[iPeriod].u32Percentage); \
        if (rc == VERR_CFGM_VALUE_NOT_FOUND) \
            pVM->tm.s.aVirtualSyncCatchUpPeriods[iPeriod].u32Percentage = (DefPct); \
        else if (RT_FAILURE(rc)) \
            return VMSetError(pVM, rc, RT_SRC_POS, N_("Configuration error: Failed to querying 32-bit integer value \"CatchUpPrecentage" #iPeriod "\"")); \
    } while (0)
    /* This needs more tuning. Not sure if we really need so many period and be so gentle. */
    TM_CFG_PERIOD(0,     750000,   5); /* 0.75ms at 1.05x */
    TM_CFG_PERIOD(1,    1500000,  10); /* 1.50ms at 1.10x */
    TM_CFG_PERIOD(2,    8000000,  25); /*    8ms at 1.25x */
    TM_CFG_PERIOD(3,   30000000,  50); /*   30ms at 1.50x */
    TM_CFG_PERIOD(4,   75000000,  75); /*   75ms at 1.75x */
    TM_CFG_PERIOD(5,  175000000, 100); /*  175ms at 2x */
    TM_CFG_PERIOD(6,  500000000, 200); /*  500ms at 3x */
    TM_CFG_PERIOD(7, 3000000000, 300); /*    3s  at 4x */
    TM_CFG_PERIOD(8,30000000000, 400); /*   30s  at 5x */
    TM_CFG_PERIOD(9,55000000000, 500); /*   55s  at 6x */
    AssertCompile(RT_ELEMENTS(pVM->tm.s.aVirtualSyncCatchUpPeriods) == 10);
#undef TM_CFG_PERIOD

    /*
     * Configure real world time (UTC).
     */
    /** @cfgm{TM/UTCOffset, int64_t, ns, INT64_MIN, INT64_MAX, 0}
     * The UTC offset. This is used to put the guest back or forwards in time.  */
    rc = CFGMR3QueryS64(pCfgHandle, "UTCOffset", &pVM->tm.s.offUTC);
    if (rc == VERR_CFGM_VALUE_NOT_FOUND)
        pVM->tm.s.offUTC = 0; /* ns */
    else if (RT_FAILURE(rc))
        return VMSetError(pVM, rc, RT_SRC_POS,
                          N_("Configuration error: Failed to querying 64-bit integer value \"UTCOffset\""));

    /*
     * Setup the warp drive.
     */
    /** @cfgm{TM/WarpDrivePercentage, uint32_t, %, 0, 20000, 100}
     * The warp drive percentage, 100% is normal speed.  This is used to speed up
     * or slow down the virtual clock, which can be useful for fast forwarding
     * borring periods during tests. */
    rc = CFGMR3QueryU32(pCfgHandle, "WarpDrivePercentage", &pVM->tm.s.u32VirtualWarpDrivePercentage);
    if (rc == VERR_CFGM_VALUE_NOT_FOUND)
        rc = CFGMR3QueryU32(CFGMR3GetRoot(pVM), "WarpDrivePercentage", &pVM->tm.s.u32VirtualWarpDrivePercentage); /* legacy */
    if (rc == VERR_CFGM_VALUE_NOT_FOUND)
        pVM->tm.s.u32VirtualWarpDrivePercentage = 100;
    else if (RT_FAILURE(rc))
        return VMSetError(pVM, rc, RT_SRC_POS,
                          N_("Configuration error: Failed to querying uint32_t value \"WarpDrivePercent\""));
    else if (   pVM->tm.s.u32VirtualWarpDrivePercentage < 2
             || pVM->tm.s.u32VirtualWarpDrivePercentage > 20000)
        return VMSetError(pVM, VERR_INVALID_PARAMETER, RT_SRC_POS,
                          N_("Configuration error: \"WarpDrivePercent\" = %RI32 is not in the range 2..20000"),
                          pVM->tm.s.u32VirtualWarpDrivePercentage);
    pVM->tm.s.fVirtualWarpDrive = pVM->tm.s.u32VirtualWarpDrivePercentage != 100;
    if (pVM->tm.s.fVirtualWarpDrive)
        LogRel(("TM: u32VirtualWarpDrivePercentage=%RI32\n", pVM->tm.s.u32VirtualWarpDrivePercentage));

    /*
     * Gather the Host Hz configuration values.
     */
    rc = CFGMR3QueryU32Def(pCfgHandle, "HostHzMax", &pVM->tm.s.cHostHzMax, 20000);
    if (RT_FAILURE(rc))
        return VMSetError(pVM, rc, RT_SRC_POS,
                          N_("Configuration error: Failed to querying uint32_t value \"HostHzMax\""));

    rc = CFGMR3QueryU32Def(pCfgHandle, "HostHzFudgeFactorTimerCpu", &pVM->tm.s.cPctHostHzFudgeFactorTimerCpu, 111);
    if (RT_FAILURE(rc))
        return VMSetError(pVM, rc, RT_SRC_POS,
                          N_("Configuration error: Failed to querying uint32_t value \"HostHzFudgeFactorTimerCpu\""));

    rc = CFGMR3QueryU32Def(pCfgHandle, "HostHzFudgeFactorOtherCpu", &pVM->tm.s.cPctHostHzFudgeFactorOtherCpu, 110);
    if (RT_FAILURE(rc))
        return VMSetError(pVM, rc, RT_SRC_POS,
                          N_("Configuration error: Failed to querying uint32_t value \"HostHzFudgeFactorOtherCpu\""));

    rc = CFGMR3QueryU32Def(pCfgHandle, "HostHzFudgeFactorCatchUp100", &pVM->tm.s.cPctHostHzFudgeFactorCatchUp100, 300);
    if (RT_FAILURE(rc))
        return VMSetError(pVM, rc, RT_SRC_POS,
                          N_("Configuration error: Failed to querying uint32_t value \"HostHzFudgeFactorCatchUp100\""));

    rc = CFGMR3QueryU32Def(pCfgHandle, "HostHzFudgeFactorCatchUp200", &pVM->tm.s.cPctHostHzFudgeFactorCatchUp200, 250);
    if (RT_FAILURE(rc))
        return VMSetError(pVM, rc, RT_SRC_POS,
                          N_("Configuration error: Failed to querying uint32_t value \"HostHzFudgeFactorCatchUp200\""));

    rc = CFGMR3QueryU32Def(pCfgHandle, "HostHzFudgeFactorCatchUp400", &pVM->tm.s.cPctHostHzFudgeFactorCatchUp400, 200);
    if (RT_FAILURE(rc))
        return VMSetError(pVM, rc, RT_SRC_POS,
                          N_("Configuration error: Failed to querying uint32_t value \"HostHzFudgeFactorCatchUp400\""));

    /*
     * Start the timer (guard against REM not yielding).
     */
    /** @cfgm{TM/TimerMillies, uint32_t, ms, 1, 1000, 10}
     * The watchdog timer interval.  */
    uint32_t u32Millies;
    rc = CFGMR3QueryU32(pCfgHandle, "TimerMillies", &u32Millies);
    if (rc == VERR_CFGM_VALUE_NOT_FOUND)
        u32Millies = 10;
    else if (RT_FAILURE(rc))
        return VMSetError(pVM, rc, RT_SRC_POS,
                          N_("Configuration error: Failed to query uint32_t value \"TimerMillies\""));
    rc = RTTimerCreate(&pVM->tm.s.pTimer, u32Millies, tmR3TimerCallback, pVM);
    if (RT_FAILURE(rc))
    {
        AssertMsgFailed(("Failed to create timer, u32Millies=%d rc=%Rrc.\n", u32Millies, rc));
        return rc;
    }
    Log(("TM: Created timer %p firing every %d milliseconds\n", pVM->tm.s.pTimer, u32Millies));
    pVM->tm.s.u32TimerMillies = u32Millies;

    /*
     * Register saved state.
     */
    rc = SSMR3RegisterInternal(pVM, "tm", 1, TM_SAVED_STATE_VERSION, sizeof(uint64_t) * 8,
                               NULL, NULL, NULL,
                               NULL, tmR3Save, NULL,
                               NULL, tmR3Load, NULL);
    if (RT_FAILURE(rc))
        return rc;

    /*
     * Register statistics.
     */
    STAM_REL_REG_USED(pVM,(void*)&pVM->tm.s.VirtualGetRawDataR3.c1nsSteps,STAMTYPE_U32, "/TM/R3/1nsSteps",                     STAMUNIT_OCCURENCES, "Virtual time 1ns steps (due to TSC / GIP variations).");
    STAM_REL_REG_USED(pVM,(void*)&pVM->tm.s.VirtualGetRawDataR3.cBadPrev, STAMTYPE_U32, "/TM/R3/cBadPrev",                     STAMUNIT_OCCURENCES, "Times the previous virtual time was considered erratic (shouldn't ever happen).");
    STAM_REL_REG_USED(pVM,(void*)&pVM->tm.s.VirtualGetRawDataR0.c1nsSteps,STAMTYPE_U32, "/TM/R0/1nsSteps",                     STAMUNIT_OCCURENCES, "Virtual time 1ns steps (due to TSC / GIP variations).");
    STAM_REL_REG_USED(pVM,(void*)&pVM->tm.s.VirtualGetRawDataR0.cBadPrev, STAMTYPE_U32, "/TM/R0/cBadPrev",                     STAMUNIT_OCCURENCES, "Times the previous virtual time was considered erratic (shouldn't ever happen).");
    STAM_REL_REG_USED(pVM,(void*)&pVM->tm.s.VirtualGetRawDataRC.c1nsSteps,STAMTYPE_U32, "/TM/RC/1nsSteps",                     STAMUNIT_OCCURENCES, "Virtual time 1ns steps (due to TSC / GIP variations).");
    STAM_REL_REG_USED(pVM,(void*)&pVM->tm.s.VirtualGetRawDataRC.cBadPrev, STAMTYPE_U32, "/TM/RC/cBadPrev",                     STAMUNIT_OCCURENCES, "Times the previous virtual time was considered erratic (shouldn't ever happen).");
    STAM_REL_REG(     pVM,(void*)&pVM->tm.s.offVirtualSync,               STAMTYPE_U64, "/TM/VirtualSync/CurrentOffset",               STAMUNIT_NS, "The current offset. (subtract GivenUp to get the lag)");
    STAM_REL_REG_USED(pVM,(void*)&pVM->tm.s.offVirtualSyncGivenUp,        STAMTYPE_U64, "/TM/VirtualSync/GivenUp",                     STAMUNIT_NS, "Nanoseconds of the 'CurrentOffset' that's been given up and won't ever be attempted caught up with.");
    STAM_REL_REG(     pVM,(void*)&pVM->tm.s.uMaxHzHint,                   STAMTYPE_U32, "/TM/MaxHzHint",                               STAMUNIT_HZ, "Max guest timer frequency hint.");

#ifdef VBOX_WITH_STATISTICS
    STAM_REG_USED(pVM,(void *)&pVM->tm.s.VirtualGetRawDataR3.cExpired,    STAMTYPE_U32, "/TM/R3/cExpired",                     STAMUNIT_OCCURENCES, "Times the TSC interval expired (overlaps 1ns steps).");
    STAM_REG_USED(pVM,(void *)&pVM->tm.s.VirtualGetRawDataR3.cUpdateRaces,STAMTYPE_U32, "/TM/R3/cUpdateRaces",                 STAMUNIT_OCCURENCES, "Thread races when updating the previous timestamp.");
    STAM_REG_USED(pVM,(void *)&pVM->tm.s.VirtualGetRawDataR0.cExpired,    STAMTYPE_U32, "/TM/R0/cExpired",                     STAMUNIT_OCCURENCES, "Times the TSC interval expired (overlaps 1ns steps).");
    STAM_REG_USED(pVM,(void *)&pVM->tm.s.VirtualGetRawDataR0.cUpdateRaces,STAMTYPE_U32, "/TM/R0/cUpdateRaces",                 STAMUNIT_OCCURENCES, "Thread races when updating the previous timestamp.");
    STAM_REG_USED(pVM,(void *)&pVM->tm.s.VirtualGetRawDataRC.cExpired,    STAMTYPE_U32, "/TM/RC/cExpired",                     STAMUNIT_OCCURENCES, "Times the TSC interval expired (overlaps 1ns steps).");
    STAM_REG_USED(pVM,(void *)&pVM->tm.s.VirtualGetRawDataRC.cUpdateRaces,STAMTYPE_U32, "/TM/RC/cUpdateRaces",                 STAMUNIT_OCCURENCES, "Thread races when updating the previous timestamp.");
    STAM_REG(pVM, &pVM->tm.s.StatDoQueues,                            STAMTYPE_PROFILE, "/TM/DoQueues",                    STAMUNIT_TICKS_PER_CALL, "Profiling timer TMR3TimerQueuesDo.");
    STAM_REG(pVM, &pVM->tm.s.aStatDoQueues[TMCLOCK_VIRTUAL],      STAMTYPE_PROFILE_ADV, "/TM/DoQueues/Virtual",            STAMUNIT_TICKS_PER_CALL, "Time spent on the virtual clock queue.");
    STAM_REG(pVM, &pVM->tm.s.aStatDoQueues[TMCLOCK_VIRTUAL_SYNC], STAMTYPE_PROFILE_ADV, "/TM/DoQueues/VirtualSync",        STAMUNIT_TICKS_PER_CALL, "Time spent on the virtual sync clock queue.");
    STAM_REG(pVM, &pVM->tm.s.aStatDoQueues[TMCLOCK_REAL],         STAMTYPE_PROFILE_ADV, "/TM/DoQueues/Real",               STAMUNIT_TICKS_PER_CALL, "Time spent on the real clock queue.");

    STAM_REG(pVM, &pVM->tm.s.StatPoll,                                STAMTYPE_COUNTER, "/TM/Poll",                            STAMUNIT_OCCURENCES, "TMTimerPoll calls.");
    STAM_REG(pVM, &pVM->tm.s.StatPollAlreadySet,                      STAMTYPE_COUNTER, "/TM/Poll/AlreadySet",                 STAMUNIT_OCCURENCES, "TMTimerPoll calls where the FF was already set.");
    STAM_REG(pVM, &pVM->tm.s.StatPollELoop,                           STAMTYPE_COUNTER, "/TM/Poll/ELoop",                      STAMUNIT_OCCURENCES, "Times TMTimerPoll has given up getting a consistent virtual sync data set.");
    STAM_REG(pVM, &pVM->tm.s.StatPollMiss,                            STAMTYPE_COUNTER, "/TM/Poll/Miss",                       STAMUNIT_OCCURENCES, "TMTimerPoll calls where nothing had expired.");
    STAM_REG(pVM, &pVM->tm.s.StatPollRunning,                         STAMTYPE_COUNTER, "/TM/Poll/Running",                    STAMUNIT_OCCURENCES, "TMTimerPoll calls where the queues were being run.");
    STAM_REG(pVM, &pVM->tm.s.StatPollSimple,                          STAMTYPE_COUNTER, "/TM/Poll/Simple",                     STAMUNIT_OCCURENCES, "TMTimerPoll calls where we could take the simple path.");
    STAM_REG(pVM, &pVM->tm.s.StatPollVirtual,                         STAMTYPE_COUNTER, "/TM/Poll/HitsVirtual",                STAMUNIT_OCCURENCES, "The number of times TMTimerPoll found an expired TMCLOCK_VIRTUAL queue.");
    STAM_REG(pVM, &pVM->tm.s.StatPollVirtualSync,                     STAMTYPE_COUNTER, "/TM/Poll/HitsVirtualSync",            STAMUNIT_OCCURENCES, "The number of times TMTimerPoll found an expired TMCLOCK_VIRTUAL_SYNC queue.");

    STAM_REG(pVM, &pVM->tm.s.StatPostponedR3,                         STAMTYPE_COUNTER, "/TM/PostponedR3",                     STAMUNIT_OCCURENCES, "Postponed due to unschedulable state, in ring-3.");
    STAM_REG(pVM, &pVM->tm.s.StatPostponedRZ,                         STAMTYPE_COUNTER, "/TM/PostponedRZ",                     STAMUNIT_OCCURENCES, "Postponed due to unschedulable state, in ring-0 / RC.");

    STAM_REG(pVM, &pVM->tm.s.StatScheduleOneR3,                       STAMTYPE_PROFILE, "/TM/ScheduleOneR3",               STAMUNIT_TICKS_PER_CALL, "Profiling the scheduling of one queue during a TMTimer* call in EMT.");
    STAM_REG(pVM, &pVM->tm.s.StatScheduleOneRZ,                       STAMTYPE_PROFILE, "/TM/ScheduleOneRZ",               STAMUNIT_TICKS_PER_CALL, "Profiling the scheduling of one queue during a TMTimer* call in EMT.");
    STAM_REG(pVM, &pVM->tm.s.StatScheduleSetFF,                       STAMTYPE_COUNTER, "/TM/ScheduleSetFF",                   STAMUNIT_OCCURENCES, "The number of times the timer FF was set instead of doing scheduling.");

    STAM_REG(pVM, &pVM->tm.s.StatTimerSet,                            STAMTYPE_COUNTER, "/TM/TimerSet",                        STAMUNIT_OCCURENCES, "Calls");
    STAM_REG(pVM, &pVM->tm.s.StatTimerSetOpt,                         STAMTYPE_COUNTER, "/TM/TimerSet/Opt",                    STAMUNIT_OCCURENCES, "Optimized path taken.");
    STAM_REG(pVM, &pVM->tm.s.StatTimerSetR3,                          STAMTYPE_PROFILE, "/TM/TimerSet/R3",                 STAMUNIT_TICKS_PER_CALL, "Profiling TMTimerSet calls made in ring-3.");
    STAM_REG(pVM, &pVM->tm.s.StatTimerSetRZ,                          STAMTYPE_PROFILE, "/TM/TimerSet/RZ",                 STAMUNIT_TICKS_PER_CALL, "Profiling TMTimerSet calls made in ring-0 / RC.");
    STAM_REG(pVM, &pVM->tm.s.StatTimerSetStActive,                    STAMTYPE_COUNTER, "/TM/TimerSet/StActive",               STAMUNIT_OCCURENCES, "ACTIVE");
    STAM_REG(pVM, &pVM->tm.s.StatTimerSetStExpDeliver,                STAMTYPE_COUNTER, "/TM/TimerSet/StExpDeliver",           STAMUNIT_OCCURENCES, "EXPIRED_DELIVER");
    STAM_REG(pVM, &pVM->tm.s.StatTimerSetStOther,                     STAMTYPE_COUNTER, "/TM/TimerSet/StOther",                STAMUNIT_OCCURENCES, "Other states");
    STAM_REG(pVM, &pVM->tm.s.StatTimerSetStPendStop,                  STAMTYPE_COUNTER, "/TM/TimerSet/StPendStop",             STAMUNIT_OCCURENCES, "PENDING_STOP");
    STAM_REG(pVM, &pVM->tm.s.StatTimerSetStPendStopSched,             STAMTYPE_COUNTER, "/TM/TimerSet/StPendStopSched",        STAMUNIT_OCCURENCES, "PENDING_STOP_SCHEDULE");
    STAM_REG(pVM, &pVM->tm.s.StatTimerSetStPendSched,                 STAMTYPE_COUNTER, "/TM/TimerSet/StPendSched",            STAMUNIT_OCCURENCES, "PENDING_SCHEDULE");
    STAM_REG(pVM, &pVM->tm.s.StatTimerSetStPendResched,               STAMTYPE_COUNTER, "/TM/TimerSet/StPendResched",          STAMUNIT_OCCURENCES, "PENDING_RESCHEDULE");
    STAM_REG(pVM, &pVM->tm.s.StatTimerSetStStopped,                   STAMTYPE_COUNTER, "/TM/TimerSet/StStopped",              STAMUNIT_OCCURENCES, "STOPPED");

    STAM_REG(pVM, &pVM->tm.s.StatTimerSetRelative,                    STAMTYPE_COUNTER, "/TM/TimerSetRelative",                STAMUNIT_OCCURENCES, "Calls");
    STAM_REG(pVM, &pVM->tm.s.StatTimerSetRelativeOpt,                 STAMTYPE_COUNTER, "/TM/TimerSetRelative/Opt",            STAMUNIT_OCCURENCES, "Optimized path taken.");
    STAM_REG(pVM, &pVM->tm.s.StatTimerSetRelativeR3,                  STAMTYPE_PROFILE, "/TM/TimerSetRelative/R3",         STAMUNIT_TICKS_PER_CALL, "Profiling TMTimerSetRelative calls made in ring-3.");
    STAM_REG(pVM, &pVM->tm.s.StatTimerSetRelativeRZ,                  STAMTYPE_PROFILE, "/TM/TimerSetRelative/RZ",         STAMUNIT_TICKS_PER_CALL, "Profiling TMTimerSetReltaive calls made in ring-0 / RC.");
    STAM_REG(pVM, &pVM->tm.s.StatTimerSetRelativeRacyVirtSync,        STAMTYPE_COUNTER, "/TM/TimerSetRelative/RacyVirtSync",   STAMUNIT_OCCURENCES, "Potentially racy virtual sync timer update.");
    STAM_REG(pVM, &pVM->tm.s.StatTimerSetRelativeStActive,            STAMTYPE_COUNTER, "/TM/TimerSetRelative/StActive",       STAMUNIT_OCCURENCES, "ACTIVE");
    STAM_REG(pVM, &pVM->tm.s.StatTimerSetRelativeStExpDeliver,        STAMTYPE_COUNTER, "/TM/TimerSetRelative/StExpDeliver",   STAMUNIT_OCCURENCES, "EXPIRED_DELIVER");
    STAM_REG(pVM, &pVM->tm.s.StatTimerSetRelativeStOther,             STAMTYPE_COUNTER, "/TM/TimerSetRelative/StOther",        STAMUNIT_OCCURENCES, "Other states");
    STAM_REG(pVM, &pVM->tm.s.StatTimerSetRelativeStPendStop,          STAMTYPE_COUNTER, "/TM/TimerSetRelative/StPendStop",     STAMUNIT_OCCURENCES, "PENDING_STOP");
    STAM_REG(pVM, &pVM->tm.s.StatTimerSetRelativeStPendStopSched,     STAMTYPE_COUNTER, "/TM/TimerSetRelative/StPendStopSched",STAMUNIT_OCCURENCES, "PENDING_STOP_SCHEDULE");
    STAM_REG(pVM, &pVM->tm.s.StatTimerSetRelativeStPendSched,         STAMTYPE_COUNTER, "/TM/TimerSetRelative/StPendSched",    STAMUNIT_OCCURENCES, "PENDING_SCHEDULE");
    STAM_REG(pVM, &pVM->tm.s.StatTimerSetRelativeStPendResched,       STAMTYPE_COUNTER, "/TM/TimerSetRelative/StPendResched",  STAMUNIT_OCCURENCES, "PENDING_RESCHEDULE");
    STAM_REG(pVM, &pVM->tm.s.StatTimerSetRelativeStStopped,           STAMTYPE_COUNTER, "/TM/TimerSetRelative/StStopped",      STAMUNIT_OCCURENCES, "STOPPED");

    STAM_REG(pVM, &pVM->tm.s.StatTimerStopR3,                         STAMTYPE_PROFILE, "/TM/TimerStopR3",                 STAMUNIT_TICKS_PER_CALL, "Profiling TMTimerStop calls made in ring-3.");
    STAM_REG(pVM, &pVM->tm.s.StatTimerStopRZ,                         STAMTYPE_PROFILE, "/TM/TimerStopRZ",                 STAMUNIT_TICKS_PER_CALL, "Profiling TMTimerStop calls made in ring-0 / RC.");

    STAM_REG(pVM, &pVM->tm.s.StatVirtualGet,                          STAMTYPE_COUNTER, "/TM/VirtualGet",                      STAMUNIT_OCCURENCES, "The number of times TMTimerGet was called when the clock was running.");
    STAM_REG(pVM, &pVM->tm.s.StatVirtualGetSetFF,                     STAMTYPE_COUNTER, "/TM/VirtualGetSetFF",                 STAMUNIT_OCCURENCES, "Times we set the FF when calling TMTimerGet.");
    STAM_REG(pVM, &pVM->tm.s.StatVirtualSyncGet,                      STAMTYPE_COUNTER, "/TM/VirtualSyncGet",                  STAMUNIT_OCCURENCES, "The number of times tmVirtualSyncGetEx was called.");
    STAM_REG(pVM, &pVM->tm.s.StatVirtualSyncGetELoop,                 STAMTYPE_COUNTER, "/TM/VirtualSyncGet/ELoop",            STAMUNIT_OCCURENCES, "Times tmVirtualSyncGetEx has given up getting a consistent virtual sync data set.");
    STAM_REG(pVM, &pVM->tm.s.StatVirtualSyncGetExpired,               STAMTYPE_COUNTER, "/TM/VirtualSyncGet/Expired",          STAMUNIT_OCCURENCES, "Times tmVirtualSyncGetEx encountered an expired timer stopping the clock.");
    STAM_REG(pVM, &pVM->tm.s.StatVirtualSyncGetLocked,                STAMTYPE_COUNTER, "/TM/VirtualSyncGet/Locked",           STAMUNIT_OCCURENCES, "Times we successfully acquired the lock in tmVirtualSyncGetEx.");
    STAM_REG(pVM, &pVM->tm.s.StatVirtualSyncGetLockless,              STAMTYPE_COUNTER, "/TM/VirtualSyncGet/Lockless",         STAMUNIT_OCCURENCES, "Times tmVirtualSyncGetEx returned without needing to take the lock.");
    STAM_REG(pVM, &pVM->tm.s.StatVirtualSyncGetSetFF,                 STAMTYPE_COUNTER, "/TM/VirtualSyncGet/SetFF",            STAMUNIT_OCCURENCES, "Times we set the FF when calling tmVirtualSyncGetEx.");
    STAM_REG(pVM, &pVM->tm.s.StatVirtualPause,                        STAMTYPE_COUNTER, "/TM/VirtualPause",                    STAMUNIT_OCCURENCES, "The number of times TMR3TimerPause was called.");
    STAM_REG(pVM, &pVM->tm.s.StatVirtualResume,                       STAMTYPE_COUNTER, "/TM/VirtualResume",                   STAMUNIT_OCCURENCES, "The number of times TMR3TimerResume was called.");

    STAM_REG(pVM, &pVM->tm.s.StatTimerCallbackSetFF,                  STAMTYPE_COUNTER, "/TM/CallbackSetFF",                   STAMUNIT_OCCURENCES, "The number of times the timer callback set FF.");

    STAM_REG(pVM, &pVM->tm.s.StatTSCCatchupLE010,                     STAMTYPE_COUNTER, "/TM/TSC/Intercept/CatchupLE010",      STAMUNIT_OCCURENCES, "In catch-up mode, 10% or lower.");
    STAM_REG(pVM, &pVM->tm.s.StatTSCCatchupLE025,                     STAMTYPE_COUNTER, "/TM/TSC/Intercept/CatchupLE025",      STAMUNIT_OCCURENCES, "In catch-up mode, 25%-11%.");
    STAM_REG(pVM, &pVM->tm.s.StatTSCCatchupLE100,                     STAMTYPE_COUNTER, "/TM/TSC/Intercept/CatchupLE100",      STAMUNIT_OCCURENCES, "In catch-up mode, 100%-26%.");
    STAM_REG(pVM, &pVM->tm.s.StatTSCCatchupOther,                     STAMTYPE_COUNTER, "/TM/TSC/Intercept/CatchupOther",      STAMUNIT_OCCURENCES, "In catch-up mode, > 100%.");
    STAM_REG(pVM, &pVM->tm.s.StatTSCNotFixed,                         STAMTYPE_COUNTER, "/TM/TSC/Intercept/NotFixed",          STAMUNIT_OCCURENCES, "TSC is not fixed, it may run at variable speed.");
    STAM_REG(pVM, &pVM->tm.s.StatTSCNotTicking,                       STAMTYPE_COUNTER, "/TM/TSC/Intercept/NotTicking",        STAMUNIT_OCCURENCES, "TSC is not ticking.");
    STAM_REG(pVM, &pVM->tm.s.StatTSCSyncNotTicking,                   STAMTYPE_COUNTER, "/TM/TSC/Intercept/SyncNotTicking",    STAMUNIT_OCCURENCES, "VirtualSync isn't ticking.");
    STAM_REG(pVM, &pVM->tm.s.StatTSCWarp,                             STAMTYPE_COUNTER, "/TM/TSC/Intercept/Warp",              STAMUNIT_OCCURENCES, "Warpdrive is active.");
    STAM_REG(pVM, &pVM->tm.s.StatTSCSet,                              STAMTYPE_COUNTER, "/TM/TSC/Sets",                        STAMUNIT_OCCURENCES, "Calls to TMCpuTickSet.");
    STAM_REG(pVM, &pVM->tm.s.StatTSCUnderflow,                        STAMTYPE_COUNTER, "/TM/TSC/Underflow",                   STAMUNIT_OCCURENCES, "TSC underflow; corrected with last seen value .");
#endif /* VBOX_WITH_STATISTICS */

    for (VMCPUID i = 0; i < pVM->cCpus; i++)
    {
        STAMR3RegisterF(pVM, &pVM->aCpus[i].tm.s.offTSCRawSrc,          STAMTYPE_U64, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS, "TSC offset relative the raw source",           "/TM/TSC/offCPU%u", i);
#ifndef VBOX_WITHOUT_NS_ACCOUNTING
# if defined(VBOX_WITH_STATISTICS) || defined(VBOX_WITH_NS_ACCOUNTING_STATS)
        STAMR3RegisterF(pVM, &pVM->aCpus[i].tm.s.StatNsTotal,       STAMTYPE_COUNTER, STAMVISIBILITY_ALWAYS, STAMUNIT_NS,               "Resettable: Total CPU run time.",   "/TM/CPU/%02u", i);
        STAMR3RegisterF(pVM, &pVM->aCpus[i].tm.s.StatNsExecuting,   STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_NS_PER_OCCURENCE, "Resettable: Time spent executing guest code.",    "/TM/CPU/%02u/PrfExecuting", i);
        STAMR3RegisterF(pVM, &pVM->aCpus[i].tm.s.StatNsExecLong,    STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_NS_PER_OCCURENCE, "Resettable: Time spent executing guest code - long hauls.",    "/TM/CPU/%02u/PrfExecLong", i);
        STAMR3RegisterF(pVM, &pVM->aCpus[i].tm.s.StatNsExecShort,   STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_NS_PER_OCCURENCE, "Resettable: Time spent executing guest code - short stretches.",    "/TM/CPU/%02u/PrfExecShort", i);
        STAMR3RegisterF(pVM, &pVM->aCpus[i].tm.s.StatNsExecTiny,    STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_NS_PER_OCCURENCE, "Resettable: Time spent executing guest code - tiny bits.",    "/TM/CPU/%02u/PrfExecTiny", i);
        STAMR3RegisterF(pVM, &pVM->aCpus[i].tm.s.StatNsHalted,      STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_NS_PER_OCCURENCE, "Resettable: Time spent halted.",                  "/TM/CPU/%02u/PrfHalted", i);
        STAMR3RegisterF(pVM, &pVM->aCpus[i].tm.s.StatNsOther,       STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_NS_PER_OCCURENCE, "Resettable: Time spent in the VMM or preempted.", "/TM/CPU/%02u/PrfOther", i);
# endif
        STAMR3RegisterF(pVM, &pVM->aCpus[i].tm.s.cNsTotal,              STAMTYPE_U64, STAMVISIBILITY_ALWAYS, STAMUNIT_NS,    "Total CPU run time.",                          "/TM/CPU/%02u/cNsTotal", i);
        STAMR3RegisterF(pVM, &pVM->aCpus[i].tm.s.cNsExecuting,          STAMTYPE_U64, STAMVISIBILITY_ALWAYS, STAMUNIT_NS,    "Time spent executing guest code.",             "/TM/CPU/%02u/cNsExecuting", i);
        STAMR3RegisterF(pVM, &pVM->aCpus[i].tm.s.cNsHalted,             STAMTYPE_U64, STAMVISIBILITY_ALWAYS, STAMUNIT_NS,    "Time spent halted.",                           "/TM/CPU/%02u/cNsHalted", i);
        STAMR3RegisterF(pVM, &pVM->aCpus[i].tm.s.cNsOther,              STAMTYPE_U64, STAMVISIBILITY_ALWAYS, STAMUNIT_NS,    "Time spent in the VMM or preempted.",          "/TM/CPU/%02u/cNsOther", i);
        STAMR3RegisterF(pVM, &pVM->aCpus[i].tm.s.cPeriodsExecuting,     STAMTYPE_U64, STAMVISIBILITY_ALWAYS, STAMUNIT_COUNT, "Times executed guest code.",                   "/TM/CPU/%02u/cPeriodsExecuting", i);
        STAMR3RegisterF(pVM, &pVM->aCpus[i].tm.s.cPeriodsHalted,        STAMTYPE_U64, STAMVISIBILITY_ALWAYS, STAMUNIT_COUNT, "Times halted.",                                "/TM/CPU/%02u/cPeriodsHalted", i);
        STAMR3RegisterF(pVM, &pVM->aCpus[i].tm.s.CpuLoad.cPctExecuting, STAMTYPE_U8,  STAMVISIBILITY_ALWAYS, STAMUNIT_PCT,   "Time spent executing guest code recently.",    "/TM/CPU/%02u/pctExecuting", i);
        STAMR3RegisterF(pVM, &pVM->aCpus[i].tm.s.CpuLoad.cPctHalted,    STAMTYPE_U8,  STAMVISIBILITY_ALWAYS, STAMUNIT_PCT,   "Time spent halted recently.",                  "/TM/CPU/%02u/pctHalted", i);
        STAMR3RegisterF(pVM, &pVM->aCpus[i].tm.s.CpuLoad.cPctOther,     STAMTYPE_U8,  STAMVISIBILITY_ALWAYS, STAMUNIT_PCT,   "Time spent in the VMM or preempted recently.", "/TM/CPU/%02u/pctOther", i);
#endif
    }
#ifndef VBOX_WITHOUT_NS_ACCOUNTING
    STAMR3RegisterF(pVM, &pVM->tm.s.CpuLoad.cPctExecuting, STAMTYPE_U8,  STAMVISIBILITY_ALWAYS, STAMUNIT_PCT,   "Time spent executing guest code recently.",    "/TM/CPU/pctExecuting");
    STAMR3RegisterF(pVM, &pVM->tm.s.CpuLoad.cPctHalted,    STAMTYPE_U8,  STAMVISIBILITY_ALWAYS, STAMUNIT_PCT,   "Time spent halted recently.",                  "/TM/CPU/pctHalted");
    STAMR3RegisterF(pVM, &pVM->tm.s.CpuLoad.cPctOther,     STAMTYPE_U8,  STAMVISIBILITY_ALWAYS, STAMUNIT_PCT,   "Time spent in the VMM or preempted recently.", "/TM/CPU/pctOther");
#endif

#ifdef VBOX_WITH_STATISTICS
    STAM_REG(pVM, &pVM->tm.s.StatVirtualSyncCatchup,              STAMTYPE_PROFILE_ADV, "/TM/VirtualSync/CatchUp",    STAMUNIT_TICKS_PER_OCCURENCE, "Counting and measuring the times spent catching up.");
    STAM_REG(pVM, (void *)&pVM->tm.s.fVirtualSyncCatchUp,                  STAMTYPE_U8, "/TM/VirtualSync/CatchUpActive",             STAMUNIT_NONE, "Catch-Up active indicator.");
    STAM_REG(pVM, (void *)&pVM->tm.s.u32VirtualSyncCatchUpPercentage,     STAMTYPE_U32, "/TM/VirtualSync/CatchUpPercentage",          STAMUNIT_PCT, "The catch-up percentage. (+100/100 to get clock multiplier)");
    STAM_REG(pVM, &pVM->tm.s.StatVirtualSyncFF,                       STAMTYPE_PROFILE, "/TM/VirtualSync/FF",         STAMUNIT_TICKS_PER_OCCURENCE, "Time spent in TMR3VirtualSyncFF by all but the dedicate timer EMT.");
    STAM_REG(pVM, &pVM->tm.s.StatVirtualSyncGiveUp,                   STAMTYPE_COUNTER, "/TM/VirtualSync/GiveUp",              STAMUNIT_OCCURENCES, "Times the catch-up was abandoned.");
    STAM_REG(pVM, &pVM->tm.s.StatVirtualSyncGiveUpBeforeStarting,     STAMTYPE_COUNTER, "/TM/VirtualSync/GiveUpBeforeStarting",STAMUNIT_OCCURENCES, "Times the catch-up was abandoned before even starting. (Typically debugging++.)");
    STAM_REG(pVM, &pVM->tm.s.StatVirtualSyncRun,                      STAMTYPE_COUNTER, "/TM/VirtualSync/Run",                 STAMUNIT_OCCURENCES, "Times the virtual sync timer queue was considered.");
    STAM_REG(pVM, &pVM->tm.s.StatVirtualSyncRunRestart,               STAMTYPE_COUNTER, "/TM/VirtualSync/Run/Restarts",        STAMUNIT_OCCURENCES, "Times the clock was restarted after a run.");
    STAM_REG(pVM, &pVM->tm.s.StatVirtualSyncRunStop,                  STAMTYPE_COUNTER, "/TM/VirtualSync/Run/Stop",            STAMUNIT_OCCURENCES, "Times the clock was stopped when calculating the current time before examining the timers.");
    STAM_REG(pVM, &pVM->tm.s.StatVirtualSyncRunStoppedAlready,        STAMTYPE_COUNTER, "/TM/VirtualSync/Run/StoppedAlready",  STAMUNIT_OCCURENCES, "Times the clock was already stopped elsewhere (TMVirtualSyncGet).");
    STAM_REG(pVM, &pVM->tm.s.StatVirtualSyncRunSlack,                 STAMTYPE_PROFILE, "/TM/VirtualSync/Run/Slack",     STAMUNIT_NS_PER_OCCURENCE, "The scheduling slack. (Catch-up handed out when running timers.)");
    for (unsigned i = 0; i < RT_ELEMENTS(pVM->tm.s.aVirtualSyncCatchUpPeriods); i++)
    {
        STAMR3RegisterF(pVM, &pVM->tm.s.aVirtualSyncCatchUpPeriods[i].u32Percentage,    STAMTYPE_U32, STAMVISIBILITY_ALWAYS,          STAMUNIT_PCT, "The catch-up percentage.",         "/TM/VirtualSync/Periods/%u", i);
        STAMR3RegisterF(pVM, &pVM->tm.s.aStatVirtualSyncCatchupAdjust[i],           STAMTYPE_COUNTER, STAMVISIBILITY_ALWAYS,   STAMUNIT_OCCURENCES, "Times adjusted to this period.",   "/TM/VirtualSync/Periods/%u/Adjust", i);
        STAMR3RegisterF(pVM, &pVM->tm.s.aStatVirtualSyncCatchupInitial[i],          STAMTYPE_COUNTER, STAMVISIBILITY_ALWAYS,   STAMUNIT_OCCURENCES, "Times started in this period.",    "/TM/VirtualSync/Periods/%u/Initial", i);
        STAMR3RegisterF(pVM, &pVM->tm.s.aVirtualSyncCatchUpPeriods[i].u64Start,         STAMTYPE_U64, STAMVISIBILITY_ALWAYS,           STAMUNIT_NS, "Start of this period (lag).",      "/TM/VirtualSync/Periods/%u/Start", i);
    }
#endif /* VBOX_WITH_STATISTICS */

    /*
     * Register info handlers.
     */
    DBGFR3InfoRegisterInternalEx(pVM, "timers",       "Dumps all timers. No arguments.",          tmR3TimerInfo,        DBGFINFO_FLAGS_RUN_ON_EMT);
    DBGFR3InfoRegisterInternalEx(pVM, "activetimers", "Dumps active all timers. No arguments.",   tmR3TimerInfoActive,  DBGFINFO_FLAGS_RUN_ON_EMT);
    DBGFR3InfoRegisterInternalEx(pVM, "clocks",       "Display the time of the various clocks.",  tmR3InfoClocks,       DBGFINFO_FLAGS_RUN_ON_EMT);

    return VINF_SUCCESS;
}


/**
 * Checks if the host CPU has a fixed TSC frequency.
 *
 * @returns true if it has, false if it hasn't.
 *
 * @remark  This test doesn't bother with very old CPUs that don't do power
 *          management or any other stuff that might influence the TSC rate.
 *          This isn't currently relevant.
 */
static bool tmR3HasFixedTSC(PVM pVM)
{
    if (ASMHasCpuId())
    {
        uint32_t uEAX, uEBX, uECX, uEDX;

        if (CPUMGetHostCpuVendor(pVM) == CPUMCPUVENDOR_AMD)
        {
            /*
             * AuthenticAMD - Check for APM support and that TscInvariant is set.
             *
             * This test isn't correct with respect to fixed/non-fixed TSC and
             * older models, but this isn't relevant since the result is currently
             * only used for making a decision on AMD-V models.
             */
            ASMCpuId(0x80000000, &uEAX, &uEBX, &uECX, &uEDX);
            if (uEAX >= 0x80000007)
            {
                PSUPGLOBALINFOPAGE pGip = g_pSUPGlobalInfoPage;

                ASMCpuId(0x80000007, &uEAX, &uEBX, &uECX, &uEDX);
                if (   (uEDX & X86_CPUID_AMD_ADVPOWER_EDX_TSCINVAR) /* TscInvariant */
                    && pGip->u32Mode == SUPGIPMODE_SYNC_TSC /* no fixed tsc if the gip timer is in async mode */)
                    return true;
            }
        }
        else if (CPUMGetHostCpuVendor(pVM) == CPUMCPUVENDOR_INTEL)
        {
            /*
             * GenuineIntel - Check the model number.
             *
             * This test is lacking in the same way and for the same reasons
             * as the AMD test above.
             */
            ASMCpuId(1, &uEAX, &uEBX, &uECX, &uEDX);
            unsigned uModel  = (uEAX >> 4) & 0x0f;
            unsigned uFamily = (uEAX >> 8) & 0x0f;
            if (uFamily == 0x0f)
                uFamily += (uEAX >> 20) & 0xff;
            if (uFamily >= 0x06)
                uModel += ((uEAX >> 16) & 0x0f) << 4;
            if (    (uFamily == 0x0f /*P4*/     && uModel >= 0x03)
                ||  (uFamily == 0x06 /*P2/P3*/  && uModel >= 0x0e))
                return true;
        }
    }
    return false;
}


/**
 * Calibrate the CPU tick.
 *
 * @returns Number of ticks per second.
 */
static uint64_t tmR3CalibrateTSC(PVM pVM)
{
    /*
     * Use GIP when available present.
     */
    uint64_t    u64Hz;
    PSUPGLOBALINFOPAGE pGip = g_pSUPGlobalInfoPage;
    if (    pGip
        &&  pGip->u32Magic == SUPGLOBALINFOPAGE_MAGIC)
    {
        unsigned iCpu = pGip->u32Mode != SUPGIPMODE_ASYNC_TSC ? 0 : ASMGetApicId();
        if (iCpu >= RT_ELEMENTS(pGip->aCPUs))
            AssertReleaseMsgFailed(("iCpu=%d - the ApicId is too high. send VBox.log and hardware specs!\n", iCpu));
        else
        {
            if (tmR3HasFixedTSC(pVM))
                /* Sleep a bit to get a more reliable CpuHz value. */
                RTThreadSleep(32);
            else
            {
                /* Spin for 40ms to try push up the CPU frequency and get a more reliable CpuHz value. */
                const uint64_t u64 = RTTimeMilliTS();
                while ((RTTimeMilliTS() - u64) < 40 /*ms*/)
                    /* nothing */;
            }

            pGip = g_pSUPGlobalInfoPage;
            if (    pGip
                &&  pGip->u32Magic == SUPGLOBALINFOPAGE_MAGIC
                &&  (u64Hz = pGip->aCPUs[iCpu].u64CpuHz)
                &&  u64Hz != ~(uint64_t)0)
                return u64Hz;
        }
    }

    /* call this once first to make sure it's initialized. */
    RTTimeNanoTS();

    /*
     * Yield the CPU to increase our chances of getting
     * a correct value.
     */
    RTThreadYield();                    /* Try avoid interruptions between TSC and NanoTS samplings. */
    static const unsigned   s_auSleep[5] = { 50, 30, 30, 40, 40 };
    uint64_t                au64Samples[5];
    unsigned                i;
    for (i = 0; i < RT_ELEMENTS(au64Samples); i++)
    {
        RTMSINTERVAL    cMillies;
        int             cTries   = 5;
        uint64_t        u64Start = ASMReadTSC();
        uint64_t        u64End;
        uint64_t        StartTS  = RTTimeNanoTS();
        uint64_t        EndTS;
        do
        {
            RTThreadSleep(s_auSleep[i]);
            u64End = ASMReadTSC();
            EndTS  = RTTimeNanoTS();
            cMillies = (RTMSINTERVAL)((EndTS - StartTS + 500000) / 1000000);
        } while (   cMillies == 0       /* the sleep may be interrupted... */
                 || (cMillies < 20 && --cTries > 0));
        uint64_t    u64Diff = u64End - u64Start;

        au64Samples[i] = (u64Diff * 1000) / cMillies;
        AssertMsg(cTries > 0, ("cMillies=%d i=%d\n", cMillies, i));
    }

    /*
     * Discard the highest and lowest results and calculate the average.
     */
    unsigned iHigh = 0;
    unsigned iLow = 0;
    for (i = 1; i < RT_ELEMENTS(au64Samples); i++)
    {
        if (au64Samples[i] < au64Samples[iLow])
            iLow = i;
        if (au64Samples[i] > au64Samples[iHigh])
            iHigh = i;
    }
    au64Samples[iLow] = 0;
    au64Samples[iHigh] = 0;

    u64Hz = au64Samples[0];
    for (i = 1; i < RT_ELEMENTS(au64Samples); i++)
        u64Hz += au64Samples[i];
    u64Hz /= RT_ELEMENTS(au64Samples) - 2;

    return u64Hz;
}


/**
 * Finalizes the TM initialization.
 *
 * @returns VBox status code.
 * @param   pVM         The VM to operate on.
 */
VMM_INT_DECL(int) TMR3InitFinalize(PVM pVM)
{
    int rc;

    /*
     * Resolve symbols.
     */
    rc = PDMR3LdrGetSymbolRC(pVM, NULL, "tmVirtualNanoTSBad",          &pVM->tm.s.VirtualGetRawDataRC.pfnBad);
    AssertRCReturn(rc, rc);
    rc = PDMR3LdrGetSymbolRC(pVM, NULL, "tmVirtualNanoTSRediscover",   &pVM->tm.s.VirtualGetRawDataRC.pfnRediscover);
    AssertRCReturn(rc, rc);
    if (pVM->tm.s.pfnVirtualGetRawR3       == RTTimeNanoTSLFenceSync)
        rc = PDMR3LdrGetSymbolRC(pVM, NULL, "RTTimeNanoTSLFenceSync",  &pVM->tm.s.pfnVirtualGetRawRC);
    else if (pVM->tm.s.pfnVirtualGetRawR3  == RTTimeNanoTSLFenceAsync)
        rc = PDMR3LdrGetSymbolRC(pVM, NULL, "RTTimeNanoTSLFenceAsync", &pVM->tm.s.pfnVirtualGetRawRC);
    else if (pVM->tm.s.pfnVirtualGetRawR3  == RTTimeNanoTSLegacySync)
        rc = PDMR3LdrGetSymbolRC(pVM, NULL, "RTTimeNanoTSLegacySync",  &pVM->tm.s.pfnVirtualGetRawRC);
    else if (pVM->tm.s.pfnVirtualGetRawR3  == RTTimeNanoTSLegacyAsync)
        rc = PDMR3LdrGetSymbolRC(pVM, NULL, "RTTimeNanoTSLegacyAsync", &pVM->tm.s.pfnVirtualGetRawRC);
    else
        AssertFatalFailed();
    AssertRCReturn(rc, rc);

    rc = PDMR3LdrGetSymbolR0(pVM, NULL, "tmVirtualNanoTSBad",          &pVM->tm.s.VirtualGetRawDataR0.pfnBad);
    AssertRCReturn(rc, rc);
    rc = PDMR3LdrGetSymbolR0(pVM, NULL, "tmVirtualNanoTSRediscover",   &pVM->tm.s.VirtualGetRawDataR0.pfnRediscover);
    AssertRCReturn(rc, rc);
    if (pVM->tm.s.pfnVirtualGetRawR3       == RTTimeNanoTSLFenceSync)
        rc = PDMR3LdrGetSymbolR0(pVM, NULL, "RTTimeNanoTSLFenceSync",  &pVM->tm.s.pfnVirtualGetRawR0);
    else if (pVM->tm.s.pfnVirtualGetRawR3  == RTTimeNanoTSLFenceAsync)
        rc = PDMR3LdrGetSymbolR0(pVM, NULL, "RTTimeNanoTSLFenceAsync", &pVM->tm.s.pfnVirtualGetRawR0);
    else if (pVM->tm.s.pfnVirtualGetRawR3  == RTTimeNanoTSLegacySync)
        rc = PDMR3LdrGetSymbolR0(pVM, NULL, "RTTimeNanoTSLegacySync",  &pVM->tm.s.pfnVirtualGetRawR0);
    else if (pVM->tm.s.pfnVirtualGetRawR3  == RTTimeNanoTSLegacyAsync)
        rc = PDMR3LdrGetSymbolR0(pVM, NULL, "RTTimeNanoTSLegacyAsync", &pVM->tm.s.pfnVirtualGetRawR0);
    else
        AssertFatalFailed();
    AssertRCReturn(rc, rc);

#ifndef VBOX_WITHOUT_NS_ACCOUNTING
    /*
     * Create a timer for refreshing the CPU load stats.
     */
    PTMTIMER pTimer;
    rc = TMR3TimerCreateInternal(pVM, TMCLOCK_REAL, tmR3CpuLoadTimer, NULL, "CPU Load Timer", &pTimer);
    if (RT_SUCCESS(rc))
        rc = TMTimerSetMillies(pTimer, 1000);
#endif

    return rc;
}


/**
 * Applies relocations to data and code managed by this
 * component. This function will be called at init and
 * whenever the VMM need to relocate it self inside the GC.
 *
 * @param   pVM     The VM.
 * @param   offDelta    Relocation delta relative to old location.
 */
VMM_INT_DECL(void) TMR3Relocate(PVM pVM, RTGCINTPTR offDelta)
{
    int rc;
    LogFlow(("TMR3Relocate\n"));

    pVM->tm.s.pvGIPRC = MMHyperR3ToRC(pVM, pVM->tm.s.pvGIPR3);
    pVM->tm.s.paTimerQueuesRC = MMHyperR3ToRC(pVM, pVM->tm.s.paTimerQueuesR3);
    pVM->tm.s.paTimerQueuesR0 = MMHyperR3ToR0(pVM, pVM->tm.s.paTimerQueuesR3);

    pVM->tm.s.VirtualGetRawDataRC.pu64Prev = MMHyperR3ToRC(pVM, (void *)&pVM->tm.s.u64VirtualRawPrev);
    AssertFatal(pVM->tm.s.VirtualGetRawDataRC.pu64Prev);
    rc = PDMR3LdrGetSymbolRC(pVM, NULL, "tmVirtualNanoTSBad",          &pVM->tm.s.VirtualGetRawDataRC.pfnBad);
    AssertFatalRC(rc);
    rc = PDMR3LdrGetSymbolRC(pVM, NULL, "tmVirtualNanoTSRediscover",   &pVM->tm.s.VirtualGetRawDataRC.pfnRediscover);
    AssertFatalRC(rc);

    if (pVM->tm.s.pfnVirtualGetRawR3       == RTTimeNanoTSLFenceSync)
        rc = PDMR3LdrGetSymbolRC(pVM, NULL, "RTTimeNanoTSLFenceSync",  &pVM->tm.s.pfnVirtualGetRawRC);
    else if (pVM->tm.s.pfnVirtualGetRawR3  == RTTimeNanoTSLFenceAsync)
        rc = PDMR3LdrGetSymbolRC(pVM, NULL, "RTTimeNanoTSLFenceAsync", &pVM->tm.s.pfnVirtualGetRawRC);
    else if (pVM->tm.s.pfnVirtualGetRawR3  == RTTimeNanoTSLegacySync)
        rc = PDMR3LdrGetSymbolRC(pVM, NULL, "RTTimeNanoTSLegacySync",  &pVM->tm.s.pfnVirtualGetRawRC);
    else if (pVM->tm.s.pfnVirtualGetRawR3  == RTTimeNanoTSLegacyAsync)
        rc = PDMR3LdrGetSymbolRC(pVM, NULL, "RTTimeNanoTSLegacyAsync", &pVM->tm.s.pfnVirtualGetRawRC);
    else
        AssertFatalFailed();
    AssertFatalRC(rc);

    /*
     * Iterate the timers updating the pVMRC pointers.
     */
    for (PTMTIMER pTimer = pVM->tm.s.pCreated; pTimer; pTimer = pTimer->pBigNext)
    {
        pTimer->pVMRC = pVM->pVMRC;
        pTimer->pVMR0 = pVM->pVMR0;
    }
}


/**
 * Terminates the TM.
 *
 * Termination means cleaning up and freeing all resources,
 * the VM it self is at this point powered off or suspended.
 *
 * @returns VBox status code.
 * @param   pVM         The VM to operate on.
 */
VMM_INT_DECL(int) TMR3Term(PVM pVM)
{
    AssertMsg(pVM->tm.s.offVM, ("bad init order!\n"));
    if (pVM->tm.s.pTimer)
    {
        int rc = RTTimerDestroy(pVM->tm.s.pTimer);
        AssertRC(rc);
        pVM->tm.s.pTimer = NULL;
    }

    return VINF_SUCCESS;
}


/**
 * The VM is being reset.
 *
 * For the TM component this means that a rescheduling is preformed,
 * the FF is cleared and but without running the queues. We'll have to
 * check if this makes sense or not, but it seems like a good idea now....
 *
 * @param   pVM     VM handle.
 */
VMM_INT_DECL(void) TMR3Reset(PVM pVM)
{
    LogFlow(("TMR3Reset:\n"));
    VM_ASSERT_EMT(pVM);
    tmTimerLock(pVM);

    /*
     * Abort any pending catch up.
     * This isn't perfect...
     */
    if (pVM->tm.s.fVirtualSyncCatchUp)
    {
        const uint64_t offVirtualNow = TMVirtualGetNoCheck(pVM);
        const uint64_t offVirtualSyncNow = TMVirtualSyncGetNoCheck(pVM);
        if (pVM->tm.s.fVirtualSyncCatchUp)
        {
            STAM_PROFILE_ADV_STOP(&pVM->tm.s.StatVirtualSyncCatchup, c);

            const uint64_t offOld = pVM->tm.s.offVirtualSyncGivenUp;
            const uint64_t offNew = offVirtualNow - offVirtualSyncNow;
            Assert(offOld <= offNew);
            ASMAtomicWriteU64((uint64_t volatile *)&pVM->tm.s.offVirtualSyncGivenUp, offNew);
            ASMAtomicWriteU64((uint64_t volatile *)&pVM->tm.s.offVirtualSync, offNew);
            ASMAtomicWriteBool(&pVM->tm.s.fVirtualSyncCatchUp, false);
            LogRel(("TM: Aborting catch-up attempt on reset with a %'RU64 ns lag on reset; new total: %'RU64 ns\n", offNew - offOld, offNew));
        }
    }

    /*
     * Process the queues.
     */
    for (int i = 0; i < TMCLOCK_MAX; i++)
        tmTimerQueueSchedule(pVM, &pVM->tm.s.paTimerQueuesR3[i]);
#ifdef VBOX_STRICT
    tmTimerQueuesSanityChecks(pVM, "TMR3Reset");
#endif

    PVMCPU pVCpuDst = &pVM->aCpus[pVM->tm.s.idTimerCpu];
    VMCPU_FF_CLEAR(pVCpuDst, VMCPU_FF_TIMER); /** @todo FIXME: this isn't right. */
    tmTimerUnlock(pVM);
}


/**
 * Resolve a builtin RC symbol.
 * Called by PDM when loading or relocating GC modules.
 *
 * @returns VBox status
 * @param   pVM             VM Handle.
 * @param   pszSymbol       Symbol to resolve.
 * @param   pRCPtrValue     Where to store the symbol value.
 * @remark  This has to     work before TMR3Relocate() is called.
 */
VMM_INT_DECL(int) TMR3GetImportRC(PVM pVM, const char *pszSymbol, PRTRCPTR pRCPtrValue)
{
    if (!strcmp(pszSymbol, "g_pSUPGlobalInfoPage"))
        *pRCPtrValue = MMHyperR3ToRC(pVM, &pVM->tm.s.pvGIPRC);
    //else if (..)
    else
        return VERR_SYMBOL_NOT_FOUND;
    return VINF_SUCCESS;
}


/**
 * Execute state save operation.
 *
 * @returns VBox status code.
 * @param   pVM             VM Handle.
 * @param   pSSM            SSM operation handle.
 */
static DECLCALLBACK(int) tmR3Save(PVM pVM, PSSMHANDLE pSSM)
{
    LogFlow(("tmR3Save:\n"));
#ifdef VBOX_STRICT
    for (VMCPUID i = 0; i < pVM->cCpus; i++)
    {
        PVMCPU pVCpu = &pVM->aCpus[i];
        Assert(!pVCpu->tm.s.fTSCTicking);
    }
    Assert(!pVM->tm.s.cVirtualTicking);
    Assert(!pVM->tm.s.fVirtualSyncTicking);
#endif

    /*
     * Save the virtual clocks.
     */
    /* the virtual clock. */
    SSMR3PutU64(pSSM, TMCLOCK_FREQ_VIRTUAL);
    SSMR3PutU64(pSSM, pVM->tm.s.u64Virtual);

    /* the virtual timer synchronous clock. */
    SSMR3PutU64(pSSM, pVM->tm.s.u64VirtualSync);
    SSMR3PutU64(pSSM, pVM->tm.s.offVirtualSync);
    SSMR3PutU64(pSSM, pVM->tm.s.offVirtualSyncGivenUp);
    SSMR3PutU64(pSSM, pVM->tm.s.u64VirtualSyncCatchUpPrev);
    SSMR3PutBool(pSSM, pVM->tm.s.fVirtualSyncCatchUp);

    /* real time clock */
    SSMR3PutU64(pSSM, TMCLOCK_FREQ_REAL);

    /* the cpu tick clock. */
    for (VMCPUID i = 0; i < pVM->cCpus; i++)
    {
        PVMCPU pVCpu = &pVM->aCpus[i];
        SSMR3PutU64(pSSM, TMCpuTickGet(pVCpu));
    }
    return SSMR3PutU64(pSSM, pVM->tm.s.cTSCTicksPerSecond);
}


/**
 * Execute state load operation.
 *
 * @returns VBox status code.
 * @param   pVM             VM Handle.
 * @param   pSSM            SSM operation handle.
 * @param   uVersion        Data layout version.
 * @param   uPass           The data pass.
 */
static DECLCALLBACK(int) tmR3Load(PVM pVM, PSSMHANDLE pSSM, uint32_t uVersion, uint32_t uPass)
{
    LogFlow(("tmR3Load:\n"));

    Assert(uPass == SSM_PASS_FINAL); NOREF(uPass);
#ifdef VBOX_STRICT
    for (VMCPUID i = 0; i < pVM->cCpus; i++)
    {
        PVMCPU pVCpu = &pVM->aCpus[i];
        Assert(!pVCpu->tm.s.fTSCTicking);
    }
    Assert(!pVM->tm.s.cVirtualTicking);
    Assert(!pVM->tm.s.fVirtualSyncTicking);
#endif

    /*
     * Validate version.
     */
    if (uVersion != TM_SAVED_STATE_VERSION)
    {
        AssertMsgFailed(("tmR3Load: Invalid version uVersion=%d!\n", uVersion));
        return VERR_SSM_UNSUPPORTED_DATA_UNIT_VERSION;
    }

    /*
     * Load the virtual clock.
     */
    pVM->tm.s.cVirtualTicking = 0;
    /* the virtual clock. */
    uint64_t u64Hz;
    int rc = SSMR3GetU64(pSSM, &u64Hz);
    if (RT_FAILURE(rc))
        return rc;
    if (u64Hz != TMCLOCK_FREQ_VIRTUAL)
    {
        AssertMsgFailed(("The virtual clock frequency differs! Saved: %'RU64 Binary: %'RU64\n",
                         u64Hz, TMCLOCK_FREQ_VIRTUAL));
        return VERR_SSM_VIRTUAL_CLOCK_HZ;
    }
    SSMR3GetU64(pSSM, &pVM->tm.s.u64Virtual);
    pVM->tm.s.u64VirtualOffset = 0;

    /* the virtual timer synchronous clock. */
    pVM->tm.s.fVirtualSyncTicking = false;
    uint64_t u64;
    SSMR3GetU64(pSSM, &u64);
    pVM->tm.s.u64VirtualSync = u64;
    SSMR3GetU64(pSSM, &u64);
    pVM->tm.s.offVirtualSync = u64;
    SSMR3GetU64(pSSM, &u64);
    pVM->tm.s.offVirtualSyncGivenUp = u64;
    SSMR3GetU64(pSSM, &u64);
    pVM->tm.s.u64VirtualSyncCatchUpPrev = u64;
    bool f;
    SSMR3GetBool(pSSM, &f);
    pVM->tm.s.fVirtualSyncCatchUp = f;

    /* the real clock  */
    rc = SSMR3GetU64(pSSM, &u64Hz);
    if (RT_FAILURE(rc))
        return rc;
    if (u64Hz != TMCLOCK_FREQ_REAL)
    {
        AssertMsgFailed(("The real clock frequency differs! Saved: %'RU64 Binary: %'RU64\n",
                         u64Hz, TMCLOCK_FREQ_REAL));
        return VERR_SSM_VIRTUAL_CLOCK_HZ; /* misleading... */
    }

    /* the cpu tick clock. */
    for (VMCPUID i = 0; i < pVM->cCpus; i++)
    {
        PVMCPU pVCpu = &pVM->aCpus[i];

        pVCpu->tm.s.fTSCTicking = false;
        SSMR3GetU64(pSSM, &pVCpu->tm.s.u64TSC);

        if (pVM->tm.s.fTSCUseRealTSC)
            pVCpu->tm.s.offTSCRawSrc = 0; /** @todo TSC restore stuff and HWACC. */
    }

    rc = SSMR3GetU64(pSSM, &u64Hz);
    if (RT_FAILURE(rc))
        return rc;
    if (!pVM->tm.s.fTSCUseRealTSC)
        pVM->tm.s.cTSCTicksPerSecond = u64Hz;

    LogRel(("TM: cTSCTicksPerSecond=%#RX64 (%'RU64) fTSCVirtualized=%RTbool fTSCUseRealTSC=%RTbool (state load)\n",
            pVM->tm.s.cTSCTicksPerSecond, pVM->tm.s.cTSCTicksPerSecond, pVM->tm.s.fTSCVirtualized, pVM->tm.s.fTSCUseRealTSC));

    /*
     * Make sure timers get rescheduled immediately.
     */
    PVMCPU pVCpuDst = &pVM->aCpus[pVM->tm.s.idTimerCpu];
    VMCPU_FF_SET(pVCpuDst, VMCPU_FF_TIMER);

    return VINF_SUCCESS;
}


/**
 * Internal TMR3TimerCreate worker.
 *
 * @returns VBox status code.
 * @param   pVM         The VM handle.
 * @param   enmClock    The timer clock.
 * @param   pszDesc     The timer description.
 * @param   ppTimer     Where to store the timer pointer on success.
 */
static int tmr3TimerCreate(PVM pVM, TMCLOCK enmClock, const char *pszDesc, PPTMTIMERR3 ppTimer)
{
    VM_ASSERT_EMT(pVM);

    /*
     * Allocate the timer.
     */
    PTMTIMERR3 pTimer = NULL;
    if (pVM->tm.s.pFree && VM_IS_EMT(pVM))
    {
        pTimer = pVM->tm.s.pFree;
        pVM->tm.s.pFree = pTimer->pBigNext;
        Log3(("TM: Recycling timer %p, new free head %p.\n", pTimer, pTimer->pBigNext));
    }

    if (!pTimer)
    {
        int rc = MMHyperAlloc(pVM, sizeof(*pTimer), 0, MM_TAG_TM, (void **)&pTimer);
        if (RT_FAILURE(rc))
            return rc;
        Log3(("TM: Allocated new timer %p\n", pTimer));
    }

    /*
     * Initialize it.
     */
    pTimer->u64Expire       = 0;
    pTimer->enmClock        = enmClock;
    pTimer->pVMR3           = pVM;
    pTimer->pVMR0           = pVM->pVMR0;
    pTimer->pVMRC           = pVM->pVMRC;
    pTimer->enmState        = TMTIMERSTATE_STOPPED;
    pTimer->offScheduleNext = 0;
    pTimer->offNext         = 0;
    pTimer->offPrev         = 0;
    pTimer->pvUser          = NULL;
    pTimer->pCritSect       = NULL;
    pTimer->pszDesc         = pszDesc;

    /* insert into the list of created timers. */
    tmTimerLock(pVM);
    pTimer->pBigPrev        = NULL;
    pTimer->pBigNext        = pVM->tm.s.pCreated;
    pVM->tm.s.pCreated      = pTimer;
    if (pTimer->pBigNext)
        pTimer->pBigNext->pBigPrev = pTimer;
#ifdef VBOX_STRICT
    tmTimerQueuesSanityChecks(pVM, "tmR3TimerCreate");
#endif
    tmTimerUnlock(pVM);

    *ppTimer = pTimer;
    return VINF_SUCCESS;
}


/**
 * Creates a device timer.
 *
 * @returns VBox status.
 * @param   pVM             The VM to create the timer in.
 * @param   pDevIns         Device instance.
 * @param   enmClock        The clock to use on this timer.
 * @param   pfnCallback     Callback function.
 * @param   pvUser          The user argument to the callback.
 * @param   fFlags          Timer creation flags, see grp_tm_timer_flags.
 * @param   pszDesc         Pointer to description string which must stay around
 *                          until the timer is fully destroyed (i.e. a bit after TMTimerDestroy()).
 * @param   ppTimer         Where to store the timer on success.
 */
VMM_INT_DECL(int) TMR3TimerCreateDevice(PVM pVM, PPDMDEVINS pDevIns, TMCLOCK enmClock, PFNTMTIMERDEV pfnCallback, void *pvUser, uint32_t fFlags, const char *pszDesc, PPTMTIMERR3 ppTimer)
{
    AssertReturn(!(fFlags & ~(TMTIMER_FLAGS_NO_CRIT_SECT)), VERR_INVALID_PARAMETER);

    /*
     * Allocate and init stuff.
     */
    int rc = tmr3TimerCreate(pVM, enmClock, pszDesc, ppTimer);
    if (RT_SUCCESS(rc))
    {
        (*ppTimer)->enmType         = TMTIMERTYPE_DEV;
        (*ppTimer)->u.Dev.pfnTimer  = pfnCallback;
        (*ppTimer)->u.Dev.pDevIns   = pDevIns;
        (*ppTimer)->pvUser          = pvUser;
        if (fFlags & TMTIMER_FLAGS_DEFAULT_CRIT_SECT)
        {
            if (pDevIns->pCritSectR3)
                (*ppTimer)->pCritSect = pDevIns->pCritSectR3;
            else
                (*ppTimer)->pCritSect = IOMR3GetCritSect(pVM);
        }
        Log(("TM: Created device timer %p clock %d callback %p '%s'\n", (*ppTimer), enmClock, pfnCallback, pszDesc));
    }

    return rc;
}


/**
 * Creates a driver timer.
 *
 * @returns VBox status.
 * @param   pVM             The VM to create the timer in.
 * @param   pDrvIns         Driver instance.
 * @param   enmClock        The clock to use on this timer.
 * @param   pfnCallback     Callback function.
 * @param   pvUser          The user argument to the callback.
 * @param   fFlags          Timer creation flags, see grp_tm_timer_flags.
 * @param   pszDesc         Pointer to description string which must stay around
 *                          until the timer is fully destroyed (i.e. a bit after TMTimerDestroy()).
 * @param   ppTimer         Where to store the timer on success.
 */
VMM_INT_DECL(int) TMR3TimerCreateDriver(PVM pVM, PPDMDRVINS pDrvIns, TMCLOCK enmClock, PFNTMTIMERDRV pfnCallback, void *pvUser,
                                        uint32_t fFlags, const char *pszDesc, PPTMTIMERR3 ppTimer)
{
    AssertReturn(!(fFlags & ~(TMTIMER_FLAGS_NO_CRIT_SECT)), VERR_INVALID_PARAMETER);

    /*
     * Allocate and init stuff.
     */
    int rc = tmr3TimerCreate(pVM, enmClock, pszDesc, ppTimer);
    if (RT_SUCCESS(rc))
    {
        (*ppTimer)->enmType         = TMTIMERTYPE_DRV;
        (*ppTimer)->u.Drv.pfnTimer  = pfnCallback;
        (*ppTimer)->u.Drv.pDrvIns   = pDrvIns;
        (*ppTimer)->pvUser          = pvUser;
        Log(("TM: Created device timer %p clock %d callback %p '%s'\n", (*ppTimer), enmClock, pfnCallback, pszDesc));
    }

    return rc;
}


/**
 * Creates an internal timer.
 *
 * @returns VBox status.
 * @param   pVM             The VM to create the timer in.
 * @param   enmClock        The clock to use on this timer.
 * @param   pfnCallback     Callback function.
 * @param   pvUser          User argument to be passed to the callback.
 * @param   pszDesc         Pointer to description string which must stay around
 *                          until the timer is fully destroyed (i.e. a bit after TMTimerDestroy()).
 * @param   ppTimer         Where to store the timer on success.
 */
VMMR3DECL(int) TMR3TimerCreateInternal(PVM pVM, TMCLOCK enmClock, PFNTMTIMERINT pfnCallback, void *pvUser, const char *pszDesc, PPTMTIMERR3 ppTimer)
{
    /*
     * Allocate and init  stuff.
     */
    PTMTIMER pTimer;
    int rc = tmr3TimerCreate(pVM, enmClock, pszDesc, &pTimer);
    if (RT_SUCCESS(rc))
    {
        pTimer->enmType             = TMTIMERTYPE_INTERNAL;
        pTimer->u.Internal.pfnTimer = pfnCallback;
        pTimer->pvUser              = pvUser;
        *ppTimer = pTimer;
        Log(("TM: Created internal timer %p clock %d callback %p '%s'\n", pTimer, enmClock, pfnCallback, pszDesc));
    }

    return rc;
}

/**
 * Creates an external timer.
 *
 * @returns Timer handle on success.
 * @returns NULL on failure.
 * @param   pVM             The VM to create the timer in.
 * @param   enmClock        The clock to use on this timer.
 * @param   pfnCallback     Callback function.
 * @param   pvUser          User argument.
 * @param   pszDesc         Pointer to description string which must stay around
 *                          until the timer is fully destroyed (i.e. a bit after TMTimerDestroy()).
 */
VMMR3DECL(PTMTIMERR3) TMR3TimerCreateExternal(PVM pVM, TMCLOCK enmClock, PFNTMTIMEREXT pfnCallback, void *pvUser, const char *pszDesc)
{
    /*
     * Allocate and init stuff.
     */
    PTMTIMERR3 pTimer;
    int rc = tmr3TimerCreate(pVM, enmClock, pszDesc, &pTimer);
    if (RT_SUCCESS(rc))
    {
        pTimer->enmType             = TMTIMERTYPE_EXTERNAL;
        pTimer->u.External.pfnTimer = pfnCallback;
        pTimer->pvUser              = pvUser;
        Log(("TM: Created external timer %p clock %d callback %p '%s'\n", pTimer, enmClock, pfnCallback, pszDesc));
        return pTimer;
    }

    return NULL;
}


/**
 * Destroy a timer
 *
 * @returns VBox status.
 * @param   pTimer          Timer handle as returned by one of the create functions.
 */
VMMR3DECL(int) TMR3TimerDestroy(PTMTIMER pTimer)
{
    /*
     * Be extra careful here.
     */
    if (!pTimer)
        return VINF_SUCCESS;
    AssertPtr(pTimer);
    Assert((unsigned)pTimer->enmClock < (unsigned)TMCLOCK_MAX);

    PVM             pVM      = pTimer->CTX_SUFF(pVM);
    PTMTIMERQUEUE   pQueue   = &pVM->tm.s.CTX_SUFF(paTimerQueues)[pTimer->enmClock];
    bool            fActive  = false;
    bool            fPending = false;

    AssertMsg(   !pTimer->pCritSect
              || VMR3GetState(pVM) != VMSTATE_RUNNING
              || PDMCritSectIsOwner(pTimer->pCritSect), ("%s\n", pTimer->pszDesc));

    /*
     * The rest of the game happens behind the lock, just
     * like create does. All the work is done here.
     */
    tmTimerLock(pVM);
    for (int cRetries = 1000;; cRetries--)
    {
        /*
         * Change to the DESTROY state.
         */
        TMTIMERSTATE enmState    = pTimer->enmState;
        TMTIMERSTATE enmNewState = enmState;
        Log2(("TMTimerDestroy: %p:{.enmState=%s, .pszDesc='%s'} cRetries=%d\n",
              pTimer, tmTimerState(enmState), R3STRING(pTimer->pszDesc), cRetries));
        switch (enmState)
        {
            case TMTIMERSTATE_STOPPED:
            case TMTIMERSTATE_EXPIRED_DELIVER:
                break;

            case TMTIMERSTATE_ACTIVE:
                fActive     = true;
                break;

            case TMTIMERSTATE_PENDING_STOP:
            case TMTIMERSTATE_PENDING_STOP_SCHEDULE:
            case TMTIMERSTATE_PENDING_RESCHEDULE:
                fActive     = true;
                fPending    = true;
                break;

            case TMTIMERSTATE_PENDING_SCHEDULE:
                fPending    = true;
                break;

            /*
             * This shouldn't happen as the caller should make sure there are no races.
             */
            case TMTIMERSTATE_EXPIRED_GET_UNLINK:
            case TMTIMERSTATE_PENDING_SCHEDULE_SET_EXPIRE:
            case TMTIMERSTATE_PENDING_RESCHEDULE_SET_EXPIRE:
                AssertMsgFailed(("%p:.enmState=%s %s\n", pTimer, tmTimerState(enmState), pTimer->pszDesc));
                tmTimerUnlock(pVM);
                if (!RTThreadYield())
                    RTThreadSleep(1);
                AssertMsgReturn(cRetries > 0, ("Failed waiting for stable state. state=%d (%s)\n", pTimer->enmState, pTimer->pszDesc),
                                VERR_TM_UNSTABLE_STATE);
                tmTimerLock(pVM);
                continue;

            /*
             * Invalid states.
             */
            case TMTIMERSTATE_FREE:
            case TMTIMERSTATE_DESTROY:
                tmTimerUnlock(pVM);
                AssertLogRelMsgFailedReturn(("pTimer=%p %s\n", pTimer, tmTimerState(enmState)), VERR_TM_INVALID_STATE);

            default:
                AssertMsgFailed(("Unknown timer state %d (%s)\n", enmState, R3STRING(pTimer->pszDesc)));
                tmTimerUnlock(pVM);
                return VERR_TM_UNKNOWN_STATE;
        }

        /*
         * Try switch to the destroy state.
         * This should always succeed as the caller should make sure there are no race.
         */
        bool fRc;
        TM_TRY_SET_STATE(pTimer, TMTIMERSTATE_DESTROY, enmState, fRc);
        if (fRc)
            break;
        AssertMsgFailed(("%p:.enmState=%s %s\n", pTimer, tmTimerState(enmState), pTimer->pszDesc));
        tmTimerUnlock(pVM);
        AssertMsgReturn(cRetries > 0, ("Failed waiting for stable state. state=%d (%s)\n", pTimer->enmState, pTimer->pszDesc),
                        VERR_TM_UNSTABLE_STATE);
        tmTimerLock(pVM);
    }

    /*
     * Unlink from the active list.
     */
    if (fActive)
    {
        const PTMTIMER pPrev = TMTIMER_GET_PREV(pTimer);
        const PTMTIMER pNext = TMTIMER_GET_NEXT(pTimer);
        if (pPrev)
            TMTIMER_SET_NEXT(pPrev, pNext);
        else
        {
            TMTIMER_SET_HEAD(pQueue, pNext);
            pQueue->u64Expire = pNext ? pNext->u64Expire : INT64_MAX;
        }
        if (pNext)
            TMTIMER_SET_PREV(pNext, pPrev);
        pTimer->offNext = 0;
        pTimer->offPrev = 0;
    }

    /*
     * Unlink from the schedule list by running it.
     */
    if (fPending)
    {
        Log3(("TMR3TimerDestroy: tmTimerQueueSchedule\n"));
        STAM_PROFILE_START(&pVM->tm.s.CTX_SUFF_Z(StatScheduleOne), a);
        Assert(pQueue->offSchedule);
        tmTimerQueueSchedule(pVM, pQueue);
    }

    /*
     * Read to move the timer from the created list and onto the free list.
     */
    Assert(!pTimer->offNext); Assert(!pTimer->offPrev); Assert(!pTimer->offScheduleNext);

    /* unlink from created list */
    if (pTimer->pBigPrev)
        pTimer->pBigPrev->pBigNext = pTimer->pBigNext;
    else
        pVM->tm.s.pCreated         = pTimer->pBigNext;
    if (pTimer->pBigNext)
        pTimer->pBigNext->pBigPrev = pTimer->pBigPrev;
    pTimer->pBigNext = 0;
    pTimer->pBigPrev = 0;

    /* free */
    Log2(("TM: Inserting %p into the free list ahead of %p!\n", pTimer, pVM->tm.s.pFree));
    TM_SET_STATE(pTimer, TMTIMERSTATE_FREE);
    pTimer->pBigNext = pVM->tm.s.pFree;
    pVM->tm.s.pFree = pTimer;

#ifdef VBOX_STRICT
    tmTimerQueuesSanityChecks(pVM, "TMR3TimerDestroy");
#endif
    tmTimerUnlock(pVM);
    return VINF_SUCCESS;
}


/**
 * Destroy all timers owned by a device.
 *
 * @returns VBox status.
 * @param   pVM             VM handle.
 * @param   pDevIns         Device which timers should be destroyed.
 */
VMM_INT_DECL(int) TMR3TimerDestroyDevice(PVM pVM, PPDMDEVINS pDevIns)
{
    LogFlow(("TMR3TimerDestroyDevice: pDevIns=%p\n", pDevIns));
    if (!pDevIns)
        return VERR_INVALID_PARAMETER;

    tmTimerLock(pVM);
    PTMTIMER    pCur = pVM->tm.s.pCreated;
    while (pCur)
    {
        PTMTIMER pDestroy = pCur;
        pCur = pDestroy->pBigNext;
        if (    pDestroy->enmType == TMTIMERTYPE_DEV
            &&  pDestroy->u.Dev.pDevIns == pDevIns)
        {
            int rc = TMR3TimerDestroy(pDestroy);
            AssertRC(rc);
        }
    }
    tmTimerUnlock(pVM);

    LogFlow(("TMR3TimerDestroyDevice: returns VINF_SUCCESS\n"));
    return VINF_SUCCESS;
}


/**
 * Destroy all timers owned by a driver.
 *
 * @returns VBox status.
 * @param   pVM             VM handle.
 * @param   pDrvIns         Driver which timers should be destroyed.
 */
VMM_INT_DECL(int) TMR3TimerDestroyDriver(PVM pVM, PPDMDRVINS pDrvIns)
{
    LogFlow(("TMR3TimerDestroyDriver: pDrvIns=%p\n", pDrvIns));
    if (!pDrvIns)
        return VERR_INVALID_PARAMETER;

    tmTimerLock(pVM);
    PTMTIMER    pCur = pVM->tm.s.pCreated;
    while (pCur)
    {
        PTMTIMER pDestroy = pCur;
        pCur = pDestroy->pBigNext;
        if (    pDestroy->enmType == TMTIMERTYPE_DRV
            &&  pDestroy->u.Drv.pDrvIns == pDrvIns)
        {
            int rc = TMR3TimerDestroy(pDestroy);
            AssertRC(rc);
        }
    }
    tmTimerUnlock(pVM);

    LogFlow(("TMR3TimerDestroyDriver: returns VINF_SUCCESS\n"));
    return VINF_SUCCESS;
}


/**
 * Internal function for getting the clock time.
 *
 * @returns clock time.
 * @param   pVM         The VM handle.
 * @param   enmClock    The clock.
 */
DECLINLINE(uint64_t) tmClock(PVM pVM, TMCLOCK enmClock)
{
    switch (enmClock)
    {
        case TMCLOCK_VIRTUAL:       return TMVirtualGet(pVM);
        case TMCLOCK_VIRTUAL_SYNC:  return TMVirtualSyncGet(pVM);
        case TMCLOCK_REAL:          return TMRealGet(pVM);
        case TMCLOCK_TSC:           return TMCpuTickGet(&pVM->aCpus[0] /* just take VCPU 0 */);
        default:
            AssertMsgFailed(("enmClock=%d\n", enmClock));
            return ~(uint64_t)0;
    }
}


/**
 * Checks if the sync queue has one or more expired timers.
 *
 * @returns true / false.
 *
 * @param   pVM         The VM handle.
 * @param   enmClock    The queue.
 */
DECLINLINE(bool) tmR3HasExpiredTimer(PVM pVM, TMCLOCK enmClock)
{
    const uint64_t u64Expire = pVM->tm.s.CTX_SUFF(paTimerQueues)[enmClock].u64Expire;
    return u64Expire != INT64_MAX && u64Expire <= tmClock(pVM, enmClock);
}


/**
 * Checks for expired timers in all the queues.
 *
 * @returns true / false.
 * @param   pVM         The VM handle.
 */
DECLINLINE(bool) tmR3AnyExpiredTimers(PVM pVM)
{
    /*
     * Combine the time calculation for the first two since we're not on EMT
     * TMVirtualSyncGet only permits EMT.
     */
    uint64_t u64Now = TMVirtualGetNoCheck(pVM);
    if (pVM->tm.s.CTX_SUFF(paTimerQueues)[TMCLOCK_VIRTUAL].u64Expire <= u64Now)
        return true;
    u64Now = pVM->tm.s.fVirtualSyncTicking
           ? u64Now - pVM->tm.s.offVirtualSync
           : pVM->tm.s.u64VirtualSync;
    if (pVM->tm.s.CTX_SUFF(paTimerQueues)[TMCLOCK_VIRTUAL_SYNC].u64Expire <= u64Now)
        return true;

    /*
     * The remaining timers.
     */
    if (tmR3HasExpiredTimer(pVM, TMCLOCK_REAL))
        return true;
    if (tmR3HasExpiredTimer(pVM, TMCLOCK_TSC))
        return true;
    return false;
}


/**
 * Schedule timer callback.
 *
 * @param   pTimer      Timer handle.
 * @param   pvUser      VM handle.
 * @thread  Timer thread.
 *
 * @remark  We cannot do the scheduling and queues running from a timer handler
 *          since it's not executing in EMT, and even if it was it would be async
 *          and we wouldn't know the state of the affairs.
 *          So, we'll just raise the timer FF and force any REM execution to exit.
 */
static DECLCALLBACK(void) tmR3TimerCallback(PRTTIMER pTimer, void *pvUser, uint64_t /*iTick*/)
{
    PVM     pVM      = (PVM)pvUser;
    PVMCPU  pVCpuDst = &pVM->aCpus[pVM->tm.s.idTimerCpu];

    AssertCompile(TMCLOCK_MAX == 4);
#ifdef DEBUG_Sander /* very annoying, keep it private. */
    if (VMCPU_FF_ISSET(pVCpuDst, VMCPU_FF_TIMER))
        Log(("tmR3TimerCallback: timer event still pending!!\n"));
#endif
    if (    !VMCPU_FF_ISSET(pVCpuDst, VMCPU_FF_TIMER)
        &&  (   pVM->tm.s.paTimerQueuesR3[TMCLOCK_VIRTUAL_SYNC].offSchedule /** @todo FIXME - reconsider offSchedule as a reason for running the timer queues. */
            ||  pVM->tm.s.paTimerQueuesR3[TMCLOCK_VIRTUAL].offSchedule
            ||  pVM->tm.s.paTimerQueuesR3[TMCLOCK_REAL].offSchedule
            ||  pVM->tm.s.paTimerQueuesR3[TMCLOCK_TSC].offSchedule
            ||  tmR3AnyExpiredTimers(pVM)
            )
        && !VMCPU_FF_ISSET(pVCpuDst, VMCPU_FF_TIMER)
        && !pVM->tm.s.fRunningQueues
       )
    {
        Log5(("TM(%u): FF: 0 -> 1\n", __LINE__));
        VMCPU_FF_SET(pVCpuDst, VMCPU_FF_TIMER);
        REMR3NotifyTimerPending(pVM, pVCpuDst);
        VMR3NotifyCpuFFU(pVCpuDst->pUVCpu, VMNOTIFYFF_FLAGS_DONE_REM /** @todo | VMNOTIFYFF_FLAGS_POKE ?*/);
        STAM_COUNTER_INC(&pVM->tm.s.StatTimerCallbackSetFF);
    }
}


/**
 * Schedules and runs any pending timers.
 *
 * This is normally called from a forced action handler in EMT.
 *
 * @param   pVM             The VM to run the timers for.
 *
 * @thread  EMT (actually EMT0, but we fend off the others)
 */
VMMR3DECL(void) TMR3TimerQueuesDo(PVM pVM)
{
    /*
     * Only the dedicated timer EMT should do stuff here.
     * (fRunningQueues is only used as an indicator.)
     */
    Assert(pVM->tm.s.idTimerCpu < pVM->cCpus);
    PVMCPU pVCpuDst = &pVM->aCpus[pVM->tm.s.idTimerCpu];
    if (VMMGetCpu(pVM) != pVCpuDst)
    {
        Assert(pVM->cCpus > 1);
        return;
    }
    STAM_PROFILE_START(&pVM->tm.s.StatDoQueues, a);
    Log2(("TMR3TimerQueuesDo:\n"));
    Assert(!pVM->tm.s.fRunningQueues);
    ASMAtomicWriteBool(&pVM->tm.s.fRunningQueues, true);
    tmTimerLock(pVM);

    /*
     * Process the queues.
     */
    AssertCompile(TMCLOCK_MAX == 4);

    /* TMCLOCK_VIRTUAL_SYNC (see also TMR3VirtualSyncFF) */
    STAM_PROFILE_ADV_START(&pVM->tm.s.aStatDoQueues[TMCLOCK_VIRTUAL_SYNC], s1);
    tmVirtualSyncLock(pVM);
    ASMAtomicWriteBool(&pVM->tm.s.fRunningVirtualSyncQueue, true);
    VMCPU_FF_CLEAR(pVCpuDst, VMCPU_FF_TIMER);   /* Clear the FF once we started working for real. */

    if (pVM->tm.s.paTimerQueuesR3[TMCLOCK_VIRTUAL_SYNC].offSchedule)
        tmTimerQueueSchedule(pVM, &pVM->tm.s.paTimerQueuesR3[TMCLOCK_VIRTUAL_SYNC]);
    tmR3TimerQueueRunVirtualSync(pVM);
    if (pVM->tm.s.fVirtualSyncTicking) /** @todo move into tmR3TimerQueueRunVirtualSync - FIXME */
        VM_FF_CLEAR(pVM, VM_FF_TM_VIRTUAL_SYNC);

    ASMAtomicWriteBool(&pVM->tm.s.fRunningVirtualSyncQueue, false);
    tmVirtualSyncUnlock(pVM);
    STAM_PROFILE_ADV_STOP(&pVM->tm.s.aStatDoQueues[TMCLOCK_VIRTUAL_SYNC], s1);

    /* TMCLOCK_VIRTUAL */
    STAM_PROFILE_ADV_START(&pVM->tm.s.aStatDoQueues[TMCLOCK_VIRTUAL], s2);
    if (pVM->tm.s.paTimerQueuesR3[TMCLOCK_VIRTUAL].offSchedule)
        tmTimerQueueSchedule(pVM, &pVM->tm.s.paTimerQueuesR3[TMCLOCK_VIRTUAL]);
    tmR3TimerQueueRun(pVM, &pVM->tm.s.paTimerQueuesR3[TMCLOCK_VIRTUAL]);
    STAM_PROFILE_ADV_STOP(&pVM->tm.s.aStatDoQueues[TMCLOCK_VIRTUAL], s2);

    /* TMCLOCK_TSC */
    Assert(!pVM->tm.s.paTimerQueuesR3[TMCLOCK_TSC].offActive); /* not used */

    /* TMCLOCK_REAL */
    STAM_PROFILE_ADV_START(&pVM->tm.s.aStatDoQueues[TMCLOCK_REAL], s3);
    if (pVM->tm.s.paTimerQueuesR3[TMCLOCK_REAL].offSchedule)
        tmTimerQueueSchedule(pVM, &pVM->tm.s.paTimerQueuesR3[TMCLOCK_REAL]);
    tmR3TimerQueueRun(pVM, &pVM->tm.s.paTimerQueuesR3[TMCLOCK_REAL]);
    STAM_PROFILE_ADV_STOP(&pVM->tm.s.aStatDoQueues[TMCLOCK_REAL], s3);

#ifdef VBOX_STRICT
    /* check that we didn't screw up. */
    tmTimerQueuesSanityChecks(pVM, "TMR3TimerQueuesDo");
#endif

    /* done */
    Log2(("TMR3TimerQueuesDo: returns void\n"));
    ASMAtomicWriteBool(&pVM->tm.s.fRunningQueues, false);
    tmTimerUnlock(pVM);
    STAM_PROFILE_STOP(&pVM->tm.s.StatDoQueues, a);
}

//RT_C_DECLS_BEGIN
//int     iomLock(PVM pVM);
//void    iomUnlock(PVM pVM);
//RT_C_DECLS_END


/**
 * Schedules and runs any pending times in the specified queue.
 *
 * This is normally called from a forced action handler in EMT.
 *
 * @param   pVM             The VM to run the timers for.
 * @param   pQueue          The queue to run.
 */
static void tmR3TimerQueueRun(PVM pVM, PTMTIMERQUEUE pQueue)
{
    VM_ASSERT_EMT(pVM);

    /*
     * Run timers.
     *
     * We check the clock once and run all timers which are ACTIVE
     * and have an expire time less or equal to the time we read.
     *
     * N.B. A generic unlink must be applied since other threads
     *      are allowed to mess with any active timer at any time.
     *      However, we only allow EMT to handle EXPIRED_PENDING
     *      timers, thus enabling the timer handler function to
     *      arm the timer again.
     */
    PTMTIMER pNext = TMTIMER_GET_HEAD(pQueue);
    if (!pNext)
        return;
    const uint64_t u64Now = tmClock(pVM, pQueue->enmClock);
    while (pNext && pNext->u64Expire <= u64Now)
    {
        PTMTIMER        pTimer    = pNext;
        pNext = TMTIMER_GET_NEXT(pTimer);
        PPDMCRITSECT    pCritSect = pTimer->pCritSect;
        if (pCritSect)
            PDMCritSectEnter(pCritSect, VERR_INTERNAL_ERROR);
        Log2(("tmR3TimerQueueRun: %p:{.enmState=%s, .enmClock=%d, .enmType=%d, u64Expire=%llx (now=%llx) .pszDesc=%s}\n",
              pTimer, tmTimerState(pTimer->enmState), pTimer->enmClock, pTimer->enmType, pTimer->u64Expire, u64Now, pTimer->pszDesc));
        bool fRc;
        TM_TRY_SET_STATE(pTimer, TMTIMERSTATE_EXPIRED_GET_UNLINK, TMTIMERSTATE_ACTIVE, fRc);
        if (fRc)
        {
            Assert(!pTimer->offScheduleNext); /* this can trigger falsely */

            /* unlink */
            const PTMTIMER pPrev = TMTIMER_GET_PREV(pTimer);
            if (pPrev)
                TMTIMER_SET_NEXT(pPrev, pNext);
            else
            {
                TMTIMER_SET_HEAD(pQueue, pNext);
                pQueue->u64Expire = pNext ? pNext->u64Expire : INT64_MAX;
            }
            if (pNext)
                TMTIMER_SET_PREV(pNext, pPrev);
            pTimer->offNext = 0;
            pTimer->offPrev = 0;

            /* fire */
            TM_SET_STATE(pTimer, TMTIMERSTATE_EXPIRED_DELIVER);
            switch (pTimer->enmType)
            {
                case TMTIMERTYPE_DEV:       pTimer->u.Dev.pfnTimer(pTimer->u.Dev.pDevIns, pTimer, pTimer->pvUser); break;
                case TMTIMERTYPE_DRV:       pTimer->u.Drv.pfnTimer(pTimer->u.Drv.pDrvIns, pTimer, pTimer->pvUser); break;
                case TMTIMERTYPE_INTERNAL:  pTimer->u.Internal.pfnTimer(pVM, pTimer, pTimer->pvUser); break;
                case TMTIMERTYPE_EXTERNAL:  pTimer->u.External.pfnTimer(pTimer->pvUser); break;
                default:
                    AssertMsgFailed(("Invalid timer type %d (%s)\n", pTimer->enmType, pTimer->pszDesc));
                    break;
            }

            /* change the state if it wasn't changed already in the handler. */
            TM_TRY_SET_STATE(pTimer, TMTIMERSTATE_STOPPED, TMTIMERSTATE_EXPIRED_DELIVER, fRc);
            Log2(("tmR3TimerQueueRun: new state %s\n", tmTimerState(pTimer->enmState)));
        }
        if (pCritSect)
            PDMCritSectLeave(pCritSect);
    } /* run loop */
}


/**
 * Schedules and runs any pending times in the timer queue for the
 * synchronous virtual clock.
 *
 * This scheduling is a bit different from the other queues as it need
 * to implement the special requirements of the timer synchronous virtual
 * clock, thus this 2nd queue run function.
 *
 * @param   pVM             The VM to run the timers for.
 *
 * @remarks The caller must own both the TM/EMT and the Virtual Sync locks.
 */
static void tmR3TimerQueueRunVirtualSync(PVM pVM)
{
    PTMTIMERQUEUE const pQueue = &pVM->tm.s.paTimerQueuesR3[TMCLOCK_VIRTUAL_SYNC];
    VM_ASSERT_EMT(pVM);

    /*
     * Any timers?
     */
    PTMTIMER pNext = TMTIMER_GET_HEAD(pQueue);
    if (RT_UNLIKELY(!pNext))
    {
        Assert(pVM->tm.s.fVirtualSyncTicking || !pVM->tm.s.cVirtualTicking);
        return;
    }
    STAM_COUNTER_INC(&pVM->tm.s.StatVirtualSyncRun);

    /*
     * Calculate the time frame for which we will dispatch timers.
     *
     * We use a time frame ranging from the current sync time (which is most likely the
     * same as the head timer) and some configurable period (100000ns) up towards the
     * current virtual time. This period might also need to be restricted by the catch-up
     * rate so frequent calls to this function won't accelerate the time too much, however
     * this will be implemented at a later point if necessary.
     *
     * Without this frame we would 1) having to run timers much more frequently
     * and 2) lag behind at a steady rate.
     */
    const uint64_t  u64VirtualNow  = TMVirtualGetNoCheck(pVM);
    uint64_t const  offSyncGivenUp = pVM->tm.s.offVirtualSyncGivenUp;
    uint64_t        u64Now;
    if (!pVM->tm.s.fVirtualSyncTicking)
    {
        STAM_COUNTER_INC(&pVM->tm.s.StatVirtualSyncRunStoppedAlready);
        u64Now = pVM->tm.s.u64VirtualSync;
#ifdef DEBUG_bird
        Assert(u64Now <= pNext->u64Expire);
#endif
    }
    else
    {
        /* Calc 'now'. */
        bool        fStopCatchup   = false;
        bool        fUpdateStuff   = false;
        uint64_t    off            = pVM->tm.s.offVirtualSync;
        if (pVM->tm.s.fVirtualSyncCatchUp)
        {
            uint64_t u64Delta = u64VirtualNow - pVM->tm.s.u64VirtualSyncCatchUpPrev;
            if (RT_LIKELY(!(u64Delta >> 32)))
            {
                uint64_t u64Sub = ASMMultU64ByU32DivByU32(u64Delta, pVM->tm.s.u32VirtualSyncCatchUpPercentage, 100);
                if (off > u64Sub + offSyncGivenUp)
                {
                    off -= u64Sub;
                    Log4(("TM: %'RU64/-%'8RU64: sub %'RU64 [tmR3TimerQueueRunVirtualSync]\n", u64VirtualNow - off, off - offSyncGivenUp, u64Sub));
                }
                else
                {
                    STAM_PROFILE_ADV_STOP(&pVM->tm.s.StatVirtualSyncCatchup, c);
                    fStopCatchup = true;
                    off = offSyncGivenUp;
                }
                fUpdateStuff = true;
            }
        }
        u64Now = u64VirtualNow - off;

        /* Check if stopped by expired timer. */
        uint64_t u64Expire = pNext->u64Expire;
        if (u64Now >= pNext->u64Expire)
        {
            STAM_COUNTER_INC(&pVM->tm.s.StatVirtualSyncRunStop);
            u64Now = pNext->u64Expire;
            ASMAtomicWriteU64(&pVM->tm.s.u64VirtualSync, u64Now);
            ASMAtomicWriteBool(&pVM->tm.s.fVirtualSyncTicking, false);
            Log4(("TM: %'RU64/-%'8RU64: exp tmr [tmR3TimerQueueRunVirtualSync]\n", u64Now, u64VirtualNow - u64Now - offSyncGivenUp));
        }
        else if (fUpdateStuff)
        {
            ASMAtomicWriteU64(&pVM->tm.s.offVirtualSync, off);
            ASMAtomicWriteU64(&pVM->tm.s.u64VirtualSyncCatchUpPrev, u64VirtualNow);
            if (fStopCatchup)
            {
                ASMAtomicWriteBool(&pVM->tm.s.fVirtualSyncCatchUp, false);
                Log4(("TM: %'RU64/0: caught up [tmR3TimerQueueRunVirtualSync]\n", u64VirtualNow));
            }
        }
    }

    /* calc end of frame. */
    uint64_t u64Max = u64Now + pVM->tm.s.u32VirtualSyncScheduleSlack;
    if (u64Max > u64VirtualNow - offSyncGivenUp)
        u64Max = u64VirtualNow - offSyncGivenUp;

    /* assert sanity */
#ifdef DEBUG_bird
    Assert(u64Now <= u64VirtualNow - offSyncGivenUp);
    Assert(u64Max <= u64VirtualNow - offSyncGivenUp);
    Assert(u64Now <= u64Max);
    Assert(offSyncGivenUp == pVM->tm.s.offVirtualSyncGivenUp);
#endif

    /*
     * Process the expired timers moving the clock along as we progress.
     */
#ifdef DEBUG_bird
#ifdef VBOX_STRICT
    uint64_t u64Prev = u64Now; NOREF(u64Prev);
#endif
#endif
    while (pNext && pNext->u64Expire <= u64Max)
    {
        PTMTIMER        pTimer    = pNext;
        pNext = TMTIMER_GET_NEXT(pTimer);
        PPDMCRITSECT    pCritSect = pTimer->pCritSect;
        if (pCritSect)
            PDMCritSectEnter(pCritSect, VERR_INTERNAL_ERROR);
        Log2(("tmR3TimerQueueRun: %p:{.enmState=%s, .enmClock=%d, .enmType=%d, u64Expire=%llx (now=%llx) .pszDesc=%s}\n",
              pTimer, tmTimerState(pTimer->enmState), pTimer->enmClock, pTimer->enmType, pTimer->u64Expire, u64Now, pTimer->pszDesc));
        bool fRc;
        TM_TRY_SET_STATE(pTimer, TMTIMERSTATE_EXPIRED_GET_UNLINK, TMTIMERSTATE_ACTIVE, fRc);
        if (fRc)
        {
            /* unlink */
            const PTMTIMER pPrev = TMTIMER_GET_PREV(pTimer);
            if (pPrev)
                TMTIMER_SET_NEXT(pPrev, pNext);
            else
            {
                TMTIMER_SET_HEAD(pQueue, pNext);
                pQueue->u64Expire = pNext ? pNext->u64Expire : INT64_MAX;
            }
            if (pNext)
                TMTIMER_SET_PREV(pNext, pPrev);
            pTimer->offNext = 0;
            pTimer->offPrev = 0;

            /* advance the clock - don't permit timers to be out of order or armed in the 'past'. */
#ifdef DEBUG_bird
#ifdef VBOX_STRICT
            AssertMsg(pTimer->u64Expire >= u64Prev, ("%'RU64 < %'RU64 %s\n", pTimer->u64Expire, u64Prev, pTimer->pszDesc));
            u64Prev = pTimer->u64Expire;
#endif
#endif
            ASMAtomicWriteU64(&pVM->tm.s.u64VirtualSync, pTimer->u64Expire);
            ASMAtomicWriteBool(&pVM->tm.s.fVirtualSyncTicking, false);

            /* fire */
            TM_SET_STATE(pTimer, TMTIMERSTATE_EXPIRED_DELIVER);
            switch (pTimer->enmType)
            {
                case TMTIMERTYPE_DEV:       pTimer->u.Dev.pfnTimer(pTimer->u.Dev.pDevIns, pTimer, pTimer->pvUser); break;
                case TMTIMERTYPE_DRV:       pTimer->u.Drv.pfnTimer(pTimer->u.Drv.pDrvIns, pTimer, pTimer->pvUser); break;
                case TMTIMERTYPE_INTERNAL:  pTimer->u.Internal.pfnTimer(pVM, pTimer, pTimer->pvUser); break;
                case TMTIMERTYPE_EXTERNAL:  pTimer->u.External.pfnTimer(pTimer->pvUser); break;
                default:
                    AssertMsgFailed(("Invalid timer type %d (%s)\n", pTimer->enmType, pTimer->pszDesc));
                    break;
            }

            /* Change the state if it wasn't changed already in the handler.
               Reset the Hz hint too since this is the same as TMTimerStop. */
            TM_TRY_SET_STATE(pTimer, TMTIMERSTATE_STOPPED, TMTIMERSTATE_EXPIRED_DELIVER, fRc);
            if (fRc && pTimer->uHzHint)
            {
                if (pTimer->uHzHint >= pVM->tm.s.uMaxHzHint)
                    ASMAtomicWriteBool(&pVM->tm.s.fHzHintNeedsUpdating, true);
                pTimer->uHzHint = 0;
            }
            Log2(("tmR3TimerQueueRun: new state %s\n", tmTimerState(pTimer->enmState)));
        }
        if (pCritSect)
            PDMCritSectLeave(pCritSect);
    } /* run loop */

    /*
     * Restart the clock if it was stopped to serve any timers,
     * and start/adjust catch-up if necessary.
     */
    if (    !pVM->tm.s.fVirtualSyncTicking
        &&  pVM->tm.s.cVirtualTicking)
    {
        STAM_COUNTER_INC(&pVM->tm.s.StatVirtualSyncRunRestart);

        /* calc the slack we've handed out. */
        const uint64_t u64VirtualNow2 = TMVirtualGetNoCheck(pVM);
        Assert(u64VirtualNow2 >= u64VirtualNow);
#ifdef DEBUG_bird
        AssertMsg(pVM->tm.s.u64VirtualSync >= u64Now, ("%'RU64 < %'RU64\n", pVM->tm.s.u64VirtualSync, u64Now));
#endif
        const uint64_t offSlack = pVM->tm.s.u64VirtualSync - u64Now;
        STAM_STATS({
            if (offSlack)
            {
                PSTAMPROFILE p = &pVM->tm.s.StatVirtualSyncRunSlack;
                p->cPeriods++;
                p->cTicks += offSlack;
                if (p->cTicksMax < offSlack) p->cTicksMax = offSlack;
                if (p->cTicksMin > offSlack) p->cTicksMin = offSlack;
            }
        });

        /* Let the time run a little bit while we were busy running timers(?). */
        uint64_t u64Elapsed;
#define MAX_ELAPSED 30000U /* ns */
        if (offSlack > MAX_ELAPSED)
            u64Elapsed = 0;
        else
        {
            u64Elapsed = u64VirtualNow2 - u64VirtualNow;
            if (u64Elapsed > MAX_ELAPSED)
                u64Elapsed = MAX_ELAPSED;
            u64Elapsed = u64Elapsed > offSlack ? u64Elapsed - offSlack : 0;
        }
#undef MAX_ELAPSED

        /* Calc the current offset. */
        uint64_t offNew = u64VirtualNow2 - pVM->tm.s.u64VirtualSync - u64Elapsed;
        Assert(!(offNew & RT_BIT_64(63)));
        uint64_t offLag = offNew - pVM->tm.s.offVirtualSyncGivenUp;
        Assert(!(offLag & RT_BIT_64(63)));

        /*
         * Deal with starting, adjusting and stopping catchup.
         */
        if (pVM->tm.s.fVirtualSyncCatchUp)
        {
            if (offLag <= pVM->tm.s.u64VirtualSyncCatchUpStopThreshold)
            {
                /* stop */
                STAM_PROFILE_ADV_STOP(&pVM->tm.s.StatVirtualSyncCatchup, c);
                ASMAtomicWriteBool(&pVM->tm.s.fVirtualSyncCatchUp, false);
                Log4(("TM: %'RU64/-%'8RU64: caught up [pt]\n", u64VirtualNow2 - offNew, offLag));
            }
            else if (offLag <= pVM->tm.s.u64VirtualSyncCatchUpGiveUpThreshold)
            {
                /* adjust */
                unsigned i = 0;
                while (     i + 1 < RT_ELEMENTS(pVM->tm.s.aVirtualSyncCatchUpPeriods)
                       &&   offLag >= pVM->tm.s.aVirtualSyncCatchUpPeriods[i + 1].u64Start)
                    i++;
                if (pVM->tm.s.u32VirtualSyncCatchUpPercentage < pVM->tm.s.aVirtualSyncCatchUpPeriods[i].u32Percentage)
                {
                    STAM_COUNTER_INC(&pVM->tm.s.aStatVirtualSyncCatchupAdjust[i]);
                    ASMAtomicWriteU32(&pVM->tm.s.u32VirtualSyncCatchUpPercentage, pVM->tm.s.aVirtualSyncCatchUpPeriods[i].u32Percentage);
                    Log4(("TM: %'RU64/%'8RU64: adj %u%%\n", u64VirtualNow2 - offNew, offLag, pVM->tm.s.u32VirtualSyncCatchUpPercentage));
                }
                pVM->tm.s.u64VirtualSyncCatchUpPrev = u64VirtualNow2;
            }
            else
            {
                /* give up */
                STAM_COUNTER_INC(&pVM->tm.s.StatVirtualSyncGiveUp);
                STAM_PROFILE_ADV_STOP(&pVM->tm.s.StatVirtualSyncCatchup, c);
                ASMAtomicWriteU64((uint64_t volatile *)&pVM->tm.s.offVirtualSyncGivenUp, offNew);
                ASMAtomicWriteBool(&pVM->tm.s.fVirtualSyncCatchUp, false);
                Log4(("TM: %'RU64/%'8RU64: give up %u%%\n", u64VirtualNow2 - offNew, offLag, pVM->tm.s.u32VirtualSyncCatchUpPercentage));
                LogRel(("TM: Giving up catch-up attempt at a %'RU64 ns lag; new total: %'RU64 ns\n", offLag, offNew));
            }
        }
        else if (offLag >= pVM->tm.s.aVirtualSyncCatchUpPeriods[0].u64Start)
        {
            if (offLag <= pVM->tm.s.u64VirtualSyncCatchUpGiveUpThreshold)
            {
                /* start */
                STAM_PROFILE_ADV_START(&pVM->tm.s.StatVirtualSyncCatchup, c);
                unsigned i = 0;
                while (     i + 1 < RT_ELEMENTS(pVM->tm.s.aVirtualSyncCatchUpPeriods)
                       &&   offLag >= pVM->tm.s.aVirtualSyncCatchUpPeriods[i + 1].u64Start)
                    i++;
                STAM_COUNTER_INC(&pVM->tm.s.aStatVirtualSyncCatchupInitial[i]);
                ASMAtomicWriteU32(&pVM->tm.s.u32VirtualSyncCatchUpPercentage, pVM->tm.s.aVirtualSyncCatchUpPeriods[i].u32Percentage);
                ASMAtomicWriteBool(&pVM->tm.s.fVirtualSyncCatchUp, true);
                Log4(("TM: %'RU64/%'8RU64: catch-up %u%%\n", u64VirtualNow2 - offNew, offLag, pVM->tm.s.u32VirtualSyncCatchUpPercentage));
            }
            else
            {
                /* don't bother */
                STAM_COUNTER_INC(&pVM->tm.s.StatVirtualSyncGiveUpBeforeStarting);
                ASMAtomicWriteU64((uint64_t volatile *)&pVM->tm.s.offVirtualSyncGivenUp, offNew);
                Log4(("TM: %'RU64/%'8RU64: give up\n", u64VirtualNow2 - offNew, offLag));
                LogRel(("TM: Not bothering to attempt catching up a %'RU64 ns lag; new total: %'RU64\n", offLag, offNew));
            }
        }

        /*
         * Update the offset and restart the clock.
         */
        Assert(!(offNew & RT_BIT_64(63)));
        ASMAtomicWriteU64(&pVM->tm.s.offVirtualSync, offNew);
        ASMAtomicWriteBool(&pVM->tm.s.fVirtualSyncTicking, true);
    }
}


/**
 * Deals with stopped Virtual Sync clock.
 *
 * This is called by the forced action flag handling code in EM when it
 * encounters the VM_FF_TM_VIRTUAL_SYNC flag. It is called by all VCPUs and they
 * will block on the VirtualSyncLock until the pending timers has been executed
 * and the clock restarted.
 *
 * @param   pVM             The VM to run the timers for.
 * @param   pVCpu           The virtual CPU we're running at.
 *
 * @thread  EMTs
 */
VMM_INT_DECL(void) TMR3VirtualSyncFF(PVM pVM, PVMCPU pVCpu)
{
    Log2(("TMR3VirtualSyncFF:\n"));

    /*
     * The EMT doing the timers is diverted to them.
     */
    if (pVCpu->idCpu == pVM->tm.s.idTimerCpu)
        TMR3TimerQueuesDo(pVM);
    /*
     * The other EMTs will block on the virtual sync lock and the first owner
     * will run the queue and thus restarting the clock.
     *
     * Note! This is very suboptimal code wrt to resuming execution when there
     *       are more than two Virtual CPUs, since they will all have to enter
     *       the critical section one by one. But it's a very simple solution
     *       which will have to do the job for now.
     */
    else
    {
        STAM_PROFILE_START(&pVM->tm.s.StatVirtualSyncFF, a);
        tmVirtualSyncLock(pVM);
        if (pVM->tm.s.fVirtualSyncTicking)
        {
            STAM_PROFILE_STOP(&pVM->tm.s.StatVirtualSyncFF, a); /* before the unlock! */
            tmVirtualSyncUnlock(pVM);
            Log2(("TMR3VirtualSyncFF: ticking\n"));
        }
        else
        {
            tmVirtualSyncUnlock(pVM);

            /* try run it. */
            tmTimerLock(pVM);
            tmVirtualSyncLock(pVM);
            if (pVM->tm.s.fVirtualSyncTicking)
                Log2(("TMR3VirtualSyncFF: ticking (2)\n"));
            else
            {
                ASMAtomicWriteBool(&pVM->tm.s.fRunningVirtualSyncQueue, true);
                Log2(("TMR3VirtualSyncFF: running queue\n"));

                if (pVM->tm.s.paTimerQueuesR3[TMCLOCK_VIRTUAL_SYNC].offSchedule)
                    tmTimerQueueSchedule(pVM, &pVM->tm.s.paTimerQueuesR3[TMCLOCK_VIRTUAL_SYNC]);
                tmR3TimerQueueRunVirtualSync(pVM);
                if (pVM->tm.s.fVirtualSyncTicking) /** @todo move into tmR3TimerQueueRunVirtualSync - FIXME */
                    VM_FF_CLEAR(pVM, VM_FF_TM_VIRTUAL_SYNC);

                ASMAtomicWriteBool(&pVM->tm.s.fRunningVirtualSyncQueue, false);
            }
            STAM_PROFILE_STOP(&pVM->tm.s.StatVirtualSyncFF, a); /* before the unlock! */
            tmVirtualSyncUnlock(pVM);
            tmTimerUnlock(pVM);
        }
    }
}


/** @name Saved state values
 * @{ */
#define TMTIMERSTATE_SAVED_PENDING_STOP         4
#define TMTIMERSTATE_SAVED_PENDING_SCHEDULE     7
/** @}  */


/**
 * Saves the state of a timer to a saved state.
 *
 * @returns VBox status.
 * @param   pTimer          Timer to save.
 * @param   pSSM            Save State Manager handle.
 */
VMMR3DECL(int) TMR3TimerSave(PTMTIMERR3 pTimer, PSSMHANDLE pSSM)
{
    LogFlow(("TMR3TimerSave: %p:{enmState=%s, .pszDesc={%s}} pSSM=%p\n", pTimer, tmTimerState(pTimer->enmState), pTimer->pszDesc, pSSM));
    switch (pTimer->enmState)
    {
        case TMTIMERSTATE_STOPPED:
        case TMTIMERSTATE_PENDING_STOP:
        case TMTIMERSTATE_PENDING_STOP_SCHEDULE:
            return SSMR3PutU8(pSSM, TMTIMERSTATE_SAVED_PENDING_STOP);

        case TMTIMERSTATE_PENDING_SCHEDULE_SET_EXPIRE:
        case TMTIMERSTATE_PENDING_RESCHEDULE_SET_EXPIRE:
            AssertMsgFailed(("u64Expire is being updated! (%s)\n", pTimer->pszDesc));
            if (!RTThreadYield())
                RTThreadSleep(1);
            /* fall thru */
        case TMTIMERSTATE_ACTIVE:
        case TMTIMERSTATE_PENDING_SCHEDULE:
        case TMTIMERSTATE_PENDING_RESCHEDULE:
            SSMR3PutU8(pSSM, TMTIMERSTATE_SAVED_PENDING_SCHEDULE);
            return SSMR3PutU64(pSSM, pTimer->u64Expire);

        case TMTIMERSTATE_EXPIRED_GET_UNLINK:
        case TMTIMERSTATE_EXPIRED_DELIVER:
        case TMTIMERSTATE_DESTROY:
        case TMTIMERSTATE_FREE:
            AssertMsgFailed(("Invalid timer state %d %s (%s)\n", pTimer->enmState, tmTimerState(pTimer->enmState), pTimer->pszDesc));
            return SSMR3HandleSetStatus(pSSM, VERR_TM_INVALID_STATE);
    }

    AssertMsgFailed(("Unknown timer state %d (%s)\n", pTimer->enmState, pTimer->pszDesc));
    return SSMR3HandleSetStatus(pSSM, VERR_TM_UNKNOWN_STATE);
}


/**
 * Loads the state of a timer from a saved state.
 *
 * @returns VBox status.
 * @param   pTimer          Timer to restore.
 * @param   pSSM            Save State Manager handle.
 */
VMMR3DECL(int) TMR3TimerLoad(PTMTIMERR3 pTimer, PSSMHANDLE pSSM)
{
    Assert(pTimer); Assert(pSSM); VM_ASSERT_EMT(pTimer->pVMR3);
    LogFlow(("TMR3TimerLoad: %p:{enmState=%s, .pszDesc={%s}} pSSM=%p\n", pTimer, tmTimerState(pTimer->enmState), pTimer->pszDesc, pSSM));

    /*
     * Load the state and validate it.
     */
    uint8_t u8State;
    int rc = SSMR3GetU8(pSSM, &u8State);
    if (RT_FAILURE(rc))
        return rc;
#if 1 /* Workaround for accidental state shift in r47786 (2009-05-26 19:12:12). */  /** @todo remove this in a few weeks! */
    if (    u8State == TMTIMERSTATE_SAVED_PENDING_STOP + 1
        ||  u8State == TMTIMERSTATE_SAVED_PENDING_SCHEDULE + 1)
        u8State--;
#endif
    if (    u8State != TMTIMERSTATE_SAVED_PENDING_STOP
        &&  u8State != TMTIMERSTATE_SAVED_PENDING_SCHEDULE)
    {
        AssertLogRelMsgFailed(("u8State=%d\n", u8State));
        return SSMR3HandleSetStatus(pSSM, VERR_TM_LOAD_STATE);
    }

    /* Enter the critical section to make TMTimerSet/Stop happy. */
    PPDMCRITSECT pCritSect = pTimer->pCritSect;
    if (pCritSect)
        PDMCritSectEnter(pCritSect, VERR_INTERNAL_ERROR);

    if (u8State == TMTIMERSTATE_SAVED_PENDING_SCHEDULE)
    {
        /*
         * Load the expire time.
         */
        uint64_t u64Expire;
        rc = SSMR3GetU64(pSSM, &u64Expire);
        if (RT_FAILURE(rc))
            return rc;

        /*
         * Set it.
         */
        Log(("u8State=%d u64Expire=%llu\n", u8State, u64Expire));
        rc = TMTimerSet(pTimer, u64Expire);
    }
    else
    {
        /*
         * Stop it.
         */
        Log(("u8State=%d\n", u8State));
        rc = TMTimerStop(pTimer);
    }

    if (pCritSect)
        PDMCritSectLeave(pCritSect);

    /*
     * On failure set SSM status.
     */
    if (RT_FAILURE(rc))
        rc = SSMR3HandleSetStatus(pSSM, rc);
    return rc;
}


/**
 * Associates a critical section with a timer.
 *
 * The critical section will be entered prior to doing the timer call back, thus
 * avoiding potential races between the timer thread and other threads trying to
 * stop or adjust the timer expiration while it's being delivered. The timer
 * thread will leave the critical section when the timer callback returns.
 *
 * In strict builds, ownership of the critical section will be asserted by
 * TMTimerSet, TMTimerStop, TMTimerGetExpire and TMTimerDestroy (when called at
 * runtime).
 *
 * @retval  VINF_SUCCESS on success.
 * @retval  VERR_INVALID_HANDLE if the timer handle is NULL or invalid
 *          (asserted).
 * @retval  VERR_INVALID_PARAMETER if pCritSect is NULL or has an invalid magic
 *          (asserted).
 * @retval  VERR_ALREADY_EXISTS if a critical section was already associated
 *          with the timer (asserted).
 * @retval  VERR_INVALID_STATE if the timer isn't stopped.
 *
 * @param   pTimer          The timer handle.
 * @param   pCritSect       The critical section. The caller must make sure this
 *                          is around for the life time of the timer.
 *
 * @thread  Any, but the caller is responsible for making sure the timer is not
 *          active.
 */
VMMR3DECL(int) TMR3TimerSetCritSect(PTMTIMERR3 pTimer, PPDMCRITSECT pCritSect)
{
    AssertPtrReturn(pTimer, VERR_INVALID_HANDLE);
    AssertPtrReturn(pCritSect, VERR_INVALID_PARAMETER);
    const char *pszName = PDMR3CritSectName(pCritSect); /* exploited for validation */
    AssertReturn(pszName, VERR_INVALID_PARAMETER);
    AssertReturn(!pTimer->pCritSect, VERR_ALREADY_EXISTS);
    AssertReturn(pTimer->enmState == TMTIMERSTATE_STOPPED, VERR_INVALID_STATE);
    LogFlow(("pTimer=%p (%s) pCritSect=%p (%s)\n", pTimer, pTimer->pszDesc, pCritSect, pszName));

    pTimer->pCritSect = pCritSect;
    return VINF_SUCCESS;
}


/**
 * Get the real world UTC time adjusted for VM lag.
 *
 * @returns pTime.
 * @param   pVM             The VM instance.
 * @param   pTime           Where to store the time.
 */
VMM_INT_DECL(PRTTIMESPEC) TMR3UtcNow(PVM pVM, PRTTIMESPEC pTime)
{
    RTTimeNow(pTime);
    RTTimeSpecSubNano(pTime, ASMAtomicReadU64(&pVM->tm.s.offVirtualSync) - ASMAtomicReadU64((uint64_t volatile *)&pVM->tm.s.offVirtualSyncGivenUp));
    RTTimeSpecAddNano(pTime, pVM->tm.s.offUTC);
    return pTime;
}


/**
 * Pauses all clocks except TMCLOCK_REAL.
 *
 * @returns VBox status code, all errors are asserted.
 * @param   pVM         The VM handle.
 * @param   pVCpu       The virtual CPU handle.
 * @thread  EMT corresponding to the virtual CPU handle.
 */
VMMR3DECL(int) TMR3NotifySuspend(PVM pVM, PVMCPU pVCpu)
{
    VMCPU_ASSERT_EMT(pVCpu);

    /*
     * The shared virtual clock (includes virtual sync which is tied to it).
     */
    tmTimerLock(pVM);                           /* Paranoia: Exploiting the timer lock here. */
    int rc = tmVirtualPauseLocked(pVM);
    tmTimerUnlock(pVM);
    if (RT_FAILURE(rc))
        return rc;

    /*
     * Pause the TSC last since it is normally linked to the virtual
     * sync clock, so the above code may actually stop both clock.
     */
    rc = tmCpuTickPause(pVM, pVCpu);
    if (RT_FAILURE(rc))
        return rc;

#ifndef VBOX_WITHOUT_NS_ACCOUNTING
    /*
     * Update cNsTotal.
     */
    uint32_t uGen = ASMAtomicIncU32(&pVCpu->tm.s.uTimesGen); Assert(uGen & 1);
    pVCpu->tm.s.cNsTotal = RTTimeNanoTS() - pVCpu->tm.s.u64NsTsStartTotal;
    pVCpu->tm.s.cNsOther = pVCpu->tm.s.cNsTotal - pVCpu->tm.s.cNsExecuting - pVCpu->tm.s.cNsHalted;
    ASMAtomicWriteU32(&pVCpu->tm.s.uTimesGen, (uGen | 1) + 1);
#endif

    return VINF_SUCCESS;
}


/**
 * Resumes all clocks except TMCLOCK_REAL.
 *
 * @returns VBox status code, all errors are asserted.
 * @param   pVM         The VM handle.
 * @param   pVCpu       The virtual CPU handle.
 * @thread  EMT corresponding to the virtual CPU handle.
 */
VMMR3DECL(int) TMR3NotifyResume(PVM pVM, PVMCPU pVCpu)
{
    VMCPU_ASSERT_EMT(pVCpu);
    int rc;

#ifndef VBOX_WITHOUT_NS_ACCOUNTING
    /*
     * Set u64NsTsStartTotal.  There is no need to back this out if either of
     * the two calls below fail.
     */
    pVCpu->tm.s.u64NsTsStartTotal = RTTimeNanoTS() - pVCpu->tm.s.cNsTotal;
#endif

    /*
     * Resume the TSC first since it is normally linked to the virtual sync
     * clock, so it may actually not be resumed until we've executed the code
     * below.
     */
    if (!pVM->tm.s.fTSCTiedToExecution)
    {
        rc = tmCpuTickResume(pVM, pVCpu);
        if (RT_FAILURE(rc))
            return rc;
    }

    /*
     * The shared virtual clock (includes virtual sync which is tied to it).
     */
    tmTimerLock(pVM);                           /* Paranoia: Exploiting the timer lock here. */
    rc = tmVirtualResumeLocked(pVM);
    tmTimerUnlock(pVM);

    return rc;
}


/**
 * Sets the warp drive percent of the virtual time.
 *
 * @returns VBox status code.
 * @param   pVM         The VM handle.
 * @param   u32Percent  The new percentage. 100 means normal operation.
 *
 * @todo    Move to Ring-3!
 */
VMMDECL(int) TMR3SetWarpDrive(PVM pVM, uint32_t u32Percent)
{
    return VMR3ReqCallWait(pVM, VMCPUID_ANY, (PFNRT)tmR3SetWarpDrive, 2, pVM, u32Percent);
}


/**
 * EMT worker for TMR3SetWarpDrive.
 *
 * @returns VBox status code.
 * @param   pVM         The VM handle.
 * @param   u32Percent  See TMR3SetWarpDrive().
 * @internal
 */
static DECLCALLBACK(int) tmR3SetWarpDrive(PVM pVM, uint32_t u32Percent)
{
    PVMCPU pVCpu = VMMGetCpu(pVM);

    /*
     * Validate it.
     */
    AssertMsgReturn(u32Percent >= 2 && u32Percent <= 20000,
                    ("%RX32 is not between 2 and 20000 (inclusive).\n", u32Percent),
                    VERR_INVALID_PARAMETER);

/** @todo This isn't a feature specific to virtual time, move the variables to
 * TM level and make it affect TMR3UCTNow as well! */

    /*
     * If the time is running we'll have to pause it before we can change
     * the warp drive settings.
     */
    tmTimerLock(pVM);                           /* Paranoia: Exploiting the timer lock here. */
    bool fPaused = !!pVM->tm.s.cVirtualTicking;
    if (fPaused) /** @todo this isn't really working, but wtf. */
        TMR3NotifySuspend(pVM, pVCpu);

    pVM->tm.s.u32VirtualWarpDrivePercentage = u32Percent;
    pVM->tm.s.fVirtualWarpDrive = u32Percent != 100;
    LogRel(("TM: u32VirtualWarpDrivePercentage=%RI32 fVirtualWarpDrive=%RTbool\n",
            pVM->tm.s.u32VirtualWarpDrivePercentage, pVM->tm.s.fVirtualWarpDrive));

    if (fPaused)
        TMR3NotifyResume(pVM, pVCpu);
    tmTimerUnlock(pVM);
    return VINF_SUCCESS;
}


/**
 * Gets the performance information for one virtual CPU as seen by the VMM.
 *
 * The returned times covers the period where the VM is running and will be
 * reset when restoring a previous VM state (at least for the time being).
 *
 * @retval  VINF_SUCCESS on success.
 * @retval  VERR_NOT_IMPLEMENTED if not compiled in.
 * @retval  VERR_INVALID_STATE if the VM handle is bad.
 * @retval  VERR_INVALID_PARAMETER if idCpu is out of range.
 *
 * @param   pVM             The VM handle.
 * @param   idCpu           The ID of the virtual CPU which times to get.
 * @param   pcNsTotal       Where to store the total run time (nano seconds) of
 *                          the CPU, i.e. the sum of the three other returns.
 *                          Optional.
 * @param   pcNsExecuting   Where to store the time (nano seconds) spent
 *                          executing guest code.  Optional.
 * @param   pcNsHalted      Where to store the time (nano seconds) spent
 *                          halted.  Optional
 * @param   pcNsOther       Where to store the time (nano seconds) spent
 *                          preempted by the host scheduler, on virtualization
 *                          overhead and on other tasks.
 */
VMMR3DECL(int) TMR3GetCpuLoadTimes(PVM pVM, VMCPUID idCpu, uint64_t *pcNsTotal, uint64_t *pcNsExecuting,
                                   uint64_t *pcNsHalted, uint64_t *pcNsOther)
{
    VM_ASSERT_VALID_EXT_RETURN(pVM, VERR_INVALID_STATE);
    AssertReturn(idCpu < pVM->cCpus, VERR_INVALID_PARAMETER);

#ifndef VBOX_WITHOUT_NS_ACCOUNTING
    /*
     * Get a stable result set.
     * This should be way quicker than an EMT request.
     */
    PVMCPU      pVCpu        = &pVM->aCpus[idCpu];
    uint32_t    uTimesGen    = ASMAtomicReadU32(&pVCpu->tm.s.uTimesGen);
    uint64_t    cNsTotal     = pVCpu->tm.s.cNsTotal;
    uint64_t    cNsExecuting = pVCpu->tm.s.cNsExecuting;
    uint64_t    cNsHalted    = pVCpu->tm.s.cNsHalted;
    uint64_t    cNsOther     = pVCpu->tm.s.cNsOther;
    while (   (uTimesGen & 1) /* update in progress */
           || uTimesGen != ASMAtomicReadU32(&pVCpu->tm.s.uTimesGen))
    {
        RTThreadYield();
        uTimesGen    = ASMAtomicReadU32(&pVCpu->tm.s.uTimesGen);
        cNsTotal     = pVCpu->tm.s.cNsTotal;
        cNsExecuting = pVCpu->tm.s.cNsExecuting;
        cNsHalted    = pVCpu->tm.s.cNsHalted;
        cNsOther     = pVCpu->tm.s.cNsOther;
    }

    /*
     * Fill in the return values.
     */
    if (pcNsTotal)
        *pcNsTotal = cNsTotal;
    if (pcNsExecuting)
        *pcNsExecuting = cNsExecuting;
    if (pcNsHalted)
        *pcNsHalted = cNsHalted;
    if (pcNsOther)
        *pcNsOther = cNsOther;

    return VINF_SUCCESS;

#else
    return VERR_NOT_IMPLEMENTED;
#endif
}

#ifndef VBOX_WITHOUT_NS_ACCOUNTING

/**
 * Helper for tmR3CpuLoadTimer.
 * @returns
 * @param   pState              The state to update.
 * @param   cNsTotalDelta       Total time.
 * @param   cNsExecutingDelta   Time executing.
 * @param   cNsHaltedDelta      Time halted.
 */
DECLINLINE(void) tmR3CpuLoadTimerMakeUpdate(PTMCPULOADSTATE pState,
                                            uint64_t cNsTotal,
                                            uint64_t cNsExecuting,
                                            uint64_t cNsHalted)
{
    /* Calc deltas */
    uint64_t cNsTotalDelta      = cNsTotal     - pState->cNsPrevTotal;
    pState->cNsPrevTotal        = cNsTotal;

    uint64_t cNsExecutingDelta  = cNsExecuting - pState->cNsPrevExecuting;
    pState->cNsPrevExecuting    = cNsExecuting;

    uint64_t cNsHaltedDelta     = cNsHalted    - pState->cNsPrevHalted;
    pState->cNsPrevHalted       = cNsHalted;

    /* Calc pcts. */
    if (!cNsTotalDelta)
    {
        pState->cPctExecuting   = 0;
        pState->cPctHalted      = 100;
        pState->cPctOther       = 0;
    }
    else if (cNsTotalDelta < UINT64_MAX / 4)
    {
        pState->cPctExecuting   = (uint8_t)(cNsExecutingDelta    * 100 / cNsTotalDelta);
        pState->cPctHalted      = (uint8_t)(cNsHaltedDelta       * 100 / cNsTotalDelta);
        pState->cPctOther       = (uint8_t)((cNsTotalDelta - cNsExecutingDelta - cNsHaltedDelta) * 100 / cNsTotalDelta);
    }
    else
    {
        pState->cPctExecuting   = 0;
        pState->cPctHalted      = 100;
        pState->cPctOther       = 0;
    }
}


/**
 * Timer callback that calculates the CPU load since the last time it was
 * called.
 *
 * @param   pVM                 The VM handle.
 * @param   pTimer              The timer.
 * @param   pvUser              NULL, unused.
 */
static DECLCALLBACK(void) tmR3CpuLoadTimer(PVM pVM, PTMTIMER pTimer, void *pvUser)
{
    /*
     * Re-arm the timer first.
     */
    int rc = TMTimerSetMillies(pTimer, 1000);
    AssertLogRelRC(rc);
    NOREF(pvUser);

    /*
     * Update the values for each CPU.
     */
    uint64_t cNsTotalAll       = 0;
    uint64_t cNsExecutingAll   = 0;
    uint64_t cNsHaltedAll      = 0;
    for (VMCPUID iCpu = 0; iCpu < pVM->cCpus; iCpu++)
    {
        PVMCPU      pVCpu = &pVM->aCpus[iCpu];

        /* Try get a stable data set. */
        uint32_t    cTries       = 3;
        uint32_t    uTimesGen    = ASMAtomicReadU32(&pVCpu->tm.s.uTimesGen);
        uint64_t    cNsTotal     = pVCpu->tm.s.cNsTotal;
        uint64_t    cNsExecuting = pVCpu->tm.s.cNsExecuting;
        uint64_t    cNsHalted    = pVCpu->tm.s.cNsHalted;
        while (RT_UNLIKELY(   (uTimesGen & 1) /* update in progress */
                           || uTimesGen != ASMAtomicReadU32(&pVCpu->tm.s.uTimesGen)))
        {
            if (!--cTries)
                break;
            ASMNopPause();
            uTimesGen    = ASMAtomicReadU32(&pVCpu->tm.s.uTimesGen);
            cNsTotal     = pVCpu->tm.s.cNsTotal;
            cNsExecuting = pVCpu->tm.s.cNsExecuting;
            cNsHalted    = pVCpu->tm.s.cNsHalted;
        }

        /* Totals */
        cNsTotalAll     += cNsTotal;
        cNsExecutingAll += cNsExecuting;
        cNsHaltedAll    += cNsHalted;

        /* Calc the PCTs and update the state. */
        tmR3CpuLoadTimerMakeUpdate(&pVCpu->tm.s.CpuLoad, cNsTotal, cNsExecuting, cNsHalted);
    }

    /*
     * Update the value for all the CPUs.
     */
    tmR3CpuLoadTimerMakeUpdate(&pVM->tm.s.CpuLoad, cNsTotalAll, cNsExecutingAll, cNsHaltedAll);

    /** @todo Try add 1, 5 and 15 min load stats. */

}

#endif /* !VBOX_WITHOUT_NS_ACCOUNTING */

/**
 * Gets the 5 char clock name for the info tables.
 *
 * @returns The name.
 * @param   enmClock        The clock.
 */
DECLINLINE(const char *) tmR3Get5CharClockName(TMCLOCK enmClock)
{
    switch (enmClock)
    {
        case TMCLOCK_REAL:          return "Real ";
        case TMCLOCK_VIRTUAL:       return "Virt ";
        case TMCLOCK_VIRTUAL_SYNC:  return "VrSy ";
        case TMCLOCK_TSC:           return "TSC  ";
        default:                    return "Bad  ";
    }
}


/**
 * Display all timers.
 *
 * @param   pVM         VM Handle.
 * @param   pHlp        The info helpers.
 * @param   pszArgs     Arguments, ignored.
 */
static DECLCALLBACK(void) tmR3TimerInfo(PVM pVM, PCDBGFINFOHLP pHlp, const char *pszArgs)
{
    NOREF(pszArgs);
    pHlp->pfnPrintf(pHlp,
                    "Timers (pVM=%p)\n"
                    "%.*s %.*s %.*s %.*s Clock %18s %18s %6s %-25s Description\n",
                    pVM,
                    sizeof(RTR3PTR) * 2,        "pTimerR3        ",
                    sizeof(int32_t) * 2,        "offNext         ",
                    sizeof(int32_t) * 2,        "offPrev         ",
                    sizeof(int32_t) * 2,        "offSched        ",
                                                "Time",
                                                "Expire",
                                                "HzHint",
                                                "State");
    tmTimerLock(pVM);
    for (PTMTIMERR3 pTimer = pVM->tm.s.pCreated; pTimer; pTimer = pTimer->pBigNext)
    {
        pHlp->pfnPrintf(pHlp,
                        "%p %08RX32 %08RX32 %08RX32 %s %18RU64 %18RU64 %6RU32 %-25s %s\n",
                        pTimer,
                        pTimer->offNext,
                        pTimer->offPrev,
                        pTimer->offScheduleNext,
                        tmR3Get5CharClockName(pTimer->enmClock),
                        TMTimerGet(pTimer),
                        pTimer->u64Expire,
                        pTimer->uHzHint,
                        tmTimerState(pTimer->enmState),
                        pTimer->pszDesc);
    }
    tmTimerUnlock(pVM);
}


/**
 * Display all active timers.
 *
 * @param   pVM         VM Handle.
 * @param   pHlp        The info helpers.
 * @param   pszArgs     Arguments, ignored.
 */
static DECLCALLBACK(void) tmR3TimerInfoActive(PVM pVM, PCDBGFINFOHLP pHlp, const char *pszArgs)
{
    NOREF(pszArgs);
    pHlp->pfnPrintf(pHlp,
                    "Active Timers (pVM=%p)\n"
                    "%.*s %.*s %.*s %.*s Clock %18s %18s %6s %-25s Description\n",
                    pVM,
                    sizeof(RTR3PTR) * 2,        "pTimerR3        ",
                    sizeof(int32_t) * 2,        "offNext         ",
                    sizeof(int32_t) * 2,        "offPrev         ",
                    sizeof(int32_t) * 2,        "offSched        ",
                                                "Time",
                                                "Expire",
                                                "HzHint",
                                                "State");
    for (unsigned iQueue = 0; iQueue < TMCLOCK_MAX; iQueue++)
    {
        tmTimerLock(pVM);
        for (PTMTIMERR3 pTimer = TMTIMER_GET_HEAD(&pVM->tm.s.paTimerQueuesR3[iQueue]);
             pTimer;
             pTimer = TMTIMER_GET_NEXT(pTimer))
        {
            pHlp->pfnPrintf(pHlp,
                            "%p %08RX32 %08RX32 %08RX32 %s %18RU64 %18RU64 %6RU32 %-25s %s\n",
                            pTimer,
                            pTimer->offNext,
                            pTimer->offPrev,
                            pTimer->offScheduleNext,
                            tmR3Get5CharClockName(pTimer->enmClock),
                            TMTimerGet(pTimer),
                            pTimer->u64Expire,
                            pTimer->uHzHint,
                            tmTimerState(pTimer->enmState),
                            pTimer->pszDesc);
        }
        tmTimerUnlock(pVM);
    }
}


/**
 * Display all clocks.
 *
 * @param   pVM         VM Handle.
 * @param   pHlp        The info helpers.
 * @param   pszArgs     Arguments, ignored.
 */
static DECLCALLBACK(void) tmR3InfoClocks(PVM pVM, PCDBGFINFOHLP pHlp, const char *pszArgs)
{
    NOREF(pszArgs);

    /*
     * Read the times first to avoid more than necessary time variation.
     */
    const uint64_t u64Virtual     = TMVirtualGet(pVM);
    const uint64_t u64VirtualSync = TMVirtualSyncGet(pVM);
    const uint64_t u64Real        = TMRealGet(pVM);

    for (VMCPUID i = 0; i < pVM->cCpus; i++)
    {
        PVMCPU   pVCpu  = &pVM->aCpus[i];
        uint64_t u64TSC = TMCpuTickGet(pVCpu);

        /*
         * TSC
         */
        pHlp->pfnPrintf(pHlp,
                        "Cpu Tick: %18RU64 (%#016RX64) %RU64Hz %s%s",
                        u64TSC, u64TSC, TMCpuTicksPerSecond(pVM),
                        pVCpu->tm.s.fTSCTicking ? "ticking" : "paused",
                        pVM->tm.s.fTSCVirtualized ? " - virtualized" : "");
        if (pVM->tm.s.fTSCUseRealTSC)
        {
            pHlp->pfnPrintf(pHlp, " - real tsc");
            if (pVCpu->tm.s.offTSCRawSrc)
                pHlp->pfnPrintf(pHlp, "\n          offset %RU64", pVCpu->tm.s.offTSCRawSrc);
        }
        else
            pHlp->pfnPrintf(pHlp, " - virtual clock");
        pHlp->pfnPrintf(pHlp, "\n");
    }

    /*
     * virtual
     */
    pHlp->pfnPrintf(pHlp,
                    " Virtual: %18RU64 (%#016RX64) %RU64Hz %s",
                    u64Virtual, u64Virtual, TMVirtualGetFreq(pVM),
                    pVM->tm.s.cVirtualTicking ? "ticking" : "paused");
    if (pVM->tm.s.fVirtualWarpDrive)
        pHlp->pfnPrintf(pHlp, " WarpDrive %RU32 %%", pVM->tm.s.u32VirtualWarpDrivePercentage);
    pHlp->pfnPrintf(pHlp, "\n");

    /*
     * virtual sync
     */
    pHlp->pfnPrintf(pHlp,
                    "VirtSync: %18RU64 (%#016RX64) %s%s",
                    u64VirtualSync, u64VirtualSync,
                    pVM->tm.s.fVirtualSyncTicking ? "ticking" : "paused",
                    pVM->tm.s.fVirtualSyncCatchUp ? " - catchup" : "");
    if (pVM->tm.s.offVirtualSync)
    {
        pHlp->pfnPrintf(pHlp, "\n          offset %RU64", pVM->tm.s.offVirtualSync);
        if (pVM->tm.s.u32VirtualSyncCatchUpPercentage)
            pHlp->pfnPrintf(pHlp, "  catch-up rate %u %%", pVM->tm.s.u32VirtualSyncCatchUpPercentage);
    }
    pHlp->pfnPrintf(pHlp, "\n");

    /*
     * real
     */
    pHlp->pfnPrintf(pHlp,
                    "    Real: %18RU64 (%#016RX64) %RU64Hz\n",
                    u64Real, u64Real, TMRealGetFreq(pVM));
}