Adding upstream version 7.0.14-dfsg.upstream/7.0.14-dfsg

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1462 insertions, 0 deletions

diff --git a/src/VBox/VMM/VMMR3/VMEmt.cpp b/src/VBox/VMM/VMMR3/VMEmt.cpp
new file mode 100644
index 00000000..bbd12fd5
--- /dev/null
+++ b/src/VBox/VMM/VMMR3/VMEmt.cpp
@@ -0,0 +1,1462 @@
+/* $Id: VMEmt.cpp $ */
+/** @file
+ * VM - Virtual Machine, The Emulation Thread.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_VM
+#include <VBox/vmm/tm.h>
+#include <VBox/vmm/dbgf.h>
+#include <VBox/vmm/em.h>
+#include <VBox/vmm/gvmm.h>
+#include <VBox/vmm/nem.h>
+#include <VBox/vmm/pdmapi.h>
+#include <VBox/vmm/tm.h>
+#include "VMInternal.h"
+#include <VBox/vmm/vmcc.h>
+
+#include <VBox/err.h>
+#include <VBox/log.h>
+#include <iprt/assert.h>
+#include <iprt/asm.h>
+#include <iprt/asm-math.h>
+#include <iprt/semaphore.h>
+#include <iprt/string.h>
+#include <iprt/thread.h>
+#include <iprt/time.h>
+
+
+/*********************************************************************************************************************************
+*   Internal Functions                                                                                                           *
+*********************************************************************************************************************************/
+int vmR3EmulationThreadWithId(RTTHREAD hThreadSelf, PUVMCPU pUVCpu, VMCPUID idCpu);
+
+
+/**
+ * The emulation thread main function.
+ *
+ * @returns Thread exit code.
+ * @param   hThreadSelf The handle to the executing thread.
+ * @param   pvArgs      Pointer to the user mode per-VCpu structure (UVMPCU).
+ */
+DECLCALLBACK(int) vmR3EmulationThread(RTTHREAD hThreadSelf, void *pvArgs)
+{
+    PUVMCPU pUVCpu = (PUVMCPU)pvArgs;
+    return vmR3EmulationThreadWithId(hThreadSelf, pUVCpu, pUVCpu->idCpu);
+}
+
+
+/**
+ * The emulation thread main function, with Virtual CPU ID for debugging.
+ *
+ * @returns Thread exit code.
+ * @param   hThreadSelf The handle to the executing thread.
+ * @param   pUVCpu      Pointer to the user mode per-VCpu structure.
+ * @param   idCpu       The virtual CPU ID, for backtrace purposes.
+ */
+int vmR3EmulationThreadWithId(RTTHREAD hThreadSelf, PUVMCPU pUVCpu, VMCPUID idCpu)
+{
+    PUVM    pUVM = pUVCpu->pUVM;
+    int     rc;
+    RT_NOREF_PV(hThreadSelf);
+
+    AssertReleaseMsg(RT_VALID_PTR(pUVM) && pUVM->u32Magic == UVM_MAGIC,
+                     ("Invalid arguments to the emulation thread!\n"));
+
+    rc = RTTlsSet(pUVM->vm.s.idxTLS, pUVCpu);
+    AssertReleaseMsgRCReturn(rc, ("RTTlsSet %x failed with %Rrc\n", pUVM->vm.s.idxTLS, rc), rc);
+
+    if (   pUVM->pVmm2UserMethods
+        && pUVM->pVmm2UserMethods->pfnNotifyEmtInit)
+        pUVM->pVmm2UserMethods->pfnNotifyEmtInit(pUVM->pVmm2UserMethods, pUVM, pUVCpu);
+
+    /*
+     * The request loop.
+     */
+    rc = VINF_SUCCESS;
+    Log(("vmR3EmulationThread: Emulation thread starting the days work... Thread=%#x pUVM=%p\n", hThreadSelf, pUVM));
+    VMSTATE enmBefore = VMSTATE_CREATED; /* (only used for logging atm.) */
+    ASMAtomicIncU32(&pUVM->vm.s.cActiveEmts);
+    for (;;)
+    {
+        /*
+         * During early init there is no pVM and/or pVCpu, so make a special path
+         * for that to keep things clearly separate.
+         */
+        PVM    pVM   = pUVM->pVM;
+        PVMCPU pVCpu = pUVCpu->pVCpu;
+        if (!pVCpu || !pVM)
+        {
+            /*
+             * Check for termination first.
+             */
+            if (pUVM->vm.s.fTerminateEMT)
+            {
+                rc = VINF_EM_TERMINATE;
+                break;
+            }
+
+            /*
+             * Only the first VCPU may initialize the VM during early init
+             * and must therefore service all VMCPUID_ANY requests.
+             * See also VMR3Create
+             */
+            if (    (pUVM->vm.s.pNormalReqs || pUVM->vm.s.pPriorityReqs)
+                &&  pUVCpu->idCpu == 0)
+            {
+                /*
+                 * Service execute in any EMT request.
+                 */
+                rc = VMR3ReqProcessU(pUVM, VMCPUID_ANY, false /*fPriorityOnly*/);
+                Log(("vmR3EmulationThread: Req rc=%Rrc, VM state %s -> %s\n", rc, VMR3GetStateName(enmBefore), pUVM->pVM ? VMR3GetStateName(pUVM->pVM->enmVMState) : "CREATING"));
+            }
+            else if (pUVCpu->vm.s.pNormalReqs || pUVCpu->vm.s.pPriorityReqs)
+            {
+                /*
+                 * Service execute in specific EMT request.
+                 */
+                rc = VMR3ReqProcessU(pUVM, pUVCpu->idCpu, false /*fPriorityOnly*/);
+                Log(("vmR3EmulationThread: Req (cpu=%u) rc=%Rrc, VM state %s -> %s\n", pUVCpu->idCpu, rc, VMR3GetStateName(enmBefore), pUVM->pVM ? VMR3GetStateName(pUVM->pVM->enmVMState) : "CREATING"));
+            }
+            else
+            {
+                /*
+                 * Nothing important is pending, so wait for something.
+                 */
+                rc = VMR3WaitU(pUVCpu);
+                if (RT_FAILURE(rc))
+                {
+                    AssertLogRelMsgFailed(("VMR3WaitU failed with %Rrc\n", rc));
+                    break;
+                }
+            }
+        }
+        else
+        {
+            /*
+             * Pending requests which needs servicing?
+             *
+             * We check for state changes in addition to status codes when
+             * servicing requests. (Look after the ifs.)
+             */
+            enmBefore = pVM->enmVMState;
+            if (pUVM->vm.s.fTerminateEMT)
+            {
+                rc = VINF_EM_TERMINATE;
+                break;
+            }
+
+            if (VM_FF_IS_SET(pVM, VM_FF_EMT_RENDEZVOUS))
+            {
+                rc = VMMR3EmtRendezvousFF(pVM, pVM->apCpusR3[idCpu]);
+                Log(("vmR3EmulationThread: Rendezvous rc=%Rrc, VM state %s -> %s\n", rc, VMR3GetStateName(enmBefore), VMR3GetStateName(pVM->enmVMState)));
+            }
+            else if (pUVM->vm.s.pNormalReqs || pUVM->vm.s.pPriorityReqs)
+            {
+                /*
+                 * Service execute in any EMT request.
+                 */
+                rc = VMR3ReqProcessU(pUVM, VMCPUID_ANY, false /*fPriorityOnly*/);
+                Log(("vmR3EmulationThread: Req rc=%Rrc, VM state %s -> %s\n", rc, VMR3GetStateName(enmBefore), VMR3GetStateName(pVM->enmVMState)));
+            }
+            else if (pUVCpu->vm.s.pNormalReqs || pUVCpu->vm.s.pPriorityReqs)
+            {
+                /*
+                 * Service execute in specific EMT request.
+                 */
+                rc = VMR3ReqProcessU(pUVM, pUVCpu->idCpu, false /*fPriorityOnly*/);
+                Log(("vmR3EmulationThread: Req (cpu=%u) rc=%Rrc, VM state %s -> %s\n", pUVCpu->idCpu, rc, VMR3GetStateName(enmBefore), VMR3GetStateName(pVM->enmVMState)));
+            }
+            else if (   VM_FF_IS_SET(pVM, VM_FF_DBGF)
+                     || VMCPU_FF_IS_SET(pVCpu, VMCPU_FF_DBGF))
+            {
+                /*
+                 * Service the debugger request.
+                 */
+                rc = DBGFR3VMMForcedAction(pVM, pVCpu);
+                Log(("vmR3EmulationThread: Dbg rc=%Rrc, VM state %s -> %s\n", rc, VMR3GetStateName(enmBefore), VMR3GetStateName(pVM->enmVMState)));
+            }
+            else if (VM_FF_TEST_AND_CLEAR(pVM, VM_FF_RESET))
+            {
+                /*
+                 * Service a delayed reset request.
+                 */
+                rc = VBOXSTRICTRC_VAL(VMR3ResetFF(pVM));
+                VM_FF_CLEAR(pVM, VM_FF_RESET);
+                Log(("vmR3EmulationThread: Reset rc=%Rrc, VM state %s -> %s\n", rc, VMR3GetStateName(enmBefore), VMR3GetStateName(pVM->enmVMState)));
+            }
+            else
+            {
+                /*
+                 * Nothing important is pending, so wait for something.
+                 */
+                rc = VMR3WaitU(pUVCpu);
+                if (RT_FAILURE(rc))
+                {
+                    AssertLogRelMsgFailed(("VMR3WaitU failed with %Rrc\n", rc));
+                    break;
+                }
+            }
+
+            /*
+             * Check for termination requests, these have extremely high priority.
+             */
+            if (    rc == VINF_EM_TERMINATE
+                ||  pUVM->vm.s.fTerminateEMT)
+                break;
+        }
+
+        /*
+         * Some requests (both VMR3Req* and the DBGF) can potentially resume
+         * or start the VM, in that case we'll get a change in VM status
+         * indicating that we're now running.
+         */
+        if (RT_SUCCESS(rc))
+        {
+            pVM = pUVM->pVM;
+            if (pVM)
+            {
+                pVCpu = pVM->apCpusR3[idCpu];
+                if (   pVM->enmVMState == VMSTATE_RUNNING
+                    && VMCPUSTATE_IS_STARTED(VMCPU_GET_STATE(pVCpu)))
+                {
+                    rc = EMR3ExecuteVM(pVM, pVCpu);
+                    Log(("vmR3EmulationThread: EMR3ExecuteVM() -> rc=%Rrc, enmVMState=%d\n", rc, pVM->enmVMState));
+                }
+            }
+        }
+
+    } /* forever */
+
+
+    /*
+     * Decrement the active EMT count if we haven't done it yet in vmR3Destroy.
+     */
+    if (!pUVCpu->vm.s.fBeenThruVmDestroy)
+        ASMAtomicDecU32(&pUVM->vm.s.cActiveEmts);
+
+
+    /*
+     * Cleanup and exit.
+     * EMT0 does the VM destruction after all other EMTs have deregistered and terminated.
+     */
+    Log(("vmR3EmulationThread: Terminating emulation thread! Thread=%#x pUVM=%p rc=%Rrc enmBefore=%d enmVMState=%d\n",
+         hThreadSelf, pUVM, rc, enmBefore, pUVM->pVM ? pUVM->pVM->enmVMState : VMSTATE_TERMINATED));
+    PVM pVM;
+    if (   idCpu == 0
+        && (pVM = pUVM->pVM) != NULL)
+    {
+        /* Wait for any other EMTs to terminate before we destroy the VM (see vmR3DestroyVM). */
+        for (VMCPUID iCpu = 1; iCpu < pUVM->cCpus; iCpu++)
+        {
+            RTTHREAD hThread;
+            ASMAtomicXchgHandle(&pUVM->aCpus[iCpu].vm.s.ThreadEMT, NIL_RTTHREAD, &hThread);
+            if (hThread != NIL_RTTHREAD)
+            {
+                int rc2 = RTThreadWait(hThread, 5 * RT_MS_1SEC, NULL);
+                AssertLogRelMsgRC(rc2, ("iCpu=%u rc=%Rrc\n", iCpu, rc2));
+                if (RT_FAILURE(rc2))
+                    pUVM->aCpus[iCpu].vm.s.ThreadEMT = hThread;
+            }
+        }
+
+        /* Switch to the terminated state, clearing the VM pointer and finally destroy the VM. */
+        vmR3SetTerminated(pVM);
+
+        pUVM->pVM = NULL;
+        for (VMCPUID iCpu = 0; iCpu < pUVM->cCpus; iCpu++)
+        {
+            pUVM->aCpus[iCpu].pVM   = NULL;
+            pUVM->aCpus[iCpu].pVCpu = NULL;
+        }
+
+        int rc2 = GVMMR3DestroyVM(pUVM, pVM);
+        AssertLogRelRC(rc2);
+    }
+    /* Deregister the EMT with VMMR0. */
+    else if (   idCpu != 0
+             && (pVM = pUVM->pVM) != NULL)
+    {
+        int rc2 = GVMMR3DeregisterVCpu(pVM, idCpu);
+        AssertLogRelRC(rc2);
+    }
+
+    if (   pUVM->pVmm2UserMethods
+        && pUVM->pVmm2UserMethods->pfnNotifyEmtTerm)
+        pUVM->pVmm2UserMethods->pfnNotifyEmtTerm(pUVM->pVmm2UserMethods, pUVM, pUVCpu);
+
+    pUVCpu->vm.s.NativeThreadEMT = NIL_RTNATIVETHREAD;
+    Log(("vmR3EmulationThread: EMT is terminated.\n"));
+    return rc;
+}
+
+
+/**
+ * Gets the name of a halt method.
+ *
+ * @returns Pointer to a read only string.
+ * @param   enmMethod   The method.
+ */
+static const char *vmR3GetHaltMethodName(VMHALTMETHOD enmMethod)
+{
+    switch (enmMethod)
+    {
+        case VMHALTMETHOD_BOOTSTRAP:    return "bootstrap";
+        case VMHALTMETHOD_DEFAULT:      return "default";
+        case VMHALTMETHOD_OLD:          return "old";
+        case VMHALTMETHOD_1:            return "method1";
+        //case VMHALTMETHOD_2:            return "method2";
+        case VMHALTMETHOD_GLOBAL_1:     return "global1";
+        default:                        return "unknown";
+    }
+}
+
+
+/**
+ * Signal a fatal wait error.
+ *
+ * @returns Fatal error code to be propagated up the call stack.
+ * @param   pUVCpu              The user mode per CPU structure of the calling
+ *                              EMT.
+ * @param   pszFmt              The error format with a single %Rrc in it.
+ * @param   rcFmt               The status code to format.
+ */
+static int vmR3FatalWaitError(PUVMCPU pUVCpu, const char *pszFmt, int rcFmt)
+{
+    /** @todo This is wrong ... raise a fatal error / guru meditation
+     *        instead. */
+    AssertLogRelMsgFailed((pszFmt, rcFmt));
+    ASMAtomicUoWriteBool(&pUVCpu->pUVM->vm.s.fTerminateEMT, true);
+    if (pUVCpu->pVM)
+        VM_FF_SET(pUVCpu->pVM, VM_FF_CHECK_VM_STATE);
+    return VERR_VM_FATAL_WAIT_ERROR;
+}
+
+
+/**
+ * The old halt loop.
+ */
+static DECLCALLBACK(int) vmR3HaltOldDoHalt(PUVMCPU pUVCpu, const uint32_t fMask, uint64_t /* u64Now*/)
+{
+    /*
+     * Halt loop.
+     */
+    PVM    pVM   = pUVCpu->pVM;
+    PVMCPU pVCpu = pUVCpu->pVCpu;
+
+    int rc = VINF_SUCCESS;
+    ASMAtomicWriteBool(&pUVCpu->vm.s.fWait, true);
+    //unsigned cLoops = 0;
+    for (;;)
+    {
+        /*
+         * Work the timers and check if we can exit.
+         * The poll call gives us the ticks left to the next event in
+         * addition to perhaps set an FF.
+         */
+        uint64_t const u64StartTimers   = RTTimeNanoTS();
+        TMR3TimerQueuesDo(pVM);
+        uint64_t const cNsElapsedTimers = RTTimeNanoTS() - u64StartTimers;
+        STAM_REL_PROFILE_ADD_PERIOD(&pUVCpu->vm.s.StatHaltTimers, cNsElapsedTimers);
+        if (    VM_FF_IS_ANY_SET(pVM, VM_FF_EXTERNAL_HALTED_MASK)
+            ||  VMCPU_FF_IS_ANY_SET(pVCpu, fMask))
+            break;
+        uint64_t u64NanoTS;
+        TMTimerPollGIP(pVM, pVCpu, &u64NanoTS);
+        if (    VM_FF_IS_ANY_SET(pVM, VM_FF_EXTERNAL_HALTED_MASK)
+            ||  VMCPU_FF_IS_ANY_SET(pVCpu, fMask))
+            break;
+
+        /*
+         * Wait for a while. Someone will wake us up or interrupt the call if
+         * anything needs our attention.
+         */
+        if (u64NanoTS < 50000)
+        {
+            //RTLogPrintf("u64NanoTS=%RI64 cLoops=%d spin\n", u64NanoTS, cLoops++);
+            /* spin */;
+        }
+        else
+        {
+            VMMR3YieldStop(pVM);
+            //uint64_t u64Start = RTTimeNanoTS();
+            if (u64NanoTS <  870000) /* this is a bit speculative... works fine on linux. */
+            {
+                //RTLogPrintf("u64NanoTS=%RI64 cLoops=%d yield", u64NanoTS, cLoops++);
+                uint64_t const u64StartSchedYield   = RTTimeNanoTS();
+                RTThreadYield(); /* this is the best we can do here */
+                uint64_t const cNsElapsedSchedYield = RTTimeNanoTS() - u64StartSchedYield;
+                STAM_REL_PROFILE_ADD_PERIOD(&pUVCpu->vm.s.StatHaltYield, cNsElapsedSchedYield);
+            }
+            else if (u64NanoTS < 2000000)
+            {
+                //RTLogPrintf("u64NanoTS=%RI64 cLoops=%d sleep 1ms", u64NanoTS, cLoops++);
+                uint64_t const u64StartSchedHalt   = RTTimeNanoTS();
+                rc = RTSemEventWait(pUVCpu->vm.s.EventSemWait, 1);
+                uint64_t const cNsElapsedSchedHalt = RTTimeNanoTS() - u64StartSchedHalt;
+                STAM_REL_PROFILE_ADD_PERIOD(&pUVCpu->vm.s.StatHaltBlock, cNsElapsedSchedHalt);
+            }
+            else
+            {
+                //RTLogPrintf("u64NanoTS=%RI64 cLoops=%d sleep %dms", u64NanoTS, cLoops++, (uint32_t)RT_MIN((u64NanoTS - 500000) / 1000000, 15));
+                uint64_t const u64StartSchedHalt   = RTTimeNanoTS();
+                rc = RTSemEventWait(pUVCpu->vm.s.EventSemWait, RT_MIN((u64NanoTS - 1000000) / 1000000, 15));
+                uint64_t const cNsElapsedSchedHalt = RTTimeNanoTS() - u64StartSchedHalt;
+                STAM_REL_PROFILE_ADD_PERIOD(&pUVCpu->vm.s.StatHaltBlock, cNsElapsedSchedHalt);
+            }
+            //uint64_t u64Slept = RTTimeNanoTS() - u64Start;
+            //RTLogPrintf(" -> rc=%Rrc in %RU64 ns / %RI64 ns delta\n", rc, u64Slept, u64NanoTS - u64Slept);
+        }
+        if (rc == VERR_TIMEOUT)
+            rc = VINF_SUCCESS;
+        else if (RT_FAILURE(rc))
+        {
+            rc = vmR3FatalWaitError(pUVCpu, "RTSemEventWait->%Rrc\n", rc);
+            break;
+        }
+    }
+
+    ASMAtomicUoWriteBool(&pUVCpu->vm.s.fWait, false);
+    return rc;
+}
+
+
+/**
+ * Initialize the configuration of halt method 1 & 2.
+ *
+ * @return VBox status code. Failure on invalid CFGM data.
+ * @param   pUVM        The user mode VM structure.
+ */
+static int vmR3HaltMethod12ReadConfigU(PUVM pUVM)
+{
+    /*
+     * The defaults.
+     */
+#if 1 /* DEBUGGING STUFF - REMOVE LATER */
+    pUVM->vm.s.Halt.Method12.u32LagBlockIntervalDivisorCfg = 4;
+    pUVM->vm.s.Halt.Method12.u32MinBlockIntervalCfg =   2*1000000;
+    pUVM->vm.s.Halt.Method12.u32MaxBlockIntervalCfg =  75*1000000;
+    pUVM->vm.s.Halt.Method12.u32StartSpinningCfg    =  30*1000000;
+    pUVM->vm.s.Halt.Method12.u32StopSpinningCfg     =  20*1000000;
+#else
+    pUVM->vm.s.Halt.Method12.u32LagBlockIntervalDivisorCfg = 4;
+    pUVM->vm.s.Halt.Method12.u32MinBlockIntervalCfg =   5*1000000;
+    pUVM->vm.s.Halt.Method12.u32MaxBlockIntervalCfg = 200*1000000;
+    pUVM->vm.s.Halt.Method12.u32StartSpinningCfg    =  20*1000000;
+    pUVM->vm.s.Halt.Method12.u32StopSpinningCfg     =   2*1000000;
+#endif
+
+    /*
+     * Query overrides.
+     *
+     * I don't have time to bother with niceties such as invalid value checks
+     * here right now. sorry.
+     */
+    PCFGMNODE pCfg = CFGMR3GetChild(CFGMR3GetRoot(pUVM->pVM), "/VMM/HaltedMethod1");
+    if (pCfg)
+    {
+        uint32_t u32;
+        if (RT_SUCCESS(CFGMR3QueryU32(pCfg, "LagBlockIntervalDivisor", &u32)))
+            pUVM->vm.s.Halt.Method12.u32LagBlockIntervalDivisorCfg = u32;
+        if (RT_SUCCESS(CFGMR3QueryU32(pCfg, "MinBlockInterval", &u32)))
+            pUVM->vm.s.Halt.Method12.u32MinBlockIntervalCfg = u32;
+        if (RT_SUCCESS(CFGMR3QueryU32(pCfg, "MaxBlockInterval", &u32)))
+            pUVM->vm.s.Halt.Method12.u32MaxBlockIntervalCfg = u32;
+        if (RT_SUCCESS(CFGMR3QueryU32(pCfg, "StartSpinning", &u32)))
+            pUVM->vm.s.Halt.Method12.u32StartSpinningCfg = u32;
+        if (RT_SUCCESS(CFGMR3QueryU32(pCfg, "StopSpinning", &u32)))
+            pUVM->vm.s.Halt.Method12.u32StopSpinningCfg = u32;
+        LogRel(("VMEmt: HaltedMethod1 config: %d/%d/%d/%d/%d\n",
+                pUVM->vm.s.Halt.Method12.u32LagBlockIntervalDivisorCfg,
+                pUVM->vm.s.Halt.Method12.u32MinBlockIntervalCfg,
+                pUVM->vm.s.Halt.Method12.u32MaxBlockIntervalCfg,
+                pUVM->vm.s.Halt.Method12.u32StartSpinningCfg,
+                pUVM->vm.s.Halt.Method12.u32StopSpinningCfg));
+    }
+
+    return VINF_SUCCESS;
+}
+
+
+/**
+ * Initialize halt method 1.
+ *
+ * @return VBox status code.
+ * @param   pUVM            Pointer to the user mode VM structure.
+ */
+static DECLCALLBACK(int) vmR3HaltMethod1Init(PUVM pUVM)
+{
+    return vmR3HaltMethod12ReadConfigU(pUVM);
+}
+
+
+/**
+ * Method 1 - Block whenever possible, and when lagging behind
+ * switch to spinning for 10-30ms with occasional blocking until
+ * the lag has been eliminated.
+ */
+static DECLCALLBACK(int) vmR3HaltMethod1Halt(PUVMCPU pUVCpu, const uint32_t fMask, uint64_t u64Now)
+{
+    PUVM    pUVM    = pUVCpu->pUVM;
+    PVMCPU  pVCpu   = pUVCpu->pVCpu;
+    PVM     pVM     = pUVCpu->pVM;
+
+    /*
+     * To simplify things, we decide up-front whether we should switch to spinning or
+     * not. This makes some ASSUMPTIONS about the cause of the spinning (PIT/RTC/PCNet)
+     * and that it will generate interrupts or other events that will cause us to exit
+     * the halt loop.
+     */
+    bool fBlockOnce = false;
+    bool fSpinning = false;
+    uint32_t u32CatchUpPct = TMVirtualSyncGetCatchUpPct(pVM);
+    if (u32CatchUpPct /* non-zero if catching up */)
+    {
+        if (pUVCpu->vm.s.Halt.Method12.u64StartSpinTS)
+        {
+            fSpinning = TMVirtualSyncGetLag(pVM) >= pUVM->vm.s.Halt.Method12.u32StopSpinningCfg;
+            if (fSpinning)
+            {
+                uint64_t u64Lag = TMVirtualSyncGetLag(pVM);
+                fBlockOnce = u64Now - pUVCpu->vm.s.Halt.Method12.u64LastBlockTS
+                           > RT_MAX(pUVM->vm.s.Halt.Method12.u32MinBlockIntervalCfg,
+                                    RT_MIN(u64Lag / pUVM->vm.s.Halt.Method12.u32LagBlockIntervalDivisorCfg,
+                                           pUVM->vm.s.Halt.Method12.u32MaxBlockIntervalCfg));
+            }
+            else
+            {
+                //RTLogRelPrintf("Stopped spinning (%u ms)\n", (u64Now - pUVCpu->vm.s.Halt.Method12.u64StartSpinTS) / 1000000);
+                pUVCpu->vm.s.Halt.Method12.u64StartSpinTS = 0;
+            }
+        }
+        else
+        {
+            fSpinning = TMVirtualSyncGetLag(pVM) >= pUVM->vm.s.Halt.Method12.u32StartSpinningCfg;
+            if (fSpinning)
+                pUVCpu->vm.s.Halt.Method12.u64StartSpinTS = u64Now;
+        }
+    }
+    else if (pUVCpu->vm.s.Halt.Method12.u64StartSpinTS)
+    {
+        //RTLogRelPrintf("Stopped spinning (%u ms)\n", (u64Now - pUVCpu->vm.s.Halt.Method12.u64StartSpinTS) / 1000000);
+        pUVCpu->vm.s.Halt.Method12.u64StartSpinTS = 0;
+    }
+
+    /*
+     * Halt loop.
+     */
+    int rc = VINF_SUCCESS;
+    ASMAtomicWriteBool(&pUVCpu->vm.s.fWait, true);
+    unsigned cLoops = 0;
+    for (;; cLoops++)
+    {
+        /*
+         * Work the timers and check if we can exit.
+         */
+        uint64_t const u64StartTimers   = RTTimeNanoTS();
+        TMR3TimerQueuesDo(pVM);
+        uint64_t const cNsElapsedTimers = RTTimeNanoTS() - u64StartTimers;
+        STAM_REL_PROFILE_ADD_PERIOD(&pUVCpu->vm.s.StatHaltTimers, cNsElapsedTimers);
+        if (    VM_FF_IS_ANY_SET(pVM, VM_FF_EXTERNAL_HALTED_MASK)
+            ||  VMCPU_FF_IS_ANY_SET(pVCpu, fMask))
+            break;
+
+        /*
+         * Estimate time left to the next event.
+         */
+        uint64_t u64NanoTS;
+        TMTimerPollGIP(pVM, pVCpu, &u64NanoTS);
+        if (    VM_FF_IS_ANY_SET(pVM, VM_FF_EXTERNAL_HALTED_MASK)
+            ||  VMCPU_FF_IS_ANY_SET(pVCpu, fMask))
+            break;
+
+        /*
+         * Block if we're not spinning and the interval isn't all that small.
+         */
+        if (    (   !fSpinning
+                 || fBlockOnce)
+#if 1 /* DEBUGGING STUFF - REMOVE LATER */
+            &&  u64NanoTS >= 100000) /* 0.100 ms */
+#else
+            &&  u64NanoTS >= 250000) /* 0.250 ms */
+#endif
+        {
+            const uint64_t Start = pUVCpu->vm.s.Halt.Method12.u64LastBlockTS = RTTimeNanoTS();
+            VMMR3YieldStop(pVM);
+
+            uint32_t cMilliSecs = RT_MIN(u64NanoTS / 1000000, 15);
+            if (cMilliSecs <= pUVCpu->vm.s.Halt.Method12.cNSBlockedTooLongAvg)
+                cMilliSecs = 1;
+            else
+                cMilliSecs -= pUVCpu->vm.s.Halt.Method12.cNSBlockedTooLongAvg;
+
+            //RTLogRelPrintf("u64NanoTS=%RI64 cLoops=%3d sleep %02dms (%7RU64) ", u64NanoTS, cLoops, cMilliSecs, u64NanoTS);
+            uint64_t const u64StartSchedHalt   = RTTimeNanoTS();
+            rc = RTSemEventWait(pUVCpu->vm.s.EventSemWait, cMilliSecs);
+            uint64_t const cNsElapsedSchedHalt = RTTimeNanoTS() - u64StartSchedHalt;
+            STAM_REL_PROFILE_ADD_PERIOD(&pUVCpu->vm.s.StatHaltBlock, cNsElapsedSchedHalt);
+
+            if (rc == VERR_TIMEOUT)
+                rc = VINF_SUCCESS;
+            else if (RT_FAILURE(rc))
+            {
+                rc = vmR3FatalWaitError(pUVCpu, "RTSemEventWait->%Rrc\n", rc);
+                break;
+            }
+
+            /*
+             * Calc the statistics.
+             * Update averages every 16th time, and flush parts of the history every 64th time.
+             */
+            const uint64_t Elapsed = RTTimeNanoTS() - Start;
+            pUVCpu->vm.s.Halt.Method12.cNSBlocked += Elapsed;
+            if (Elapsed > u64NanoTS)
+                pUVCpu->vm.s.Halt.Method12.cNSBlockedTooLong += Elapsed - u64NanoTS;
+            pUVCpu->vm.s.Halt.Method12.cBlocks++;
+            if (!(pUVCpu->vm.s.Halt.Method12.cBlocks & 0xf))
+            {
+                pUVCpu->vm.s.Halt.Method12.cNSBlockedTooLongAvg = pUVCpu->vm.s.Halt.Method12.cNSBlockedTooLong / pUVCpu->vm.s.Halt.Method12.cBlocks;
+                if (!(pUVCpu->vm.s.Halt.Method12.cBlocks & 0x3f))
+                {
+                    pUVCpu->vm.s.Halt.Method12.cNSBlockedTooLong = pUVCpu->vm.s.Halt.Method12.cNSBlockedTooLongAvg * 0x40;
+                    pUVCpu->vm.s.Halt.Method12.cBlocks = 0x40;
+                }
+            }
+            //RTLogRelPrintf(" -> %7RU64 ns / %7RI64 ns delta%s\n", Elapsed, Elapsed - u64NanoTS, fBlockOnce ? " (block once)" : "");
+
+            /*
+             * Clear the block once flag if we actually blocked.
+             */
+            if (    fBlockOnce
+                &&  Elapsed > 100000 /* 0.1 ms */)
+                fBlockOnce = false;
+        }
+    }
+    //if (fSpinning) RTLogRelPrintf("spun for %RU64 ns %u loops; lag=%RU64 pct=%d\n", RTTimeNanoTS() - u64Now, cLoops, TMVirtualSyncGetLag(pVM), u32CatchUpPct);
+
+    ASMAtomicUoWriteBool(&pUVCpu->vm.s.fWait, false);
+    return rc;
+}
+
+
+/**
+ * Initialize the global 1 halt method.
+ *
+ * @return VBox status code.
+ * @param   pUVM            Pointer to the user mode VM structure.
+ */
+static DECLCALLBACK(int) vmR3HaltGlobal1Init(PUVM pUVM)
+{
+    /*
+     * The defaults.
+     */
+    uint32_t cNsResolution = SUPSemEventMultiGetResolution(pUVM->vm.s.pSession);
+    if (cNsResolution > 5*RT_NS_100US)
+        pUVM->vm.s.Halt.Global1.cNsSpinBlockThresholdCfg = 50000;
+    else if (cNsResolution > RT_NS_100US)
+        pUVM->vm.s.Halt.Global1.cNsSpinBlockThresholdCfg = cNsResolution / 4;
+    else
+        pUVM->vm.s.Halt.Global1.cNsSpinBlockThresholdCfg = 2000;
+
+    /*
+     * Query overrides.
+     *
+     * I don't have time to bother with niceties such as invalid value checks
+     * here right now. sorry.
+     */
+    PCFGMNODE pCfg = CFGMR3GetChild(CFGMR3GetRoot(pUVM->pVM), "/VMM/HaltedGlobal1");
+    if (pCfg)
+    {
+        uint32_t u32;
+        if (RT_SUCCESS(CFGMR3QueryU32(pCfg, "SpinBlockThreshold", &u32)))
+            pUVM->vm.s.Halt.Global1.cNsSpinBlockThresholdCfg = u32;
+    }
+    LogRel(("VMEmt: HaltedGlobal1 config: cNsSpinBlockThresholdCfg=%u\n",
+            pUVM->vm.s.Halt.Global1.cNsSpinBlockThresholdCfg));
+    return VINF_SUCCESS;
+}
+
+
+/**
+ * The global 1 halt method - Block in GMM (ring-0) and let it
+ * try take care of the global scheduling of EMT threads.
+ */
+static DECLCALLBACK(int) vmR3HaltGlobal1Halt(PUVMCPU pUVCpu, const uint32_t fMask, uint64_t u64Now)
+{
+    PUVM    pUVM  = pUVCpu->pUVM;
+    PVMCPU  pVCpu = pUVCpu->pVCpu;
+    PVM     pVM   = pUVCpu->pVM;
+    Assert(VMMGetCpu(pVM) == pVCpu);
+    NOREF(u64Now);
+
+    /*
+     * Halt loop.
+     */
+    //uint64_t u64NowLog, u64Start;
+    //u64Start = u64NowLog = RTTimeNanoTS();
+    int rc = VINF_SUCCESS;
+    ASMAtomicWriteBool(&pUVCpu->vm.s.fWait, true);
+    unsigned cLoops = 0;
+    for (;; cLoops++)
+    {
+        /*
+         * Work the timers and check if we can exit.
+         */
+        uint64_t const u64StartTimers   = RTTimeNanoTS();
+        TMR3TimerQueuesDo(pVM);
+        uint64_t const cNsElapsedTimers = RTTimeNanoTS() - u64StartTimers;
+        STAM_REL_PROFILE_ADD_PERIOD(&pUVCpu->vm.s.StatHaltTimers, cNsElapsedTimers);
+        if (    VM_FF_IS_ANY_SET(pVM, VM_FF_EXTERNAL_HALTED_MASK)
+            ||  VMCPU_FF_IS_ANY_SET(pVCpu, fMask))
+            break;
+
+        /*
+         * Estimate time left to the next event.
+         */
+        //u64NowLog = RTTimeNanoTS();
+        uint64_t u64Delta;
+        uint64_t u64GipTime = TMTimerPollGIP(pVM, pVCpu, &u64Delta);
+        if (    VM_FF_IS_ANY_SET(pVM, VM_FF_EXTERNAL_HALTED_MASK)
+            ||  VMCPU_FF_IS_ANY_SET(pVCpu, fMask))
+            break;
+
+        /*
+         * Block if we're not spinning and the interval isn't all that small.
+         */
+        if (u64Delta >= pUVM->vm.s.Halt.Global1.cNsSpinBlockThresholdCfg)
+        {
+            VMMR3YieldStop(pVM);
+            if (    VM_FF_IS_ANY_SET(pVM, VM_FF_EXTERNAL_HALTED_MASK)
+                ||  VMCPU_FF_IS_ANY_SET(pVCpu, fMask))
+                break;
+
+            //RTLogPrintf("loop=%-3d  u64GipTime=%'llu / %'llu   now=%'llu / %'llu\n", cLoops, u64GipTime, u64Delta, u64NowLog, u64GipTime - u64NowLog);
+            uint64_t const u64StartSchedHalt   = RTTimeNanoTS();
+            rc = SUPR3CallVMMR0Ex(VMCC_GET_VMR0_FOR_CALL(pVM), pVCpu->idCpu, VMMR0_DO_GVMM_SCHED_HALT, u64GipTime, NULL);
+            uint64_t const u64EndSchedHalt     = RTTimeNanoTS();
+            uint64_t const cNsElapsedSchedHalt = u64EndSchedHalt - u64StartSchedHalt;
+            STAM_REL_PROFILE_ADD_PERIOD(&pUVCpu->vm.s.StatHaltBlock, cNsElapsedSchedHalt);
+
+            if (rc == VERR_INTERRUPTED)
+                rc = VINF_SUCCESS;
+            else if (RT_FAILURE(rc))
+            {
+                rc = vmR3FatalWaitError(pUVCpu, "vmR3HaltGlobal1Halt: VMMR0_DO_GVMM_SCHED_HALT->%Rrc\n", rc);
+                break;
+            }
+            else
+            {
+                int64_t const cNsOverslept = u64EndSchedHalt - u64GipTime;
+                if (cNsOverslept > 50000)
+                    STAM_REL_PROFILE_ADD_PERIOD(&pUVCpu->vm.s.StatHaltBlockOverslept, cNsOverslept);
+                else if (cNsOverslept < -50000)
+                    STAM_REL_PROFILE_ADD_PERIOD(&pUVCpu->vm.s.StatHaltBlockInsomnia,  cNsElapsedSchedHalt);
+                else
+                    STAM_REL_PROFILE_ADD_PERIOD(&pUVCpu->vm.s.StatHaltBlockOnTime,    cNsElapsedSchedHalt);
+            }
+        }
+        /*
+         * When spinning call upon the GVMM and do some wakups once
+         * in a while, it's not like we're actually busy or anything.
+         */
+        else if (!(cLoops & 0x1fff))
+        {
+            uint64_t const u64StartSchedYield   = RTTimeNanoTS();
+            rc = SUPR3CallVMMR0Ex(VMCC_GET_VMR0_FOR_CALL(pVM), pVCpu->idCpu, VMMR0_DO_GVMM_SCHED_POLL, false /* don't yield */, NULL);
+            uint64_t const cNsElapsedSchedYield = RTTimeNanoTS() - u64StartSchedYield;
+            STAM_REL_PROFILE_ADD_PERIOD(&pUVCpu->vm.s.StatHaltYield, cNsElapsedSchedYield);
+        }
+    }
+    //RTLogPrintf("*** %u loops %'llu;  lag=%RU64\n", cLoops, u64NowLog - u64Start, TMVirtualSyncGetLag(pVM));
+
+    ASMAtomicUoWriteBool(&pUVCpu->vm.s.fWait, false);
+    return rc;
+}
+
+
+/**
+ * The global 1 halt method - VMR3Wait() worker.
+ *
+ * @returns VBox status code.
+ * @param   pUVCpu            Pointer to the user mode VMCPU structure.
+ */
+static DECLCALLBACK(int) vmR3HaltGlobal1Wait(PUVMCPU pUVCpu)
+{
+    ASMAtomicWriteBool(&pUVCpu->vm.s.fWait, true);
+
+    PVM    pVM   = pUVCpu->pUVM->pVM;
+    PVMCPU pVCpu = VMMGetCpu(pVM);
+    Assert(pVCpu->idCpu == pUVCpu->idCpu);
+
+    int rc = VINF_SUCCESS;
+    for (;;)
+    {
+        /*
+         * Check Relevant FFs.
+         */
+        if (    VM_FF_IS_ANY_SET(pVM, VM_FF_EXTERNAL_SUSPENDED_MASK)
+            ||  VMCPU_FF_IS_ANY_SET(pVCpu, VMCPU_FF_EXTERNAL_SUSPENDED_MASK))
+            break;
+
+        /*
+         * Wait for a while. Someone will wake us up or interrupt the call if
+         * anything needs our attention.
+         */
+        rc = SUPR3CallVMMR0Ex(VMCC_GET_VMR0_FOR_CALL(pVM), pVCpu->idCpu, VMMR0_DO_GVMM_SCHED_HALT, RTTimeNanoTS() + 1000000000 /* +1s */, NULL);
+        if (rc == VERR_INTERRUPTED)
+            rc = VINF_SUCCESS;
+        else if (RT_FAILURE(rc))
+        {
+            rc = vmR3FatalWaitError(pUVCpu, "vmR3HaltGlobal1Wait: VMMR0_DO_GVMM_SCHED_HALT->%Rrc\n", rc);
+            break;
+        }
+    }
+
+    ASMAtomicUoWriteBool(&pUVCpu->vm.s.fWait, false);
+    return rc;
+}
+
+
+/**
+ * The global 1 halt method - VMR3NotifyFF() worker.
+ *
+ * @param   pUVCpu          Pointer to the user mode VMCPU structure.
+ * @param   fFlags          Notification flags, VMNOTIFYFF_FLAGS_*.
+ */
+static DECLCALLBACK(void) vmR3HaltGlobal1NotifyCpuFF(PUVMCPU pUVCpu, uint32_t fFlags)
+{
+    /*
+     * With ring-0 halting, the fWait flag isn't set, so we have to check the
+     * CPU state to figure out whether to do a wakeup call.
+     */
+    PVMCPU pVCpu = pUVCpu->pVCpu;
+    if (pVCpu)
+    {
+        VMCPUSTATE enmState = VMCPU_GET_STATE(pVCpu);
+        if (enmState == VMCPUSTATE_STARTED_HALTED || pUVCpu->vm.s.fWait)
+        {
+            int rc = SUPR3CallVMMR0Ex(VMCC_GET_VMR0_FOR_CALL(pUVCpu->pVM), pUVCpu->idCpu, VMMR0_DO_GVMM_SCHED_WAKE_UP, 0, NULL);
+            AssertRC(rc);
+
+        }
+        else if (   (fFlags & VMNOTIFYFF_FLAGS_POKE)
+                 || !(fFlags & VMNOTIFYFF_FLAGS_DONE_REM))
+        {
+            if (enmState == VMCPUSTATE_STARTED_EXEC)
+            {
+                if (fFlags & VMNOTIFYFF_FLAGS_POKE)
+                {
+                    int rc = SUPR3CallVMMR0Ex(VMCC_GET_VMR0_FOR_CALL(pUVCpu->pVM), pUVCpu->idCpu, VMMR0_DO_GVMM_SCHED_POKE, 0, NULL);
+                    AssertRC(rc);
+                }
+            }
+            else if (   enmState == VMCPUSTATE_STARTED_EXEC_NEM
+                     || enmState == VMCPUSTATE_STARTED_EXEC_NEM_WAIT)
+                NEMR3NotifyFF(pUVCpu->pVM, pVCpu, fFlags);
+        }
+    }
+    /* This probably makes little sense: */
+    else if (pUVCpu->vm.s.fWait)
+    {
+        int rc = SUPR3CallVMMR0Ex(VMCC_GET_VMR0_FOR_CALL(pUVCpu->pVM), pUVCpu->idCpu, VMMR0_DO_GVMM_SCHED_WAKE_UP, 0, NULL);
+        AssertRC(rc);
+    }
+}
+
+
+/**
+ * Bootstrap VMR3Wait() worker.
+ *
+ * @returns VBox status code.
+ * @param   pUVCpu      Pointer to the user mode VMCPU structure.
+ */
+static DECLCALLBACK(int) vmR3BootstrapWait(PUVMCPU pUVCpu)
+{
+    PUVM pUVM = pUVCpu->pUVM;
+
+    ASMAtomicWriteBool(&pUVCpu->vm.s.fWait, true);
+
+    int rc = VINF_SUCCESS;
+    for (;;)
+    {
+        /*
+         * Check Relevant FFs.
+         */
+        if (pUVM->vm.s.pNormalReqs   || pUVM->vm.s.pPriorityReqs)   /* global requests pending? */
+            break;
+        if (pUVCpu->vm.s.pNormalReqs || pUVCpu->vm.s.pPriorityReqs) /* local requests pending? */
+            break;
+
+        if (    pUVCpu->pVM
+            &&  (   VM_FF_IS_ANY_SET(pUVCpu->pVM, VM_FF_EXTERNAL_SUSPENDED_MASK)
+                 || VMCPU_FF_IS_ANY_SET(VMMGetCpu(pUVCpu->pVM), VMCPU_FF_EXTERNAL_SUSPENDED_MASK)
+                )
+            )
+            break;
+        if (pUVM->vm.s.fTerminateEMT)
+            break;
+
+        /*
+         * Wait for a while. Someone will wake us up or interrupt the call if
+         * anything needs our attention.
+         */
+        rc = RTSemEventWait(pUVCpu->vm.s.EventSemWait, 1000);
+        if (rc == VERR_TIMEOUT)
+            rc = VINF_SUCCESS;
+        else if (RT_FAILURE(rc))
+        {
+            rc = vmR3FatalWaitError(pUVCpu, "RTSemEventWait->%Rrc\n", rc);
+            break;
+        }
+    }
+
+    ASMAtomicUoWriteBool(&pUVCpu->vm.s.fWait, false);
+    return rc;
+}
+
+
+/**
+ * Bootstrap VMR3NotifyFF() worker.
+ *
+ * @param   pUVCpu          Pointer to the user mode VMCPU structure.
+ * @param   fFlags          Notification flags, VMNOTIFYFF_FLAGS_*.
+ */
+static DECLCALLBACK(void) vmR3BootstrapNotifyCpuFF(PUVMCPU pUVCpu, uint32_t fFlags)
+{
+    if (pUVCpu->vm.s.fWait)
+    {
+        int rc = RTSemEventSignal(pUVCpu->vm.s.EventSemWait);
+        AssertRC(rc);
+    }
+    NOREF(fFlags);
+}
+
+
+/**
+ * Default VMR3Wait() worker.
+ *
+ * @returns VBox status code.
+ * @param   pUVCpu          Pointer to the user mode VMCPU structure.
+ */
+static DECLCALLBACK(int) vmR3DefaultWait(PUVMCPU pUVCpu)
+{
+    ASMAtomicWriteBool(&pUVCpu->vm.s.fWait, true);
+
+    PVM    pVM   = pUVCpu->pVM;
+    PVMCPU pVCpu = pUVCpu->pVCpu;
+    int    rc    = VINF_SUCCESS;
+    for (;;)
+    {
+        /*
+         * Check Relevant FFs.
+         */
+        if (    VM_FF_IS_ANY_SET(pVM, VM_FF_EXTERNAL_SUSPENDED_MASK)
+            ||  VMCPU_FF_IS_ANY_SET(pVCpu, VMCPU_FF_EXTERNAL_SUSPENDED_MASK))
+            break;
+
+        /*
+         * Wait for a while. Someone will wake us up or interrupt the call if
+         * anything needs our attention.
+         */
+        rc = RTSemEventWait(pUVCpu->vm.s.EventSemWait, 1000);
+        if (rc == VERR_TIMEOUT)
+            rc = VINF_SUCCESS;
+        else if (RT_FAILURE(rc))
+        {
+            rc = vmR3FatalWaitError(pUVCpu, "RTSemEventWait->%Rrc", rc);
+            break;
+        }
+    }
+
+    ASMAtomicUoWriteBool(&pUVCpu->vm.s.fWait, false);
+    return rc;
+}
+
+
+/**
+ * Default VMR3NotifyFF() worker.
+ *
+ * @param   pUVCpu          Pointer to the user mode VMCPU structure.
+ * @param   fFlags          Notification flags, VMNOTIFYFF_FLAGS_*.
+ */
+static DECLCALLBACK(void) vmR3DefaultNotifyCpuFF(PUVMCPU pUVCpu, uint32_t fFlags)
+{
+    if (pUVCpu->vm.s.fWait)
+    {
+        int rc = RTSemEventSignal(pUVCpu->vm.s.EventSemWait);
+        AssertRC(rc);
+    }
+    else
+    {
+        PVMCPU pVCpu = pUVCpu->pVCpu;
+        if (pVCpu)
+        {
+            VMCPUSTATE enmState = pVCpu->enmState;
+            if (   enmState == VMCPUSTATE_STARTED_EXEC_NEM
+                || enmState == VMCPUSTATE_STARTED_EXEC_NEM_WAIT)
+                NEMR3NotifyFF(pUVCpu->pVM, pVCpu, fFlags);
+        }
+    }
+}
+
+
+/**
+ * Array with halt method descriptors.
+ * VMINT::iHaltMethod contains an index into this array.
+ */
+static const struct VMHALTMETHODDESC
+{
+    /** The halt method ID. */
+    VMHALTMETHOD                enmHaltMethod;
+    /** Set if the method support halting directly in ring-0. */
+    bool                        fMayHaltInRing0;
+    /** The init function for loading config and initialize variables. */
+    DECLR3CALLBACKMEMBER(int,   pfnInit,(PUVM pUVM));
+    /** The term function. */
+    DECLR3CALLBACKMEMBER(void,  pfnTerm,(PUVM pUVM));
+    /** The VMR3WaitHaltedU function. */
+    DECLR3CALLBACKMEMBER(int,   pfnHalt,(PUVMCPU pUVCpu, const uint32_t fMask, uint64_t u64Now));
+    /** The VMR3WaitU function. */
+    DECLR3CALLBACKMEMBER(int,   pfnWait,(PUVMCPU pUVCpu));
+    /** The VMR3NotifyCpuFFU function. */
+    DECLR3CALLBACKMEMBER(void,  pfnNotifyCpuFF,(PUVMCPU pUVCpu, uint32_t fFlags));
+    /** The VMR3NotifyGlobalFFU function. */
+    DECLR3CALLBACKMEMBER(void,  pfnNotifyGlobalFF,(PUVM pUVM, uint32_t fFlags));
+} g_aHaltMethods[] =
+{
+    { VMHALTMETHOD_BOOTSTRAP, false, NULL,                NULL,   NULL,                vmR3BootstrapWait,   vmR3BootstrapNotifyCpuFF,   NULL },
+    { VMHALTMETHOD_OLD,       false, NULL,                NULL,   vmR3HaltOldDoHalt,   vmR3DefaultWait,     vmR3DefaultNotifyCpuFF,     NULL },
+    { VMHALTMETHOD_1,         false, vmR3HaltMethod1Init, NULL,   vmR3HaltMethod1Halt, vmR3DefaultWait,     vmR3DefaultNotifyCpuFF,     NULL },
+    { VMHALTMETHOD_GLOBAL_1,   true, vmR3HaltGlobal1Init, NULL,   vmR3HaltGlobal1Halt, vmR3HaltGlobal1Wait, vmR3HaltGlobal1NotifyCpuFF, NULL },
+};
+
+
+/**
+ * Notify the emulation thread (EMT) about pending Forced Action (FF).
+ *
+ * This function is called by thread other than EMT to make
+ * sure EMT wakes up and promptly service an FF request.
+ *
+ * @param   pUVM            Pointer to the user mode VM structure.
+ * @param   fFlags          Notification flags, VMNOTIFYFF_FLAGS_*.
+ * @internal
+ */
+VMMR3_INT_DECL(void) VMR3NotifyGlobalFFU(PUVM pUVM, uint32_t fFlags)
+{
+    LogFlow(("VMR3NotifyGlobalFFU:\n"));
+    uint32_t iHaltMethod = pUVM->vm.s.iHaltMethod;
+
+    if (g_aHaltMethods[iHaltMethod].pfnNotifyGlobalFF) /** @todo make mandatory. */
+        g_aHaltMethods[iHaltMethod].pfnNotifyGlobalFF(pUVM, fFlags);
+    else
+        for (VMCPUID iCpu = 0; iCpu < pUVM->cCpus; iCpu++)
+            g_aHaltMethods[iHaltMethod].pfnNotifyCpuFF(&pUVM->aCpus[iCpu], fFlags);
+}
+
+
+/**
+ * Notify the emulation thread (EMT) about pending Forced Action (FF).
+ *
+ * This function is called by thread other than EMT to make
+ * sure EMT wakes up and promptly service an FF request.
+ *
+ * @param   pUVCpu          Pointer to the user mode per CPU VM structure.
+ * @param   fFlags          Notification flags, VMNOTIFYFF_FLAGS_*.
+ * @internal
+ */
+VMMR3_INT_DECL(void) VMR3NotifyCpuFFU(PUVMCPU pUVCpu, uint32_t fFlags)
+{
+    PUVM pUVM = pUVCpu->pUVM;
+
+    LogFlow(("VMR3NotifyCpuFFU:\n"));
+    g_aHaltMethods[pUVM->vm.s.iHaltMethod].pfnNotifyCpuFF(pUVCpu, fFlags);
+}
+
+
+/**
+ * Halted VM Wait.
+ * Any external event will unblock the thread.
+ *
+ * @returns VINF_SUCCESS unless a fatal error occurred. In the latter
+ *          case an appropriate status code is returned.
+ * @param   pVM         The cross context VM structure.
+ * @param   pVCpu       The cross context virtual CPU structure.
+ * @param   fIgnoreInterrupts   If set the VM_FF_INTERRUPT flags is ignored.
+ * @thread  The emulation thread.
+ * @remarks Made visible for implementing vmsvga sync register.
+ * @internal
+ */
+VMMR3_INT_DECL(int) VMR3WaitHalted(PVM pVM, PVMCPU pVCpu, bool fIgnoreInterrupts)
+{
+    LogFlow(("VMR3WaitHalted: fIgnoreInterrupts=%d\n", fIgnoreInterrupts));
+
+    /*
+     * Check Relevant FFs.
+     */
+    const uint32_t fMask = !fIgnoreInterrupts
+        ? VMCPU_FF_EXTERNAL_HALTED_MASK
+        : VMCPU_FF_EXTERNAL_HALTED_MASK & ~(VMCPU_FF_UPDATE_APIC | VMCPU_FF_INTERRUPT_APIC | VMCPU_FF_INTERRUPT_PIC);
+    if (    VM_FF_IS_ANY_SET(pVM, VM_FF_EXTERNAL_HALTED_MASK)
+        ||  VMCPU_FF_IS_ANY_SET(pVCpu, fMask))
+    {
+        LogFlow(("VMR3WaitHalted: returns VINF_SUCCESS (FF %#x FFCPU %#RX64)\n", pVM->fGlobalForcedActions, (uint64_t)pVCpu->fLocalForcedActions));
+        return VINF_SUCCESS;
+    }
+
+    /*
+     * The yielder is suspended while we're halting, while TM might have clock(s) running
+     * only at certain times and need to be notified..
+     */
+    if (pVCpu->idCpu == 0)
+        VMMR3YieldSuspend(pVM);
+    TMNotifyStartOfHalt(pVCpu);
+
+    /*
+     * Record halt averages for the last second.
+     */
+    PUVMCPU pUVCpu = pVCpu->pUVCpu;
+    uint64_t u64Now = RTTimeNanoTS();
+    int64_t off = u64Now - pUVCpu->vm.s.u64HaltsStartTS;
+    if (off > 1000000000)
+    {
+        if (off > _4G || !pUVCpu->vm.s.cHalts)
+        {
+            pUVCpu->vm.s.HaltInterval = 1000000000 /* 1 sec */;
+            pUVCpu->vm.s.HaltFrequency = 1;
+        }
+        else
+        {
+            pUVCpu->vm.s.HaltInterval = (uint32_t)off / pUVCpu->vm.s.cHalts;
+            pUVCpu->vm.s.HaltFrequency = ASMMultU64ByU32DivByU32(pUVCpu->vm.s.cHalts, 1000000000, (uint32_t)off);
+        }
+        pUVCpu->vm.s.u64HaltsStartTS = u64Now;
+        pUVCpu->vm.s.cHalts = 0;
+    }
+    pUVCpu->vm.s.cHalts++;
+
+    /*
+     * Do the halt.
+     */
+    VMCPU_ASSERT_STATE_2(pVCpu, VMCPUSTATE_STARTED, VMCPUSTATE_STARTED_EXEC_NEM);
+    VMCPUSTATE enmStateOld = VMCPU_GET_STATE(pVCpu);
+    VMCPU_SET_STATE(pVCpu, VMCPUSTATE_STARTED_HALTED);
+    PUVM pUVM = pUVCpu->pUVM;
+    int rc = g_aHaltMethods[pUVM->vm.s.iHaltMethod].pfnHalt(pUVCpu, fMask, u64Now);
+    VMCPU_SET_STATE(pVCpu, enmStateOld);
+
+    /*
+     * Notify TM and resume the yielder
+     */
+    TMNotifyEndOfHalt(pVCpu);
+    if (pVCpu->idCpu == 0)
+        VMMR3YieldResume(pVM);
+
+    LogFlow(("VMR3WaitHalted: returns %Rrc (FF %#x)\n", rc, pVM->fGlobalForcedActions));
+    return rc;
+}
+
+
+/**
+ * Suspended VM Wait.
+ * Only a handful of forced actions will cause the function to
+ * return to the caller.
+ *
+ * @returns VINF_SUCCESS unless a fatal error occurred. In the latter
+ *          case an appropriate status code is returned.
+ * @param   pUVCpu          Pointer to the user mode VMCPU structure.
+ * @thread  The emulation thread.
+ * @internal
+ */
+VMMR3_INT_DECL(int) VMR3WaitU(PUVMCPU pUVCpu)
+{
+    LogFlow(("VMR3WaitU:\n"));
+
+    /*
+     * Check Relevant FFs.
+     */
+    PVM    pVM   = pUVCpu->pVM;
+    PVMCPU pVCpu = pUVCpu->pVCpu;
+
+    if (    pVM
+        &&  (   VM_FF_IS_ANY_SET(pVM, VM_FF_EXTERNAL_SUSPENDED_MASK)
+             || VMCPU_FF_IS_ANY_SET(pVCpu, VMCPU_FF_EXTERNAL_SUSPENDED_MASK)
+            )
+        )
+    {
+        LogFlow(("VMR3Wait: returns VINF_SUCCESS (FF %#x)\n", pVM->fGlobalForcedActions));
+        return VINF_SUCCESS;
+    }
+
+    /*
+     * Do waiting according to the halt method (so VMR3NotifyFF
+     * doesn't have to special case anything).
+     */
+    PUVM pUVM = pUVCpu->pUVM;
+    int rc = g_aHaltMethods[pUVM->vm.s.iHaltMethod].pfnWait(pUVCpu);
+    LogFlow(("VMR3WaitU: returns %Rrc (FF %#x)\n", rc, pUVM->pVM ? pUVM->pVM->fGlobalForcedActions : 0));
+    return rc;
+}
+
+
+/**
+ * Interface that PDMR3Suspend, PDMR3PowerOff and PDMR3Reset uses when they wait
+ * for the handling of asynchronous notifications to complete.
+ *
+ * @returns VINF_SUCCESS unless a fatal error occurred. In the latter
+ *          case an appropriate status code is returned.
+ * @param   pUVCpu              Pointer to the user mode VMCPU structure.
+ * @thread  The emulation thread.
+ */
+VMMR3_INT_DECL(int) VMR3AsyncPdmNotificationWaitU(PUVMCPU pUVCpu)
+{
+    LogFlow(("VMR3AsyncPdmNotificationWaitU:\n"));
+    return VMR3WaitU(pUVCpu);
+}
+
+
+/**
+ * Interface that PDM the helper asynchronous notification completed methods
+ * uses for EMT0 when it is waiting inside VMR3AsyncPdmNotificationWaitU().
+ *
+ * @param   pUVM                Pointer to the user mode VM structure.
+ */
+VMMR3_INT_DECL(void) VMR3AsyncPdmNotificationWakeupU(PUVM pUVM)
+{
+    LogFlow(("VMR3AsyncPdmNotificationWakeupU:\n"));
+    VM_FF_SET(pUVM->pVM, VM_FF_REQUEST); /* this will have to do for now. */
+    g_aHaltMethods[pUVM->vm.s.iHaltMethod].pfnNotifyCpuFF(&pUVM->aCpus[0], 0 /*fFlags*/);
+}
+
+
+/**
+ * Rendezvous callback that will be called once.
+ *
+ * @returns VBox strict status code.
+ * @param   pVM                 The cross context VM structure.
+ * @param   pVCpu               The cross context virtual CPU structure of the calling EMT.
+ * @param   pvUser              The new g_aHaltMethods index.
+ */
+static DECLCALLBACK(VBOXSTRICTRC) vmR3SetHaltMethodCallback(PVM pVM, PVMCPU pVCpu, void *pvUser)
+{
+    PUVM      pUVM = pVM->pUVM;
+    int       rc   = VINF_SUCCESS;
+    uintptr_t i    = (uintptr_t)pvUser;
+    Assert(i < RT_ELEMENTS(g_aHaltMethods));
+
+    /*
+     * Main job is done once on EMT0 (it goes thru here first).
+     */
+    if (pVCpu->idCpu == 0)
+    {
+        /*
+         * Terminate the old one.
+         */
+        if (    pUVM->vm.s.enmHaltMethod != VMHALTMETHOD_INVALID
+            &&  g_aHaltMethods[pUVM->vm.s.iHaltMethod].pfnTerm)
+        {
+            g_aHaltMethods[pUVM->vm.s.iHaltMethod].pfnTerm(pUVM);
+            pUVM->vm.s.enmHaltMethod = VMHALTMETHOD_INVALID;
+        }
+
+        /* Assert that the failure fallback is where we expect. */
+        Assert(g_aHaltMethods[0].enmHaltMethod == VMHALTMETHOD_BOOTSTRAP);
+        Assert(!g_aHaltMethods[0].pfnTerm && !g_aHaltMethods[0].pfnInit);
+
+        /*
+         * Init the new one.
+         */
+        memset(&pUVM->vm.s.Halt, 0, sizeof(pUVM->vm.s.Halt));
+        if (g_aHaltMethods[i].pfnInit)
+        {
+            rc = g_aHaltMethods[i].pfnInit(pUVM);
+            if (RT_FAILURE(rc))
+            {
+                /* Fall back on the bootstrap method. This requires no
+                   init/term (see assertion above), and will always work. */
+                AssertLogRelRC(rc);
+                i = 0;
+            }
+        }
+
+        /*
+         * Commit it.
+         */
+        pUVM->vm.s.enmHaltMethod = g_aHaltMethods[i].enmHaltMethod;
+        ASMAtomicWriteU32(&pUVM->vm.s.iHaltMethod, i);
+    }
+    else
+        i = pUVM->vm.s.iHaltMethod;
+
+    /*
+     * All EMTs must update their ring-0 halt configuration.
+     */
+    VMMR3SetMayHaltInRing0(pVCpu, g_aHaltMethods[i].fMayHaltInRing0,
+                           g_aHaltMethods[i].enmHaltMethod == VMHALTMETHOD_GLOBAL_1
+                           ? pUVM->vm.s.Halt.Global1.cNsSpinBlockThresholdCfg : 0);
+
+    return rc;
+}
+
+
+/**
+ * Changes the halt method.
+ *
+ * @returns VBox status code.
+ * @param   pUVM            Pointer to the user mode VM structure.
+ * @param   enmHaltMethod   The new halt method.
+ * @thread  EMT.
+ */
+int vmR3SetHaltMethodU(PUVM pUVM, VMHALTMETHOD enmHaltMethod)
+{
+    PVM pVM = pUVM->pVM; Assert(pVM);
+    VM_ASSERT_EMT(pVM);
+    AssertReturn(enmHaltMethod > VMHALTMETHOD_INVALID && enmHaltMethod < VMHALTMETHOD_END, VERR_INVALID_PARAMETER);
+
+    /*
+     * Resolve default (can be overridden in the configuration).
+     */
+    if (enmHaltMethod == VMHALTMETHOD_DEFAULT)
+    {
+        uint32_t u32;
+        int rc = CFGMR3QueryU32(CFGMR3GetChild(CFGMR3GetRoot(pVM), "VM"), "HaltMethod", &u32);
+        if (RT_SUCCESS(rc))
+        {
+            enmHaltMethod = (VMHALTMETHOD)u32;
+            if (enmHaltMethod <= VMHALTMETHOD_INVALID || enmHaltMethod >= VMHALTMETHOD_END)
+                return VMSetError(pVM, VERR_INVALID_PARAMETER, RT_SRC_POS, N_("Invalid VM/HaltMethod value %d"), enmHaltMethod);
+        }
+        else if (rc == VERR_CFGM_VALUE_NOT_FOUND || rc == VERR_CFGM_CHILD_NOT_FOUND)
+            return VMSetError(pVM, rc, RT_SRC_POS, N_("Failed to Query VM/HaltMethod as uint32_t"));
+        else
+            enmHaltMethod = VMHALTMETHOD_GLOBAL_1;
+            //enmHaltMethod = VMHALTMETHOD_1;
+            //enmHaltMethod = VMHALTMETHOD_OLD;
+    }
+
+    /*
+     * The global halt method doesn't work in driverless mode, so fall back on
+     * method #1 instead.
+     */
+    if (!SUPR3IsDriverless() || enmHaltMethod != VMHALTMETHOD_GLOBAL_1)
+        LogRel(("VMEmt: Halt method %s (%d)\n", vmR3GetHaltMethodName(enmHaltMethod), enmHaltMethod));
+    else
+    {
+        LogRel(("VMEmt: Halt method %s (%d) not available in driverless mode, using %s (%d) instead\n",
+                vmR3GetHaltMethodName(enmHaltMethod), enmHaltMethod, vmR3GetHaltMethodName(VMHALTMETHOD_1), VMHALTMETHOD_1));
+        enmHaltMethod = VMHALTMETHOD_1;
+    }
+
+
+    /*
+     * Find the descriptor.
+     */
+    unsigned i = 0;
+    while (     i < RT_ELEMENTS(g_aHaltMethods)
+           &&   g_aHaltMethods[i].enmHaltMethod != enmHaltMethod)
+        i++;
+    AssertReturn(i < RT_ELEMENTS(g_aHaltMethods), VERR_INVALID_PARAMETER);
+
+    /*
+     * This needs to be done while the other EMTs are not sleeping or otherwise messing around.
+     */
+    return VMMR3EmtRendezvous(pVM, VMMEMTRENDEZVOUS_FLAGS_TYPE_ASCENDING, vmR3SetHaltMethodCallback, (void *)(uintptr_t)i);
+}
+
+
+/**
+ * Special interface for implementing a HLT-like port on a device.
+ *
+ * This can be called directly from device code, provide the device is trusted
+ * to access the VMM directly.  Since we may not have an accurate register set
+ * and the caller certainly shouldn't (device code does not access CPU
+ * registers), this function will return when interrupts are pending regardless
+ * of the actual EFLAGS.IF state.
+ *
+ * @returns VBox error status (never informational statuses).
+ * @param   pVM                 The cross context VM structure.
+ * @param   idCpu               The id of the calling EMT.
+ */
+VMMR3DECL(int) VMR3WaitForDeviceReady(PVM pVM, VMCPUID idCpu)
+{
+    /*
+     * Validate caller and resolve the CPU ID.
+     */
+    VM_ASSERT_VALID_EXT_RETURN(pVM, VERR_INVALID_VM_HANDLE);
+    AssertReturn(idCpu < pVM->cCpus, VERR_INVALID_CPU_ID);
+    PVMCPU pVCpu = pVM->apCpusR3[idCpu];
+    VMCPU_ASSERT_EMT_RETURN(pVCpu, VERR_VM_THREAD_NOT_EMT);
+
+    /*
+     * Tag along with the HLT mechanics for now.
+     */
+    int rc = VMR3WaitHalted(pVM, pVCpu, false /*fIgnoreInterrupts*/);
+    if (RT_SUCCESS(rc))
+        return VINF_SUCCESS;
+    return rc;
+}
+
+
+/**
+ * Wakes up a CPU that has called VMR3WaitForDeviceReady.
+ *
+ * @returns VBox error status (never informational statuses).
+ * @param   pVM                 The cross context VM structure.
+ * @param   idCpu               The id of the calling EMT.
+ */
+VMMR3DECL(int) VMR3NotifyCpuDeviceReady(PVM pVM, VMCPUID idCpu)
+{
+    /*
+     * Validate caller and resolve the CPU ID.
+     */
+    VM_ASSERT_VALID_EXT_RETURN(pVM, VERR_INVALID_VM_HANDLE);
+    AssertReturn(idCpu < pVM->cCpus, VERR_INVALID_CPU_ID);
+    PVMCPU pVCpu = pVM->apCpusR3[idCpu];
+
+    /*
+     * Pretend it was an FF that got set since we've got logic for that already.
+     */
+    VMR3NotifyCpuFFU(pVCpu->pUVCpu, VMNOTIFYFF_FLAGS_DONE_REM);
+    return VINF_SUCCESS;
+}
+
+
+/**
+ * Returns the number of active EMTs.
+ *
+ * This is used by the rendezvous code during VM destruction to avoid waiting
+ * for EMTs that aren't around any more.
+ *
+ * @returns Number of active EMTs.  0 if invalid parameter.
+ * @param   pUVM                The user mode VM structure.
+ */
+VMMR3_INT_DECL(uint32_t) VMR3GetActiveEmts(PUVM pUVM)
+{
+    UVM_ASSERT_VALID_EXT_RETURN(pUVM, 0);
+    return pUVM->vm.s.cActiveEmts;
+}
+