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, 3038 insertions, 0 deletions

diff --git a/src/VBox/Main/src-client/HGCM.cpp b/src/VBox/Main/src-client/HGCM.cpp
new file mode 100644
index 00000000..4650ca35
--- /dev/null
+++ b/src/VBox/Main/src-client/HGCM.cpp
@@ -0,0 +1,3038 @@
+/* $Id: HGCM.cpp $ */
+/** @file
+ * HGCM (Host-Guest Communication Manager)
+ */
+
+/*
+ * 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
+ */
+
+#define LOG_GROUP LOG_GROUP_HGCM
+#include "LoggingNew.h"
+
+#include "HGCM.h"
+#include "HGCMThread.h"
+
+#include <VBox/err.h>
+#include <VBox/hgcmsvc.h>
+#include <VBox/vmm/ssm.h>
+#include <VBox/vmm/stam.h>
+#include <VBox/vmm/vmmr3vtable.h>
+#include <VBox/sup.h>
+#include <VBox/AssertGuest.h>
+
+#include <iprt/alloc.h>
+#include <iprt/avl.h>
+#include <iprt/critsect.h>
+#include <iprt/asm.h>
+#include <iprt/ldr.h>
+#include <iprt/param.h>
+#include <iprt/path.h>
+#include <iprt/string.h>
+#include <iprt/semaphore.h>
+#include <iprt/thread.h>
+
+#include <VBox/VMMDev.h>
+#include <new>
+
+/**
+ * A service gets one thread, which synchronously delivers messages to
+ * the service. This is good for serialization.
+ *
+ * Some services may want to process messages asynchronously, and will want
+ * a next message to be delivered, while a previous message is still being
+ * processed.
+ *
+ * The dedicated service thread delivers a next message when service
+ * returns after fetching a previous one. The service will call a message
+ * completion callback when message is actually processed. So returning
+ * from the service call means only that the service is processing message.
+ *
+ * 'Message processed' condition is indicated by service, which call the
+ * callback, even if the callback is called synchronously in the dedicated
+ * thread.
+ *
+ * This message completion callback is only valid for Call requests.
+ * Connect and Disconnect are processed synchronously by the service.
+ */
+
+
+/* The maximum allowed size of a service name in bytes. */
+#define VBOX_HGCM_SVC_NAME_MAX_BYTES 1024
+
+struct _HGCMSVCEXTHANDLEDATA
+{
+    char *pszServiceName;
+    /* The service name follows. */
+};
+
+class HGCMClient;
+
+/** Internal helper service object. HGCM code would use it to
+ *  hold information about services and communicate with services.
+ *  The HGCMService is an (in future) abstract class that implements
+ *  common functionality. There will be derived classes for specific
+ *  service types.
+ */
+
+class HGCMService
+{
+    private:
+        VBOXHGCMSVCHELPERS m_svcHelpers;
+
+        static HGCMService *sm_pSvcListHead;
+        static HGCMService *sm_pSvcListTail;
+
+        static int sm_cServices;
+
+        HGCMThread *m_pThread;
+        friend DECLCALLBACK(void) hgcmServiceThread(HGCMThread *pThread, void *pvUser);
+
+        uint32_t volatile m_u32RefCnt;
+
+        HGCMService *m_pSvcNext;
+        HGCMService *m_pSvcPrev;
+
+        char *m_pszSvcName;
+        char *m_pszSvcLibrary;
+
+        RTLDRMOD m_hLdrMod;
+        PFNVBOXHGCMSVCLOAD m_pfnLoad;
+
+        VBOXHGCMSVCFNTABLE m_fntable;
+
+        /** Set if servicing SVC_MSG_CONNECT or SVC_MSG_DISCONNECT.
+         * Used for context checking pfnDisconnectClient calls, as it can only
+         * safely be made when the main HGCM thread is waiting on the service to
+         * process those messages. */
+        bool m_fInConnectOrDisconnect;
+
+        uint32_t m_acClients[HGCM_CLIENT_CATEGORY_MAX]; /**< Clients per category. */
+        uint32_t m_cClients;
+        uint32_t m_cClientsAllocated;
+
+        uint32_t *m_paClientIds;
+
+        HGCMSVCEXTHANDLE m_hExtension;
+
+        PUVM m_pUVM;
+        PCVMMR3VTABLE m_pVMM;
+        PPDMIHGCMPORT m_pHgcmPort;
+
+        /** @name Statistics
+         * @{ */
+        STAMPROFILE m_StatHandleMsg;
+        STAMCOUNTER m_StatTooManyClients;
+        STAMCOUNTER m_StatTooManyCalls;
+        /** @} */
+
+        int loadServiceDLL(void);
+        void unloadServiceDLL(void);
+
+        /*
+         * Main HGCM thread methods.
+         */
+        int instanceCreate(const char *pszServiceLibrary, const char *pszServiceName,
+                           PUVM pUVM, PCVMMR3VTABLE pVMM, PPDMIHGCMPORT pHgcmPort);
+        void registerStatistics(const char *pszServiceName, PUVM pUVM, PCVMMR3VTABLE pVMM);
+        void instanceDestroy(void);
+
+        int saveClientState(uint32_t u32ClientId, PSSMHANDLE pSSM, PCVMMR3VTABLE pVMM);
+        int loadClientState(uint32_t u32ClientId, PSSMHANDLE pSSM, PCVMMR3VTABLE pVMM, uint32_t uVersion);
+
+        HGCMService();
+        ~HGCMService() {};
+
+        static DECLCALLBACK(int)  svcHlpCallComplete(VBOXHGCMCALLHANDLE callHandle, int32_t vrc);
+        static DECLCALLBACK(int)  svcHlpDisconnectClient(void *pvInstance, uint32_t idClient);
+        static DECLCALLBACK(bool) svcHlpIsCallRestored(VBOXHGCMCALLHANDLE callHandle);
+        static DECLCALLBACK(bool) svcHlpIsCallCancelled(VBOXHGCMCALLHANDLE callHandle);
+        static DECLCALLBACK(int)  svcHlpStamRegisterV(void *pvInstance, void *pvSample, STAMTYPE enmType,
+                                                      STAMVISIBILITY enmVisibility, STAMUNIT enmUnit, const char *pszDesc,
+                                                      const char *pszName, va_list va);
+        static DECLCALLBACK(int)  svcHlpStamDeregisterV(void *pvInstance, const char *pszPatFmt, va_list va);
+        static DECLCALLBACK(int)  svcHlpInfoRegister(void *pvInstance, const char *pszName, const char *pszDesc,
+                                                     PFNDBGFHANDLEREXT pfnHandler, void *pvUser);
+        static DECLCALLBACK(int)  svcHlpInfoDeregister(void *pvInstance, const char *pszName);
+        static DECLCALLBACK(uint32_t) svcHlpGetRequestor(VBOXHGCMCALLHANDLE hCall);
+        static DECLCALLBACK(uint64_t) svcHlpGetVMMDevSessionId(void *pvInstance);
+
+    public:
+
+        /*
+         * Main HGCM thread methods.
+         */
+        static int LoadService(const char *pszServiceLibrary, const char *pszServiceName,
+                               PUVM pUVM, PCVMMR3VTABLE pVMM, PPDMIHGCMPORT pHgcmPort);
+        void UnloadService(bool fUvmIsInvalid);
+
+        static void UnloadAll(bool fUvmIsInvalid);
+
+        static int ResolveService(HGCMService **ppsvc, const char *pszServiceName);
+        void ReferenceService(void);
+        void ReleaseService(void);
+
+        static void Reset(void);
+
+        static int SaveState(PSSMHANDLE pSSM, PCVMMR3VTABLE pVMM);
+        static int LoadState(PSSMHANDLE pSSM, PCVMMR3VTABLE pVMM, uint32_t uVersion);
+
+        int CreateAndConnectClient(uint32_t *pu32ClientIdOut, uint32_t u32ClientIdIn, uint32_t fRequestor, bool fRestoring);
+        int DisconnectClient(uint32_t u32ClientId, bool fFromService, HGCMClient *pClient);
+
+        int HostCall(uint32_t u32Function, uint32_t cParms, VBOXHGCMSVCPARM *paParms);
+        static void BroadcastNotify(HGCMNOTIFYEVENT enmEvent);
+        void Notify(HGCMNOTIFYEVENT enmEvent);
+
+        uint32_t SizeOfClient(void) { return m_fntable.cbClient; };
+
+        int RegisterExtension(HGCMSVCEXTHANDLE handle, PFNHGCMSVCEXT pfnExtension, void *pvExtension);
+        void UnregisterExtension(HGCMSVCEXTHANDLE handle);
+
+        /*
+         * The service thread methods.
+         */
+
+        int GuestCall(PPDMIHGCMPORT pHGCMPort, PVBOXHGCMCMD pCmd, uint32_t u32ClientId, HGCMClient *pClient,
+                      uint32_t u32Function, uint32_t cParms, VBOXHGCMSVCPARM aParms[], uint64_t tsArrival);
+        void GuestCancelled(PPDMIHGCMPORT pHGCMPort, PVBOXHGCMCMD pCmd, uint32_t idClient);
+};
+
+
+class HGCMClient: public HGCMObject
+{
+    public:
+        HGCMClient(uint32_t a_fRequestor, uint32_t a_idxCategory)
+            : HGCMObject(HGCMOBJ_CLIENT)
+            , pService(NULL)
+            , pvData(NULL)
+            , fRequestor(a_fRequestor)
+            , idxCategory(a_idxCategory)
+            , cPendingCalls(0)
+            , m_fGuestAccessible(false)
+        {
+            Assert(idxCategory < HGCM_CLIENT_CATEGORY_MAX);
+        }
+        ~HGCMClient();
+
+        int Init(HGCMService *pSvc);
+
+        /** Lookups a client object by its handle. */
+        static HGCMClient *ReferenceByHandle(uint32_t idClient)
+        {
+            return (HGCMClient *)hgcmObjReference(idClient, HGCMOBJ_CLIENT);
+        }
+
+        /** Lookups a client object by its handle and makes sure that it's accessible to the guest. */
+        static HGCMClient *ReferenceByHandleForGuest(uint32_t idClient)
+        {
+            HGCMClient *pClient = (HGCMClient *)hgcmObjReference(idClient, HGCMOBJ_CLIENT);
+            if (pClient)
+            {
+                if (RT_LIKELY(pClient->m_fGuestAccessible))
+                    return pClient;
+                pClient->Dereference();
+            }
+            return NULL;
+        }
+
+        /** Make the client object accessible to the guest. */
+        void makeAccessibleToGuest()
+        {
+            ASMAtomicWriteBool(&m_fGuestAccessible, true);
+        }
+
+        /** Service that the client is connected to. */
+        HGCMService *pService;
+
+        /** Client specific data. */
+        void *pvData;
+
+        /** The requestor flags this client was created with.
+         * @sa VMMDevRequestHeader::fRequestor */
+        uint32_t fRequestor;
+
+        /** The client category (HGCM_CLIENT_CATEGORY_XXX). */
+        uint32_t idxCategory;
+
+        /** Number of pending calls. */
+        uint32_t volatile cPendingCalls;
+
+    protected:
+        /** Set if the client is accessible to the guest, clear if not. */
+        bool volatile m_fGuestAccessible;
+
+    private: /* none of this: */
+        HGCMClient();
+        HGCMClient(HGCMClient const &);
+        HGCMClient &operator=(HGCMClient const &);
+};
+
+HGCMClient::~HGCMClient()
+{
+    if (pService->SizeOfClient() > 0)
+    {
+        RTMemFree(pvData);
+        pvData = NULL;
+    }
+}
+
+
+int HGCMClient::Init(HGCMService *pSvc)
+{
+    pService = pSvc;
+
+    if (pService->SizeOfClient() > 0)
+    {
+        pvData = RTMemAllocZ(pService->SizeOfClient());
+
+        if (!pvData)
+        {
+           return VERR_NO_MEMORY;
+        }
+    }
+
+    return VINF_SUCCESS;
+}
+
+
+#define HGCM_CLIENT_DATA(pService, pClient)(pClient->pvData)
+
+
+
+HGCMService *HGCMService::sm_pSvcListHead = NULL;
+HGCMService *HGCMService::sm_pSvcListTail = NULL;
+int HGCMService::sm_cServices = 0;
+
+HGCMService::HGCMService()
+    :
+    m_pThread    (NULL),
+    m_u32RefCnt  (0),
+    m_pSvcNext   (NULL),
+    m_pSvcPrev   (NULL),
+    m_pszSvcName (NULL),
+    m_pszSvcLibrary (NULL),
+    m_hLdrMod    (NIL_RTLDRMOD),
+    m_pfnLoad    (NULL),
+    m_fInConnectOrDisconnect(false),
+    m_cClients   (0),
+    m_cClientsAllocated (0),
+    m_paClientIds (NULL),
+    m_hExtension (NULL),
+    m_pUVM       (NULL),
+    m_pVMM       (NULL),
+    m_pHgcmPort  (NULL)
+{
+    RT_ZERO(m_acClients);
+    RT_ZERO(m_fntable);
+}
+
+
+static bool g_fResetting = false;
+static bool g_fSaveState = false;
+
+
+/** Helper function to load a local service DLL.
+ *
+ *  @return VBox code
+ */
+int HGCMService::loadServiceDLL(void)
+{
+    LogFlowFunc(("m_pszSvcLibrary = %s\n", m_pszSvcLibrary));
+
+    if (m_pszSvcLibrary == NULL)
+    {
+        return VERR_INVALID_PARAMETER;
+    }
+
+    RTERRINFOSTATIC ErrInfo;
+    RTErrInfoInitStatic(&ErrInfo);
+
+    int vrc;
+
+    if (RTPathHasPath(m_pszSvcLibrary))
+        vrc = SUPR3HardenedLdrLoadPlugIn(m_pszSvcLibrary, &m_hLdrMod, &ErrInfo.Core);
+    else
+        vrc = SUPR3HardenedLdrLoadAppPriv(m_pszSvcLibrary, &m_hLdrMod, RTLDRLOAD_FLAGS_LOCAL, &ErrInfo.Core);
+
+    if (RT_SUCCESS(vrc))
+    {
+        LogFlowFunc(("successfully loaded the library.\n"));
+
+        m_pfnLoad = NULL;
+
+        vrc = RTLdrGetSymbol(m_hLdrMod, VBOX_HGCM_SVCLOAD_NAME, (void**)&m_pfnLoad);
+
+        if (RT_FAILURE(vrc) || !m_pfnLoad)
+        {
+            Log(("HGCMService::loadServiceDLL: Error resolving the service entry point %s, vrc = %Rrc, m_pfnLoad = %p\n",
+                 VBOX_HGCM_SVCLOAD_NAME, vrc, m_pfnLoad));
+
+            if (RT_SUCCESS(vrc))
+            {
+                /* m_pfnLoad was NULL */
+                vrc = VERR_SYMBOL_NOT_FOUND;
+            }
+        }
+
+        if (RT_SUCCESS(vrc))
+        {
+            RT_ZERO(m_fntable);
+
+            m_fntable.cbSize     = sizeof(m_fntable);
+            m_fntable.u32Version = VBOX_HGCM_SVC_VERSION;
+            m_fntable.pHelpers   = &m_svcHelpers;
+
+            /*  Total max calls: (2048 + 1024 + 1024) * 8192 = 33 554 432 */
+            m_fntable.idxLegacyClientCategory = HGCM_CLIENT_CATEGORY_KERNEL;
+            m_fntable.acMaxClients[HGCM_CLIENT_CATEGORY_KERNEL] = _2K;
+            m_fntable.acMaxClients[HGCM_CLIENT_CATEGORY_ROOT]   = _1K;
+            m_fntable.acMaxClients[HGCM_CLIENT_CATEGORY_USER]   = _1K;
+            m_fntable.acMaxCallsPerClient[HGCM_CLIENT_CATEGORY_KERNEL] = _8K;
+            m_fntable.acMaxCallsPerClient[HGCM_CLIENT_CATEGORY_ROOT]   = _4K;
+            m_fntable.acMaxCallsPerClient[HGCM_CLIENT_CATEGORY_USER]   = _2K;
+            /** @todo provide way to configure different values via extra data.   */
+
+            vrc = m_pfnLoad(&m_fntable);
+
+            LogFlowFunc(("m_pfnLoad vrc = %Rrc\n", vrc));
+
+            if (RT_SUCCESS(vrc))
+            {
+                if (   m_fntable.pfnUnload != NULL
+                    && m_fntable.pfnConnect != NULL
+                    && m_fntable.pfnDisconnect != NULL
+                    && m_fntable.pfnCall != NULL
+                   )
+                {
+                    Assert(m_fntable.idxLegacyClientCategory < RT_ELEMENTS(m_fntable.acMaxClients));
+                    LogRel2(("HGCMService::loadServiceDLL: acMaxClients={%u,%u,%u} acMaxCallsPerClient={%u,%u,%u} => %RU64 calls; idxLegacyClientCategory=%d; %s\n",
+                             m_fntable.acMaxClients[HGCM_CLIENT_CATEGORY_KERNEL],
+                             m_fntable.acMaxClients[HGCM_CLIENT_CATEGORY_ROOT],
+                             m_fntable.acMaxClients[HGCM_CLIENT_CATEGORY_USER],
+                             m_fntable.acMaxCallsPerClient[HGCM_CLIENT_CATEGORY_KERNEL],
+                             m_fntable.acMaxCallsPerClient[HGCM_CLIENT_CATEGORY_ROOT],
+                             m_fntable.acMaxCallsPerClient[HGCM_CLIENT_CATEGORY_USER],
+                                 (uint64_t)m_fntable.acMaxClients[HGCM_CLIENT_CATEGORY_KERNEL]
+                               *    m_fntable.acMaxCallsPerClient[HGCM_CLIENT_CATEGORY_KERNEL]
+                             +   (uint64_t)m_fntable.acMaxClients[HGCM_CLIENT_CATEGORY_ROOT]
+                               *    m_fntable.acMaxCallsPerClient[HGCM_CLIENT_CATEGORY_ROOT]
+                             +   (uint64_t)m_fntable.acMaxClients[HGCM_CLIENT_CATEGORY_USER]
+                               *    m_fntable.acMaxCallsPerClient[HGCM_CLIENT_CATEGORY_USER],
+                             m_fntable.idxLegacyClientCategory, m_pszSvcName));
+                }
+                else
+                {
+                    Log(("HGCMService::loadServiceDLL: at least one of function pointers is NULL\n"));
+
+                    vrc = VERR_INVALID_PARAMETER;
+
+                    if (m_fntable.pfnUnload)
+                    {
+                        m_fntable.pfnUnload(m_fntable.pvService);
+                    }
+                }
+            }
+        }
+    }
+    else
+    {
+        LogRel(("HGCM: Failed to load the service library: [%s], vrc = %Rrc - %s. The service will be not available.\n",
+                m_pszSvcLibrary, vrc, ErrInfo.Core.pszMsg));
+        m_hLdrMod = NIL_RTLDRMOD;
+    }
+
+    if (RT_FAILURE(vrc))
+    {
+        unloadServiceDLL();
+    }
+
+    return vrc;
+}
+
+/**
+ * Helper function to free a local service DLL.
+ */
+void HGCMService::unloadServiceDLL(void)
+{
+    if (m_hLdrMod)
+    {
+        RTLdrClose(m_hLdrMod);
+    }
+
+    RT_ZERO(m_fntable);
+    m_pfnLoad = NULL;
+    m_hLdrMod = NIL_RTLDRMOD;
+}
+
+/*
+ * Messages processed by service threads. These threads only call the service entry points.
+ */
+
+#define SVC_MSG_LOAD            (0)  /**< Load the service library and call VBOX_HGCM_SVCLOAD_NAME entry point. */
+#define SVC_MSG_UNLOAD          (1)  /**< call pfnUnload and unload the service library. */
+#define SVC_MSG_CONNECT         (2)  /**< pfnConnect */
+#define SVC_MSG_DISCONNECT      (3)  /**< pfnDisconnect */
+#define SVC_MSG_GUESTCALL       (4)  /**< pfnGuestCall */
+#define SVC_MSG_HOSTCALL        (5)  /**< pfnHostCall */
+#define SVC_MSG_LOADSTATE       (6)  /**< pfnLoadState. */
+#define SVC_MSG_SAVESTATE       (7)  /**< pfnSaveState. */
+#define SVC_MSG_QUIT            (8)  /**< Terminate the thread. */
+#define SVC_MSG_REGEXT          (9)  /**< pfnRegisterExtension */
+#define SVC_MSG_UNREGEXT        (10) /**< pfnRegisterExtension */
+#define SVC_MSG_NOTIFY          (11) /**< pfnNotify */
+#define SVC_MSG_GUESTCANCELLED  (12) /**< pfnCancelled */
+
+class HGCMMsgSvcLoad: public HGCMMsgCore
+{
+    public:
+        HGCMMsgSvcLoad() : HGCMMsgCore(), pUVM() {}
+
+        /** The user mode VM handle (for statistics and such). */
+        PUVM pUVM;
+};
+
+class HGCMMsgSvcUnload: public HGCMMsgCore
+{
+};
+
+class HGCMMsgSvcConnect: public HGCMMsgCore
+{
+    public:
+        /** client identifier */
+        uint32_t u32ClientId;
+        /** Requestor flags. */
+        uint32_t fRequestor;
+        /** Set if restoring. */
+        bool fRestoring;
+};
+
+class HGCMMsgSvcDisconnect: public HGCMMsgCore
+{
+    public:
+        /** client identifier */
+        uint32_t u32ClientId;
+        /** The client instance. */
+        HGCMClient *pClient;
+};
+
+class HGCMMsgHeader: public HGCMMsgCore
+{
+    public:
+        HGCMMsgHeader() : pCmd(NULL), pHGCMPort(NULL) {};
+
+        /* Command pointer/identifier. */
+        PVBOXHGCMCMD pCmd;
+
+        /* Port to be informed on message completion. */
+        PPDMIHGCMPORT pHGCMPort;
+};
+
+class HGCMMsgCall: public HGCMMsgHeader
+{
+    public:
+        HGCMMsgCall() : pcCounter(NULL)
+        { }
+
+        HGCMMsgCall(HGCMThread *pThread)
+            : pcCounter(NULL)
+        {
+            InitializeCore(SVC_MSG_GUESTCALL, pThread);
+            Initialize();
+        }
+        ~HGCMMsgCall()
+        {
+            Log(("~HGCMMsgCall %p\n", this));
+            Assert(!pcCounter);
+        }
+
+        /** Points to HGCMClient::cPendingCalls if it needs to be decremented. */
+        uint32_t volatile *pcCounter;
+
+        /* client identifier */
+        uint32_t u32ClientId;
+
+        /* function number */
+        uint32_t u32Function;
+
+        /* number of parameters */
+        uint32_t cParms;
+
+        VBOXHGCMSVCPARM *paParms;
+
+        /** The STAM_GET_TS() value when the request arrived. */
+        uint64_t tsArrival;
+};
+
+class HGCMMsgCancelled: public HGCMMsgHeader
+{
+    public:
+        HGCMMsgCancelled() {}
+
+        HGCMMsgCancelled(HGCMThread *pThread)
+        {
+            InitializeCore(SVC_MSG_GUESTCANCELLED, pThread);
+            Initialize();
+        }
+        ~HGCMMsgCancelled() { Log(("~HGCMMsgCancelled %p\n", this)); }
+
+        /** The client identifier. */
+        uint32_t idClient;
+};
+
+class HGCMMsgLoadSaveStateClient: public HGCMMsgCore
+{
+    public:
+        PSSMHANDLE      pSSM;
+        PCVMMR3VTABLE   pVMM;
+        uint32_t        uVersion;
+        uint32_t        u32ClientId;
+};
+
+class HGCMMsgHostCallSvc: public HGCMMsgCore
+{
+    public:
+        /* function number */
+        uint32_t u32Function;
+
+        /* number of parameters */
+        uint32_t cParms;
+
+        VBOXHGCMSVCPARM *paParms;
+};
+
+class HGCMMsgSvcRegisterExtension: public HGCMMsgCore
+{
+    public:
+        /* Handle of the extension to be registered. */
+        HGCMSVCEXTHANDLE handle;
+        /* The extension entry point. */
+        PFNHGCMSVCEXT pfnExtension;
+        /* The extension pointer. */
+        void *pvExtension;
+};
+
+class HGCMMsgSvcUnregisterExtension: public HGCMMsgCore
+{
+    public:
+        /* Handle of the registered extension. */
+        HGCMSVCEXTHANDLE handle;
+};
+
+class HGCMMsgNotify: public HGCMMsgCore
+{
+    public:
+        /** The event. */
+        HGCMNOTIFYEVENT enmEvent;
+};
+
+static HGCMMsgCore *hgcmMessageAllocSvc(uint32_t u32MsgId)
+{
+    switch (u32MsgId)
+    {
+        case SVC_MSG_LOAD:        return new HGCMMsgSvcLoad();
+        case SVC_MSG_UNLOAD:      return new HGCMMsgSvcUnload();
+        case SVC_MSG_CONNECT:     return new HGCMMsgSvcConnect();
+        case SVC_MSG_DISCONNECT:  return new HGCMMsgSvcDisconnect();
+        case SVC_MSG_HOSTCALL:    return new HGCMMsgHostCallSvc();
+        case SVC_MSG_GUESTCALL:   return new HGCMMsgCall();
+        case SVC_MSG_LOADSTATE:
+        case SVC_MSG_SAVESTATE:   return new HGCMMsgLoadSaveStateClient();
+        case SVC_MSG_REGEXT:      return new HGCMMsgSvcRegisterExtension();
+        case SVC_MSG_UNREGEXT:    return new HGCMMsgSvcUnregisterExtension();
+        case SVC_MSG_NOTIFY:      return new HGCMMsgNotify();
+        case SVC_MSG_GUESTCANCELLED: return new HGCMMsgCancelled();
+        default:
+            AssertReleaseMsgFailed(("Msg id = %08X\n", u32MsgId));
+    }
+
+    return NULL;
+}
+
+/*
+ * The service thread. Loads the service library and calls the service entry points.
+ */
+DECLCALLBACK(void) hgcmServiceThread(HGCMThread *pThread, void *pvUser)
+{
+    HGCMService *pSvc = (HGCMService *)pvUser;
+    AssertRelease(pSvc != NULL);
+
+    bool fQuit = false;
+
+    while (!fQuit)
+    {
+        HGCMMsgCore *pMsgCore;
+        int vrc = hgcmMsgGet(pThread, &pMsgCore);
+
+        if (RT_FAILURE(vrc))
+        {
+            /* The error means some serious unrecoverable problem in the hgcmMsg/hgcmThread layer. */
+            AssertMsgFailed(("%Rrc\n", vrc));
+            break;
+        }
+
+        STAM_REL_PROFILE_START(&pSvc->m_StatHandleMsg, a);
+
+        /* Cache required information to avoid unnecessary pMsgCore access. */
+        uint32_t u32MsgId = pMsgCore->MsgId();
+
+        switch (u32MsgId)
+        {
+            case SVC_MSG_LOAD:
+            {
+                LogFlowFunc(("SVC_MSG_LOAD\n"));
+                vrc = pSvc->loadServiceDLL();
+            } break;
+
+            case SVC_MSG_UNLOAD:
+            {
+                LogFlowFunc(("SVC_MSG_UNLOAD\n"));
+                if (pSvc->m_fntable.pfnUnload)
+                {
+                    pSvc->m_fntable.pfnUnload(pSvc->m_fntable.pvService);
+                }
+
+                pSvc->unloadServiceDLL();
+                fQuit = true;
+            } break;
+
+            case SVC_MSG_CONNECT:
+            {
+                HGCMMsgSvcConnect *pMsg = (HGCMMsgSvcConnect *)pMsgCore;
+
+                LogFlowFunc(("SVC_MSG_CONNECT u32ClientId = %d\n", pMsg->u32ClientId));
+
+                HGCMClient *pClient = HGCMClient::ReferenceByHandle(pMsg->u32ClientId);
+
+                if (pClient)
+                {
+                    pSvc->m_fInConnectOrDisconnect = true;
+                    vrc = pSvc->m_fntable.pfnConnect(pSvc->m_fntable.pvService, pMsg->u32ClientId,
+                                                     HGCM_CLIENT_DATA(pSvc, pClient),
+                                                     pMsg->fRequestor, pMsg->fRestoring);
+                    pSvc->m_fInConnectOrDisconnect = false;
+
+                    hgcmObjDereference(pClient);
+                }
+                else
+                {
+                    vrc = VERR_HGCM_INVALID_CLIENT_ID;
+                }
+            } break;
+
+            case SVC_MSG_DISCONNECT:
+            {
+                HGCMMsgSvcDisconnect *pMsg = (HGCMMsgSvcDisconnect *)pMsgCore;
+
+                LogFlowFunc(("SVC_MSG_DISCONNECT u32ClientId = %d, pClient = %p\n", pMsg->u32ClientId, pMsg->pClient));
+
+                if (pMsg->pClient)
+                {
+                    pSvc->m_fInConnectOrDisconnect = true;
+                    vrc = pSvc->m_fntable.pfnDisconnect(pSvc->m_fntable.pvService, pMsg->u32ClientId,
+                                                        HGCM_CLIENT_DATA(pSvc, pMsg->pClient));
+                    pSvc->m_fInConnectOrDisconnect = false;
+                }
+                else
+                {
+                    vrc = VERR_HGCM_INVALID_CLIENT_ID;
+                }
+            } break;
+
+            case SVC_MSG_GUESTCALL:
+            {
+                HGCMMsgCall *pMsg = (HGCMMsgCall *)pMsgCore;
+
+                LogFlowFunc(("SVC_MSG_GUESTCALL u32ClientId = %d, u32Function = %d, cParms = %d, paParms = %p\n",
+                             pMsg->u32ClientId, pMsg->u32Function, pMsg->cParms, pMsg->paParms));
+
+                HGCMClient *pClient = HGCMClient::ReferenceByHandleForGuest(pMsg->u32ClientId);
+
+                if (pClient)
+                {
+                    pSvc->m_fntable.pfnCall(pSvc->m_fntable.pvService, (VBOXHGCMCALLHANDLE)pMsg, pMsg->u32ClientId,
+                                            HGCM_CLIENT_DATA(pSvc, pClient), pMsg->u32Function,
+                                            pMsg->cParms, pMsg->paParms, pMsg->tsArrival);
+
+                    hgcmObjDereference(pClient);
+                }
+                else
+                {
+                    vrc = VERR_HGCM_INVALID_CLIENT_ID;
+                }
+            } break;
+
+            case SVC_MSG_GUESTCANCELLED:
+            {
+                HGCMMsgCancelled *pMsg = (HGCMMsgCancelled *)pMsgCore;
+
+                LogFlowFunc(("SVC_MSG_GUESTCANCELLED idClient = %d\n", pMsg->idClient));
+
+                HGCMClient *pClient = HGCMClient::ReferenceByHandleForGuest(pMsg->idClient);
+
+                if (pClient)
+                {
+                    pSvc->m_fntable.pfnCancelled(pSvc->m_fntable.pvService, pMsg->idClient, HGCM_CLIENT_DATA(pSvc, pClient));
+
+                    hgcmObjDereference(pClient);
+                }
+                else
+                {
+                    vrc = VERR_HGCM_INVALID_CLIENT_ID;
+                }
+            } break;
+
+            case SVC_MSG_HOSTCALL:
+            {
+                HGCMMsgHostCallSvc *pMsg = (HGCMMsgHostCallSvc *)pMsgCore;
+
+                LogFlowFunc(("SVC_MSG_HOSTCALL u32Function = %d, cParms = %d, paParms = %p\n",
+                             pMsg->u32Function, pMsg->cParms, pMsg->paParms));
+
+                vrc = pSvc->m_fntable.pfnHostCall(pSvc->m_fntable.pvService, pMsg->u32Function, pMsg->cParms, pMsg->paParms);
+            } break;
+
+            case SVC_MSG_LOADSTATE:
+            {
+                HGCMMsgLoadSaveStateClient *pMsg = (HGCMMsgLoadSaveStateClient *)pMsgCore;
+
+                LogFlowFunc(("SVC_MSG_LOADSTATE\n"));
+
+                HGCMClient *pClient = HGCMClient::ReferenceByHandle(pMsg->u32ClientId);
+
+                if (pClient)
+                {
+                    /* fRequestor: Restored by the message sender already. */
+                    bool fHaveClientState = pSvc->m_fntable.pfnLoadState != NULL;
+                    if (pMsg->uVersion > HGCM_SAVED_STATE_VERSION_V2)
+                        vrc = pMsg->pVMM->pfnSSMR3GetBool(pMsg->pSSM, &fHaveClientState);
+                    else
+                        vrc = VINF_SUCCESS;
+                    if (RT_SUCCESS(vrc) )
+                    {
+                        if (pSvc->m_fntable.pfnLoadState)
+                            vrc = pSvc->m_fntable.pfnLoadState(pSvc->m_fntable.pvService, pMsg->u32ClientId,
+                                                               HGCM_CLIENT_DATA(pSvc, pClient), pMsg->pSSM, pMsg->pVMM,
+                                                               fHaveClientState ? pMsg->uVersion : 0);
+                        else
+                            AssertLogRelStmt(!fHaveClientState, vrc = VERR_INTERNAL_ERROR_5);
+                    }
+                    hgcmObjDereference(pClient);
+                }
+                else
+                {
+                    vrc = VERR_HGCM_INVALID_CLIENT_ID;
+                }
+            } break;
+
+            case SVC_MSG_SAVESTATE:
+            {
+                HGCMMsgLoadSaveStateClient *pMsg = (HGCMMsgLoadSaveStateClient *)pMsgCore;
+
+                LogFlowFunc(("SVC_MSG_SAVESTATE\n"));
+
+                HGCMClient *pClient = HGCMClient::ReferenceByHandle(pMsg->u32ClientId);
+
+                vrc = VINF_SUCCESS;
+
+                if (pClient)
+                {
+                    pMsg->pVMM->pfnSSMR3PutU32(pMsg->pSSM, pClient->fRequestor); /* Quicker to save this here than in the message sender. */
+                    vrc = pMsg->pVMM->pfnSSMR3PutBool(pMsg->pSSM, pSvc->m_fntable.pfnSaveState != NULL);
+                    if (RT_SUCCESS(vrc) && pSvc->m_fntable.pfnSaveState)
+                    {
+                        g_fSaveState = true;
+                        vrc = pSvc->m_fntable.pfnSaveState(pSvc->m_fntable.pvService, pMsg->u32ClientId,
+                                                           HGCM_CLIENT_DATA(pSvc, pClient), pMsg->pSSM, pMsg->pVMM);
+                        g_fSaveState = false;
+                    }
+
+                    hgcmObjDereference(pClient);
+                }
+                else
+                {
+                    vrc = VERR_HGCM_INVALID_CLIENT_ID;
+                }
+            } break;
+
+            case SVC_MSG_REGEXT:
+            {
+                HGCMMsgSvcRegisterExtension *pMsg = (HGCMMsgSvcRegisterExtension *)pMsgCore;
+
+                LogFlowFunc(("SVC_MSG_REGEXT handle = %p, pfn = %p\n", pMsg->handle, pMsg->pfnExtension));
+
+                if (pSvc->m_hExtension)
+                {
+                    vrc = VERR_NOT_SUPPORTED;
+                }
+                else
+                {
+                    if (pSvc->m_fntable.pfnRegisterExtension)
+                    {
+                        vrc = pSvc->m_fntable.pfnRegisterExtension(pSvc->m_fntable.pvService, pMsg->pfnExtension,
+                                                                   pMsg->pvExtension);
+                    }
+                    else
+                    {
+                        vrc = VERR_NOT_SUPPORTED;
+                    }
+
+                    if (RT_SUCCESS(vrc))
+                    {
+                        pSvc->m_hExtension = pMsg->handle;
+                    }
+                }
+            } break;
+
+            case SVC_MSG_UNREGEXT:
+            {
+                HGCMMsgSvcUnregisterExtension *pMsg = (HGCMMsgSvcUnregisterExtension *)pMsgCore;
+
+                LogFlowFunc(("SVC_MSG_UNREGEXT handle = %p\n", pMsg->handle));
+
+                if (pSvc->m_hExtension != pMsg->handle)
+                {
+                    vrc = VERR_NOT_SUPPORTED;
+                }
+                else
+                {
+                    if (pSvc->m_fntable.pfnRegisterExtension)
+                    {
+                        vrc = pSvc->m_fntable.pfnRegisterExtension(pSvc->m_fntable.pvService, NULL, NULL);
+                    }
+                    else
+                    {
+                        vrc = VERR_NOT_SUPPORTED;
+                    }
+
+                    pSvc->m_hExtension = NULL;
+                }
+            } break;
+
+            case SVC_MSG_NOTIFY:
+            {
+                HGCMMsgNotify *pMsg = (HGCMMsgNotify *)pMsgCore;
+
+                LogFlowFunc(("SVC_MSG_NOTIFY enmEvent = %d\n", pMsg->enmEvent));
+
+                pSvc->m_fntable.pfnNotify(pSvc->m_fntable.pvService, pMsg->enmEvent);
+            } break;
+
+            default:
+            {
+                AssertMsgFailed(("hgcmServiceThread::Unsupported message number %08X\n", u32MsgId));
+                vrc = VERR_NOT_SUPPORTED;
+            } break;
+        }
+
+        if (u32MsgId != SVC_MSG_GUESTCALL)
+        {
+            /* For SVC_MSG_GUESTCALL the service calls the completion helper.
+             * Other messages have to be completed here.
+             */
+            hgcmMsgComplete (pMsgCore, vrc);
+        }
+        STAM_REL_PROFILE_STOP(&pSvc->m_StatHandleMsg, a);
+    }
+}
+
+/**
+ * @interface_method_impl{VBOXHGCMSVCHELPERS,pfnCallComplete}
+ */
+/* static */ DECLCALLBACK(int) HGCMService::svcHlpCallComplete(VBOXHGCMCALLHANDLE callHandle, int32_t vrc)
+{
+   HGCMMsgCore *pMsgCore = (HGCMMsgCore *)callHandle;
+
+   /* Only call the completion for these messages. The helper
+    * is called by the service, and the service does not get
+    * any other messages.
+    */
+   AssertMsgReturn(pMsgCore->MsgId() == SVC_MSG_GUESTCALL, ("%d\n", pMsgCore->MsgId()), VERR_WRONG_TYPE);
+   return hgcmMsgComplete(pMsgCore, vrc);
+}
+
+/**
+ * @interface_method_impl{VBOXHGCMSVCHELPERS,pfnDisconnectClient}
+ */
+/* static */ DECLCALLBACK(int) HGCMService::svcHlpDisconnectClient(void *pvInstance, uint32_t idClient)
+{
+     HGCMService *pService = static_cast <HGCMService *> (pvInstance);
+     AssertReturn(pService, VERR_INVALID_HANDLE);
+
+     /* Only safe to call when the main HGCM thread is waiting on the service
+        to handle a SVC_MSG_CONNECT or SVC_MSG_DISCONNECT message.  Otherwise
+        we'd risk racing it and corrupt data structures. */
+     AssertReturn(pService->m_fInConnectOrDisconnect, VERR_INVALID_CONTEXT);
+
+     /* Resolve the client ID and verify that it belongs to this service before
+        trying to disconnect it. */
+     int vrc = VERR_NOT_FOUND;
+     HGCMClient * const pClient = HGCMClient::ReferenceByHandle(idClient);
+     if (pClient)
+     {
+         if (pClient->pService == pService)
+             vrc = pService->DisconnectClient(idClient, true, pClient);
+         hgcmObjDereference(pClient);
+     }
+     return vrc;
+}
+
+/**
+ * @interface_method_impl{VBOXHGCMSVCHELPERS,pfnIsCallRestored}
+ */
+/* static */ DECLCALLBACK(bool) HGCMService::svcHlpIsCallRestored(VBOXHGCMCALLHANDLE callHandle)
+{
+    HGCMMsgHeader *pMsgHdr = (HGCMMsgHeader *)callHandle;
+    AssertPtrReturn(pMsgHdr, false);
+
+    PVBOXHGCMCMD pCmd = pMsgHdr->pCmd;
+    AssertPtrReturn(pCmd, false);
+
+    PPDMIHGCMPORT pHgcmPort = pMsgHdr->pHGCMPort;
+    AssertPtrReturn(pHgcmPort, false);
+
+    return pHgcmPort->pfnIsCmdRestored(pHgcmPort, pCmd);
+}
+
+/**
+ * @interface_method_impl{VBOXHGCMSVCHELPERS,pfnIsCallCancelled}
+ */
+/* static */ DECLCALLBACK(bool) HGCMService::svcHlpIsCallCancelled(VBOXHGCMCALLHANDLE callHandle)
+{
+    HGCMMsgHeader *pMsgHdr = (HGCMMsgHeader *)callHandle;
+    AssertPtrReturn(pMsgHdr, false);
+
+    PVBOXHGCMCMD pCmd = pMsgHdr->pCmd;
+    AssertPtrReturn(pCmd, false);
+
+    PPDMIHGCMPORT pHgcmPort = pMsgHdr->pHGCMPort;
+    AssertPtrReturn(pHgcmPort, false);
+
+    return pHgcmPort->pfnIsCmdCancelled(pHgcmPort, pCmd);
+}
+
+/**
+ * @interface_method_impl{VBOXHGCMSVCHELPERS,pfnStamRegisterV}
+ */
+/* static */ DECLCALLBACK(int)
+HGCMService::svcHlpStamRegisterV(void *pvInstance, void *pvSample, STAMTYPE enmType, STAMVISIBILITY enmVisibility,
+                                 STAMUNIT enmUnit, const char *pszDesc, const char *pszName, va_list va)
+{
+     HGCMService *pService = static_cast <HGCMService *>(pvInstance);
+     AssertPtrReturn(pService, VERR_INVALID_PARAMETER);
+
+     if (pService->m_pUVM)
+         return pService->m_pVMM->pfnSTAMR3RegisterVU(pService->m_pUVM, pvSample, enmType, enmVisibility,
+                                                      enmUnit, pszDesc, pszName, va);
+     return VINF_SUCCESS;
+}
+
+/**
+ * @interface_method_impl{VBOXHGCMSVCHELPERS,pfnStamDeregisterV}
+ */
+/* static */ DECLCALLBACK(int) HGCMService::svcHlpStamDeregisterV(void *pvInstance, const char *pszPatFmt, va_list va)
+{
+     HGCMService *pService = static_cast <HGCMService *>(pvInstance);
+     AssertPtrReturn(pService, VERR_INVALID_PARAMETER);
+
+     if (pService->m_pUVM)
+         return pService->m_pVMM->pfnSTAMR3DeregisterV(pService->m_pUVM, pszPatFmt, va);
+     return VINF_SUCCESS;
+}
+
+/**
+ * @interface_method_impl{VBOXHGCMSVCHELPERS,pfnInfoRegister}
+ */
+/* static */ DECLCALLBACK(int) HGCMService::svcHlpInfoRegister(void *pvInstance, const char *pszName, const char *pszDesc,
+                                                               PFNDBGFHANDLEREXT pfnHandler, void *pvUser)
+{
+     HGCMService *pService = static_cast <HGCMService *>(pvInstance);
+     AssertPtrReturn(pService, VERR_INVALID_PARAMETER);
+
+     if (pService->m_pUVM)
+         return pService->m_pVMM->pfnDBGFR3InfoRegisterExternal(pService->m_pUVM, pszName, pszDesc, pfnHandler, pvUser);
+     return VINF_SUCCESS;
+}
+
+/**
+ * @interface_method_impl{VBOXHGCMSVCHELPERS,pfnInfoDeregister}
+ */
+/* static */ DECLCALLBACK(int) HGCMService::svcHlpInfoDeregister(void *pvInstance, const char *pszName)
+{
+     HGCMService *pService = static_cast <HGCMService *>(pvInstance);
+     AssertPtrReturn(pService, VERR_INVALID_PARAMETER);
+     if (pService->m_pUVM)
+         return pService->m_pVMM->pfnDBGFR3InfoDeregisterExternal(pService->m_pUVM, pszName);
+     return VINF_SUCCESS;
+}
+
+/**
+ * @interface_method_impl{VBOXHGCMSVCHELPERS,pfnGetRequestor}
+ */
+/* static */ DECLCALLBACK(uint32_t) HGCMService::svcHlpGetRequestor(VBOXHGCMCALLHANDLE hCall)
+{
+    HGCMMsgHeader *pMsgHdr = (HGCMMsgHeader *)(hCall);
+    AssertPtrReturn(pMsgHdr, VMMDEV_REQUESTOR_LOWEST);
+
+    PVBOXHGCMCMD pCmd = pMsgHdr->pCmd;
+    AssertPtrReturn(pCmd, VMMDEV_REQUESTOR_LOWEST);
+
+    PPDMIHGCMPORT pHgcmPort = pMsgHdr->pHGCMPort;
+    AssertPtrReturn(pHgcmPort, VMMDEV_REQUESTOR_LOWEST);
+
+    return pHgcmPort->pfnGetRequestor(pHgcmPort, pCmd);
+}
+
+/**
+ * @interface_method_impl{VBOXHGCMSVCHELPERS,pfnGetVMMDevSessionId}
+ */
+/* static */ DECLCALLBACK(uint64_t) HGCMService::svcHlpGetVMMDevSessionId(void *pvInstance)
+{
+     HGCMService *pService = static_cast <HGCMService *>(pvInstance);
+     AssertPtrReturn(pService, UINT64_MAX);
+
+     PPDMIHGCMPORT pHgcmPort = pService->m_pHgcmPort;
+     AssertPtrReturn(pHgcmPort, UINT64_MAX);
+
+     return pHgcmPort->pfnGetVMMDevSessionId(pHgcmPort);
+}
+
+
+static DECLCALLBACK(int) hgcmMsgCompletionCallback(int32_t result, HGCMMsgCore *pMsgCore)
+{
+    /* Call the VMMDev port interface to issue IRQ notification. */
+    HGCMMsgHeader *pMsgHdr = (HGCMMsgHeader *)pMsgCore;
+
+    LogFlow(("MAIN::hgcmMsgCompletionCallback: message %p\n", pMsgCore));
+
+    if (pMsgHdr->pHGCMPort)
+    {
+        if (!g_fResetting)
+            return pMsgHdr->pHGCMPort->pfnCompleted(pMsgHdr->pHGCMPort,
+                                                    g_fSaveState ? VINF_HGCM_SAVE_STATE : result, pMsgHdr->pCmd);
+        return VERR_ALREADY_RESET; /* best I could find. */
+    }
+    return VERR_NOT_AVAILABLE;
+}
+
+/*
+ * The main HGCM methods of the service.
+ */
+
+int HGCMService::instanceCreate(const char *pszServiceLibrary, const char *pszServiceName,
+                                PUVM pUVM, PCVMMR3VTABLE pVMM, PPDMIHGCMPORT pHgcmPort)
+{
+    LogFlowFunc(("name %s, lib %s\n", pszServiceName, pszServiceLibrary));
+
+    /* The maximum length of the thread name, allowed by the RT is 15. */
+    char szThreadName[16];
+    if (!strncmp(pszServiceName, RT_STR_TUPLE("VBoxShared")))
+        RTStrPrintf(szThreadName, sizeof(szThreadName), "Sh%s", pszServiceName + 10);
+    else if (!strncmp(pszServiceName, RT_STR_TUPLE("VBox")))
+        RTStrCopy(szThreadName, sizeof(szThreadName), pszServiceName + 4);
+    else
+        RTStrCopy(szThreadName, sizeof(szThreadName), pszServiceName);
+
+    int vrc = hgcmThreadCreate(&m_pThread, szThreadName, hgcmServiceThread, this, pszServiceName, pUVM, pVMM);
+    if (RT_SUCCESS(vrc))
+    {
+        m_pszSvcName    = RTStrDup(pszServiceName);
+        m_pszSvcLibrary = RTStrDup(pszServiceLibrary);
+
+        if (!m_pszSvcName || !m_pszSvcLibrary)
+        {
+            RTStrFree(m_pszSvcLibrary);
+            m_pszSvcLibrary = NULL;
+
+            RTStrFree(m_pszSvcName);
+            m_pszSvcName = NULL;
+
+            vrc = VERR_NO_MEMORY;
+        }
+        else
+        {
+            m_pUVM = pUVM;
+            m_pVMM = pVMM;
+            m_pHgcmPort = pHgcmPort;
+
+            registerStatistics(pszServiceName, pUVM, pVMM);
+
+            /* Initialize service helpers table. */
+            m_svcHelpers.pfnCallComplete       = svcHlpCallComplete;
+            m_svcHelpers.pvInstance            = this;
+            m_svcHelpers.pfnDisconnectClient   = svcHlpDisconnectClient;
+            m_svcHelpers.pfnIsCallRestored     = svcHlpIsCallRestored;
+            m_svcHelpers.pfnIsCallCancelled    = svcHlpIsCallCancelled;
+            m_svcHelpers.pfnStamRegisterV      = svcHlpStamRegisterV;
+            m_svcHelpers.pfnStamDeregisterV    = svcHlpStamDeregisterV;
+            m_svcHelpers.pfnInfoRegister       = svcHlpInfoRegister;
+            m_svcHelpers.pfnInfoDeregister     = svcHlpInfoDeregister;
+            m_svcHelpers.pfnGetRequestor       = svcHlpGetRequestor;
+            m_svcHelpers.pfnGetVMMDevSessionId = svcHlpGetVMMDevSessionId;
+
+            /* Execute the load request on the service thread. */
+            HGCMMsgCore *pCoreMsg;
+            vrc = hgcmMsgAlloc(m_pThread, &pCoreMsg, SVC_MSG_LOAD, hgcmMessageAllocSvc);
+
+            if (RT_SUCCESS(vrc))
+            {
+                HGCMMsgSvcLoad *pMsg = (HGCMMsgSvcLoad *)pCoreMsg;
+
+                pMsg->pUVM = pUVM;
+
+                vrc = hgcmMsgSend(pMsg);
+            }
+        }
+    }
+
+    if (RT_FAILURE(vrc))
+    {
+        instanceDestroy();
+    }
+
+    LogFlowFunc(("vrc = %Rrc\n", vrc));
+    return vrc;
+}
+
+/** Called by HGCMService::instanceCreate to register statistics. */
+void HGCMService::registerStatistics(const char *pszServiceName, PUVM pUVM, PCVMMR3VTABLE pVMM)
+{
+    pVMM->pfnSTAMR3RegisterFU(pUVM, &m_StatHandleMsg, STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_OCCURENCE,
+                              "Message handling", "/HGCM/%s/Msg", pszServiceName);
+    pVMM->pfnSTAMR3RegisterFU(pUVM, &m_StatTooManyCalls, STAMTYPE_COUNTER, STAMVISIBILITY_ALWAYS, STAMUNIT_OCCURENCES,
+                              "Too many calls (per client)", "/HGCM/%s/TooManyCalls", pszServiceName);
+    pVMM->pfnSTAMR3RegisterFU(pUVM, &m_StatTooManyClients, STAMTYPE_COUNTER, STAMVISIBILITY_ALWAYS, STAMUNIT_OCCURENCES,
+                              "Too many clients", "/HGCM/%s/TooManyClients", pszServiceName);
+    pVMM->pfnSTAMR3RegisterFU(pUVM, &m_cClients, STAMTYPE_U32, STAMVISIBILITY_ALWAYS, STAMUNIT_OCCURENCES,
+                              "Number of clients", "/HGCM/%s/Clients", pszServiceName);
+    pVMM->pfnSTAMR3RegisterFU(pUVM, &m_acClients[HGCM_CLIENT_CATEGORY_KERNEL], STAMTYPE_U32, STAMVISIBILITY_ALWAYS,
+                              STAMUNIT_OCCURENCES, "Number of kernel clients", "/HGCM/%s/Clients/Kernel", pszServiceName);
+    pVMM->pfnSTAMR3RegisterFU(pUVM, &m_acClients[HGCM_CLIENT_CATEGORY_ROOT], STAMTYPE_U32, STAMVISIBILITY_ALWAYS,
+                              STAMUNIT_OCCURENCES, "Number of root/admin clients", "/HGCM/%s/Clients/Root", pszServiceName);
+    pVMM->pfnSTAMR3RegisterFU(pUVM, &m_acClients[HGCM_CLIENT_CATEGORY_USER], STAMTYPE_U32, STAMVISIBILITY_ALWAYS,
+                              STAMUNIT_OCCURENCES, "Number of regular user clients", "/HGCM/%s/Clients/User", pszServiceName);
+    pVMM->pfnSTAMR3RegisterFU(pUVM, &m_fntable.acMaxClients[HGCM_CLIENT_CATEGORY_KERNEL], STAMTYPE_U32, STAMVISIBILITY_ALWAYS,
+                              STAMUNIT_OCCURENCES, "Max number of kernel clients", "/HGCM/%s/Clients/KernelMax", pszServiceName);
+    pVMM->pfnSTAMR3RegisterFU(pUVM, &m_fntable.acMaxClients[HGCM_CLIENT_CATEGORY_ROOT], STAMTYPE_U32, STAMVISIBILITY_ALWAYS,
+                              STAMUNIT_OCCURENCES, "Max number of root clients", "/HGCM/%s/Clients/RootMax", pszServiceName);
+    pVMM->pfnSTAMR3RegisterFU(pUVM, &m_fntable.acMaxClients[HGCM_CLIENT_CATEGORY_USER], STAMTYPE_U32, STAMVISIBILITY_ALWAYS,
+                              STAMUNIT_OCCURENCES, "Max number of user clients", "/HGCM/%s/Clients/UserMax", pszServiceName);
+    pVMM->pfnSTAMR3RegisterFU(pUVM, &m_fntable.idxLegacyClientCategory, STAMTYPE_U32, STAMVISIBILITY_ALWAYS,
+                              STAMUNIT_OCCURENCES, "Legacy client mapping", "/HGCM/%s/Clients/LegacyClientMapping", pszServiceName);
+    pVMM->pfnSTAMR3RegisterFU(pUVM, &m_fntable.acMaxCallsPerClient[HGCM_CLIENT_CATEGORY_KERNEL], STAMTYPE_U32, STAMVISIBILITY_ALWAYS,
+                              STAMUNIT_OCCURENCES, "Max number of call per kernel client", "/HGCM/%s/MaxCallsKernelClient", pszServiceName);
+    pVMM->pfnSTAMR3RegisterFU(pUVM, &m_fntable.acMaxCallsPerClient[HGCM_CLIENT_CATEGORY_ROOT], STAMTYPE_U32, STAMVISIBILITY_ALWAYS,
+                              STAMUNIT_OCCURENCES, "Max number of call per root client", "/HGCM/%s/MaxCallsRootClient", pszServiceName);
+    pVMM->pfnSTAMR3RegisterFU(pUVM, &m_fntable.acMaxCallsPerClient[HGCM_CLIENT_CATEGORY_USER], STAMTYPE_U32, STAMVISIBILITY_ALWAYS,
+                              STAMUNIT_OCCURENCES, "Max number of call per user client", "/HGCM/%s/MaxCallsUserClient", pszServiceName);
+}
+
+void HGCMService::instanceDestroy(void)
+{
+    LogFlowFunc(("%s\n", m_pszSvcName));
+
+    HGCMMsgCore *pMsg;
+    int vrc = hgcmMsgAlloc(m_pThread, &pMsg, SVC_MSG_UNLOAD, hgcmMessageAllocSvc);
+
+    if (RT_SUCCESS(vrc))
+    {
+        vrc = hgcmMsgSend(pMsg);
+
+        if (RT_SUCCESS(vrc))
+            hgcmThreadWait(m_pThread);
+    }
+
+    if (m_pszSvcName && m_pUVM)
+        m_pVMM->pfnSTAMR3DeregisterF(m_pUVM, "/HGCM/%s/*", m_pszSvcName);
+    m_pUVM = NULL;
+    m_pHgcmPort = NULL;
+
+    RTStrFree(m_pszSvcLibrary);
+    m_pszSvcLibrary = NULL;
+
+    RTStrFree(m_pszSvcName);
+    m_pszSvcName = NULL;
+
+    if (m_paClientIds)
+    {
+        RTMemFree(m_paClientIds);
+        m_paClientIds = NULL;
+    }
+}
+
+int HGCMService::saveClientState(uint32_t u32ClientId, PSSMHANDLE pSSM, PCVMMR3VTABLE pVMM)
+{
+    LogFlowFunc(("%s\n", m_pszSvcName));
+
+    HGCMMsgCore *pCoreMsg;
+    int vrc = hgcmMsgAlloc(m_pThread, &pCoreMsg, SVC_MSG_SAVESTATE, hgcmMessageAllocSvc);
+
+    if (RT_SUCCESS(vrc))
+    {
+        HGCMMsgLoadSaveStateClient *pMsg = (HGCMMsgLoadSaveStateClient *)pCoreMsg;
+
+        pMsg->u32ClientId = u32ClientId;
+        pMsg->pSSM        = pSSM;
+        pMsg->pVMM        = pVMM;
+
+        vrc = hgcmMsgSend(pMsg);
+    }
+
+    LogFlowFunc(("vrc = %Rrc\n", vrc));
+    return vrc;
+}
+
+int HGCMService::loadClientState(uint32_t u32ClientId, PSSMHANDLE pSSM, PCVMMR3VTABLE pVMM, uint32_t uVersion)
+{
+    LogFlowFunc(("%s\n", m_pszSvcName));
+
+    HGCMMsgCore *pCoreMsg;
+    int vrc = hgcmMsgAlloc(m_pThread, &pCoreMsg, SVC_MSG_LOADSTATE, hgcmMessageAllocSvc);
+
+    if (RT_SUCCESS(vrc))
+    {
+        HGCMMsgLoadSaveStateClient *pMsg = (HGCMMsgLoadSaveStateClient *)pCoreMsg;
+
+        pMsg->pSSM        = pSSM;
+        pMsg->pVMM        = pVMM;
+        pMsg->uVersion    = uVersion;
+        pMsg->u32ClientId = u32ClientId;
+
+        vrc = hgcmMsgSend(pMsg);
+    }
+
+    LogFlowFunc(("vrc = %Rrc\n", vrc));
+    return vrc;
+}
+
+
+/** The method creates a service and references it.
+ *
+ * @param   pszServiceLibrary  The library to be loaded.
+ * @param   pszServiceName     The name of the service.
+ * @param   pUVM               The user mode VM handle (for statistics and such).
+ * @param   pVMM               The VMM vtable (for statistics and such).
+ * @param   pHgcmPort          The VMMDev HGCM port interface.
+ *
+ * @return  VBox status code.
+ * @thread  main HGCM
+ */
+/* static */ int HGCMService::LoadService(const char *pszServiceLibrary, const char *pszServiceName,
+                                          PUVM pUVM, PCVMMR3VTABLE pVMM, PPDMIHGCMPORT pHgcmPort)
+{
+    LogFlowFunc(("lib %s, name = %s, pUVM = %p\n", pszServiceLibrary, pszServiceName, pUVM));
+
+    /* Look at already loaded services to avoid double loading. */
+
+    HGCMService *pSvc;
+    int vrc = HGCMService::ResolveService(&pSvc, pszServiceName);
+
+    if (RT_SUCCESS(vrc))
+    {
+        /* The service is already loaded. */
+        pSvc->ReleaseService();
+        vrc = VERR_HGCM_SERVICE_EXISTS;
+    }
+    else
+    {
+        /* Create the new service. */
+        pSvc = new (std::nothrow) HGCMService();
+
+        if (!pSvc)
+        {
+            vrc = VERR_NO_MEMORY;
+        }
+        else
+        {
+            /* Load the library and call the initialization entry point. */
+            vrc = pSvc->instanceCreate(pszServiceLibrary, pszServiceName, pUVM, pVMM, pHgcmPort);
+            if (RT_SUCCESS(vrc))
+            {
+                /* Insert the just created service to list for future references. */
+                pSvc->m_pSvcNext = sm_pSvcListHead;
+                pSvc->m_pSvcPrev = NULL;
+
+                if (sm_pSvcListHead)
+                    sm_pSvcListHead->m_pSvcPrev = pSvc;
+                else
+                    sm_pSvcListTail = pSvc;
+
+                sm_pSvcListHead = pSvc;
+
+                sm_cServices++;
+
+                /* Reference the service (for first time) until it is unloaded on HGCM termination. */
+                AssertRelease(pSvc->m_u32RefCnt == 0);
+                pSvc->ReferenceService();
+
+                LogFlowFunc(("service %p\n", pSvc));
+            }
+        }
+    }
+
+    LogFlowFunc(("vrc = %Rrc\n", vrc));
+    return vrc;
+}
+
+/** The method unloads a service.
+ *
+ * @thread main HGCM
+ */
+void HGCMService::UnloadService(bool fUvmIsInvalid)
+{
+    LogFlowFunc(("name = %s\n", m_pszSvcName));
+
+    if (fUvmIsInvalid)
+    {
+        m_pUVM = NULL;
+        m_pHgcmPort = NULL;
+    }
+
+    /* Remove the service from the list. */
+    if (m_pSvcNext)
+    {
+        m_pSvcNext->m_pSvcPrev = m_pSvcPrev;
+    }
+    else
+    {
+        sm_pSvcListTail = m_pSvcPrev;
+    }
+
+    if (m_pSvcPrev)
+    {
+        m_pSvcPrev->m_pSvcNext = m_pSvcNext;
+    }
+    else
+    {
+        sm_pSvcListHead = m_pSvcNext;
+    }
+
+    sm_cServices--;
+
+    /* The service must be unloaded only if all clients were disconnected. */
+    LogFlowFunc(("m_u32RefCnt = %d\n", m_u32RefCnt));
+    AssertRelease(m_u32RefCnt == 1);
+
+    /* Now the service can be released. */
+    ReleaseService();
+}
+
+/** The method unloads all services.
+ *
+ * @thread main HGCM
+ */
+/* static */ void HGCMService::UnloadAll(bool fUvmIsInvalid)
+{
+    while (sm_pSvcListHead)
+    {
+        sm_pSvcListHead->UnloadService(fUvmIsInvalid);
+    }
+}
+
+/** The method obtains a referenced pointer to the service with
+ *  specified name. The caller must call ReleaseService when
+ *  the pointer is no longer needed.
+ *
+ * @param ppSvc          Where to store the pointer to the service.
+ * @param pszServiceName The name of the service.
+ * @return VBox status code.
+ * @thread main HGCM
+ */
+/* static */ int HGCMService::ResolveService(HGCMService **ppSvc, const char *pszServiceName)
+{
+    LogFlowFunc(("ppSvc = %p name = %s\n",
+                 ppSvc, pszServiceName));
+
+    if (!ppSvc || !pszServiceName)
+    {
+        return VERR_INVALID_PARAMETER;
+    }
+
+    HGCMService *pSvc = sm_pSvcListHead;
+
+    while (pSvc)
+    {
+        if (strcmp(pSvc->m_pszSvcName, pszServiceName) == 0)
+        {
+            break;
+        }
+
+        pSvc = pSvc->m_pSvcNext;
+    }
+
+    LogFlowFunc(("lookup in the list is %p\n", pSvc));
+
+    if (pSvc == NULL)
+    {
+        *ppSvc = NULL;
+        return VERR_HGCM_SERVICE_NOT_FOUND;
+    }
+
+    pSvc->ReferenceService();
+
+    *ppSvc = pSvc;
+
+    return VINF_SUCCESS;
+}
+
+/** The method increases reference counter.
+ *
+ * @thread main HGCM
+ */
+void HGCMService::ReferenceService(void)
+{
+    ASMAtomicIncU32(&m_u32RefCnt);
+    LogFlowFunc(("[%s] m_u32RefCnt = %d\n", m_pszSvcName, m_u32RefCnt));
+}
+
+/** The method dereferences a service and deletes it when no more refs.
+ *
+ * @thread main HGCM
+ */
+void HGCMService::ReleaseService(void)
+{
+    LogFlowFunc(("m_u32RefCnt = %d\n", m_u32RefCnt));
+    uint32_t u32RefCnt = ASMAtomicDecU32(&m_u32RefCnt);
+    AssertRelease(u32RefCnt != ~0U);
+
+    LogFlowFunc(("u32RefCnt = %d, name %s\n", u32RefCnt, m_pszSvcName));
+
+    if (u32RefCnt == 0)
+    {
+        instanceDestroy();
+        delete this;
+    }
+}
+
+/** The method is called when the VM is being reset or terminated
+ *  and disconnects all clients from all services.
+ *
+ * @thread main HGCM
+ */
+/* static */ void HGCMService::Reset(void)
+{
+    g_fResetting = true;
+
+    HGCMService *pSvc = sm_pSvcListHead;
+
+    while (pSvc)
+    {
+        while (pSvc->m_cClients && pSvc->m_paClientIds)
+        {
+            uint32_t const     idClient = pSvc->m_paClientIds[0];
+            HGCMClient * const pClient  = HGCMClient::ReferenceByHandle(idClient);
+            Assert(pClient);
+            LogFlowFunc(("handle %d/%p\n", pSvc->m_paClientIds[0], pClient));
+
+            pSvc->DisconnectClient(pSvc->m_paClientIds[0], false, pClient);
+
+            hgcmObjDereference(pClient);
+        }
+
+        pSvc = pSvc->m_pSvcNext;
+    }
+
+    g_fResetting = false;
+}
+
+/** The method saves the HGCM state.
+ *
+ * @param pSSM  The saved state context.
+ * @param pVMM  The VMM vtable.
+ * @return VBox status code.
+ * @thread main HGCM
+ */
+/* static */ int HGCMService::SaveState(PSSMHANDLE pSSM, PCVMMR3VTABLE pVMM)
+{
+    /* Save the current handle count and restore afterwards to avoid client id conflicts. */
+    int vrc = pVMM->pfnSSMR3PutU32(pSSM, hgcmObjQueryHandleCount());
+    AssertRCReturn(vrc, vrc);
+
+    LogFlowFunc(("%d services to be saved:\n", sm_cServices));
+
+    /* Save number of services. */
+    vrc = pVMM->pfnSSMR3PutU32(pSSM, sm_cServices);
+    AssertRCReturn(vrc, vrc);
+
+    /* Save every service. */
+    HGCMService *pSvc = sm_pSvcListHead;
+
+    while (pSvc)
+    {
+        LogFlowFunc(("Saving service [%s]\n", pSvc->m_pszSvcName));
+
+        /* Save the length of the service name. */
+        vrc = pVMM->pfnSSMR3PutU32(pSSM, (uint32_t) strlen(pSvc->m_pszSvcName) + 1);
+        AssertRCReturn(vrc, vrc);
+
+        /* Save the name of the service. */
+        vrc = pVMM->pfnSSMR3PutStrZ(pSSM, pSvc->m_pszSvcName);
+        AssertRCReturn(vrc, vrc);
+
+        /* Save the number of clients. */
+        vrc = pVMM->pfnSSMR3PutU32(pSSM, pSvc->m_cClients);
+        AssertRCReturn(vrc, vrc);
+
+        /* Call the service for every client. Normally a service must not have
+         * a global state to be saved: only per client info is relevant.
+         * The global state of a service is configured during VM startup.
+         */
+        uint32_t i;
+
+        for (i = 0; i < pSvc->m_cClients; i++)
+        {
+            uint32_t u32ClientId = pSvc->m_paClientIds[i];
+
+            Log(("client id 0x%08X\n", u32ClientId));
+
+            /* Save the client id. (fRequestor is saved via SVC_MSG_SAVESTATE for convenience.) */
+            vrc = pVMM->pfnSSMR3PutU32(pSSM, u32ClientId);
+            AssertRCReturn(vrc, vrc);
+
+            /* Call the service, so the operation is executed by the service thread. */
+            vrc = pSvc->saveClientState(u32ClientId, pSSM, pVMM);
+            AssertRCReturn(vrc, vrc);
+        }
+
+        pSvc = pSvc->m_pSvcNext;
+    }
+
+    return VINF_SUCCESS;
+}
+
+/** The method loads saved HGCM state.
+ *
+ * @param pSSM      The saved state handle.
+ * @param pVMM      The VMM vtable.
+ * @param uVersion  The state version being loaded.
+ * @return VBox status code.
+ * @thread main HGCM
+ */
+/* static */ int HGCMService::LoadState(PSSMHANDLE pSSM, PCVMMR3VTABLE pVMM, uint32_t uVersion)
+{
+    /* Restore handle count to avoid client id conflicts. */
+    uint32_t u32;
+
+    int vrc = pVMM->pfnSSMR3GetU32(pSSM, &u32);
+    AssertRCReturn(vrc, vrc);
+
+    hgcmObjSetHandleCount(u32);
+
+    /* Get the number of services. */
+    uint32_t cServices;
+
+    vrc = pVMM->pfnSSMR3GetU32(pSSM, &cServices);
+    AssertRCReturn(vrc, vrc);
+
+    LogFlowFunc(("%d services to be restored:\n", cServices));
+
+    while (cServices--)
+    {
+        /* Get the length of the service name. */
+        vrc = pVMM->pfnSSMR3GetU32(pSSM, &u32);
+        AssertRCReturn(vrc, vrc);
+        AssertReturn(u32 <= VBOX_HGCM_SVC_NAME_MAX_BYTES, VERR_SSM_UNEXPECTED_DATA);
+
+        /* Get the service name. */
+        char szServiceName[VBOX_HGCM_SVC_NAME_MAX_BYTES];
+        vrc = pVMM->pfnSSMR3GetStrZ(pSSM, szServiceName, u32);
+        AssertRCReturn(vrc, vrc);
+
+        LogRel(("HGCM: Restoring [%s]\n", szServiceName));
+
+        /* Resolve the service instance. */
+        HGCMService *pSvc;
+        vrc = ResolveService(&pSvc, szServiceName);
+        AssertLogRelMsgReturn(pSvc, ("vrc=%Rrc, %s\n", vrc, szServiceName), VERR_SSM_UNEXPECTED_DATA);
+
+        /* Get the number of clients. */
+        uint32_t cClients;
+        vrc = pVMM->pfnSSMR3GetU32(pSSM, &cClients);
+        if (RT_FAILURE(vrc))
+        {
+            pSvc->ReleaseService();
+            AssertFailed();
+            return vrc;
+        }
+
+        while (cClients--)
+        {
+            /* Get the client ID and fRequest (convieniently save via SVC_MSG_SAVESTATE
+               but restored here in time for calling CreateAndConnectClient). */
+            uint32_t u32ClientId;
+            vrc = pVMM->pfnSSMR3GetU32(pSSM, &u32ClientId);
+            uint32_t fRequestor = VMMDEV_REQUESTOR_LEGACY;
+            if (RT_SUCCESS(vrc) && uVersion > HGCM_SAVED_STATE_VERSION_V2)
+                vrc = pVMM->pfnSSMR3GetU32(pSSM, &fRequestor);
+            AssertLogRelMsgRCReturnStmt(vrc, ("vrc=%Rrc, %s\n", vrc, szServiceName), pSvc->ReleaseService(), vrc);
+
+            /* Connect the client. */
+            vrc = pSvc->CreateAndConnectClient(NULL, u32ClientId, fRequestor, true /*fRestoring*/);
+            AssertLogRelMsgRCReturnStmt(vrc, ("vrc=%Rrc, %s\n", vrc, szServiceName), pSvc->ReleaseService(), vrc);
+
+            /* Call the service, so the operation is executed by the service thread. */
+            vrc = pSvc->loadClientState(u32ClientId, pSSM, pVMM, uVersion);
+            AssertLogRelMsgRCReturnStmt(vrc, ("vrc=%Rrc, %s\n", vrc, szServiceName), pSvc->ReleaseService(), vrc);
+        }
+
+        pSvc->ReleaseService();
+    }
+
+    return VINF_SUCCESS;
+}
+
+/* Create a new client instance and connect it to the service.
+ *
+ * @param pu32ClientIdOut If not NULL, then the method must generate a new handle for the client.
+ *                        If NULL, use the given 'u32ClientIdIn' handle.
+ * @param u32ClientIdIn   The handle for the client, when 'pu32ClientIdOut' is NULL.
+ * @param fRequestor      The requestor flags, VMMDEV_REQUESTOR_LEGACY if not available.
+ * @param fRestoring      Set if we're restoring a saved state.
+ * @return VBox status code.
+ */
+int HGCMService::CreateAndConnectClient(uint32_t *pu32ClientIdOut, uint32_t u32ClientIdIn, uint32_t fRequestor, bool fRestoring)
+{
+    LogFlowFunc(("pu32ClientIdOut = %p, u32ClientIdIn = %d, fRequestor = %#x, fRestoring = %d\n",
+                 pu32ClientIdOut, u32ClientIdIn, fRequestor, fRestoring));
+
+    /*
+     * Categorize the client (compress VMMDEV_REQUESTOR_USR_MASK)
+     * and check the respective client limit.
+     */
+    uint32_t idxClientCategory;
+    if (fRequestor == VMMDEV_REQUESTOR_LEGACY)
+    {
+        idxClientCategory = m_fntable.idxLegacyClientCategory;
+        AssertStmt(idxClientCategory < RT_ELEMENTS(m_acClients), idxClientCategory = HGCM_CLIENT_CATEGORY_KERNEL);
+    }
+    else
+        switch (fRequestor & VMMDEV_REQUESTOR_USR_MASK)
+        {
+            case VMMDEV_REQUESTOR_USR_DRV:
+            case VMMDEV_REQUESTOR_USR_DRV_OTHER:
+                idxClientCategory = HGCM_CLIENT_CATEGORY_KERNEL;
+                break;
+            case VMMDEV_REQUESTOR_USR_ROOT:
+            case VMMDEV_REQUESTOR_USR_SYSTEM:
+                idxClientCategory = HGCM_CLIENT_CATEGORY_ROOT;
+                break;
+            default:
+                idxClientCategory = HGCM_CLIENT_CATEGORY_USER;
+                break;
+        }
+
+    if (   m_acClients[idxClientCategory] < m_fntable.acMaxClients[idxClientCategory]
+        || fRestoring)
+    { }
+    else
+    {
+        LogRel2(("Too many concurrenct clients for HGCM service '%s': %u, max %u; category %u\n",
+                 m_pszSvcName, m_cClients, m_fntable.acMaxClients[idxClientCategory], idxClientCategory));
+        STAM_REL_COUNTER_INC(&m_StatTooManyClients);
+        return VERR_HGCM_TOO_MANY_CLIENTS;
+    }
+
+    /* Allocate a client information structure. */
+    HGCMClient *pClient = new (std::nothrow) HGCMClient(fRequestor, idxClientCategory);
+
+    if (!pClient)
+    {
+        Log1WarningFunc(("Could not allocate HGCMClient!!!\n"));
+        return VERR_NO_MEMORY;
+    }
+
+    uint32_t handle;
+
+    if (pu32ClientIdOut != NULL)
+    {
+        handle = hgcmObjGenerateHandle(pClient);
+    }
+    else
+    {
+        handle = hgcmObjAssignHandle(pClient, u32ClientIdIn);
+    }
+
+    LogFlowFunc(("client id = %d\n", handle));
+
+    AssertRelease(handle);
+
+    /* Initialize the HGCM part of the client. */
+    int vrc = pClient->Init(this);
+
+    if (RT_SUCCESS(vrc))
+    {
+        /* Call the service. */
+        HGCMMsgCore *pCoreMsg;
+
+        vrc = hgcmMsgAlloc(m_pThread, &pCoreMsg, SVC_MSG_CONNECT, hgcmMessageAllocSvc);
+
+        if (RT_SUCCESS(vrc))
+        {
+            HGCMMsgSvcConnect *pMsg = (HGCMMsgSvcConnect *)pCoreMsg;
+
+            pMsg->u32ClientId = handle;
+            pMsg->fRequestor = fRequestor;
+            pMsg->fRestoring = fRestoring;
+
+            vrc = hgcmMsgSend(pMsg);
+
+            if (RT_SUCCESS(vrc))
+            {
+                /* Add the client Id to the array. */
+                if (m_cClients == m_cClientsAllocated)
+                {
+                    const uint32_t cDelta = 64;
+
+                    /* Guards against integer overflow on 32bit arch and also limits size of m_paClientIds array to 4GB*/
+                    if (m_cClientsAllocated < UINT32_MAX / sizeof(m_paClientIds[0]) - cDelta)
+                    {
+                        uint32_t *paClientIdsNew;
+
+                        paClientIdsNew = (uint32_t *)RTMemRealloc(m_paClientIds,
+                                                                  (m_cClientsAllocated + cDelta) * sizeof(m_paClientIds[0]));
+                        Assert(paClientIdsNew);
+
+                        if (paClientIdsNew)
+                        {
+                            m_paClientIds = paClientIdsNew;
+                            m_cClientsAllocated += cDelta;
+                        }
+                        else
+                        {
+                            vrc = VERR_NO_MEMORY;
+                        }
+                    }
+                    else
+                    {
+                        vrc = VERR_NO_MEMORY;
+                    }
+                }
+
+                if (RT_SUCCESS(vrc))
+                {
+                    m_paClientIds[m_cClients] = handle;
+                    m_cClients++;
+                    m_acClients[idxClientCategory]++;
+                    LogFunc(("idClient=%u m_cClients=%u m_acClients[%u]=%u %s\n",
+                             handle, m_cClients, idxClientCategory, m_acClients[idxClientCategory], m_pszSvcName));
+                }
+            }
+        }
+    }
+
+    if (RT_SUCCESS(vrc))
+    {
+        if (pu32ClientIdOut != NULL)
+        {
+            *pu32ClientIdOut = handle;
+        }
+
+        ReferenceService();
+
+        /* The guest may now use this client object. */
+        pClient->makeAccessibleToGuest();
+    }
+    else
+    {
+        hgcmObjDeleteHandle(handle);
+    }
+
+    LogFlowFunc(("vrc = %Rrc\n", vrc));
+    return vrc;
+}
+
+/**
+ * Disconnect the client from the service and delete the client handle.
+ *
+ * @param   u32ClientId     The handle of the client.
+ * @param   fFromService    Set if called by the service via
+ *                          svcHlpDisconnectClient().
+ * @param   pClient         The client disconnecting.
+ * @return  VBox status code.
+ */
+int HGCMService::DisconnectClient(uint32_t u32ClientId, bool fFromService, HGCMClient *pClient)
+{
+    AssertPtr(pClient);
+    LogFlowFunc(("client id = %d, fFromService = %d, pClient = %p\n", u32ClientId, fFromService, pClient));
+
+    /*
+     * Destroy the client handle prior to the disconnecting to avoid creating
+     * a race with other messages from the same client.  See @bugref{10038}
+     * for further details.
+     */
+    Assert(pClient->idxCategory < HGCM_CLIENT_CATEGORY_MAX);
+    Assert(m_acClients[pClient->idxCategory] > 0);
+
+    bool fReleaseService = false;
+    int  vrc             = VERR_NOT_FOUND;
+    for (uint32_t i = 0; i < m_cClients; i++)
+    {
+        if (m_paClientIds[i] == u32ClientId)
+        {
+            if (m_acClients[pClient->idxCategory] > 0)
+                m_acClients[pClient->idxCategory]--;
+
+            m_cClients--;
+
+            if (m_cClients > i)
+                memmove(&m_paClientIds[i], &m_paClientIds[i + 1], sizeof(m_paClientIds[0]) * (m_cClients - i));
+
+            /* Delete the client handle. */
+            hgcmObjDeleteHandle(u32ClientId);
+            fReleaseService = true;
+
+            vrc = VINF_SUCCESS;
+            break;
+        }
+    }
+
+    /* Some paranoia wrt to not trusting the client ID array. */
+    Assert(vrc == VINF_SUCCESS || fFromService);
+    if (vrc == VERR_NOT_FOUND && !fFromService)
+    {
+        if (m_acClients[pClient->idxCategory] > 0)
+            m_acClients[pClient->idxCategory]--;
+
+        hgcmObjDeleteHandle(u32ClientId);
+        fReleaseService = true;
+    }
+
+    LogFunc(("idClient=%u m_cClients=%u m_acClients[%u]=%u %s (cPendingCalls=%u) vrc=%Rrc\n", u32ClientId, m_cClients,
+             pClient->idxCategory, m_acClients[pClient->idxCategory], m_pszSvcName, pClient->cPendingCalls, vrc));
+
+    /*
+     * Call the service.
+     */
+    if (!fFromService)
+    {
+        /* Call the service. */
+        HGCMMsgCore *pCoreMsg;
+
+        vrc = hgcmMsgAlloc(m_pThread, &pCoreMsg, SVC_MSG_DISCONNECT, hgcmMessageAllocSvc);
+
+        if (RT_SUCCESS(vrc))
+        {
+            HGCMMsgSvcDisconnect *pMsg = (HGCMMsgSvcDisconnect *)pCoreMsg;
+
+            pMsg->u32ClientId = u32ClientId;
+            pMsg->pClient = pClient;
+
+            vrc = hgcmMsgSend(pMsg);
+        }
+        else
+        {
+            LogRel(("(%d, %d) [%s] hgcmMsgAlloc(%p, SVC_MSG_DISCONNECT) failed %Rrc\n",
+                    u32ClientId, fFromService, RT_VALID_PTR(m_pszSvcName)? m_pszSvcName: "", m_pThread, vrc));
+        }
+    }
+
+
+    /*
+     * Release the pClient->pService reference.
+     */
+    if (fReleaseService)
+        ReleaseService();
+
+    LogFlowFunc(("vrc = %Rrc\n", vrc));
+    return vrc;
+}
+
+int HGCMService::RegisterExtension(HGCMSVCEXTHANDLE handle,
+                                   PFNHGCMSVCEXT pfnExtension,
+                                   void *pvExtension)
+{
+    LogFlowFunc(("%s\n", handle->pszServiceName));
+
+    /* Forward the message to the service thread. */
+    HGCMMsgCore *pCoreMsg;
+    int vrc = hgcmMsgAlloc(m_pThread, &pCoreMsg, SVC_MSG_REGEXT, hgcmMessageAllocSvc);
+
+    if (RT_SUCCESS(vrc))
+    {
+        HGCMMsgSvcRegisterExtension *pMsg = (HGCMMsgSvcRegisterExtension *)pCoreMsg;
+
+        pMsg->handle       = handle;
+        pMsg->pfnExtension = pfnExtension;
+        pMsg->pvExtension  = pvExtension;
+
+        vrc = hgcmMsgSend(pMsg);
+    }
+
+    LogFlowFunc(("vrc = %Rrc\n", vrc));
+    return vrc;
+}
+
+void HGCMService::UnregisterExtension(HGCMSVCEXTHANDLE handle)
+{
+    /* Forward the message to the service thread. */
+    HGCMMsgCore *pCoreMsg;
+    int vrc = hgcmMsgAlloc(m_pThread, &pCoreMsg, SVC_MSG_UNREGEXT, hgcmMessageAllocSvc);
+
+    if (RT_SUCCESS(vrc))
+    {
+        HGCMMsgSvcUnregisterExtension *pMsg = (HGCMMsgSvcUnregisterExtension *)pCoreMsg;
+
+        pMsg->handle = handle;
+
+        vrc = hgcmMsgSend(pMsg);
+    }
+
+    LogFlowFunc(("vrc = %Rrc\n", vrc));
+}
+
+/** @callback_method_impl{FNHGCMMSGCALLBACK}   */
+static DECLCALLBACK(int) hgcmMsgCallCompletionCallback(int32_t result, HGCMMsgCore *pMsgCore)
+{
+    /*
+     * Do common message completion then decrement the call counter
+     * for the client if necessary.
+     */
+    int vrc = hgcmMsgCompletionCallback(result, pMsgCore);
+
+    HGCMMsgCall *pMsg = (HGCMMsgCall *)pMsgCore;
+    if (pMsg->pcCounter)
+    {
+        uint32_t cCalls = ASMAtomicDecU32(pMsg->pcCounter);
+        AssertStmt(cCalls < UINT32_MAX / 2, ASMAtomicWriteU32(pMsg->pcCounter, 0));
+        pMsg->pcCounter = NULL;
+        Log3Func(("pMsg=%p cPendingCalls=%u / %u (fun %u, %u parms)\n",
+                  pMsg, cCalls, pMsg->u32ClientId, pMsg->u32Function, pMsg->cParms));
+    }
+
+    return vrc;
+}
+
+/** Perform a guest call to the service.
+ *
+ * @param pHGCMPort      The port to be used for completion confirmation.
+ * @param pCmd           The VBox HGCM context.
+ * @param u32ClientId    The client handle to be disconnected and deleted.
+ * @param pClient        The client data.
+ * @param u32Function    The function number.
+ * @param cParms         Number of parameters.
+ * @param paParms        Pointer to array of parameters.
+ * @param tsArrival      The STAM_GET_TS() value when the request arrived.
+ * @return VBox status code.
+ * @retval VINF_HGCM_ASYNC_EXECUTE on success.
+ */
+int HGCMService::GuestCall(PPDMIHGCMPORT pHGCMPort, PVBOXHGCMCMD pCmd, uint32_t u32ClientId, HGCMClient *pClient,
+                           uint32_t u32Function, uint32_t cParms, VBOXHGCMSVCPARM paParms[], uint64_t tsArrival)
+{
+    LogFlow(("MAIN::HGCMService::GuestCall\n"));
+
+    int vrc;
+    HGCMMsgCall *pMsg = new(std::nothrow) HGCMMsgCall(m_pThread);
+    if (pMsg)
+    {
+        pMsg->Reference(); /** @todo starts out with zero references. */
+
+        uint32_t cCalls = ASMAtomicIncU32(&pClient->cPendingCalls);
+        Assert(pClient->idxCategory < RT_ELEMENTS(m_fntable.acMaxCallsPerClient));
+        if (cCalls < m_fntable.acMaxCallsPerClient[pClient->idxCategory])
+        {
+            pMsg->pcCounter   = &pClient->cPendingCalls;
+            Log3(("MAIN::HGCMService::GuestCall: pMsg=%p cPendingCalls=%u / %u / %s (fun %u, %u parms)\n",
+                  pMsg, cCalls, u32ClientId, m_pszSvcName, u32Function, cParms));
+
+            pMsg->pCmd        = pCmd;
+            pMsg->pHGCMPort   = pHGCMPort;
+            pMsg->u32ClientId = u32ClientId;
+            pMsg->u32Function = u32Function;
+            pMsg->cParms      = cParms;
+            pMsg->paParms     = paParms;
+            pMsg->tsArrival   = tsArrival;
+
+            vrc = hgcmMsgPost(pMsg, hgcmMsgCallCompletionCallback);
+
+            if (RT_SUCCESS(vrc))
+            { /* Reference donated on success. */ }
+            else
+            {
+                ASMAtomicDecU32(&pClient->cPendingCalls);
+                pMsg->pcCounter = NULL;
+                Log(("MAIN::HGCMService::GuestCall: hgcmMsgPost failed: %Rrc\n", vrc));
+                pMsg->Dereference();
+            }
+        }
+        else
+        {
+            ASMAtomicDecU32(&pClient->cPendingCalls);
+            LogRel2(("HGCM: Too many calls to '%s' from client %u: %u, max %u; category %u\n", m_pszSvcName, u32ClientId,
+                     cCalls, m_fntable.acMaxCallsPerClient[pClient->idxCategory], pClient->idxCategory));
+            pMsg->Dereference();
+            STAM_REL_COUNTER_INC(&m_StatTooManyCalls);
+            vrc = VERR_HGCM_TOO_MANY_CLIENT_CALLS;
+        }
+    }
+    else
+    {
+        Log(("MAIN::HGCMService::GuestCall: Message allocation failed\n"));
+        vrc = VERR_NO_MEMORY;
+    }
+
+    LogFlowFunc(("vrc = %Rrc\n", vrc));
+    return vrc;
+}
+
+/** Guest cancelled a request (call, connection attempt, disconnect attempt).
+ *
+ * @param   pHGCMPort      The port to be used for completion confirmation
+ * @param   pCmd           The VBox HGCM context.
+ * @param   idClient       The client handle to be disconnected and deleted.
+ */
+void HGCMService::GuestCancelled(PPDMIHGCMPORT pHGCMPort, PVBOXHGCMCMD pCmd, uint32_t idClient)
+{
+    LogFlow(("MAIN::HGCMService::GuestCancelled\n"));
+
+    if (m_fntable.pfnCancelled)
+    {
+        HGCMMsgCancelled *pMsg = new (std::nothrow) HGCMMsgCancelled(m_pThread);
+        if (pMsg)
+        {
+            pMsg->Reference(); /** @todo starts out with zero references. */
+
+            pMsg->pCmd      = pCmd;
+            pMsg->pHGCMPort = pHGCMPort;
+            pMsg->idClient  = idClient;
+
+            hgcmMsgPost(pMsg, NULL);
+        }
+        else
+            Log(("MAIN::HGCMService::GuestCancelled: Message allocation failed\n"));
+    }
+}
+
+/** Perform a host call the service.
+ *
+ * @param u32Function    The function number.
+ * @param cParms         Number of parameters.
+ * @param paParms        Pointer to array of parameters.
+ * @return VBox status code.
+ */
+int HGCMService::HostCall(uint32_t u32Function, uint32_t cParms, VBOXHGCMSVCPARM *paParms)
+{
+    LogFlowFunc(("%s u32Function = %d, cParms = %d, paParms = %p\n",
+                 m_pszSvcName, u32Function, cParms, paParms));
+
+    HGCMMsgCore *pCoreMsg;
+    int vrc = hgcmMsgAlloc(m_pThread, &pCoreMsg, SVC_MSG_HOSTCALL, hgcmMessageAllocSvc);
+
+    if (RT_SUCCESS(vrc))
+    {
+        HGCMMsgHostCallSvc *pMsg = (HGCMMsgHostCallSvc *)pCoreMsg;
+
+        pMsg->u32Function      = u32Function;
+        pMsg->cParms           = cParms;
+        pMsg->paParms          = paParms;
+
+        vrc = hgcmMsgSend(pMsg);
+    }
+
+    LogFlowFunc(("vrc = %Rrc\n", vrc));
+    return vrc;
+}
+
+/** Posts a broadcast notification event to all interested services.
+ *
+ * @param   enmEvent    The notification event.
+ */
+/*static*/ void HGCMService::BroadcastNotify(HGCMNOTIFYEVENT enmEvent)
+{
+    for (HGCMService *pService = sm_pSvcListHead; pService != NULL; pService = pService->m_pSvcNext)
+    {
+        pService->Notify(enmEvent);
+    }
+}
+
+/** Posts a broadcast notification event to the service.
+ *
+ * @param   enmEvent    The notification event.
+ */
+void HGCMService::Notify(HGCMNOTIFYEVENT enmEvent)
+{
+    LogFlowFunc(("%s enmEvent=%d pfnNotify=%p\n", m_pszSvcName, enmEvent, m_fntable.pfnNotify));
+    if (m_fntable.pfnNotify)
+    {
+        HGCMMsgCore *pCoreMsg;
+        int vrc = hgcmMsgAlloc(m_pThread, &pCoreMsg, SVC_MSG_NOTIFY, hgcmMessageAllocSvc);
+        if (RT_SUCCESS(vrc))
+        {
+            HGCMMsgNotify *pMsg = (HGCMMsgNotify *)pCoreMsg;
+            pMsg->enmEvent = enmEvent;
+
+            vrc = hgcmMsgPost(pMsg, NULL);
+            AssertRC(vrc);
+        }
+    }
+}
+
+/*
+ * Main HGCM thread that manages services.
+ */
+
+/* Messages processed by the main HGCM thread. */
+#define HGCM_MSG_CONNECT    (10)  /**< Connect a client to a service. */
+#define HGCM_MSG_DISCONNECT (11)  /**< Disconnect the specified client id. */
+#define HGCM_MSG_LOAD       (12)  /**< Load the service. */
+#define HGCM_MSG_HOSTCALL   (13)  /**< Call the service. */
+#define HGCM_MSG_LOADSTATE  (14)  /**< Load saved state for the specified service. */
+#define HGCM_MSG_SAVESTATE  (15)  /**< Save state for the specified service. */
+#define HGCM_MSG_RESET      (16)  /**< Disconnect all clients from the specified service. */
+#define HGCM_MSG_QUIT       (17)  /**< Unload all services and terminate the thread. */
+#define HGCM_MSG_REGEXT     (18)  /**< Register a service extension. */
+#define HGCM_MSG_UNREGEXT   (19)  /**< Unregister a service extension. */
+#define HGCM_MSG_BRD_NOTIFY (20)  /**< Broadcast notification event (VM state change). */
+
+class HGCMMsgMainConnect: public HGCMMsgHeader
+{
+    public:
+        /* Service name. */
+        const char *pszServiceName;
+        /* Where to store the client handle. */
+        uint32_t *pu32ClientId;
+};
+
+class HGCMMsgMainDisconnect: public HGCMMsgHeader
+{
+    public:
+        /* Handle of the client to be disconnected. */
+        uint32_t u32ClientId;
+};
+
+class HGCMMsgMainLoad: public HGCMMsgCore
+{
+    public:
+        /* Name of the library to be loaded. */
+        const char *pszServiceLibrary;
+        /* Name to be assigned to the service. */
+        const char *pszServiceName;
+        /** The user mode VM handle (for statistics and such). */
+        PUVM pUVM;
+        /** The VMM vtable (for statistics and such). */
+        PCVMMR3VTABLE pVMM;
+        /** The HGCM port on the VMMDev device (for session ID and such). */
+        PPDMIHGCMPORT pHgcmPort;
+};
+
+class HGCMMsgMainHostCall: public HGCMMsgCore
+{
+    public:
+        /* Which service to call. */
+        const char *pszServiceName;
+        /* Function number. */
+        uint32_t u32Function;
+        /* Number of the function parameters. */
+        uint32_t cParms;
+        /* Pointer to array of the function parameters. */
+        VBOXHGCMSVCPARM *paParms;
+};
+
+class HGCMMsgMainLoadSaveState: public HGCMMsgCore
+{
+    public:
+        /** Saved state handle. */
+        PSSMHANDLE pSSM;
+        /** The VMM vtable. */
+        PCVMMR3VTABLE pVMM;
+        /** The HGCM saved state version being loaded (ignore for save). */
+        uint32_t uVersion;
+};
+
+class HGCMMsgMainReset: public HGCMMsgCore
+{
+    public:
+        /** Set if this is actually a shutdown and not a VM reset. */
+        bool fForShutdown;
+};
+
+class HGCMMsgMainQuit: public HGCMMsgCore
+{
+    public:
+        /** Whether UVM has gone invalid already or not. */
+        bool fUvmIsInvalid;
+};
+
+class HGCMMsgMainRegisterExtension: public HGCMMsgCore
+{
+    public:
+        /** Returned handle to be used in HGCMMsgMainUnregisterExtension. */
+        HGCMSVCEXTHANDLE *pHandle;
+        /** Name of the service. */
+        const char *pszServiceName;
+        /** The extension entry point. */
+        PFNHGCMSVCEXT pfnExtension;
+        /** The extension pointer. */
+        void *pvExtension;
+};
+
+class HGCMMsgMainUnregisterExtension: public HGCMMsgCore
+{
+    public:
+        /* Handle of the registered extension. */
+        HGCMSVCEXTHANDLE handle;
+};
+
+class HGCMMsgMainBroadcastNotify: public HGCMMsgCore
+{
+    public:
+        /** The notification event. */
+        HGCMNOTIFYEVENT enmEvent;
+};
+
+
+static HGCMMsgCore *hgcmMainMessageAlloc (uint32_t u32MsgId)
+{
+    switch (u32MsgId)
+    {
+        case HGCM_MSG_CONNECT:    return new HGCMMsgMainConnect();
+        case HGCM_MSG_DISCONNECT: return new HGCMMsgMainDisconnect();
+        case HGCM_MSG_LOAD:       return new HGCMMsgMainLoad();
+        case HGCM_MSG_HOSTCALL:   return new HGCMMsgMainHostCall();
+        case HGCM_MSG_LOADSTATE:
+        case HGCM_MSG_SAVESTATE:  return new HGCMMsgMainLoadSaveState();
+        case HGCM_MSG_RESET:      return new HGCMMsgMainReset();
+        case HGCM_MSG_QUIT:       return new HGCMMsgMainQuit();
+        case HGCM_MSG_REGEXT:     return new HGCMMsgMainRegisterExtension();
+        case HGCM_MSG_UNREGEXT:   return new HGCMMsgMainUnregisterExtension();
+        case HGCM_MSG_BRD_NOTIFY: return new HGCMMsgMainBroadcastNotify();
+
+        default:
+            AssertReleaseMsgFailed(("Msg id = %08X\n", u32MsgId));
+    }
+
+    return NULL;
+}
+
+
+/* The main HGCM thread handler. */
+static DECLCALLBACK(void) hgcmThread(HGCMThread *pThread, void *pvUser)
+{
+    LogFlowFunc(("pThread = %p, pvUser = %p\n", pThread, pvUser));
+
+    NOREF(pvUser);
+
+    bool fQuit = false;
+
+    while (!fQuit)
+    {
+        HGCMMsgCore *pMsgCore;
+        int vrc = hgcmMsgGet(pThread, &pMsgCore);
+
+        if (RT_FAILURE(vrc))
+        {
+            /* The error means some serious unrecoverable problem in the hgcmMsg/hgcmThread layer. */
+            AssertMsgFailed(("%Rrc\n", vrc));
+            break;
+        }
+
+        uint32_t u32MsgId = pMsgCore->MsgId();
+
+        switch (u32MsgId)
+        {
+            case HGCM_MSG_CONNECT:
+            {
+                HGCMMsgMainConnect *pMsg = (HGCMMsgMainConnect *)pMsgCore;
+
+                LogFlowFunc(("HGCM_MSG_CONNECT pszServiceName %s, pu32ClientId %p\n",
+                             pMsg->pszServiceName, pMsg->pu32ClientId));
+
+                /* Resolve the service name to the pointer to service instance.
+                 */
+                HGCMService *pService;
+                vrc = HGCMService::ResolveService(&pService, pMsg->pszServiceName);
+
+                if (RT_SUCCESS(vrc))
+                {
+                    /* Call the service instance method. */
+                    vrc = pService->CreateAndConnectClient(pMsg->pu32ClientId,
+                                                           0,
+                                                           pMsg->pHGCMPort->pfnGetRequestor(pMsg->pHGCMPort, pMsg->pCmd),
+                                                           pMsg->pHGCMPort->pfnIsCmdRestored(pMsg->pHGCMPort, pMsg->pCmd));
+
+                    /* Release the service after resolve. */
+                    pService->ReleaseService();
+                }
+            } break;
+
+            case HGCM_MSG_DISCONNECT:
+            {
+                HGCMMsgMainDisconnect *pMsg = (HGCMMsgMainDisconnect *)pMsgCore;
+
+                LogFlowFunc(("HGCM_MSG_DISCONNECT u32ClientId = %d\n",
+                             pMsg->u32ClientId));
+
+                HGCMClient *pClient = HGCMClient::ReferenceByHandle(pMsg->u32ClientId);
+
+                if (!pClient)
+                {
+                    vrc = VERR_HGCM_INVALID_CLIENT_ID;
+                    break;
+                }
+
+                /* The service the client belongs to. */
+                HGCMService *pService = pClient->pService;
+
+                /* Call the service instance to disconnect the client. */
+                vrc = pService->DisconnectClient(pMsg->u32ClientId, false, pClient);
+
+                hgcmObjDereference(pClient);
+            } break;
+
+            case HGCM_MSG_LOAD:
+            {
+                HGCMMsgMainLoad *pMsg = (HGCMMsgMainLoad *)pMsgCore;
+
+                LogFlowFunc(("HGCM_MSG_LOAD pszServiceName = %s, pMsg->pszServiceLibrary = %s, pMsg->pUVM = %p\n",
+                             pMsg->pszServiceName, pMsg->pszServiceLibrary, pMsg->pUVM));
+
+                vrc = HGCMService::LoadService(pMsg->pszServiceLibrary, pMsg->pszServiceName,
+                                               pMsg->pUVM, pMsg->pVMM, pMsg->pHgcmPort);
+            } break;
+
+            case HGCM_MSG_HOSTCALL:
+            {
+                HGCMMsgMainHostCall *pMsg = (HGCMMsgMainHostCall *)pMsgCore;
+
+                LogFlowFunc(("HGCM_MSG_HOSTCALL pszServiceName %s, u32Function %d, cParms %d, paParms %p\n",
+                             pMsg->pszServiceName, pMsg->u32Function, pMsg->cParms, pMsg->paParms));
+
+                /* Resolve the service name to the pointer to service instance. */
+                HGCMService *pService;
+                vrc = HGCMService::ResolveService(&pService, pMsg->pszServiceName);
+
+                if (RT_SUCCESS(vrc))
+                {
+                    vrc = pService->HostCall(pMsg->u32Function, pMsg->cParms, pMsg->paParms);
+
+                    pService->ReleaseService();
+                }
+            } break;
+
+            case HGCM_MSG_BRD_NOTIFY:
+            {
+                HGCMMsgMainBroadcastNotify *pMsg = (HGCMMsgMainBroadcastNotify *)pMsgCore;
+
+                LogFlowFunc(("HGCM_MSG_BRD_NOTIFY enmEvent=%d\n", pMsg->enmEvent));
+
+                HGCMService::BroadcastNotify(pMsg->enmEvent);
+            } break;
+
+            case HGCM_MSG_RESET:
+            {
+                LogFlowFunc(("HGCM_MSG_RESET\n"));
+
+                HGCMService::Reset();
+
+                HGCMMsgMainReset *pMsg = (HGCMMsgMainReset *)pMsgCore;
+                if (!pMsg->fForShutdown)
+                    HGCMService::BroadcastNotify(HGCMNOTIFYEVENT_RESET);
+            } break;
+
+            case HGCM_MSG_LOADSTATE:
+            {
+                HGCMMsgMainLoadSaveState *pMsg = (HGCMMsgMainLoadSaveState *)pMsgCore;
+
+                LogFlowFunc(("HGCM_MSG_LOADSTATE\n"));
+
+                vrc = HGCMService::LoadState(pMsg->pSSM, pMsg->pVMM, pMsg->uVersion);
+            } break;
+
+            case HGCM_MSG_SAVESTATE:
+            {
+                HGCMMsgMainLoadSaveState *pMsg = (HGCMMsgMainLoadSaveState *)pMsgCore;
+
+                LogFlowFunc(("HGCM_MSG_SAVESTATE\n"));
+
+                vrc = HGCMService::SaveState(pMsg->pSSM, pMsg->pVMM);
+            } break;
+
+            case HGCM_MSG_QUIT:
+            {
+                HGCMMsgMainQuit *pMsg = (HGCMMsgMainQuit *)pMsgCore;
+                LogFlowFunc(("HGCM_MSG_QUIT\n"));
+
+                HGCMService::UnloadAll(pMsg->fUvmIsInvalid);
+
+                fQuit = true;
+            } break;
+
+            case HGCM_MSG_REGEXT:
+            {
+                HGCMMsgMainRegisterExtension *pMsg = (HGCMMsgMainRegisterExtension *)pMsgCore;
+
+                LogFlowFunc(("HGCM_MSG_REGEXT\n"));
+
+                /* Allocate the handle data. */
+                HGCMSVCEXTHANDLE handle = (HGCMSVCEXTHANDLE)RTMemAllocZ(sizeof(struct _HGCMSVCEXTHANDLEDATA)
+                                                                        + strlen(pMsg->pszServiceName)
+                                                                        + sizeof(char));
+
+                if (handle == NULL)
+                {
+                    vrc = VERR_NO_MEMORY;
+                }
+                else
+                {
+                    handle->pszServiceName = (char *)((uint8_t *)handle + sizeof(struct _HGCMSVCEXTHANDLEDATA));
+                    strcpy(handle->pszServiceName, pMsg->pszServiceName);
+
+                    HGCMService *pService;
+                    vrc = HGCMService::ResolveService(&pService, handle->pszServiceName);
+
+                    if (RT_SUCCESS(vrc))
+                    {
+                        pService->RegisterExtension(handle, pMsg->pfnExtension, pMsg->pvExtension);
+
+                        pService->ReleaseService();
+                    }
+
+                    if (RT_FAILURE(vrc))
+                    {
+                        RTMemFree(handle);
+                    }
+                    else
+                    {
+                        *pMsg->pHandle = handle;
+                    }
+                }
+            } break;
+
+            case HGCM_MSG_UNREGEXT:
+            {
+                HGCMMsgMainUnregisterExtension *pMsg = (HGCMMsgMainUnregisterExtension *)pMsgCore;
+
+                LogFlowFunc(("HGCM_MSG_UNREGEXT\n"));
+
+                HGCMService *pService;
+                vrc = HGCMService::ResolveService(&pService, pMsg->handle->pszServiceName);
+
+                if (RT_SUCCESS(vrc))
+                {
+                    pService->UnregisterExtension(pMsg->handle);
+
+                    pService->ReleaseService();
+                }
+
+                RTMemFree(pMsg->handle);
+            } break;
+
+            default:
+            {
+                AssertMsgFailed(("hgcmThread: Unsupported message number %08X!!!\n", u32MsgId));
+                vrc = VERR_NOT_SUPPORTED;
+            } break;
+        }
+
+        /* Complete the message processing. */
+        hgcmMsgComplete(pMsgCore, vrc);
+
+        LogFlowFunc(("message processed %Rrc\n", vrc));
+    }
+}
+
+
+/*
+ * The HGCM API.
+ */
+
+/** The main hgcm thread. */
+static HGCMThread *g_pHgcmThread = 0;
+
+/*
+ * Public HGCM functions.
+ *
+ * hgcmGuest* - called as a result of the guest HGCM requests.
+ * hgcmHost*  - called by the host.
+ */
+
+/* Load a HGCM service from the specified library.
+ * Assign the specified name to the service.
+ *
+ * @param pszServiceLibrary  The library to be loaded.
+ * @param pszServiceName     The name to be assigned to the service.
+ * @param pUVM               The user mode VM handle (for statistics and such).
+ * @param pVMM               The VMM vtable (for statistics and such).
+ * @param pHgcmPort          The HGCM port on the VMMDev device (for session ID and such).
+ * @return VBox status code.
+ */
+int HGCMHostLoad(const char *pszServiceLibrary,
+                 const char *pszServiceName,
+                 PUVM pUVM,
+                 PCVMMR3VTABLE pVMM,
+                 PPDMIHGCMPORT pHgcmPort)
+{
+    LogFlowFunc(("lib = %s, name = %s\n", pszServiceLibrary, pszServiceName));
+
+    if (!pszServiceLibrary || !pszServiceName)
+        return VERR_INVALID_PARAMETER;
+
+    /* Forward the request to the main hgcm thread. */
+    HGCMMsgCore *pCoreMsg;
+    int vrc = hgcmMsgAlloc(g_pHgcmThread, &pCoreMsg, HGCM_MSG_LOAD, hgcmMainMessageAlloc);
+    if (RT_SUCCESS(vrc))
+    {
+        /* Initialize the message. Since the message is synchronous, use the supplied pointers. */
+        HGCMMsgMainLoad *pMsg = (HGCMMsgMainLoad *)pCoreMsg;
+
+        pMsg->pszServiceLibrary = pszServiceLibrary;
+        pMsg->pszServiceName    = pszServiceName;
+        pMsg->pUVM              = pUVM;
+        pMsg->pVMM              = pVMM;
+        pMsg->pHgcmPort         = pHgcmPort;
+
+        vrc = hgcmMsgSend(pMsg);
+    }
+
+    LogFlowFunc(("vrc = %Rrc\n", vrc));
+    return vrc;
+}
+
+/* Register a HGCM service extension.
+ *
+ * @param pHandle            Returned handle for the registered extension.
+ * @param pszServiceName     The name of the service.
+ * @param pfnExtension       The extension entry point (callback).
+ * @param pvExtension        The extension pointer.
+ * @return VBox status code.
+ */
+int HGCMHostRegisterServiceExtension(HGCMSVCEXTHANDLE *pHandle,
+                                     const char *pszServiceName,
+                                     PFNHGCMSVCEXT pfnExtension,
+                                     void *pvExtension)
+{
+    LogFlowFunc(("pHandle = %p, name = %s, pfn = %p, rv = %p\n", pHandle, pszServiceName, pfnExtension, pvExtension));
+
+    if (!pHandle || !pszServiceName || !pfnExtension)
+    {
+        return VERR_INVALID_PARAMETER;
+    }
+
+    /* Forward the request to the main hgcm thread. */
+    HGCMMsgCore *pCoreMsg;
+    int vrc = hgcmMsgAlloc(g_pHgcmThread, &pCoreMsg, HGCM_MSG_REGEXT, hgcmMainMessageAlloc);
+
+    if (RT_SUCCESS(vrc))
+    {
+        /* Initialize the message. Since the message is synchronous, use the supplied pointers. */
+        HGCMMsgMainRegisterExtension *pMsg = (HGCMMsgMainRegisterExtension *)pCoreMsg;
+
+        pMsg->pHandle        = pHandle;
+        pMsg->pszServiceName = pszServiceName;
+        pMsg->pfnExtension   = pfnExtension;
+        pMsg->pvExtension    = pvExtension;
+
+        vrc = hgcmMsgSend(pMsg);
+    }
+
+    LogFlowFunc(("*pHandle = %p, vrc = %Rrc\n", *pHandle, vrc));
+    return vrc;
+}
+
+void HGCMHostUnregisterServiceExtension(HGCMSVCEXTHANDLE handle)
+{
+    LogFlowFunc(("handle = %p\n", handle));
+
+    /* Forward the request to the main hgcm thread. */
+    HGCMMsgCore *pCoreMsg;
+    int vrc = hgcmMsgAlloc(g_pHgcmThread, &pCoreMsg, HGCM_MSG_UNREGEXT, hgcmMainMessageAlloc);
+
+    if (RT_SUCCESS(vrc))
+    {
+        /* Initialize the message. */
+        HGCMMsgMainUnregisterExtension *pMsg = (HGCMMsgMainUnregisterExtension *)pCoreMsg;
+
+        pMsg->handle = handle;
+
+        vrc = hgcmMsgSend(pMsg);
+    }
+
+    LogFlowFunc(("vrc = %Rrc\n", vrc));
+    return;
+}
+
+/* Find a service and inform it about a client connection, create a client handle.
+ *
+ * @param pHGCMPort      The port to be used for completion confirmation.
+ * @param pCmd           The VBox HGCM context.
+ * @param pszServiceName The name of the service to be connected to.
+ * @param pu32ClientId   Where the store the created client handle.
+ * @return VBox status code.
+ */
+int HGCMGuestConnect(PPDMIHGCMPORT pHGCMPort,
+                     PVBOXHGCMCMD pCmd,
+                     const char *pszServiceName,
+                     uint32_t *pu32ClientId)
+{
+    LogFlowFunc(("pHGCMPort = %p, pCmd = %p, name = %s, pu32ClientId = %p\n",
+                 pHGCMPort, pCmd, pszServiceName, pu32ClientId));
+
+    if (pHGCMPort == NULL || pCmd == NULL || pszServiceName == NULL || pu32ClientId == NULL)
+    {
+        return VERR_INVALID_PARAMETER;
+    }
+
+    /* Forward the request to the main hgcm thread. */
+    HGCMMsgCore *pCoreMsg;
+    int vrc = hgcmMsgAlloc(g_pHgcmThread, &pCoreMsg, HGCM_MSG_CONNECT, hgcmMainMessageAlloc);
+
+    if (RT_SUCCESS(vrc))
+    {
+        /* Initialize the message. Since 'pszServiceName' and 'pu32ClientId'
+         * will not be deallocated by the caller until the message is completed,
+         * use the supplied pointers.
+         */
+        HGCMMsgMainConnect *pMsg = (HGCMMsgMainConnect *)pCoreMsg;
+
+        pMsg->pHGCMPort      = pHGCMPort;
+        pMsg->pCmd           = pCmd;
+        pMsg->pszServiceName = pszServiceName;
+        pMsg->pu32ClientId   = pu32ClientId;
+
+        vrc = hgcmMsgPost(pMsg, hgcmMsgCompletionCallback);
+    }
+
+    LogFlowFunc(("vrc = %Rrc\n", vrc));
+    return vrc;
+}
+
+/* Tell a service that the client is disconnecting, destroy the client handle.
+ *
+ * @param pHGCMPort      The port to be used for completion confirmation.
+ * @param pCmd           The VBox HGCM context.
+ * @param u32ClientId    The client handle to be disconnected and deleted.
+ * @return VBox status code.
+ */
+int HGCMGuestDisconnect(PPDMIHGCMPORT pHGCMPort,
+                        PVBOXHGCMCMD pCmd,
+                        uint32_t u32ClientId)
+{
+    LogFlowFunc(("pHGCMPort = %p, pCmd = %p, u32ClientId = %d\n",
+                  pHGCMPort, pCmd, u32ClientId));
+
+    if (!pHGCMPort || !pCmd || !u32ClientId)
+    {
+        return VERR_INVALID_PARAMETER;
+    }
+
+    /* Forward the request to the main hgcm thread. */
+    HGCMMsgCore *pCoreMsg;
+    int vrc = hgcmMsgAlloc(g_pHgcmThread, &pCoreMsg, HGCM_MSG_DISCONNECT, hgcmMainMessageAlloc);
+
+    if (RT_SUCCESS(vrc))
+    {
+        /* Initialize the message. */
+        HGCMMsgMainDisconnect *pMsg = (HGCMMsgMainDisconnect *)pCoreMsg;
+
+        pMsg->pCmd        = pCmd;
+        pMsg->pHGCMPort   = pHGCMPort;
+        pMsg->u32ClientId = u32ClientId;
+
+        vrc = hgcmMsgPost(pMsg, hgcmMsgCompletionCallback);
+    }
+
+    LogFlowFunc(("vrc = %Rrc\n", vrc));
+    return vrc;
+}
+
+/** Helper to send either HGCM_MSG_SAVESTATE or HGCM_MSG_LOADSTATE messages to the main HGCM thread.
+ *
+ * @param pSSM     The SSM handle.
+ * @param pVMM      The VMM vtable.
+ * @param idMsg    The message to be sent: HGCM_MSG_SAVESTATE or HGCM_MSG_LOADSTATE.
+ * @param uVersion The state version being loaded.
+ * @return VBox status code.
+ */
+static int hgcmHostLoadSaveState(PSSMHANDLE pSSM, PCVMMR3VTABLE pVMM, uint32_t idMsg, uint32_t uVersion)
+{
+    LogFlowFunc(("pSSM = %p, pVMM = %p, idMsg = %d, uVersion = %#x\n", pSSM, pVMM, idMsg, uVersion));
+
+    HGCMMsgCore *pCoreMsg;
+    int vrc = hgcmMsgAlloc(g_pHgcmThread, &pCoreMsg, idMsg, hgcmMainMessageAlloc);
+    if (RT_SUCCESS(vrc))
+    {
+        HGCMMsgMainLoadSaveState *pMsg = (HGCMMsgMainLoadSaveState *)pCoreMsg;
+        AssertRelease(pMsg);
+
+        pMsg->pSSM = pSSM;
+        pMsg->pVMM = pVMM;
+        pMsg->uVersion = uVersion;
+
+        vrc = hgcmMsgSend(pMsg);
+    }
+
+    LogFlowFunc(("vrc = %Rrc\n", vrc));
+    return vrc;
+}
+
+/** Save the state of services.
+ *
+ * @param pSSM      The SSM handle.
+ * @param pVMM      The VMM vtable.
+ * @return VBox status code.
+ */
+int HGCMHostSaveState(PSSMHANDLE pSSM, PCVMMR3VTABLE pVMM)
+{
+    return hgcmHostLoadSaveState(pSSM, pVMM, HGCM_MSG_SAVESTATE, HGCM_SAVED_STATE_VERSION);
+}
+
+/** Load the state of services.
+ *
+ * @param pSSM      The SSM handle.
+ * @param pVMM      The VMM vtable.
+ * @param uVersion  The state version being loaded.
+ * @return VBox status code.
+ */
+int HGCMHostLoadState(PSSMHANDLE pSSM, PCVMMR3VTABLE pVMM, uint32_t uVersion)
+{
+    return hgcmHostLoadSaveState(pSSM, pVMM, HGCM_MSG_LOADSTATE, uVersion);
+}
+
+/** The guest calls the service.
+ *
+ * @param pHGCMPort      The port to be used for completion confirmation.
+ * @param pCmd           The VBox HGCM context.
+ * @param u32ClientId    The client handle.
+ * @param u32Function    The function number.
+ * @param cParms         Number of parameters.
+ * @param paParms        Pointer to array of parameters.
+ * @param tsArrival      The STAM_GET_TS() value when the request arrived.
+ * @return VBox status code.
+ */
+int HGCMGuestCall(PPDMIHGCMPORT pHGCMPort,
+                  PVBOXHGCMCMD pCmd,
+                  uint32_t u32ClientId,
+                  uint32_t u32Function,
+                  uint32_t cParms,
+                  VBOXHGCMSVCPARM *paParms,
+                  uint64_t tsArrival)
+{
+    LogFlowFunc(("pHGCMPort = %p, pCmd = %p, u32ClientId = %d, u32Function = %d, cParms = %d, paParms = %p\n",
+                  pHGCMPort, pCmd, u32ClientId, u32Function, cParms, paParms));
+
+    if (!pHGCMPort || !pCmd || u32ClientId == 0)
+    {
+        return VERR_INVALID_PARAMETER;
+    }
+
+    int vrc = VERR_HGCM_INVALID_CLIENT_ID;
+
+    /* Resolve the client handle to the client instance pointer. */
+    HGCMClient *pClient = HGCMClient::ReferenceByHandleForGuest(u32ClientId);
+
+    if (pClient)
+    {
+        AssertRelease(pClient->pService);
+
+        /* Forward the message to the service thread. */
+        vrc = pClient->pService->GuestCall(pHGCMPort, pCmd, u32ClientId, pClient, u32Function, cParms, paParms, tsArrival);
+
+        hgcmObjDereference(pClient);
+    }
+
+    LogFlowFunc(("vrc = %Rrc\n", vrc));
+    return vrc;
+}
+
+/** The guest cancelled a request (call, connect, disconnect)
+ *
+ * @param   pHGCMPort      The port to be used for completion confirmation.
+ * @param   pCmd           The VBox HGCM context.
+ * @param   idClient       The client handle.
+ */
+void HGCMGuestCancelled(PPDMIHGCMPORT pHGCMPort, PVBOXHGCMCMD pCmd, uint32_t idClient)
+{
+    LogFlowFunc(("pHGCMPort = %p, pCmd = %p, idClient = %d\n", pHGCMPort, pCmd, idClient));
+    AssertReturnVoid(pHGCMPort);
+    AssertReturnVoid(pCmd);
+    AssertReturnVoid(idClient != 0);
+
+    /* Resolve the client handle to the client instance pointer. */
+    HGCMClient *pClient = HGCMClient::ReferenceByHandleForGuest(idClient);
+
+    if (pClient)
+    {
+        AssertRelease(pClient->pService);
+
+        /* Forward the message to the service thread. */
+        pClient->pService->GuestCancelled(pHGCMPort, pCmd, idClient);
+
+        hgcmObjDereference(pClient);
+    }
+
+    LogFlowFunc(("returns\n"));
+}
+
+/** The host calls the service.
+ *
+ * @param pszServiceName The service name to be called.
+ * @param u32Function    The function number.
+ * @param cParms         Number of parameters.
+ * @param paParms        Pointer to array of parameters.
+ * @return VBox status code.
+ */
+int HGCMHostCall(const char *pszServiceName,
+                 uint32_t u32Function,
+                 uint32_t cParms,
+                 VBOXHGCMSVCPARM *paParms)
+{
+    LogFlowFunc(("name = %s, u32Function = %d, cParms = %d, paParms = %p\n",
+                 pszServiceName, u32Function, cParms, paParms));
+
+    if (!pszServiceName)
+    {
+        return VERR_INVALID_PARAMETER;
+    }
+
+    /* Host calls go to main HGCM thread that resolves the service name to the
+     * service instance pointer and then, using the service pointer, forwards
+     * the message to the service thread.
+     * So it is slow but host calls are intended mostly for configuration and
+     * other non-time-critical functions.
+     */
+    HGCMMsgCore *pCoreMsg;
+    int vrc = hgcmMsgAlloc(g_pHgcmThread, &pCoreMsg, HGCM_MSG_HOSTCALL, hgcmMainMessageAlloc);
+
+    if (RT_SUCCESS(vrc))
+    {
+        HGCMMsgMainHostCall *pMsg = (HGCMMsgMainHostCall *)pCoreMsg;
+
+        pMsg->pszServiceName = (char *)pszServiceName;
+        pMsg->u32Function    = u32Function;
+        pMsg->cParms         = cParms;
+        pMsg->paParms        = paParms;
+
+        vrc = hgcmMsgSend(pMsg);
+    }
+
+    LogFlowFunc(("vrc = %Rrc\n", vrc));
+    return vrc;
+}
+
+/** Posts a notification event to all services.
+ *
+ * @param   enmEvent    The notification event.
+ * @return  VBox status code.
+ */
+int HGCMBroadcastEvent(HGCMNOTIFYEVENT enmEvent)
+{
+    LogFlowFunc(("enmEvent=%d\n", enmEvent));
+
+    HGCMMsgCore *pCoreMsg;
+    int vrc = hgcmMsgAlloc(g_pHgcmThread, &pCoreMsg, HGCM_MSG_BRD_NOTIFY, hgcmMainMessageAlloc);
+
+    if (RT_SUCCESS(vrc))
+    {
+        HGCMMsgMainBroadcastNotify *pMsg = (HGCMMsgMainBroadcastNotify *)pCoreMsg;
+
+        pMsg->enmEvent = enmEvent;
+
+        vrc = hgcmMsgPost(pMsg, NULL);
+    }
+
+    LogFlowFunc(("vrc = %Rrc\n", vrc));
+    return vrc;
+}
+
+
+int HGCMHostReset(bool fForShutdown)
+{
+    LogFlowFunc(("\n"));
+
+    /* Disconnect all clients.
+     */
+
+    HGCMMsgCore *pMsgCore;
+    int vrc = hgcmMsgAlloc(g_pHgcmThread, &pMsgCore, HGCM_MSG_RESET, hgcmMainMessageAlloc);
+
+    if (RT_SUCCESS(vrc))
+    {
+        HGCMMsgMainReset *pMsg = (HGCMMsgMainReset *)pMsgCore;
+
+        pMsg->fForShutdown = fForShutdown;
+
+        vrc = hgcmMsgSend(pMsg);
+    }
+
+    LogFlowFunc(("vrc = %Rrc\n", vrc));
+    return vrc;
+}
+
+int HGCMHostInit(void)
+{
+    LogFlowFunc(("\n"));
+
+    int vrc = hgcmThreadInit();
+
+    if (RT_SUCCESS(vrc))
+    {
+        /*
+         * Start main HGCM thread.
+         */
+
+        vrc = hgcmThreadCreate(&g_pHgcmThread, "MainHGCMthread", hgcmThread, NULL /*pvUser*/,
+                               NULL /*pszStatsSubDir*/, NULL /*pUVM*/, NULL /*pVMM*/);
+
+        if (RT_FAILURE(vrc))
+            LogRel(("Failed to start HGCM thread. HGCM services will be unavailable!!! vrc = %Rrc\n", vrc));
+    }
+
+    LogFlowFunc(("vrc = %Rrc\n", vrc));
+    return vrc;
+}
+
+int HGCMHostShutdown(bool fUvmIsInvalid /*= false*/)
+{
+    LogFlowFunc(("\n"));
+
+    /*
+     * Do HGCMReset and then unload all services.
+     */
+
+    int vrc = HGCMHostReset(true /*fForShutdown*/);
+
+    if (RT_SUCCESS(vrc))
+    {
+        /* Send the quit message to the main hgcmThread. */
+        HGCMMsgCore *pMsgCore;
+        vrc = hgcmMsgAlloc(g_pHgcmThread, &pMsgCore, HGCM_MSG_QUIT, hgcmMainMessageAlloc);
+
+        if (RT_SUCCESS(vrc))
+        {
+            HGCMMsgMainQuit *pMsg = (HGCMMsgMainQuit *)pMsgCore;
+            pMsg->fUvmIsInvalid = fUvmIsInvalid;
+
+            vrc = hgcmMsgSend(pMsg);
+
+            if (RT_SUCCESS(vrc))
+            {
+                /* Wait for the thread termination. */
+                hgcmThreadWait(g_pHgcmThread);
+                g_pHgcmThread = NULL;
+
+                hgcmThreadUninit();
+            }
+        }
+    }
+
+    LogFlowFunc(("vrc = %Rrc\n", vrc));
+    return vrc;
+}
+