Adding upstream version 6.1.22-dfsg.upstream/6.1.22-dfsgupstream

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

3 files changed, 1154 insertions, 0 deletions

diff --git a/src/VBox/Runtime/common/ioqueue/ioqueue-aiofile-provider.cpp b/src/VBox/Runtime/common/ioqueue/ioqueue-aiofile-provider.cpp
new file mode 100644
index 00000000..c4efa38d
--- /dev/null
+++ b/src/VBox/Runtime/common/ioqueue/ioqueue-aiofile-provider.cpp
@@ -0,0 +1,328 @@
+/* $Id: ioqueue-aiofile-provider.cpp $ */
+/** @file
+ * IPRT - I/O queue, Async I/O file provider.
+ */
+
+/*
+ * Copyright (C) 2019-2020 Oracle Corporation
+ *
+ * This file is part of VirtualBox Open Source Edition (OSE), as
+ * available from http://www.virtualbox.org. This file is free software;
+ * you can redistribute it and/or modify it under the terms of the GNU
+ * General Public License (GPL) as published by the Free Software
+ * Foundation, in version 2 as it comes in the "COPYING" file of the
+ * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
+ * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
+ *
+ * The contents of this file may alternatively be used under the terms
+ * of the Common Development and Distribution License Version 1.0
+ * (CDDL) only, as it comes in the "COPYING.CDDL" file of the
+ * VirtualBox OSE distribution, in which case the provisions of the
+ * CDDL are applicable instead of those of the GPL.
+ *
+ * You may elect to license modified versions of this file under the
+ * terms and conditions of either the GPL or the CDDL or both.
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP RTLOGGROUP_IOQUEUE
+#include <iprt/ioqueue.h>
+
+#include <iprt/asm.h>
+#include <iprt/errcore.h>
+#include <iprt/file.h>
+#include <iprt/log.h>
+#include <iprt/mem.h>
+#include <iprt/semaphore.h>
+#include <iprt/string.h>
+
+#include "internal/ioqueue.h"
+
+
+/*********************************************************************************************************************************
+*   Structures and Typedefs                                                                                                      *
+*********************************************************************************************************************************/
+
+
+/**
+ * Internal I/O queue provider instance data.
+ */
+typedef struct RTIOQUEUEPROVINT
+{
+    /** The async I/O context handle. */
+    RTFILEAIOCTX                hAioCtx;
+    /** Pointer to the array of requests waiting for commit. */
+    PRTFILEAIOREQ               pahReqsToCommit;
+    /** Maximum number of requests to wait for commit.. */
+    size_t                      cReqsToCommitMax;
+    /** Number of requests waiting for commit. */
+    uint32_t                    cReqsToCommit;
+    /** Array of free cached request handles. */
+    PRTFILEAIOREQ               pahReqsFree;
+    /** Maximum number of cached requests. */
+    uint32_t                    cReqsFreeMax;
+    /** Number of free cached requests. */
+    volatile uint32_t           cReqsFree;
+} RTIOQUEUEPROVINT;
+/** Pointer to the internal I/O queue provider instance data. */
+typedef RTIOQUEUEPROVINT *PRTIOQUEUEPROVINT;
+
+
+/*********************************************************************************************************************************
+*   Internal Functions                                                                                                           *
+*********************************************************************************************************************************/
+
+
+/** @interface_method_impl{RTIOQUEUEPROVVTABLE,pfnIsSupported} */
+static DECLCALLBACK(bool) rtIoQueueAioFileProv_IsSupported(void)
+{
+    /* The common code/public API already checked for the proper handle type. */
+    /** @todo Check that the file was opened with async I/O enabled on some platforms? */
+    return true;
+}
+
+
+/** @interface_method_impl{RTIOQUEUEPROVVTABLE,pfnQueueInit} */
+static DECLCALLBACK(int) rtIoQueueAioFileProv_QueueInit(RTIOQUEUEPROV hIoQueueProv, uint32_t fFlags,
+                                                        uint32_t cSqEntries, uint32_t cCqEntries)
+{
+    RT_NOREF(fFlags, cCqEntries);
+
+    PRTIOQUEUEPROVINT pThis = hIoQueueProv;
+    int rc = VINF_SUCCESS;
+
+    pThis->cReqsToCommitMax = cSqEntries;
+    pThis->cReqsFreeMax     = cSqEntries;
+    pThis->cReqsFree        = 0;
+
+    pThis->pahReqsToCommit = (PRTFILEAIOREQ)RTMemAllocZ(cSqEntries * sizeof(PRTFILEAIOREQ));
+    if (RT_LIKELY(pThis->pahReqsToCommit))
+    {
+        pThis->pahReqsFree = (PRTFILEAIOREQ)RTMemAllocZ(cSqEntries * sizeof(PRTFILEAIOREQ));
+        if (RT_LIKELY(pThis->pahReqsFree))
+        {
+            rc = RTFileAioCtxCreate(&pThis->hAioCtx, cSqEntries, RTFILEAIOCTX_FLAGS_WAIT_WITHOUT_PENDING_REQUESTS);
+            if (RT_SUCCESS(rc))
+                return VINF_SUCCESS;
+
+            RTMemFree(pThis->pahReqsFree);
+        }
+        else
+            rc = VERR_NO_MEMORY;
+
+        RTMemFree(pThis->pahReqsToCommit);
+    }
+    else
+        rc = VERR_NO_MEMORY;
+
+    return rc;
+}
+
+
+/** @interface_method_impl{RTIOQUEUEPROVVTABLE,pfnQueueDestroy} */
+static DECLCALLBACK(void) rtIoQueueAioFileProv_QueueDestroy(RTIOQUEUEPROV hIoQueueProv)
+{
+    PRTIOQUEUEPROVINT pThis = hIoQueueProv;
+
+    RTFileAioCtxDestroy(pThis->hAioCtx);
+    RTMemFree(pThis->pahReqsFree);
+    RTMemFree(pThis->pahReqsToCommit);
+    RT_BZERO(pThis, sizeof(*pThis));
+}
+
+
+/** @interface_method_impl{RTIOQUEUEPROVVTABLE,pfnHandleRegister} */
+static DECLCALLBACK(int) rtIoQueueAioFileProv_HandleRegister(RTIOQUEUEPROV hIoQueueProv, PCRTHANDLE pHandle)
+{
+    PRTIOQUEUEPROVINT pThis = hIoQueueProv;
+
+    return RTFileAioCtxAssociateWithFile(pThis->hAioCtx, pHandle->u.hFile);
+}
+
+
+/** @interface_method_impl{RTIOQUEUEPROVVTABLE,pfnHandleDeregister} */
+static DECLCALLBACK(int) rtIoQueueAioFileProv_HandleDeregister(RTIOQUEUEPROV hIoQueueProv, PCRTHANDLE pHandle)
+{
+    RT_NOREF(hIoQueueProv, pHandle);
+
+    /** @todo For Windows there doesn't seem to be a way to deregister the file handle without reopening the file,
+     *.for all other hosts this is a nop, just like the register method.
+     */
+    return VINF_SUCCESS;
+}
+
+
+/** @interface_method_impl{RTIOQUEUEPROVVTABLE,pfnReqPrepare} */
+static DECLCALLBACK(int) rtIoQueueAioFileProv_ReqPrepare(RTIOQUEUEPROV hIoQueueProv, PCRTHANDLE pHandle, RTIOQUEUEOP enmOp,
+                                                         uint64_t off, void *pvBuf, size_t cbBuf, uint32_t fReqFlags,
+                                                         void *pvUser)
+{
+    RT_NOREF(fReqFlags);
+
+    PRTIOQUEUEPROVINT pThis = hIoQueueProv;
+
+    /* Try to grab a free request structure from the cache. */
+    RTFILEAIOREQ hReq = NIL_RTFILEAIOREQ;
+    int rc = VINF_SUCCESS;
+    uint32_t cReqsFree = ASMAtomicReadU32(&pThis->cReqsFree);
+    if (cReqsFree)
+    {
+        do
+        {
+            cReqsFree = ASMAtomicReadU32(&pThis->cReqsFree);
+            hReq = pThis->pahReqsFree[pThis->cReqsFree - 1];
+        } while (!ASMAtomicCmpXchgU32(&pThis->cReqsFree, cReqsFree - 1, cReqsFree));
+    }
+    else
+        rc = RTFileAioReqCreate(&hReq);
+
+    if (RT_SUCCESS(rc))
+    {
+        switch (enmOp)
+        {
+            case RTIOQUEUEOP_READ:
+                rc = RTFileAioReqPrepareRead(hReq, pHandle->u.hFile, (RTFOFF)off, pvBuf, cbBuf, pvUser);
+                break;
+            case RTIOQUEUEOP_WRITE:
+                rc = RTFileAioReqPrepareWrite(hReq, pHandle->u.hFile, (RTFOFF)off, pvBuf, cbBuf, pvUser);
+                break;
+            case RTIOQUEUEOP_SYNC:
+                rc = RTFileAioReqPrepareFlush(hReq, pHandle->u.hFile, pvUser);
+                break;
+            default:
+                AssertMsgFailedReturn(("Invalid I/O queue operation: %d\n", enmOp), VERR_INTERNAL_ERROR);
+        }
+
+        if (RT_SUCCESS(rc))
+            pThis->pahReqsToCommit[pThis->cReqsToCommit++] = hReq;
+        else
+        {
+            int rc2 = RTFileAioReqDestroy(hReq);
+            Assert(rc2); RT_NOREF(rc2);
+        }
+    }
+
+    return rc;
+}
+
+
+/** @interface_method_impl{RTIOQUEUEPROVVTABLE,pfnCommit} */
+static DECLCALLBACK(int) rtIoQueueAioFileProv_Commit(RTIOQUEUEPROV hIoQueueProv, uint32_t *pcReqsCommitted)
+{
+    PRTIOQUEUEPROVINT pThis = hIoQueueProv;
+
+    int rc = RTFileAioCtxSubmit(pThis->hAioCtx, pThis->pahReqsToCommit, pThis->cReqsToCommit);
+    if (RT_SUCCESS(rc))
+    {
+        *pcReqsCommitted = pThis->cReqsToCommit;
+        pThis->cReqsToCommit = 0;
+    }
+
+    return rc;
+}
+
+
+/** @interface_method_impl{RTIOQUEUEPROVVTABLE,pfnEvtWait} */
+static DECLCALLBACK(int) rtIoQueueAioFileProv_EvtWait(RTIOQUEUEPROV hIoQueueProv, PRTIOQUEUECEVT paCEvt, uint32_t cCEvt,
+                                                      uint32_t cMinWait, uint32_t *pcCEvt, uint32_t fFlags)
+{
+    RT_NOREF(fFlags);
+
+    PRTIOQUEUEPROVINT pThis = hIoQueueProv;
+    int rc = VINF_SUCCESS;
+    uint32_t idxCEvt = 0;
+
+    while (   RT_SUCCESS(rc)
+           && cMinWait
+           && cCEvt)
+    {
+        RTFILEAIOREQ ahReqs[64];
+        uint32_t cReqsCompleted = 0;
+
+        rc = RTFileAioCtxWait(pThis->hAioCtx, cMinWait, RT_INDEFINITE_WAIT,
+                              &ahReqs[0], RT_MIN(RT_ELEMENTS(ahReqs), cCEvt), &cReqsCompleted);
+        if (RT_SUCCESS(rc))
+        {
+            for (unsigned i = 0; i < cReqsCompleted; i++)
+            {
+                RTFILEAIOREQ hReq = ahReqs[i];
+
+                paCEvt[idxCEvt].rcReq    = RTFileAioReqGetRC(hReq, &paCEvt[idxCEvt].cbXfered);
+                paCEvt[idxCEvt].pvUser   = RTFileAioReqGetUser(hReq);
+                idxCEvt++;
+
+                /* Try to insert the free request into the cache. */
+                uint32_t cReqsFree = ASMAtomicReadU32(&pThis->cReqsFree);
+                if (cReqsFree < pThis->cReqsFreeMax)
+                {
+                    do
+                    {
+                        cReqsFree = ASMAtomicReadU32(&pThis->cReqsFree);
+                        pThis->pahReqsFree[pThis->cReqsFree] = hReq;
+                    } while (!ASMAtomicCmpXchgU32(&pThis->cReqsFree, cReqsFree + 1, cReqsFree));
+                }
+                else
+                    rc = RTFileAioReqDestroy(hReq);
+            }
+
+            cCEvt -= cReqsCompleted;
+            cMinWait -= RT_MIN(cMinWait, cReqsCompleted);
+        }
+    }
+
+    *pcCEvt = idxCEvt;
+    return rc;
+}
+
+
+/** @interface_method_impl{RTIOQUEUEPROVVTABLE,pfnEvtWaitWakeup} */
+static DECLCALLBACK(int) rtIoQueueAioFileProv_EvtWaitWakeup(RTIOQUEUEPROV hIoQueueProv)
+{
+    PRTIOQUEUEPROVINT pThis = hIoQueueProv;
+
+    return RTFileAioCtxWakeup(pThis->hAioCtx);
+}
+
+
+/**
+ * Async file I/O queue provider virtual method table.
+ */
+RT_DECL_DATA_CONST(RTIOQUEUEPROVVTABLE const) g_RTIoQueueAioFileProv =
+{
+    /** uVersion */
+    RTIOQUEUEPROVVTABLE_VERSION,
+    /** pszId */
+    "AioFile",
+    /** cbIoQueueProv */
+    sizeof(RTIOQUEUEPROVINT),
+    /** enmHnd */
+    RTHANDLETYPE_FILE,
+    /** fFlags */
+    0,
+    /** pfnIsSupported */
+    rtIoQueueAioFileProv_IsSupported,
+    /** pfnQueueInit  */
+    rtIoQueueAioFileProv_QueueInit,
+    /** pfnQueueDestroy */
+    rtIoQueueAioFileProv_QueueDestroy,
+    /** pfnHandleRegister */
+    rtIoQueueAioFileProv_HandleRegister,
+    /** pfnHandleDeregister */
+    rtIoQueueAioFileProv_HandleDeregister,
+    /** pfnReqPrepare */
+    rtIoQueueAioFileProv_ReqPrepare,
+    /** pfnReqPrepareSg */
+    NULL,
+    /** pfnCommit */
+    rtIoQueueAioFileProv_Commit,
+    /** pfnEvtWait */
+    rtIoQueueAioFileProv_EvtWait,
+    /** pfnEvtWaitWakeup */
+    rtIoQueueAioFileProv_EvtWaitWakeup,
+    /** uEndMarker */
+    RTIOQUEUEPROVVTABLE_VERSION
+};
+
diff --git a/src/VBox/Runtime/common/ioqueue/ioqueue-stdfile-provider.cpp b/src/VBox/Runtime/common/ioqueue/ioqueue-stdfile-provider.cpp
new file mode 100644
index 00000000..826fdabc
--- /dev/null
+++ b/src/VBox/Runtime/common/ioqueue/ioqueue-stdfile-provider.cpp
@@ -0,0 +1,539 @@
+/* $Id: ioqueue-stdfile-provider.cpp $ */
+/** @file
+ * IPRT - I/O queue, Standard file provider.
+ */
+
+/*
+ * Copyright (C) 2019-2020 Oracle Corporation
+ *
+ * This file is part of VirtualBox Open Source Edition (OSE), as
+ * available from http://www.virtualbox.org. This file is free software;
+ * you can redistribute it and/or modify it under the terms of the GNU
+ * General Public License (GPL) as published by the Free Software
+ * Foundation, in version 2 as it comes in the "COPYING" file of the
+ * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
+ * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
+ *
+ * The contents of this file may alternatively be used under the terms
+ * of the Common Development and Distribution License Version 1.0
+ * (CDDL) only, as it comes in the "COPYING.CDDL" file of the
+ * VirtualBox OSE distribution, in which case the provisions of the
+ * CDDL are applicable instead of those of the GPL.
+ *
+ * You may elect to license modified versions of this file under the
+ * terms and conditions of either the GPL or the CDDL or both.
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP RTLOGGROUP_IOQUEUE
+#include <iprt/ioqueue.h>
+
+#include <iprt/asm.h>
+#include <iprt/errcore.h>
+#include <iprt/file.h>
+#include <iprt/log.h>
+#include <iprt/mem.h>
+#include <iprt/semaphore.h>
+#include <iprt/string.h>
+#include <iprt/thread.h>
+
+#include "internal/ioqueue.h"
+
+
+/*********************************************************************************************************************************
+*   Defined Constants And Macros                                                                                                 *
+*********************************************************************************************************************************/
+
+/** The I/O queue worker thread needs to wake up the waiting thread when requests completed. */
+#define RTIOQUEUE_STDFILE_PROV_STATE_F_EVTWAIT_NEED_WAKEUP      RT_BIT(0)
+/** The waiting thread was interrupted by the external wakeup call. */
+#define RTIOQUEUE_STDFILE_PROV_STATE_F_EVTWAIT_INTR             RT_BIT(1)
+#define RTIOQUEUE_STDFILE_PROV_STATE_F_EVTWAIT_INTR_BIT         1
+/** The I/O queue worker thread needs to be woken up to process new requests. */
+#define RTIOQUEUE_STDFILE_PROV_STATE_F_WORKER_NEED_WAKEUP       RT_BIT(2)
+#define RTIOQUEUE_STDFILE_PROV_STATE_F_WORKER_NEED_WAKEUP_BIT   2
+
+
+/*********************************************************************************************************************************
+*   Structures and Typedefs                                                                                                      *
+*********************************************************************************************************************************/
+
+
+/**
+ * Submission queue entry.
+ */
+typedef struct RTIOQUEUESSQENTRY
+{
+    /** The file to work on. */
+    RTFILE                      hFile;
+    /** I/O operation. */
+    RTIOQUEUEOP                 enmOp;
+    /** Start offset. */
+    uint64_t                    off;
+    /** Additional request flags. */
+    uint32_t                    fReqFlags;
+    /** Size of the request. */
+    size_t                      cbReq;
+    /** Opaque user data passed on completion. */
+    void                        *pvUser;
+    /** Flag whether this is a S/G or standard request. */
+    bool                        fSg;
+    /** Type dependent data. */
+    union
+    {
+        /** Pointer to buffer for non S/G requests. */
+        void                    *pvBuf;
+        /** Pointer to S/G buffer. */
+        PCRTSGBUF               pSgBuf;
+    } u;
+} RTIOQUEUESSQENTRY;
+/** Pointer to a submission queue entry. */
+typedef RTIOQUEUESSQENTRY *PRTIOQUEUESSQENTRY;
+/** Pointer to a constant submission queue entry. */
+typedef const RTIOQUEUESSQENTRY *PCRTIOQUEUESSQENTRY;
+
+
+/**
+ * Internal I/O queue provider instance data.
+ */
+typedef struct RTIOQUEUEPROVINT
+{
+    /** Size of the submission queue in entries. */
+    uint32_t                    cSqEntries;
+    /** Size of the completion queue in entries. */
+    uint32_t                    cCqEntries;
+    /** Pointer to the submission queue base. */
+    PRTIOQUEUESSQENTRY          paSqEntryBase;
+    /** Submission queue producer index. */
+    volatile uint32_t           idxSqProd;
+    /** Submission queue producer value for any uncommitted requests. */
+    uint32_t                    idxSqProdUncommit;
+    /** Submission queue consumer index. */
+    volatile uint32_t           idxSqCons;
+    /** Pointer to the completion queue base. */
+    PRTIOQUEUECEVT              paCqEntryBase;
+    /** Completion queue producer index. */
+    volatile uint32_t           idxCqProd;
+    /** Completion queue consumer index. */
+    volatile uint32_t           idxCqCons;
+    /** Various state flags for synchronizing the worker thread with other participants. */
+    volatile uint32_t           fState;
+    /** The worker thread handle. */
+    RTTHREAD                    hThrdWork;
+    /** Event semaphore the worker thread waits on for work. */
+    RTSEMEVENT                  hSemEvtWorker;
+    /** Event semaphore the caller waits for completion events. */
+    RTSEMEVENT                  hSemEvtWaitEvts;
+    /** Flag whether to shutdown the worker thread. */
+    volatile bool               fShutdown;
+} RTIOQUEUEPROVINT;
+/** Pointer to the internal I/O queue provider instance data. */
+typedef RTIOQUEUEPROVINT *PRTIOQUEUEPROVINT;
+
+
+/*********************************************************************************************************************************
+*   Internal Functions                                                                                                           *
+*********************************************************************************************************************************/
+
+
+/**
+ * Processes the given submission queue entry and reports back the result in the completion queue.
+ *
+ * @returns nothing.
+ * @param   pSqEntry            The submission queue entry to process.
+ * @param   pCqEntry            The comppletion queue entry to store the result in.
+ */
+static void rtIoQueueStdFileProv_SqEntryProcess(PCRTIOQUEUESSQENTRY pSqEntry, PRTIOQUEUECEVT pCqEntry)
+{
+    int rcReq = VINF_SUCCESS;
+
+    switch (pSqEntry->enmOp)
+    {
+        case RTIOQUEUEOP_READ:
+            if (!pSqEntry->fSg)
+                rcReq = RTFileReadAt(pSqEntry->hFile, pSqEntry->off, pSqEntry->u.pvBuf, pSqEntry->cbReq, NULL);
+            else
+            {
+                RTSGBUF SgBuf;
+                RTSgBufClone(&SgBuf, pSqEntry->u.pSgBuf);
+                rcReq = RTFileSgReadAt(pSqEntry->hFile, pSqEntry->off, &SgBuf, pSqEntry->cbReq, NULL);
+            }
+            break;
+        case RTIOQUEUEOP_WRITE:
+            if (!pSqEntry->fSg)
+                rcReq = RTFileWriteAt(pSqEntry->hFile, pSqEntry->off, pSqEntry->u.pvBuf, pSqEntry->cbReq, NULL);
+            else
+            {
+                RTSGBUF SgBuf;
+                RTSgBufClone(&SgBuf, pSqEntry->u.pSgBuf);
+                rcReq = RTFileSgWriteAt(pSqEntry->hFile, pSqEntry->off, &SgBuf, pSqEntry->cbReq, NULL);
+            }
+            break;
+        case RTIOQUEUEOP_SYNC:
+            rcReq = RTFileFlush(pSqEntry->hFile);
+            break;
+        default:
+            AssertMsgFailedReturnVoid(("Invalid I/O queue operation: %d\n", pSqEntry->enmOp));
+    }
+
+    /* Write the result back into the completion queue. */
+    pCqEntry->rcReq    = rcReq;
+    pCqEntry->pvUser   = pSqEntry->pvUser;
+    pCqEntry->cbXfered = RT_SUCCESS(rcReq) ? pSqEntry->cbReq : 0;
+}
+
+
+/**
+ * The main I/O queue worker loop which processes the incoming I/O requests.
+ */
+static DECLCALLBACK(int) rtIoQueueStdFileProv_WorkerLoop(RTTHREAD hThrdSelf, void *pvUser)
+{
+    PRTIOQUEUEPROVINT pThis = (PRTIOQUEUEPROVINT)pvUser;
+
+    /* Signal that we started up. */
+    int rc = RTThreadUserSignal(hThrdSelf);
+    AssertRC(rc);
+
+    while (!ASMAtomicReadBool(&pThis->fShutdown))
+    {
+        /* Wait for some work. */
+        ASMAtomicOrU32(&pThis->fState, RTIOQUEUE_STDFILE_PROV_STATE_F_WORKER_NEED_WAKEUP);
+        uint32_t idxSqProd = ASMAtomicReadU32(&pThis->idxSqProd);
+        uint32_t idxSqCons = ASMAtomicReadU32(&pThis->idxSqCons);
+        uint32_t idxCqCons = ASMAtomicReadU32(&pThis->idxCqCons);
+
+        if (idxSqCons == idxSqProd)
+        {
+            rc = RTSemEventWait(pThis->hSemEvtWorker, RT_INDEFINITE_WAIT);
+            AssertRC(rc);
+
+            idxSqProd = ASMAtomicReadU32(&pThis->idxSqProd);
+            idxSqCons = ASMAtomicReadU32(&pThis->idxSqCons);
+            idxCqCons = ASMAtomicReadU32(&pThis->idxCqCons);
+        }
+
+        ASMAtomicBitTestAndClear(&pThis->fState, RTIOQUEUE_STDFILE_PROV_STATE_F_WORKER_NEED_WAKEUP_BIT);
+
+        /* Process all requests. */
+        uint32_t cCqFree = 0;
+        if (idxCqCons > pThis->idxCqProd)
+            cCqFree = pThis->cCqEntries - (pThis->cCqEntries - idxCqCons) - pThis->idxCqProd;
+        else
+            cCqFree = pThis->cCqEntries - pThis->idxCqProd - idxCqCons;
+        do
+        {
+            while (   idxSqCons != idxSqProd
+                   && cCqFree)
+            {
+                PCRTIOQUEUESSQENTRY pSqEntry = &pThis->paSqEntryBase[idxSqCons];
+                PRTIOQUEUECEVT pCqEntry = &pThis->paCqEntryBase[pThis->idxCqProd];
+
+                rtIoQueueStdFileProv_SqEntryProcess(pSqEntry, pCqEntry);
+                ASMWriteFence();
+
+                idxSqCons = (idxSqCons + 1) % pThis->cSqEntries;
+                cCqFree--;
+                pThis->idxCqProd = (pThis->idxCqProd + 1) % pThis->cCqEntries;
+                ASMAtomicWriteU32(&pThis->idxSqCons, idxSqCons);
+                ASMWriteFence();
+                if (ASMAtomicReadU32(&pThis->fState) & RTIOQUEUE_STDFILE_PROV_STATE_F_EVTWAIT_NEED_WAKEUP)
+                {
+                    rc = RTSemEventSignal(pThis->hSemEvtWaitEvts);
+                    AssertRC(rc);
+                }
+            }
+
+            idxSqProd = ASMAtomicReadU32(&pThis->idxSqProd);
+        } while (   idxSqCons != idxSqProd
+                 && cCqFree);
+    }
+
+    return VINF_SUCCESS;
+}
+
+
+/** @interface_method_impl{RTIOQUEUEPROVVTABLE,pfnIsSupported} */
+static DECLCALLBACK(bool) rtIoQueueStdFileProv_IsSupported(void)
+{
+    /* The common code/public API already checked for the proper handle type. */
+    return true;
+}
+
+
+/** @interface_method_impl{RTIOQUEUEPROVVTABLE,pfnQueueInit} */
+static DECLCALLBACK(int) rtIoQueueStdFileProv_QueueInit(RTIOQUEUEPROV hIoQueueProv, uint32_t fFlags,
+                                                        uint32_t cSqEntries, uint32_t cCqEntries)
+{
+    RT_NOREF(fFlags);
+
+    PRTIOQUEUEPROVINT pThis = hIoQueueProv;
+    int rc = VINF_SUCCESS;
+
+    cSqEntries++;
+    cCqEntries++;
+
+    pThis->cSqEntries        = cSqEntries;
+    pThis->cCqEntries        = cCqEntries;
+    pThis->idxSqProd         = 0;
+    pThis->idxSqProdUncommit = 0;
+    pThis->idxSqCons         = 0;
+    pThis->idxCqProd         = 0;
+    pThis->idxCqCons         = 0;
+    pThis->fShutdown         = false;
+    pThis->fState            = 0;
+
+    pThis->paSqEntryBase = (PRTIOQUEUESSQENTRY)RTMemAllocZ(cSqEntries * sizeof(RTIOQUEUESSQENTRY));
+    if (RT_LIKELY(pThis->paSqEntryBase))
+    {
+        pThis->paCqEntryBase = (PRTIOQUEUECEVT)RTMemAllocZ(cCqEntries * sizeof(RTIOQUEUECEVT));
+        if (RT_LIKELY(pThis->paSqEntryBase))
+        {
+            rc = RTSemEventCreate(&pThis->hSemEvtWorker);
+            if (RT_SUCCESS(rc))
+            {
+                rc = RTSemEventCreate(&pThis->hSemEvtWaitEvts);
+                if (RT_SUCCESS(rc))
+                {
+                    /* Spin up the worker thread. */
+                    rc = RTThreadCreate(&pThis->hThrdWork, rtIoQueueStdFileProv_WorkerLoop, pThis, 0, RTTHREADTYPE_IO, RTTHREADFLAGS_WAITABLE,
+                                        "IoQ-StdFile");
+                    if (RT_SUCCESS(rc))
+                    {
+                        rc = RTThreadUserWait(pThis->hThrdWork, 10 * RT_MS_1SEC);
+                        AssertRC(rc);
+
+                        return VINF_SUCCESS;
+                    }
+
+                    RTSemEventDestroy(pThis->hSemEvtWaitEvts);
+                }
+
+                RTSemEventDestroy(pThis->hSemEvtWorker);
+            }
+
+            RTMemFree(pThis->paCqEntryBase);
+        }
+        else
+            rc = VERR_NO_MEMORY;
+
+        RTMemFree(pThis->paSqEntryBase);
+    }
+    else
+        rc = VERR_NO_MEMORY;
+
+    return rc;
+}
+
+
+/** @interface_method_impl{RTIOQUEUEPROVVTABLE,pfnQueueDestroy} */
+static DECLCALLBACK(void) rtIoQueueStdFileProv_QueueDestroy(RTIOQUEUEPROV hIoQueueProv)
+{
+    PRTIOQUEUEPROVINT pThis = hIoQueueProv;
+
+    ASMAtomicXchgBool(&pThis->fShutdown, true);
+    RTSemEventSignal(pThis->hSemEvtWorker);
+
+    int rc = RTThreadWait(pThis->hThrdWork, 60 * RT_MS_1SEC, NULL);
+    AssertRC(rc);
+
+    RTSemEventDestroy(pThis->hSemEvtWaitEvts);
+    RTSemEventDestroy(pThis->hSemEvtWorker);
+    RTMemFree(pThis->paCqEntryBase);
+    RTMemFree(pThis->paSqEntryBase);
+    RT_BZERO(pThis, sizeof(*pThis));
+}
+
+
+/** @interface_method_impl{RTIOQUEUEPROVVTABLE,pfnHandleRegister} */
+static DECLCALLBACK(int) rtIoQueueStdFileProv_HandleRegister(RTIOQUEUEPROV hIoQueueProv, PCRTHANDLE pHandle)
+{
+    RT_NOREF(hIoQueueProv, pHandle);
+
+    /* Nothing to do here. */
+    return VINF_SUCCESS;
+}
+
+
+/** @interface_method_impl{RTIOQUEUEPROVVTABLE,pfnHandleDeregister} */
+static DECLCALLBACK(int) rtIoQueueStdFileProv_HandleDeregister(RTIOQUEUEPROV hIoQueueProv, PCRTHANDLE pHandle)
+{
+    RT_NOREF(hIoQueueProv, pHandle);
+
+    /* Nothing to do here. */
+    return VINF_SUCCESS;
+}
+
+
+/** @interface_method_impl{RTIOQUEUEPROVVTABLE,pfnReqPrepare} */
+static DECLCALLBACK(int) rtIoQueueStdFileProv_ReqPrepare(RTIOQUEUEPROV hIoQueueProv, PCRTHANDLE pHandle, RTIOQUEUEOP enmOp,
+                                                         uint64_t off, void *pvBuf, size_t cbBuf, uint32_t fReqFlags,
+                                                         void *pvUser)
+{
+    PRTIOQUEUEPROVINT pThis = hIoQueueProv;
+    PRTIOQUEUESSQENTRY pSqEntry = &pThis->paSqEntryBase[pThis->idxSqProdUncommit];
+
+    pSqEntry->hFile     = pHandle->u.hFile;
+    pSqEntry->enmOp     = enmOp;
+    pSqEntry->off       = off;
+    pSqEntry->fReqFlags = fReqFlags;
+    pSqEntry->cbReq     = cbBuf;
+    pSqEntry->pvUser    = pvUser;
+    pSqEntry->fSg       = false;
+    pSqEntry->u.pvBuf   = pvBuf;
+
+    pThis->idxSqProdUncommit = (pThis->idxSqProdUncommit + 1) % pThis->cSqEntries;
+    return VINF_SUCCESS;
+}
+
+
+/** @interface_method_impl{RTIOQUEUEPROVVTABLE,pfnReqPrepareSg} */
+static DECLCALLBACK(int) rtIoQueueStdFileProv_ReqPrepareSg(RTIOQUEUEPROV hIoQueueProv, PCRTHANDLE pHandle, RTIOQUEUEOP enmOp,
+                                                           uint64_t off, PCRTSGBUF pSgBuf, size_t cbSg, uint32_t fReqFlags,
+                                                           void *pvUser)
+{
+    PRTIOQUEUEPROVINT pThis = hIoQueueProv;
+    PRTIOQUEUESSQENTRY pSqEntry = &pThis->paSqEntryBase[pThis->idxSqProdUncommit];
+
+    pSqEntry->hFile     = pHandle->u.hFile;
+    pSqEntry->enmOp     = enmOp;
+    pSqEntry->off       = off;
+    pSqEntry->fReqFlags = fReqFlags;
+    pSqEntry->cbReq     = cbSg;
+    pSqEntry->pvUser    = pvUser;
+    pSqEntry->fSg       = true;
+    pSqEntry->u.pSgBuf  = pSgBuf;
+
+    pThis->idxSqProdUncommit = (pThis->idxSqProdUncommit + 1) % pThis->cSqEntries;
+    return VINF_SUCCESS;
+}
+
+
+/** @interface_method_impl{RTIOQUEUEPROVVTABLE,pfnCommit} */
+static DECLCALLBACK(int) rtIoQueueStdFileProv_Commit(RTIOQUEUEPROV hIoQueueProv, uint32_t *pcReqsCommitted)
+{
+    PRTIOQUEUEPROVINT pThis = hIoQueueProv;
+
+    if (pThis->idxSqProd > pThis->idxSqProdUncommit)
+        *pcReqsCommitted = pThis->cSqEntries - pThis->idxSqProd + pThis->idxSqProdUncommit;
+    else
+        *pcReqsCommitted = pThis->idxSqProdUncommit - pThis->idxSqProd;
+
+    ASMWriteFence();
+    ASMAtomicWriteU32(&pThis->idxSqProd, pThis->idxSqProdUncommit);
+    return RTSemEventSignal(pThis->hSemEvtWorker);
+}
+
+
+/** @interface_method_impl{RTIOQUEUEPROVVTABLE,pfnEvtWait} */
+static DECLCALLBACK(int) rtIoQueueStdFileProv_EvtWait(RTIOQUEUEPROV hIoQueueProv, PRTIOQUEUECEVT paCEvt, uint32_t cCEvt,
+                                                      uint32_t cMinWait, uint32_t *pcCEvt, uint32_t fFlags)
+{
+    RT_NOREF(fFlags);
+
+    PRTIOQUEUEPROVINT pThis = hIoQueueProv;
+    int rc = VINF_SUCCESS;
+    uint32_t idxCEvt = 0;
+
+    while (   RT_SUCCESS(rc)
+           && cMinWait
+           && cCEvt)
+    {
+        ASMAtomicOrU32(&pThis->fState, RTIOQUEUE_STDFILE_PROV_STATE_F_EVTWAIT_NEED_WAKEUP);
+        uint32_t idxCqProd = ASMAtomicReadU32(&pThis->idxCqProd);
+        uint32_t idxCqCons = ASMAtomicReadU32(&pThis->idxCqCons);
+
+        if (idxCqCons == idxCqProd)
+        {
+            rc = RTSemEventWait(pThis->hSemEvtWaitEvts, RT_INDEFINITE_WAIT);
+            AssertRC(rc);
+            if (ASMAtomicBitTestAndClear(&pThis->fState, RTIOQUEUE_STDFILE_PROV_STATE_F_EVTWAIT_INTR_BIT))
+            {
+                rc = VERR_INTERRUPTED;
+                ASMAtomicBitTestAndClear(&pThis->fState, RTIOQUEUE_STDFILE_PROV_STATE_F_WORKER_NEED_WAKEUP_BIT);
+                break;
+            }
+
+            idxCqProd = ASMAtomicReadU32(&pThis->idxCqProd);
+            idxCqCons = ASMAtomicReadU32(&pThis->idxCqCons);
+        }
+
+        ASMAtomicBitTestAndClear(&pThis->fState, RTIOQUEUE_STDFILE_PROV_STATE_F_WORKER_NEED_WAKEUP_BIT);
+
+        /* Process all requests. */
+        while (   idxCqCons != idxCqProd
+               && cCEvt)
+        {
+            PRTIOQUEUECEVT pCqEntry = &pThis->paCqEntryBase[idxCqCons];
+
+            paCEvt[idxCEvt].rcReq    = pCqEntry->rcReq;
+            paCEvt[idxCEvt].pvUser   = pCqEntry->pvUser;
+            paCEvt[idxCEvt].cbXfered = pCqEntry->cbXfered;
+            ASMReadFence();
+
+            idxCEvt++;
+            cCEvt--;
+            cMinWait--;
+
+            idxCqCons = (idxCqCons + 1) % pThis->cCqEntries;
+            pThis->idxCqCons = (pThis->idxCqCons + 1) % pThis->cCqEntries;
+            ASMWriteFence();
+        }
+    }
+
+    *pcCEvt = idxCEvt;
+    return rc;
+}
+
+
+/** @interface_method_impl{RTIOQUEUEPROVVTABLE,pfnEvtWaitWakeup} */
+static DECLCALLBACK(int) rtIoQueueStdFileProv_EvtWaitWakeup(RTIOQUEUEPROV hIoQueueProv)
+{
+    PRTIOQUEUEPROVINT pThis = hIoQueueProv;
+
+    ASMAtomicOrU32(&pThis->fState, RTIOQUEUE_STDFILE_PROV_STATE_F_EVTWAIT_INTR);
+    return RTSemEventSignal(pThis->hSemEvtWaitEvts);
+}
+
+
+/**
+ * Standard file I/O queue provider virtual method table.
+ */
+RT_DECL_DATA_CONST(RTIOQUEUEPROVVTABLE const) g_RTIoQueueStdFileProv =
+{
+    /** uVersion */
+    RTIOQUEUEPROVVTABLE_VERSION,
+    /** pszId */
+    "StdFile",
+    /** cbIoQueueProv */
+    sizeof(RTIOQUEUEPROVINT),
+    /** enmHnd */
+    RTHANDLETYPE_FILE,
+    /** fFlags */
+    0,
+    /** pfnIsSupported */
+    rtIoQueueStdFileProv_IsSupported,
+    /** pfnQueueInit  */
+    rtIoQueueStdFileProv_QueueInit,
+    /** pfnQueueDestroy */
+    rtIoQueueStdFileProv_QueueDestroy,
+    /** pfnHandleRegister */
+    rtIoQueueStdFileProv_HandleRegister,
+    /** pfnHandleDeregister */
+    rtIoQueueStdFileProv_HandleDeregister,
+    /** pfnReqPrepare */
+    rtIoQueueStdFileProv_ReqPrepare,
+    /** pfnReqPrepareSg */
+    rtIoQueueStdFileProv_ReqPrepareSg,
+    /** pfnCommit */
+    rtIoQueueStdFileProv_Commit,
+    /** pfnEvtWait */
+    rtIoQueueStdFileProv_EvtWait,
+    /** pfnEvtWaitWakeup */
+    rtIoQueueStdFileProv_EvtWaitWakeup,
+    /** uEndMarker */
+    RTIOQUEUEPROVVTABLE_VERSION
+};
+
diff --git a/src/VBox/Runtime/common/ioqueue/ioqueuebase.cpp b/src/VBox/Runtime/common/ioqueue/ioqueuebase.cpp
new file mode 100644
index 00000000..28ecf1af
--- /dev/null
+++ b/src/VBox/Runtime/common/ioqueue/ioqueuebase.cpp
@@ -0,0 +1,287 @@
+/* $Id: ioqueuebase.cpp $ */
+/** @file
+ * IPRT - I/O queue, Base/Public API.
+ */
+
+/*
+ * Copyright (C) 2019-2020 Oracle Corporation
+ *
+ * This file is part of VirtualBox Open Source Edition (OSE), as
+ * available from http://www.virtualbox.org. This file is free software;
+ * you can redistribute it and/or modify it under the terms of the GNU
+ * General Public License (GPL) as published by the Free Software
+ * Foundation, in version 2 as it comes in the "COPYING" file of the
+ * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
+ * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
+ *
+ * The contents of this file may alternatively be used under the terms
+ * of the Common Development and Distribution License Version 1.0
+ * (CDDL) only, as it comes in the "COPYING.CDDL" file of the
+ * VirtualBox OSE distribution, in which case the provisions of the
+ * CDDL are applicable instead of those of the GPL.
+ *
+ * You may elect to license modified versions of this file under the
+ * terms and conditions of either the GPL or the CDDL or both.
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP RTLOGGROUP_IOQUEUE
+#include <iprt/ioqueue.h>
+
+#include <iprt/asm.h>
+#include <iprt/err.h>
+#include <iprt/log.h>
+#include <iprt/mem.h>
+#include <iprt/semaphore.h>
+#include <iprt/string.h>
+
+#include "internal/ioqueue.h"
+
+
+/*********************************************************************************************************************************
+*   Defined Constants And Macros                                                                                                 *
+*********************************************************************************************************************************/
+
+
+
+/*********************************************************************************************************************************
+*   Structures and Typedefs                                                                                                      *
+*********************************************************************************************************************************/
+
+/**
+ * Internal I/O queue instance data.
+ */
+typedef struct RTIOQUEUEINT
+{
+    /** Magic identifying the I/O queue structure. */
+    uint32_t                    u32Magic;
+    /** Pointer to the provider vtable. */
+    PCRTIOQUEUEPROVVTABLE       pVTbl;
+    /** I/O queue provider instance handle. */
+    RTIOQUEUEPROV               hIoQueueProv;
+    /** Maximum number of submission queue entries - constant. */
+    uint32_t                    cSqEntries;
+    /** Maximum number of completion queue entries - constant. */
+    uint32_t                    cCqEntries;
+    /** Number of currently committed and not completed requests. */
+    volatile uint32_t           cReqsCommitted;
+    /** Number of prepared requests. */
+    volatile uint32_t           cReqsPrepared;
+    /** Start of the provider specific instance data - vvariable in size. */
+    uint8_t                     abInst[1];
+} RTIOQUEUEINT;
+/** Pointer to the internal I/O queue instance data. */
+typedef RTIOQUEUEINT *PRTIOQUEUEINT;
+
+
+/*********************************************************************************************************************************
+*   Global Variables                                                                                                             *
+*********************************************************************************************************************************/
+/** Array of I/O queue providers we know about, order is important for each type.
+ * The best suited ones for each platform should come first.
+ */
+static PCRTIOQUEUEPROVVTABLE g_apIoQueueProviders[] =
+{
+#if defined(RT_OS_LINUX)
+    &g_RTIoQueueLnxIoURingProv,
+#endif
+#ifndef RT_OS_OS2
+    &g_RTIoQueueAioFileProv,
+#endif
+    &g_RTIoQueueStdFileProv
+};
+
+
+/*********************************************************************************************************************************
+*   Internal Functions                                                                                                           *
+*********************************************************************************************************************************/
+
+
+RTDECL(PCRTIOQUEUEPROVVTABLE) RTIoQueueProviderGetBestForHndType(RTHANDLETYPE enmHnd)
+{
+    /* Go through the array and pick the first supported provider for the given handle type. */
+    for (unsigned i = 0; i < RT_ELEMENTS(g_apIoQueueProviders); i++)
+    {
+        PCRTIOQUEUEPROVVTABLE pIoQueueProv = g_apIoQueueProviders[i];
+        if (   pIoQueueProv->enmHnd == enmHnd
+            && pIoQueueProv->pfnIsSupported())
+            return pIoQueueProv;
+    }
+
+    return NULL;
+}
+
+
+RTDECL(PCRTIOQUEUEPROVVTABLE) RTIoQueueProviderGetById(const char *pszId)
+{
+    for (unsigned i = 0; i < RT_ELEMENTS(g_apIoQueueProviders); i++)
+    {
+        PCRTIOQUEUEPROVVTABLE pIoQueueProv = g_apIoQueueProviders[i];
+        if (!strcmp(pIoQueueProv->pszId, pszId))
+            return pIoQueueProv;
+    }
+
+    return NULL;
+}
+
+
+RTDECL(int) RTIoQueueCreate(PRTIOQUEUE phIoQueue, PCRTIOQUEUEPROVVTABLE pProvVTable,
+                            uint32_t fFlags, uint32_t cSqEntries, uint32_t cCqEntries)
+{
+    AssertPtrReturn(phIoQueue, VERR_INVALID_POINTER);
+    AssertPtrReturn(pProvVTable, VERR_INVALID_POINTER);
+    AssertReturn(!fFlags, VERR_INVALID_PARAMETER);
+    AssertReturn(cSqEntries > 0, VERR_INVALID_PARAMETER);
+    AssertReturn(cCqEntries > 0, VERR_INVALID_PARAMETER);
+
+    int rc = VINF_SUCCESS;
+    PRTIOQUEUEINT pThis = (PRTIOQUEUEINT)RTMemAllocZ(RT_UOFFSETOF_DYN(RTIOQUEUEINT, abInst[pProvVTable->cbIoQueueProv]));
+    if (RT_LIKELY(pThis))
+    {
+        pThis->pVTbl          = pProvVTable;
+        pThis->hIoQueueProv   = (RTIOQUEUEPROV)&pThis->abInst[0];
+        pThis->cSqEntries     = cSqEntries;
+        pThis->cCqEntries     = cCqEntries;
+        pThis->cReqsCommitted = 0;
+        pThis->cReqsPrepared  = 0;
+
+        rc = pThis->pVTbl->pfnQueueInit(pThis->hIoQueueProv, fFlags, cSqEntries, cCqEntries);
+        if (RT_SUCCESS(rc))
+        {
+            *phIoQueue = pThis;
+            return VINF_SUCCESS;
+        }
+
+        RTMemFree(pThis);
+    }
+    else
+        rc = VERR_NO_MEMORY;
+
+    return rc;
+}
+
+
+RTDECL(int) RTIoQueueDestroy(RTIOQUEUE hIoQueue)
+{
+    PRTIOQUEUEINT pThis = hIoQueue;
+    AssertPtrReturn(pThis, VERR_INVALID_HANDLE);
+    AssertReturn(ASMAtomicReadU32(&pThis->cReqsCommitted) == 0, VERR_IOQUEUE_BUSY);
+
+    pThis->pVTbl->pfnQueueDestroy(pThis->hIoQueueProv);
+    RTMemFree(pThis);
+    return VINF_SUCCESS;
+}
+
+
+RTDECL(int) RTIoQueueHandleRegister(RTIOQUEUE hIoQueue, PCRTHANDLE pHandle)
+{
+    PRTIOQUEUEINT pThis = hIoQueue;
+    AssertPtrReturn(pThis, VERR_INVALID_HANDLE);
+
+    /** @todo Efficiently check that handle wasn't registered previously. */
+    return pThis->pVTbl->pfnHandleRegister(pThis->hIoQueueProv, pHandle);
+}
+
+
+RTDECL(int) RTIoQueueHandleDeregister(RTIOQUEUE hIoQueue, PCRTHANDLE pHandle)
+{
+    PRTIOQUEUEINT pThis = hIoQueue;
+    AssertPtrReturn(pThis, VERR_INVALID_HANDLE);
+
+    /** @todo Efficiently check that handle was registered previously. */
+    return pThis->pVTbl->pfnHandleDeregister(pThis->hIoQueueProv, pHandle);
+}
+
+
+RTDECL(int) RTIoQueueRequestPrepare(RTIOQUEUE hIoQueue, PCRTHANDLE pHandle, RTIOQUEUEOP enmOp,
+                                    uint64_t off, void *pvBuf, size_t cbBuf, uint32_t fReqFlags,
+                                    void *pvUser)
+{
+    PRTIOQUEUEINT pThis = hIoQueue;
+    AssertPtrReturn(pThis, VERR_INVALID_HANDLE);
+    AssertReturn(pHandle->enmType == pThis->pVTbl->enmHnd, VERR_INVALID_HANDLE);
+
+    /** @todo Efficiently check that handle was registered previously. */
+    int rc = pThis->pVTbl->pfnReqPrepare(pThis->hIoQueueProv, pHandle, enmOp, off, pvBuf, cbBuf,
+                                         fReqFlags, pvUser);
+    if (RT_SUCCESS(rc))
+        ASMAtomicIncU32(&pThis->cReqsPrepared);
+
+    return rc;
+}
+
+
+RTDECL(int) RTIoQueueRequestPrepareSg(RTIOQUEUE hIoQueue, PCRTHANDLE pHandle, RTIOQUEUEOP enmOp,
+                                      uint64_t off, PCRTSGBUF pSgBuf, size_t cbSg, uint32_t fReqFlags,
+                                      void *pvUser)
+{
+    PRTIOQUEUEINT pThis = hIoQueue;
+    AssertPtrReturn(pThis, VERR_INVALID_HANDLE);
+    AssertReturn(pHandle->enmType == pThis->pVTbl->enmHnd, VERR_INVALID_HANDLE);
+
+    /** @todo Efficiently check that handle was registered previously. */
+    int rc = pThis->pVTbl->pfnReqPrepareSg(pThis->hIoQueueProv, pHandle, enmOp, off, pSgBuf, cbSg,
+                                           fReqFlags, pvUser);
+    if (RT_SUCCESS(rc))
+        ASMAtomicIncU32(&pThis->cReqsPrepared);
+
+    return rc;
+}
+
+
+RTDECL(int) RTIoQueueCommit(RTIOQUEUE hIoQueue)
+{
+    PRTIOQUEUEINT pThis = hIoQueue;
+    AssertPtrReturn(pThis, VERR_INVALID_HANDLE);
+    AssertReturn(ASMAtomicReadU32(&pThis->cReqsPrepared) > 0, VERR_IOQUEUE_EMPTY);
+
+    uint32_t cReqsPreparedOld = 0;
+    uint32_t cReqsCommitted = 0;
+    int rc = VINF_SUCCESS;
+    do
+    {
+        rc = pThis->pVTbl->pfnCommit(pThis->hIoQueueProv, &cReqsCommitted);
+        if (RT_SUCCESS(rc))
+        {
+            ASMAtomicAddU32(&pThis->cReqsCommitted, cReqsCommitted);
+            cReqsPreparedOld = ASMAtomicSubU32(&pThis->cReqsPrepared, cReqsCommitted);
+        }
+    } while (RT_SUCCESS(rc) && cReqsPreparedOld - cReqsCommitted > 0);
+
+    return rc;
+}
+
+
+RTDECL(int) RTIoQueueEvtWait(RTIOQUEUE hIoQueue, PRTIOQUEUECEVT paCEvt, uint32_t cCEvt, uint32_t cMinWait,
+                             uint32_t *pcCEvt, uint32_t fFlags)
+{
+    PRTIOQUEUEINT pThis = hIoQueue;
+    AssertPtrReturn(pThis, VERR_INVALID_HANDLE);
+    AssertPtrReturn(paCEvt, VERR_INVALID_POINTER);
+    AssertReturn(cCEvt > 0, VERR_INVALID_PARAMETER);
+    AssertReturn(cMinWait > 0, VERR_INVALID_PARAMETER);
+    AssertPtrReturn(pcCEvt, VERR_INVALID_POINTER);
+    AssertReturn(!fFlags, VERR_INVALID_PARAMETER);
+    AssertReturn(ASMAtomicReadU32(&pThis->cReqsCommitted) > 0, VERR_IOQUEUE_EMPTY);
+
+    *pcCEvt = 0;
+    int rc = pThis->pVTbl->pfnEvtWait(pThis->hIoQueueProv, paCEvt, cCEvt, cMinWait, pcCEvt, fFlags);
+    if (   (RT_SUCCESS(rc) || rc == VERR_INTERRUPTED)
+        && *pcCEvt > 0)
+        ASMAtomicSubU32(&pThis->cReqsCommitted, *pcCEvt);
+
+    return rc;
+}
+
+
+RTDECL(int) RTIoQueueEvtWaitWakeup(RTIOQUEUE hIoQueue)
+{
+    PRTIOQUEUEINT pThis = hIoQueue;
+    AssertPtrReturn(pThis, VERR_INVALID_HANDLE);
+
+    return pThis->pVTbl->pfnEvtWaitWakeup(pThis->hIoQueueProv);
+}
+