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, 1320 insertions, 0 deletions

diff --git a/src/VBox/VMM/VMMAll/IOMAllMmioNew.cpp b/src/VBox/VMM/VMMAll/IOMAllMmioNew.cpp
new file mode 100644
index 00000000..c737bf1f
--- /dev/null
+++ b/src/VBox/VMM/VMMAll/IOMAllMmioNew.cpp
@@ -0,0 +1,1320 @@
+/* $Id: IOMAllMmioNew.cpp $ */
+/** @file
+ * IOM - Input / Output Monitor - Any Context, MMIO & String I/O.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_IOM_MMIO
+#define VMCPU_INCL_CPUM_GST_CTX
+#include <VBox/vmm/iom.h>
+#include <VBox/vmm/cpum.h>
+#include <VBox/vmm/pgm.h>
+#include <VBox/vmm/selm.h>
+#include <VBox/vmm/mm.h>
+#include <VBox/vmm/em.h>
+#include <VBox/vmm/pgm.h>
+#include <VBox/vmm/trpm.h>
+#include <VBox/vmm/iem.h>
+#include "IOMInternal.h"
+#include <VBox/vmm/vmcc.h>
+#include <VBox/vmm/vmm.h>
+#include <VBox/vmm/hm.h>
+#include "IOMInline.h"
+
+#include <VBox/dis.h>
+#include <VBox/disopcode.h>
+#include <VBox/vmm/pdmdev.h>
+#include <VBox/param.h>
+#include <VBox/err.h>
+#include <iprt/assert.h>
+#include <VBox/log.h>
+#include <iprt/asm.h>
+#include <iprt/string.h>
+
+
+/*********************************************************************************************************************************
+*   Defined Constants And Macros                                                                                                 *
+*********************************************************************************************************************************/
+/** @def IOM_MMIO_STATS_COMMA_DECL
+ * Parameter list declaration for statistics entry pointer. */
+/** @def IOM_MMIO_STATS_COMMA_ARG
+ * Statistics entry pointer argument. */
+#if defined(VBOX_WITH_STATISTICS) || defined(DOXYGEN_RUNNING)
+# define IOM_MMIO_STATS_COMMA_DECL , PIOMMMIOSTATSENTRY pStats
+# define IOM_MMIO_STATS_COMMA_ARG  , pStats
+#else
+# define IOM_MMIO_STATS_COMMA_DECL
+# define IOM_MMIO_STATS_COMMA_ARG
+#endif
+
+
+
+#ifndef IN_RING3
+/**
+ * Defers a pending MMIO write to ring-3.
+ *
+ * @returns VINF_IOM_R3_MMIO_COMMIT_WRITE
+ * @param   pVCpu       The cross context virtual CPU structure of the calling EMT.
+ * @param   GCPhys      The write address.
+ * @param   pvBuf       The bytes being written.
+ * @param   cbBuf       How many bytes.
+ * @param   idxRegEntry The MMIO registration index (handle) if available,
+ *                      otherwise UINT32_MAX.
+ */
+static VBOXSTRICTRC iomMmioRing3WritePending(PVMCPU pVCpu, RTGCPHYS GCPhys, void const *pvBuf, size_t cbBuf,
+                                             uint32_t idxRegEntry)
+{
+    Log5(("iomMmioRing3WritePending: %RGp LB %#x (idx=%#x)\n", GCPhys, cbBuf, idxRegEntry));
+    if (pVCpu->iom.s.PendingMmioWrite.cbValue == 0)
+    {
+        pVCpu->iom.s.PendingMmioWrite.GCPhys            = GCPhys;
+        AssertReturn(cbBuf <= sizeof(pVCpu->iom.s.PendingMmioWrite.abValue), VERR_IOM_MMIO_IPE_2);
+        pVCpu->iom.s.PendingMmioWrite.cbValue           = (uint32_t)cbBuf;
+        pVCpu->iom.s.PendingMmioWrite.idxMmioRegionHint = idxRegEntry;
+        memcpy(pVCpu->iom.s.PendingMmioWrite.abValue, pvBuf, cbBuf);
+    }
+    else
+    {
+        /*
+         * Join with pending if adjecent.
+         *
+         * This may happen if the stack overflows into MMIO territory and RSP/ESP/SP
+         * isn't aligned. IEM will bounce buffer the access and do one write for each
+         * page.  We get here when the 2nd page part is written.
+         */
+        uint32_t const cbOldValue = pVCpu->iom.s.PendingMmioWrite.cbValue;
+        AssertMsgReturn(GCPhys == pVCpu->iom.s.PendingMmioWrite.GCPhys + cbOldValue,
+                        ("pending %RGp LB %#x; incoming %RGp LB %#x\n",
+                         pVCpu->iom.s.PendingMmioWrite.GCPhys, cbOldValue, GCPhys, cbBuf),
+                        VERR_IOM_MMIO_IPE_1);
+        AssertReturn(cbBuf <= sizeof(pVCpu->iom.s.PendingMmioWrite.abValue) - cbOldValue, VERR_IOM_MMIO_IPE_2);
+        pVCpu->iom.s.PendingMmioWrite.cbValue = cbOldValue + (uint32_t)cbBuf;
+        memcpy(&pVCpu->iom.s.PendingMmioWrite.abValue[cbOldValue], pvBuf, cbBuf);
+    }
+
+    VMCPU_FF_SET(pVCpu, VMCPU_FF_IOM);
+    return VINF_IOM_R3_MMIO_COMMIT_WRITE;
+}
+#endif
+
+
+/**
+ * Deals with complicated MMIO writes.
+ *
+ * Complicated means unaligned or non-dword/qword sized accesses depending on
+ * the MMIO region's access mode flags.
+ *
+ * @returns Strict VBox status code. Any EM scheduling status code,
+ *          VINF_IOM_R3_MMIO_WRITE, VINF_IOM_R3_MMIO_READ_WRITE or
+ *          VINF_IOM_R3_MMIO_READ may be returned.
+ *
+ * @param   pVM         The cross context VM structure.
+ * @param   pVCpu       The cross context virtual CPU structure of the calling EMT.
+ * @param   pRegEntry   The MMIO entry for the current context.
+ * @param   GCPhys      The physical address to start writing.
+ * @param   offRegion   MMIO region offset corresponding to @a GCPhys.
+ * @param   pvValue     Where to store the value.
+ * @param   cbValue     The size of the value to write.
+ * @param   pStats      Pointer to the statistics (never NULL).
+ */
+static VBOXSTRICTRC iomMmioDoComplicatedWrite(PVM pVM, PVMCPU pVCpu, CTX_SUFF(PIOMMMIOENTRY) pRegEntry,
+                                              RTGCPHYS GCPhys, RTGCPHYS offRegion,
+                                              void const *pvValue, unsigned cbValue IOM_MMIO_STATS_COMMA_DECL)
+{
+    AssertReturn(   (pRegEntry->fFlags & IOMMMIO_FLAGS_WRITE_MODE) != IOMMMIO_FLAGS_WRITE_PASSTHRU
+                 && (pRegEntry->fFlags & IOMMMIO_FLAGS_WRITE_MODE) <= IOMMMIO_FLAGS_WRITE_DWORD_QWORD_READ_MISSING,
+                 VERR_IOM_MMIO_IPE_1);
+    AssertReturn(cbValue != 0 && cbValue <= 16, VERR_IOM_MMIO_IPE_2);
+    RTGCPHYS const GCPhysStart  = GCPhys; NOREF(GCPhysStart);
+    bool const     fReadMissing = (pRegEntry->fFlags & IOMMMIO_FLAGS_WRITE_MODE) == IOMMMIO_FLAGS_WRITE_DWORD_READ_MISSING
+                               || (pRegEntry->fFlags & IOMMMIO_FLAGS_WRITE_MODE) == IOMMMIO_FLAGS_WRITE_DWORD_QWORD_READ_MISSING;
+    RT_NOREF_PV(pVCpu); /* ring-3 */
+
+    /*
+     * Do debug stop if requested.
+     */
+    VBOXSTRICTRC rc = VINF_SUCCESS; NOREF(pVM);
+#ifdef VBOX_STRICT
+    if (!(pRegEntry->fFlags & IOMMMIO_FLAGS_DBGSTOP_ON_COMPLICATED_WRITE))
+    { /* likely */ }
+    else
+    {
+# ifdef IN_RING3
+        LogRel(("IOM: Complicated write %#x byte at %RGp to %s, initiating debugger intervention\n", cbValue, GCPhys,
+                R3STRING(pRegEntry->pszDesc)));
+        rc = DBGFR3EventSrc(pVM, DBGFEVENT_DEV_STOP, RT_SRC_POS,
+                            "Complicated write %#x byte at %RGp to %s\n", cbValue, GCPhys, pRegEntry->pszDesc);
+        if (rc == VERR_DBGF_NOT_ATTACHED)
+            rc = VINF_SUCCESS;
+# else
+        return VINF_IOM_R3_MMIO_WRITE;
+# endif
+    }
+#endif
+
+    STAM_COUNTER_INC(&pStats->ComplicatedWrites);
+
+    /*
+     * Check if we should ignore the write.
+     */
+    if ((pRegEntry->fFlags & IOMMMIO_FLAGS_WRITE_MODE) == IOMMMIO_FLAGS_WRITE_ONLY_DWORD)
+    {
+        Assert(cbValue != 4 || (GCPhys & 3));
+        return VINF_SUCCESS;
+    }
+    if ((pRegEntry->fFlags & IOMMMIO_FLAGS_WRITE_MODE) == IOMMMIO_FLAGS_WRITE_ONLY_DWORD_QWORD)
+    {
+        Assert((cbValue != 4 && cbValue != 8) || (GCPhys & (cbValue - 1)));
+        return VINF_SUCCESS;
+    }
+
+    /*
+     * Split and conquer.
+     */
+    for (;;)
+    {
+        unsigned const  offAccess  = GCPhys & 3;
+        unsigned        cbThisPart = 4 - offAccess;
+        if (cbThisPart > cbValue)
+            cbThisPart = cbValue;
+
+        /*
+         * Get the missing bits (if any).
+         */
+        uint32_t u32MissingValue = 0;
+        if (fReadMissing && cbThisPart != 4)
+        {
+            VBOXSTRICTRC rc2 = pRegEntry->pfnReadCallback(pRegEntry->pDevIns, pRegEntry->pvUser,
+                                                          !(pRegEntry->fFlags & IOMMMIO_FLAGS_ABS)
+                                                          ? offRegion & ~(RTGCPHYS)3 : (GCPhys & ~(RTGCPHYS)3),
+                                                          &u32MissingValue, sizeof(u32MissingValue));
+            switch (VBOXSTRICTRC_VAL(rc2))
+            {
+                case VINF_SUCCESS:
+                    break;
+                case VINF_IOM_MMIO_UNUSED_FF:
+                    STAM_COUNTER_INC(&pStats->FFor00Reads);
+                    u32MissingValue = UINT32_C(0xffffffff);
+                    break;
+                case VINF_IOM_MMIO_UNUSED_00:
+                    STAM_COUNTER_INC(&pStats->FFor00Reads);
+                    u32MissingValue = 0;
+                    break;
+#ifndef IN_RING3
+                case VINF_IOM_R3_MMIO_READ:
+                case VINF_IOM_R3_MMIO_READ_WRITE:
+                case VINF_IOM_R3_MMIO_WRITE:
+                    LogFlow(("iomMmioDoComplicatedWrite: GCPhys=%RGp GCPhysStart=%RGp cbValue=%u rc=%Rrc [read]\n", GCPhys, GCPhysStart, cbValue, VBOXSTRICTRC_VAL(rc2)));
+                    rc2 = iomMmioRing3WritePending(pVCpu, GCPhys, pvValue, cbValue, pRegEntry->idxSelf);
+                    if (rc == VINF_SUCCESS || rc2 < rc)
+                        rc = rc2;
+                    return rc;
+#endif
+                default:
+                    if (RT_FAILURE(rc2))
+                    {
+                        Log(("iomMmioDoComplicatedWrite: GCPhys=%RGp GCPhysStart=%RGp cbValue=%u rc=%Rrc [read]\n", GCPhys, GCPhysStart, cbValue, VBOXSTRICTRC_VAL(rc2)));
+                        return rc2;
+                    }
+                    AssertMsgReturn(rc2 >= VINF_EM_FIRST && rc2 <= VINF_EM_LAST, ("%Rrc\n", VBOXSTRICTRC_VAL(rc2)), VERR_IPE_UNEXPECTED_INFO_STATUS);
+                    if (rc == VINF_SUCCESS || rc2 < rc)
+                        rc = rc2;
+                    break;
+            }
+        }
+
+        /*
+         * Merge missing and given bits.
+         */
+        uint32_t u32GivenMask;
+        uint32_t u32GivenValue;
+        switch (cbThisPart)
+        {
+            case 1:
+                u32GivenValue = *(uint8_t  const *)pvValue;
+                u32GivenMask  = UINT32_C(0x000000ff);
+                break;
+            case 2:
+                u32GivenValue = *(uint16_t const *)pvValue;
+                u32GivenMask  = UINT32_C(0x0000ffff);
+                break;
+            case 3:
+                u32GivenValue = RT_MAKE_U32_FROM_U8(((uint8_t const *)pvValue)[0], ((uint8_t const *)pvValue)[1],
+                                                    ((uint8_t const *)pvValue)[2], 0);
+                u32GivenMask  = UINT32_C(0x00ffffff);
+                break;
+            case 4:
+                u32GivenValue = *(uint32_t const *)pvValue;
+                u32GivenMask  = UINT32_C(0xffffffff);
+                break;
+            default:
+                AssertFailedReturn(VERR_IOM_MMIO_IPE_3);
+        }
+        if (offAccess)
+        {
+            u32GivenValue <<= offAccess * 8;
+            u32GivenMask  <<= offAccess * 8;
+        }
+
+        uint32_t u32Value = (u32MissingValue & ~u32GivenMask)
+                          | (u32GivenValue & u32GivenMask);
+
+        /*
+         * Do DWORD write to the device.
+         */
+        VBOXSTRICTRC rc2 = pRegEntry->pfnWriteCallback(pRegEntry->pDevIns, pRegEntry->pvUser,
+                                                       !(pRegEntry->fFlags & IOMMMIO_FLAGS_ABS)
+                                                       ? offRegion & ~(RTGCPHYS)3 : GCPhys & ~(RTGCPHYS)3,
+                                                       &u32Value, sizeof(u32Value));
+        switch (VBOXSTRICTRC_VAL(rc2))
+        {
+            case VINF_SUCCESS:
+                break;
+#ifndef IN_RING3
+            case VINF_IOM_R3_MMIO_READ:
+            case VINF_IOM_R3_MMIO_READ_WRITE:
+            case VINF_IOM_R3_MMIO_WRITE:
+                Log3(("iomMmioDoComplicatedWrite: deferring GCPhys=%RGp GCPhysStart=%RGp cbValue=%u rc=%Rrc [write]\n", GCPhys, GCPhysStart, cbValue, VBOXSTRICTRC_VAL(rc2)));
+                AssertReturn(pVCpu->iom.s.PendingMmioWrite.cbValue == 0, VERR_IOM_MMIO_IPE_1);
+                AssertReturn(cbValue + (GCPhys & 3) <= sizeof(pVCpu->iom.s.PendingMmioWrite.abValue), VERR_IOM_MMIO_IPE_2);
+                pVCpu->iom.s.PendingMmioWrite.GCPhys  = GCPhys & ~(RTGCPHYS)3;
+                pVCpu->iom.s.PendingMmioWrite.cbValue = cbValue + (GCPhys & 3);
+                *(uint32_t *)pVCpu->iom.s.PendingMmioWrite.abValue = u32Value;
+                if (cbValue > cbThisPart)
+                    memcpy(&pVCpu->iom.s.PendingMmioWrite.abValue[4],
+                           (uint8_t const *)pvValue + cbThisPart, cbValue - cbThisPart);
+                VMCPU_FF_SET(pVCpu, VMCPU_FF_IOM);
+                if (rc == VINF_SUCCESS)
+                    rc = VINF_IOM_R3_MMIO_COMMIT_WRITE;
+                return rc;
+#endif
+            default:
+                if (RT_FAILURE(rc2))
+                {
+                    Log(("iomMmioDoComplicatedWrite: GCPhys=%RGp GCPhysStart=%RGp cbValue=%u rc=%Rrc [write]\n", GCPhys, GCPhysStart, cbValue, VBOXSTRICTRC_VAL(rc2)));
+                    return rc2;
+                }
+                AssertMsgReturn(rc2 >= VINF_EM_FIRST && rc2 <= VINF_EM_LAST, ("%Rrc\n", VBOXSTRICTRC_VAL(rc2)), VERR_IPE_UNEXPECTED_INFO_STATUS);
+                if (rc == VINF_SUCCESS || rc2 < rc)
+                    rc = rc2;
+                break;
+        }
+
+        /*
+         * Advance.
+         */
+        cbValue   -= cbThisPart;
+        if (!cbValue)
+            break;
+        GCPhys    += cbThisPart;
+        offRegion += cbThisPart;
+        pvValue    = (uint8_t const *)pvValue + cbThisPart;
+    }
+
+    return rc;
+}
+
+
+
+
+/**
+ * Wrapper which does the write.
+ */
+DECLINLINE(VBOXSTRICTRC) iomMmioDoWrite(PVMCC pVM, PVMCPU pVCpu, CTX_SUFF(PIOMMMIOENTRY) pRegEntry,
+                                        RTGCPHYS GCPhys, RTGCPHYS offRegion,
+                                        const void *pvData, uint32_t cb IOM_MMIO_STATS_COMMA_DECL)
+{
+    VBOXSTRICTRC rcStrict;
+    if (RT_LIKELY(pRegEntry->pfnWriteCallback))
+    {
+        if (   (cb == 4 && !(GCPhys & 3))
+            || (pRegEntry->fFlags & IOMMMIO_FLAGS_WRITE_MODE) == IOMMMIO_FLAGS_WRITE_PASSTHRU
+            || (cb == 8 && !(GCPhys & 7) && IOMMMIO_DOES_WRITE_MODE_ALLOW_QWORD(pRegEntry->fFlags)) )
+            rcStrict = pRegEntry->pfnWriteCallback(pRegEntry->pDevIns, pRegEntry->pvUser,
+                                                   !(pRegEntry->fFlags & IOMMMIO_FLAGS_ABS) ? offRegion : GCPhys, pvData, cb);
+        else
+            rcStrict = iomMmioDoComplicatedWrite(pVM, pVCpu, pRegEntry, GCPhys, offRegion, pvData, cb IOM_MMIO_STATS_COMMA_ARG);
+    }
+    else
+        rcStrict = VINF_SUCCESS;
+    return rcStrict;
+}
+
+
+#ifdef IN_RING3
+/**
+ * Helper for IOMR3ProcessForceFlag() that lives here to utilize iomMmioDoWrite et al.
+ */
+VBOXSTRICTRC iomR3MmioCommitWorker(PVM pVM, PVMCPU pVCpu, PIOMMMIOENTRYR3 pRegEntry, RTGCPHYS offRegion)
+{
+# ifdef VBOX_WITH_STATISTICS
+    STAM_PROFILE_START(UnusedMacroArg, Prf);
+    PIOMMMIOSTATSENTRY const pStats = iomMmioGetStats(pVM, pRegEntry);
+# endif
+    PPDMDEVINS const         pDevIns = pRegEntry->pDevIns;
+    int rc = PDMCritSectEnter(pVM, pDevIns->CTX_SUFF(pCritSectRo), VERR_IGNORED);
+    AssertRCReturn(rc, rc);
+
+    VBOXSTRICTRC rcStrict = iomMmioDoWrite(pVM, pVCpu, pRegEntry, pVCpu->iom.s.PendingMmioWrite.GCPhys, offRegion,
+                                           pVCpu->iom.s.PendingMmioWrite.abValue, pVCpu->iom.s.PendingMmioWrite.cbValue
+                                           IOM_MMIO_STATS_COMMA_ARG);
+
+    PDMCritSectLeave(pVM, pDevIns->CTX_SUFF(pCritSectRo));
+    STAM_PROFILE_STOP(&pStats->ProfWriteR3, Prf);
+    return rcStrict;
+}
+#endif /* IN_RING3 */
+
+
+/**
+ * Deals with complicated MMIO reads.
+ *
+ * Complicated means unaligned or non-dword/qword sized accesses depending on
+ * the MMIO region's access mode flags.
+ *
+ * @returns Strict VBox status code. Any EM scheduling status code,
+ *          VINF_IOM_R3_MMIO_READ, VINF_IOM_R3_MMIO_READ_WRITE or
+ *          VINF_IOM_R3_MMIO_WRITE may be returned.
+ *
+ * @param   pVM         The cross context VM structure.
+ * @param   pRegEntry   The MMIO entry for the current context.
+ * @param   GCPhys      The physical address to start reading.
+ * @param   offRegion   MMIO region offset corresponding to @a GCPhys.
+ * @param   pvValue     Where to store the value.
+ * @param   cbValue     The size of the value to read.
+ * @param   pStats      Pointer to the statistics (never NULL).
+ */
+static VBOXSTRICTRC iomMMIODoComplicatedRead(PVM pVM, CTX_SUFF(PIOMMMIOENTRY) pRegEntry, RTGCPHYS GCPhys, RTGCPHYS offRegion,
+                                             void *pvValue, unsigned cbValue IOM_MMIO_STATS_COMMA_DECL)
+{
+    AssertReturn(   (pRegEntry->fFlags & IOMMMIO_FLAGS_READ_MODE) == IOMMMIO_FLAGS_READ_DWORD
+                 || (pRegEntry->fFlags & IOMMMIO_FLAGS_READ_MODE) == IOMMMIO_FLAGS_READ_DWORD_QWORD,
+                 VERR_IOM_MMIO_IPE_1);
+    AssertReturn(cbValue != 0 && cbValue <= 16, VERR_IOM_MMIO_IPE_2);
+#ifdef LOG_ENABLED
+    RTGCPHYS const GCPhysStart = GCPhys;
+#endif
+
+    /*
+     * Do debug stop if requested.
+     */
+    VBOXSTRICTRC rc = VINF_SUCCESS; NOREF(pVM);
+#ifdef VBOX_STRICT
+    if (pRegEntry->fFlags & IOMMMIO_FLAGS_DBGSTOP_ON_COMPLICATED_READ)
+    {
+# ifdef IN_RING3
+        rc = DBGFR3EventSrc(pVM, DBGFEVENT_DEV_STOP, RT_SRC_POS,
+                            "Complicated read %#x byte at %RGp to %s\n", cbValue, GCPhys, R3STRING(pRegEntry->pszDesc));
+        if (rc == VERR_DBGF_NOT_ATTACHED)
+            rc = VINF_SUCCESS;
+# else
+        return VINF_IOM_R3_MMIO_READ;
+# endif
+    }
+#endif
+
+    STAM_COUNTER_INC(&pStats->ComplicatedReads);
+
+    /*
+     * Split and conquer.
+     */
+    for (;;)
+    {
+        /*
+         * Do DWORD read from the device.
+         */
+        uint32_t u32Value;
+        VBOXSTRICTRC rcStrict2 = pRegEntry->pfnReadCallback(pRegEntry->pDevIns, pRegEntry->pvUser,
+                                                            !(pRegEntry->fFlags & IOMMMIO_FLAGS_ABS)
+                                                            ? offRegion & ~(RTGCPHYS)3 : GCPhys & ~(RTGCPHYS)3,
+                                                            &u32Value, sizeof(u32Value));
+        switch (VBOXSTRICTRC_VAL(rcStrict2))
+        {
+            case VINF_SUCCESS:
+                break;
+            case VINF_IOM_MMIO_UNUSED_FF:
+                STAM_COUNTER_INC(&pStats->FFor00Reads);
+                u32Value = UINT32_C(0xffffffff);
+                break;
+            case VINF_IOM_MMIO_UNUSED_00:
+                STAM_COUNTER_INC(&pStats->FFor00Reads);
+                u32Value = 0;
+                break;
+            case VINF_IOM_R3_MMIO_READ:
+            case VINF_IOM_R3_MMIO_READ_WRITE:
+            case VINF_IOM_R3_MMIO_WRITE:
+                /** @todo What if we've split a transfer and already read
+                 * something?  Since reads can have sideeffects we could be
+                 * kind of screwed here... */
+                LogFlow(("iomMMIODoComplicatedRead: GCPhys=%RGp GCPhysStart=%RGp cbValue=%u rcStrict2=%Rrc\n",
+                         GCPhys, GCPhysStart, cbValue, VBOXSTRICTRC_VAL(rcStrict2)));
+                return rcStrict2;
+            default:
+                if (RT_FAILURE(rcStrict2))
+                {
+                    Log(("iomMMIODoComplicatedRead: GCPhys=%RGp GCPhysStart=%RGp cbValue=%u rcStrict2=%Rrc\n",
+                         GCPhys, GCPhysStart, cbValue, VBOXSTRICTRC_VAL(rcStrict2)));
+                    return rcStrict2;
+                }
+                AssertMsgReturn(rcStrict2 >= VINF_EM_FIRST && rcStrict2 <= VINF_EM_LAST, ("%Rrc\n", VBOXSTRICTRC_VAL(rcStrict2)),
+                                VERR_IPE_UNEXPECTED_INFO_STATUS);
+                if (rc == VINF_SUCCESS || rcStrict2 < rc)
+                    rc = rcStrict2;
+                break;
+        }
+        u32Value >>= (GCPhys & 3) * 8;
+
+        /*
+         * Write what we've read.
+         */
+        unsigned cbThisPart = 4 - (GCPhys & 3);
+        if (cbThisPart > cbValue)
+            cbThisPart = cbValue;
+
+        switch (cbThisPart)
+        {
+            case 1:
+                *(uint8_t *)pvValue = (uint8_t)u32Value;
+                break;
+            case 2:
+                *(uint16_t *)pvValue = (uint16_t)u32Value;
+                break;
+            case 3:
+                ((uint8_t *)pvValue)[0] = RT_BYTE1(u32Value);
+                ((uint8_t *)pvValue)[1] = RT_BYTE2(u32Value);
+                ((uint8_t *)pvValue)[2] = RT_BYTE3(u32Value);
+                break;
+            case 4:
+                *(uint32_t *)pvValue = u32Value;
+                break;
+        }
+
+        /*
+         * Advance.
+         */
+        cbValue   -= cbThisPart;
+        if (!cbValue)
+            break;
+        GCPhys    += cbThisPart;
+        offRegion += cbThisPart;
+        pvValue    = (uint8_t *)pvValue + cbThisPart;
+    }
+
+    return rc;
+}
+
+
+/**
+ * Implements VINF_IOM_MMIO_UNUSED_FF.
+ *
+ * @returns VINF_SUCCESS.
+ * @param   pvValue     Where to store the zeros.
+ * @param   cbValue     How many bytes to read.
+ * @param   pStats      Pointer to the statistics (never NULL).
+ */
+static int iomMMIODoReadFFs(void *pvValue, size_t cbValue IOM_MMIO_STATS_COMMA_DECL)
+{
+    switch (cbValue)
+    {
+        case 1: *(uint8_t  *)pvValue = UINT8_C(0xff); break;
+        case 2: *(uint16_t *)pvValue = UINT16_C(0xffff); break;
+        case 4: *(uint32_t *)pvValue = UINT32_C(0xffffffff); break;
+        case 8: *(uint64_t *)pvValue = UINT64_C(0xffffffffffffffff); break;
+        default:
+        {
+            uint8_t *pb = (uint8_t *)pvValue;
+            while (cbValue--)
+                *pb++ = UINT8_C(0xff);
+            break;
+        }
+    }
+    STAM_COUNTER_INC(&pStats->FFor00Reads);
+    return VINF_SUCCESS;
+}
+
+
+/**
+ * Implements VINF_IOM_MMIO_UNUSED_00.
+ *
+ * @returns VINF_SUCCESS.
+ * @param   pvValue     Where to store the zeros.
+ * @param   cbValue     How many bytes to read.
+ * @param   pStats      Pointer to the statistics (never NULL).
+ */
+static int iomMMIODoRead00s(void *pvValue, size_t cbValue IOM_MMIO_STATS_COMMA_DECL)
+{
+    switch (cbValue)
+    {
+        case 1: *(uint8_t  *)pvValue = UINT8_C(0x00); break;
+        case 2: *(uint16_t *)pvValue = UINT16_C(0x0000); break;
+        case 4: *(uint32_t *)pvValue = UINT32_C(0x00000000); break;
+        case 8: *(uint64_t *)pvValue = UINT64_C(0x0000000000000000); break;
+        default:
+        {
+            uint8_t *pb = (uint8_t *)pvValue;
+            while (cbValue--)
+                *pb++ = UINT8_C(0x00);
+            break;
+        }
+    }
+    STAM_COUNTER_INC(&pStats->FFor00Reads);
+    return VINF_SUCCESS;
+}
+
+
+/**
+ * Wrapper which does the read.
+ */
+DECLINLINE(VBOXSTRICTRC) iomMmioDoRead(PVMCC pVM, CTX_SUFF(PIOMMMIOENTRY) pRegEntry, RTGCPHYS GCPhys, RTGCPHYS offRegion,
+                                       void *pvValue, uint32_t cbValue IOM_MMIO_STATS_COMMA_DECL)
+{
+    VBOXSTRICTRC rcStrict;
+    if (RT_LIKELY(pRegEntry->pfnReadCallback))
+    {
+        if (   (   cbValue == 4
+                && !(GCPhys & 3))
+            || (pRegEntry->fFlags & IOMMMIO_FLAGS_READ_MODE) == IOMMMIO_FLAGS_READ_PASSTHRU
+            || (    cbValue == 8
+                && !(GCPhys & 7)
+                && (pRegEntry->fFlags & IOMMMIO_FLAGS_READ_MODE) == IOMMMIO_FLAGS_READ_DWORD_QWORD ) )
+            rcStrict = pRegEntry->pfnReadCallback(pRegEntry->pDevIns, pRegEntry->pvUser,
+                                                  !(pRegEntry->fFlags & IOMMMIO_FLAGS_ABS) ? offRegion : GCPhys, pvValue, cbValue);
+        else
+            rcStrict = iomMMIODoComplicatedRead(pVM, pRegEntry, GCPhys, offRegion, pvValue, cbValue IOM_MMIO_STATS_COMMA_ARG);
+    }
+    else
+        rcStrict = VINF_IOM_MMIO_UNUSED_FF;
+    if (rcStrict != VINF_SUCCESS)
+    {
+        switch (VBOXSTRICTRC_VAL(rcStrict))
+        {
+            case VINF_IOM_MMIO_UNUSED_FF: rcStrict = iomMMIODoReadFFs(pvValue, cbValue IOM_MMIO_STATS_COMMA_ARG); break;
+            case VINF_IOM_MMIO_UNUSED_00: rcStrict = iomMMIODoRead00s(pvValue, cbValue IOM_MMIO_STATS_COMMA_ARG); break;
+        }
+    }
+    return rcStrict;
+}
+
+#ifndef IN_RING3
+
+/**
+ * Checks if we can handle an MMIO \#PF in R0/RC.
+ */
+DECLINLINE(bool) iomMmioCanHandlePfInRZ(PVMCC pVM, uint32_t uErrorCode, CTX_SUFF(PIOMMMIOENTRY) pRegEntry)
+{
+    if (pRegEntry->cbRegion > 0)
+    {
+        if (   pRegEntry->pfnWriteCallback
+            && pRegEntry->pfnReadCallback)
+            return true;
+
+        PIOMMMIOENTRYR3 const pRegEntryR3 = &pVM->iomr0.s.paMmioRing3Regs[pRegEntry->idxSelf];
+        if (  uErrorCode == UINT32_MAX
+            ? pRegEntryR3->pfnWriteCallback || pRegEntryR3->pfnReadCallback
+            : uErrorCode & X86_TRAP_PF_RW
+              ? !pRegEntry->pfnWriteCallback && pRegEntryR3->pfnWriteCallback
+              : !pRegEntry->pfnReadCallback  && pRegEntryR3->pfnReadCallback)
+            return false;
+
+        return true;
+    }
+    return false;
+}
+
+
+/**
+ * Common worker for the \#PF handler and IOMMMIOPhysHandler (APIC+VT-x).
+ *
+ * @returns VBox status code (appropriate for GC return).
+ * @param   pVM         The cross context VM structure.
+ * @param   pVCpu       The cross context virtual CPU structure of the calling EMT.
+ * @param   uErrorCode  CPU Error code.  This is UINT32_MAX when we don't have
+ *                      any error code (the EPT misconfig hack).
+ * @param   GCPhysFault The GC physical address corresponding to pvFault.
+ * @param   pRegEntry   The MMIO entry for the current context.
+ */
+DECLINLINE(VBOXSTRICTRC) iomMmioCommonPfHandlerNew(PVMCC pVM, PVMCPUCC pVCpu, uint32_t uErrorCode,
+                                                   RTGCPHYS GCPhysFault, CTX_SUFF(PIOMMMIOENTRY) pRegEntry)
+{
+    Log(("iomMmioCommonPfHandler: GCPhysFault=%RGp uErr=%#x rip=%RGv\n", GCPhysFault, uErrorCode, CPUMGetGuestRIP(pVCpu) ));
+    RT_NOREF(GCPhysFault, uErrorCode);
+
+    VBOXSTRICTRC rcStrict;
+
+#ifndef IN_RING3
+    /*
+     * Should we defer the request right away?  This isn't usually the case, so
+     * do the simple test first and the try deal with uErrorCode being N/A.
+     */
+    PPDMDEVINS const pDevIns = pRegEntry->pDevIns;
+    if (RT_LIKELY(   pDevIns
+                  && iomMmioCanHandlePfInRZ(pVM, uErrorCode, pRegEntry)))
+    {
+        /*
+         * Enter the device critsect prior to engaging IOM in case of lock contention.
+         * Note! Perhaps not a good move?
+         */
+        rcStrict = PDMCritSectEnter(pVM, pDevIns->CTX_SUFF(pCritSectRo), VINF_IOM_R3_MMIO_READ_WRITE);
+        if (rcStrict == VINF_SUCCESS)
+        {
+#endif /* !IN_RING3 */
+
+            /*
+             * Let IEM call us back via iomMmioHandler.
+             */
+            rcStrict = IEMExecOne(pVCpu);
+
+#ifndef IN_RING3
+            PDMCritSectLeave(pVM, pDevIns->CTX_SUFF(pCritSectRo));
+#endif
+            if (RT_SUCCESS(rcStrict))
+            { /* likely */ }
+            else if (   rcStrict == VERR_IEM_ASPECT_NOT_IMPLEMENTED
+                     || rcStrict == VERR_IEM_INSTR_NOT_IMPLEMENTED)
+            {
+                Log(("IOM: Hit unsupported IEM feature!\n"));
+                rcStrict = VINF_EM_RAW_EMULATE_INSTR;
+            }
+#ifndef IN_RING3
+            return rcStrict;
+        }
+        STAM_COUNTER_INC(&pVM->iom.s.StatMmioDevLockContentionR0);
+    }
+    else
+        rcStrict = VINF_IOM_R3_MMIO_READ_WRITE;
+
+# ifdef VBOX_WITH_STATISTICS
+    if (rcStrict == VINF_IOM_R3_MMIO_READ_WRITE)
+    {
+        PIOMMMIOSTATSENTRY const pStats = iomMmioGetStats(pVM, pRegEntry);
+        if (uErrorCode & X86_TRAP_PF_RW)
+        {
+            STAM_COUNTER_INC(&pStats->WriteRZToR3);
+            STAM_COUNTER_INC(&pVM->iom.s.StatMmioWritesR0ToR3);
+        }
+        else
+        {
+            STAM_COUNTER_INC(&pStats->ReadRZToR3);
+            STAM_COUNTER_INC(&pVM->iom.s.StatMmioReadsR0ToR3);
+        }
+    }
+# endif
+#else  /* IN_RING3 */
+    RT_NOREF(pVM, pRegEntry);
+#endif /* IN_RING3 */
+    return rcStrict;
+}
+
+
+/**
+ * @callback_method_impl{FNPGMRZPHYSPFHANDLER,
+ *      \#PF access handler callback for MMIO pages.}
+ *
+ * @remarks The @a uUser argument is the MMIO handle.
+ */
+DECLCALLBACK(VBOXSTRICTRC) iomMmioPfHandlerNew(PVMCC pVM, PVMCPUCC pVCpu, RTGCUINT uErrorCode, PCPUMCTX pCtx,
+                                               RTGCPTR pvFault, RTGCPHYS GCPhysFault, uint64_t uUser)
+{
+    STAM_PROFILE_START(&pVM->iom.s.StatMmioPfHandler, Prf);
+    LogFlow(("iomMmioPfHandlerNew: GCPhys=%RGp uErr=%#x pvFault=%RGv rip=%RGv\n",
+             GCPhysFault, (uint32_t)uErrorCode, pvFault, (RTGCPTR)pCtx->rip));
+    RT_NOREF(pvFault, pCtx);
+
+    /* Translate the MMIO handle to a registration entry for the current context. */
+    AssertReturn(uUser < RT_MIN(pVM->iom.s.cMmioRegs, pVM->iom.s.cMmioAlloc), VERR_IOM_INVALID_MMIO_HANDLE);
+# ifdef IN_RING0
+    AssertReturn(uUser < pVM->iomr0.s.cMmioAlloc, VERR_IOM_INVALID_MMIO_HANDLE);
+    CTX_SUFF(PIOMMMIOENTRY) pRegEntry = &pVM->iomr0.s.paMmioRegs[uUser];
+# else
+    CTX_SUFF(PIOMMMIOENTRY) pRegEntry = &pVM->iom.s.paMmioRegs[uUser];
+# endif
+
+    VBOXSTRICTRC rcStrict = iomMmioCommonPfHandlerNew(pVM, pVCpu, (uint32_t)uErrorCode, GCPhysFault, pRegEntry);
+
+    STAM_PROFILE_STOP(&pVM->iom.s.StatMmioPfHandler, Prf);
+    return rcStrict;
+}
+
+#endif /* !IN_RING3 */
+
+#ifdef IN_RING0
+/**
+ * Physical access handler for MMIO ranges.
+ *
+ * This is actually only used by VT-x for APIC page accesses.
+ *
+ * @returns VBox status code (appropriate for GC return).
+ * @param   pVM         The cross context VM structure.
+ * @param   pVCpu       The cross context virtual CPU structure of the calling EMT.
+ * @param   uErrorCode  CPU Error code.
+ * @param   GCPhysFault The GC physical address.
+ */
+VMM_INT_DECL(VBOXSTRICTRC) IOMR0MmioPhysHandler(PVMCC pVM, PVMCPUCC pVCpu, uint32_t uErrorCode, RTGCPHYS GCPhysFault)
+{
+    STAM_PROFILE_START(&pVM->iom.s.StatMmioPhysHandler, Prf);
+
+    /*
+     * We don't have a range here, so look it up before calling the common function.
+     */
+    VBOXSTRICTRC rcStrict = IOM_LOCK_SHARED(pVM);
+    if (RT_SUCCESS(rcStrict))
+    {
+        RTGCPHYS offRegion;
+        CTX_SUFF(PIOMMMIOENTRY) pRegEntry = iomMmioGetEntry(pVM, GCPhysFault, &offRegion, &pVCpu->iom.s.idxMmioLastPhysHandler);
+        IOM_UNLOCK_SHARED(pVM);
+        if (RT_LIKELY(pRegEntry))
+            rcStrict = iomMmioCommonPfHandlerNew(pVM, pVCpu, (uint32_t)uErrorCode, GCPhysFault, pRegEntry);
+        else
+            rcStrict = VERR_IOM_MMIO_RANGE_NOT_FOUND;
+    }
+    else if (rcStrict == VERR_SEM_BUSY)
+        rcStrict = VINF_IOM_R3_MMIO_READ_WRITE;
+
+    STAM_PROFILE_STOP(&pVM->iom.s.StatMmioPhysHandler, Prf);
+    return rcStrict;
+}
+#endif /* IN_RING0 */
+
+
+/**
+ * @callback_method_impl{FNPGMPHYSHANDLER, MMIO page accesses}
+ *
+ * @remarks The @a uUser argument is the MMIO handle.
+ */
+DECLCALLBACK(VBOXSTRICTRC) iomMmioHandlerNew(PVMCC pVM, PVMCPUCC pVCpu, RTGCPHYS GCPhysFault, void *pvPhys, void *pvBuf,
+                                             size_t cbBuf, PGMACCESSTYPE enmAccessType, PGMACCESSORIGIN enmOrigin, uint64_t uUser)
+{
+    STAM_PROFILE_START(UnusedMacroArg, Prf);
+    STAM_COUNTER_INC(&pVM->iom.s.CTX_SUFF(StatMmioHandler));
+    Log4(("iomMmioHandlerNew: GCPhysFault=%RGp cbBuf=%#x enmAccessType=%d enmOrigin=%d uUser=%p\n", GCPhysFault, cbBuf, enmAccessType, enmOrigin, uUser));
+
+    Assert(enmAccessType == PGMACCESSTYPE_READ || enmAccessType == PGMACCESSTYPE_WRITE);
+    AssertMsg(cbBuf >= 1, ("%zu\n", cbBuf));
+    NOREF(pvPhys); NOREF(enmOrigin);
+
+#ifdef IN_RING3
+    int const rcToRing3 = VERR_IOM_MMIO_IPE_3;
+#else
+    int const rcToRing3 = enmAccessType == PGMACCESSTYPE_READ ? VINF_IOM_R3_MMIO_READ : VINF_IOM_R3_MMIO_WRITE;
+#endif
+
+    /*
+     * Translate uUser to an MMIO registration table entry.  We can do this
+     * without any locking as the data is static after VM creation.
+     */
+    AssertReturn(uUser < RT_MIN(pVM->iom.s.cMmioRegs, pVM->iom.s.cMmioAlloc), VERR_IOM_INVALID_MMIO_HANDLE);
+#ifdef IN_RING0
+    AssertReturn(uUser < pVM->iomr0.s.cMmioAlloc, VERR_IOM_INVALID_MMIO_HANDLE);
+    CTX_SUFF(PIOMMMIOENTRY) const pRegEntry    = &pVM->iomr0.s.paMmioRegs[uUser];
+    PIOMMMIOENTRYR3 const         pRegEntryR3  = &pVM->iomr0.s.paMmioRing3Regs[uUser];
+#else
+    CTX_SUFF(PIOMMMIOENTRY) const pRegEntry    = &pVM->iom.s.paMmioRegs[uUser];
+#endif
+#ifdef VBOX_WITH_STATISTICS
+    PIOMMMIOSTATSENTRY const      pStats       = iomMmioGetStats(pVM, pRegEntry);  /* (Works even without ring-0 device setup.) */
+#endif
+    PPDMDEVINS const              pDevIns      = pRegEntry->pDevIns;
+
+#ifdef VBOX_STRICT
+    /*
+     * Assert the right entry in strict builds.  This may yield a false positive
+     * for SMP VMs if we're unlucky and the guest isn't well behaved.
+     */
+# ifdef IN_RING0
+    Assert(pRegEntry && (GCPhysFault - pRegEntryR3->GCPhysMapping < pRegEntryR3->cbRegion || !pRegEntryR3->fMapped));
+# else
+    Assert(pRegEntry && (GCPhysFault - pRegEntry->GCPhysMapping   < pRegEntry->cbRegion   || !pRegEntry->fMapped));
+# endif
+#endif
+
+#ifndef IN_RING3
+    /*
+     * If someone is doing FXSAVE, FXRSTOR, XSAVE, XRSTOR or other stuff dealing with
+     * large amounts of data, just go to ring-3 where we don't need to deal with partial
+     * successes.  No chance any of these will be problematic read-modify-write stuff.
+     *
+     * Also drop back if the ring-0 registration entry isn't actually used.
+     */
+    if (   RT_LIKELY(cbBuf <= sizeof(pVCpu->iom.s.PendingMmioWrite.abValue))
+        && pRegEntry->cbRegion != 0
+        && (  enmAccessType == PGMACCESSTYPE_READ
+            ? pRegEntry->pfnReadCallback  != NULL || pVM->iomr0.s.paMmioRing3Regs[uUser].pfnReadCallback == NULL
+            : pRegEntry->pfnWriteCallback != NULL || pVM->iomr0.s.paMmioRing3Regs[uUser].pfnWriteCallback == NULL)
+        && pDevIns )
+    { /* likely */ }
+    else
+    {
+        Log4(("iomMmioHandlerNew: to ring-3: to-big=%RTbool zero-size=%RTbool no-callback=%RTbool pDevIns=%p hRegion=%#RX64\n",
+              !(cbBuf <= sizeof(pVCpu->iom.s.PendingMmioWrite.abValue)), !(pRegEntry->cbRegion != 0),
+              !(  enmAccessType == PGMACCESSTYPE_READ
+                ? pRegEntry->pfnReadCallback  != NULL || pVM->iomr0.s.paMmioRing3Regs[uUser].pfnReadCallback == NULL
+                : pRegEntry->pfnWriteCallback != NULL || pVM->iomr0.s.paMmioRing3Regs[uUser].pfnWriteCallback == NULL),
+              pDevIns, uUser));
+        STAM_COUNTER_INC(enmAccessType == PGMACCESSTYPE_READ ? &pStats->ReadRZToR3 : &pStats->WriteRZToR3);
+        STAM_COUNTER_INC(enmAccessType == PGMACCESSTYPE_READ ? &pVM->iom.s.StatMmioReadsR0ToR3 : &pVM->iom.s.StatMmioWritesR0ToR3);
+        return rcToRing3;
+    }
+#endif /* !IN_RING3 */
+
+    /*
+     * If we've got an offset that's outside the region, defer to ring-3 if we
+     * can, or pretend there is nothing there.  This shouldn't happen, but can
+     * if we're unlucky with an SMP VM and the guest isn't behaving very well.
+     */
+#ifdef IN_RING0
+    RTGCPHYS const GCPhysMapping = pRegEntryR3->GCPhysMapping;
+#else
+    RTGCPHYS const GCPhysMapping = pRegEntry->GCPhysMapping;
+#endif
+    RTGCPHYS const offRegion     = GCPhysFault - GCPhysMapping;
+    if (RT_LIKELY(offRegion < pRegEntry->cbRegion && GCPhysMapping != NIL_RTGCPHYS))
+    { /* likely */ }
+    else
+    {
+        STAM_REL_COUNTER_INC(&pVM->iom.s.StatMmioStaleMappings);
+        LogRelMax(64, ("iomMmioHandlerNew: Stale access at %#RGp to range #%#x currently residing at %RGp LB %RGp\n",
+                       GCPhysFault, pRegEntry->idxSelf, GCPhysMapping, pRegEntry->cbRegion));
+#ifdef IN_RING3
+        if (enmAccessType == PGMACCESSTYPE_READ)
+            iomMMIODoReadFFs(pvBuf, cbBuf IOM_MMIO_STATS_COMMA_ARG);
+        return VINF_SUCCESS;
+#else
+        STAM_COUNTER_INC(enmAccessType == PGMACCESSTYPE_READ ? &pStats->ReadRZToR3 : &pStats->WriteRZToR3);
+        STAM_COUNTER_INC(enmAccessType == PGMACCESSTYPE_READ ? &pVM->iom.s.StatMmioReadsR0ToR3 : &pVM->iom.s.StatMmioWritesR0ToR3);
+        return rcToRing3;
+#endif
+    }
+
+    /*
+     * Guard against device configurations causing recursive MMIO accesses
+     * (see @bugref{10315}).
+     */
+    uint8_t const idxDepth = pVCpu->iom.s.cMmioRecursionDepth;
+    if (RT_LIKELY(idxDepth < RT_ELEMENTS(pVCpu->iom.s.apMmioRecursionStack)))
+    {
+        pVCpu->iom.s.cMmioRecursionDepth  = idxDepth + 1;
+        /** @todo Add iomr0 with a apMmioRecursionStack for ring-0. */
+#ifdef IN_RING3
+        pVCpu->iom.s.apMmioRecursionStack[idxDepth] = pDevIns;
+#endif
+    }
+    else
+    {
+        STAM_REL_COUNTER_INC(&pVM->iom.s.StatMmioTooDeepRecursion);
+#ifdef IN_RING3
+        AssertCompile(RT_ELEMENTS(pVCpu->iom.s.apMmioRecursionStack) == 2);
+        LogRelMax(64, ("iomMmioHandlerNew: Too deep recursion %RGp LB %#zx: %p (%s); %p (%s); %p (%s)\n",
+                       GCPhysFault, cbBuf, pDevIns, pDevIns->pReg->szName,
+                       pVCpu->iom.s.apMmioRecursionStack[1], pVCpu->iom.s.apMmioRecursionStack[1]->pReg->szName,
+                       pVCpu->iom.s.apMmioRecursionStack[0], pVCpu->iom.s.apMmioRecursionStack[0]->pReg->szName));
+#else
+        LogRelMax(64, ("iomMmioHandlerNew: Too deep recursion %RGp LB %#zx!: %p (%s)\n",
+                       GCPhysFault, cbBuf, pDevIns, pDevIns->pReg->szName));
+#endif
+        return VINF_PGM_HANDLER_DO_DEFAULT;
+    }
+
+
+    /*
+     * Perform locking and the access.
+     *
+     * Writes requiring a return to ring-3 are buffered by IOM so IEM can
+     * commit the instruction.
+     *
+     * Note! We may end up locking the device even when the relevant callback is
+     *       NULL.  This is supposed to be an unlikely case, so not optimized yet.
+     *
+     * Note! All returns goes thru the one return statement at the end of the
+     *       function in order to correctly maintaint the recursion counter.
+     */
+    VBOXSTRICTRC rcStrict = PDMCritSectEnter(pVM, pDevIns->CTX_SUFF(pCritSectRo), rcToRing3);
+    if (rcStrict == VINF_SUCCESS)
+    {
+        if (enmAccessType == PGMACCESSTYPE_READ)
+        {
+            /*
+             * Read.
+             */
+            rcStrict = iomMmioDoRead(pVM, pRegEntry, GCPhysFault, offRegion, pvBuf, (uint32_t)cbBuf IOM_MMIO_STATS_COMMA_ARG);
+
+            PDMCritSectLeave(pVM, pDevIns->CTX_SUFF(pCritSectRo));
+#ifndef IN_RING3
+            if (rcStrict == VINF_IOM_R3_MMIO_READ)
+            {
+                STAM_COUNTER_INC(&pStats->ReadRZToR3);
+                STAM_COUNTER_INC(&pVM->iom.s.StatMmioReadsR0ToR3);
+            }
+            else
+#endif
+                STAM_COUNTER_INC(&pStats->Reads);
+            STAM_PROFILE_STOP(&pStats->CTX_SUFF_Z(ProfRead), Prf);
+        }
+        else
+        {
+            /*
+             * Write.
+             */
+            rcStrict = iomMmioDoWrite(pVM, pVCpu, pRegEntry, GCPhysFault, offRegion, pvBuf, (uint32_t)cbBuf IOM_MMIO_STATS_COMMA_ARG);
+            PDMCritSectLeave(pVM, pDevIns->CTX_SUFF(pCritSectRo));
+#ifndef IN_RING3
+            if (rcStrict == VINF_IOM_R3_MMIO_WRITE)
+                rcStrict = iomMmioRing3WritePending(pVCpu, GCPhysFault, pvBuf, cbBuf, pRegEntry->idxSelf);
+            if (rcStrict == VINF_IOM_R3_MMIO_WRITE)
+            {
+                STAM_COUNTER_INC(&pStats->WriteRZToR3);
+                STAM_COUNTER_INC(&pVM->iom.s.StatMmioWritesR0ToR3);
+            }
+            else if (rcStrict == VINF_IOM_R3_MMIO_COMMIT_WRITE)
+            {
+                STAM_COUNTER_INC(&pStats->CommitRZToR3);
+                STAM_COUNTER_INC(&pVM->iom.s.StatMmioCommitsR0ToR3);
+            }
+            else
+#endif
+                STAM_COUNTER_INC(&pStats->Writes);
+            STAM_PROFILE_STOP(&pStats->CTX_SUFF_Z(ProfWrite), Prf);
+        }
+
+        /*
+         * Check the return code.
+         */
+#ifdef IN_RING3
+        AssertMsg(rcStrict == VINF_SUCCESS, ("%Rrc -  Access type %d - %RGp - %s\n",
+                                             VBOXSTRICTRC_VAL(rcStrict), enmAccessType, GCPhysFault, pRegEntry->pszDesc));
+#else
+        AssertMsg(   rcStrict == VINF_SUCCESS
+                  || rcStrict == rcToRing3
+                  || (rcStrict == VINF_IOM_R3_MMIO_COMMIT_WRITE && enmAccessType == PGMACCESSTYPE_WRITE)
+                  || rcStrict == VINF_EM_DBG_STOP
+                  || rcStrict == VINF_EM_DBG_EVENT
+                  || rcStrict == VINF_EM_DBG_BREAKPOINT
+                  || rcStrict == VINF_EM_OFF
+                  || rcStrict == VINF_EM_SUSPEND
+                  || rcStrict == VINF_EM_RESET
+                  //|| rcStrict == VINF_EM_HALT       /* ?? */
+                  //|| rcStrict == VINF_EM_NO_MEMORY  /* ?? */
+                  , ("%Rrc - Access type %d - %RGp - %s #%u\n",
+                     VBOXSTRICTRC_VAL(rcStrict), enmAccessType, GCPhysFault, pDevIns->pReg->szName, pDevIns->iInstance));
+#endif
+    }
+    /*
+     * Deal with enter-critsect failures.
+     */
+#ifndef IN_RING3
+    else if (rcStrict == VINF_IOM_R3_MMIO_WRITE)
+    {
+        Assert(enmAccessType == PGMACCESSTYPE_WRITE);
+        rcStrict = iomMmioRing3WritePending(pVCpu, GCPhysFault, pvBuf, cbBuf, pRegEntry->idxSelf);
+        if (rcStrict == VINF_IOM_R3_MMIO_COMMIT_WRITE)
+        {
+            STAM_COUNTER_INC(&pStats->CommitRZToR3);
+            STAM_COUNTER_INC(&pVM->iom.s.StatMmioCommitsR0ToR3);
+        }
+        else
+        {
+            STAM_COUNTER_INC(&pStats->WriteRZToR3);
+            STAM_COUNTER_INC(&pVM->iom.s.StatMmioWritesR0ToR3);
+        }
+        STAM_COUNTER_INC(&pVM->iom.s.StatMmioDevLockContentionR0);
+    }
+    else if (rcStrict == VINF_IOM_R3_MMIO_READ)
+    {
+        Assert(enmAccessType == PGMACCESSTYPE_READ);
+        STAM_COUNTER_INC(&pStats->ReadRZToR3);
+        STAM_COUNTER_INC(&pVM->iom.s.StatMmioDevLockContentionR0);
+    }
+#endif
+    else
+        AssertMsg(RT_FAILURE_NP(rcStrict), ("%Rrc\n", VBOXSTRICTRC_VAL(rcStrict)));
+
+    pVCpu->iom.s.cMmioRecursionDepth = idxDepth;
+    return rcStrict;
+}
+
+
+/**
+ * Mapping an MMIO2 page in place of an MMIO page for direct access.
+ *
+ * This is a special optimization used by the VGA device.  Call
+ * IOMMmioResetRegion() to undo the mapping.
+ *
+ * @returns VBox status code.  This API may return VINF_SUCCESS even if no
+ *          remapping is made.
+ * @retval  VERR_SEM_BUSY in ring-0 if we cannot get the IOM lock.
+ *
+ * @param   pVM             The cross context VM structure.
+ * @param   pDevIns         The device instance @a hRegion and @a hMmio2 are
+ *                          associated with.
+ * @param   hRegion         The handle to the MMIO region.
+ * @param   offRegion       The offset into @a hRegion of the page to be
+ *                          remapped.
+ * @param   hMmio2          The MMIO2 handle.
+ * @param   offMmio2        Offset into @a hMmio2 of the page to be use for the
+ *                          mapping.
+ * @param   fPageFlags      Page flags to set. Must be (X86_PTE_RW | X86_PTE_P)
+ *                          for the time being.
+ */
+VMMDECL(int) IOMMmioMapMmio2Page(PVMCC pVM, PPDMDEVINS pDevIns, IOMMMIOHANDLE hRegion, RTGCPHYS offRegion,
+                                 uint64_t hMmio2, RTGCPHYS offMmio2, uint64_t fPageFlags)
+{
+    /* Currently only called from the VGA device during MMIO. */
+    Log(("IOMMmioMapMmio2Page %#RX64/%RGp -> %#RX64/%RGp flags=%RX64\n", hRegion, offRegion, hMmio2, offMmio2, fPageFlags));
+    AssertReturn(fPageFlags == (X86_PTE_RW | X86_PTE_P), VERR_INVALID_PARAMETER);
+    AssertReturn(pDevIns, VERR_INVALID_POINTER);
+
+/** @todo Why is this restricted to protected mode???  Try it in all modes! */
+    PVMCPUCC pVCpu = VMMGetCpu(pVM);
+
+    /* This currently only works in real mode, protected mode without paging or with nested paging. */
+    /** @todo NEM: MMIO page aliasing. */
+    if (    !HMIsEnabled(pVM)       /* useless without VT-x/AMD-V */
+        ||  (   CPUMIsGuestInPagedProtectedMode(pVCpu)
+             && !HMIsNestedPagingActive(pVM)))
+        return VINF_SUCCESS;    /* ignore */ /** @todo return some indicator if we fail here */
+
+    /*
+     * Translate the handle into an entry and check the region offset.
+     */
+    AssertReturn(hRegion < RT_MIN(pVM->iom.s.cMmioRegs, pVM->iom.s.cMmioAlloc), VERR_IOM_INVALID_MMIO_HANDLE);
+#ifdef IN_RING0
+    AssertReturn(hRegion < pVM->iomr0.s.cMmioAlloc, VERR_IOM_INVALID_MMIO_HANDLE);
+    PIOMMMIOENTRYR3 const pRegEntry = &pVM->iomr0.s.paMmioRing3Regs[hRegion];
+    AssertReturn(pRegEntry->cbRegion > 0, VERR_IOM_INVALID_MMIO_HANDLE);
+    AssertReturn(offRegion < pVM->iomr0.s.paMmioRegs[hRegion].cbRegion, VERR_OUT_OF_RANGE);
+    AssertReturn(   pVM->iomr0.s.paMmioRegs[hRegion].pDevIns == pDevIns
+                 || (   pVM->iomr0.s.paMmioRegs[hRegion].pDevIns == NULL
+                     && pRegEntry->pDevIns == pDevIns->pDevInsForR3), VERR_ACCESS_DENIED);
+#else
+    PIOMMMIOENTRYR3 const pRegEntry = &pVM->iom.s.paMmioRegs[hRegion];
+    AssertReturn(pRegEntry->cbRegion > 0, VERR_IOM_INVALID_MMIO_HANDLE);
+    AssertReturn(pRegEntry->pDevIns == pDevIns, VERR_ACCESS_DENIED);
+#endif
+    AssertReturn(offRegion < pRegEntry->cbRegion, VERR_OUT_OF_RANGE);
+    Assert((pRegEntry->cbRegion & GUEST_PAGE_OFFSET_MASK) == 0);
+
+    /*
+     * When getting and using the mapping address, we must sit on the IOM lock
+     * to prevent remapping.  Shared suffices as we change nothing.
+     */
+    int rc = IOM_LOCK_SHARED(pVM);
+    if (rc == VINF_SUCCESS)
+    {
+        RTGCPHYS const GCPhys = pRegEntry->fMapped ? pRegEntry->GCPhysMapping : NIL_RTGCPHYS;
+        if (GCPhys != NIL_RTGCPHYS)
+        {
+            Assert(!(GCPhys & GUEST_PAGE_OFFSET_MASK));
+
+            /*
+             * Do the aliasing; page align the addresses since PGM is picky.
+             */
+            rc = PGMHandlerPhysicalPageAliasMmio2(pVM, GCPhys, GCPhys + (offRegion & ~(RTGCPHYS)GUEST_PAGE_OFFSET_MASK),
+                                                  pDevIns, hMmio2, offMmio2);
+        }
+        else
+            AssertFailedStmt(rc = VERR_IOM_MMIO_REGION_NOT_MAPPED);
+
+        IOM_UNLOCK_SHARED(pVM);
+    }
+
+/** @todo either ditch this or replace it with something that works in the
+ *        nested case, since we really only care about nested paging! */
+#if 0
+    /*
+     * Modify the shadow page table. Since it's an MMIO page it won't be present and we
+     * can simply prefetch it.
+     *
+     * Note: This is a NOP in the EPT case; we'll just let it fault again to resync the page.
+     */
+# if 0 /* The assertion is wrong for the PGM_SYNC_CLEAR_PGM_POOL and VINF_PGM_HANDLER_ALREADY_ALIASED cases. */
+#  ifdef VBOX_STRICT
+    uint64_t fFlags;
+    RTHCPHYS HCPhys;
+    rc = PGMShwGetPage(pVCpu, (RTGCPTR)GCPhys, &fFlags, &HCPhys);
+    Assert(rc == VERR_PAGE_NOT_PRESENT || rc == VERR_PAGE_TABLE_NOT_PRESENT);
+#  endif
+# endif
+    rc = PGMPrefetchPage(pVCpu, (RTGCPTR)GCPhys);
+    Assert(rc == VINF_SUCCESS || rc == VERR_PAGE_NOT_PRESENT || rc == VERR_PAGE_TABLE_NOT_PRESENT);
+#endif
+    return rc;
+}
+
+
+#ifdef IN_RING0 /* VT-x ring-0 only, move to IOMR0Mmio.cpp later.  */
+/**
+ * Mapping a HC page in place of an MMIO page for direct access.
+ *
+ * This is a special optimization used by the APIC in the VT-x case.  This VT-x
+ * code uses PGMHandlerPhysicalReset rather than IOMMmioResetRegion() to undo
+ * the effects here.
+ *
+ * @todo Make VT-x usage more consistent.
+ *
+ * @returns VBox status code.
+ *
+ * @param   pVM             The cross context VM structure.
+ * @param   pVCpu           The cross context virtual CPU structure.
+ * @param   GCPhys          The address of the MMIO page to be changed.
+ * @param   HCPhys          The address of the host physical page.
+ * @param   fPageFlags      Page flags to set. Must be (X86_PTE_RW | X86_PTE_P)
+ *                          for the time being.
+ */
+VMMR0_INT_DECL(int) IOMR0MmioMapMmioHCPage(PVMCC pVM, PVMCPUCC pVCpu, RTGCPHYS GCPhys, RTHCPHYS HCPhys, uint64_t fPageFlags)
+{
+    /* Currently only called from VT-x code during a page fault. */
+    Log(("IOMR0MmioMapMmioHCPage %RGp -> %RGp flags=%RX64\n", GCPhys, HCPhys, fPageFlags));
+
+    AssertReturn(fPageFlags == (X86_PTE_RW | X86_PTE_P), VERR_INVALID_PARAMETER);
+    /** @todo NEM: MMIO page aliasing?? */
+    Assert(HMIsEnabled(pVM));
+
+# ifdef VBOX_STRICT
+    /*
+     * Check input address (it's HM calling, not the device, so no region handle).
+     */
+    int rcSem = IOM_LOCK_SHARED(pVM);
+    if (rcSem == VINF_SUCCESS)
+    {
+        RTGCPHYS offIgn;
+        uint16_t idxIgn = UINT16_MAX;
+        PIOMMMIOENTRYR0 pRegEntry = iomMmioGetEntry(pVM, GCPhys, &offIgn, &idxIgn);
+        IOM_UNLOCK_SHARED(pVM);
+        Assert(pRegEntry);
+        Assert(pRegEntry && !(pRegEntry->cbRegion & GUEST_PAGE_OFFSET_MASK));
+    }
+# endif
+
+    /*
+     * Do the aliasing; page align the addresses since PGM is picky.
+     */
+    GCPhys &= ~(RTGCPHYS)GUEST_PAGE_OFFSET_MASK;
+    HCPhys &= ~(RTHCPHYS)GUEST_PAGE_OFFSET_MASK;
+
+    int rc = PGMHandlerPhysicalPageAliasHC(pVM, GCPhys, GCPhys, HCPhys);
+    AssertRCReturn(rc, rc);
+
+/** @todo either ditch this or replace it with something that works in the
+ *        nested case, since we really only care about nested paging! */
+
+    /*
+     * Modify the shadow page table. Since it's an MMIO page it won't be present and we
+     * can simply prefetch it.
+     *
+     * Note: This is a NOP in the EPT case; we'll just let it fault again to resync the page.
+     */
+    rc = PGMPrefetchPage(pVCpu, (RTGCPTR)GCPhys);
+    Assert(rc == VINF_SUCCESS || rc == VERR_PAGE_NOT_PRESENT || rc == VERR_PAGE_TABLE_NOT_PRESENT);
+    return VINF_SUCCESS;
+}
+#endif
+
+
+/**
+ * Reset a previously modified MMIO region; restore the access flags.
+ *
+ * This undoes the effects of IOMMmioMapMmio2Page() and is currently only
+ * intended for some ancient VGA hack.  However, it would be great to extend it
+ * beyond VT-x and/or nested-paging.
+ *
+ * @returns VBox status code.
+ *
+ * @param   pVM             The cross context VM structure.
+ * @param   pDevIns         The device instance @a hRegion is associated with.
+ * @param   hRegion         The handle to the MMIO region.
+ */
+VMMDECL(int) IOMMmioResetRegion(PVMCC pVM, PPDMDEVINS pDevIns, IOMMMIOHANDLE hRegion)
+{
+    Log(("IOMMMIOResetRegion %#RX64\n", hRegion));
+    AssertReturn(pDevIns, VERR_INVALID_POINTER);
+
+/** @todo Get rid of this this real/protected or nested paging restriction,
+ *        it probably shouldn't be here and would be nasty when the CPU
+ *        changes mode while we have the hack enabled... */
+    PVMCPUCC pVCpu = VMMGetCpu(pVM);
+
+    /* This currently only works in real mode, protected mode without paging or with nested paging. */
+    /** @todo NEM: MMIO page aliasing. */
+    if (   !HMIsEnabled(pVM)       /* useless without VT-x/AMD-V */
+        || (   CPUMIsGuestInPagedProtectedMode(pVCpu)
+            && !HMIsNestedPagingActive(pVM)))
+        return VINF_SUCCESS;    /* ignore */
+
+    /*
+     * Translate the handle into an entry and mapping address for PGM.
+     * We have to take the lock to safely access the mapping address here.
+     */
+    AssertReturn(hRegion < RT_MIN(pVM->iom.s.cMmioRegs, pVM->iom.s.cMmioAlloc), VERR_IOM_INVALID_MMIO_HANDLE);
+#ifdef IN_RING0
+    AssertReturn(hRegion < pVM->iomr0.s.cMmioAlloc, VERR_IOM_INVALID_MMIO_HANDLE);
+    PIOMMMIOENTRYR3 const pRegEntry = &pVM->iomr0.s.paMmioRing3Regs[hRegion];
+    AssertReturn(pRegEntry->cbRegion > 0, VERR_IOM_INVALID_MMIO_HANDLE);
+    AssertReturn(   pVM->iomr0.s.paMmioRegs[hRegion].pDevIns == pDevIns
+                 || (   pVM->iomr0.s.paMmioRegs[hRegion].pDevIns == NULL
+                     && pRegEntry->pDevIns == pDevIns->pDevInsForR3), VERR_ACCESS_DENIED);
+#else
+    PIOMMMIOENTRYR3 const pRegEntry = &pVM->iom.s.paMmioRegs[hRegion];
+    AssertReturn(pRegEntry->cbRegion > 0, VERR_IOM_INVALID_MMIO_HANDLE);
+    AssertReturn(pRegEntry->pDevIns == pDevIns, VERR_ACCESS_DENIED);
+#endif
+    Assert((pRegEntry->cbRegion & GUEST_PAGE_OFFSET_MASK) == 0);
+
+    int rcSem = IOM_LOCK_SHARED(pVM);
+    RTGCPHYS GCPhys = pRegEntry->fMapped ? pRegEntry->GCPhysMapping : NIL_RTGCPHYS;
+    if (rcSem == VINF_SUCCESS)
+        IOM_UNLOCK_SHARED(pVM);
+
+    Assert(!(GCPhys              & GUEST_PAGE_OFFSET_MASK));
+    Assert(!(pRegEntry->cbRegion & GUEST_PAGE_OFFSET_MASK));
+
+    /*
+     * Call PGM to do the job work.
+     *
+     * After the call, all the pages should be non-present, unless there is
+     * a page pool flush pending (unlikely).
+     */
+    int rc = PGMHandlerPhysicalReset(pVM, GCPhys);
+    AssertRC(rc);
+
+# ifdef VBOX_STRICT
+    if (!VMCPU_FF_IS_SET(pVCpu, VMCPU_FF_PGM_SYNC_CR3))
+    {
+        RTGCPHYS cb = pRegEntry->cbRegion;
+        while (cb)
+        {
+            uint64_t fFlags;
+            RTHCPHYS HCPhys;
+            rc = PGMShwGetPage(pVCpu, (RTGCPTR)GCPhys, &fFlags, &HCPhys);
+            Assert(rc == VERR_PAGE_NOT_PRESENT || rc == VERR_PAGE_TABLE_NOT_PRESENT);
+            cb     -= RT_MIN(GUEST_PAGE_SIZE, HOST_PAGE_SIZE);
+            GCPhys += RT_MIN(GUEST_PAGE_SIZE, HOST_PAGE_SIZE);
+        }
+    }
+# endif
+    return rc;
+}
+