Patchwork [v2,02/23] Hierarchical memory region API

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Submitter Avi Kivity
Date July 26, 2011, 11:26 a.m.
Message ID <1311679582-11211-3-git-send-email-avi@redhat.com>
Download mbox | patch
Permalink /patch/106852/
State New
Headers show

Comments

Avi Kivity - July 26, 2011, 11:26 a.m.
The memory API separates the attributes of a memory region (its size, how
reads or writes are handled, dirty logging, and coalescing) from where it
is mapped and whether it is enabled.  This allows a device to configure
a memory region once, then hand it off to its parent bus to map it according
to the bus configuration.

Hierarchical registration also allows a device to compose a region out of
a number of sub-regions with different properties; for example some may be
RAM while others may be MMIO.

Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
---
 Makefile.target |    1 +
 memory.c        |  653 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 memory.h        |  385 ++++++++++++++++++++++++++++++++
 3 files changed, 1039 insertions(+), 0 deletions(-)
 create mode 100644 memory.c
 create mode 100644 memory.h

Patch

diff --git a/Makefile.target b/Makefile.target
index cde509b..8884a56 100644
--- a/Makefile.target
+++ b/Makefile.target
@@ -198,6 +198,7 @@  obj-$(CONFIG_REALLY_VIRTFS) += 9pfs/virtio-9p-device.o
 obj-y += rwhandler.o
 obj-$(CONFIG_KVM) += kvm.o kvm-all.o
 obj-$(CONFIG_NO_KVM) += kvm-stub.o
+obj-y += memory.o
 LIBS+=-lz
 
 QEMU_CFLAGS += $(VNC_TLS_CFLAGS)
diff --git a/memory.c b/memory.c
new file mode 100644
index 0000000..a9cf317
--- /dev/null
+++ b/memory.c
@@ -0,0 +1,653 @@ 
+/*
+ * Physical memory management
+ *
+ * Copyright 2011 Red Hat, Inc. and/or its affiliates
+ *
+ * Authors:
+ *  Avi Kivity <avi@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include "memory.h"
+#include <assert.h>
+
+typedef struct AddrRange AddrRange;
+
+struct AddrRange {
+    uint64_t start;
+    uint64_t size;
+};
+
+static AddrRange addrrange_make(uint64_t start, uint64_t size)
+{
+    return (AddrRange) { start, size };
+}
+
+static bool addrrange_equal(AddrRange r1, AddrRange r2)
+{
+    return r1.start == r2.start && r1.size == r2.size;
+}
+
+static uint64_t addrrange_end(AddrRange r)
+{
+    return r.start + r.size;
+}
+
+static AddrRange addrrange_shift(AddrRange range, int64_t delta)
+{
+    range.start += delta;
+    return range;
+}
+
+static bool addrrange_intersects(AddrRange r1, AddrRange r2)
+{
+    return (r1.start >= r2.start && r1.start < r2.start + r2.size)
+        || (r2.start >= r1.start && r2.start < r1.start + r1.size);
+}
+
+static AddrRange addrrange_intersection(AddrRange r1, AddrRange r2)
+{
+    uint64_t start = MAX(r1.start, r2.start);
+    /* off-by-one arithmetic to prevent overflow */
+    uint64_t end = MIN(addrrange_end(r1) - 1, addrrange_end(r2) - 1);
+    return addrrange_make(start, end - start + 1);
+}
+
+struct CoalescedMemoryRange {
+    AddrRange addr;
+    QTAILQ_ENTRY(CoalescedMemoryRange) link;
+};
+
+typedef struct FlatRange FlatRange;
+typedef struct FlatView FlatView;
+
+/* Range of memory in the global map.  Addresses are absolute. */
+struct FlatRange {
+    MemoryRegion *mr;
+    target_phys_addr_t offset_in_region;
+    AddrRange addr;
+};
+
+/* Flattened global view of current active memory hierarchy.  Kept in sorted
+ * order.
+ */
+struct FlatView {
+    FlatRange *ranges;
+    unsigned nr;
+    unsigned nr_allocated;
+};
+
+#define FOR_EACH_FLAT_RANGE(var, view)          \
+    for (var = (view)->ranges; var < (view)->ranges + (view)->nr; ++var)
+
+static FlatView current_memory_map;
+static MemoryRegion *root_memory_region;
+
+static bool flatrange_equal(FlatRange *a, FlatRange *b)
+{
+    return a->mr == b->mr
+        && addrrange_equal(a->addr, b->addr)
+        && a->offset_in_region == b->offset_in_region;
+}
+
+static void flatview_init(FlatView *view)
+{
+    view->ranges = NULL;
+    view->nr = 0;
+    view->nr_allocated = 0;
+}
+
+/* Insert a range into a given position.  Caller is responsible for maintaining
+ * sorting order.
+ */
+static void flatview_insert(FlatView *view, unsigned pos, FlatRange *range)
+{
+    if (view->nr == view->nr_allocated) {
+        view->nr_allocated = MAX(2 * view->nr, 10);
+        view->ranges = qemu_realloc(view->ranges,
+                                    view->nr_allocated * sizeof(*view->ranges));
+    }
+    memmove(view->ranges + pos + 1, view->ranges + pos,
+            (view->nr - pos) * sizeof(FlatRange));
+    view->ranges[pos] = *range;
+    ++view->nr;
+}
+
+static void flatview_destroy(FlatView *view)
+{
+    qemu_free(view->ranges);
+}
+
+/* Render a memory region into the global view.  Ranges in @view obscure
+ * ranges in @mr.
+ */
+static void render_memory_region(FlatView *view,
+                                 MemoryRegion *mr,
+                                 target_phys_addr_t base,
+                                 AddrRange clip)
+{
+    MemoryRegion *subregion;
+    unsigned i;
+    target_phys_addr_t offset_in_region;
+    uint64_t remain;
+    uint64_t now;
+    FlatRange fr;
+    AddrRange tmp;
+
+    base += mr->addr;
+
+    tmp = addrrange_make(base, mr->size);
+
+    if (!addrrange_intersects(tmp, clip)) {
+        return;
+    }
+
+    clip = addrrange_intersection(tmp, clip);
+
+    if (mr->alias) {
+        base -= mr->alias->addr;
+        base -= mr->alias_offset;
+        render_memory_region(view, mr->alias, base, clip);
+        return;
+    }
+
+    /* Render subregions in priority order. */
+    QTAILQ_FOREACH(subregion, &mr->subregions, subregions_link) {
+        render_memory_region(view, subregion, base, clip);
+    }
+
+    if (!mr->has_ram_addr) {
+        return;
+    }
+
+    offset_in_region = clip.start - base;
+    base = clip.start;
+    remain = clip.size;
+
+    /* Render the region itself into any gaps left by the current view. */
+    for (i = 0; i < view->nr && remain; ++i) {
+        if (base >= addrrange_end(view->ranges[i].addr)) {
+            continue;
+        }
+        if (base < view->ranges[i].addr.start) {
+            now = MIN(remain, view->ranges[i].addr.start - base);
+            fr.mr = mr;
+            fr.offset_in_region = offset_in_region;
+            fr.addr = addrrange_make(base, now);
+            flatview_insert(view, i, &fr);
+            ++i;
+            base += now;
+            offset_in_region += now;
+            remain -= now;
+        }
+        if (base == view->ranges[i].addr.start) {
+            now = MIN(remain, view->ranges[i].addr.size);
+            base += now;
+            offset_in_region += now;
+            remain -= now;
+        }
+    }
+    if (remain) {
+        fr.mr = mr;
+        fr.offset_in_region = offset_in_region;
+        fr.addr = addrrange_make(base, remain);
+        flatview_insert(view, i, &fr);
+    }
+}
+
+/* Render a memory topology into a list of disjoint absolute ranges. */
+static FlatView generate_memory_topology(MemoryRegion *mr)
+{
+    FlatView view;
+
+    flatview_init(&view);
+
+    render_memory_region(&view, mr, 0, addrrange_make(0, UINT64_MAX));
+
+    return view;
+}
+
+static void memory_region_update_topology(void)
+{
+    FlatView old_view = current_memory_map;
+    FlatView new_view = generate_memory_topology(root_memory_region);
+    unsigned iold, inew;
+    FlatRange *frold, *frnew;
+    ram_addr_t phys_offset, region_offset;
+
+    /* Generate a symmetric difference of the old and new memory maps.
+     * Kill ranges in the old map, and instantiate ranges in the new map.
+     */
+    iold = inew = 0;
+    while (iold < old_view.nr || inew < new_view.nr) {
+        if (iold < old_view.nr) {
+            frold = &old_view.ranges[iold];
+        } else {
+            frold = NULL;
+        }
+        if (inew < new_view.nr) {
+            frnew = &new_view.ranges[inew];
+        } else {
+            frnew = NULL;
+        }
+
+        if (frold
+            && (!frnew
+                || frold->addr.start < frnew->addr.start
+                || (frold->addr.start == frnew->addr.start
+                    && !flatrange_equal(frold, frnew)))) {
+            /* In old, but (not in new, or in new but attributes changed). */
+
+            cpu_register_physical_memory(frold->addr.start, frold->addr.size,
+                                         IO_MEM_UNASSIGNED);
+            ++iold;
+        } else if (frold && frnew && flatrange_equal(frold, frnew)) {
+            /* In both (logging may have changed) */
+
+            ++iold;
+            ++inew;
+            /* FIXME: dirty logging */
+        } else {
+            /* In new */
+
+            phys_offset = frnew->mr->ram_addr;
+            region_offset = frnew->offset_in_region;
+            /* cpu_register_physical_memory_log() wants region_offset for
+             * mmio, but prefers offseting phys_offset for RAM.  Humour it.
+             */
+            if ((phys_offset & ~TARGET_PAGE_MASK) <= IO_MEM_ROM) {
+                phys_offset += region_offset;
+                region_offset = 0;
+            }
+
+            cpu_register_physical_memory_log(frnew->addr.start,
+                                             frnew->addr.size,
+                                             phys_offset,
+                                             region_offset,
+                                             0);
+            ++inew;
+        }
+    }
+    current_memory_map = new_view;
+    flatview_destroy(&old_view);
+}
+
+void memory_region_init(MemoryRegion *mr,
+                        const char *name,
+                        uint64_t size)
+{
+    mr->ops = NULL;
+    mr->parent = NULL;
+    mr->size = size;
+    mr->addr = 0;
+    mr->offset = 0;
+    mr->has_ram_addr = false;
+    mr->priority = 0;
+    mr->may_overlap = false;
+    mr->alias = NULL;
+    QTAILQ_INIT(&mr->subregions);
+    memset(&mr->subregions_link, 0, sizeof mr->subregions_link);
+    QTAILQ_INIT(&mr->coalesced);
+    mr->name = qemu_strdup(name);
+}
+
+static bool memory_region_access_valid(MemoryRegion *mr,
+                                       target_phys_addr_t addr,
+                                       unsigned size)
+{
+    if (!mr->ops->valid.unaligned && (addr & (size - 1))) {
+        return false;
+    }
+
+    /* Treat zero as compatibility all valid */
+    if (!mr->ops->valid.max_access_size) {
+        return true;
+    }
+
+    if (size > mr->ops->valid.max_access_size
+        || size < mr->ops->valid.min_access_size) {
+        return false;
+    }
+    return true;
+}
+
+static uint32_t memory_region_read_thunk_n(void *_mr,
+                                           target_phys_addr_t addr,
+                                           unsigned size)
+{
+    MemoryRegion *mr = _mr;
+    unsigned access_size, access_size_min, access_size_max;
+    uint64_t access_mask;
+    uint32_t data = 0, tmp;
+    unsigned i;
+
+    if (!memory_region_access_valid(mr, addr, size)) {
+        return -1U; /* FIXME: better signalling */
+    }
+
+    /* FIXME: support unaligned access */
+
+    access_size_min = mr->ops->impl.min_access_size;
+    if (!access_size_min) {
+        access_size_min = 1;
+    }
+    access_size_max = mr->ops->impl.max_access_size;
+    if (!access_size_max) {
+        access_size_max = 4;
+    }
+    access_size = MAX(MIN(size, access_size_max), access_size_min);
+    access_mask = -1ULL >> (64 - access_size * 8);
+    addr += mr->offset;
+    for (i = 0; i < size; i += access_size) {
+        /* FIXME: big-endian support */
+        tmp = mr->ops->read(mr->opaque, addr + i, access_size);
+        data |= (tmp & access_mask) << (i * 8);
+    }
+
+    return data;
+}
+
+static void memory_region_write_thunk_n(void *_mr,
+                                        target_phys_addr_t addr,
+                                        unsigned size,
+                                        uint64_t data)
+{
+    MemoryRegion *mr = _mr;
+    unsigned access_size, access_size_min, access_size_max;
+    uint64_t access_mask;
+    unsigned i;
+
+    if (!memory_region_access_valid(mr, addr, size)) {
+        return; /* FIXME: better signalling */
+    }
+
+    /* FIXME: support unaligned access */
+
+    access_size_min = mr->ops->impl.min_access_size;
+    if (!access_size_min) {
+        access_size_min = 1;
+    }
+    access_size_max = mr->ops->impl.max_access_size;
+    if (!access_size_max) {
+        access_size_max = 4;
+    }
+    access_size = MAX(MIN(size, access_size_max), access_size_min);
+    access_mask = -1ULL >> (64 - access_size * 8);
+    addr += mr->offset;
+    for (i = 0; i < size; i += access_size) {
+        /* FIXME: big-endian support */
+        mr->ops->write(mr->opaque, addr + i, (data >> (i * 8)) & access_mask,
+                       access_size);
+    }
+}
+
+static uint32_t memory_region_read_thunk_b(void *mr, target_phys_addr_t addr)
+{
+    return memory_region_read_thunk_n(mr, addr, 1);
+}
+
+static uint32_t memory_region_read_thunk_w(void *mr, target_phys_addr_t addr)
+{
+    return memory_region_read_thunk_n(mr, addr, 2);
+}
+
+static uint32_t memory_region_read_thunk_l(void *mr, target_phys_addr_t addr)
+{
+    return memory_region_read_thunk_n(mr, addr, 4);
+}
+
+static void memory_region_write_thunk_b(void *mr, target_phys_addr_t addr,
+                                        uint32_t data)
+{
+    memory_region_write_thunk_n(mr, addr, 1, data);
+}
+
+static void memory_region_write_thunk_w(void *mr, target_phys_addr_t addr,
+                                        uint32_t data)
+{
+    memory_region_write_thunk_n(mr, addr, 2, data);
+}
+
+static void memory_region_write_thunk_l(void *mr, target_phys_addr_t addr,
+                                        uint32_t data)
+{
+    memory_region_write_thunk_n(mr, addr, 4, data);
+}
+
+static CPUReadMemoryFunc * const memory_region_read_thunk[] = {
+    memory_region_read_thunk_b,
+    memory_region_read_thunk_w,
+    memory_region_read_thunk_l,
+};
+
+static CPUWriteMemoryFunc * const memory_region_write_thunk[] = {
+    memory_region_write_thunk_b,
+    memory_region_write_thunk_w,
+    memory_region_write_thunk_l,
+};
+
+void memory_region_init_io(MemoryRegion *mr,
+                           const MemoryRegionOps *ops,
+                           void *opaque,
+                           const char *name,
+                           uint64_t size)
+{
+    memory_region_init(mr, name, size);
+    mr->ops = ops;
+    mr->opaque = opaque;
+    mr->has_ram_addr = true;
+    mr->ram_addr = cpu_register_io_memory(memory_region_read_thunk,
+                                          memory_region_write_thunk,
+                                          mr,
+                                          mr->ops->endianness);
+}
+
+void memory_region_init_ram(MemoryRegion *mr,
+                            DeviceState *dev,
+                            const char *name,
+                            uint64_t size)
+{
+    memory_region_init(mr, name, size);
+    mr->has_ram_addr = true;
+    mr->ram_addr = qemu_ram_alloc(dev, name, size);
+}
+
+void memory_region_init_ram_ptr(MemoryRegion *mr,
+                                DeviceState *dev,
+                                const char *name,
+                                uint64_t size,
+                                void *ptr)
+{
+    memory_region_init(mr, name, size);
+    mr->has_ram_addr = true;
+    mr->ram_addr = qemu_ram_alloc_from_ptr(dev, name, size, ptr);
+}
+
+void memory_region_init_alias(MemoryRegion *mr,
+                              const char *name,
+                              MemoryRegion *orig,
+                              target_phys_addr_t offset,
+                              uint64_t size)
+{
+    memory_region_init(mr, name, size);
+    mr->alias = orig;
+    mr->alias_offset = offset;
+}
+
+void memory_region_destroy(MemoryRegion *mr)
+{
+    assert(QTAILQ_EMPTY(&mr->subregions));
+    memory_region_clear_coalescing(mr);
+    qemu_free((char *)mr->name);
+}
+
+uint64_t memory_region_size(MemoryRegion *mr)
+{
+    return mr->size;
+}
+
+void memory_region_set_offset(MemoryRegion *mr, target_phys_addr_t offset)
+{
+    mr->offset = offset;
+}
+
+void memory_region_set_log(MemoryRegion *mr, bool log, unsigned client)
+{
+    /* FIXME */
+}
+
+bool memory_region_get_dirty(MemoryRegion *mr, target_phys_addr_t addr,
+                             unsigned client)
+{
+    /* FIXME */
+    return true;
+}
+
+void memory_region_set_dirty(MemoryRegion *mr, target_phys_addr_t addr)
+{
+    /* FIXME */
+}
+
+void memory_region_sync_dirty_bitmap(MemoryRegion *mr)
+{
+    /* FIXME */
+}
+
+void memory_region_set_readonly(MemoryRegion *mr, bool readonly)
+{
+    /* FIXME */
+}
+
+void memory_region_reset_dirty(MemoryRegion *mr, target_phys_addr_t addr,
+                               target_phys_addr_t size, unsigned client)
+{
+    /* FIXME */
+}
+
+void *memory_region_get_ram_ptr(MemoryRegion *mr)
+{
+    if (mr->alias) {
+        return memory_region_get_ram_ptr(mr->alias) + mr->alias_offset;
+    }
+
+    assert(mr->has_ram_addr);
+
+    return qemu_get_ram_ptr(mr->ram_addr);
+}
+
+static void memory_region_update_coalesced_range(MemoryRegion *mr)
+{
+    FlatRange *fr;
+    CoalescedMemoryRange *cmr;
+    AddrRange tmp;
+
+    FOR_EACH_FLAT_RANGE(fr, &current_memory_map) {
+        if (fr->mr == mr) {
+            qemu_unregister_coalesced_mmio(fr->addr.start, fr->addr.size);
+            QTAILQ_FOREACH(cmr, &mr->coalesced, link) {
+                tmp = addrrange_shift(cmr->addr,
+                                      fr->addr.start - fr->offset_in_region);
+                if (!addrrange_intersects(tmp, fr->addr)) {
+                    continue;
+                }
+                tmp = addrrange_intersection(tmp, fr->addr);
+                qemu_register_coalesced_mmio(tmp.start, tmp.size);
+            }
+        }
+    }
+}
+
+void memory_region_set_coalescing(MemoryRegion *mr)
+{
+    memory_region_clear_coalescing(mr);
+    memory_region_add_coalescing(mr, 0, mr->size);
+}
+
+void memory_region_add_coalescing(MemoryRegion *mr,
+                                  target_phys_addr_t offset,
+                                  uint64_t size)
+{
+    CoalescedMemoryRange *cmr = qemu_malloc(sizeof(*cmr));
+
+    cmr->addr = addrrange_make(offset, size);
+    QTAILQ_INSERT_TAIL(&mr->coalesced, cmr, link);
+    memory_region_update_coalesced_range(mr);
+}
+
+void memory_region_clear_coalescing(MemoryRegion *mr)
+{
+    CoalescedMemoryRange *cmr;
+
+    while (!QTAILQ_EMPTY(&mr->coalesced)) {
+        cmr = QTAILQ_FIRST(&mr->coalesced);
+        QTAILQ_REMOVE(&mr->coalesced, cmr, link);
+        qemu_free(cmr);
+    }
+    memory_region_update_coalesced_range(mr);
+}
+
+static void memory_region_add_subregion_common(MemoryRegion *mr,
+                                               target_phys_addr_t offset,
+                                               MemoryRegion *subregion)
+{
+    MemoryRegion *other;
+
+    assert(!subregion->parent);
+    subregion->parent = mr;
+    subregion->addr = offset;
+    QTAILQ_FOREACH(other, &mr->subregions, subregions_link) {
+        if (subregion->may_overlap || other->may_overlap) {
+            continue;
+        }
+        if (offset >= other->offset + other->size
+            || offset + subregion->size <= other->offset) {
+            continue;
+        }
+        printf("warning: subregion collision %llx/%llx vs %llx/%llx\n",
+               (unsigned long long)offset,
+               (unsigned long long)subregion->size,
+               (unsigned long long)other->offset,
+               (unsigned long long)other->size);
+    }
+    QTAILQ_FOREACH(other, &mr->subregions, subregions_link) {
+        if (subregion->priority >= other->priority) {
+            QTAILQ_INSERT_BEFORE(other, subregion, subregions_link);
+            goto done;
+        }
+    }
+    QTAILQ_INSERT_TAIL(&mr->subregions, subregion, subregions_link);
+done:
+    memory_region_update_topology();
+}
+
+
+void memory_region_add_subregion(MemoryRegion *mr,
+                                 target_phys_addr_t offset,
+                                 MemoryRegion *subregion)
+{
+    subregion->may_overlap = false;
+    subregion->priority = 0;
+    memory_region_add_subregion_common(mr, offset, subregion);
+}
+
+void memory_region_add_subregion_overlap(MemoryRegion *mr,
+                                         target_phys_addr_t offset,
+                                         MemoryRegion *subregion,
+                                         unsigned priority)
+{
+    subregion->may_overlap = true;
+    subregion->priority = priority;
+    memory_region_add_subregion_common(mr, offset, subregion);
+}
+
+void memory_region_del_subregion(MemoryRegion *mr,
+                                 MemoryRegion *subregion)
+{
+    assert(subregion->parent == mr);
+    subregion->parent = NULL;
+    QTAILQ_REMOVE(&mr->subregions, subregion, subregions_link);
+    memory_region_update_topology();
+}
diff --git a/memory.h b/memory.h
new file mode 100644
index 0000000..a4c94bd
--- /dev/null
+++ b/memory.h
@@ -0,0 +1,385 @@ 
+/*
+ * Physical memory management API
+ *
+ * Copyright 2011 Red Hat, Inc. and/or its affiliates
+ *
+ * Authors:
+ *  Avi Kivity <avi@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef MEMORY_H
+#define MEMORY_H
+
+#ifndef CONFIG_USER_ONLY
+
+#include <stdint.h>
+#include <stdbool.h>
+#include "qemu-common.h"
+#include "cpu-common.h"
+#include "targphys.h"
+#include "qemu-queue.h"
+
+typedef struct MemoryRegionOps MemoryRegionOps;
+typedef struct MemoryRegion MemoryRegion;
+
+/* Must match *_DIRTY_FLAGS in cpu-all.h.  To be replaced with dynamic
+ * registration.
+ */
+#define DIRTY_MEMORY_VGA       0
+#define DIRTY_MEMORY_CODE      1
+#define DIRTY_MEMORY_MIGRATION 3
+
+/*
+ * Memory region callbacks
+ */
+struct MemoryRegionOps {
+    /* Read from the memory region. @addr is relative to @mr; @size is
+     * in bytes. */
+    uint64_t (*read)(void *opaque,
+                     target_phys_addr_t addr,
+                     unsigned size);
+    /* Write to the memory region. @addr is relative to @mr; @size is
+     * in bytes. */
+    void (*write)(void *opaque,
+                  target_phys_addr_t addr,
+                  uint64_t data,
+                  unsigned size);
+
+    enum device_endian endianness;
+    /* Guest-visible constraints: */
+    struct {
+        /* If nonzero, specify bounds on access sizes beyond which a machine
+         * check is thrown.
+         */
+        unsigned min_access_size;
+        unsigned max_access_size;
+        /* If true, unaligned accesses are supported.  Otherwise unaligned
+         * accesses throw machine checks.
+         */
+         bool unaligned;
+    } valid;
+    /* Internal implementation constraints: */
+    struct {
+        /* If nonzero, specifies the minimum size implemented.  Smaller sizes
+         * will be rounded upwards and a partial result will be returned.
+         */
+        unsigned min_access_size;
+        /* If nonzero, specifies the maximum size implemented.  Larger sizes
+         * will be done as a series of accesses with smaller sizes.
+         */
+        unsigned max_access_size;
+        /* If true, unaligned accesses are supported.  Otherwise all accesses
+         * are converted to (possibly multiple) naturally aligned accesses.
+         */
+         bool unaligned;
+    } impl;
+};
+
+typedef struct CoalescedMemoryRange CoalescedMemoryRange;
+
+struct MemoryRegion {
+    /* All fields are private - violators will be prosecuted */
+    const MemoryRegionOps *ops;
+    void *opaque;
+    MemoryRegion *parent;
+    uint64_t size;
+    target_phys_addr_t addr;
+    target_phys_addr_t offset;
+    ram_addr_t ram_addr;
+    bool has_ram_addr;
+    MemoryRegion *alias;
+    target_phys_addr_t alias_offset;
+    unsigned priority;
+    bool may_overlap;
+    QTAILQ_HEAD(subregions, MemoryRegion) subregions;
+    QTAILQ_ENTRY(MemoryRegion) subregions_link;
+    QTAILQ_HEAD(coalesced_ranges, CoalescedMemoryRange) coalesced;
+    const char *name;
+};
+
+/**
+ * memory_region_init: Initialize a memory region
+ *
+ * The region typically acts as a container for other memory regions.  Us
+ * memory_region_add_subregion() to add subregions.
+ *
+ * @mr: the #MemoryRegion to be initialized
+ * @name: used for debugging; not visible to the user or ABI
+ * @size: size of the region; any subregions beyond this size will be clipped
+ */
+void memory_region_init(MemoryRegion *mr,
+                        const char *name,
+                        uint64_t size);
+/**
+ * memory_region_init_io: Initialize an I/O memory region.
+ *
+ * Accesses into the region will be cause the callbacks in @ops to be called.
+ * if @size is nonzero, subregions will be clipped to @size.
+ *
+ * @mr: the #MemoryRegion to be initialized.
+ * @ops: a structure containing read and write callbacks to be used when
+ *       I/O is performed on the region.
+ * @opaque: passed to to the read and write callbacks of the @ops structure.
+ * @name: used for debugging; not visible to the user or ABI
+ * @size: size of the region.
+ */
+void memory_region_init_io(MemoryRegion *mr,
+                           const MemoryRegionOps *ops,
+                           void *opaque,
+                           const char *name,
+                           uint64_t size);
+
+/**
+ * memory_region_init_ram:  Initialize RAM memory region.  Accesses into the
+ *                          region will be modify memory directly.
+ *
+ * @mr: the #MemoryRegion to be initialized.
+ * @dev: a device associated with the region; may be %NULL.
+ * @name: the name of the region; the pair (@dev, @name) must be globally
+ *        unique.  The name is part of the save/restore ABI and so cannot be
+ *        changed.
+ * @size: size of the region.
+ */
+void memory_region_init_ram(MemoryRegion *mr,
+                            DeviceState *dev, /* FIXME: layering violation */
+                            const char *name,
+                            uint64_t size);
+
+/**
+ * memory_region_init_ram:  Initialize RAM memory region from a user-provided.
+ *                          pointer.  Accesses into the region will be modify
+ *                          memory directly.
+ *
+ * @mr: the #MemoryRegion to be initialized.
+ * @dev: a device associated with the region; may be %NULL.
+ * @name: the name of the region; the pair (@dev, @name) must be globally
+ *        unique.  The name is part of the save/restore ABI and so cannot be
+ *        changed.
+ * @size: size of the region.
+ * @ptr: memory to be mapped; must contain at least @size bytes.
+ */
+void memory_region_init_ram_ptr(MemoryRegion *mr,
+                                DeviceState *dev, /* FIXME: layering violation */
+                                const char *name,
+                                uint64_t size,
+                                void *ptr);
+
+/**
+ * memory_region_init_alias: Initialize a memory region that aliases all or a
+ *                           part of another memory region.
+ *
+ * @mr: the #MemoryRegion to be initialized.
+ * @name: used for debugging; not visible to the user or ABI
+ * @orig: the region to be referenced; @mr will be equivalent to
+ *        @orig between @offset and @offset + @size - 1.
+ * @offset: start of the section in @orig to be referenced.
+ * @size: size of the region.
+ */
+void memory_region_init_alias(MemoryRegion *mr,
+                              const char *name,
+                              MemoryRegion *orig,
+                              target_phys_addr_t offset,
+                              uint64_t size);
+/**
+ * memory_region_destroy: Destroy a memory region and relaim all resources.
+ *
+ * @mr: the region to be destroyed.  May not currently be a subregion
+ *      (see memory_region_add_subregion()) or referenced in an alias
+ *      (see memory_region_init_alias()).
+ */
+void memory_region_destroy(MemoryRegion *mr);
+
+/**
+ * memory_region_size: get a memory region's size.
+ *
+ * @mr: the memory region being queried.
+ */
+uint64_t memory_region_size(MemoryRegion *mr);
+
+/**
+ * memory_region_get_ram_ptr: Get a pointer into a RAM memory region.
+ *
+ * Returns a host pointer to a RAM memory region (created with
+ * memory_region_init_ram() or memory_region_init_ram_ptr()).  Use with
+ * care.
+ *
+ * @mr: the memory region being queried.
+ */
+void *memory_region_get_ram_ptr(MemoryRegion *mr);
+
+/**
+ * memory_region_set_offset: Sets an offset to be added to MemoryRegionOps
+ *                           callbacks.
+ *
+ * This function is deprecated and should not be used in new code.
+ */
+void memory_region_set_offset(MemoryRegion *mr, target_phys_addr_t offset);
+
+/**
+ * memory_region_set_log: Turn dirty logging on or off for a region.
+ *
+ * Turns dirty logging on or off for a specified client (display, migration).
+ * Only meaningful for RAM regions.
+ *
+ * @mr: the memory region being updated.
+ * @log: whether dirty logging is to be enabled or disabled.
+ * @client: the user of the logging information; %DIRTY_MEMORY_MIGRATION or
+ *          %DIRTY_MEMORY_VGA.
+ */
+void memory_region_set_log(MemoryRegion *mr, bool log, unsigned client);
+
+/**
+ * memory_region_get_dirty: Check whether a page is dirty for a specified
+ *                          client.
+ *
+ * Checks whether a page has been written to since the last
+ * call to memory_region_reset_dirty() with the same @client.  Dirty logging
+ * must be enabled.
+ *
+ * @mr: the memory region being queried.
+ * @addr: the address (relative to the start of the region) being queried.
+ * @client: the user of the logging information; %DIRTY_MEMORY_MIGRATION or
+ *          %DIRTY_MEMORY_VGA.
+ */
+bool memory_region_get_dirty(MemoryRegion *mr, target_phys_addr_t addr,
+                             unsigned client);
+
+/**
+ * memory_region_set_dirty: Mark a page as dirty in a memory region.
+ *
+ * Marks a page as dirty, after it has been dirtied outside guest code.
+ *
+ * @mr: the memory region being queried.
+ * @addr: the address (relative to the start of the region) being dirtied.
+ */
+void memory_region_set_dirty(MemoryRegion *mr, target_phys_addr_t addr);
+
+/**
+ * memory_region_sync_dirty_bitmap: Synchronize a region's dirty bitmap with
+ *                                  any external TLBs (e.g. kvm)
+ *
+ * Flushes dirty information from accelerators such as kvm and vhost-net
+ * and makes it available to users of the memory API.
+ *
+ * @mr: the region being flushed.
+ */
+void memory_region_sync_dirty_bitmap(MemoryRegion *mr);
+
+/**
+ * memory_region_reset_dirty: Mark a range of pages as clean, for a specified
+ *                            client.
+ *
+ * Marks a range of pages as no longer dirty.
+ *
+ * @mr: the region being updated.
+ * @addr: the start of the subrange being cleaned.
+ * @size: the size of the subrange being cleaned.
+ * @client: the user of the logging information; %DIRTY_MEMORY_MIGRATION or
+ *          %DIRTY_MEMORY_VGA.
+ */
+void memory_region_reset_dirty(MemoryRegion *mr, target_phys_addr_t addr,
+                               target_phys_addr_t size, unsigned client);
+
+/**
+ * memory_region_set_readonly: Turn a memory region read-only (or read-write)
+ *
+ * Allows a memory region to be marked as read-only (turning it into a ROM).
+ * only useful on RAM regions.
+ *
+ * @mr: the region being updated.
+ * @readonly: whether rhe region is to be ROM or RAM.
+ */
+void memory_region_set_readonly(MemoryRegion *mr, bool readonly);
+
+/**
+ * memory_region_set_coalescing: Enable memory coalescing for the region.
+ *
+ * Enabled writes to a region to be queued for later processing. MMIO ->write
+ * callbacks may be delayed until a non-coalesced MMIO is issued.
+ * Only useful for IO regions.  Roughly similar to write-combining hardware.
+ *
+ * @mr: the memory region to be write coalesced
+ */
+void memory_region_set_coalescing(MemoryRegion *mr);
+
+/**
+ * memory_region_add_coalescing: Enable memory coalescing for a sub-range of
+ *                               a region.
+ *
+ * Like memory_region_set_coalescing(), but works on a sub-range of a region.
+ * Multiple calls can be issued coalesced disjoint ranges.
+ *
+ * @mr: the memory region to be updated.
+ * @offset: the start of the range within the region to be coalesced.
+ * @size: the size of the subrange to be coalesced.
+ */
+void memory_region_add_coalescing(MemoryRegion *mr,
+                                  target_phys_addr_t offset,
+                                  uint64_t size);
+
+/**
+ * memory_region_clear_coalescing: Disable MMIO coalescing for the region.
+ *
+ * Disables any coalescing caused by memory_region_set_coalescing() or
+ * memory_region_add_coalescing().  Roughly equivalent to uncacheble memory
+ * hardware.
+ *
+ * @mr: the memory region to be updated.
+ */
+void memory_region_clear_coalescing(MemoryRegion *mr);
+
+/**
+ * memory_region_add_subregion: Add a sub-region to a container.
+ *
+ * Adds a sub-region at @offset.  The sub-region may not overlap with other
+ * subregions (except for those explicitly marked as overlapping).  A region
+ * may only be added once as a subregion (unless removed with
+ * memory_region_del_subregion()); use memory_region_init_alias() if you
+ * want a region to be a subregion in multiple locations.
+ *
+ * @mr: the region to contain the new subregion; must be a container
+ *      initialized with memory_region_init().
+ * @offset: the offset relative to @mr where @subregion is added.
+ * @subregion: the subregion to be added.
+ */
+void memory_region_add_subregion(MemoryRegion *mr,
+                                 target_phys_addr_t offset,
+                                 MemoryRegion *subregion);
+/**
+ * memory_region_add_subregion: Add a sub-region to a container, with overlap.
+ *
+ * Adds a sub-region at @offset.  The sub-region may overlap with other
+ * subregions.  Conflicts are resolved by having a higher @priority hide a
+ * lower @priority. Subregions without priority are taken as @priority 0.
+ * A region may only be added once as a subregion (unless removed with
+ * memory_region_del_subregion()); use memory_region_init_alias() if you
+ * want a region to be a subregion in multiple locations.
+ *
+ * @mr: the region to contain the new subregion; must be a container
+ *      initialized with memory_region_init().
+ * @offset: the offset relative to @mr where @subregion is added.
+ * @subregion: the subregion to be added.
+ * @priority: used for resolving overlaps; highest priority wins.
+ */
+void memory_region_add_subregion_overlap(MemoryRegion *mr,
+                                         target_phys_addr_t offset,
+                                         MemoryRegion *subregion,
+                                         unsigned priority);
+/**
+ * memory_region_del_subregion: Remove a subregion.
+ *
+ * Removes a subregion from its container.
+ *
+ * @mr: the container to be updated.
+ * @subregion: the region being removed; must be a current subregion of @mr.
+ */
+void memory_region_del_subregion(MemoryRegion *mr,
+                                 MemoryRegion *subregion);
+
+#endif
+
+#endif