Archipelago » qemu

/*

 * 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.

 *

 * Contributions after 2012-01-13 are licensed under the terms of the

 * GNU GPL, version 2 or (at your option) any later version.

 */

#include "memory.h"

#include "exec-memory.h"

#include "ioport.h"

#include "bitops.h"

#include "kvm.h"

#include <assert.h>

#define WANT_EXEC_OBSOLETE

#include "exec-obsolete.h"

unsigned memory_region_transaction_depth = 0;

static bool memory_region_update_pending = false;

static bool global_dirty_log = false;

static QTAILQ_HEAD(memory_listeners, MemoryListener) memory_listeners

    = QTAILQ_HEAD_INITIALIZER(memory_listeners);

typedef struct AddrRange AddrRange;

/*

 * Note using signed integers limits us to physical addresses at most

 * 63 bits wide.  They are needed for negative offsetting in aliases

 * (large MemoryRegion::alias_offset).

 */

struct AddrRange {

    Int128 start;

    Int128 size;

};

static AddrRange addrrange_make(Int128 start, Int128 size)

{

    return (AddrRange) { start, size };

}

static bool addrrange_equal(AddrRange r1, AddrRange r2)

{

    return int128_eq(r1.start, r2.start) && int128_eq(r1.size, r2.size);

}

static Int128 addrrange_end(AddrRange r)

{

    return int128_add(r.start, r.size);

}

static AddrRange addrrange_shift(AddrRange range, Int128 delta)

{

    int128_addto(&range.start, delta);

    return range;

}

static bool addrrange_contains(AddrRange range, Int128 addr)

{

    return int128_ge(addr, range.start)

        && int128_lt(addr, addrrange_end(range));

}

static bool addrrange_intersects(AddrRange r1, AddrRange r2)

{

    return addrrange_contains(r1, r2.start)

        || addrrange_contains(r2, r1.start);

}

static AddrRange addrrange_intersection(AddrRange r1, AddrRange r2)

{

    Int128 start = int128_max(r1.start, r2.start);

    Int128 end = int128_min(addrrange_end(r1), addrrange_end(r2));

    return addrrange_make(start, int128_sub(end, start));

}

enum ListenerDirection { Forward, Reverse };

static bool memory_listener_match(MemoryListener *listener,

                                  MemoryRegionSection *section)

{

    return !listener->address_space_filter

        || listener->address_space_filter == section->address_space;

}

#define MEMORY_LISTENER_CALL_GLOBAL(_callback, _direction, _args...)    \

    do {                                                                \

        MemoryListener *_listener;                                      \

                                                                        \

        switch (_direction) {                                           \

        case Forward:                                                   \

            QTAILQ_FOREACH(_listener, &memory_listeners, link) {        \

                _listener->_callback(_listener, ##_args);               \

            }                                                           \

            break;                                                      \

        case Reverse:                                                   \

            QTAILQ_FOREACH_REVERSE(_listener, &memory_listeners,        \

                                   memory_listeners, link) {            \

                _listener->_callback(_listener, ##_args);               \

            }                                                           \

            break;                                                      \

        default:                                                        \

            abort();                                                    \

        }                                                               \

    } while (0)

#define MEMORY_LISTENER_CALL(_callback, _direction, _section, _args...) \

    do {                                                                \

        MemoryListener *_listener;                                      \

                                                                        \

        switch (_direction) {                                           \

        case Forward:                                                   \

            QTAILQ_FOREACH(_listener, &memory_listeners, link) {        \

                if (memory_listener_match(_listener, _section)) {       \

                    _listener->_callback(_listener, _section, ##_args); \

                }                                                       \

            }                                                           \

            break;                                                      \

        case Reverse:                                                   \

            QTAILQ_FOREACH_REVERSE(_listener, &memory_listeners,        \

                                   memory_listeners, link) {            \

                if (memory_listener_match(_listener, _section)) {       \

                    _listener->_callback(_listener, _section, ##_args); \

                }                                                       \

            }                                                           \

            break;                                                      \

        default:                                                        \

            abort();                                                    \

        }                                                               \

    } while (0)

#define MEMORY_LISTENER_UPDATE_REGION(fr, as, dir, callback)            \

    MEMORY_LISTENER_CALL(callback, dir, (&(MemoryRegionSection) {       \

        .mr = (fr)->mr,                                                 \

        .address_space = (as)->root,                                    \

        .offset_within_region = (fr)->offset_in_region,                 \

        .size = int128_get64((fr)->addr.size),                          \

        .offset_within_address_space = int128_get64((fr)->addr.start),  \

        .readonly = (fr)->readonly,                                     \

              }))

struct CoalescedMemoryRange {

    AddrRange addr;

    QTAILQ_ENTRY(CoalescedMemoryRange) link;

};

struct MemoryRegionIoeventfd {

    AddrRange addr;

    bool match_data;

    uint64_t data;

    EventNotifier *e;

};

static bool memory_region_ioeventfd_before(MemoryRegionIoeventfd a,

                                           MemoryRegionIoeventfd b)

{

    if (int128_lt(a.addr.start, b.addr.start)) {

        return true;

    } else if (int128_gt(a.addr.start, b.addr.start)) {

        return false;

    } else if (int128_lt(a.addr.size, b.addr.size)) {

        return true;

    } else if (int128_gt(a.addr.size, b.addr.size)) {

        return false;

    } else if (a.match_data < b.match_data) {

        return true;

    } else  if (a.match_data > b.match_data) {

        return false;

    } else if (a.match_data) {

        if (a.data < b.data) {

            return true;

        } else if (a.data > b.data) {

            return false;

        }

    }

    if (a.e < b.e) {

        return true;

    } else if (a.e > b.e) {

        return false;

    }

    return false;

}

static bool memory_region_ioeventfd_equal(MemoryRegionIoeventfd a,

                                          MemoryRegionIoeventfd b)

{

    return !memory_region_ioeventfd_before(a, b)

        && !memory_region_ioeventfd_before(b, a);

}

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;

    uint8_t dirty_log_mask;

    bool readable;

    bool readonly;

};

/* Flattened global view of current active memory hierarchy.  Kept in sorted

 * order.

 */

struct FlatView {

    FlatRange *ranges;

    unsigned nr;

    unsigned nr_allocated;

};

typedef struct AddressSpace AddressSpace;

typedef struct AddressSpaceOps AddressSpaceOps;

/* A system address space - I/O, memory, etc. */

struct AddressSpace {

    MemoryRegion *root;

    FlatView current_map;

    int ioeventfd_nb;

    MemoryRegionIoeventfd *ioeventfds;

};

#define FOR_EACH_FLAT_RANGE(var, view)          \

    for (var = (view)->ranges; var < (view)->ranges + (view)->nr; ++var)

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

        && a->readable == b->readable

        && a->readonly == b->readonly;

}

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 = g_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)

{

    g_free(view->ranges);

}

static bool can_merge(FlatRange *r1, FlatRange *r2)

{

    return int128_eq(addrrange_end(r1->addr), r2->addr.start)

        && r1->mr == r2->mr

        && int128_eq(int128_add(int128_make64(r1->offset_in_region),

                                r1->addr.size),

                     int128_make64(r2->offset_in_region))

        && r1->dirty_log_mask == r2->dirty_log_mask

        && r1->readable == r2->readable

        && r1->readonly == r2->readonly;

}

/* Attempt to simplify a view by merging ajacent ranges */

static void flatview_simplify(FlatView *view)

{

    unsigned i, j;

    i = 0;

    while (i < view->nr) {

        j = i + 1;

        while (j < view->nr

               && can_merge(&view->ranges[j-1], &view->ranges[j])) {

            int128_addto(&view->ranges[i].addr.size, view->ranges[j].addr.size);

            ++j;

        }

        ++i;

        memmove(&view->ranges[i], &view->ranges[j],

                (view->nr - j) * sizeof(view->ranges[j]));

        view->nr -= j - i;

    }

}

static void memory_region_read_accessor(void *opaque,

                                        target_phys_addr_t addr,

                                        uint64_t *value,

                                        unsigned size,

                                        unsigned shift,

                                        uint64_t mask)

{

    MemoryRegion *mr = opaque;

    uint64_t tmp;

    tmp = mr->ops->read(mr->opaque, addr, size);

    *value |= (tmp & mask) << shift;

}

static void memory_region_write_accessor(void *opaque,

                                         target_phys_addr_t addr,

                                         uint64_t *value,

                                         unsigned size,

                                         unsigned shift,

                                         uint64_t mask)

{

    MemoryRegion *mr = opaque;

    uint64_t tmp;

    tmp = (*value >> shift) & mask;

    mr->ops->write(mr->opaque, addr, tmp, size);

}

static void access_with_adjusted_size(target_phys_addr_t addr,

                                      uint64_t *value,

                                      unsigned size,

                                      unsigned access_size_min,

                                      unsigned access_size_max,

                                      void (*access)(void *opaque,

                                                     target_phys_addr_t addr,

                                                     uint64_t *value,

                                                     unsigned size,

                                                     unsigned shift,

                                                     uint64_t mask),

                                      void *opaque)

{

    uint64_t access_mask;

    unsigned access_size;

    unsigned i;

    if (!access_size_min) {

        access_size_min = 1;

    }

    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);

    for (i = 0; i < size; i += access_size) {

        /* FIXME: big-endian support */

        access(opaque, addr + i, value, access_size, i * 8, access_mask);

    }

}

static AddressSpace address_space_memory;

static const MemoryRegionPortio *find_portio(MemoryRegion *mr, uint64_t offset,

                                             unsigned width, bool write)

{

    const MemoryRegionPortio *mrp;

    for (mrp = mr->ops->old_portio; mrp->size; ++mrp) {

        if (offset >= mrp->offset && offset < mrp->offset + mrp->len

            && width == mrp->size

            && (write ? (bool)mrp->write : (bool)mrp->read)) {

            return mrp;

        }

    }

    return NULL;

}

static void memory_region_iorange_read(IORange *iorange,

                                       uint64_t offset,

                                       unsigned width,

                                       uint64_t *data)

{

    MemoryRegionIORange *mrio

        = container_of(iorange, MemoryRegionIORange, iorange);

    MemoryRegion *mr = mrio->mr;

    offset += mrio->offset;

    if (mr->ops->old_portio) {

        const MemoryRegionPortio *mrp = find_portio(mr, offset - mrio->offset,

                                                    width, false);

        *data = ((uint64_t)1 << (width * 8)) - 1;

        if (mrp) {

            *data = mrp->read(mr->opaque, offset);

        } else if (width == 2) {

            mrp = find_portio(mr, offset - mrio->offset, 1, false);

            assert(mrp);

            *data = mrp->read(mr->opaque, offset) |

                    (mrp->read(mr->opaque, offset + 1) << 8);

        }

        return;

    }

    *data = 0;

    access_with_adjusted_size(offset, data, width,

                              mr->ops->impl.min_access_size,

                              mr->ops->impl.max_access_size,

                              memory_region_read_accessor, mr);

}

static void memory_region_iorange_write(IORange *iorange,

                                        uint64_t offset,

                                        unsigned width,

                                        uint64_t data)

{

    MemoryRegionIORange *mrio

        = container_of(iorange, MemoryRegionIORange, iorange);

    MemoryRegion *mr = mrio->mr;

    offset += mrio->offset;

    if (mr->ops->old_portio) {

        const MemoryRegionPortio *mrp = find_portio(mr, offset - mrio->offset,

                                                    width, true);

        if (mrp) {

            mrp->write(mr->opaque, offset, data);

        } else if (width == 2) {

            mrp = find_portio(mr, offset - mrio->offset, 1, false);

            assert(mrp);

            mrp->write(mr->opaque, offset, data & 0xff);

            mrp->write(mr->opaque, offset + 1, data >> 8);

        }

        return;

    }

    access_with_adjusted_size(offset, &data, width,

                              mr->ops->impl.min_access_size,

                              mr->ops->impl.max_access_size,

                              memory_region_write_accessor, mr);

}

static void memory_region_iorange_destructor(IORange *iorange)

{

    g_free(container_of(iorange, MemoryRegionIORange, iorange));

}

const IORangeOps memory_region_iorange_ops = {

    .read = memory_region_iorange_read,

    .write = memory_region_iorange_write,

    .destructor = memory_region_iorange_destructor,

};

static AddressSpace address_space_io;

static AddressSpace *memory_region_to_address_space(MemoryRegion *mr)

{

    while (mr->parent) {

        mr = mr->parent;

    }

    if (mr == address_space_memory.root) {

        return &address_space_memory;

    }

    if (mr == address_space_io.root) {

        return &address_space_io;

    }

    abort();

}

/* Render a memory region into the global view.  Ranges in @view obscure

 * ranges in @mr.

 */

static void render_memory_region(FlatView *view,

                                 MemoryRegion *mr,

                                 Int128 base,

                                 AddrRange clip,

                                 bool readonly)

{

    MemoryRegion *subregion;

    unsigned i;

    target_phys_addr_t offset_in_region;

    Int128 remain;

    Int128 now;

    FlatRange fr;

    AddrRange tmp;

    if (!mr->enabled) {

        return;

    }

    int128_addto(&base, int128_make64(mr->addr));

    readonly |= mr->readonly;

    tmp = addrrange_make(base, mr->size);

    if (!addrrange_intersects(tmp, clip)) {

        return;

    }

    clip = addrrange_intersection(tmp, clip);

    if (mr->alias) {

        int128_subfrom(&base, int128_make64(mr->alias->addr));

        int128_subfrom(&base, int128_make64(mr->alias_offset));

        render_memory_region(view, mr->alias, base, clip, readonly);

        return;

    }

    /* Render subregions in priority order. */

    QTAILQ_FOREACH(subregion, &mr->subregions, subregions_link) {

        render_memory_region(view, subregion, base, clip, readonly);

    }

    if (!mr->terminates) {

        return;

    }

    offset_in_region = int128_get64(int128_sub(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 && int128_nz(remain); ++i) {

        if (int128_ge(base, addrrange_end(view->ranges[i].addr))) {

            continue;

        }

        if (int128_lt(base, view->ranges[i].addr.start)) {

            now = int128_min(remain,

                             int128_sub(view->ranges[i].addr.start, base));

            fr.mr = mr;

            fr.offset_in_region = offset_in_region;

            fr.addr = addrrange_make(base, now);

            fr.dirty_log_mask = mr->dirty_log_mask;

            fr.readable = mr->readable;

            fr.readonly = readonly;

            flatview_insert(view, i, &fr);

            ++i;

            int128_addto(&base, now);

            offset_in_region += int128_get64(now);

            int128_subfrom(&remain, now);

        }

        if (int128_eq(base, view->ranges[i].addr.start)) {

            now = int128_min(remain, view->ranges[i].addr.size);

            int128_addto(&base, now);

            offset_in_region += int128_get64(now);

            int128_subfrom(&remain, now);

        }

    }

    if (int128_nz(remain)) {

        fr.mr = mr;

        fr.offset_in_region = offset_in_region;

        fr.addr = addrrange_make(base, remain);

        fr.dirty_log_mask = mr->dirty_log_mask;

        fr.readable = mr->readable;

        fr.readonly = readonly;

        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, int128_zero(),

                         addrrange_make(int128_zero(), int128_2_64()), false);

    flatview_simplify(&view);

    return view;

}

static void address_space_add_del_ioeventfds(AddressSpace *as,

                                             MemoryRegionIoeventfd *fds_new,

                                             unsigned fds_new_nb,

                                             MemoryRegionIoeventfd *fds_old,

                                             unsigned fds_old_nb)

{

    unsigned iold, inew;

    MemoryRegionIoeventfd *fd;

    MemoryRegionSection section;

    /* Generate a symmetric difference of the old and new fd sets, adding

     * and deleting as necessary.

     */

    iold = inew = 0;

    while (iold < fds_old_nb || inew < fds_new_nb) {

        if (iold < fds_old_nb

            && (inew == fds_new_nb

                || memory_region_ioeventfd_before(fds_old[iold],

                                                  fds_new[inew]))) {

            fd = &fds_old[iold];

            section = (MemoryRegionSection) {

                .address_space = as->root,

                .offset_within_address_space = int128_get64(fd->addr.start),

                .size = int128_get64(fd->addr.size),

            };

            MEMORY_LISTENER_CALL(eventfd_del, Forward, &section,

                                 fd->match_data, fd->data, fd->e);

            ++iold;

        } else if (inew < fds_new_nb

                   && (iold == fds_old_nb

                       || memory_region_ioeventfd_before(fds_new[inew],

                                                         fds_old[iold]))) {

            fd = &fds_new[inew];

            section = (MemoryRegionSection) {

                .address_space = as->root,

                .offset_within_address_space = int128_get64(fd->addr.start),

                .size = int128_get64(fd->addr.size),

            };

            MEMORY_LISTENER_CALL(eventfd_add, Reverse, &section,

                                 fd->match_data, fd->data, fd->e);

            ++inew;

        } else {

            ++iold;

            ++inew;

        }

    }

}

static void address_space_update_ioeventfds(AddressSpace *as)

{

    FlatRange *fr;

    unsigned ioeventfd_nb = 0;

    MemoryRegionIoeventfd *ioeventfds = NULL;

    AddrRange tmp;

    unsigned i;

    FOR_EACH_FLAT_RANGE(fr, &as->current_map) {

        for (i = 0; i < fr->mr->ioeventfd_nb; ++i) {

            tmp = addrrange_shift(fr->mr->ioeventfds[i].addr,

                                  int128_sub(fr->addr.start,

                                             int128_make64(fr->offset_in_region)));

            if (addrrange_intersects(fr->addr, tmp)) {

                ++ioeventfd_nb;

                ioeventfds = g_realloc(ioeventfds,

                                          ioeventfd_nb * sizeof(*ioeventfds));

                ioeventfds[ioeventfd_nb-1] = fr->mr->ioeventfds[i];

                ioeventfds[ioeventfd_nb-1].addr = tmp;

            }

        }

    }

    address_space_add_del_ioeventfds(as, ioeventfds, ioeventfd_nb,

                                     as->ioeventfds, as->ioeventfd_nb);

    g_free(as->ioeventfds);

    as->ioeventfds = ioeventfds;

    as->ioeventfd_nb = ioeventfd_nb;

}

static void address_space_update_topology_pass(AddressSpace *as,

                                               FlatView old_view,

                                               FlatView new_view,

                                               bool adding)

{

    unsigned iold, inew;

    FlatRange *frold, *frnew;

    /* 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

                || int128_lt(frold->addr.start, frnew->addr.start)

                || (int128_eq(frold->addr.start, frnew->addr.start)

                    && !flatrange_equal(frold, frnew)))) {

            /* In old, but (not in new, or in new but attributes changed). */

            if (!adding) {

                MEMORY_LISTENER_UPDATE_REGION(frold, as, Reverse, region_del);

            }

            ++iold;

        } else if (frold && frnew && flatrange_equal(frold, frnew)) {

            /* In both (logging may have changed) */

            if (adding) {

                MEMORY_LISTENER_UPDATE_REGION(frnew, as, Forward, region_nop);

                if (frold->dirty_log_mask && !frnew->dirty_log_mask) {

                    MEMORY_LISTENER_UPDATE_REGION(frnew, as, Reverse, log_stop);

                } else if (frnew->dirty_log_mask && !frold->dirty_log_mask) {

                    MEMORY_LISTENER_UPDATE_REGION(frnew, as, Forward, log_start);

                }

            }

            ++iold;

            ++inew;

        } else {

            /* In new */

            if (adding) {

                MEMORY_LISTENER_UPDATE_REGION(frnew, as, Forward, region_add);

            }

            ++inew;

        }

    }

}

static void address_space_update_topology(AddressSpace *as)

{

    FlatView old_view = as->current_map;

    FlatView new_view = generate_memory_topology(as->root);

    address_space_update_topology_pass(as, old_view, new_view, false);

    address_space_update_topology_pass(as, old_view, new_view, true);

    as->current_map = new_view;

    flatview_destroy(&old_view);

    address_space_update_ioeventfds(as);

}

static void memory_region_update_topology(MemoryRegion *mr)

{

    if (memory_region_transaction_depth) {

        memory_region_update_pending |= !mr || mr->enabled;

        return;

    }

    if (mr && !mr->enabled) {

        return;

    }

    MEMORY_LISTENER_CALL_GLOBAL(begin, Forward);

    if (address_space_memory.root) {

        address_space_update_topology(&address_space_memory);

    }

    if (address_space_io.root) {

        address_space_update_topology(&address_space_io);

    }

    MEMORY_LISTENER_CALL_GLOBAL(commit, Forward);

    memory_region_update_pending = false;

}

void memory_region_transaction_begin(void)

{

    ++memory_region_transaction_depth;

}

void memory_region_transaction_commit(void)

{

    assert(memory_region_transaction_depth);

    --memory_region_transaction_depth;

    if (!memory_region_transaction_depth && memory_region_update_pending) {

        memory_region_update_topology(NULL);

    }

}

static void memory_region_destructor_none(MemoryRegion *mr)

{

}

static void memory_region_destructor_ram(MemoryRegion *mr)

{

    qemu_ram_free(mr->ram_addr);

}

static void memory_region_destructor_ram_from_ptr(MemoryRegion *mr)

{

    qemu_ram_free_from_ptr(mr->ram_addr);

}

static void memory_region_destructor_iomem(MemoryRegion *mr)

{

}

static void memory_region_destructor_rom_device(MemoryRegion *mr)

{

    qemu_ram_free(mr->ram_addr & TARGET_PAGE_MASK);

}

static bool memory_region_wrong_endianness(MemoryRegion *mr)

{

#ifdef TARGET_WORDS_BIGENDIAN

    return mr->ops->endianness == DEVICE_LITTLE_ENDIAN;

#else

    return mr->ops->endianness == DEVICE_BIG_ENDIAN;

#endif

}

void memory_region_init(MemoryRegion *mr,

                        const char *name,

                        uint64_t size)

{

    mr->ops = NULL;

    mr->parent = NULL;

    mr->size = int128_make64(size);

    if (size == UINT64_MAX) {

        mr->size = int128_2_64();

    }

    mr->addr = 0;

    mr->subpage = false;

    mr->enabled = true;

    mr->terminates = false;

    mr->ram = false;

    mr->readable = true;

    mr->readonly = false;

    mr->rom_device = false;

    mr->destructor = memory_region_destructor_none;

    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 = g_strdup(name);

    mr->dirty_log_mask = 0;

    mr->ioeventfd_nb = 0;

    mr->ioeventfds = NULL;

}

static bool memory_region_access_valid(MemoryRegion *mr,

                                       target_phys_addr_t addr,

                                       unsigned size,

                                       bool is_write)

{

    if (mr->ops->valid.accepts

        && !mr->ops->valid.accepts(mr->opaque, addr, size, is_write)) {

        return false;

    }

    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 uint64_t memory_region_dispatch_read1(MemoryRegion *mr,

                                             target_phys_addr_t addr,

                                             unsigned size)

{

    uint64_t data = 0;

    if (!memory_region_access_valid(mr, addr, size, false)) {

        return -1U; /* FIXME: better signalling */

    }

    if (!mr->ops->read) {

        return mr->ops->old_mmio.read[bitops_ffsl(size)](mr->opaque, addr);

    }

    /* FIXME: support unaligned access */

    access_with_adjusted_size(addr, &data, size,

                              mr->ops->impl.min_access_size,

                              mr->ops->impl.max_access_size,

                              memory_region_read_accessor, mr);

    return data;

}

static void adjust_endianness(MemoryRegion *mr, uint64_t *data, unsigned size)

{

    if (memory_region_wrong_endianness(mr)) {

        switch (size) {

        case 1:

            break;

        case 2:

            *data = bswap16(*data);

            break;

        case 4:

            *data = bswap32(*data);

            break;

        default:

            abort();

        }

    }

}

static uint64_t memory_region_dispatch_read(MemoryRegion *mr,

                                            target_phys_addr_t addr,

                                            unsigned size)

{

    uint64_t ret;

    ret = memory_region_dispatch_read1(mr, addr, size);

    adjust_endianness(mr, &ret, size);

    return ret;

}

static void memory_region_dispatch_write(MemoryRegion *mr,

                                         target_phys_addr_t addr,

                                         uint64_t data,

                                         unsigned size)

{

    if (!memory_region_access_valid(mr, addr, size, true)) {

        return; /* FIXME: better signalling */

    }

    adjust_endianness(mr, &data, size);

    if (!mr->ops->write) {

        mr->ops->old_mmio.write[bitops_ffsl(size)](mr->opaque, addr, data);

        return;

    }

    /* FIXME: support unaligned access */

    access_with_adjusted_size(addr, &data, size,

                              mr->ops->impl.min_access_size,

                              mr->ops->impl.max_access_size,

                              memory_region_write_accessor, mr);