Re: [Qemu-block] [PATCH 12/17] migration: add postcopy migration of dirty bitmaps

[Dr. David Alan Gilbert]

* Vladimir Sementsov-Ogievskiy (address@hidden) wrote:
> 24.02.2017 16:26, Dr. David Alan Gilbert wrote:
> > * Vladimir Sementsov-Ogievskiy (address@hidden) wrote:
> > > Postcopy migration of dirty bitmaps. Only named dirty bitmaps,
> > > associated with root nodes and non-root named nodes are migrated.
> > > 
> > > If destination qemu is already containing a dirty bitmap with the same 
> > > name
> > > as a migrated bitmap (for the same node), than, if their granularities are
> > > the same the migration will be done, otherwise the error will be 
> > > generated.
> > > 
> > > If destination qemu doesn't contain such bitmap it will be created.
> > > 
> > > Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> > > ---
> > >   include/migration/block.h      |   1 +
> > >   include/migration/migration.h  |   4 +
> > >   migration/Makefile.objs        |   2 +-
> > >   migration/block-dirty-bitmap.c | 679 
> > > +++++++++++++++++++++++++++++++++++++++++
> > >   migration/migration.c          |   3 +
> > >   migration/savevm.c             |   2 +
> > >   migration/trace-events         |  14 +
> > >   vl.c                           |   1 +
> > >   8 files changed, 705 insertions(+), 1 deletion(-)
> > >   create mode 100644 migration/block-dirty-bitmap.c
> > > 
> > > diff --git a/include/migration/block.h b/include/migration/block.h
> > > index 41a1ac8..8333c43 100644
> > > --- a/include/migration/block.h
> > > +++ b/include/migration/block.h
> > > @@ -14,6 +14,7 @@
> > >   #ifndef MIGRATION_BLOCK_H
> > >   #define MIGRATION_BLOCK_H
> > > +void dirty_bitmap_mig_init(void);
> > >   void blk_mig_init(void);
> > >   int blk_mig_active(void);
> > >   uint64_t blk_mig_bytes_transferred(void);
> > > diff --git a/include/migration/migration.h b/include/migration/migration.h
> > > index 46645f4..03a4993 100644
> > > --- a/include/migration/migration.h
> > > +++ b/include/migration/migration.h
> > > @@ -371,4 +371,8 @@ int ram_save_queue_pages(MigrationState *ms, const 
> > > char *rbname,
> > >   PostcopyState postcopy_state_get(void);
> > >   /* Set the state and return the old state */
> > >   PostcopyState postcopy_state_set(PostcopyState new_state);
> > > +
> > > +void dirty_bitmap_mig_before_vm_start(void);
> > > +void init_dirty_bitmap_incoming_migration(void);
> > > +
> > >   #endif
> > > diff --git a/migration/Makefile.objs b/migration/Makefile.objs
> > > index 480dd49..fa3bf6a 100644
> > > --- a/migration/Makefile.objs
> > > +++ b/migration/Makefile.objs
> > > @@ -9,5 +9,5 @@ common-obj-y += qjson.o
> > >   common-obj-$(CONFIG_RDMA) += rdma.o
> > > -common-obj-y += block.o
> > > +common-obj-y += block.o block-dirty-bitmap.o
> > > diff --git a/migration/block-dirty-bitmap.c 
> > > b/migration/block-dirty-bitmap.c
> > > new file mode 100644
> > > index 0000000..28e3732
> > > --- /dev/null
> > > +++ b/migration/block-dirty-bitmap.c
> > > @@ -0,0 +1,679 @@
> > > +/*
> > > + * Block dirty bitmap postcopy migration
> > > + *
> > > + * Copyright IBM, Corp. 2009
> > > + * Copyright (C) 2016 Parallels IP Holdings GmbH. All rights reserved.
> > > + *
> > > + * Authors:
> > > + *  Liran Schour   <address@hidden>
> > > + *  Vladimir Sementsov-Ogievskiy <address@hidden>
> > > + *
> > > + * This work is licensed under the terms of the GNU GPL, version 2.  See
> > > + * the COPYING file in the top-level directory.
> > > + * This file is derived from migration/block.c, so it's author and IBM 
> > > copyright
> > > + * are here, although content is quite different.
> > > + *
> > > + * Contributions after 2012-01-13 are licensed under the terms of the
> > > + * GNU GPL, version 2 or (at your option) any later version.
> > > + *
> > > + *                                ***
> > > + *
> > > + * Here postcopy migration of dirty bitmaps is realized. Only named dirty
> > > + * bitmaps, associated with root nodes and non-root named nodes are 
> > > migrated.
> > > + *
> > > + * If destination qemu is already containing a dirty bitmap with the 
> > > same name
> > > + * as a migrated bitmap (for the same node), then, if their 
> > > granularities are
> > > + * the same the migration will be done, otherwise the error will be 
> > > generated.
> > > + *
> > > + * If destination qemu doesn't contain such bitmap it will be created.
> > > + *
> > > + * format of migration:
> > > + *
> > > + * # Header (shared for different chunk types)
> > > + * 1, 2 or 4 bytes: flags (see qemu_{put,put}_flags)
> > > + * [ 1 byte: node name size ] \  flags & DEVICE_NAME
> > > + * [ n bytes: node name     ] /
> > > + * [ 1 byte: bitmap name size ] \  flags & BITMAP_NAME
> > > + * [ n bytes: bitmap name     ] /
> > > + *
> > > + * # Start of bitmap migration (flags & START)
> > > + * header
> > > + * be64: granularity
> > > + * 1 byte: bitmap enabled flag
> > > + *
> > > + * # Complete of bitmap migration (flags & COMPLETE)
> > > + * header
> > > + *
> > > + * # Data chunk of bitmap migration
> > > + * header
> > > + * be64: start sector
> > > + * be32: number of sectors
> > > + * [ be64: buffer size  ] \ ! (flags & ZEROES)
> > > + * [ n bytes: buffer    ] /
> > > + *
> > > + * The last chunk in stream should contain flags & EOS. The chunk may 
> > > skip
> > > + * device and/or bitmap names, assuming them to be the same with the 
> > > previous
> > > + * chunk.
> > > + */
> > > +
> > > +#include "qemu/osdep.h"
> > > +#include "block/block.h"
> > > +#include "block/block_int.h"
> > > +#include "sysemu/block-backend.h"
> > > +#include "qemu/main-loop.h"
> > > +#include "qemu/error-report.h"
> > > +#include "migration/block.h"
> > > +#include "migration/migration.h"
> > > +#include "qemu/hbitmap.h"
> > > +#include "sysemu/sysemu.h"
> > > +#include "qemu/cutils.h"
> > > +#include "qapi/error.h"
> > > +#include "trace.h"
> > > +#include <assert.h>
> > > +
> > > +#define CHUNK_SIZE     (1 << 10)
> > > +
> > > +/* Flags occupy from one to four bytes. In all but one the 7-th 
> > > (EXTRA_FLAGS)
> > > + * bit should be set. */
> > > +#define DIRTY_BITMAP_MIG_FLAG_EOS           0x01
> > > +#define DIRTY_BITMAP_MIG_FLAG_ZEROES        0x02
> > > +#define DIRTY_BITMAP_MIG_FLAG_BITMAP_NAME   0x04
> > > +#define DIRTY_BITMAP_MIG_FLAG_DEVICE_NAME   0x08
> > > +#define DIRTY_BITMAP_MIG_FLAG_START         0x10
> > > +#define DIRTY_BITMAP_MIG_FLAG_COMPLETE      0x20
> > > +#define DIRTY_BITMAP_MIG_FLAG_BITS          0x40
> > > +
> > > +#define DIRTY_BITMAP_MIG_EXTRA_FLAGS        0x80
> > > +#define DIRTY_BITMAP_MIG_FLAGS_SIZE_16      0x8000
> > > +#define DIRTY_BITMAP_MIG_FLAGS_SIZE_32      0x8080
> > > +
> > > +#define DEBUG_DIRTY_BITMAP_MIGRATION 0
> > > +
> > > +typedef struct DirtyBitmapMigBitmapState {
> > > +    /* Written during setup phase. */
> > > +    BlockDriverState *bs;
> > > +    const char *node_name;
> > > +    BdrvDirtyBitmap *bitmap;
> > > +    uint64_t total_sectors;
> > > +    uint64_t sectors_per_chunk;
> > > +    QSIMPLEQ_ENTRY(DirtyBitmapMigBitmapState) entry;
> > > +
> > > +    /* For bulk phase. */
> > > +    bool bulk_completed;
> > > +    uint64_t cur_sector;
> > > +} DirtyBitmapMigBitmapState;
> > > +
> > > +typedef struct DirtyBitmapMigState {
> > > +    QSIMPLEQ_HEAD(dbms_list, DirtyBitmapMigBitmapState) dbms_list;
> > > +
> > > +    bool bulk_completed;
> > > +
> > > +    /* for send_bitmap_bits() */
> > > +    BlockDriverState *prev_bs;
> > > +    BdrvDirtyBitmap *prev_bitmap;
> > > +} DirtyBitmapMigState;
> > > +
> > > +typedef struct DirtyBitmapLoadState {
> > > +    uint32_t flags;
> > > +    char node_name[256];
> > > +    char bitmap_name[256];
> > > +    BlockDriverState *bs;
> > > +    BdrvDirtyBitmap *bitmap;
> > > +} DirtyBitmapLoadState;
> > > +
> > > +static DirtyBitmapMigState dirty_bitmap_mig_state;
> > > +
> > > +typedef struct DirtyBitmapLoadBitmapState {
> > > +    BlockDriverState *bs;
> > > +    BdrvDirtyBitmap *bitmap;
> > > +    bool migrated;
> > > +} DirtyBitmapLoadBitmapState;
> > > +static GSList *enabled_bitmaps;
> > > +QemuMutex finish_lock;
> > > +
> > > +void init_dirty_bitmap_incoming_migration(void)
> > > +{
> > > +    qemu_mutex_init(&finish_lock);
> > > +}
> > > +
> > > +static uint32_t qemu_get_bitmap_flags(QEMUFile *f)
> > > +{
> > > +    uint8_t flags = qemu_get_byte(f);
> > > +    if (flags & DIRTY_BITMAP_MIG_EXTRA_FLAGS) {
> > > +        flags = flags << 8 | qemu_get_byte(f);
> > > +        if (flags & DIRTY_BITMAP_MIG_EXTRA_FLAGS) {
> > > +            flags = flags << 16 | qemu_get_be16(f);
> > > +        }
> > > +    }
> > > +
> > > +    return flags;
> > > +}
> > > +
> > > +static void qemu_put_bitmap_flags(QEMUFile *f, uint32_t flags)
> > > +{
> > > +    if (!(flags & 0xffffff00)) {
> > > +        qemu_put_byte(f, flags);
> > > +        return;
> > > +    }
> > > +
> > > +    if (!(flags & 0xffff0000)) {
> > > +        qemu_put_be16(f, flags | DIRTY_BITMAP_MIG_FLAGS_SIZE_16);
> > > +        return;
> > > +    }
> > > +
> > > +    qemu_put_be32(f, flags | DIRTY_BITMAP_MIG_FLAGS_SIZE_32);
> > Is this stuff worth the hastle? It would seem easier just to send
> > the 32bits each time;  the overhead doesn't seem to be much except
> > in the case where you send minimum size chunks a lot.
> 
> I've started with one byte of flags (I don't need more) and I've implemented
> this after proposal by John Snow:
> > I might recommend reserving the last bit of the second byte to be a flag
> > such as DIRTY_BITMAP_EXTRA_FLAGS that indicates the presence of
> > additional byte(s) of flags, to be determined later, if we ever need
> > them, but two bytes for now should be sufficient.
> 
> And I think it is not bad. Code is a bit more complex, yes, but why should
> we send 4 bytes with every chunk when (very likely) we will never use more
> than one?

Yes if it's very rare and a useful % of the size then that makes sense; just
don't worry about squeezing every byte out of it if it's a tiny %.
And yes, keeping one flag set aside for 'and there's more' is good.

Dave

> > 
> > Dave
> > 
> > > +}
> > > +
> > > +static void send_bitmap_header(QEMUFile *f, DirtyBitmapMigBitmapState 
> > > *dbms,
> > > +                               uint32_t additional_flags)
> > > +{
> > > +    BlockDriverState *bs = dbms->bs;
> > > +    BdrvDirtyBitmap *bitmap = dbms->bitmap;
> > > +    uint32_t flags = additional_flags;
> > > +    trace_send_bitmap_header_enter();
> > > +
> > > +    if (bs != dirty_bitmap_mig_state.prev_bs) {
> > > +        dirty_bitmap_mig_state.prev_bs = bs;
> > > +        flags |= DIRTY_BITMAP_MIG_FLAG_DEVICE_NAME;
> > > +    }
> > > +
> > > +    if (bitmap != dirty_bitmap_mig_state.prev_bitmap) {
> > > +        dirty_bitmap_mig_state.prev_bitmap = bitmap;
> > > +        flags |= DIRTY_BITMAP_MIG_FLAG_BITMAP_NAME;
> > > +    }
> > > +
> > > +    qemu_put_bitmap_flags(f, flags);
> > > +
> > > +    if (flags & DIRTY_BITMAP_MIG_FLAG_DEVICE_NAME) {
> > > +        qemu_put_counted_string(f, dbms->node_name);
> > > +    }
> > > +
> > > +    if (flags & DIRTY_BITMAP_MIG_FLAG_BITMAP_NAME) {
> > > +        qemu_put_counted_string(f, bdrv_dirty_bitmap_name(bitmap));
> > > +    }
> > > +}
> > > +
> > > +static void send_bitmap_start(QEMUFile *f, DirtyBitmapMigBitmapState 
> > > *dbms)
> > > +{
> > > +    send_bitmap_header(f, dbms, DIRTY_BITMAP_MIG_FLAG_START);
> > > +    qemu_put_be32(f, bdrv_dirty_bitmap_granularity(dbms->bitmap));
> > > +    qemu_put_byte(f, bdrv_dirty_bitmap_enabled(dbms->bitmap));
> > > +}
> > > +
> > > +static void send_bitmap_complete(QEMUFile *f, DirtyBitmapMigBitmapState 
> > > *dbms)
> > > +{
> > > +    send_bitmap_header(f, dbms, DIRTY_BITMAP_MIG_FLAG_COMPLETE);
> > > +}
> > > +
> > > +static void send_bitmap_bits(QEMUFile *f, DirtyBitmapMigBitmapState 
> > > *dbms,
> > > +                             uint64_t start_sector, uint32_t nr_sectors)
> > > +{
> > > +    /* align for buffer_is_zero() */
> > > +    uint64_t align = 4 * sizeof(long);
> > > +    uint64_t unaligned_size =
> > > +        bdrv_dirty_bitmap_serialization_size(dbms->bitmap,
> > > +                                             start_sector, nr_sectors);
> > > +    uint64_t buf_size = (unaligned_size + align - 1) & ~(align - 1);
> > > +    uint8_t *buf = g_malloc0(buf_size);
> > > +    uint32_t flags = DIRTY_BITMAP_MIG_FLAG_BITS;
> > > +
> > > +    bdrv_dirty_bitmap_serialize_part(dbms->bitmap, buf,
> > > +                                     start_sector, nr_sectors);
> > > +
> > > +    if (buffer_is_zero(buf, buf_size)) {
> > > +        g_free(buf);
> > > +        buf = NULL;
> > > +        flags |= DIRTY_BITMAP_MIG_FLAG_ZEROES;
> > > +    }
> > > +
> > > +    trace_send_bitmap_bits(flags, start_sector, nr_sectors, buf_size);
> > > +
> > > +    send_bitmap_header(f, dbms, flags);
> > > +
> > > +    qemu_put_be64(f, start_sector);
> > > +    qemu_put_be32(f, nr_sectors);
> > > +
> > > +    /* if a block is zero we need to flush here since the network
> > > +     * bandwidth is now a lot higher than the storage device bandwidth.
> > > +     * thus if we queue zero blocks we slow down the migration. */
> > > +    if (flags & DIRTY_BITMAP_MIG_FLAG_ZEROES) {
> > > +        qemu_fflush(f);
> > > +    } else {
> > > +        qemu_put_be64(f, buf_size);
> > > +        qemu_put_buffer(f, buf, buf_size);
> > > +    }
> > > +
> > > +    g_free(buf);
> > > +}
> > > +
> > > +
> > > +/* Called with iothread lock taken.  */
> > > +
> > > +static void init_dirty_bitmap_migration(void)
> > > +{
> > > +    BlockDriverState *bs;
> > > +    BdrvDirtyBitmap *bitmap;
> > > +    DirtyBitmapMigBitmapState *dbms;
> > > +    BdrvNextIterator it;
> > > +    uint64_t total_bytes = 0;
> > > +
> > > +    dirty_bitmap_mig_state.bulk_completed = false;
> > > +    dirty_bitmap_mig_state.prev_bs = NULL;
> > > +    dirty_bitmap_mig_state.prev_bitmap = NULL;
> > > +
> > > +    for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
> > > +        for (bitmap = bdrv_next_dirty_bitmap(bs, NULL); bitmap;
> > > +             bitmap = bdrv_next_dirty_bitmap(bs, bitmap)) {
> > > +            if (!bdrv_dirty_bitmap_name(bitmap)) {
> > > +                continue;
> > > +            }
> > > +
> > > +            if (!bdrv_get_device_or_node_name(bs)) {
> > > +                /* not named non-root node */
> > > +                continue;
> > > +            }
> > > +
> > > +            dbms = g_new0(DirtyBitmapMigBitmapState, 1);
> > > +            dbms->bs = bs;
> > > +            dbms->node_name = bdrv_get_node_name(bs);
> > > +            if (!dbms->node_name || dbms->node_name[0] == '\0') {
> > > +                dbms->node_name = bdrv_get_device_name(bs);
> > > +            }
> > > +            dbms->bitmap = bitmap;
> > > +            dbms->total_sectors = bdrv_nb_sectors(bs);
> > > +            dbms->sectors_per_chunk = CHUNK_SIZE * 8 *
> > > +                bdrv_dirty_bitmap_granularity(bitmap) >> 
> > > BDRV_SECTOR_BITS;
> > > +
> > > +            total_bytes +=
> > > +                bdrv_dirty_bitmap_serialization_size(bitmap,
> > > +                                                     0, 
> > > dbms->total_sectors);
> > > +
> > > +            QSIMPLEQ_INSERT_TAIL(&dirty_bitmap_mig_state.dbms_list,
> > > +                                 dbms, entry);
> > > +        }
> > > +    }
> > > +}
> > > +
> > > +/* Called with no lock taken.  */
> > > +static void bulk_phase_send_chunk(QEMUFile *f, DirtyBitmapMigBitmapState 
> > > *dbms)
> > > +{
> > > +    uint32_t nr_sectors = MIN(dbms->total_sectors - dbms->cur_sector,
> > > +                             dbms->sectors_per_chunk);
> > > +
> > > +    send_bitmap_bits(f, dbms, dbms->cur_sector, nr_sectors);
> > > +
> > > +    dbms->cur_sector += nr_sectors;
> > > +    if (dbms->cur_sector >= dbms->total_sectors) {
> > > +        dbms->bulk_completed = true;
> > > +    }
> > > +}
> > > +
> > > +/* Called with no lock taken.  */
> > > +static void bulk_phase(QEMUFile *f, bool limit)
> > > +{
> > > +    DirtyBitmapMigBitmapState *dbms;
> > > +
> > > +    QSIMPLEQ_FOREACH(dbms, &dirty_bitmap_mig_state.dbms_list, entry) {
> > > +        while (!dbms->bulk_completed) {
> > > +            bulk_phase_send_chunk(f, dbms);
> > > +            if (limit && qemu_file_rate_limit(f)) {
> > > +                return;
> > > +            }
> > > +        }
> > > +    }
> > > +
> > > +    dirty_bitmap_mig_state.bulk_completed = true;
> > > +}
> > > +
> > > +/* Called with iothread lock taken.  */
> > > +static void dirty_bitmap_mig_cleanup(void)
> > > +{
> > > +    DirtyBitmapMigBitmapState *dbms;
> > > +
> > > +    while ((dbms = QSIMPLEQ_FIRST(&dirty_bitmap_mig_state.dbms_list)) != 
> > > NULL) {
> > > +        QSIMPLEQ_REMOVE_HEAD(&dirty_bitmap_mig_state.dbms_list, entry);
> > > +        g_free(dbms);
> > > +    }
> > > +}
> > > +
> > > +/* for SaveVMHandlers */
> > > +static void dirty_bitmap_migration_cleanup(void *opaque)
> > > +{
> > > +    dirty_bitmap_mig_cleanup();
> > > +}
> > > +
> > > +static int dirty_bitmap_save_iterate(QEMUFile *f, void *opaque)
> > > +{
> > > +    trace_dirty_bitmap_save_iterate(
> > > +            migration_in_postcopy(migrate_get_current()));
> > > +
> > > +    if (migration_in_postcopy(migrate_get_current()) &&
> > > +        !dirty_bitmap_mig_state.bulk_completed) {
> > > +        bulk_phase(f, true);
> > > +    }
> > > +
> > > +    qemu_put_bitmap_flags(f, DIRTY_BITMAP_MIG_FLAG_EOS);
> > > +
> > > +    return dirty_bitmap_mig_state.bulk_completed;
> > > +}
> > > +
> > > +/* Called with iothread lock taken.  */
> > > +
> > > +static int dirty_bitmap_save_complete(QEMUFile *f, void *opaque)
> > > +{
> > > +    DirtyBitmapMigBitmapState *dbms;
> > > +    trace_dirty_bitmap_save_complete_enter();
> > > +
> > > +    if (!dirty_bitmap_mig_state.bulk_completed) {
> > > +        bulk_phase(f, false);
> > > +    }
> > > +
> > > +    QSIMPLEQ_FOREACH(dbms, &dirty_bitmap_mig_state.dbms_list, entry) {
> > > +        send_bitmap_complete(f, dbms);
> > > +    }
> > > +
> > > +    qemu_put_bitmap_flags(f, DIRTY_BITMAP_MIG_FLAG_EOS);
> > > +
> > > +    trace_dirty_bitmap_save_complete_finish();
> > > +
> > > +    dirty_bitmap_mig_cleanup();
> > > +    return 0;
> > > +}
> > > +
> > > +static void dirty_bitmap_save_pending(QEMUFile *f, void *opaque,
> > > +                                      uint64_t max_size,
> > > +                                      uint64_t *res_precopy_only,
> > > +                                      uint64_t *res_compatible,
> > > +                                      uint64_t *res_postcopy_only)
> > > +{
> > > +    DirtyBitmapMigBitmapState *dbms;
> > > +    uint64_t pending = 0;
> > > +
> > > +    qemu_mutex_lock_iothread();
> > > +
> > > +    QSIMPLEQ_FOREACH(dbms, &dirty_bitmap_mig_state.dbms_list, entry) {
> > > +        uint64_t gran = bdrv_dirty_bitmap_granularity(dbms->bitmap);
> > > +        uint64_t sectors = dbms->bulk_completed ? 0 :
> > > +                           dbms->total_sectors - dbms->cur_sector;
> > > +
> > > +        pending += (sectors * BDRV_SECTOR_SIZE + gran - 1) / gran;
> > > +    }
> > > +
> > > +    qemu_mutex_unlock_iothread();
> > > +
> > > +    trace_dirty_bitmap_save_pending(pending, max_size);
> > > +
> > > +    *res_postcopy_only += pending;
> > > +}
> > > +
> > > +/* First occurrence of this bitmap. It should be created if doesn't 
> > > exist */
> > > +static int dirty_bitmap_load_start(QEMUFile *f, DirtyBitmapLoadState *s)
> > > +{
> > > +    Error *local_err = NULL;
> > > +    uint32_t granularity = qemu_get_be32(f);
> > > +    bool enabled = qemu_get_byte(f);
> > > +
> > > +    if (!s->bitmap) {
> > > +        s->bitmap = bdrv_create_dirty_bitmap(s->bs, granularity,
> > > +                                             s->bitmap_name, &local_err);
> > > +        if (!s->bitmap) {
> > > +            error_report_err(local_err);
> > > +            return -EINVAL;
> > > +        }
> > > +    } else {
> > > +        uint32_t dest_granularity =
> > > +            bdrv_dirty_bitmap_granularity(s->bitmap);
> > > +        if (dest_granularity != granularity) {
> > > +            fprintf(stderr,
> > > +                    "Error: "
> > > +                    "Migrated bitmap granularity (%" PRIu32 ") "
> > > +                    "doesn't match the destination bitmap '%s' "
> > > +                    "granularity (%" PRIu32 ")\n",
> > > +                    granularity,
> > > +                    bdrv_dirty_bitmap_name(s->bitmap),
> > > +                    dest_granularity);
> > > +            return -EINVAL;
> > > +        }
> > > +    }
> > > +
> > > +    bdrv_disable_dirty_bitmap(s->bitmap);
> > > +    if (enabled) {
> > > +        DirtyBitmapLoadBitmapState *b;
> > > +
> > > +        bdrv_dirty_bitmap_create_successor(s->bs, s->bitmap, &local_err);
> > > +        if (local_err) {
> > > +            error_report_err(local_err);
> > > +            return -EINVAL;
> > > +        }
> > > +
> > > +        b = g_new(DirtyBitmapLoadBitmapState, 1);
> > > +        b->bs = s->bs;
> > > +        b->bitmap = s->bitmap;
> > > +        b->migrated = false;
> > > +        enabled_bitmaps = g_slist_prepend(enabled_bitmaps, b);
> > > +    }
> > > +
> > > +    return 0;
> > > +}
> > > +
> > > +void dirty_bitmap_mig_before_vm_start(void)
> > > +{
> > > +    GSList *item;
> > > +
> > > +    qemu_mutex_lock(&finish_lock);
> > > +
> > > +    for (item = enabled_bitmaps; item; item = g_slist_next(item)) {
> > > +        DirtyBitmapLoadBitmapState *b = item->data;
> > > +
> > > +        if (b->migrated) {
> > > +            bdrv_enable_dirty_bitmap(b->bitmap);
> > > +        } else {
> > > +            bdrv_dirty_bitmap_enable_successor(b->bitmap);
> > > +        }
> > > +
> > > +        g_free(b);
> > > +    }
> > > +
> > > +    g_slist_free(enabled_bitmaps);
> > > +    enabled_bitmaps = NULL;
> > > +
> > > +    qemu_mutex_unlock(&finish_lock);
> > > +}
> > > +
> > > +static void dirty_bitmap_load_complete(QEMUFile *f, DirtyBitmapLoadState 
> > > *s)
> > > +{
> > > +    GSList *item;
> > > +    trace_dirty_bitmap_load_complete();
> > > +    bdrv_dirty_bitmap_deserialize_finish(s->bitmap);
> > > +
> > > +    qemu_mutex_lock(&finish_lock);
> > > +
> > > +    for (item = enabled_bitmaps; item; item = g_slist_next(item)) {
> > > +        DirtyBitmapLoadBitmapState *b = item->data;
> > > +
> > > +        if (b->bitmap == s->bitmap) {
> > > +            b->migrated = true;
> > > +        }
> > > +    }
> > > +
> > > +    if (bdrv_dirty_bitmap_frozen(s->bitmap)) {
> > > +        if (enabled_bitmaps == NULL) {
> > > +            /* in postcopy */
> > > +            AioContext *aio_context = bdrv_get_aio_context(s->bs);
> > > +            aio_context_acquire(aio_context);
> > > +
> > > +            bdrv_reclaim_dirty_bitmap(s->bs, s->bitmap, &error_abort);
> > > +            bdrv_enable_dirty_bitmap(s->bitmap);
> > > +
> > > +            aio_context_release(aio_context);
> > > +        } else {
> > > +            /* target not started, successor is empty */
> > > +            bdrv_dirty_bitmap_release_successor(s->bs, s->bitmap);
> > > +        }
> > > +    }
> > > +
> > > +    qemu_mutex_unlock(&finish_lock);
> > > +}
> > > +
> > > +static int dirty_bitmap_load_bits(QEMUFile *f, DirtyBitmapLoadState *s)
> > > +{
> > > +    uint64_t first_sector = qemu_get_be64(f);
> > > +    uint32_t nr_sectors = qemu_get_be32(f);
> > > +    trace_dirty_bitmap_load_bits_enter(first_sector, nr_sectors);
> > > +
> > > +    if (s->flags & DIRTY_BITMAP_MIG_FLAG_ZEROES) {
> > > +        trace_dirty_bitmap_load_bits_zeroes();
> > > +        bdrv_dirty_bitmap_deserialize_zeroes(s->bitmap, first_sector,
> > > +                                             nr_sectors, false);
> > > +    } else {
> > > +        uint8_t *buf;
> > > +        uint64_t buf_size = qemu_get_be64(f);
> > > +        uint64_t needed_size =
> > > +            bdrv_dirty_bitmap_serialization_size(s->bitmap,
> > > +                                                 first_sector, 
> > > nr_sectors);
> > > +
> > > +        if (needed_size > buf_size) {
> > > +            fprintf(stderr,
> > > +                    "Error: Migrated bitmap granularity doesn't "
> > > +                    "match the destination bitmap '%s' granularity\n",
> > > +                    bdrv_dirty_bitmap_name(s->bitmap));
> > > +            return -EINVAL;
> > > +        }
> > > +
> > > +        buf = g_malloc(buf_size);
> > > +        qemu_get_buffer(f, buf, buf_size);
> > > +        bdrv_dirty_bitmap_deserialize_part(s->bitmap, buf,
> > > +                                           first_sector,
> > > +                                           nr_sectors, false);
> > > +        g_free(buf);
> > > +    }
> > > +
> > > +    return 0;
> > > +}
> > > +
> > > +static int dirty_bitmap_load_header(QEMUFile *f, DirtyBitmapLoadState *s)
> > > +{
> > > +    Error *local_err = NULL;
> > > +    s->flags = qemu_get_bitmap_flags(f);
> > > +    trace_dirty_bitmap_load_header(s->flags);
> > > +
> > > +    if (s->flags & DIRTY_BITMAP_MIG_FLAG_DEVICE_NAME) {
> > > +        if (!qemu_get_counted_string(f, s->node_name)) {
> > > +            fprintf(stderr, "Unable to read node name string\n");
> > > +            return -EINVAL;
> > > +        }
> > > +        s->bs = bdrv_lookup_bs(s->node_name, s->node_name, &local_err);
> > > +        if (!s->bs) {
> > > +            error_report("%s", error_get_pretty(local_err));
> > > +            error_free(local_err);
> > > +            return -EINVAL;
> > > +        }
> > > +    } else if (!s->bs) {
> > > +        fprintf(stderr, "Error: block device name is not set\n");
> > > +        return -EINVAL;
> > > +    }
> > > +
> > > +    if (s->flags & DIRTY_BITMAP_MIG_FLAG_BITMAP_NAME) {
> > > +        if (!qemu_get_counted_string(f, s->bitmap_name)) {
> > > +            fprintf(stderr, "Unable to read node name string\n");
> > > +            return -EINVAL;
> > > +        }
> > > +        s->bitmap = bdrv_find_dirty_bitmap(s->bs, s->bitmap_name);
> > > +
> > > +        /* bitmap may be NULL here, it wouldn't be an error if it is the
> > > +         * first occurrence of the bitmap */
> > > +        if (!s->bitmap && !(s->flags & DIRTY_BITMAP_MIG_FLAG_START)) {
> > > +            fprintf(stderr, "Error: unknown dirty bitmap "
> > > +                    "'%s' for block device '%s'\n",
> > > +                    s->bitmap_name, s->node_name);
> > > +            return -EINVAL;
> > > +        }
> > > +    } else if (!s->bitmap) {
> > > +        fprintf(stderr, "Error: block device name is not set\n");
> > > +        return -EINVAL;
> > > +    }
> > > +
> > > +    return 0;
> > > +}
> > > +
> > > +static int dirty_bitmap_load(QEMUFile *f, void *opaque, int version_id)
> > > +{
> > > +    static DirtyBitmapLoadState s;
> > > +
> > > +    int ret = 0;
> > > +
> > > +    trace_dirty_bitmap_load_enter();
> > > +
> > > +    do {
> > > +        dirty_bitmap_load_header(f, &s);
> > > +
> > > +        if (s.flags & DIRTY_BITMAP_MIG_FLAG_START) {
> > > +            ret = dirty_bitmap_load_start(f, &s);
> > > +        } else if (s.flags & DIRTY_BITMAP_MIG_FLAG_COMPLETE) {
> > > +            dirty_bitmap_load_complete(f, &s);
> > > +        } else if (s.flags & DIRTY_BITMAP_MIG_FLAG_BITS) {
> > > +            ret = dirty_bitmap_load_bits(f, &s);
> > > +        }
> > > +
> > > +        if (!ret) {
> > > +            ret = qemu_file_get_error(f);
> > > +        }
> > > +
> > > +        if (ret) {
> > > +            return ret;
> > > +        }
> > > +    } while (!(s.flags & DIRTY_BITMAP_MIG_FLAG_EOS));
> > > +
> > > +    trace_dirty_bitmap_load_success();
> > > +    return 0;
> > > +}
> > > +
> > > +static int dirty_bitmap_save_setup(QEMUFile *f, void *opaque)
> > > +{
> > > +    DirtyBitmapMigBitmapState *dbms = NULL;
> > > +    init_dirty_bitmap_migration();
> > > +
> > > +    QSIMPLEQ_FOREACH(dbms, &dirty_bitmap_mig_state.dbms_list, entry) {
> > > +        send_bitmap_start(f, dbms);
> > > +    }
> > > +    qemu_put_bitmap_flags(f, DIRTY_BITMAP_MIG_FLAG_EOS);
> > > +
> > > +    return 0;
> > > +}
> > > +
> > > +static bool dirty_bitmap_is_active(void *opaque)
> > > +{
> > > +    return migrate_dirty_bitmaps();
> > > +}
> > > +
> > > +static bool dirty_bitmap_is_active_iterate(void *opaque)
> > > +{
> > > +    return dirty_bitmap_is_active(opaque) && !runstate_is_running();
> > > +}
> > > +
> > > +static bool dirty_bitmap_has_postcopy(void *opaque)
> > > +{
> > > +    return true;
> > > +}
> > > +
> > > +static SaveVMHandlers savevm_dirty_bitmap_handlers = {
> > > +    .save_live_setup = dirty_bitmap_save_setup,
> > > +    .save_live_complete_postcopy = dirty_bitmap_save_complete,
> > > +    .save_live_complete_precopy = dirty_bitmap_save_complete,
> > > +    .has_postcopy = dirty_bitmap_has_postcopy,
> > > +    .save_live_pending = dirty_bitmap_save_pending,
> > > +    .save_live_iterate = dirty_bitmap_save_iterate,
> > > +    .is_active_iterate = dirty_bitmap_is_active_iterate,
> > > +    .load_state = dirty_bitmap_load,
> > > +    .cleanup = dirty_bitmap_migration_cleanup,
> > > +    .is_active = dirty_bitmap_is_active,
> > > +};
> > > +
> > > +void dirty_bitmap_mig_init(void)
> > > +{
> > > +    QSIMPLEQ_INIT(&dirty_bitmap_mig_state.dbms_list);
> > > +
> > > +    register_savevm_live(NULL, "dirty-bitmap", 0, 1,
> > > +                         &savevm_dirty_bitmap_handlers,
> > > +                         &dirty_bitmap_mig_state);
> > > +}
> > > diff --git a/migration/migration.c b/migration/migration.c
> > > index 179bd04..edf5623 100644
> > > --- a/migration/migration.c
> > > +++ b/migration/migration.c
> > > @@ -122,6 +122,9 @@ MigrationIncomingState 
> > > *migration_incoming_get_current(void)
> > >           QLIST_INIT(&mis_current.loadvm_handlers);
> > >           qemu_mutex_init(&mis_current.rp_mutex);
> > >           qemu_event_init(&mis_current.main_thread_load_event, false);
> > > +
> > > +        init_dirty_bitmap_incoming_migration();
> > > +
> > >           once = true;
> > >       }
> > >       return &mis_current;
> > > diff --git a/migration/savevm.c b/migration/savevm.c
> > > index 54572ef..927a680 100644
> > > --- a/migration/savevm.c
> > > +++ b/migration/savevm.c
> > > @@ -1651,6 +1651,8 @@ static void loadvm_postcopy_handle_run_bh(void 
> > > *opaque)
> > >       trace_loadvm_postcopy_handle_run_vmstart();
> > > +    dirty_bitmap_mig_before_vm_start();
> > > +
> > >       if (autostart) {
> > >           /* Hold onto your hats, starting the CPU */
> > >           vm_start();
> > > diff --git a/migration/trace-events b/migration/trace-events
> > > index 0212929..38fca41 100644
> > > --- a/migration/trace-events
> > > +++ b/migration/trace-events
> > > @@ -222,3 +222,17 @@ colo_vm_state_change(const char *old, const char 
> > > *new) "Change '%s' => '%s'"
> > >   colo_send_message(const char *msg) "Send '%s' message"
> > >   colo_receive_message(const char *msg) "Receive '%s' message"
> > >   colo_failover_set_state(const char *new_state) "new state %s"
> > > +
> > > +# migration/block-dirty-bitmap.c
> > > +send_bitmap_header_enter(void) ""
> > > +send_bitmap_bits(uint32_t flags, uint64_t start_sector, uint32_t 
> > > nr_sectors, uint64_t data_size) "\n   flags:        %x\n   start_sector: 
> > > %" PRIu64 "\n   nr_sectors:   %" PRIu32 "\n   data_size:    %" PRIu64 "\n"
> > > +dirty_bitmap_save_iterate(int in_postcopy) "in postcopy: %d"
> > > +dirty_bitmap_save_complete_enter(void) ""
> > > +dirty_bitmap_save_complete_finish(void) ""
> > > +dirty_bitmap_save_pending(uint64_t pending, uint64_t max_size) "pending 
> > > %" PRIu64 " max: %" PRIu64
> > > +dirty_bitmap_load_complete(void) ""
> > > +dirty_bitmap_load_bits_enter(uint64_t first_sector, uint32_t nr_sectors) 
> > > "chunk: %" PRIu64 " %" PRIu32
> > > +dirty_bitmap_load_bits_zeroes(void) ""
> > > +dirty_bitmap_load_header(uint32_t flags) "flags %x"
> > > +dirty_bitmap_load_enter(void) ""
> > > +dirty_bitmap_load_success(void) ""
> > > diff --git a/vl.c b/vl.c
> > > index b4eaf03..f1ee9ff 100644
> > > --- a/vl.c
> > > +++ b/vl.c
> > > @@ -4405,6 +4405,7 @@ int main(int argc, char **argv, char **envp)
> > >       blk_mig_init();
> > >       ram_mig_init();
> > > +    dirty_bitmap_mig_init();
> > >       /* If the currently selected machine wishes to override the 
> > > units-per-bus
> > >        * property of its default HBA interface type, do so now. */
> > > -- 
> > > 1.8.3.1
> > > 
> > --
> > Dr. David Alan Gilbert / address@hidden / Manchester, UK
> 
> 
> -- 
> Best regards,
> Vladimir
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK