Re: [Qemu-devel] [PATCHv2] migration: move ram migration support

[Michael S. Tsirkin]

On Thu, Mar 07, 2013 at 04:20:48PM +0100, Paolo Bonzini wrote:
> Il 07/03/2013 14:32, Michael S. Tsirkin ha scritto:
> > +#ifdef DEBUG_ARCH_INIT
> > +#define DPRINTF(fmt, ...) \
> > +    do { fprintf(stdout, "arch_init: " fmt, ## __VA_ARGS__); } while (0)
> 
> These need to be adjusted, but it can be a follow-up.
> 
> Paolo

Thanks, will do a follow-up.

> > +#else
> > +#define DPRINTF(fmt, ...) \
> > +    do { } while (0)
> > +#endif
> > +
> > +/***********************************************************/
> > +/* ram save/restore */
> > +
> > +#define RAM_SAVE_FLAG_FULL     0x01 /* Obsolete, not used anymore */
> > +#define RAM_SAVE_FLAG_COMPRESS 0x02
> > +#define RAM_SAVE_FLAG_MEM_SIZE 0x04
> > +#define RAM_SAVE_FLAG_PAGE     0x08
> > +#define RAM_SAVE_FLAG_EOS      0x10
> > +#define RAM_SAVE_FLAG_CONTINUE 0x20
> > +#define RAM_SAVE_FLAG_XBZRLE   0x40
> > +
> > +#ifdef __ALTIVEC__
> > +#include <altivec.h>
> > +#define VECTYPE        vector unsigned char
> > +#define SPLAT(p)       vec_splat(vec_ld(0, p), 0)
> > +#define ALL_EQ(v1, v2) vec_all_eq(v1, v2)
> > +/* altivec.h may redefine the bool macro as vector type.
> > + * Reset it to POSIX semantics. */
> > +#undef bool
> > +#define bool _Bool
> > +#elif defined __SSE2__
> > +#include <emmintrin.h>
> > +#define VECTYPE        __m128i
> > +#define SPLAT(p)       _mm_set1_epi8(*(p))
> > +#define ALL_EQ(v1, v2) (_mm_movemask_epi8(_mm_cmpeq_epi8(v1, v2)) == 
> > 0xFFFF)
> > +#else
> > +#define VECTYPE        unsigned long
> > +#define SPLAT(p)       (*(p) * (~0UL / 255))
> > +#define ALL_EQ(v1, v2) ((v1) == (v2))
> > +#endif
> > +
> > +static int is_dup_page(uint8_t *page)
> > +{
> > +    VECTYPE *p = (VECTYPE *)page;
> > +    VECTYPE val = SPLAT(page);
> > +    int i;
> > +
> > +    for (i = 0; i < TARGET_PAGE_SIZE / sizeof(VECTYPE); i++) {
> > +        if (!ALL_EQ(val, p[i])) {
> > +            return 0;
> > +        }
> > +    }
> > +
> > +    return 1;
> > +}
> > +
> > +/* struct contains XBZRLE cache and a static page
> > +   used by the compression */
> > +static struct {
> > +    /* buffer used for XBZRLE encoding */
> > +    uint8_t *encoded_buf;
> > +    /* buffer for storing page content */
> > +    uint8_t *current_buf;
> > +    /* buffer used for XBZRLE decoding */
> > +    uint8_t *decoded_buf;
> > +    /* Cache for XBZRLE */
> > +    PageCache *cache;
> > +} XBZRLE = {
> > +    .encoded_buf = NULL,
> > +    .current_buf = NULL,
> > +    .decoded_buf = NULL,
> > +    .cache = NULL,
> > +};
> > +
> > +
> > +int64_t xbzrle_cache_resize(int64_t new_size)
> > +{
> > +    if (XBZRLE.cache != NULL) {
> > +        return cache_resize(XBZRLE.cache, new_size / TARGET_PAGE_SIZE) *
> > +            TARGET_PAGE_SIZE;
> > +    }
> > +    return pow2floor(new_size);
> > +}
> > +
> > +/* accounting for migration statistics */
> > +typedef struct AccountingInfo {
> > +    uint64_t dup_pages;
> > +    uint64_t norm_pages;
> > +    uint64_t iterations;
> > +    uint64_t xbzrle_bytes;
> > +    uint64_t xbzrle_pages;
> > +    uint64_t xbzrle_cache_miss;
> > +    uint64_t xbzrle_overflows;
> > +} AccountingInfo;
> > +
> > +static AccountingInfo acct_info;
> > +
> > +static void acct_clear(void)
> > +{
> > +    memset(&acct_info, 0, sizeof(acct_info));
> > +}
> > +
> > +uint64_t dup_mig_bytes_transferred(void)
> > +{
> > +    return acct_info.dup_pages * TARGET_PAGE_SIZE;
> > +}
> > +
> > +uint64_t dup_mig_pages_transferred(void)
> > +{
> > +    return acct_info.dup_pages;
> > +}
> > +
> > +uint64_t norm_mig_bytes_transferred(void)
> > +{
> > +    return acct_info.norm_pages * TARGET_PAGE_SIZE;
> > +}
> > +
> > +uint64_t norm_mig_pages_transferred(void)
> > +{
> > +    return acct_info.norm_pages;
> > +}
> > +
> > +uint64_t xbzrle_mig_bytes_transferred(void)
> > +{
> > +    return acct_info.xbzrle_bytes;
> > +}
> > +
> > +uint64_t xbzrle_mig_pages_transferred(void)
> > +{
> > +    return acct_info.xbzrle_pages;
> > +}
> > +
> > +uint64_t xbzrle_mig_pages_cache_miss(void)
> > +{
> > +    return acct_info.xbzrle_cache_miss;
> > +}
> > +
> > +uint64_t xbzrle_mig_pages_overflow(void)
> > +{
> > +    return acct_info.xbzrle_overflows;
> > +}
> > +
> > +static size_t save_block_hdr(QEMUFile *f, RAMBlock *block, ram_addr_t 
> > offset,
> > +                             int cont, int flag)
> > +{
> > +    size_t size;
> > +
> > +    qemu_put_be64(f, offset | cont | flag);
> > +    size = 8;
> > +
> > +    if (!cont) {
> > +        qemu_put_byte(f, strlen(block->idstr));
> > +        qemu_put_buffer(f, (uint8_t *)block->idstr,
> > +                        strlen(block->idstr));
> > +        size += 1 + strlen(block->idstr);
> > +    }
> > +    return size;
> > +}
> > +
> > +#define ENCODING_FLAG_XBZRLE 0x1
> > +
> > +static int save_xbzrle_page(QEMUFile *f, uint8_t *current_data,
> > +                            ram_addr_t current_addr, RAMBlock *block,
> > +                            ram_addr_t offset, int cont, bool last_stage)
> > +{
> > +    int encoded_len = 0, bytes_sent = -1;
> > +    uint8_t *prev_cached_page;
> > +
> > +    if (!cache_is_cached(XBZRLE.cache, current_addr)) {
> > +        if (!last_stage) {
> > +            cache_insert(XBZRLE.cache, current_addr, current_data);
> > +        }
> > +        acct_info.xbzrle_cache_miss++;
> > +        return -1;
> > +    }
> > +
> > +    prev_cached_page = get_cached_data(XBZRLE.cache, current_addr);
> > +
> > +    /* save current buffer into memory */
> > +    memcpy(XBZRLE.current_buf, current_data, TARGET_PAGE_SIZE);
> > +
> > +    /* XBZRLE encoding (if there is no overflow) */
> > +    encoded_len = xbzrle_encode_buffer(prev_cached_page, 
> > XBZRLE.current_buf,
> > +                                       TARGET_PAGE_SIZE, 
> > XBZRLE.encoded_buf,
> > +                                       TARGET_PAGE_SIZE);
> > +    if (encoded_len == 0) {
> > +        DPRINTF("Skipping unmodified page\n");
> > +        return 0;
> > +    } else if (encoded_len == -1) {
> > +        DPRINTF("Overflow\n");
> > +        acct_info.xbzrle_overflows++;
> > +        /* update data in the cache */
> > +        memcpy(prev_cached_page, current_data, TARGET_PAGE_SIZE);
> > +        return -1;
> > +    }
> > +
> > +    /* we need to update the data in the cache, in order to get the same 
> > data */
> > +    if (!last_stage) {
> > +        memcpy(prev_cached_page, XBZRLE.current_buf, TARGET_PAGE_SIZE);
> > +    }
> > +
> > +    /* Send XBZRLE based compressed page */
> > +    bytes_sent = save_block_hdr(f, block, offset, cont, 
> > RAM_SAVE_FLAG_XBZRLE);
> > +    qemu_put_byte(f, ENCODING_FLAG_XBZRLE);
> > +    qemu_put_be16(f, encoded_len);
> > +    qemu_put_buffer(f, XBZRLE.encoded_buf, encoded_len);
> > +    bytes_sent += encoded_len + 1 + 2;
> > +    acct_info.xbzrle_pages++;
> > +    acct_info.xbzrle_bytes += bytes_sent;
> > +
> > +    return bytes_sent;
> > +}
> > +
> > +
> > +/* This is the last block that we have visited serching for dirty pages
> > + */
> > +static RAMBlock *last_seen_block;
> > +/* This is the last block from where we have sent data */
> > +static RAMBlock *last_sent_block;
> > +static ram_addr_t last_offset;
> > +static unsigned long *migration_bitmap;
> > +static uint64_t migration_dirty_pages;
> > +static uint32_t last_version;
> > +
> > +static inline
> > +ram_addr_t migration_bitmap_find_and_reset_dirty(MemoryRegion *mr,
> > +                                                 ram_addr_t start)
> > +{
> > +    unsigned long base = mr->ram_addr >> TARGET_PAGE_BITS;
> > +    unsigned long nr = base + (start >> TARGET_PAGE_BITS);
> > +    unsigned long size = base + (int128_get64(mr->size) >> 
> > TARGET_PAGE_BITS);
> > +
> > +    unsigned long next = find_next_bit(migration_bitmap, size, nr);
> > +
> > +    if (next < size) {
> > +        clear_bit(next, migration_bitmap);
> > +        migration_dirty_pages--;
> > +    }
> > +    return (next - base) << TARGET_PAGE_BITS;
> > +}
> > +
> > +static inline bool migration_bitmap_set_dirty(MemoryRegion *mr,
> > +                                              ram_addr_t offset)
> > +{
> > +    bool ret;
> > +    int nr = (mr->ram_addr + offset) >> TARGET_PAGE_BITS;
> > +
> > +    ret = test_and_set_bit(nr, migration_bitmap);
> > +
> > +    if (!ret) {
> > +        migration_dirty_pages++;
> > +    }
> > +    return ret;
> > +}
> > +
> > +/* Needs iothread lock! */
> > +
> > +static void migration_bitmap_sync(void)
> > +{
> > +    RAMBlock *block;
> > +    ram_addr_t addr;
> > +    uint64_t num_dirty_pages_init = migration_dirty_pages;
> > +    MigrationState *s = migrate_get_current();
> > +    static int64_t start_time;
> > +    static int64_t num_dirty_pages_period;
> > +    int64_t end_time;
> > +
> > +    if (!start_time) {
> > +        start_time = qemu_get_clock_ms(rt_clock);
> > +    }
> > +
> > +    trace_migration_bitmap_sync_start();
> > +    memory_global_sync_dirty_bitmap(get_system_memory());
> > +
> > +    QTAILQ_FOREACH(block, &ram_list.blocks, next) {
> > +        for (addr = 0; addr < block->length; addr += TARGET_PAGE_SIZE) {
> > +            if (memory_region_test_and_clear_dirty(block->mr,
> > +                                                   addr, TARGET_PAGE_SIZE,
> > +                                                   
> > DIRTY_MEMORY_MIGRATION)) {
> > +                migration_bitmap_set_dirty(block->mr, addr);
> > +            }
> > +        }
> > +    }
> > +    trace_migration_bitmap_sync_end(migration_dirty_pages
> > +                                    - num_dirty_pages_init);
> > +    num_dirty_pages_period += migration_dirty_pages - num_dirty_pages_init;
> > +    end_time = qemu_get_clock_ms(rt_clock);
> > +
> > +    /* more than 1 second = 1000 millisecons */
> > +    if (end_time > start_time + 1000) {
> > +        s->dirty_pages_rate = num_dirty_pages_period * 1000
> > +            / (end_time - start_time);
> > +        s->dirty_bytes_rate = s->dirty_pages_rate * TARGET_PAGE_SIZE;
> > +        start_time = end_time;
> > +        num_dirty_pages_period = 0;
> > +    }
> > +}
> > +
> > +/*
> > + * ram_save_block: Writes a page of memory to the stream f
> > + *
> > + * Returns:  The number of bytes written.
> > + *           0 means no dirty pages
> > + */
> > +
> > +static int ram_save_block(QEMUFile *f, bool last_stage)
> > +{
> > +    RAMBlock *block = last_seen_block;
> > +    ram_addr_t offset = last_offset;
> > +    bool complete_round = false;
> > +    int bytes_sent = 0;
> > +    MemoryRegion *mr;
> > +    ram_addr_t current_addr;
> > +
> > +    if (!block)
> > +        block = QTAILQ_FIRST(&ram_list.blocks);
> > +
> > +    while (true) {
> > +        mr = block->mr;
> > +        offset = migration_bitmap_find_and_reset_dirty(mr, offset);
> > +        if (complete_round && block == last_seen_block &&
> > +            offset >= last_offset) {
> > +            break;
> > +        }
> > +        if (offset >= block->length) {
> > +            offset = 0;
> > +            block = QTAILQ_NEXT(block, next);
> > +            if (!block) {
> > +                block = QTAILQ_FIRST(&ram_list.blocks);
> > +                complete_round = true;
> > +            }
> > +        } else {
> > +            uint8_t *p;
> > +            int cont = (block == last_sent_block) ?
> > +                RAM_SAVE_FLAG_CONTINUE : 0;
> > +
> > +            p = memory_region_get_ram_ptr(mr) + offset;
> > +
> > +            /* In doubt sent page as normal */
> > +            bytes_sent = -1;
> > +            if (is_dup_page(p)) {
> > +                acct_info.dup_pages++;
> > +                bytes_sent = save_block_hdr(f, block, offset, cont,
> > +                                            RAM_SAVE_FLAG_COMPRESS);
> > +                qemu_put_byte(f, *p);
> > +                bytes_sent += 1;
> > +            } else if (migrate_use_xbzrle()) {
> > +                current_addr = block->offset + offset;
> > +                bytes_sent = save_xbzrle_page(f, p, current_addr, block,
> > +                                              offset, cont, last_stage);
> > +                if (!last_stage) {
> > +                    p = get_cached_data(XBZRLE.cache, current_addr);
> > +                }
> > +            }
> > +
> > +            /* XBZRLE overflow or normal page */
> > +            if (bytes_sent == -1) {
> > +                bytes_sent = save_block_hdr(f, block, offset, cont, 
> > RAM_SAVE_FLAG_PAGE);
> > +                qemu_put_buffer(f, p, TARGET_PAGE_SIZE);
> > +                bytes_sent += TARGET_PAGE_SIZE;
> > +                acct_info.norm_pages++;
> > +            }
> > +
> > +            /* if page is unmodified, continue to the next */
> > +            if (bytes_sent > 0) {
> > +                last_sent_block = block;
> > +                break;
> > +            }
> > +        }
> > +    }
> > +    last_seen_block = block;
> > +    last_offset = offset;
> > +
> > +    return bytes_sent;
> > +}
> > +
> > +static uint64_t bytes_transferred;
> > +
> > +static ram_addr_t ram_save_remaining(void)
> > +{
> > +    return migration_dirty_pages;
> > +}
> > +
> > +uint64_t ram_bytes_remaining(void)
> > +{
> > +    return ram_save_remaining() * TARGET_PAGE_SIZE;
> > +}
> > +
> > +uint64_t ram_bytes_transferred(void)
> > +{
> > +    return bytes_transferred;
> > +}
> > +
> > +uint64_t ram_bytes_total(void)
> > +{
> > +    RAMBlock *block;
> > +    uint64_t total = 0;
> > +
> > +    QTAILQ_FOREACH(block, &ram_list.blocks, next)
> > +        total += block->length;
> > +
> > +    return total;
> > +}
> > +
> > +static void migration_end(void)
> > +{
> > +    if (migration_bitmap) {
> > +        memory_global_dirty_log_stop();
> > +        g_free(migration_bitmap);
> > +        migration_bitmap = NULL;
> > +    }
> > +
> > +    if (XBZRLE.cache) {
> > +        cache_fini(XBZRLE.cache);
> > +        g_free(XBZRLE.cache);
> > +        g_free(XBZRLE.encoded_buf);
> > +        g_free(XBZRLE.current_buf);
> > +        g_free(XBZRLE.decoded_buf);
> > +        XBZRLE.cache = NULL;
> > +    }
> > +}
> > +
> > +static void ram_migration_cancel(void *opaque)
> > +{
> > +    migration_end();
> > +}
> > +
> > +static void reset_ram_globals(void)
> > +{
> > +    last_seen_block = NULL;
> > +    last_sent_block = NULL;
> > +    last_offset = 0;
> > +    last_version = ram_list.version;
> > +}
> > +
> > +#define MAX_WAIT 50 /* ms, half buffered_file limit */
> > +
> > +static int ram_save_setup(QEMUFile *f, void *opaque)
> > +{
> > +    RAMBlock *block;
> > +    int64_t ram_pages = last_ram_offset() >> TARGET_PAGE_BITS;
> > +
> > +    migration_bitmap = bitmap_new(ram_pages);
> > +    bitmap_set(migration_bitmap, 0, ram_pages);
> > +    migration_dirty_pages = ram_pages;
> > +
> > +    if (migrate_use_xbzrle()) {
> > +        XBZRLE.cache = cache_init(migrate_xbzrle_cache_size() /
> > +                                  TARGET_PAGE_SIZE,
> > +                                  TARGET_PAGE_SIZE);
> > +        if (!XBZRLE.cache) {
> > +            DPRINTF("Error creating cache\n");
> > +            return -1;
> > +        }
> > +        XBZRLE.encoded_buf = g_malloc0(TARGET_PAGE_SIZE);
> > +        XBZRLE.current_buf = g_malloc(TARGET_PAGE_SIZE);
> > +        acct_clear();
> > +    }
> > +
> > +    qemu_mutex_lock_iothread();
> > +    qemu_mutex_lock_ramlist();
> > +    bytes_transferred = 0;
> > +    reset_ram_globals();
> > +
> > +    memory_global_dirty_log_start();
> > +    migration_bitmap_sync();
> > +    qemu_mutex_unlock_iothread();
> > +
> > +    qemu_put_be64(f, ram_bytes_total() | RAM_SAVE_FLAG_MEM_SIZE);
> > +
> > +    QTAILQ_FOREACH(block, &ram_list.blocks, next) {
> > +        qemu_put_byte(f, strlen(block->idstr));
> > +        qemu_put_buffer(f, (uint8_t *)block->idstr, strlen(block->idstr));
> > +        qemu_put_be64(f, block->length);
> > +    }
> > +
> > +    qemu_mutex_unlock_ramlist();
> > +    qemu_put_be64(f, RAM_SAVE_FLAG_EOS);
> > +
> > +    return 0;
> > +}
> > +
> > +static int ram_save_iterate(QEMUFile *f, void *opaque)
> > +{
> > +    int ret;
> > +    int i;
> > +    int64_t t0;
> > +    int total_sent = 0;
> > +
> > +    qemu_mutex_lock_ramlist();
> > +
> > +    if (ram_list.version != last_version) {
> > +        reset_ram_globals();
> > +    }
> > +
> > +    t0 = qemu_get_clock_ns(rt_clock);
> > +    i = 0;
> > +    while ((ret = qemu_file_rate_limit(f)) == 0) {
> > +        int bytes_sent;
> > +
> > +        bytes_sent = ram_save_block(f, false);
> > +        /* no more blocks to sent */
> > +        if (bytes_sent == 0) {
> > +            break;
> > +        }
> > +        total_sent += bytes_sent;
> > +        acct_info.iterations++;
> > +        /* we want to check in the 1st loop, just in case it was the 1st 
> > time
> > +           and we had to sync the dirty bitmap.
> > +           qemu_get_clock_ns() is a bit expensive, so we only check each 
> > some
> > +           iterations
> > +        */
> > +        if ((i & 63) == 0) {
> > +            uint64_t t1 = (qemu_get_clock_ns(rt_clock) - t0) / 1000000;
> > +            if (t1 > MAX_WAIT) {
> > +                DPRINTF("big wait: %" PRIu64 " milliseconds, %d 
> > iterations\n",
> > +                        t1, i);
> > +                break;
> > +            }
> > +        }
> > +        i++;
> > +    }
> > +
> > +    qemu_mutex_unlock_ramlist();
> > +
> > +    if (ret < 0) {
> > +        bytes_transferred += total_sent;
> > +        return ret;
> > +    }
> > +
> > +    qemu_put_be64(f, RAM_SAVE_FLAG_EOS);
> > +    total_sent += 8;
> > +    bytes_transferred += total_sent;
> > +
> > +    return total_sent;
> > +}
> > +
> > +static int ram_save_complete(QEMUFile *f, void *opaque)
> > +{
> > +    qemu_mutex_lock_ramlist();
> > +    migration_bitmap_sync();
> > +
> > +    /* try transferring iterative blocks of memory */
> > +
> > +    /* flush all remaining blocks regardless of rate limiting */
> > +    while (true) {
> > +        int bytes_sent;
> > +
> > +        bytes_sent = ram_save_block(f, true);
> > +        /* no more blocks to sent */
> > +        if (bytes_sent == 0) {
> > +            break;
> > +        }
> > +        bytes_transferred += bytes_sent;
> > +    }
> > +    migration_end();
> > +
> > +    qemu_mutex_unlock_ramlist();
> > +    qemu_put_be64(f, RAM_SAVE_FLAG_EOS);
> > +
> > +    return 0;
> > +}
> > +
> > +static uint64_t ram_save_pending(QEMUFile *f, void *opaque, uint64_t 
> > max_size)
> > +{
> > +    uint64_t remaining_size;
> > +
> > +    remaining_size = ram_save_remaining() * TARGET_PAGE_SIZE;
> > +
> > +    if (remaining_size < max_size) {
> > +        qemu_mutex_lock_iothread();
> > +        migration_bitmap_sync();
> > +        qemu_mutex_unlock_iothread();
> > +        remaining_size = ram_save_remaining() * TARGET_PAGE_SIZE;
> > +    }
> > +    return remaining_size;
> > +}
> > +
> > +static int load_xbzrle(QEMUFile *f, ram_addr_t addr, void *host)
> > +{
> > +    int ret, rc = 0;
> > +    unsigned int xh_len;
> > +    int xh_flags;
> > +
> > +    if (!XBZRLE.decoded_buf) {
> > +        XBZRLE.decoded_buf = g_malloc(TARGET_PAGE_SIZE);
> > +    }
> > +
> > +    /* extract RLE header */
> > +    xh_flags = qemu_get_byte(f);
> > +    xh_len = qemu_get_be16(f);
> > +
> > +    if (xh_flags != ENCODING_FLAG_XBZRLE) {
> > +        fprintf(stderr, "Failed to load XBZRLE page - wrong 
> > compression!\n");
> > +        return -1;
> > +    }
> > +
> > +    if (xh_len > TARGET_PAGE_SIZE) {
> > +        fprintf(stderr, "Failed to load XBZRLE page - len overflow!\n");
> > +        return -1;
> > +    }
> > +    /* load data and decode */
> > +    qemu_get_buffer(f, XBZRLE.decoded_buf, xh_len);
> > +
> > +    /* decode RLE */
> > +    ret = xbzrle_decode_buffer(XBZRLE.decoded_buf, xh_len, host,
> > +                               TARGET_PAGE_SIZE);
> > +    if (ret == -1) {
> > +        fprintf(stderr, "Failed to load XBZRLE page - decode error!\n");
> > +        rc = -1;
> > +    } else  if (ret > TARGET_PAGE_SIZE) {
> > +        fprintf(stderr, "Failed to load XBZRLE page - size %d exceeds 
> > %d!\n",
> > +                ret, TARGET_PAGE_SIZE);
> > +        abort();
> > +    }
> > +
> > +    return rc;
> > +}
> > +
> > +static inline void *host_from_stream_offset(QEMUFile *f,
> > +                                            ram_addr_t offset,
> > +                                            int flags)
> > +{
> > +    static RAMBlock *block = NULL;
> > +    char id[256];
> > +    uint8_t len;
> > +
> > +    if (flags & RAM_SAVE_FLAG_CONTINUE) {
> > +        if (!block) {
> > +            fprintf(stderr, "Ack, bad migration stream!\n");
> > +            return NULL;
> > +        }
> > +
> > +        return memory_region_get_ram_ptr(block->mr) + offset;
> > +    }
> > +
> > +    len = qemu_get_byte(f);
> > +    qemu_get_buffer(f, (uint8_t *)id, len);
> > +    id[len] = 0;
> > +
> > +    QTAILQ_FOREACH(block, &ram_list.blocks, next) {
> > +        if (!strncmp(id, block->idstr, sizeof(id)))
> > +            return memory_region_get_ram_ptr(block->mr) + offset;
> > +    }
> > +
> > +    fprintf(stderr, "Can't find block %s!\n", id);
> > +    return NULL;
> > +}
> > +
> > +static int ram_load(QEMUFile *f, void *opaque, int version_id)
> > +{
> > +    ram_addr_t addr;
> > +    int flags, ret = 0;
> > +    int error;
> > +    static uint64_t seq_iter;
> > +
> > +    seq_iter++;
> > +
> > +    if (version_id < 4 || version_id > 4) {
> > +        return -EINVAL;
> > +    }
> > +
> > +    do {
> > +        addr = qemu_get_be64(f);
> > +
> > +        flags = addr & ~TARGET_PAGE_MASK;
> > +        addr &= TARGET_PAGE_MASK;
> > +
> > +        if (flags & RAM_SAVE_FLAG_MEM_SIZE) {
> > +            if (version_id == 4) {
> > +                /* Synchronize RAM block list */
> > +                char id[256];
> > +                ram_addr_t length;
> > +                ram_addr_t total_ram_bytes = addr;
> > +
> > +                while (total_ram_bytes) {
> > +                    RAMBlock *block;
> > +                    uint8_t len;
> > +
> > +                    len = qemu_get_byte(f);
> > +                    qemu_get_buffer(f, (uint8_t *)id, len);
> > +                    id[len] = 0;
> > +                    length = qemu_get_be64(f);
> > +
> > +                    QTAILQ_FOREACH(block, &ram_list.blocks, next) {
> > +                        if (!strncmp(id, block->idstr, sizeof(id))) {
> > +                            if (block->length != length) {
> > +                                ret =  -EINVAL;
> > +                                goto done;
> > +                            }
> > +                            break;
> > +                        }
> > +                    }
> > +
> > +                    if (!block) {
> > +                        fprintf(stderr, "Unknown ramblock \"%s\", cannot "
> > +                                "accept migration\n", id);
> > +                        ret = -EINVAL;
> > +                        goto done;
> > +                    }
> > +
> > +                    total_ram_bytes -= length;
> > +                }
> > +            }
> > +        }
> > +
> > +        if (flags & RAM_SAVE_FLAG_COMPRESS) {
> > +            void *host;
> > +            uint8_t ch;
> > +
> > +            host = host_from_stream_offset(f, addr, flags);
> > +            if (!host) {
> > +                return -EINVAL;
> > +            }
> > +
> > +            ch = qemu_get_byte(f);
> > +            memset(host, ch, TARGET_PAGE_SIZE);
> > +#ifndef _WIN32
> > +            if (ch == 0 &&
> > +                (!kvm_enabled() || kvm_has_sync_mmu()) &&
> > +                getpagesize() <= TARGET_PAGE_SIZE) {
> > +                qemu_madvise(host, TARGET_PAGE_SIZE, QEMU_MADV_DONTNEED);
> > +            }
> > +#endif
> > +        } else if (flags & RAM_SAVE_FLAG_PAGE) {
> > +            void *host;
> > +
> > +            host = host_from_stream_offset(f, addr, flags);
> > +            if (!host) {
> > +                return -EINVAL;
> > +            }
> > +
> > +            qemu_get_buffer(f, host, TARGET_PAGE_SIZE);
> > +        } else if (flags & RAM_SAVE_FLAG_XBZRLE) {
> > +            void *host = host_from_stream_offset(f, addr, flags);
> > +            if (!host) {
> > +                return -EINVAL;
> > +            }
> > +
> > +            if (load_xbzrle(f, addr, host) < 0) {
> > +                ret = -EINVAL;
> > +                goto done;
> > +            }
> > +        }
> > +        error = qemu_file_get_error(f);
> > +        if (error) {
> > +            ret = error;
> > +            goto done;
> > +        }
> > +    } while (!(flags & RAM_SAVE_FLAG_EOS));
> > +
> > +done:
> > +    DPRINTF("Completed load of VM with exit code %d seq iteration "
> > +            "%" PRIu64 "\n", ret, seq_iter);
> > +    return ret;
> > +}
> > +
> > +SaveVMHandlers savevm_ram_handlers = {
> > +    .save_live_setup = ram_save_setup,
> > +    .save_live_iterate = ram_save_iterate,
> > +    .save_live_complete = ram_save_complete,
> > +    .save_live_pending = ram_save_pending,
> > +    .load_state = ram_load,
> > +    .cancel = ram_migration_cancel,
> > +};
> >