migration: move ram stuff to migration/ram

For historic reasons, ram migration have been on arch_init.c.  Just
split it into migration/ram.c, the same that happened with block.c.

There is only code movement, no changes altogether.

Signed-off-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

1 files changed, 1639 insertions, 0 deletions

diff --git a/migration/ram.c b/migration/ram.c
new file mode 100644
index 0000000000..ff889ba4ba
--- /dev/null
+++ b/migration/ram.c
@@ -0,0 +1,1639 @@
+/*
+ * QEMU System Emulator
+ *
+ * Copyright (c) 2003-2008 Fabrice Bellard
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+#include <stdint.h>
+#include <stdarg.h>
+#include <stdlib.h>
+#include <zlib.h>
+#ifndef _WIN32
+#include <sys/types.h>
+#include <sys/mman.h>
+#endif
+#include "config.h"
+#include "monitor/monitor.h"
+#include "sysemu/sysemu.h"
+#include "qemu/bitops.h"
+#include "qemu/bitmap.h"
+#include "hw/i386/pc.h"
+#include "hw/pci/pci.h"
+#include "hw/audio/audio.h"
+#include "migration/migration.h"
+#include "exec/address-spaces.h"
+#include "migration/page_cache.h"
+#include "qemu/config-file.h"
+#include "qemu/error-report.h"
+#include "qmp-commands.h"
+#include "trace.h"
+#include "exec/cpu-all.h"
+#include "exec/ram_addr.h"
+#include "qemu/host-utils.h"
+#include "qemu/rcu_queue.h"
+
+#ifdef DEBUG_MIGRATION_RAM
+#define DPRINTF(fmt, ...) \
+    do { fprintf(stdout, "migration_ram: " fmt, ## __VA_ARGS__); } while (0)
+#else
+#define DPRINTF(fmt, ...) \
+    do { } while (0)
+#endif
+
+static bool mig_throttle_on;
+static int dirty_rate_high_cnt;
+static void check_guest_throttling(void);
+
+static uint64_t bitmap_sync_count;
+
+/***********************************************************/
+/* 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
+/* 0x80 is reserved in migration.h start with 0x100 next */
+#define RAM_SAVE_FLAG_COMPRESS_PAGE    0x100
+
+static const uint8_t ZERO_TARGET_PAGE[TARGET_PAGE_SIZE];
+
+static inline bool is_zero_range(uint8_t *p, uint64_t size)
+{
+    return buffer_find_nonzero_offset(p, size) == size;
+}
+
+/* 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;
+    /* Cache for XBZRLE, Protected by lock. */
+    PageCache *cache;
+    QemuMutex lock;
+} XBZRLE;
+
+/* buffer used for XBZRLE decoding */
+static uint8_t *xbzrle_decoded_buf;
+
+static void XBZRLE_cache_lock(void)
+{
+    if (migrate_use_xbzrle())
+        qemu_mutex_lock(&XBZRLE.lock);
+}
+
+static void XBZRLE_cache_unlock(void)
+{
+    if (migrate_use_xbzrle())
+        qemu_mutex_unlock(&XBZRLE.lock);
+}
+
+/*
+ * called from qmp_migrate_set_cache_size in main thread, possibly while
+ * a migration is in progress.
+ * A running migration maybe using the cache and might finish during this
+ * call, hence changes to the cache are protected by XBZRLE.lock().
+ */
+int64_t xbzrle_cache_resize(int64_t new_size)
+{
+    PageCache *new_cache;
+    int64_t ret;
+
+    if (new_size < TARGET_PAGE_SIZE) {
+        return -1;
+    }
+
+    XBZRLE_cache_lock();
+
+    if (XBZRLE.cache != NULL) {
+        if (pow2floor(new_size) == migrate_xbzrle_cache_size()) {
+            goto out_new_size;
+        }
+        new_cache = cache_init(new_size / TARGET_PAGE_SIZE,
+                                        TARGET_PAGE_SIZE);
+        if (!new_cache) {
+            error_report("Error creating cache");
+            ret = -1;
+            goto out;
+        }
+
+        cache_fini(XBZRLE.cache);
+        XBZRLE.cache = new_cache;
+    }
+
+out_new_size:
+    ret = pow2floor(new_size);
+out:
+    XBZRLE_cache_unlock();
+    return ret;
+}
+
+/* accounting for migration statistics */
+typedef struct AccountingInfo {
+    uint64_t dup_pages;
+    uint64_t skipped_pages;
+    uint64_t norm_pages;
+    uint64_t iterations;
+    uint64_t xbzrle_bytes;
+    uint64_t xbzrle_pages;
+    uint64_t xbzrle_cache_miss;
+    double xbzrle_cache_miss_rate;
+    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 skipped_mig_bytes_transferred(void)
+{
+    return acct_info.skipped_pages * TARGET_PAGE_SIZE;
+}
+
+uint64_t skipped_mig_pages_transferred(void)
+{
+    return acct_info.skipped_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;
+}
+
+double xbzrle_mig_cache_miss_rate(void)
+{
+    return acct_info.xbzrle_cache_miss_rate;
+}
+
+uint64_t xbzrle_mig_pages_overflow(void)
+{
+    return acct_info.xbzrle_overflows;
+}
+
+/* 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 bool ram_bulk_stage;
+
+struct CompressParam {
+    bool start;
+    bool done;
+    QEMUFile *file;
+    QemuMutex mutex;
+    QemuCond cond;
+    RAMBlock *block;
+    ram_addr_t offset;
+};
+typedef struct CompressParam CompressParam;
+
+struct DecompressParam {
+    bool start;
+    QemuMutex mutex;
+    QemuCond cond;
+    void *des;
+    uint8 *compbuf;
+    int len;
+};
+typedef struct DecompressParam DecompressParam;
+
+static CompressParam *comp_param;
+static QemuThread *compress_threads;
+/* comp_done_cond is used to wake up the migration thread when
+ * one of the compression threads has finished the compression.
+ * comp_done_lock is used to co-work with comp_done_cond.
+ */
+static QemuMutex *comp_done_lock;
+static QemuCond *comp_done_cond;
+/* The empty QEMUFileOps will be used by file in CompressParam */
+static const QEMUFileOps empty_ops = { };
+
+static bool compression_switch;
+static bool quit_comp_thread;
+static bool quit_decomp_thread;
+static DecompressParam *decomp_param;
+static QemuThread *decompress_threads;
+static uint8_t *compressed_data_buf;
+
+static int do_compress_ram_page(CompressParam *param);
+
+static void *do_data_compress(void *opaque)
+{
+    CompressParam *param = opaque;
+
+    while (!quit_comp_thread) {
+        qemu_mutex_lock(&param->mutex);
+        /* Re-check the quit_comp_thread in case of
+         * terminate_compression_threads is called just before
+         * qemu_mutex_lock(&param->mutex) and after
+         * while(!quit_comp_thread), re-check it here can make
+         * sure the compression thread terminate as expected.
+         */
+        while (!param->start && !quit_comp_thread) {
+            qemu_cond_wait(&param->cond, &param->mutex);
+        }
+        if (!quit_comp_thread) {
+            do_compress_ram_page(param);
+        }
+        param->start = false;
+        qemu_mutex_unlock(&param->mutex);
+
+        qemu_mutex_lock(comp_done_lock);
+        param->done = true;
+        qemu_cond_signal(comp_done_cond);
+        qemu_mutex_unlock(comp_done_lock);
+    }
+
+    return NULL;
+}
+
+static inline void terminate_compression_threads(void)
+{
+    int idx, thread_count;
+
+    thread_count = migrate_compress_threads();
+    quit_comp_thread = true;
+    for (idx = 0; idx < thread_count; idx++) {
+        qemu_mutex_lock(&comp_param[idx].mutex);
+        qemu_cond_signal(&comp_param[idx].cond);
+        qemu_mutex_unlock(&comp_param[idx].mutex);
+    }
+}
+
+void migrate_compress_threads_join(void)
+{
+    int i, thread_count;
+
+    if (!migrate_use_compression()) {
+        return;
+    }
+    terminate_compression_threads();
+    thread_count = migrate_compress_threads();
+    for (i = 0; i < thread_count; i++) {
+        qemu_thread_join(compress_threads + i);
+        qemu_fclose(comp_param[i].file);
+        qemu_mutex_destroy(&comp_param[i].mutex);
+        qemu_cond_destroy(&comp_param[i].cond);
+    }
+    qemu_mutex_destroy(comp_done_lock);
+    qemu_cond_destroy(comp_done_cond);
+    g_free(compress_threads);
+    g_free(comp_param);
+    g_free(comp_done_cond);
+    g_free(comp_done_lock);
+    compress_threads = NULL;
+    comp_param = NULL;
+    comp_done_cond = NULL;
+    comp_done_lock = NULL;
+}
+
+void migrate_compress_threads_create(void)
+{
+    int i, thread_count;
+
+    if (!migrate_use_compression()) {
+        return;
+    }
+    quit_comp_thread = false;
+    compression_switch = true;
+    thread_count = migrate_compress_threads();
+    compress_threads = g_new0(QemuThread, thread_count);
+    comp_param = g_new0(CompressParam, thread_count);
+    comp_done_cond = g_new0(QemuCond, 1);
+    comp_done_lock = g_new0(QemuMutex, 1);
+    qemu_cond_init(comp_done_cond);
+    qemu_mutex_init(comp_done_lock);
+    for (i = 0; i < thread_count; i++) {
+        /* com_param[i].file is just used as a dummy buffer to save data, set
+         * it's ops to empty.
+         */
+        comp_param[i].file = qemu_fopen_ops(NULL, &empty_ops);
+        comp_param[i].done = true;
+        qemu_mutex_init(&comp_param[i].mutex);
+        qemu_cond_init(&comp_param[i].cond);
+        qemu_thread_create(compress_threads + i, "compress",
+                           do_data_compress, comp_param + i,
+                           QEMU_THREAD_JOINABLE);
+    }
+}
+
+/**
+ * save_page_header: Write page header to wire
+ *
+ * If this is the 1st block, it also writes the block identification
+ *
+ * Returns: Number of bytes written
+ *
+ * @f: QEMUFile where to send the data
+ * @block: block that contains the page we want to send
+ * @offset: offset inside the block for the page
+ *          in the lower bits, it contains flags
+ */
+static size_t save_page_header(QEMUFile *f, RAMBlock *block, ram_addr_t offset)
+{
+    size_t size;
+
+    qemu_put_be64(f, offset);
+    size = 8;
+
+    if (!(offset & RAM_SAVE_FLAG_CONTINUE)) {
+        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;
+}
+
+/* Update the xbzrle cache to reflect a page that's been sent as all 0.
+ * The important thing is that a stale (not-yet-0'd) page be replaced
+ * by the new data.
+ * As a bonus, if the page wasn't in the cache it gets added so that
+ * when a small write is made into the 0'd page it gets XBZRLE sent
+ */
+static void xbzrle_cache_zero_page(ram_addr_t current_addr)
+{
+    if (ram_bulk_stage || !migrate_use_xbzrle()) {
+        return;
+    }
+
+    /* We don't care if this fails to allocate a new cache page
+     * as long as it updated an old one */
+    cache_insert(XBZRLE.cache, current_addr, ZERO_TARGET_PAGE,
+                 bitmap_sync_count);
+}
+
+#define ENCODING_FLAG_XBZRLE 0x1
+
+/**
+ * save_xbzrle_page: compress and send current page
+ *
+ * Returns: 1 means that we wrote the page
+ *          0 means that page is identical to the one already sent
+ *          -1 means that xbzrle would be longer than normal
+ *
+ * @f: QEMUFile where to send the data
+ * @current_data:
+ * @current_addr:
+ * @block: block that contains the page we want to send
+ * @offset: offset inside the block for the page
+ * @last_stage: if we are at the completion stage
+ * @bytes_transferred: increase it with the number of transferred bytes
+ */
+static int save_xbzrle_page(QEMUFile *f, uint8_t **current_data,
+                            ram_addr_t current_addr, RAMBlock *block,
+                            ram_addr_t offset, bool last_stage,
+                            uint64_t *bytes_transferred)
+{
+    int encoded_len = 0, bytes_xbzrle;
+    uint8_t *prev_cached_page;
+
+    if (!cache_is_cached(XBZRLE.cache, current_addr, bitmap_sync_count)) {
+        acct_info.xbzrle_cache_miss++;
+        if (!last_stage) {
+            if (cache_insert(XBZRLE.cache, current_addr, *current_data,
+                             bitmap_sync_count) == -1) {
+                return -1;
+            } else {
+                /* update *current_data when the page has been
+                   inserted into cache */
+                *current_data = get_cached_data(XBZRLE.cache, current_addr);
+            }
+        }
+        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 */
+        if (!last_stage) {
+            memcpy(prev_cached_page, *current_data, TARGET_PAGE_SIZE);
+            *current_data = prev_cached_page;
+        }
+        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_xbzrle = save_page_header(f, block, offset | 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_xbzrle += encoded_len + 1 + 2;
+    acct_info.xbzrle_pages++;
+    acct_info.xbzrle_bytes += bytes_xbzrle;
+    *bytes_transferred += bytes_xbzrle;
+
+    return 1;
+}
+
+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);
+    uint64_t mr_size = TARGET_PAGE_ALIGN(memory_region_size(mr));
+    unsigned long size = base + (mr_size >> TARGET_PAGE_BITS);
+
+    unsigned long next;
+
+    if (ram_bulk_stage && nr > base) {
+        next = nr + 1;
+    } else {
+        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 void migration_bitmap_sync_range(ram_addr_t start, ram_addr_t length)
+{
+    migration_dirty_pages +=
+        cpu_physical_memory_sync_dirty_bitmap(migration_bitmap, start, length);
+}
+
+
+/* Fix me: there are too many global variables used in migration process. */
+static int64_t start_time;
+static int64_t bytes_xfer_prev;
+static int64_t num_dirty_pages_period;
+static uint64_t xbzrle_cache_miss_prev;
+static uint64_t iterations_prev;
+
+static void migration_bitmap_sync_init(void)
+{
+    start_time = 0;
+    bytes_xfer_prev = 0;
+    num_dirty_pages_period = 0;
+    xbzrle_cache_miss_prev = 0;
+    iterations_prev = 0;
+}
+
+/* Called with iothread lock held, to protect ram_list.dirty_memory[] */
+static void migration_bitmap_sync(void)
+{
+    RAMBlock *block;
+    uint64_t num_dirty_pages_init = migration_dirty_pages;
+    MigrationState *s = migrate_get_current();
+    int64_t end_time;
+    int64_t bytes_xfer_now;
+
+    bitmap_sync_count++;
+
+    if (!bytes_xfer_prev) {
+        bytes_xfer_prev = ram_bytes_transferred();
+    }
+
+    if (!start_time) {
+        start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
+    }
+
+    trace_migration_bitmap_sync_start();
+    address_space_sync_dirty_bitmap(&address_space_memory);
+
+    rcu_read_lock();
+    QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
+        migration_bitmap_sync_range(block->mr->ram_addr, block->used_length);
+    }
+    rcu_read_unlock();
+
+    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_clock_get_ms(QEMU_CLOCK_REALTIME);
+
+    /* more than 1 second = 1000 millisecons */
+    if (end_time > start_time + 1000) {
+        if (migrate_auto_converge()) {
+            /* The following detection logic can be refined later. For now:
+               Check to see if the dirtied bytes is 50% more than the approx.
+               amount of bytes that just got transferred since the last time we
+               were in this routine. If that happens >N times (for now N==4)
+               we turn on the throttle down logic */
+            bytes_xfer_now = ram_bytes_transferred();
+            if (s->dirty_pages_rate &&
+               (num_dirty_pages_period * TARGET_PAGE_SIZE >
+                   (bytes_xfer_now - bytes_xfer_prev)/2) &&
+               (dirty_rate_high_cnt++ > 4)) {
+                    trace_migration_throttle();
+                    mig_throttle_on = true;
+                    dirty_rate_high_cnt = 0;
+             }
+             bytes_xfer_prev = bytes_xfer_now;
+        } else {
+             mig_throttle_on = false;
+        }
+        if (migrate_use_xbzrle()) {
+            if (iterations_prev != acct_info.iterations) {
+                acct_info.xbzrle_cache_miss_rate =
+                   (double)(acct_info.xbzrle_cache_miss -
+                            xbzrle_cache_miss_prev) /
+                   (acct_info.iterations - iterations_prev);
+            }
+            iterations_prev = acct_info.iterations;
+            xbzrle_cache_miss_prev = acct_info.xbzrle_cache_miss;
+        }
+        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;
+    }
+    s->dirty_sync_count = bitmap_sync_count;
+}
+
+/**
+ * save_zero_page: Send the zero page to the stream
+ *
+ * Returns: Number of pages written.
+ *
+ * @f: QEMUFile where to send the data
+ * @block: block that contains the page we want to send
+ * @offset: offset inside the block for the page
+ * @p: pointer to the page
+ * @bytes_transferred: increase it with the number of transferred bytes
+ */
+static int save_zero_page(QEMUFile *f, RAMBlock *block, ram_addr_t offset,
+                          uint8_t *p, uint64_t *bytes_transferred)
+{
+    int pages = -1;
+
+    if (is_zero_range(p, TARGET_PAGE_SIZE)) {
+        acct_info.dup_pages++;
+        *bytes_transferred += save_page_header(f, block,
+                                               offset | RAM_SAVE_FLAG_COMPRESS);
+        qemu_put_byte(f, 0);
+        *bytes_transferred += 1;
+        pages = 1;
+    }
+
+    return pages;
+}
+
+/**
+ * ram_save_page: Send the given page to the stream
+ *
+ * Returns: Number of pages written.
+ *
+ * @f: QEMUFile where to send the data
+ * @block: block that contains the page we want to send
+ * @offset: offset inside the block for the page
+ * @last_stage: if we are at the completion stage
+ * @bytes_transferred: increase it with the number of transferred bytes
+ */
+static int ram_save_page(QEMUFile *f, RAMBlock* block, ram_addr_t offset,
+                         bool last_stage, uint64_t *bytes_transferred)
+{
+    int pages = -1;
+    uint64_t bytes_xmit;
+    ram_addr_t current_addr;
+    MemoryRegion *mr = block->mr;
+    uint8_t *p;
+    int ret;
+    bool send_async = true;
+
+    p = memory_region_get_ram_ptr(mr) + offset;
+
+    /* In doubt sent page as normal */
+    bytes_xmit = 0;
+    ret = ram_control_save_page(f, block->offset,
+                           offset, TARGET_PAGE_SIZE, &bytes_xmit);
+    if (bytes_xmit) {
+        *bytes_transferred += bytes_xmit;
+        pages = 1;
+    }
+
+    XBZRLE_cache_lock();
+
+    current_addr = block->offset + offset;
+
+    if (block == last_sent_block) {
+        offset |= RAM_SAVE_FLAG_CONTINUE;
+    }
+    if (ret != RAM_SAVE_CONTROL_NOT_SUPP) {
+        if (ret != RAM_SAVE_CONTROL_DELAYED) {
+            if (bytes_xmit > 0) {
+                acct_info.norm_pages++;
+            } else if (bytes_xmit == 0) {
+                acct_info.dup_pages++;
+            }
+        }
+    } else {
+        pages = save_zero_page(f, block, offset, p, bytes_transferred);
+        if (pages > 0) {
+            /* Must let xbzrle know, otherwise a previous (now 0'd) cached
+             * page would be stale
+             */
+            xbzrle_cache_zero_page(current_addr);
+        } else if (!ram_bulk_stage && migrate_use_xbzrle()) {
+            pages = save_xbzrle_page(f, &p, current_addr, block,
+                                     offset, last_stage, bytes_transferred);
+            if (!last_stage) {
+                /* Can't send this cached data async, since the cache page
+                 * might get updated before it gets to the wire
+                 */
+                send_async = false;
+            }
+        }
+    }
+
+    /* XBZRLE overflow or normal page */
+    if (pages == -1) {
+        *bytes_transferred += save_page_header(f, block,
+                                               offset | RAM_SAVE_FLAG_PAGE);
+        if (send_async) {
+            qemu_put_buffer_async(f, p, TARGET_PAGE_SIZE);
+        } else {
+            qemu_put_buffer(f, p, TARGET_PAGE_SIZE);
+        }
+        *bytes_transferred += TARGET_PAGE_SIZE;
+        pages = 1;
+        acct_info.norm_pages++;
+    }
+
+    XBZRLE_cache_unlock();
+
+    return pages;
+}
+
+static int do_compress_ram_page(CompressParam *param)
+{
+    int bytes_sent, blen;
+    uint8_t *p;
+    RAMBlock *block = param->block;
+    ram_addr_t offset = param->offset;
+
+    p = memory_region_get_ram_ptr(block->mr) + (offset & TARGET_PAGE_MASK);
+
+    bytes_sent = save_page_header(param->file, block, offset |
+                                  RAM_SAVE_FLAG_COMPRESS_PAGE);
+    blen = qemu_put_compression_data(param->file, p, TARGET_PAGE_SIZE,
+                                     migrate_compress_level());
+    bytes_sent += blen;
+
+    return bytes_sent;
+}
+
+static inline void start_compression(CompressParam *param)
+{
+    param->done = false;
+    qemu_mutex_lock(&param->mutex);
+    param->start = true;
+    qemu_cond_signal(&param->cond);
+    qemu_mutex_unlock(&param->mutex);
+}
+
+static inline void start_decompression(DecompressParam *param)
+{
+    qemu_mutex_lock(&param->mutex);
+    param->start = true;
+    qemu_cond_signal(&param->cond);
+    qemu_mutex_unlock(&param->mutex);
+}
+
+static uint64_t bytes_transferred;
+
+static void flush_compressed_data(QEMUFile *f)
+{
+    int idx, len, thread_count;
+
+    if (!migrate_use_compression()) {
+        return;
+    }
+    thread_count = migrate_compress_threads();
+    for (idx = 0; idx < thread_count; idx++) {
+        if (!comp_param[idx].done) {
+            qemu_mutex_lock(comp_done_lock);
+            while (!comp_param[idx].done && !quit_comp_thread) {
+                qemu_cond_wait(comp_done_cond, comp_done_lock);
+            }
+            qemu_mutex_unlock(comp_done_lock);
+        }
+        if (!quit_comp_thread) {
+            len = qemu_put_qemu_file(f, comp_param[idx].file);
+            bytes_transferred += len;
+        }
+    }
+}
+
+static inline void set_compress_params(CompressParam *param, RAMBlock *block,
+                                       ram_addr_t offset)
+{
+    param->block = block;
+    param->offset = offset;
+}
+
+static int compress_page_with_multi_thread(QEMUFile *f, RAMBlock *block,
+                                           ram_addr_t offset,
+                                           uint64_t *bytes_transferred)
+{
+    int idx, thread_count, bytes_xmit = -1, pages = -1;
+
+    thread_count = migrate_compress_threads();
+    qemu_mutex_lock(comp_done_lock);
+    while (true) {
+        for (idx = 0; idx < thread_count; idx++) {
+            if (comp_param[idx].done) {
+                bytes_xmit = qemu_put_qemu_file(f, comp_param[idx].file);
+                set_compress_params(&comp_param[idx], block, offset);
+                start_compression(&comp_param[idx]);
+                pages = 1;
+                acct_info.norm_pages++;
+                *bytes_transferred += bytes_xmit;
+                break;
+            }
+        }
+        if (pages > 0) {
+            break;
+        } else {
+            qemu_cond_wait(comp_done_cond, comp_done_lock);
+        }
+    }
+    qemu_mutex_unlock(comp_done_lock);
+
+    return pages;
+}
+
+/**
+ * ram_save_compressed_page: compress the given page and send it to the stream
+ *
+ * Returns: Number of pages written.
+ *
+ * @f: QEMUFile where to send the data
+ * @block: block that contains the page we want to send
+ * @offset: offset inside the block for the page
+ * @last_stage: if we are at the completion stage
+ * @bytes_transferred: increase it with the number of transferred bytes
+ */
+static int ram_save_compressed_page(QEMUFile *f, RAMBlock *block,
+                                    ram_addr_t offset, bool last_stage,
+                                    uint64_t *bytes_transferred)
+{
+    int pages = -1;
+    uint64_t bytes_xmit;
+    MemoryRegion *mr = block->mr;
+    uint8_t *p;
+    int ret;
+
+    p = memory_region_get_ram_ptr(mr) + offset;
+
+    bytes_xmit = 0;
+    ret = ram_control_save_page(f, block->offset,
+                                offset, TARGET_PAGE_SIZE, &bytes_xmit);
+    if (bytes_xmit) {
+        *bytes_transferred += bytes_xmit;
+        pages = 1;
+    }
+    if (block == last_sent_block) {
+        offset |= RAM_SAVE_FLAG_CONTINUE;
+    }
+    if (ret != RAM_SAVE_CONTROL_NOT_SUPP) {
+        if (ret != RAM_SAVE_CONTROL_DELAYED) {
+            if (bytes_xmit > 0) {
+                acct_info.norm_pages++;
+            } else if (bytes_xmit == 0) {
+                acct_info.dup_pages++;
+            }
+        }
+    } else {
+        /* When starting the process of a new block, the first page of
+         * the block should be sent out before other pages in the same
+         * block, and all the pages in last block should have been sent
+         * out, keeping this order is important, because the 'cont' flag
+         * is used to avoid resending the block name.
+         */
+        if (block != last_sent_block) {
+            flush_compressed_data(f);
+            pages = save_zero_page(f, block, offset, p, bytes_transferred);
+            if (pages == -1) {
+                set_compress_params(&comp_param[0], block, offset);
+                /* Use the qemu thread to compress the data to make sure the
+                 * first page is sent out before other pages
+                 */
+                bytes_xmit = do_compress_ram_page(&comp_param[0]);
+                acct_info.norm_pages++;
+                qemu_put_qemu_file(f, comp_param[0].file);
+                *bytes_transferred += bytes_xmit;
+                pages = 1;
+            }
+        } else {
+            pages = save_zero_page(f, block, offset, p, bytes_transferred);
+            if (pages == -1) {
+                pages = compress_page_with_multi_thread(f, block, offset,
+                                                        bytes_transferred);
+            }
+        }
+    }
+
+    return pages;
+}
+
+/**
+ * ram_find_and_save_block: Finds a dirty page and sends it to f
+ *
+ * Called within an RCU critical section.
+ *
+ * Returns:  The number of pages written
+ *           0 means no dirty pages
+ *
+ * @f: QEMUFile where to send the data
+ * @last_stage: if we are at the completion stage
+ * @bytes_transferred: increase it with the number of transferred bytes
+ */
+
+static int ram_find_and_save_block(QEMUFile *f, bool last_stage,
+                                   uint64_t *bytes_transferred)
+{
+    RAMBlock *block = last_seen_block;
+    ram_addr_t offset = last_offset;
+    bool complete_round = false;
+    int pages = 0;
+    MemoryRegion *mr;
+
+    if (!block)
+        block = QLIST_FIRST_RCU(&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->used_length) {
+            offset = 0;
+            block = QLIST_NEXT_RCU(block, next);
+            if (!block) {
+                block = QLIST_FIRST_RCU(&ram_list.blocks);
+                complete_round = true;
+                ram_bulk_stage = false;
+                if (migrate_use_xbzrle()) {
+                    /* If xbzrle is on, stop using the data compression at this
+                     * point. In theory, xbzrle can do better than compression.
+                     */
+                    flush_compressed_data(f);
+                    compression_switch = false;
+                }
+            }
+        } else {
+            if (compression_switch && migrate_use_compression()) {
+                pages = ram_save_compressed_page(f, block, offset, last_stage,
+                                                 bytes_transferred);
+            } else {
+                pages = ram_save_page(f, block, offset, last_stage,
+                                      bytes_transferred);
+            }
+
+            /* if page is unmodified, continue to the next */
+            if (pages > 0) {
+                last_sent_block = block;
+                break;
+            }
+        }
+    }
+
+    last_seen_block = block;
+    last_offset = offset;
+
+    return pages;
+}
+
+void acct_update_position(QEMUFile *f, size_t size, bool zero)
+{
+    uint64_t pages = size / TARGET_PAGE_SIZE;
+    if (zero) {
+        acct_info.dup_pages += pages;
+    } else {
+        acct_info.norm_pages += pages;
+        bytes_transferred += size;
+        qemu_update_position(f, size);
+    }
+}
+
+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;
+
+    rcu_read_lock();
+    QLIST_FOREACH_RCU(block, &ram_list.blocks, next)
+        total += block->used_length;
+    rcu_read_unlock();
+    return total;
+}
+
+void free_xbzrle_decoded_buf(void)
+{
+    g_free(xbzrle_decoded_buf);
+    xbzrle_decoded_buf = NULL;
+}
+
+static void migration_end(void)
+{
+    if (migration_bitmap) {
+        memory_global_dirty_log_stop();
+        g_free(migration_bitmap);
+        migration_bitmap = NULL;
+    }
+
+    XBZRLE_cache_lock();
+    if (XBZRLE.cache) {
+        cache_fini(XBZRLE.cache);
+        g_free(XBZRLE.encoded_buf);
+        g_free(XBZRLE.current_buf);
+        XBZRLE.cache = NULL;
+        XBZRLE.encoded_buf = NULL;
+        XBZRLE.current_buf = NULL;
+    }
+    XBZRLE_cache_unlock();
+}
+
+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;
+    ram_bulk_stage = true;
+}
+
+#define MAX_WAIT 50 /* ms, half buffered_file limit */
+
+
+/* Each of ram_save_setup, ram_save_iterate and ram_save_complete has
+ * long-running RCU critical section.  When rcu-reclaims in the code
+ * start to become numerous it will be necessary to reduce the
+ * granularity of these critical sections.
+ */
+
+static int ram_save_setup(QEMUFile *f, void *opaque)
+{
+    RAMBlock *block;
+    int64_t ram_bitmap_pages; /* Size of bitmap in pages, including gaps */
+
+    mig_throttle_on = false;
+    dirty_rate_high_cnt = 0;
+    bitmap_sync_count = 0;
+    migration_bitmap_sync_init();
+
+    if (migrate_use_xbzrle()) {
+        XBZRLE_cache_lock();
+        XBZRLE.cache = cache_init(migrate_xbzrle_cache_size() /
+                                  TARGET_PAGE_SIZE,
+                                  TARGET_PAGE_SIZE);
+        if (!XBZRLE.cache) {
+            XBZRLE_cache_unlock();
+            error_report("Error creating cache");
+            return -1;
+        }
+        XBZRLE_cache_unlock();
+
+        /* We prefer not to abort if there is no memory */
+        XBZRLE.encoded_buf = g_try_malloc0(TARGET_PAGE_SIZE);
+        if (!XBZRLE.encoded_buf) {
+            error_report("Error allocating encoded_buf");
+            return -1;
+        }
+
+        XBZRLE.current_buf = g_try_malloc(TARGET_PAGE_SIZE);
+        if (!XBZRLE.current_buf) {
+            error_report("Error allocating current_buf");
+            g_free(XBZRLE.encoded_buf);
+            XBZRLE.encoded_buf = NULL;
+            return -1;
+        }
+
+        acct_clear();
+    }
+
+    /* iothread lock needed for ram_list.dirty_memory[] */
+    qemu_mutex_lock_iothread();
+    qemu_mutex_lock_ramlist();
+    rcu_read_lock();
+    bytes_transferred = 0;
+    reset_ram_globals();
+
+    ram_bitmap_pages = last_ram_offset() >> TARGET_PAGE_BITS;
+    migration_bitmap = bitmap_new(ram_bitmap_pages);
+    bitmap_set(migration_bitmap, 0, ram_bitmap_pages);
+
+    /*
+     * Count the total number of pages used by ram blocks not including any
+     * gaps due to alignment or unplugs.
+     */
+    migration_dirty_pages = ram_bytes_total() >> TARGET_PAGE_BITS;
+
+    memory_global_dirty_log_start();
+    migration_bitmap_sync();
+    qemu_mutex_unlock_ramlist();
+    qemu_mutex_unlock_iothread();
+
+    qemu_put_be64(f, ram_bytes_total() | RAM_SAVE_FLAG_MEM_SIZE);
+
+    QLIST_FOREACH_RCU(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->used_length);
+    }
+
+    rcu_read_unlock();
+
+    ram_control_before_iterate(f, RAM_CONTROL_SETUP);
+    ram_control_after_iterate(f, RAM_CONTROL_SETUP);
+
+    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 pages_sent = 0;
+
+    rcu_read_lock();
+    if (ram_list.version != last_version) {
+        reset_ram_globals();
+    }
+
+    /* Read version before ram_list.blocks */
+    smp_rmb();
+
+    ram_control_before_iterate(f, RAM_CONTROL_ROUND);
+
+    t0 = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
+    i = 0;
+    while ((ret = qemu_file_rate_limit(f)) == 0) {
+        int pages;
+
+        pages = ram_find_and_save_block(f, false, &bytes_transferred);
+        /* no more pages to sent */
+        if (pages == 0) {
+            break;
+        }
+        pages_sent += pages;
+        acct_info.iterations++;
+        check_guest_throttling();
+        /* 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_clock_get_ns(QEMU_CLOCK_REALTIME) - t0) / 1000000;
+            if (t1 > MAX_WAIT) {
+                DPRINTF("big wait: %" PRIu64 " milliseconds, %d iterations\n",
+                        t1, i);
+                break;
+            }
+        }
+        i++;
+    }
+    flush_compressed_data(f);
+    rcu_read_unlock();
+
+    /*
+     * Must occur before EOS (or any QEMUFile operation)
+     * because of RDMA protocol.
+     */
+    ram_control_after_iterate(f, RAM_CONTROL_ROUND);
+
+    qemu_put_be64(f, RAM_SAVE_FLAG_EOS);
+    bytes_transferred += 8;
+
+    ret = qemu_file_get_error(f);
+    if (ret < 0) {
+        return ret;
+    }
+
+    return pages_sent;
+}
+
+/* Called with iothread lock */
+static int ram_save_complete(QEMUFile *f, void *opaque)
+{
+    rcu_read_lock();
+
+    migration_bitmap_sync();
+
+    ram_control_before_iterate(f, RAM_CONTROL_FINISH);
+
+    /* try transferring iterative blocks of memory */
+
+    /* flush all remaining blocks regardless of rate limiting */
+    while (true) {
+        int pages;
+
+        pages = ram_find_and_save_block(f, true, &bytes_transferred);
+        /* no more blocks to sent */
+        if (pages == 0) {
+            break;
+        }
+    }
+
+    flush_compressed_data(f);
+    ram_control_after_iterate(f, RAM_CONTROL_FINISH);
+    migration_end();
+
+    rcu_read_unlock();
+    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();
+        rcu_read_lock();
+        migration_bitmap_sync();
+        rcu_read_unlock();
+        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)
+{
+    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) {
+        error_report("Failed to load XBZRLE page - wrong compression!");
+        return -1;
+    }
+
+    if (xh_len > TARGET_PAGE_SIZE) {
+        error_report("Failed to load XBZRLE page - len overflow!");
+        return -1;
+    }
+    /* load data and decode */
+    qemu_get_buffer(f, xbzrle_decoded_buf, xh_len);
+
+    /* decode RLE */
+    if (xbzrle_decode_buffer(xbzrle_decoded_buf, xh_len, host,
+                             TARGET_PAGE_SIZE) == -1) {
+        error_report("Failed to load XBZRLE page - decode error!");
+        return -1;
+    }
+
+    return 0;
+}
+
+/* Must be called from within a rcu critical section.
+ * Returns a pointer from within the RCU-protected ram_list.
+ */
+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 || block->max_length <= offset) {
+            error_report("Ack, bad migration stream!");
+            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;
+
+    QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
+        if (!strncmp(id, block->idstr, sizeof(id)) &&
+            block->max_length > offset) {
+            return memory_region_get_ram_ptr(block->mr) + offset;
+        }
+    }
+
+    error_report("Can't find block %s!", id);
+    return NULL;
+}
+
+/*
+ * If a page (or a whole RDMA chunk) has been
+ * determined to be zero, then zap it.
+ */
+void ram_handle_compressed(void *host, uint8_t ch, uint64_t size)
+{
+    if (ch != 0 || !is_zero_range(host, size)) {
+        memset(host, ch, size);
+    }
+}
+
+static void *do_data_decompress(void *opaque)
+{
+    DecompressParam *param = opaque;
+    unsigned long pagesize;
+
+    while (!quit_decomp_thread) {
+        qemu_mutex_lock(&param->mutex);
+        while (!param->start && !quit_decomp_thread) {
+            qemu_cond_wait(&param->cond, &param->mutex);
+            pagesize = TARGET_PAGE_SIZE;
+            if (!quit_decomp_thread) {
+                /* uncompress() will return failed in some case, especially
+                 * when the page is dirted when doing the compression, it's
+                 * not a problem because the dirty page will be retransferred
+                 * and uncompress() won't break the data in other pages.
+                 */
+                uncompress((Bytef *)param->des, &pagesize,
+                           (const Bytef *)param->compbuf, param->len);
+            }
+            param->start = false;
+        }
+        qemu_mutex_unlock(&param->mutex);
+    }
+
+    return NULL;
+}
+
+void migrate_decompress_threads_create(void)
+{
+    int i, thread_count;
+
+    thread_count = migrate_decompress_threads();
+    decompress_threads = g_new0(QemuThread, thread_count);
+    decomp_param = g_new0(DecompressParam, thread_count);
+    compressed_data_buf = g_malloc0(compressBound(TARGET_PAGE_SIZE));
+    quit_decomp_thread = false;
+    for (i = 0; i < thread_count; i++) {
+        qemu_mutex_init(&decomp_param[i].mutex);
+        qemu_cond_init(&decomp_param[i].cond);
+        decomp_param[i].compbuf = g_malloc0(compressBound(TARGET_PAGE_SIZE));
+        qemu_thread_create(decompress_threads + i, "decompress",
+                           do_data_decompress, decomp_param + i,
+                           QEMU_THREAD_JOINABLE);
+    }
+}
+
+void migrate_decompress_threads_join(void)
+{
+    int i, thread_count;
+
+    quit_decomp_thread = true;
+    thread_count = migrate_decompress_threads();
+    for (i = 0; i < thread_count; i++) {
+        qemu_mutex_lock(&decomp_param[i].mutex);
+        qemu_cond_signal(&decomp_param[i].cond);
+        qemu_mutex_unlock(&decomp_param[i].mutex);
+    }
+    for (i = 0; i < thread_count; i++) {
+        qemu_thread_join(decompress_threads + i);
+        qemu_mutex_destroy(&decomp_param[i].mutex);
+        qemu_cond_destroy(&decomp_param[i].cond);
+        g_free(decomp_param[i].compbuf);
+    }
+    g_free(decompress_threads);
+    g_free(decomp_param);
+    g_free(compressed_data_buf);
+    decompress_threads = NULL;
+    decomp_param = NULL;
+    compressed_data_buf = NULL;
+}
+
+static void decompress_data_with_multi_threads(uint8_t *compbuf,
+                                               void *host, int len)
+{
+    int idx, thread_count;
+
+    thread_count = migrate_decompress_threads();
+    while (true) {
+        for (idx = 0; idx < thread_count; idx++) {
+            if (!decomp_param[idx].start) {
+                memcpy(decomp_param[idx].compbuf, compbuf, len);
+                decomp_param[idx].des = host;
+                decomp_param[idx].len = len;
+                start_decompression(&decomp_param[idx]);
+                break;
+            }
+        }
+        if (idx < thread_count) {
+            break;
+        }
+    }
+}
+
+static int ram_load(QEMUFile *f, void *opaque, int version_id)
+{
+    int flags = 0, ret = 0;
+    static uint64_t seq_iter;
+    int len = 0;
+
+    seq_iter++;
+
+    if (version_id != 4) {
+        ret = -EINVAL;
+    }
+
+    /* This RCU critical section can be very long running.
+     * When RCU reclaims in the code start to become numerous,
+     * it will be necessary to reduce the granularity of this
+     * critical section.
+     */
+    rcu_read_lock();
+    while (!ret && !(flags & RAM_SAVE_FLAG_EOS)) {
+        ram_addr_t addr, total_ram_bytes;
+        void *host;
+        uint8_t ch;
+
+        addr = qemu_get_be64(f);
+        flags = addr & ~TARGET_PAGE_MASK;
+        addr &= TARGET_PAGE_MASK;
+
+        switch (flags & ~RAM_SAVE_FLAG_CONTINUE) {
+        case RAM_SAVE_FLAG_MEM_SIZE:
+            /* Synchronize RAM block list */
+            total_ram_bytes = addr;
+            while (!ret && total_ram_bytes) {
+                RAMBlock *block;
+                uint8_t len;
+                char id[256];
+                ram_addr_t length;
+
+                len = qemu_get_byte(f);
+                qemu_get_buffer(f, (uint8_t *)id, len);
+                id[len] = 0;
+                length = qemu_get_be64(f);
+
+                QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
+                    if (!strncmp(id, block->idstr, sizeof(id))) {
+                        if (length != block->used_length) {
+                            Error *local_err = NULL;
+
+                            ret = qemu_ram_resize(block->offset, length, &local_err);
+                            if (local_err) {
+                                error_report_err(local_err);
+                            }
+                        }
+                        break;
+                    }
+                }
+
+                if (!block) {
+                    error_report("Unknown ramblock \"%s\", cannot "
+                                 "accept migration", id);
+                    ret = -EINVAL;
+                }
+
+                total_ram_bytes -= length;
+            }
+            break;
+        case RAM_SAVE_FLAG_COMPRESS:
+            host = host_from_stream_offset(f, addr, flags);
+            if (!host) {
+                error_report("Illegal RAM offset " RAM_ADDR_FMT, addr);
+                ret = -EINVAL;
+                break;
+            }
+            ch = qemu_get_byte(f);
+            ram_handle_compressed(host, ch, TARGET_PAGE_SIZE);
+            break;
+        case RAM_SAVE_FLAG_PAGE:
+            host = host_from_stream_offset(f, addr, flags);
+            if (!host) {
+                error_report("Illegal RAM offset " RAM_ADDR_FMT, addr);
+                ret = -EINVAL;
+                break;
+            }
+            qemu_get_buffer(f, host, TARGET_PAGE_SIZE);
+            break;
+        case RAM_SAVE_FLAG_COMPRESS_PAGE:
+            host = host_from_stream_offset(f, addr, flags);
+            if (!host) {
+                error_report("Invalid RAM offset " RAM_ADDR_FMT, addr);
+                ret = -EINVAL;
+                break;
+            }
+
+            len = qemu_get_be32(f);
+            if (len < 0 || len > compressBound(TARGET_PAGE_SIZE)) {
+                error_report("Invalid compressed data length: %d", len);
+                ret = -EINVAL;
+                break;
+            }
+            qemu_get_buffer(f, compressed_data_buf, len);
+            decompress_data_with_multi_threads(compressed_data_buf, host, len);
+            break;
+        case RAM_SAVE_FLAG_XBZRLE:
+            host = host_from_stream_offset(f, addr, flags);
+            if (!host) {
+                error_report("Illegal RAM offset " RAM_ADDR_FMT, addr);
+                ret = -EINVAL;
+                break;
+            }
+            if (load_xbzrle(f, addr, host) < 0) {
+                error_report("Failed to decompress XBZRLE page at "
+                             RAM_ADDR_FMT, addr);
+                ret = -EINVAL;
+                break;
+            }
+            break;
+        case RAM_SAVE_FLAG_EOS:
+            /* normal exit */
+            break;
+        default:
+            if (flags & RAM_SAVE_FLAG_HOOK) {
+                ram_control_load_hook(f, flags);
+            } else {
+                error_report("Unknown combination of migration flags: %#x",
+                             flags);
+                ret = -EINVAL;
+            }
+        }
+        if (!ret) {
+            ret = qemu_file_get_error(f);
+        }
+    }
+
+    rcu_read_unlock();
+    DPRINTF("Completed load of VM with exit code %d seq iteration "
+            "%" PRIu64 "\n", ret, seq_iter);
+    return ret;
+}
+
+static 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,
+};
+
+void ram_mig_init(void)
+{
+    qemu_mutex_init(&XBZRLE.lock);
+    register_savevm_live(NULL, "ram", 0, 4, &savevm_ram_handlers, NULL);
+}
+/* Stub function that's gets run on the vcpu when its brought out of the
+   VM to run inside qemu via async_run_on_cpu()*/
+
+static void mig_sleep_cpu(void *opq)
+{
+    qemu_mutex_unlock_iothread();
+    g_usleep(30*1000);
+    qemu_mutex_lock_iothread();
+}
+
+/* To reduce the dirty rate explicitly disallow the VCPUs from spending
+   much time in the VM. The migration thread will try to catchup.
+   Workload will experience a performance drop.
+*/
+static void mig_throttle_guest_down(void)
+{
+    CPUState *cpu;
+
+    qemu_mutex_lock_iothread();
+    CPU_FOREACH(cpu) {
+        async_run_on_cpu(cpu, mig_sleep_cpu, NULL);
+    }
+    qemu_mutex_unlock_iothread();
+}
+
+static void check_guest_throttling(void)
+{
+    static int64_t t0;
+    int64_t        t1;
+
+    if (!mig_throttle_on) {
+        return;
+    }
+
+    if (!t0)  {
+        t0 = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
+        return;
+    }
+
+    t1 = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
+
+    /* If it has been more than 40 ms since the last time the guest
+     * was throttled then do it again.
+     */
+    if (40 < (t1-t0)/1000000) {
+        mig_throttle_guest_down();
+        t0 = t1;
+    }
+}