Archipelago » qemu

/*

 * QEMU live block migration

 *

 * Copyright IBM, Corp. 2009

 *

 * Authors:

 *  Liran Schour   <lirans@il.ibm.com>

 *

 * This work is licensed under the terms of the GNU GPL, version 2.  See

 * the COPYING file in the top-level directory.

 *

 */

#include "qemu-common.h"

#include "block_int.h"

#include "hw/hw.h"

#include "qemu-queue.h"

#include "qemu-timer.h"

#include "monitor.h"

#include "block-migration.h"

#include "migration.h"

#include "blockdev.h"

#include <assert.h>

#define BLOCK_SIZE (BDRV_SECTORS_PER_DIRTY_CHUNK << BDRV_SECTOR_BITS)

#define BLK_MIG_FLAG_DEVICE_BLOCK       0x01

#define BLK_MIG_FLAG_EOS                0x02

#define BLK_MIG_FLAG_PROGRESS           0x04

#define MAX_IS_ALLOCATED_SEARCH 65536

//#define DEBUG_BLK_MIGRATION

#ifdef DEBUG_BLK_MIGRATION

#define DPRINTF(fmt, ...) \

    do { printf("blk_migration: " fmt, ## __VA_ARGS__); } while (0)

#else

#define DPRINTF(fmt, ...) \

    do { } while (0)

#endif

typedef struct BlkMigDevState {

    BlockDriverState *bs;

    int bulk_completed;

    int shared_base;

    int64_t cur_sector;

    int64_t cur_dirty;

    int64_t completed_sectors;

    int64_t total_sectors;

    int64_t dirty;

    QSIMPLEQ_ENTRY(BlkMigDevState) entry;

    unsigned long *aio_bitmap;

} BlkMigDevState;

typedef struct BlkMigBlock {

    uint8_t *buf;

    BlkMigDevState *bmds;

    int64_t sector;

    int nr_sectors;

    struct iovec iov;

    QEMUIOVector qiov;

    BlockDriverAIOCB *aiocb;

    int ret;

    int64_t time;

    QSIMPLEQ_ENTRY(BlkMigBlock) entry;

} BlkMigBlock;

typedef struct BlkMigState {

    int blk_enable;

    int shared_base;

    QSIMPLEQ_HEAD(bmds_list, BlkMigDevState) bmds_list;

    QSIMPLEQ_HEAD(blk_list, BlkMigBlock) blk_list;

    int submitted;

    int read_done;

    int transferred;

    int64_t total_sector_sum;

    int prev_progress;

    int bulk_completed;

    long double total_time;

    int reads;

} BlkMigState;

static BlkMigState block_mig_state;

static void blk_send(QEMUFile *f, BlkMigBlock * blk)

{

    int len;

    /* sector number and flags */

    qemu_put_be64(f, (blk->sector << BDRV_SECTOR_BITS)

                     | BLK_MIG_FLAG_DEVICE_BLOCK);

    /* device name */

    len = strlen(blk->bmds->bs->device_name);

    qemu_put_byte(f, len);

    qemu_put_buffer(f, (uint8_t *)blk->bmds->bs->device_name, len);

    qemu_put_buffer(f, blk->buf, BLOCK_SIZE);

}

int blk_mig_active(void)

{

    return !QSIMPLEQ_EMPTY(&block_mig_state.bmds_list);

}

uint64_t blk_mig_bytes_transferred(void)

{

    BlkMigDevState *bmds;

    uint64_t sum = 0;

    QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {

        sum += bmds->completed_sectors;

    }

    return sum << BDRV_SECTOR_BITS;

}

uint64_t blk_mig_bytes_remaining(void)

{

    return blk_mig_bytes_total() - blk_mig_bytes_transferred();

}

uint64_t blk_mig_bytes_total(void)

{

    BlkMigDevState *bmds;

    uint64_t sum = 0;

    QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {

        sum += bmds->total_sectors;

    }

    return sum << BDRV_SECTOR_BITS;

}

static inline void add_avg_read_time(int64_t time)

{

    block_mig_state.reads++;

    block_mig_state.total_time += time;

}

static inline long double compute_read_bwidth(void)

{

    assert(block_mig_state.total_time != 0);

    return  (block_mig_state.reads * BLOCK_SIZE)/ block_mig_state.total_time;

}

static int bmds_aio_inflight(BlkMigDevState *bmds, int64_t sector)

{

    int64_t chunk = sector / (int64_t)BDRV_SECTORS_PER_DIRTY_CHUNK;

    if ((sector << BDRV_SECTOR_BITS) < bdrv_getlength(bmds->bs)) {

        return !!(bmds->aio_bitmap[chunk / (sizeof(unsigned long) * 8)] &

            (1UL << (chunk % (sizeof(unsigned long) * 8))));

    } else {

        return 0;

    }

}

static void bmds_set_aio_inflight(BlkMigDevState *bmds, int64_t sector_num,

                             int nb_sectors, int set)

{

    int64_t start, end;

    unsigned long val, idx, bit;

    start = sector_num / BDRV_SECTORS_PER_DIRTY_CHUNK;

    end = (sector_num + nb_sectors - 1) / BDRV_SECTORS_PER_DIRTY_CHUNK;

    for (; start <= end; start++) {

        idx = start / (sizeof(unsigned long) * 8);

        bit = start % (sizeof(unsigned long) * 8);

        val = bmds->aio_bitmap[idx];

        if (set) {

            val |= 1UL << bit;

        } else {

            val &= ~(1UL << bit);

        }

        bmds->aio_bitmap[idx] = val;

    }

}

static void alloc_aio_bitmap(BlkMigDevState *bmds)

{

    BlockDriverState *bs = bmds->bs;

    int64_t bitmap_size;

    bitmap_size = (bdrv_getlength(bs) >> BDRV_SECTOR_BITS) +

            BDRV_SECTORS_PER_DIRTY_CHUNK * 8 - 1;

    bitmap_size /= BDRV_SECTORS_PER_DIRTY_CHUNK * 8;

    bmds->aio_bitmap = qemu_mallocz(bitmap_size);

}

static void blk_mig_read_cb(void *opaque, int ret)

{

    BlkMigBlock *blk = opaque;

    blk->ret = ret;

    blk->time = qemu_get_clock_ns(rt_clock) - blk->time;

    add_avg_read_time(blk->time);

    QSIMPLEQ_INSERT_TAIL(&block_mig_state.blk_list, blk, entry);

    bmds_set_aio_inflight(blk->bmds, blk->sector, blk->nr_sectors, 0);

    block_mig_state.submitted--;

    block_mig_state.read_done++;

    assert(block_mig_state.submitted >= 0);

}

static int mig_save_device_bulk(Monitor *mon, QEMUFile *f,

                                BlkMigDevState *bmds)

{

    int64_t total_sectors = bmds->total_sectors;

    int64_t cur_sector = bmds->cur_sector;

    BlockDriverState *bs = bmds->bs;

    BlkMigBlock *blk;

    int nr_sectors;

    if (bmds->shared_base) {

        while (cur_sector < total_sectors &&

               !bdrv_is_allocated(bs, cur_sector, MAX_IS_ALLOCATED_SEARCH,

                                  &nr_sectors)) {

            cur_sector += nr_sectors;

        }

    }

    if (cur_sector >= total_sectors) {

        bmds->cur_sector = bmds->completed_sectors = total_sectors;

        return 1;

    }

    bmds->completed_sectors = cur_sector;

    cur_sector &= ~((int64_t)BDRV_SECTORS_PER_DIRTY_CHUNK - 1);

    /* we are going to transfer a full block even if it is not allocated */

    nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;

    if (total_sectors - cur_sector < BDRV_SECTORS_PER_DIRTY_CHUNK) {

        nr_sectors = total_sectors - cur_sector;

    }

    blk = qemu_malloc(sizeof(BlkMigBlock));

    blk->buf = qemu_malloc(BLOCK_SIZE);

    blk->bmds = bmds;

    blk->sector = cur_sector;

    blk->nr_sectors = nr_sectors;

    blk->iov.iov_base = blk->buf;

    blk->iov.iov_len = nr_sectors * BDRV_SECTOR_SIZE;

    qemu_iovec_init_external(&blk->qiov, &blk->iov, 1);

    blk->time = qemu_get_clock_ns(rt_clock);

    blk->aiocb = bdrv_aio_readv(bs, cur_sector, &blk->qiov,

                                nr_sectors, blk_mig_read_cb, blk);

    if (!blk->aiocb) {

        goto error;

    }

    block_mig_state.submitted++;

    bdrv_reset_dirty(bs, cur_sector, nr_sectors);

    bmds->cur_sector = cur_sector + nr_sectors;

    return (bmds->cur_sector >= total_sectors);

error:

    monitor_printf(mon, "Error reading sector %" PRId64 "\n", cur_sector);

    qemu_file_set_error(f);

    qemu_free(blk->buf);

    qemu_free(blk);

    return 0;

}

static void set_dirty_tracking(int enable)

{

    BlkMigDevState *bmds;

    QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {

        bdrv_set_dirty_tracking(bmds->bs, enable);

    }

}

static void init_blk_migration_it(void *opaque, BlockDriverState *bs)

{

    Monitor *mon = opaque;

    BlkMigDevState *bmds;

    int64_t sectors;

    if (!bdrv_is_read_only(bs)) {

        sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;

        if (sectors <= 0) {

            return;

        }

        bmds = qemu_mallocz(sizeof(BlkMigDevState));

        bmds->bs = bs;

        bmds->bulk_completed = 0;

        bmds->total_sectors = sectors;

        bmds->completed_sectors = 0;

        bmds->shared_base = block_mig_state.shared_base;

        alloc_aio_bitmap(bmds);

        drive_get_ref(drive_get_by_blockdev(bs));

        bdrv_set_in_use(bs, 1);

        block_mig_state.total_sector_sum += sectors;

        if (bmds->shared_base) {

            monitor_printf(mon, "Start migration for %s with shared base "

                                "image\n",

                           bs->device_name);

        } else {

            monitor_printf(mon, "Start full migration for %s\n",

                           bs->device_name);

        }

        QSIMPLEQ_INSERT_TAIL(&block_mig_state.bmds_list, bmds, entry);

    }

}

static void init_blk_migration(Monitor *mon, QEMUFile *f)

{

    block_mig_state.submitted = 0;

    block_mig_state.read_done = 0;

    block_mig_state.transferred = 0;

    block_mig_state.total_sector_sum = 0;

    block_mig_state.prev_progress = -1;

    block_mig_state.bulk_completed = 0;

    block_mig_state.total_time = 0;

    block_mig_state.reads = 0;

    bdrv_iterate(init_blk_migration_it, mon);

}

static int blk_mig_save_bulked_block(Monitor *mon, QEMUFile *f)

{

    int64_t completed_sector_sum = 0;

    BlkMigDevState *bmds;

    int progress;

    int ret = 0;

    QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {

        if (bmds->bulk_completed == 0) {

            if (mig_save_device_bulk(mon, f, bmds) == 1) {

                /* completed bulk section for this device */

                bmds->bulk_completed = 1;

            }

            completed_sector_sum += bmds->completed_sectors;

            ret = 1;

            break;

        } else {

            completed_sector_sum += bmds->completed_sectors;

        }

    }

    if (block_mig_state.total_sector_sum != 0) {

        progress = completed_sector_sum * 100 /

                   block_mig_state.total_sector_sum;

    } else {

        progress = 100;

    }

    if (progress != block_mig_state.prev_progress) {

        block_mig_state.prev_progress = progress;

        qemu_put_be64(f, (progress << BDRV_SECTOR_BITS)

                         | BLK_MIG_FLAG_PROGRESS);

        monitor_printf(mon, "Completed %d %%\r", progress);

        monitor_flush(mon);

    }

    return ret;

}

static void blk_mig_reset_dirty_cursor(void)

{

    BlkMigDevState *bmds;

    QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {

        bmds->cur_dirty = 0;

    }

}

static int mig_save_device_dirty(Monitor *mon, QEMUFile *f,

                                 BlkMigDevState *bmds, int is_async)

{

    BlkMigBlock *blk;

    int64_t total_sectors = bmds->total_sectors;

    int64_t sector;

    int nr_sectors;

    for (sector = bmds->cur_dirty; sector < bmds->total_sectors;) {

        if (bmds_aio_inflight(bmds, sector)) {

            qemu_aio_flush();

        }

        if (bdrv_get_dirty(bmds->bs, sector)) {

            if (total_sectors - sector < BDRV_SECTORS_PER_DIRTY_CHUNK) {

                nr_sectors = total_sectors - sector;

            } else {

                nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;

            }

            blk = qemu_malloc(sizeof(BlkMigBlock));

            blk->buf = qemu_malloc(BLOCK_SIZE);

            blk->bmds = bmds;

            blk->sector = sector;

            blk->nr_sectors = nr_sectors;

            if (is_async) {

                blk->iov.iov_base = blk->buf;

                blk->iov.iov_len = nr_sectors * BDRV_SECTOR_SIZE;

                qemu_iovec_init_external(&blk->qiov, &blk->iov, 1);

                blk->time = qemu_get_clock_ns(rt_clock);

                blk->aiocb = bdrv_aio_readv(bmds->bs, sector, &blk->qiov,

                                            nr_sectors, blk_mig_read_cb, blk);

                if (!blk->aiocb) {

                    goto error;

                }

                block_mig_state.submitted++;

                bmds_set_aio_inflight(bmds, sector, nr_sectors, 1);

            } else {

                if (bdrv_read(bmds->bs, sector, blk->buf,

                              nr_sectors) < 0) {

                    goto error;

                }

                blk_send(f, blk);

                qemu_free(blk->buf);

                qemu_free(blk);

            }

            bdrv_reset_dirty(bmds->bs, sector, nr_sectors);

            break;

        }

        sector += BDRV_SECTORS_PER_DIRTY_CHUNK;

        bmds->cur_dirty = sector;

    }

    return (bmds->cur_dirty >= bmds->total_sectors);

error:

    monitor_printf(mon, "Error reading sector %" PRId64 "\n", sector);

    qemu_file_set_error(f);

    qemu_free(blk->buf);

    qemu_free(blk);

    return 0;

}

static int blk_mig_save_dirty_block(Monitor *mon, QEMUFile *f, int is_async)

{

    BlkMigDevState *bmds;

    int ret = 0;

    QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {

        if (mig_save_device_dirty(mon, f, bmds, is_async) == 0) {

            ret = 1;

            break;

        }

    }

    return ret;

}

static void flush_blks(QEMUFile* f)

{

    BlkMigBlock *blk;

    DPRINTF("%s Enter submitted %d read_done %d transferred %d\n",

            __FUNCTION__, block_mig_state.submitted, block_mig_state.read_done,

            block_mig_state.transferred);

    while ((blk = QSIMPLEQ_FIRST(&block_mig_state.blk_list)) != NULL) {

        if (qemu_file_rate_limit(f)) {

            break;

        }

        if (blk->ret < 0) {

            qemu_file_set_error(f);

            break;

        }

        blk_send(f, blk);

        QSIMPLEQ_REMOVE_HEAD(&block_mig_state.blk_list, entry);

        qemu_free(blk->buf);

        qemu_free(blk);

        block_mig_state.read_done--;

        block_mig_state.transferred++;

        assert(block_mig_state.read_done >= 0);

    }

    DPRINTF("%s Exit submitted %d read_done %d transferred %d\n", __FUNCTION__,

            block_mig_state.submitted, block_mig_state.read_done,

            block_mig_state.transferred);

}

static int64_t get_remaining_dirty(void)

{

    BlkMigDevState *bmds;

    int64_t dirty = 0;

    QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {

        dirty += bdrv_get_dirty_count(bmds->bs);

    }

    return dirty * BLOCK_SIZE;

}

static int is_stage2_completed(void)

{

    int64_t remaining_dirty;

    long double bwidth;

    if (block_mig_state.bulk_completed == 1) {

        remaining_dirty = get_remaining_dirty();

        if (remaining_dirty == 0) {

            return 1;

        }

        bwidth = compute_read_bwidth();

        if ((remaining_dirty / bwidth) <=

            migrate_max_downtime()) {

            /* finish stage2 because we think that we can finish remaing work

               below max_downtime */

            return 1;

        }

    }

    return 0;

}

static void blk_mig_cleanup(Monitor *mon)

{

    BlkMigDevState *bmds;

    BlkMigBlock *blk;

    set_dirty_tracking(0);

    while ((bmds = QSIMPLEQ_FIRST(&block_mig_state.bmds_list)) != NULL) {

        QSIMPLEQ_REMOVE_HEAD(&block_mig_state.bmds_list, entry);

        bdrv_set_in_use(bmds->bs, 0);

        drive_put_ref(drive_get_by_blockdev(bmds->bs));

        qemu_free(bmds->aio_bitmap);

        qemu_free(bmds);

    }

    while ((blk = QSIMPLEQ_FIRST(&block_mig_state.blk_list)) != NULL) {

        QSIMPLEQ_REMOVE_HEAD(&block_mig_state.blk_list, entry);

        qemu_free(blk->buf);

        qemu_free(blk);

    }

    monitor_printf(mon, "\n");

}

static int block_save_live(Monitor *mon, QEMUFile *f, int stage, void *opaque)

{

    DPRINTF("Enter save live stage %d submitted %d transferred %d\n",

            stage, block_mig_state.submitted, block_mig_state.transferred);

    if (stage < 0) {

        blk_mig_cleanup(mon);

        return 0;

    }

    if (block_mig_state.blk_enable != 1) {

        /* no need to migrate storage */

        qemu_put_be64(f, BLK_MIG_FLAG_EOS);

        return 1;

    }

    if (stage == 1) {

        init_blk_migration(mon, f);

        /* start track dirty blocks */

        set_dirty_tracking(1);

    }

    flush_blks(f);

    if (qemu_file_has_error(f)) {

        blk_mig_cleanup(mon);

        return 0;

    }

    blk_mig_reset_dirty_cursor();

    if (stage == 2) {

        /* control the rate of transfer */

        while ((block_mig_state.submitted +

                block_mig_state.read_done) * BLOCK_SIZE <

               qemu_file_get_rate_limit(f)) {

            if (block_mig_state.bulk_completed == 0) {

                /* first finish the bulk phase */

                if (blk_mig_save_bulked_block(mon, f) == 0) {

                    /* finished saving bulk on all devices */

                    block_mig_state.bulk_completed = 1;

                }

            } else {

                if (blk_mig_save_dirty_block(mon, f, 1) == 0) {

                    /* no more dirty blocks */

                    break;

                }

            }

        }

        flush_blks(f);

        if (qemu_file_has_error(f)) {

            blk_mig_cleanup(mon);

            return 0;

        }

    }

    if (stage == 3) {

        /* we know for sure that save bulk is completed and

           all async read completed */

        assert(block_mig_state.submitted == 0);

        while (blk_mig_save_dirty_block(mon, f, 0) != 0);

        blk_mig_cleanup(mon);

        /* report completion */

        qemu_put_be64(f, (100 << BDRV_SECTOR_BITS) | BLK_MIG_FLAG_PROGRESS);

        if (qemu_file_has_error(f)) {

            return 0;

        }

        monitor_printf(mon, "Block migration completed\n");

    }

    qemu_put_be64(f, BLK_MIG_FLAG_EOS);

    return ((stage == 2) && is_stage2_completed());

}

static int block_load(QEMUFile *f, void *opaque, int version_id)

{

    static int banner_printed;

    int len, flags;

    char device_name[256];

    int64_t addr;

    BlockDriverState *bs, *bs_prev = NULL;

    uint8_t *buf;

    int64_t total_sectors = 0;

    int nr_sectors;

    do {

        addr = qemu_get_be64(f);

        flags = addr & ~BDRV_SECTOR_MASK;

        addr >>= BDRV_SECTOR_BITS;

        if (flags & BLK_MIG_FLAG_DEVICE_BLOCK) {

            int ret;

            /* get device name */

            len = qemu_get_byte(f);

            qemu_get_buffer(f, (uint8_t *)device_name, len);

            device_name[len] = '\0';

            bs = bdrv_find(device_name);

            if (!bs) {

                fprintf(stderr, "Error unknown block device %s\n",

                        device_name);

                return -EINVAL;

            }

            if (bs != bs_prev) {

                bs_prev = bs;

                total_sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;

                if (total_sectors <= 0) {

                    error_report("Error getting length of block device %s\n",

                                 device_name);

                    return -EINVAL;

                }

            }

            if (total_sectors - addr < BDRV_SECTORS_PER_DIRTY_CHUNK) {

                nr_sectors = total_sectors - addr;

            } else {

                nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;

            }

            buf = qemu_malloc(BLOCK_SIZE);

            qemu_get_buffer(f, buf, BLOCK_SIZE);

            ret = bdrv_write(bs, addr, buf, nr_sectors);

            qemu_free(buf);

            if (ret < 0) {

                return ret;

            }

        } else if (flags & BLK_MIG_FLAG_PROGRESS) {

            if (!banner_printed) {

                printf("Receiving block device images\n");

                banner_printed = 1;

            }

            printf("Completed %d %%%c", (int)addr,

                   (addr == 100) ? '\n' : '\r');

            fflush(stdout);

        } else if (!(flags & BLK_MIG_FLAG_EOS)) {

            fprintf(stderr, "Unknown flags\n");

            return -EINVAL;

        }

        if (qemu_file_has_error(f)) {

            return -EIO;

        }

    } while (!(flags & BLK_MIG_FLAG_EOS));

    return 0;

}

static void block_set_params(int blk_enable, int shared_base, void *opaque)

{

    block_mig_state.blk_enable = blk_enable;

    block_mig_state.shared_base = shared_base;

    /* shared base means that blk_enable = 1 */

    block_mig_state.blk_enable |= shared_base;

}

void blk_mig_init(void)

{

    QSIMPLEQ_INIT(&block_mig_state.bmds_list);

    QSIMPLEQ_INIT(&block_mig_state.blk_list);

    register_savevm_live(NULL, "block", 0, 1, block_set_params,

                         block_save_live, NULL, block_load, &block_mig_state);

}