/* * 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. * * Contributions after 2012-01-13 are licensed under the terms of the * GNU GPL, version 2 or (at your option) any later version. */ #include "qemu-common.h" #include "block/block_int.h" #include "hw/hw.h" #include "qemu/queue.h" #include "qemu/timer.h" #include "migration/block.h" #include "migration/migration.h" #include "sysemu/blockdev.h" #include <assert.h> #define BLOCK_SIZE (1 << 20) #define BDRV_SECTORS_PER_DIRTY_CHUNK (BLOCK_SIZE >> BDRV_SECTOR_BITS) #define BLK_MIG_FLAG_DEVICE_BLOCK 0x01 #define BLK_MIG_FLAG_EOS 0x02 #define BLK_MIG_FLAG_PROGRESS 0x04 #define BLK_MIG_FLAG_ZERO_BLOCK 0x08 #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 { /* Written during setup phase. Can be read without a lock. */ BlockDriverState *bs; int shared_base; int64_t total_sectors; QSIMPLEQ_ENTRY(BlkMigDevState) entry; /* Only used by migration thread. Does not need a lock. */ int bulk_completed; int64_t cur_sector; int64_t cur_dirty; /* Protected by block migration lock. */ unsigned long *aio_bitmap; int64_t completed_sectors; } BlkMigDevState; typedef struct BlkMigBlock { /* Only used by migration thread. */ uint8_t *buf; BlkMigDevState *bmds; int64_t sector; int nr_sectors; struct iovec iov; QEMUIOVector qiov; BlockDriverAIOCB *aiocb; /* Protected by block migration lock. */ int ret; QSIMPLEQ_ENTRY(BlkMigBlock) entry; } BlkMigBlock; typedef struct BlkMigState { /* Written during setup phase. Can be read without a lock. */ int blk_enable; int shared_base; QSIMPLEQ_HEAD(bmds_list, BlkMigDevState) bmds_list; int64_t total_sector_sum; bool zero_blocks; /* Protected by lock. */ QSIMPLEQ_HEAD(blk_list, BlkMigBlock) blk_list; int submitted; int read_done; /* Only used by migration thread. Does not need a lock. */ int transferred; int prev_progress; int bulk_completed; /* Lock must be taken _inside_ the iothread lock. */ QemuMutex lock; } BlkMigState; static BlkMigState block_mig_state; static void blk_mig_lock(void) { qemu_mutex_lock(&block_mig_state.lock); } static void blk_mig_unlock(void) { qemu_mutex_unlock(&block_mig_state.lock); } /* Must run outside of the iothread lock during the bulk phase, * or the VM will stall. */ static void blk_send(QEMUFile *f, BlkMigBlock * blk) { int len; uint64_t flags = BLK_MIG_FLAG_DEVICE_BLOCK; if (block_mig_state.zero_blocks && buffer_is_zero(blk->buf, BLOCK_SIZE)) { flags |= BLK_MIG_FLAG_ZERO_BLOCK; } /* sector number and flags */ qemu_put_be64(f, (blk->sector << BDRV_SECTOR_BITS) | flags); /* 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); /* if a block is zero we need to flush here since the network * bandwidth is now a lot higher than the storage device bandwidth. * thus if we queue zero blocks we slow down the migration */ if (flags & BLK_MIG_FLAG_ZERO_BLOCK) { qemu_fflush(f); return; } 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; blk_mig_lock(); QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) { sum += bmds->completed_sectors; } blk_mig_unlock(); 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; } /* Called with migration lock held. */ 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; } } /* Called with migration lock held. */ 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 = g_malloc0(bitmap_size); } /* Never hold migration lock when yielding to the main loop! */ static void blk_mig_read_cb(void *opaque, int ret) { BlkMigBlock *blk = opaque; blk_mig_lock(); blk->ret = ret; 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); blk_mig_unlock(); } /* Called with no lock taken. */ static int mig_save_device_bulk(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) { qemu_mutex_lock_iothread(); while (cur_sector < total_sectors && !bdrv_is_allocated(bs, cur_sector, MAX_IS_ALLOCATED_SEARCH, &nr_sectors)) { cur_sector += nr_sectors; } qemu_mutex_unlock_iothread(); } 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 = g_malloc(sizeof(BlkMigBlock)); blk->buf = g_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_mig_lock(); block_mig_state.submitted++; blk_mig_unlock(); qemu_mutex_lock_iothread(); blk->aiocb = bdrv_aio_readv(bs, cur_sector, &blk->qiov, nr_sectors, blk_mig_read_cb, blk); bdrv_reset_dirty(bs, cur_sector, nr_sectors); qemu_mutex_unlock_iothread(); bmds->cur_sector = cur_sector + nr_sectors; return (bmds->cur_sector >= total_sectors); } /* Called with iothread lock taken. */ 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 ? BLOCK_SIZE : 0); } } static void init_blk_migration_it(void *opaque, BlockDriverState *bs) { BlkMigDevState *bmds; int64_t sectors; if (!bdrv_is_read_only(bs)) { sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS; if (sectors <= 0) { return; } bmds = g_malloc0(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); bdrv_set_in_use(bs, 1); bdrv_ref(bs); block_mig_state.total_sector_sum += sectors; if (bmds->shared_base) { DPRINTF("Start migration for %s with shared base image\n", bs->device_name); } else { DPRINTF("Start full migration for %s\n", bs->device_name); } QSIMPLEQ_INSERT_TAIL(&block_mig_state.bmds_list, bmds, entry); } } static void init_blk_migration(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.zero_blocks = migrate_zero_blocks(); bdrv_iterate(init_blk_migration_it, NULL); } /* Called with no lock taken. */ static int blk_mig_save_bulked_block(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(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); DPRINTF("Completed %d %%\r", progress); } 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; } } /* Called with iothread lock taken. */ static int mig_save_device_dirty(QEMUFile *f, BlkMigDevState *bmds, int is_async) { BlkMigBlock *blk; int64_t total_sectors = bmds->total_sectors; int64_t sector; int nr_sectors; int ret = -EIO; for (sector = bmds->cur_dirty; sector < bmds->total_sectors;) { blk_mig_lock(); if (bmds_aio_inflight(bmds, sector)) { blk_mig_unlock(); bdrv_drain_all(); } else { blk_mig_unlock(); } 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 = g_malloc(sizeof(BlkMigBlock)); blk->buf = g_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->aiocb = bdrv_aio_readv(bmds->bs, sector, &blk->qiov, nr_sectors, blk_mig_read_cb, blk); blk_mig_lock(); block_mig_state.submitted++; bmds_set_aio_inflight(bmds, sector, nr_sectors, 1); blk_mig_unlock(); } else { ret = bdrv_read(bmds->bs, sector, blk->buf, nr_sectors); if (ret < 0) { goto error; } blk_send(f, blk); g_free(blk->buf); g_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: DPRINTF("Error reading sector %" PRId64 "\n", sector); g_free(blk->buf); g_free(blk); return ret; } /* Called with iothread lock taken. * * return value: * 0: too much data for max_downtime * 1: few enough data for max_downtime */ static int blk_mig_save_dirty_block(QEMUFile *f, int is_async) { BlkMigDevState *bmds; int ret = 1; QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) { ret = mig_save_device_dirty(f, bmds, is_async); if (ret <= 0) { break; } } return ret; } /* Called with no locks taken. */ static int flush_blks(QEMUFile *f) { BlkMigBlock *blk; int ret = 0; 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); blk_mig_lock(); while ((blk = QSIMPLEQ_FIRST(&block_mig_state.blk_list)) != NULL) { if (qemu_file_rate_limit(f)) { break; } if (blk->ret < 0) { ret = blk->ret; break; } QSIMPLEQ_REMOVE_HEAD(&block_mig_state.blk_list, entry); blk_mig_unlock(); blk_send(f, blk); blk_mig_lock(); g_free(blk->buf); g_free(blk); block_mig_state.read_done--; block_mig_state.transferred++; assert(block_mig_state.read_done >= 0); } blk_mig_unlock(); 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); return ret; } /* Called with iothread lock taken. */ 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 << BDRV_SECTOR_BITS; } /* Called with iothread lock taken. */ static void blk_mig_cleanup(void) { BlkMigDevState *bmds; BlkMigBlock *blk; bdrv_drain_all(); set_dirty_tracking(0); blk_mig_lock(); 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); bdrv_unref(bmds->bs); g_free(bmds->aio_bitmap); g_free(bmds); } while ((blk = QSIMPLEQ_FIRST(&block_mig_state.blk_list)) != NULL) { QSIMPLEQ_REMOVE_HEAD(&block_mig_state.blk_list, entry); g_free(blk->buf); g_free(blk); } blk_mig_unlock(); } static void block_migration_cancel(void *opaque) { blk_mig_cleanup(); } static int block_save_setup(QEMUFile *f, void *opaque) { int ret; DPRINTF("Enter save live setup submitted %d transferred %d\n", block_mig_state.submitted, block_mig_state.transferred); qemu_mutex_lock_iothread(); init_blk_migration(f); /* start track dirty blocks */ set_dirty_tracking(1); qemu_mutex_unlock_iothread(); ret = flush_blks(f); blk_mig_reset_dirty_cursor(); qemu_put_be64(f, BLK_MIG_FLAG_EOS); return ret; } static int block_save_iterate(QEMUFile *f, void *opaque) { int ret; int64_t last_ftell = qemu_ftell(f); DPRINTF("Enter save live iterate submitted %d transferred %d\n", block_mig_state.submitted, block_mig_state.transferred); ret = flush_blks(f); if (ret) { return ret; } blk_mig_reset_dirty_cursor(); /* control the rate of transfer */ blk_mig_lock(); while ((block_mig_state.submitted + block_mig_state.read_done) * BLOCK_SIZE < qemu_file_get_rate_limit(f)) { blk_mig_unlock(); if (block_mig_state.bulk_completed == 0) { /* first finish the bulk phase */ if (blk_mig_save_bulked_block(f) == 0) { /* finished saving bulk on all devices */ block_mig_state.bulk_completed = 1; } ret = 0; } else { /* Always called with iothread lock taken for * simplicity, block_save_complete also calls it. */ qemu_mutex_lock_iothread(); ret = blk_mig_save_dirty_block(f, 1); qemu_mutex_unlock_iothread(); } if (ret < 0) { return ret; } blk_mig_lock(); if (ret != 0) { /* no more dirty blocks */ break; } } blk_mig_unlock(); ret = flush_blks(f); if (ret) { return ret; } qemu_put_be64(f, BLK_MIG_FLAG_EOS); return qemu_ftell(f) - last_ftell; } /* Called with iothread lock taken. */ static int block_save_complete(QEMUFile *f, void *opaque) { int ret; DPRINTF("Enter save live complete submitted %d transferred %d\n", block_mig_state.submitted, block_mig_state.transferred); ret = flush_blks(f); if (ret) { return ret; } blk_mig_reset_dirty_cursor(); /* we know for sure that save bulk is completed and all async read completed */ blk_mig_lock(); assert(block_mig_state.submitted == 0); blk_mig_unlock(); do { ret = blk_mig_save_dirty_block(f, 0); if (ret < 0) { return ret; } } while (ret == 0); /* report completion */ qemu_put_be64(f, (100 << BDRV_SECTOR_BITS) | BLK_MIG_FLAG_PROGRESS); DPRINTF("Block migration completed\n"); qemu_put_be64(f, BLK_MIG_FLAG_EOS); blk_mig_cleanup(); return 0; } static uint64_t block_save_pending(QEMUFile *f, void *opaque, uint64_t max_size) { /* Estimate pending number of bytes to send */ uint64_t pending; qemu_mutex_lock_iothread(); blk_mig_lock(); pending = get_remaining_dirty() + block_mig_state.submitted * BLOCK_SIZE + block_mig_state.read_done * BLOCK_SIZE; /* Report at least one block pending during bulk phase */ if (pending == 0 && !block_mig_state.bulk_completed) { pending = BLOCK_SIZE; } blk_mig_unlock(); qemu_mutex_unlock_iothread(); DPRINTF("Enter save live pending %" PRIu64 "\n", pending); return pending; } 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; int ret; do { addr = qemu_get_be64(f); flags = addr & ~BDRV_SECTOR_MASK; addr >>= BDRV_SECTOR_BITS; if (flags & BLK_MIG_FLAG_DEVICE_BLOCK) { /* 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", 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; } if (flags & BLK_MIG_FLAG_ZERO_BLOCK) { ret = bdrv_write_zeroes(bs, addr, nr_sectors); } else { buf = g_malloc(BLOCK_SIZE); qemu_get_buffer(f, buf, BLOCK_SIZE); ret = bdrv_write(bs, addr, buf, nr_sectors); g_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 block migration flags: %#x\n", flags); return -EINVAL; } ret = qemu_file_get_error(f); if (ret != 0) { return ret; } } while (!(flags & BLK_MIG_FLAG_EOS)); return 0; } static void block_set_params(const MigrationParams *params, void *opaque) { block_mig_state.blk_enable = params->blk; block_mig_state.shared_base = params->shared; /* shared base means that blk_enable = 1 */ block_mig_state.blk_enable |= params->shared; } static bool block_is_active(void *opaque) { return block_mig_state.blk_enable == 1; } SaveVMHandlers savevm_block_handlers = { .set_params = block_set_params, .save_live_setup = block_save_setup, .save_live_iterate = block_save_iterate, .save_live_complete = block_save_complete, .save_live_pending = block_save_pending, .load_state = block_load, .cancel = block_migration_cancel, .is_active = block_is_active, }; void blk_mig_init(void) { QSIMPLEQ_INIT(&block_mig_state.bmds_list); QSIMPLEQ_INIT(&block_mig_state.blk_list); qemu_mutex_init(&block_mig_state.lock); register_savevm_live(NULL, "block", 0, 1, &savevm_block_handlers, &block_mig_state); }