/* * QEMU System Emulator * * Copyright (c) 2003-2008 Fabrice Bellard * Copyright (c) 2011-2015 Red Hat Inc * * Authors: * Juan Quintela * * 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 "qemu/osdep.h" #include "qemu-common.h" #include "cpu.h" #include #include "qapi-event.h" #include "qemu/cutils.h" #include "qemu/bitops.h" #include "qemu/bitmap.h" #include "qemu/timer.h" #include "qemu/main-loop.h" #include "migration/migration.h" #include "migration/postcopy-ram.h" #include "exec/address-spaces.h" #include "migration/page_cache.h" #include "qemu/error-report.h" #include "trace.h" #include "exec/ram_addr.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 int dirty_rate_high_cnt; 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_is_zero(p, 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 QemuMutex migration_bitmap_mutex; static uint64_t migration_dirty_pages; static uint32_t last_version; static bool ram_bulk_stage; /* used by the search for pages to send */ struct PageSearchStatus { /* Current block being searched */ RAMBlock *block; /* Current offset to search from */ ram_addr_t offset; /* Set once we wrap around */ bool complete_round; }; typedef struct PageSearchStatus PageSearchStatus; static struct BitmapRcu { struct rcu_head rcu; /* Main migration bitmap */ unsigned long *bmap; /* bitmap of pages that haven't been sent even once * only maintained and used in postcopy at the moment * where it's used to send the dirtymap at the start * of the postcopy phase */ unsigned long *unsentmap; } *migration_bitmap_rcu; struct CompressParam { bool done; bool quit; QEMUFile *file; QemuMutex mutex; QemuCond cond; RAMBlock *block; ram_addr_t offset; }; typedef struct CompressParam CompressParam; struct DecompressParam { bool done; bool quit; QemuMutex mutex; QemuCond cond; void *des; uint8_t *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 DecompressParam *decomp_param; static QemuThread *decompress_threads; static QemuMutex decomp_done_lock; static QemuCond decomp_done_cond; static int do_compress_ram_page(QEMUFile *f, RAMBlock *block, ram_addr_t offset); static void *do_data_compress(void *opaque) { CompressParam *param = opaque; RAMBlock *block; ram_addr_t offset; qemu_mutex_lock(¶m->mutex); while (!param->quit) { if (param->block) { block = param->block; offset = param->offset; param->block = NULL; qemu_mutex_unlock(¶m->mutex); do_compress_ram_page(param->file, block, offset); qemu_mutex_lock(&comp_done_lock); param->done = true; qemu_cond_signal(&comp_done_cond); qemu_mutex_unlock(&comp_done_lock); qemu_mutex_lock(¶m->mutex); } else { qemu_cond_wait(¶m->cond, ¶m->mutex); } } qemu_mutex_unlock(¶m->mutex); return NULL; } static inline void terminate_compression_threads(void) { int idx, thread_count; thread_count = migrate_compress_threads(); for (idx = 0; idx < thread_count; idx++) { qemu_mutex_lock(&comp_param[idx].mutex); comp_param[idx].quit = true; 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); compress_threads = NULL; comp_param = NULL; } void migrate_compress_threads_create(void) { int i, thread_count; if (!migrate_use_compression()) { return; } compression_switch = true; thread_count = migrate_compress_threads(); compress_threads = g_new0(QemuThread, thread_count); comp_param = g_new0(CompressParam, thread_count); qemu_cond_init(&comp_done_cond); qemu_mutex_init(&comp_done_lock); for (i = 0; i < thread_count; i++) { /* comp_param[i].file is just used as a dummy buffer to save data, * set its ops to empty. */ comp_param[i].file = qemu_fopen_ops(NULL, &empty_ops); comp_param[i].done = true; comp_param[i].quit = false; 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, len; qemu_put_be64(f, offset); size = 8; if (!(offset & RAM_SAVE_FLAG_CONTINUE)) { len = strlen(block->idstr); qemu_put_byte(f, len); qemu_put_buffer(f, (uint8_t *)block->idstr, len); size += 1 + len; } return size; } /* Reduce amount of guest cpu execution to hopefully slow down memory writes. * If guest dirty memory rate is reduced below the rate at which we can * transfer pages to the destination then we should be able to complete * migration. Some workloads dirty memory way too fast and will not effectively * converge, even with auto-converge. */ static void mig_throttle_guest_down(void) { MigrationState *s = migrate_get_current(); uint64_t pct_initial = s->parameters.cpu_throttle_initial; uint64_t pct_icrement = s->parameters.cpu_throttle_increment; /* We have not started throttling yet. Let's start it. */ if (!cpu_throttle_active()) { cpu_throttle_set(pct_initial); } else { /* Throttling already on, just increase the rate */ cpu_throttle_set(cpu_throttle_get_percentage() + pct_icrement); } } /* 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; } /* Called with rcu_read_lock() to protect migration_bitmap * rb: The RAMBlock to search for dirty pages in * start: Start address (typically so we can continue from previous page) * ram_addr_abs: Pointer into which to store the address of the dirty page * within the global ram_addr space * * Returns: byte offset within memory region of the start of a dirty page */ static inline ram_addr_t migration_bitmap_find_dirty(RAMBlock *rb, ram_addr_t start, ram_addr_t *ram_addr_abs) { unsigned long base = rb->offset >> TARGET_PAGE_BITS; unsigned long nr = base + (start >> TARGET_PAGE_BITS); uint64_t rb_size = rb->used_length; unsigned long size = base + (rb_size >> TARGET_PAGE_BITS); unsigned long *bitmap; unsigned long next; bitmap = atomic_rcu_read(&migration_bitmap_rcu)->bmap; if (ram_bulk_stage && nr > base) { next = nr + 1; } else { next = find_next_bit(bitmap, size, nr); } *ram_addr_abs = next << TARGET_PAGE_BITS; return (next - base) << TARGET_PAGE_BITS; } static inline bool migration_bitmap_clear_dirty(ram_addr_t addr) { bool ret; int nr = addr >> TARGET_PAGE_BITS; unsigned long *bitmap = atomic_rcu_read(&migration_bitmap_rcu)->bmap; ret = test_and_clear_bit(nr, bitmap); if (ret) { migration_dirty_pages--; } return ret; } static void migration_bitmap_sync_range(ram_addr_t start, ram_addr_t length) { unsigned long *bitmap; bitmap = atomic_rcu_read(&migration_bitmap_rcu)->bmap; migration_dirty_pages += cpu_physical_memory_sync_dirty_bitmap(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; } 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(); memory_global_dirty_log_sync(); qemu_mutex_lock(&migration_bitmap_mutex); rcu_read_lock(); QLIST_FOREACH_RCU(block, &ram_list.blocks, next) { migration_bitmap_sync_range(block->offset, block->used_length); } rcu_read_unlock(); qemu_mutex_unlock(&migration_bitmap_mutex); 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 twice, start or increase throttling */ 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++ >= 2)) { trace_migration_throttle(); dirty_rate_high_cnt = 0; mig_throttle_guest_down(); } bytes_xfer_prev = bytes_xfer_now; } 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; if (migrate_use_events()) { qapi_event_send_migration_pass(bitmap_sync_count, NULL); } } /** * 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. * < 0 - error * >=0 - Number of pages written - this might legally be 0 * if xbzrle noticed the page was the same. * * @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, PageSearchStatus *pss, bool last_stage, uint64_t *bytes_transferred) { int pages = -1; uint64_t bytes_xmit; ram_addr_t current_addr; uint8_t *p; int ret; bool send_async = true; RAMBlock *block = pss->block; ram_addr_t offset = pss->offset; p = block->host + 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 && !migration_in_postcopy(migrate_get_current()) && 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(QEMUFile *f, RAMBlock *block, ram_addr_t offset) { int bytes_sent, blen; uint8_t *p = block->host + (offset & TARGET_PAGE_MASK); bytes_sent = save_page_header(f, block, offset | RAM_SAVE_FLAG_COMPRESS_PAGE); blen = qemu_put_compression_data(f, p, TARGET_PAGE_SIZE, migrate_compress_level()); if (blen < 0) { bytes_sent = 0; qemu_file_set_error(migrate_get_current()->to_dst_file, blen); error_report("compressed data failed!"); } else { bytes_sent += blen; } return bytes_sent; } 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(); qemu_mutex_lock(&comp_done_lock); for (idx = 0; idx < thread_count; idx++) { while (!comp_param[idx].done) { qemu_cond_wait(&comp_done_cond, &comp_done_lock); } } qemu_mutex_unlock(&comp_done_lock); for (idx = 0; idx < thread_count; idx++) { qemu_mutex_lock(&comp_param[idx].mutex); if (!comp_param[idx].quit) { len = qemu_put_qemu_file(f, comp_param[idx].file); bytes_transferred += len; } qemu_mutex_unlock(&comp_param[idx].mutex); } } 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) { comp_param[idx].done = false; bytes_xmit = qemu_put_qemu_file(f, comp_param[idx].file); qemu_mutex_lock(&comp_param[idx].mutex); set_compress_params(&comp_param[idx], block, offset); qemu_cond_signal(&comp_param[idx].cond); qemu_mutex_unlock(&comp_param[idx].mutex); 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, PageSearchStatus *pss, bool last_stage, uint64_t *bytes_transferred) { int pages = -1; uint64_t bytes_xmit = 0; uint8_t *p; int ret, blen; RAMBlock *block = pss->block; ram_addr_t offset = pss->offset; p = block->host + offset; ret = ram_control_save_page(f, block->offset, offset, TARGET_PAGE_SIZE, &bytes_xmit); if (bytes_xmit) { *bytes_transferred += bytes_xmit; pages = 1; } 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) { /* Make sure the first page is sent out before other pages */ bytes_xmit = save_page_header(f, block, offset | RAM_SAVE_FLAG_COMPRESS_PAGE); blen = qemu_put_compression_data(f, p, TARGET_PAGE_SIZE, migrate_compress_level()); if (blen > 0) { *bytes_transferred += bytes_xmit + blen; acct_info.norm_pages++; pages = 1; } else { qemu_file_set_error(f, blen); error_report("compressed data failed!"); } } } else { offset |= RAM_SAVE_FLAG_CONTINUE; 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; } /* * Find the next dirty page and update any state associated with * the search process. * * Returns: True if a page is found * * @f: Current migration stream. * @pss: Data about the state of the current dirty page scan. * @*again: Set to false if the search has scanned the whole of RAM * *ram_addr_abs: Pointer into which to store the address of the dirty page * within the global ram_addr space */ static bool find_dirty_block(QEMUFile *f, PageSearchStatus *pss, bool *again, ram_addr_t *ram_addr_abs) { pss->offset = migration_bitmap_find_dirty(pss->block, pss->offset, ram_addr_abs); if (pss->complete_round && pss->block == last_seen_block && pss->offset >= last_offset) { /* * We've been once around the RAM and haven't found anything. * Give up. */ *again = false; return false; } if (pss->offset >= pss->block->used_length) { /* Didn't find anything in this RAM Block */ pss->offset = 0; pss->block = QLIST_NEXT_RCU(pss->block, next); if (!pss->block) { /* Hit the end of the list */ pss->block = QLIST_FIRST_RCU(&ram_list.blocks); /* Flag that we've looped */ pss->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; } } /* Didn't find anything this time, but try again on the new block */ *again = true; return false; } else { /* Can go around again, but... */ *again = true; /* We've found something so probably don't need to */ return true; } } /* * Helper for 'get_queued_page' - gets a page off the queue * ms: MigrationState in * *offset: Used to return the offset within the RAMBlock * ram_addr_abs: global offset in the dirty/sent bitmaps * * Returns: block (or NULL if none available) */ static RAMBlock *unqueue_page(MigrationState *ms, ram_addr_t *offset, ram_addr_t *ram_addr_abs) { RAMBlock *block = NULL; qemu_mutex_lock(&ms->src_page_req_mutex); if (!QSIMPLEQ_EMPTY(&ms->src_page_requests)) { struct MigrationSrcPageRequest *entry = QSIMPLEQ_FIRST(&ms->src_page_requests); block = entry->rb; *offset = entry->offset; *ram_addr_abs = (entry->offset + entry->rb->offset) & TARGET_PAGE_MASK; if (entry->len > TARGET_PAGE_SIZE) { entry->len -= TARGET_PAGE_SIZE; entry->offset += TARGET_PAGE_SIZE; } else { memory_region_unref(block->mr); QSIMPLEQ_REMOVE_HEAD(&ms->src_page_requests, next_req); g_free(entry); } } qemu_mutex_unlock(&ms->src_page_req_mutex); return block; } /* * Unqueue a page from the queue fed by postcopy page requests; skips pages * that are already sent (!dirty) * * ms: MigrationState in * pss: PageSearchStatus structure updated with found block/offset * ram_addr_abs: global offset in the dirty/sent bitmaps * * Returns: true if a queued page is found */ static bool get_queued_page(MigrationState *ms, PageSearchStatus *pss, ram_addr_t *ram_addr_abs) { RAMBlock *block; ram_addr_t offset; bool dirty; do { block = unqueue_page(ms, &offset, ram_addr_abs); /* * We're sending this page, and since it's postcopy nothing else * will dirty it, and we must make sure it doesn't get sent again * even if this queue request was received after the background * search already sent it. */ if (block) { unsigned long *bitmap; bitmap = atomic_rcu_read(&migration_bitmap_rcu)->bmap; dirty = test_bit(*ram_addr_abs >> TARGET_PAGE_BITS, bitmap); if (!dirty) { trace_get_queued_page_not_dirty( block->idstr, (uint64_t)offset, (uint64_t)*ram_addr_abs, test_bit(*ram_addr_abs >> TARGET_PAGE_BITS, atomic_rcu_read(&migration_bitmap_rcu)->unsentmap)); } else { trace_get_queued_page(block->idstr, (uint64_t)offset, (uint64_t)*ram_addr_abs); } } } while (block && !dirty); if (block) { /* * As soon as we start servicing pages out of order, then we have * to kill the bulk stage, since the bulk stage assumes * in (migration_bitmap_find_and_reset_dirty) that every page is * dirty, that's no longer true. */ ram_bulk_stage = false; /* * We want the background search to continue from the queued page * since the guest is likely to want other pages near to the page * it just requested. */ pss->block = block; pss->offset = offset; } return !!block; } /** * flush_page_queue: Flush any remaining pages in the ram request queue * it should be empty at the end anyway, but in error cases there may be * some left. * * ms: MigrationState */ void flush_page_queue(MigrationState *ms) { struct MigrationSrcPageRequest *mspr, *next_mspr; /* This queue generally should be empty - but in the case of a failed * migration might have some droppings in. */ rcu_read_lock(); QSIMPLEQ_FOREACH_SAFE(mspr, &ms->src_page_requests, next_req, next_mspr) { memory_region_unref(mspr->rb->mr); QSIMPLEQ_REMOVE_HEAD(&ms->src_page_requests, next_req); g_free(mspr); } rcu_read_unlock(); } /** * Queue the pages for transmission, e.g. a request from postcopy destination * ms: MigrationStatus in which the queue is held * rbname: The RAMBlock the request is for - may be NULL (to mean reuse last) * start: Offset from the start of the RAMBlock * len: Length (in bytes) to send * Return: 0 on success */ int ram_save_queue_pages(MigrationState *ms, const char *rbname, ram_addr_t start, ram_addr_t len) { RAMBlock *ramblock; ms->postcopy_requests++; rcu_read_lock(); if (!rbname) { /* Reuse last RAMBlock */ ramblock = ms->last_req_rb; if (!ramblock) { /* * Shouldn't happen, we can't reuse the last RAMBlock if * it's the 1st request. */ error_report("ram_save_queue_pages no previous block"); goto err; } } else { ramblock = qemu_ram_block_by_name(rbname); if (!ramblock) { /* We shouldn't be asked for a non-existent RAMBlock */ error_report("ram_save_queue_pages no block '%s'", rbname); goto err; } ms->last_req_rb = ramblock; } trace_ram_save_queue_pages(ramblock->idstr, start, len); if (start+len > ramblock->used_length) { error_report("%s request overrun start=" RAM_ADDR_FMT " len=" RAM_ADDR_FMT " blocklen=" RAM_ADDR_FMT, __func__, start, len, ramblock->used_length); goto err; } struct MigrationSrcPageRequest *new_entry = g_malloc0(sizeof(struct MigrationSrcPageRequest)); new_entry->rb = ramblock; new_entry->offset = start; new_entry->len = len; memory_region_ref(ramblock->mr); qemu_mutex_lock(&ms->src_page_req_mutex); QSIMPLEQ_INSERT_TAIL(&ms->src_page_requests, new_entry, next_req); qemu_mutex_unlock(&ms->src_page_req_mutex); rcu_read_unlock(); return 0; err: rcu_read_unlock(); return -1; } /** * ram_save_target_page: Save one target page * * * @f: QEMUFile where to send the data * @block: pointer to 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 * @dirty_ram_abs: Address of the start of the dirty page in ram_addr_t space * * Returns: Number of pages written. */ static int ram_save_target_page(MigrationState *ms, QEMUFile *f, PageSearchStatus *pss, bool last_stage, uint64_t *bytes_transferred, ram_addr_t dirty_ram_abs) { int res = 0; /* Check the pages is dirty and if it is send it */ if (migration_bitmap_clear_dirty(dirty_ram_abs)) { unsigned long *unsentmap; if (compression_switch && migrate_use_compression()) { res = ram_save_compressed_page(f, pss, last_stage, bytes_transferred); } else { res = ram_save_page(f, pss, last_stage, bytes_transferred); } if (res < 0) { return res; } unsentmap = atomic_rcu_read(&migration_bitmap_rcu)->unsentmap; if (unsentmap) { clear_bit(dirty_ram_abs >> TARGET_PAGE_BITS, unsentmap); } /* Only update last_sent_block if a block was actually sent; xbzrle * might have decided the page was identical so didn't bother writing * to the stream. */ if (res > 0) { last_sent_block = pss->block; } } return res; } /** * ram_save_host_page: Starting at *offset send pages up to the end * of the current host page. It's valid for the initial * offset to point into the middle of a host page * in which case the remainder of the hostpage is sent. * Only dirty target pages are sent. * * Returns: Number of pages written. * * @f: QEMUFile where to send the data * @block: pointer to block that contains the page we want to send * @offset: offset inside the block for the page; updated to last target page * sent * @last_stage: if we are at the completion stage * @bytes_transferred: increase it with the number of transferred bytes * @dirty_ram_abs: Address of the start of the dirty page in ram_addr_t space */ static int ram_save_host_page(MigrationState *ms, QEMUFile *f, PageSearchStatus *pss, bool last_stage, uint64_t *bytes_transferred, ram_addr_t dirty_ram_abs) { int tmppages, pages = 0; do { tmppages = ram_save_target_page(ms, f, pss, last_stage, bytes_transferred, dirty_ram_abs); if (tmppages < 0) { return tmppages; } pages += tmppages; pss->offset += TARGET_PAGE_SIZE; dirty_ram_abs += TARGET_PAGE_SIZE; } while (pss->offset & (qemu_host_page_size - 1)); /* The offset we leave with is the last one we looked at */ pss->offset -= TARGET_PAGE_SIZE; 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 * * On systems where host-page-size > target-page-size it will send all the * pages in a host page that are dirty. */ static int ram_find_and_save_block(QEMUFile *f, bool last_stage, uint64_t *bytes_transferred) { PageSearchStatus pss; MigrationState *ms = migrate_get_current(); int pages = 0; bool again, found; ram_addr_t dirty_ram_abs; /* Address of the start of the dirty page in ram_addr_t space */ pss.block = last_seen_block; pss.offset = last_offset; pss.complete_round = false; if (!pss.block) { pss.block = QLIST_FIRST_RCU(&ram_list.blocks); } do { again = true; found = get_queued_page(ms, &pss, &dirty_ram_abs); if (!found) { /* priority queue empty, so just search for something dirty */ found = find_dirty_block(f, &pss, &again, &dirty_ram_abs); } if (found) { pages = ram_save_host_page(ms, f, &pss, last_stage, bytes_transferred, dirty_ram_abs); } } while (!pages && again); last_seen_block = pss.block; last_offset = pss.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_bitmap_free(struct BitmapRcu *bmap) { g_free(bmap->bmap); g_free(bmap->unsentmap); g_free(bmap); } static void ram_migration_cleanup(void *opaque) { /* caller have hold iothread lock or is in a bh, so there is * no writing race against this migration_bitmap */ struct BitmapRcu *bitmap = migration_bitmap_rcu; atomic_rcu_set(&migration_bitmap_rcu, NULL); if (bitmap) { memory_global_dirty_log_stop(); call_rcu(bitmap, migration_bitmap_free, rcu); } 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 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 */ void migration_bitmap_extend(ram_addr_t old, ram_addr_t new) { /* called in qemu main thread, so there is * no writing race against this migration_bitmap */ if (migration_bitmap_rcu) { struct BitmapRcu *old_bitmap = migration_bitmap_rcu, *bitmap; bitmap = g_new(struct BitmapRcu, 1); bitmap->bmap = bitmap_new(new); /* prevent migration_bitmap content from being set bit * by migration_bitmap_sync_range() at the same time. * it is safe to migration if migration_bitmap is cleared bit * at the same time. */ qemu_mutex_lock(&migration_bitmap_mutex); bitmap_copy(bitmap->bmap, old_bitmap->bmap, old); bitmap_set(bitmap->bmap, old, new - old); /* We don't have a way to safely extend the sentmap * with RCU; so mark it as missing, entry to postcopy * will fail. */ bitmap->unsentmap = NULL; atomic_rcu_set(&migration_bitmap_rcu, bitmap); qemu_mutex_unlock(&migration_bitmap_mutex); migration_dirty_pages += new - old; call_rcu(old_bitmap, migration_bitmap_free, rcu); } } /* * 'expected' is the value you expect the bitmap mostly to be full * of; it won't bother printing lines that are all this value. * If 'todump' is null the migration bitmap is dumped. */ void ram_debug_dump_bitmap(unsigned long *todump, bool expected) { int64_t ram_pages = last_ram_offset() >> TARGET_PAGE_BITS; int64_t cur; int64_t linelen = 128; char linebuf[129]; if (!todump) { todump = atomic_rcu_read(&migration_bitmap_rcu)->bmap; } for (cur = 0; cur < ram_pages; cur += linelen) { int64_t curb; bool found = false; /* * Last line; catch the case where the line length * is longer than remaining ram */ if (cur + linelen > ram_pages) { linelen = ram_pages - cur; } for (curb = 0; curb < linelen; curb++) { bool thisbit = test_bit(cur + curb, todump); linebuf[curb] = thisbit ? '1' : '.'; found = found || (thisbit != expected); } if (found) { linebuf[curb] = '\0'; fprintf(stderr, "0x%08" PRIx64 " : %s\n", cur, linebuf); } } } /* **** functions for postcopy ***** */ /* * Callback from postcopy_each_ram_send_discard for each RAMBlock * Note: At this point the 'unsentmap' is the processed bitmap combined * with the dirtymap; so a '1' means it's either dirty or unsent. * start,length: Indexes into the bitmap for the first bit * representing the named block and length in target-pages */ static int postcopy_send_discard_bm_ram(MigrationState *ms, PostcopyDiscardState *pds, unsigned long start, unsigned long length) { unsigned long end = start + length; /* one after the end */ unsigned long current; unsigned long *unsentmap; unsentmap = atomic_rcu_read(&migration_bitmap_rcu)->unsentmap; for (current = start; current < end; ) { unsigned long one = find_next_bit(unsentmap, end, current); if (one <= end) { unsigned long zero = find_next_zero_bit(unsentmap, end, one + 1); unsigned long discard_length; if (zero >= end) { discard_length = end - one; } else { discard_length = zero - one; } if (discard_length) { postcopy_discard_send_range(ms, pds, one, discard_length); } current = one + discard_length; } else { current = one; } } return 0; } /* * Utility for the outgoing postcopy code. * Calls postcopy_send_discard_bm_ram for each RAMBlock * passing it bitmap indexes and name. * Returns: 0 on success * (qemu_ram_foreach_block ends up passing unscaled lengths * which would mean postcopy code would have to deal with target page) */ static int postcopy_each_ram_send_discard(MigrationState *ms) { struct RAMBlock *block; int ret; QLIST_FOREACH_RCU(block, &ram_list.blocks, next) { unsigned long first = block->offset >> TARGET_PAGE_BITS; PostcopyDiscardState *pds = postcopy_discard_send_init(ms, first, block->idstr); /* * Postcopy sends chunks of bitmap over the wire, but it * just needs indexes at this point, avoids it having * target page specific code. */ ret = postcopy_send_discard_bm_ram(ms, pds, first, block->used_length >> TARGET_PAGE_BITS); postcopy_discard_send_finish(ms, pds); if (ret) { return ret; } } return 0; } /* * Helper for postcopy_chunk_hostpages; it's called twice to cleanup * the two bitmaps, that are similar, but one is inverted. * * We search for runs of target-pages that don't start or end on a * host page boundary; * unsent_pass=true: Cleans up partially unsent host pages by searching * the unsentmap * unsent_pass=false: Cleans up partially dirty host pages by searching * the main migration bitmap * */ static void postcopy_chunk_hostpages_pass(MigrationState *ms, bool unsent_pass, RAMBlock *block, PostcopyDiscardState *pds) { unsigned long *bitmap; unsigned long *unsentmap; unsigned int host_ratio = qemu_host_page_size / TARGET_PAGE_SIZE; unsigned long first = block->offset >> TARGET_PAGE_BITS; unsigned long len = block->used_length >> TARGET_PAGE_BITS; unsigned long last = first + (len - 1); unsigned long run_start; bitmap = atomic_rcu_read(&migration_bitmap_rcu)->bmap; unsentmap = atomic_rcu_read(&migration_bitmap_rcu)->unsentmap; if (unsent_pass) { /* Find a sent page */ run_start = find_next_zero_bit(unsentmap, last + 1, first); } else { /* Find a dirty page */ run_start = find_next_bit(bitmap, last + 1, first); } while (run_start <= last) { bool do_fixup = false; unsigned long fixup_start_addr; unsigned long host_offset; /* * If the start of this run of pages is in the middle of a host * page, then we need to fixup this host page. */ host_offset = run_start % host_ratio; if (host_offset) { do_fixup = true; run_start -= host_offset; fixup_start_addr = run_start; /* For the next pass */ run_start = run_start + host_ratio; } else { /* Find the end of this run */ unsigned long run_end; if (unsent_pass) { run_end = find_next_bit(unsentmap, last + 1, run_start + 1); } else { run_end = find_next_zero_bit(bitmap, last + 1, run_start + 1); } /* * If the end isn't at the start of a host page, then the * run doesn't finish at the end of a host page * and we need to discard. */ host_offset = run_end % host_ratio; if (host_offset) { do_fixup = true; fixup_start_addr = run_end - host_offset; /* * This host page has gone, the next loop iteration starts * from after the fixup */ run_start = fixup_start_addr + host_ratio; } else { /* * No discards on this iteration, next loop starts from * next sent/dirty page */ run_start = run_end + 1; } } if (do_fixup) { unsigned long page; /* Tell the destination to discard this page */ if (unsent_pass || !test_bit(fixup_start_addr, unsentmap)) { /* For the unsent_pass we: * discard partially sent pages * For the !unsent_pass (dirty) we: * discard partially dirty pages that were sent * (any partially sent pages were already discarded * by the previous unsent_pass) */ postcopy_discard_send_range(ms, pds, fixup_start_addr, host_ratio); } /* Clean up the bitmap */ for (page = fixup_start_addr; page < fixup_start_addr + host_ratio; page++) { /* All pages in this host page are now not sent */ set_bit(page, unsentmap); /* * Remark them as dirty, updating the count for any pages * that weren't previously dirty. */ migration_dirty_pages += !test_and_set_bit(page, bitmap); } } if (unsent_pass) { /* Find the next sent page for the next iteration */ run_start = find_next_zero_bit(unsentmap, last + 1, run_start); } else { /* Find the next dirty page for the next iteration */ run_start = find_next_bit(bitmap, last + 1, run_start); } } } /* * Utility for the outgoing postcopy code. * * Discard any partially sent host-page size chunks, mark any partially * dirty host-page size chunks as all dirty. * * Returns: 0 on success */ static int postcopy_chunk_hostpages(MigrationState *ms) { struct RAMBlock *block; if (qemu_host_page_size == TARGET_PAGE_SIZE) { /* Easy case - TPS==HPS - nothing to be done */ return 0; } /* Easiest way to make sure we don't resume in the middle of a host-page */ last_seen_block = NULL; last_sent_block = NULL; last_offset = 0; QLIST_FOREACH_RCU(block, &ram_list.blocks, next) { unsigned long first = block->offset >> TARGET_PAGE_BITS; PostcopyDiscardState *pds = postcopy_discard_send_init(ms, first, block->idstr); /* First pass: Discard all partially sent host pages */ postcopy_chunk_hostpages_pass(ms, true, block, pds); /* * Second pass: Ensure that all partially dirty host pages are made * fully dirty. */ postcopy_chunk_hostpages_pass(ms, false, block, pds); postcopy_discard_send_finish(ms, pds); } /* ram_list loop */ return 0; } /* * Transmit the set of pages to be discarded after precopy to the target * these are pages that: * a) Have been previously transmitted but are now dirty again * b) Pages that have never been transmitted, this ensures that * any pages on the destination that have been mapped by background * tasks get discarded (transparent huge pages is the specific concern) * Hopefully this is pretty sparse */ int ram_postcopy_send_discard_bitmap(MigrationState *ms) { int ret; unsigned long *bitmap, *unsentmap; rcu_read_lock(); /* This should be our last sync, the src is now paused */ migration_bitmap_sync(); unsentmap = atomic_rcu_read(&migration_bitmap_rcu)->unsentmap; if (!unsentmap) { /* We don't have a safe way to resize the sentmap, so * if the bitmap was resized it will be NULL at this * point. */ error_report("migration ram resized during precopy phase"); rcu_read_unlock(); return -EINVAL; } /* Deal with TPS != HPS */ ret = postcopy_chunk_hostpages(ms); if (ret) { rcu_read_unlock(); return ret; } /* * Update the unsentmap to be unsentmap = unsentmap | dirty */ bitmap = atomic_rcu_read(&migration_bitmap_rcu)->bmap; bitmap_or(unsentmap, unsentmap, bitmap, last_ram_offset() >> TARGET_PAGE_BITS); trace_ram_postcopy_send_discard_bitmap(); #ifdef DEBUG_POSTCOPY ram_debug_dump_bitmap(unsentmap, true); #endif ret = postcopy_each_ram_send_discard(ms); rcu_read_unlock(); return ret; } /* * At the start of the postcopy phase of migration, any now-dirty * precopied pages are discarded. * * start, length describe a byte address range within the RAMBlock * * Returns 0 on success. */ int ram_discard_range(MigrationIncomingState *mis, const char *block_name, uint64_t start, size_t length) { int ret = -1; rcu_read_lock(); RAMBlock *rb = qemu_ram_block_by_name(block_name); if (!rb) { error_report("ram_discard_range: Failed to find block '%s'", block_name); goto err; } uint8_t *host_startaddr = rb->host + start; if ((uintptr_t)host_startaddr & (qemu_host_page_size - 1)) { error_report("ram_discard_range: Unaligned start address: %p", host_startaddr); goto err; } if ((start + length) <= rb->used_length) { uint8_t *host_endaddr = host_startaddr + length; if ((uintptr_t)host_endaddr & (qemu_host_page_size - 1)) { error_report("ram_discard_range: Unaligned end address: %p", host_endaddr); goto err; } ret = postcopy_ram_discard_range(mis, host_startaddr, length); } else { error_report("ram_discard_range: Overrun block '%s' (%" PRIu64 "/%zx/" RAM_ADDR_FMT")", block_name, start, length, rb->used_length); } err: rcu_read_unlock(); return ret; } /* 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 */ dirty_rate_high_cnt = 0; bitmap_sync_count = 0; migration_bitmap_sync_init(); qemu_mutex_init(&migration_bitmap_mutex); 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(); } /* For memory_global_dirty_log_start below. */ 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_rcu = g_new0(struct BitmapRcu, 1); migration_bitmap_rcu->bmap = bitmap_new(ram_bitmap_pages); bitmap_set(migration_bitmap_rcu->bmap, 0, ram_bitmap_pages); if (migrate_postcopy_ram()) { migration_bitmap_rcu->unsentmap = bitmap_new(ram_bitmap_pages); bitmap_set(migration_bitmap_rcu->unsentmap, 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++; /* 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(); if (!migration_in_postcopy(migrate_get_current())) { 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); rcu_read_unlock(); qemu_put_be64(f, RAM_SAVE_FLAG_EOS); return 0; } static void ram_save_pending(QEMUFile *f, void *opaque, uint64_t max_size, uint64_t *non_postcopiable_pending, uint64_t *postcopiable_pending) { uint64_t remaining_size; remaining_size = ram_save_remaining() * TARGET_PAGE_SIZE; if (!migration_in_postcopy(migrate_get_current()) && 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; } /* We can do postcopy, and all the data is postcopiable */ *postcopiable_pending += remaining_size; } static int load_xbzrle(QEMUFile *f, ram_addr_t addr, void *host) { unsigned int xh_len; int xh_flags; uint8_t *loaded_data; if (!xbzrle_decoded_buf) { xbzrle_decoded_buf = g_malloc(TARGET_PAGE_SIZE); } loaded_data = xbzrle_decoded_buf; /* 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_in_place(f, &loaded_data, xh_len); /* decode RLE */ if (xbzrle_decode_buffer(loaded_data, 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. */ /* * Read a RAMBlock ID from the stream f. * * f: Stream to read from * flags: Page flags (mostly to see if it's a continuation of previous block) */ static inline RAMBlock *ram_block_from_stream(QEMUFile *f, int flags) { static RAMBlock *block = NULL; char id[256]; uint8_t len; if (flags & RAM_SAVE_FLAG_CONTINUE) { if (!block) { error_report("Ack, bad migration stream!"); return NULL; } return block; } len = qemu_get_byte(f); qemu_get_buffer(f, (uint8_t *)id, len); id[len] = 0; block = qemu_ram_block_by_name(id); if (!block) { error_report("Can't find block %s", id); return NULL; } return block; } static inline void *host_from_ram_block_offset(RAMBlock *block, ram_addr_t offset) { if (!offset_in_ramblock(block, offset)) { return NULL; } return block->host + offset; } /* * 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; uint8_t *des; int len; qemu_mutex_lock(¶m->mutex); while (!param->quit) { if (param->des) { des = param->des; len = param->len; param->des = 0; qemu_mutex_unlock(¶m->mutex); pagesize = TARGET_PAGE_SIZE; /* 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 *)des, &pagesize, (const Bytef *)param->compbuf, len); qemu_mutex_lock(&decomp_done_lock); param->done = true; qemu_cond_signal(&decomp_done_cond); qemu_mutex_unlock(&decomp_done_lock); qemu_mutex_lock(¶m->mutex); } else { qemu_cond_wait(¶m->cond, ¶m->mutex); } } qemu_mutex_unlock(¶m->mutex); return NULL; } static void wait_for_decompress_done(void) { int idx, thread_count; if (!migrate_use_compression()) { return; } thread_count = migrate_decompress_threads(); qemu_mutex_lock(&decomp_done_lock); for (idx = 0; idx < thread_count; idx++) { while (!decomp_param[idx].done) { qemu_cond_wait(&decomp_done_cond, &decomp_done_lock); } } qemu_mutex_unlock(&decomp_done_lock); } 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); qemu_mutex_init(&decomp_done_lock); qemu_cond_init(&decomp_done_cond); 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)); decomp_param[i].done = true; decomp_param[i].quit = false; 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; thread_count = migrate_decompress_threads(); for (i = 0; i < thread_count; i++) { qemu_mutex_lock(&decomp_param[i].mutex); decomp_param[i].quit = true; 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); decompress_threads = NULL; decomp_param = NULL; } static void decompress_data_with_multi_threads(QEMUFile *f, void *host, int len) { int idx, thread_count; thread_count = migrate_decompress_threads(); qemu_mutex_lock(&decomp_done_lock); while (true) { for (idx = 0; idx < thread_count; idx++) { if (decomp_param[idx].done) { decomp_param[idx].done = false; qemu_mutex_lock(&decomp_param[idx].mutex); qemu_get_buffer(f, decomp_param[idx].compbuf, len); decomp_param[idx].des = host; decomp_param[idx].len = len; qemu_cond_signal(&decomp_param[idx].cond); qemu_mutex_unlock(&decomp_param[idx].mutex); break; } } if (idx < thread_count) { break; } else { qemu_cond_wait(&decomp_done_cond, &decomp_done_lock); } } qemu_mutex_unlock(&decomp_done_lock); } /* * Allocate data structures etc needed by incoming migration with postcopy-ram * postcopy-ram's similarly names postcopy_ram_incoming_init does the work */ int ram_postcopy_incoming_init(MigrationIncomingState *mis) { size_t ram_pages = last_ram_offset() >> TARGET_PAGE_BITS; return postcopy_ram_incoming_init(mis, ram_pages); } /* * Called in postcopy mode by ram_load(). * rcu_read_lock is taken prior to this being called. */ static int ram_load_postcopy(QEMUFile *f) { int flags = 0, ret = 0; bool place_needed = false; bool matching_page_sizes = qemu_host_page_size == TARGET_PAGE_SIZE; MigrationIncomingState *mis = migration_incoming_get_current(); /* Temporary page that is later 'placed' */ void *postcopy_host_page = postcopy_get_tmp_page(mis); void *last_host = NULL; bool all_zero = false; while (!ret && !(flags & RAM_SAVE_FLAG_EOS)) { ram_addr_t addr; void *host = NULL; void *page_buffer = NULL; void *place_source = NULL; uint8_t ch; addr = qemu_get_be64(f); flags = addr & ~TARGET_PAGE_MASK; addr &= TARGET_PAGE_MASK; trace_ram_load_postcopy_loop((uint64_t)addr, flags); place_needed = false; if (flags & (RAM_SAVE_FLAG_COMPRESS | RAM_SAVE_FLAG_PAGE)) { RAMBlock *block = ram_block_from_stream(f, flags); host = host_from_ram_block_offset(block, addr); if (!host) { error_report("Illegal RAM offset " RAM_ADDR_FMT, addr); ret = -EINVAL; break; } /* * Postcopy requires that we place whole host pages atomically. * To make it atomic, the data is read into a temporary page * that's moved into place later. * The migration protocol uses, possibly smaller, target-pages * however the source ensures it always sends all the components * of a host page in order. */ page_buffer = postcopy_host_page + ((uintptr_t)host & ~qemu_host_page_mask); /* If all TP are zero then we can optimise the place */ if (!((uintptr_t)host & ~qemu_host_page_mask)) { all_zero = true; } else { /* not the 1st TP within the HP */ if (host != (last_host + TARGET_PAGE_SIZE)) { error_report("Non-sequential target page %p/%p", host, last_host); ret = -EINVAL; break; } } /* * If it's the last part of a host page then we place the host * page */ place_needed = (((uintptr_t)host + TARGET_PAGE_SIZE) & ~qemu_host_page_mask) == 0; place_source = postcopy_host_page; } last_host = host; switch (flags & ~RAM_SAVE_FLAG_CONTINUE) { case RAM_SAVE_FLAG_COMPRESS: ch = qemu_get_byte(f); memset(page_buffer, ch, TARGET_PAGE_SIZE); if (ch) { all_zero = false; } break; case RAM_SAVE_FLAG_PAGE: all_zero = false; if (!place_needed || !matching_page_sizes) { qemu_get_buffer(f, page_buffer, TARGET_PAGE_SIZE); } else { /* Avoids the qemu_file copy during postcopy, which is * going to do a copy later; can only do it when we * do this read in one go (matching page sizes) */ qemu_get_buffer_in_place(f, (uint8_t **)&place_source, TARGET_PAGE_SIZE); } break; case RAM_SAVE_FLAG_EOS: /* normal exit */ break; default: error_report("Unknown combination of migration flags: %#x" " (postcopy mode)", flags); ret = -EINVAL; } if (place_needed) { /* This gets called at the last target page in the host page */ if (all_zero) { ret = postcopy_place_page_zero(mis, host + TARGET_PAGE_SIZE - qemu_host_page_size); } else { ret = postcopy_place_page(mis, host + TARGET_PAGE_SIZE - qemu_host_page_size, place_source); } } if (!ret) { ret = qemu_file_get_error(f); } } return ret; } static int ram_load(QEMUFile *f, void *opaque, int version_id) { int flags = 0, ret = 0; static uint64_t seq_iter; int len = 0; /* * If system is running in postcopy mode, page inserts to host memory must * be atomic */ bool postcopy_running = postcopy_state_get() >= POSTCOPY_INCOMING_LISTENING; 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(); if (postcopy_running) { ret = ram_load_postcopy(f); } while (!postcopy_running && !ret && !(flags & RAM_SAVE_FLAG_EOS)) { ram_addr_t addr, total_ram_bytes; void *host = NULL; uint8_t ch; addr = qemu_get_be64(f); flags = addr & ~TARGET_PAGE_MASK; addr &= TARGET_PAGE_MASK; if (flags & (RAM_SAVE_FLAG_COMPRESS | RAM_SAVE_FLAG_PAGE | RAM_SAVE_FLAG_COMPRESS_PAGE | RAM_SAVE_FLAG_XBZRLE)) { RAMBlock *block = ram_block_from_stream(f, flags); host = host_from_ram_block_offset(block, addr); if (!host) { error_report("Illegal RAM offset " RAM_ADDR_FMT, addr); ret = -EINVAL; break; } } 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; 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); block = qemu_ram_block_by_name(id); if (block) { if (length != block->used_length) { Error *local_err = NULL; ret = qemu_ram_resize(block, length, &local_err); if (local_err) { error_report_err(local_err); } } ram_control_load_hook(f, RAM_CONTROL_BLOCK_REG, block->idstr); } else { error_report("Unknown ramblock \"%s\", cannot " "accept migration", id); ret = -EINVAL; } total_ram_bytes -= length; } break; case RAM_SAVE_FLAG_COMPRESS: ch = qemu_get_byte(f); ram_handle_compressed(host, ch, TARGET_PAGE_SIZE); break; case RAM_SAVE_FLAG_PAGE: qemu_get_buffer(f, host, TARGET_PAGE_SIZE); break; case RAM_SAVE_FLAG_COMPRESS_PAGE: len = qemu_get_be32(f); if (len < 0 || len > compressBound(TARGET_PAGE_SIZE)) { error_report("Invalid compressed data length: %d", len); ret = -EINVAL; break; } decompress_data_with_multi_threads(f, host, len); break; case RAM_SAVE_FLAG_XBZRLE: 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, RAM_CONTROL_HOOK, NULL); } else { error_report("Unknown combination of migration flags: %#x", flags); ret = -EINVAL; } } if (!ret) { ret = qemu_file_get_error(f); } } wait_for_decompress_done(); 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_postcopy = ram_save_complete, .save_live_complete_precopy = ram_save_complete, .save_live_pending = ram_save_pending, .load_state = ram_load, .cleanup = ram_migration_cleanup, }; void ram_mig_init(void) { qemu_mutex_init(&XBZRLE.lock); register_savevm_live(NULL, "ram", 0, 4, &savevm_ram_handlers, NULL); }