/* * 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/cutils.h" #include "qemu/bitops.h" #include "qemu/bitmap.h" #include "qemu/madvise.h" #include "qemu/main-loop.h" #include "xbzrle.h" #include "ram-compress.h" #include "ram.h" #include "migration.h" #include "migration-stats.h" #include "migration/register.h" #include "migration/misc.h" #include "qemu-file.h" #include "postcopy-ram.h" #include "page_cache.h" #include "qemu/error-report.h" #include "qapi/error.h" #include "qapi/qapi-types-migration.h" #include "qapi/qapi-events-migration.h" #include "qapi/qapi-commands-migration.h" #include "qapi/qmp/qerror.h" #include "trace.h" #include "exec/ram_addr.h" #include "exec/target_page.h" #include "qemu/rcu_queue.h" #include "migration/colo.h" #include "block.h" #include "sysemu/cpu-throttle.h" #include "savevm.h" #include "qemu/iov.h" #include "multifd.h" #include "sysemu/runstate.h" #include "rdma.h" #include "options.h" #include "sysemu/dirtylimit.h" #include "sysemu/kvm.h" #include "hw/boards.h" /* for machine_dump_guest_core() */ #if defined(__linux__) #include "qemu/userfaultfd.h" #endif /* defined(__linux__) */ /***********************************************************/ /* ram save/restore */ /* * RAM_SAVE_FLAG_ZERO used to be named RAM_SAVE_FLAG_COMPRESS, it * worked for pages that were filled with the same char. We switched * it to only search for the zero value. And to avoid confusion with * RAM_SAVE_FLAG_COMPRESS_PAGE just rename it. */ /* * RAM_SAVE_FLAG_FULL was obsoleted in 2009, it can be reused now */ #define RAM_SAVE_FLAG_FULL 0x01 #define RAM_SAVE_FLAG_ZERO 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 rdma.h for RAM_SAVE_FLAG_HOOK */ #define RAM_SAVE_FLAG_COMPRESS_PAGE 0x100 #define RAM_SAVE_FLAG_MULTIFD_FLUSH 0x200 /* We can't use any flag that is bigger than 0x200 */ XBZRLECacheStats xbzrle_counters; /* used by the search for pages to send */ struct PageSearchStatus { /* The migration channel used for a specific host page */ QEMUFile *pss_channel; /* Last block from where we have sent data */ RAMBlock *last_sent_block; /* Current block being searched */ RAMBlock *block; /* Current page to search from */ unsigned long page; /* Set once we wrap around */ bool complete_round; /* Whether we're sending a host page */ bool host_page_sending; /* The start/end of current host page. Invalid if host_page_sending==false */ unsigned long host_page_start; unsigned long host_page_end; }; typedef struct PageSearchStatus PageSearchStatus; /* 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; /* it will store a page full of zeros */ uint8_t *zero_target_page; /* buffer used for XBZRLE decoding */ uint8_t *decoded_buf; } XBZRLE; static void XBZRLE_cache_lock(void) { if (migrate_xbzrle()) { qemu_mutex_lock(&XBZRLE.lock); } } static void XBZRLE_cache_unlock(void) { if (migrate_xbzrle()) { qemu_mutex_unlock(&XBZRLE.lock); } } /** * xbzrle_cache_resize: resize the xbzrle cache * * This function is called from migrate_params_apply in main * thread, possibly while a migration is in progress. A running * migration may be using the cache and might finish during this call, * hence changes to the cache are protected by XBZRLE.lock(). * * Returns 0 for success or -1 for error * * @new_size: new cache size * @errp: set *errp if the check failed, with reason */ int xbzrle_cache_resize(uint64_t new_size, Error **errp) { PageCache *new_cache; int64_t ret = 0; /* Check for truncation */ if (new_size != (size_t)new_size) { error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "cache size", "exceeding address space"); return -1; } if (new_size == migrate_xbzrle_cache_size()) { /* nothing to do */ return 0; } XBZRLE_cache_lock(); if (XBZRLE.cache != NULL) { new_cache = cache_init(new_size, TARGET_PAGE_SIZE, errp); if (!new_cache) { ret = -1; goto out; } cache_fini(XBZRLE.cache); XBZRLE.cache = new_cache; } out: XBZRLE_cache_unlock(); return ret; } static bool postcopy_preempt_active(void) { return migrate_postcopy_preempt() && migration_in_postcopy(); } bool migrate_ram_is_ignored(RAMBlock *block) { return !qemu_ram_is_migratable(block) || (migrate_ignore_shared() && qemu_ram_is_shared(block) && qemu_ram_is_named_file(block)); } #undef RAMBLOCK_FOREACH int foreach_not_ignored_block(RAMBlockIterFunc func, void *opaque) { RAMBlock *block; int ret = 0; RCU_READ_LOCK_GUARD(); RAMBLOCK_FOREACH_NOT_IGNORED(block) { ret = func(block, opaque); if (ret) { break; } } return ret; } static void ramblock_recv_map_init(void) { RAMBlock *rb; RAMBLOCK_FOREACH_NOT_IGNORED(rb) { assert(!rb->receivedmap); rb->receivedmap = bitmap_new(rb->max_length >> qemu_target_page_bits()); } } int ramblock_recv_bitmap_test(RAMBlock *rb, void *host_addr) { return test_bit(ramblock_recv_bitmap_offset(host_addr, rb), rb->receivedmap); } bool ramblock_recv_bitmap_test_byte_offset(RAMBlock *rb, uint64_t byte_offset) { return test_bit(byte_offset >> TARGET_PAGE_BITS, rb->receivedmap); } void ramblock_recv_bitmap_set(RAMBlock *rb, void *host_addr) { set_bit_atomic(ramblock_recv_bitmap_offset(host_addr, rb), rb->receivedmap); } void ramblock_recv_bitmap_set_range(RAMBlock *rb, void *host_addr, size_t nr) { bitmap_set_atomic(rb->receivedmap, ramblock_recv_bitmap_offset(host_addr, rb), nr); } #define RAMBLOCK_RECV_BITMAP_ENDING (0x0123456789abcdefULL) /* * Format: bitmap_size (8 bytes) + whole_bitmap (N bytes). * * Returns >0 if success with sent bytes, or <0 if error. */ int64_t ramblock_recv_bitmap_send(QEMUFile *file, const char *block_name) { RAMBlock *block = qemu_ram_block_by_name(block_name); unsigned long *le_bitmap, nbits; uint64_t size; if (!block) { error_report("%s: invalid block name: %s", __func__, block_name); return -1; } nbits = block->postcopy_length >> TARGET_PAGE_BITS; /* * Make sure the tmp bitmap buffer is big enough, e.g., on 32bit * machines we may need 4 more bytes for padding (see below * comment). So extend it a bit before hand. */ le_bitmap = bitmap_new(nbits + BITS_PER_LONG); /* * Always use little endian when sending the bitmap. This is * required that when source and destination VMs are not using the * same endianness. (Note: big endian won't work.) */ bitmap_to_le(le_bitmap, block->receivedmap, nbits); /* Size of the bitmap, in bytes */ size = DIV_ROUND_UP(nbits, 8); /* * size is always aligned to 8 bytes for 64bit machines, but it * may not be true for 32bit machines. We need this padding to * make sure the migration can survive even between 32bit and * 64bit machines. */ size = ROUND_UP(size, 8); qemu_put_be64(file, size); qemu_put_buffer(file, (const uint8_t *)le_bitmap, size); /* * Mark as an end, in case the middle part is screwed up due to * some "mysterious" reason. */ qemu_put_be64(file, RAMBLOCK_RECV_BITMAP_ENDING); qemu_fflush(file); g_free(le_bitmap); if (qemu_file_get_error(file)) { return qemu_file_get_error(file); } return size + sizeof(size); } /* * An outstanding page request, on the source, having been received * and queued */ struct RAMSrcPageRequest { RAMBlock *rb; hwaddr offset; hwaddr len; QSIMPLEQ_ENTRY(RAMSrcPageRequest) next_req; }; /* State of RAM for migration */ struct RAMState { /* * PageSearchStatus structures for the channels when send pages. * Protected by the bitmap_mutex. */ PageSearchStatus pss[RAM_CHANNEL_MAX]; /* UFFD file descriptor, used in 'write-tracking' migration */ int uffdio_fd; /* total ram size in bytes */ uint64_t ram_bytes_total; /* Last block that we have visited searching for dirty pages */ RAMBlock *last_seen_block; /* Last dirty target page we have sent */ ram_addr_t last_page; /* last ram version we have seen */ uint32_t last_version; /* How many times we have dirty too many pages */ int dirty_rate_high_cnt; /* these variables are used for bitmap sync */ /* last time we did a full bitmap_sync */ int64_t time_last_bitmap_sync; /* bytes transferred at start_time */ uint64_t bytes_xfer_prev; /* number of dirty pages since start_time */ uint64_t num_dirty_pages_period; /* xbzrle misses since the beginning of the period */ uint64_t xbzrle_cache_miss_prev; /* Amount of xbzrle pages since the beginning of the period */ uint64_t xbzrle_pages_prev; /* Amount of xbzrle encoded bytes since the beginning of the period */ uint64_t xbzrle_bytes_prev; /* Are we really using XBZRLE (e.g., after the first round). */ bool xbzrle_started; /* Are we on the last stage of migration */ bool last_stage; /* compression statistics since the beginning of the period */ /* amount of count that no free thread to compress data */ uint64_t compress_thread_busy_prev; /* amount bytes after compression */ uint64_t compressed_size_prev; /* amount of compressed pages */ uint64_t compress_pages_prev; /* total handled target pages at the beginning of period */ uint64_t target_page_count_prev; /* total handled target pages since start */ uint64_t target_page_count; /* number of dirty bits in the bitmap */ uint64_t migration_dirty_pages; /* * Protects: * - dirty/clear bitmap * - migration_dirty_pages * - pss structures */ QemuMutex bitmap_mutex; /* The RAMBlock used in the last src_page_requests */ RAMBlock *last_req_rb; /* Queue of outstanding page requests from the destination */ QemuMutex src_page_req_mutex; QSIMPLEQ_HEAD(, RAMSrcPageRequest) src_page_requests; /* * This is only used when postcopy is in recovery phase, to communicate * between the migration thread and the return path thread on dirty * bitmap synchronizations. This field is unused in other stages of * RAM migration. */ unsigned int postcopy_bmap_sync_requested; }; typedef struct RAMState RAMState; static RAMState *ram_state; static NotifierWithReturnList precopy_notifier_list; /* Whether postcopy has queued requests? */ static bool postcopy_has_request(RAMState *rs) { return !QSIMPLEQ_EMPTY_ATOMIC(&rs->src_page_requests); } void precopy_infrastructure_init(void) { notifier_with_return_list_init(&precopy_notifier_list); } void precopy_add_notifier(NotifierWithReturn *n) { notifier_with_return_list_add(&precopy_notifier_list, n); } void precopy_remove_notifier(NotifierWithReturn *n) { notifier_with_return_remove(n); } int precopy_notify(PrecopyNotifyReason reason, Error **errp) { PrecopyNotifyData pnd; pnd.reason = reason; pnd.errp = errp; return notifier_with_return_list_notify(&precopy_notifier_list, &pnd); } uint64_t ram_bytes_remaining(void) { return ram_state ? (ram_state->migration_dirty_pages * TARGET_PAGE_SIZE) : 0; } void ram_transferred_add(uint64_t bytes) { if (runstate_is_running()) { stat64_add(&mig_stats.precopy_bytes, bytes); } else if (migration_in_postcopy()) { stat64_add(&mig_stats.postcopy_bytes, bytes); } else { stat64_add(&mig_stats.downtime_bytes, bytes); } stat64_add(&mig_stats.transferred, bytes); } struct MigrationOps { int (*ram_save_target_page)(RAMState *rs, PageSearchStatus *pss); }; typedef struct MigrationOps MigrationOps; MigrationOps *migration_ops; static int ram_save_host_page_urgent(PageSearchStatus *pss); /* NOTE: page is the PFN not real ram_addr_t. */ static void pss_init(PageSearchStatus *pss, RAMBlock *rb, ram_addr_t page) { pss->block = rb; pss->page = page; pss->complete_round = false; } /* * Check whether two PSSs are actively sending the same page. Return true * if it is, false otherwise. */ static bool pss_overlap(PageSearchStatus *pss1, PageSearchStatus *pss2) { return pss1->host_page_sending && pss2->host_page_sending && (pss1->host_page_start == pss2->host_page_start); } /** * save_page_header: write page header to wire * * If this is the 1st block, it also writes the block identification * * Returns the number of bytes written * * @pss: current PSS channel status * @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(PageSearchStatus *pss, QEMUFile *f, RAMBlock *block, ram_addr_t offset) { size_t size, len; bool same_block = (block == pss->last_sent_block); if (same_block) { offset |= RAM_SAVE_FLAG_CONTINUE; } qemu_put_be64(f, offset); size = 8; if (!same_block) { len = strlen(block->idstr); qemu_put_byte(f, len); qemu_put_buffer(f, (uint8_t *)block->idstr, len); size += 1 + len; pss->last_sent_block = block; } return size; } /** * mig_throttle_guest_down: throttle down the guest * * 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(uint64_t bytes_dirty_period, uint64_t bytes_dirty_threshold) { uint64_t pct_initial = migrate_cpu_throttle_initial(); uint64_t pct_increment = migrate_cpu_throttle_increment(); bool pct_tailslow = migrate_cpu_throttle_tailslow(); int pct_max = migrate_max_cpu_throttle(); uint64_t throttle_now = cpu_throttle_get_percentage(); uint64_t cpu_now, cpu_ideal, throttle_inc; /* 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 */ if (!pct_tailslow) { throttle_inc = pct_increment; } else { /* Compute the ideal CPU percentage used by Guest, which may * make the dirty rate match the dirty rate threshold. */ cpu_now = 100 - throttle_now; cpu_ideal = cpu_now * (bytes_dirty_threshold * 1.0 / bytes_dirty_period); throttle_inc = MIN(cpu_now - cpu_ideal, pct_increment); } cpu_throttle_set(MIN(throttle_now + throttle_inc, pct_max)); } } void mig_throttle_counter_reset(void) { RAMState *rs = ram_state; rs->time_last_bitmap_sync = qemu_clock_get_ms(QEMU_CLOCK_REALTIME); rs->num_dirty_pages_period = 0; rs->bytes_xfer_prev = stat64_get(&mig_stats.transferred); } /** * xbzrle_cache_zero_page: insert a zero page in the XBZRLE cache * * @current_addr: address for the zero page * * 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) { /* 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, XBZRLE.zero_target_page, stat64_get(&mig_stats.dirty_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 * * @rs: current RAM state * @pss: current PSS channel * @current_data: pointer to the address of the page contents * @current_addr: addr of the page * @block: block that contains the page we want to send * @offset: offset inside the block for the page */ static int save_xbzrle_page(RAMState *rs, PageSearchStatus *pss, uint8_t **current_data, ram_addr_t current_addr, RAMBlock *block, ram_addr_t offset) { int encoded_len = 0, bytes_xbzrle; uint8_t *prev_cached_page; QEMUFile *file = pss->pss_channel; uint64_t generation = stat64_get(&mig_stats.dirty_sync_count); if (!cache_is_cached(XBZRLE.cache, current_addr, generation)) { xbzrle_counters.cache_miss++; if (!rs->last_stage) { if (cache_insert(XBZRLE.cache, current_addr, *current_data, generation) == -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; } /* * Reaching here means the page has hit the xbzrle cache, no matter what * encoding result it is (normal encoding, overflow or skipping the page), * count the page as encoded. This is used to calculate the encoding rate. * * Example: 2 pages (8KB) being encoded, first page encoding generates 2KB, * 2nd page turns out to be skipped (i.e. no new bytes written to the * page), the overall encoding rate will be 8KB / 2KB = 4, which has the * skipped page included. In this way, the encoding rate can tell if the * guest page is good for xbzrle encoding. */ xbzrle_counters.pages++; 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); /* * Update the cache contents, so that it corresponds to the data * sent, in all cases except where we skip the page. */ if (!rs->last_stage && encoded_len != 0) { memcpy(prev_cached_page, XBZRLE.current_buf, TARGET_PAGE_SIZE); /* * In the case where we couldn't compress, ensure that the caller * sends the data from the cache, since the guest might have * changed the RAM since we copied it. */ *current_data = prev_cached_page; } if (encoded_len == 0) { trace_save_xbzrle_page_skipping(); return 0; } else if (encoded_len == -1) { trace_save_xbzrle_page_overflow(); xbzrle_counters.overflow++; xbzrle_counters.bytes += TARGET_PAGE_SIZE; return -1; } /* Send XBZRLE based compressed page */ bytes_xbzrle = save_page_header(pss, pss->pss_channel, block, offset | RAM_SAVE_FLAG_XBZRLE); qemu_put_byte(file, ENCODING_FLAG_XBZRLE); qemu_put_be16(file, encoded_len); qemu_put_buffer(file, XBZRLE.encoded_buf, encoded_len); bytes_xbzrle += encoded_len + 1 + 2; /* * Like compressed_size (please see update_compress_thread_counts), * the xbzrle encoded bytes don't count the 8 byte header with * RAM_SAVE_FLAG_CONTINUE. */ xbzrle_counters.bytes += bytes_xbzrle - 8; ram_transferred_add(bytes_xbzrle); return 1; } /** * pss_find_next_dirty: find the next dirty page of current ramblock * * This function updates pss->page to point to the next dirty page index * within the ramblock to migrate, or the end of ramblock when nothing * found. Note that when pss->host_page_sending==true it means we're * during sending a host page, so we won't look for dirty page that is * outside the host page boundary. * * @pss: the current page search status */ static void pss_find_next_dirty(PageSearchStatus *pss) { RAMBlock *rb = pss->block; unsigned long size = rb->used_length >> TARGET_PAGE_BITS; unsigned long *bitmap = rb->bmap; if (migrate_ram_is_ignored(rb)) { /* Points directly to the end, so we know no dirty page */ pss->page = size; return; } /* * If during sending a host page, only look for dirty pages within the * current host page being send. */ if (pss->host_page_sending) { assert(pss->host_page_end); size = MIN(size, pss->host_page_end); } pss->page = find_next_bit(bitmap, size, pss->page); } static void migration_clear_memory_region_dirty_bitmap(RAMBlock *rb, unsigned long page) { uint8_t shift; hwaddr size, start; if (!rb->clear_bmap || !clear_bmap_test_and_clear(rb, page)) { return; } shift = rb->clear_bmap_shift; /* * CLEAR_BITMAP_SHIFT_MIN should always guarantee this... this * can make things easier sometimes since then start address * of the small chunk will always be 64 pages aligned so the * bitmap will always be aligned to unsigned long. We should * even be able to remove this restriction but I'm simply * keeping it. */ assert(shift >= 6); size = 1ULL << (TARGET_PAGE_BITS + shift); start = QEMU_ALIGN_DOWN((ram_addr_t)page << TARGET_PAGE_BITS, size); trace_migration_bitmap_clear_dirty(rb->idstr, start, size, page); memory_region_clear_dirty_bitmap(rb->mr, start, size); } static void migration_clear_memory_region_dirty_bitmap_range(RAMBlock *rb, unsigned long start, unsigned long npages) { unsigned long i, chunk_pages = 1UL << rb->clear_bmap_shift; unsigned long chunk_start = QEMU_ALIGN_DOWN(start, chunk_pages); unsigned long chunk_end = QEMU_ALIGN_UP(start + npages, chunk_pages); /* * Clear pages from start to start + npages - 1, so the end boundary is * exclusive. */ for (i = chunk_start; i < chunk_end; i += chunk_pages) { migration_clear_memory_region_dirty_bitmap(rb, i); } } /* * colo_bitmap_find_diry:find contiguous dirty pages from start * * Returns the page offset within memory region of the start of the contiguout * dirty page * * @rs: current RAM state * @rb: RAMBlock where to search for dirty pages * @start: page where we start the search * @num: the number of contiguous dirty pages */ static inline unsigned long colo_bitmap_find_dirty(RAMState *rs, RAMBlock *rb, unsigned long start, unsigned long *num) { unsigned long size = rb->used_length >> TARGET_PAGE_BITS; unsigned long *bitmap = rb->bmap; unsigned long first, next; *num = 0; if (migrate_ram_is_ignored(rb)) { return size; } first = find_next_bit(bitmap, size, start); if (first >= size) { return first; } next = find_next_zero_bit(bitmap, size, first + 1); assert(next >= first); *num = next - first; return first; } static inline bool migration_bitmap_clear_dirty(RAMState *rs, RAMBlock *rb, unsigned long page) { bool ret; /* * Clear dirty bitmap if needed. This _must_ be called before we * send any of the page in the chunk because we need to make sure * we can capture further page content changes when we sync dirty * log the next time. So as long as we are going to send any of * the page in the chunk we clear the remote dirty bitmap for all. * Clearing it earlier won't be a problem, but too late will. */ migration_clear_memory_region_dirty_bitmap(rb, page); ret = test_and_clear_bit(page, rb->bmap); if (ret) { rs->migration_dirty_pages--; } return ret; } static void dirty_bitmap_clear_section(MemoryRegionSection *section, void *opaque) { const hwaddr offset = section->offset_within_region; const hwaddr size = int128_get64(section->size); const unsigned long start = offset >> TARGET_PAGE_BITS; const unsigned long npages = size >> TARGET_PAGE_BITS; RAMBlock *rb = section->mr->ram_block; uint64_t *cleared_bits = opaque; /* * We don't grab ram_state->bitmap_mutex because we expect to run * only when starting migration or during postcopy recovery where * we don't have concurrent access. */ if (!migration_in_postcopy() && !migrate_background_snapshot()) { migration_clear_memory_region_dirty_bitmap_range(rb, start, npages); } *cleared_bits += bitmap_count_one_with_offset(rb->bmap, start, npages); bitmap_clear(rb->bmap, start, npages); } /* * Exclude all dirty pages from migration that fall into a discarded range as * managed by a RamDiscardManager responsible for the mapped memory region of * the RAMBlock. Clear the corresponding bits in the dirty bitmaps. * * Discarded pages ("logically unplugged") have undefined content and must * not get migrated, because even reading these pages for migration might * result in undesired behavior. * * Returns the number of cleared bits in the RAMBlock dirty bitmap. * * Note: The result is only stable while migrating (precopy/postcopy). */ static uint64_t ramblock_dirty_bitmap_clear_discarded_pages(RAMBlock *rb) { uint64_t cleared_bits = 0; if (rb->mr && rb->bmap && memory_region_has_ram_discard_manager(rb->mr)) { RamDiscardManager *rdm = memory_region_get_ram_discard_manager(rb->mr); MemoryRegionSection section = { .mr = rb->mr, .offset_within_region = 0, .size = int128_make64(qemu_ram_get_used_length(rb)), }; ram_discard_manager_replay_discarded(rdm, §ion, dirty_bitmap_clear_section, &cleared_bits); } return cleared_bits; } /* * Check if a host-page aligned page falls into a discarded range as managed by * a RamDiscardManager responsible for the mapped memory region of the RAMBlock. * * Note: The result is only stable while migrating (precopy/postcopy). */ bool ramblock_page_is_discarded(RAMBlock *rb, ram_addr_t start) { if (rb->mr && memory_region_has_ram_discard_manager(rb->mr)) { RamDiscardManager *rdm = memory_region_get_ram_discard_manager(rb->mr); MemoryRegionSection section = { .mr = rb->mr, .offset_within_region = start, .size = int128_make64(qemu_ram_pagesize(rb)), }; return !ram_discard_manager_is_populated(rdm, §ion); } return false; } /* Called with RCU critical section */ static void ramblock_sync_dirty_bitmap(RAMState *rs, RAMBlock *rb) { uint64_t new_dirty_pages = cpu_physical_memory_sync_dirty_bitmap(rb, 0, rb->used_length); rs->migration_dirty_pages += new_dirty_pages; rs->num_dirty_pages_period += new_dirty_pages; } /** * ram_pagesize_summary: calculate all the pagesizes of a VM * * Returns a summary bitmap of the page sizes of all RAMBlocks * * For VMs with just normal pages this is equivalent to the host page * size. If it's got some huge pages then it's the OR of all the * different page sizes. */ uint64_t ram_pagesize_summary(void) { RAMBlock *block; uint64_t summary = 0; RAMBLOCK_FOREACH_NOT_IGNORED(block) { summary |= block->page_size; } return summary; } uint64_t ram_get_total_transferred_pages(void) { return stat64_get(&mig_stats.normal_pages) + stat64_get(&mig_stats.zero_pages) + compression_counters.pages + xbzrle_counters.pages; } static void migration_update_rates(RAMState *rs, int64_t end_time) { uint64_t page_count = rs->target_page_count - rs->target_page_count_prev; double compressed_size; /* calculate period counters */ stat64_set(&mig_stats.dirty_pages_rate, rs->num_dirty_pages_period * 1000 / (end_time - rs->time_last_bitmap_sync)); if (!page_count) { return; } if (migrate_xbzrle()) { double encoded_size, unencoded_size; xbzrle_counters.cache_miss_rate = (double)(xbzrle_counters.cache_miss - rs->xbzrle_cache_miss_prev) / page_count; rs->xbzrle_cache_miss_prev = xbzrle_counters.cache_miss; unencoded_size = (xbzrle_counters.pages - rs->xbzrle_pages_prev) * TARGET_PAGE_SIZE; encoded_size = xbzrle_counters.bytes - rs->xbzrle_bytes_prev; if (xbzrle_counters.pages == rs->xbzrle_pages_prev || !encoded_size) { xbzrle_counters.encoding_rate = 0; } else { xbzrle_counters.encoding_rate = unencoded_size / encoded_size; } rs->xbzrle_pages_prev = xbzrle_counters.pages; rs->xbzrle_bytes_prev = xbzrle_counters.bytes; } if (migrate_compress()) { compression_counters.busy_rate = (double)(compression_counters.busy - rs->compress_thread_busy_prev) / page_count; rs->compress_thread_busy_prev = compression_counters.busy; compressed_size = compression_counters.compressed_size - rs->compressed_size_prev; if (compressed_size) { double uncompressed_size = (compression_counters.pages - rs->compress_pages_prev) * TARGET_PAGE_SIZE; /* Compression-Ratio = Uncompressed-size / Compressed-size */ compression_counters.compression_rate = uncompressed_size / compressed_size; rs->compress_pages_prev = compression_counters.pages; rs->compressed_size_prev = compression_counters.compressed_size; } } } /* * Enable dirty-limit to throttle down the guest */ static void migration_dirty_limit_guest(void) { /* * dirty page rate quota for all vCPUs fetched from * migration parameter 'vcpu_dirty_limit' */ static int64_t quota_dirtyrate; MigrationState *s = migrate_get_current(); /* * If dirty limit already enabled and migration parameter * vcpu-dirty-limit untouched. */ if (dirtylimit_in_service() && quota_dirtyrate == s->parameters.vcpu_dirty_limit) { return; } quota_dirtyrate = s->parameters.vcpu_dirty_limit; /* * Set all vCPU a quota dirtyrate, note that the second * parameter will be ignored if setting all vCPU for the vm */ qmp_set_vcpu_dirty_limit(false, -1, quota_dirtyrate, NULL); trace_migration_dirty_limit_guest(quota_dirtyrate); } static void migration_trigger_throttle(RAMState *rs) { uint64_t threshold = migrate_throttle_trigger_threshold(); uint64_t bytes_xfer_period = stat64_get(&mig_stats.transferred) - rs->bytes_xfer_prev; uint64_t bytes_dirty_period = rs->num_dirty_pages_period * TARGET_PAGE_SIZE; uint64_t bytes_dirty_threshold = bytes_xfer_period * threshold / 100; /* During block migration the auto-converge logic incorrectly detects * that ram migration makes no progress. Avoid this by disabling the * throttling logic during the bulk phase of block migration. */ if (blk_mig_bulk_active()) { return; } /* * The following detection logic can be refined later. For now: * Check to see if the ratio between dirtied bytes and the approx. * amount of bytes that just got transferred since the last time * we were in this routine reaches the threshold. If that happens * twice, start or increase throttling. */ if ((bytes_dirty_period > bytes_dirty_threshold) && (++rs->dirty_rate_high_cnt >= 2)) { rs->dirty_rate_high_cnt = 0; if (migrate_auto_converge()) { trace_migration_throttle(); mig_throttle_guest_down(bytes_dirty_period, bytes_dirty_threshold); } else if (migrate_dirty_limit()) { migration_dirty_limit_guest(); } } } static void migration_bitmap_sync(RAMState *rs, bool last_stage) { RAMBlock *block; int64_t end_time; stat64_add(&mig_stats.dirty_sync_count, 1); if (!rs->time_last_bitmap_sync) { rs->time_last_bitmap_sync = qemu_clock_get_ms(QEMU_CLOCK_REALTIME); } trace_migration_bitmap_sync_start(); memory_global_dirty_log_sync(last_stage); qemu_mutex_lock(&rs->bitmap_mutex); WITH_RCU_READ_LOCK_GUARD() { RAMBLOCK_FOREACH_NOT_IGNORED(block) { ramblock_sync_dirty_bitmap(rs, block); } stat64_set(&mig_stats.dirty_bytes_last_sync, ram_bytes_remaining()); } qemu_mutex_unlock(&rs->bitmap_mutex); memory_global_after_dirty_log_sync(); trace_migration_bitmap_sync_end(rs->num_dirty_pages_period); end_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME); /* more than 1 second = 1000 millisecons */ if (end_time > rs->time_last_bitmap_sync + 1000) { migration_trigger_throttle(rs); migration_update_rates(rs, end_time); rs->target_page_count_prev = rs->target_page_count; /* reset period counters */ rs->time_last_bitmap_sync = end_time; rs->num_dirty_pages_period = 0; rs->bytes_xfer_prev = stat64_get(&mig_stats.transferred); } if (migrate_events()) { uint64_t generation = stat64_get(&mig_stats.dirty_sync_count); qapi_event_send_migration_pass(generation); } } static void migration_bitmap_sync_precopy(RAMState *rs, bool last_stage) { Error *local_err = NULL; /* * The current notifier usage is just an optimization to migration, so we * don't stop the normal migration process in the error case. */ if (precopy_notify(PRECOPY_NOTIFY_BEFORE_BITMAP_SYNC, &local_err)) { error_report_err(local_err); local_err = NULL; } migration_bitmap_sync(rs, last_stage); if (precopy_notify(PRECOPY_NOTIFY_AFTER_BITMAP_SYNC, &local_err)) { error_report_err(local_err); } } void ram_release_page(const char *rbname, uint64_t offset) { if (!migrate_release_ram() || !migration_in_postcopy()) { return; } ram_discard_range(rbname, offset, TARGET_PAGE_SIZE); } /** * save_zero_page: send the zero page to the stream * * Returns the number of pages written. * * @rs: current RAM state * @pss: current PSS channel * @block: block that contains the page we want to send * @offset: offset inside the block for the page */ static int save_zero_page(RAMState *rs, PageSearchStatus *pss, RAMBlock *block, ram_addr_t offset) { uint8_t *p = block->host + offset; QEMUFile *file = pss->pss_channel; int len = 0; if (!buffer_is_zero(p, TARGET_PAGE_SIZE)) { return 0; } len += save_page_header(pss, file, block, offset | RAM_SAVE_FLAG_ZERO); qemu_put_byte(file, 0); len += 1; ram_release_page(block->idstr, offset); stat64_add(&mig_stats.zero_pages, 1); ram_transferred_add(len); /* * Must let xbzrle know, otherwise a previous (now 0'd) cached * page would be stale. */ if (rs->xbzrle_started) { XBZRLE_cache_lock(); xbzrle_cache_zero_page(block->offset + offset); XBZRLE_cache_unlock(); } return len; } /* * @pages: the number of pages written by the control path, * < 0 - error * > 0 - number of pages written * * Return true if the pages has been saved, otherwise false is returned. */ static bool control_save_page(PageSearchStatus *pss, RAMBlock *block, ram_addr_t offset, int *pages) { int ret; ret = rdma_control_save_page(pss->pss_channel, block->offset, offset, TARGET_PAGE_SIZE); if (ret == RAM_SAVE_CONTROL_NOT_SUPP) { return false; } if (ret == RAM_SAVE_CONTROL_DELAYED) { *pages = 1; return true; } *pages = ret; return true; } /* * directly send the page to the stream * * Returns the number of pages written. * * @pss: current PSS channel * @block: block that contains the page we want to send * @offset: offset inside the block for the page * @buf: the page to be sent * @async: send to page asyncly */ static int save_normal_page(PageSearchStatus *pss, RAMBlock *block, ram_addr_t offset, uint8_t *buf, bool async) { QEMUFile *file = pss->pss_channel; ram_transferred_add(save_page_header(pss, pss->pss_channel, block, offset | RAM_SAVE_FLAG_PAGE)); if (async) { qemu_put_buffer_async(file, buf, TARGET_PAGE_SIZE, migrate_release_ram() && migration_in_postcopy()); } else { qemu_put_buffer(file, buf, TARGET_PAGE_SIZE); } ram_transferred_add(TARGET_PAGE_SIZE); stat64_add(&mig_stats.normal_pages, 1); return 1; } /** * ram_save_page: send the given page to the stream * * Returns the number of pages written. * < 0 - error * >=0 - Number of pages written - this might legally be 0 * if xbzrle noticed the page was the same. * * @rs: current RAM state * @block: block that contains the page we want to send * @offset: offset inside the block for the page */ static int ram_save_page(RAMState *rs, PageSearchStatus *pss) { int pages = -1; uint8_t *p; bool send_async = true; RAMBlock *block = pss->block; ram_addr_t offset = ((ram_addr_t)pss->page) << TARGET_PAGE_BITS; ram_addr_t current_addr = block->offset + offset; p = block->host + offset; trace_ram_save_page(block->idstr, (uint64_t)offset, p); XBZRLE_cache_lock(); if (rs->xbzrle_started && !migration_in_postcopy()) { pages = save_xbzrle_page(rs, pss, &p, current_addr, block, offset); if (!rs->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) { pages = save_normal_page(pss, block, offset, p, send_async); } XBZRLE_cache_unlock(); return pages; } static int ram_save_multifd_page(QEMUFile *file, RAMBlock *block, ram_addr_t offset) { if (multifd_queue_page(file, block, offset) < 0) { return -1; } stat64_add(&mig_stats.normal_pages, 1); return 1; } static void update_compress_thread_counts(const CompressParam *param, int bytes_xmit) { ram_transferred_add(bytes_xmit); if (param->result == RES_ZEROPAGE) { stat64_add(&mig_stats.zero_pages, 1); return; } /* 8 means a header with RAM_SAVE_FLAG_CONTINUE. */ compression_counters.compressed_size += bytes_xmit - 8; compression_counters.pages++; } static bool save_page_use_compression(RAMState *rs); static int send_queued_data(CompressParam *param) { PageSearchStatus *pss = &ram_state->pss[RAM_CHANNEL_PRECOPY]; MigrationState *ms = migrate_get_current(); QEMUFile *file = ms->to_dst_file; int len = 0; RAMBlock *block = param->block; ram_addr_t offset = param->offset; if (param->result == RES_NONE) { return 0; } assert(block == pss->last_sent_block); if (param->result == RES_ZEROPAGE) { assert(qemu_file_buffer_empty(param->file)); len += save_page_header(pss, file, block, offset | RAM_SAVE_FLAG_ZERO); qemu_put_byte(file, 0); len += 1; ram_release_page(block->idstr, offset); } else if (param->result == RES_COMPRESS) { assert(!qemu_file_buffer_empty(param->file)); len += save_page_header(pss, file, block, offset | RAM_SAVE_FLAG_COMPRESS_PAGE); len += qemu_put_qemu_file(file, param->file); } else { abort(); } update_compress_thread_counts(param, len); return len; } static void ram_flush_compressed_data(RAMState *rs) { if (!save_page_use_compression(rs)) { return; } flush_compressed_data(send_queued_data); } #define PAGE_ALL_CLEAN 0 #define PAGE_TRY_AGAIN 1 #define PAGE_DIRTY_FOUND 2 /** * find_dirty_block: find the next dirty page and update any state * associated with the search process. * * Returns: * <0: An error happened * PAGE_ALL_CLEAN: no dirty page found, give up * PAGE_TRY_AGAIN: no dirty page found, retry for next block * PAGE_DIRTY_FOUND: dirty page found * * @rs: current RAM state * @pss: data about the state of the current dirty page scan * @again: set to false if the search has scanned the whole of RAM */ static int find_dirty_block(RAMState *rs, PageSearchStatus *pss) { /* Update pss->page for the next dirty bit in ramblock */ pss_find_next_dirty(pss); if (pss->complete_round && pss->block == rs->last_seen_block && pss->page >= rs->last_page) { /* * We've been once around the RAM and haven't found anything. * Give up. */ return PAGE_ALL_CLEAN; } if (!offset_in_ramblock(pss->block, ((ram_addr_t)pss->page) << TARGET_PAGE_BITS)) { /* Didn't find anything in this RAM Block */ pss->page = 0; pss->block = QLIST_NEXT_RCU(pss->block, next); if (!pss->block) { if (migrate_multifd() && !migrate_multifd_flush_after_each_section()) { QEMUFile *f = rs->pss[RAM_CHANNEL_PRECOPY].pss_channel; int ret = multifd_send_sync_main(f); if (ret < 0) { return ret; } qemu_put_be64(f, RAM_SAVE_FLAG_MULTIFD_FLUSH); qemu_fflush(f); } /* * If memory migration starts over, we will meet a dirtied page * which may still exists in compression threads's ring, so we * should flush the compressed data to make sure the new page * is not overwritten by the old one in the destination. * * Also If xbzrle is on, stop using the data compression at this * point. In theory, xbzrle can do better than compression. */ ram_flush_compressed_data(rs); /* Hit the end of the list */ pss->block = QLIST_FIRST_RCU(&ram_list.blocks); /* Flag that we've looped */ pss->complete_round = true; /* After the first round, enable XBZRLE. */ if (migrate_xbzrle()) { rs->xbzrle_started = true; } } /* Didn't find anything this time, but try again on the new block */ return PAGE_TRY_AGAIN; } else { /* We've found something */ return PAGE_DIRTY_FOUND; } } /** * unqueue_page: gets a page of the queue * * Helper for 'get_queued_page' - gets a page off the queue * * Returns the block of the page (or NULL if none available) * * @rs: current RAM state * @offset: used to return the offset within the RAMBlock */ static RAMBlock *unqueue_page(RAMState *rs, ram_addr_t *offset) { struct RAMSrcPageRequest *entry; RAMBlock *block = NULL; if (!postcopy_has_request(rs)) { return NULL; } QEMU_LOCK_GUARD(&rs->src_page_req_mutex); /* * This should _never_ change even after we take the lock, because no one * should be taking anything off the request list other than us. */ assert(postcopy_has_request(rs)); entry = QSIMPLEQ_FIRST(&rs->src_page_requests); block = entry->rb; *offset = entry->offset; 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(&rs->src_page_requests, next_req); g_free(entry); migration_consume_urgent_request(); } return block; } #if defined(__linux__) /** * poll_fault_page: try to get next UFFD write fault page and, if pending fault * is found, return RAM block pointer and page offset * * Returns pointer to the RAMBlock containing faulting page, * NULL if no write faults are pending * * @rs: current RAM state * @offset: page offset from the beginning of the block */ static RAMBlock *poll_fault_page(RAMState *rs, ram_addr_t *offset) { struct uffd_msg uffd_msg; void *page_address; RAMBlock *block; int res; if (!migrate_background_snapshot()) { return NULL; } res = uffd_read_events(rs->uffdio_fd, &uffd_msg, 1); if (res <= 0) { return NULL; } page_address = (void *)(uintptr_t) uffd_msg.arg.pagefault.address; block = qemu_ram_block_from_host(page_address, false, offset); assert(block && (block->flags & RAM_UF_WRITEPROTECT) != 0); return block; } /** * ram_save_release_protection: release UFFD write protection after * a range of pages has been saved * * @rs: current RAM state * @pss: page-search-status structure * @start_page: index of the first page in the range relative to pss->block * * Returns 0 on success, negative value in case of an error */ static int ram_save_release_protection(RAMState *rs, PageSearchStatus *pss, unsigned long start_page) { int res = 0; /* Check if page is from UFFD-managed region. */ if (pss->block->flags & RAM_UF_WRITEPROTECT) { void *page_address = pss->block->host + (start_page << TARGET_PAGE_BITS); uint64_t run_length = (pss->page - start_page) << TARGET_PAGE_BITS; /* Flush async buffers before un-protect. */ qemu_fflush(pss->pss_channel); /* Un-protect memory range. */ res = uffd_change_protection(rs->uffdio_fd, page_address, run_length, false, false); } return res; } /* ram_write_tracking_available: check if kernel supports required UFFD features * * Returns true if supports, false otherwise */ bool ram_write_tracking_available(void) { uint64_t uffd_features; int res; res = uffd_query_features(&uffd_features); return (res == 0 && (uffd_features & UFFD_FEATURE_PAGEFAULT_FLAG_WP) != 0); } /* ram_write_tracking_compatible: check if guest configuration is * compatible with 'write-tracking' * * Returns true if compatible, false otherwise */ bool ram_write_tracking_compatible(void) { const uint64_t uffd_ioctls_mask = BIT(_UFFDIO_WRITEPROTECT); int uffd_fd; RAMBlock *block; bool ret = false; /* Open UFFD file descriptor */ uffd_fd = uffd_create_fd(UFFD_FEATURE_PAGEFAULT_FLAG_WP, false); if (uffd_fd < 0) { return false; } RCU_READ_LOCK_GUARD(); RAMBLOCK_FOREACH_NOT_IGNORED(block) { uint64_t uffd_ioctls; /* Nothing to do with read-only and MMIO-writable regions */ if (block->mr->readonly || block->mr->rom_device) { continue; } /* Try to register block memory via UFFD-IO to track writes */ if (uffd_register_memory(uffd_fd, block->host, block->max_length, UFFDIO_REGISTER_MODE_WP, &uffd_ioctls)) { goto out; } if ((uffd_ioctls & uffd_ioctls_mask) != uffd_ioctls_mask) { goto out; } } ret = true; out: uffd_close_fd(uffd_fd); return ret; } static inline void populate_read_range(RAMBlock *block, ram_addr_t offset, ram_addr_t size) { const ram_addr_t end = offset + size; /* * We read one byte of each page; this will preallocate page tables if * required and populate the shared zeropage on MAP_PRIVATE anonymous memory * where no page was populated yet. This might require adaption when * supporting other mappings, like shmem. */ for (; offset < end; offset += block->page_size) { char tmp = *((char *)block->host + offset); /* Don't optimize the read out */ asm volatile("" : "+r" (tmp)); } } static inline int populate_read_section(MemoryRegionSection *section, void *opaque) { const hwaddr size = int128_get64(section->size); hwaddr offset = section->offset_within_region; RAMBlock *block = section->mr->ram_block; populate_read_range(block, offset, size); return 0; } /* * ram_block_populate_read: preallocate page tables and populate pages in the * RAM block by reading a byte of each page. * * Since it's solely used for userfault_fd WP feature, here we just * hardcode page size to qemu_real_host_page_size. * * @block: RAM block to populate */ static void ram_block_populate_read(RAMBlock *rb) { /* * Skip populating all pages that fall into a discarded range as managed by * a RamDiscardManager responsible for the mapped memory region of the * RAMBlock. Such discarded ("logically unplugged") parts of a RAMBlock * must not get populated automatically. We don't have to track * modifications via userfaultfd WP reliably, because these pages will * not be part of the migration stream either way -- see * ramblock_dirty_bitmap_exclude_discarded_pages(). * * Note: The result is only stable while migrating (precopy/postcopy). */ if (rb->mr && memory_region_has_ram_discard_manager(rb->mr)) { RamDiscardManager *rdm = memory_region_get_ram_discard_manager(rb->mr); MemoryRegionSection section = { .mr = rb->mr, .offset_within_region = 0, .size = rb->mr->size, }; ram_discard_manager_replay_populated(rdm, §ion, populate_read_section, NULL); } else { populate_read_range(rb, 0, rb->used_length); } } /* * ram_write_tracking_prepare: prepare for UFFD-WP memory tracking */ void ram_write_tracking_prepare(void) { RAMBlock *block; RCU_READ_LOCK_GUARD(); RAMBLOCK_FOREACH_NOT_IGNORED(block) { /* Nothing to do with read-only and MMIO-writable regions */ if (block->mr->readonly || block->mr->rom_device) { continue; } /* * Populate pages of the RAM block before enabling userfault_fd * write protection. * * This stage is required since ioctl(UFFDIO_WRITEPROTECT) with * UFFDIO_WRITEPROTECT_MODE_WP mode setting would silently skip * pages with pte_none() entries in page table. */ ram_block_populate_read(block); } } static inline int uffd_protect_section(MemoryRegionSection *section, void *opaque) { const hwaddr size = int128_get64(section->size); const hwaddr offset = section->offset_within_region; RAMBlock *rb = section->mr->ram_block; int uffd_fd = (uintptr_t)opaque; return uffd_change_protection(uffd_fd, rb->host + offset, size, true, false); } static int ram_block_uffd_protect(RAMBlock *rb, int uffd_fd) { assert(rb->flags & RAM_UF_WRITEPROTECT); /* See ram_block_populate_read() */ if (rb->mr && memory_region_has_ram_discard_manager(rb->mr)) { RamDiscardManager *rdm = memory_region_get_ram_discard_manager(rb->mr); MemoryRegionSection section = { .mr = rb->mr, .offset_within_region = 0, .size = rb->mr->size, }; return ram_discard_manager_replay_populated(rdm, §ion, uffd_protect_section, (void *)(uintptr_t)uffd_fd); } return uffd_change_protection(uffd_fd, rb->host, rb->used_length, true, false); } /* * ram_write_tracking_start: start UFFD-WP memory tracking * * Returns 0 for success or negative value in case of error */ int ram_write_tracking_start(void) { int uffd_fd; RAMState *rs = ram_state; RAMBlock *block; /* Open UFFD file descriptor */ uffd_fd = uffd_create_fd(UFFD_FEATURE_PAGEFAULT_FLAG_WP, true); if (uffd_fd < 0) { return uffd_fd; } rs->uffdio_fd = uffd_fd; RCU_READ_LOCK_GUARD(); RAMBLOCK_FOREACH_NOT_IGNORED(block) { /* Nothing to do with read-only and MMIO-writable regions */ if (block->mr->readonly || block->mr->rom_device) { continue; } /* Register block memory with UFFD to track writes */ if (uffd_register_memory(rs->uffdio_fd, block->host, block->max_length, UFFDIO_REGISTER_MODE_WP, NULL)) { goto fail; } block->flags |= RAM_UF_WRITEPROTECT; memory_region_ref(block->mr); /* Apply UFFD write protection to the block memory range */ if (ram_block_uffd_protect(block, uffd_fd)) { goto fail; } trace_ram_write_tracking_ramblock_start(block->idstr, block->page_size, block->host, block->max_length); } return 0; fail: error_report("ram_write_tracking_start() failed: restoring initial memory state"); RAMBLOCK_FOREACH_NOT_IGNORED(block) { if ((block->flags & RAM_UF_WRITEPROTECT) == 0) { continue; } uffd_unregister_memory(rs->uffdio_fd, block->host, block->max_length); /* Cleanup flags and remove reference */ block->flags &= ~RAM_UF_WRITEPROTECT; memory_region_unref(block->mr); } uffd_close_fd(uffd_fd); rs->uffdio_fd = -1; return -1; } /** * ram_write_tracking_stop: stop UFFD-WP memory tracking and remove protection */ void ram_write_tracking_stop(void) { RAMState *rs = ram_state; RAMBlock *block; RCU_READ_LOCK_GUARD(); RAMBLOCK_FOREACH_NOT_IGNORED(block) { if ((block->flags & RAM_UF_WRITEPROTECT) == 0) { continue; } uffd_unregister_memory(rs->uffdio_fd, block->host, block->max_length); trace_ram_write_tracking_ramblock_stop(block->idstr, block->page_size, block->host, block->max_length); /* Cleanup flags and remove reference */ block->flags &= ~RAM_UF_WRITEPROTECT; memory_region_unref(block->mr); } /* Finally close UFFD file descriptor */ uffd_close_fd(rs->uffdio_fd); rs->uffdio_fd = -1; } #else /* No target OS support, stubs just fail or ignore */ static RAMBlock *poll_fault_page(RAMState *rs, ram_addr_t *offset) { (void) rs; (void) offset; return NULL; } static int ram_save_release_protection(RAMState *rs, PageSearchStatus *pss, unsigned long start_page) { (void) rs; (void) pss; (void) start_page; return 0; } bool ram_write_tracking_available(void) { return false; } bool ram_write_tracking_compatible(void) { assert(0); return false; } int ram_write_tracking_start(void) { assert(0); return -1; } void ram_write_tracking_stop(void) { assert(0); } #endif /* defined(__linux__) */ /** * get_queued_page: unqueue a page from the postcopy requests * * Skips pages that are already sent (!dirty) * * Returns true if a queued page is found * * @rs: current RAM state * @pss: data about the state of the current dirty page scan */ static bool get_queued_page(RAMState *rs, PageSearchStatus *pss) { RAMBlock *block; ram_addr_t offset; bool dirty; do { block = unqueue_page(rs, &offset); /* * 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 page; page = offset >> TARGET_PAGE_BITS; dirty = test_bit(page, block->bmap); if (!dirty) { trace_get_queued_page_not_dirty(block->idstr, (uint64_t)offset, page); } else { trace_get_queued_page(block->idstr, (uint64_t)offset, page); } } } while (block && !dirty); if (!block) { /* * Poll write faults too if background snapshot is enabled; that's * when we have vcpus got blocked by the write protected pages. */ block = poll_fault_page(rs, &offset); } if (block) { /* * 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->page = offset >> TARGET_PAGE_BITS; /* * This unqueued page would break the "one round" check, even is * really rare. */ pss->complete_round = false; } return !!block; } /** * migration_page_queue_free: drop 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. in case that there is any page left, we drop it. * */ static void migration_page_queue_free(RAMState *rs) { struct RAMSrcPageRequest *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_GUARD(); QSIMPLEQ_FOREACH_SAFE(mspr, &rs->src_page_requests, next_req, next_mspr) { memory_region_unref(mspr->rb->mr); QSIMPLEQ_REMOVE_HEAD(&rs->src_page_requests, next_req); g_free(mspr); } } /** * ram_save_queue_pages: queue the page for transmission * * A request from postcopy destination for example. * * Returns zero on success or negative on error * * @rbname: Name of the RAMBLock of the request. NULL means the * same that last one. * @start: starting address from the start of the RAMBlock * @len: length (in bytes) to send */ int ram_save_queue_pages(const char *rbname, ram_addr_t start, ram_addr_t len) { RAMBlock *ramblock; RAMState *rs = ram_state; stat64_add(&mig_stats.postcopy_requests, 1); RCU_READ_LOCK_GUARD(); if (!rbname) { /* Reuse last RAMBlock */ ramblock = rs->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"); return -1; } } 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); return -1; } rs->last_req_rb = ramblock; } trace_ram_save_queue_pages(ramblock->idstr, start, len); if (!offset_in_ramblock(ramblock, start + len - 1)) { error_report("%s request overrun start=" RAM_ADDR_FMT " len=" RAM_ADDR_FMT " blocklen=" RAM_ADDR_FMT, __func__, start, len, ramblock->used_length); return -1; } /* * When with postcopy preempt, we send back the page directly in the * rp-return thread. */ if (postcopy_preempt_active()) { ram_addr_t page_start = start >> TARGET_PAGE_BITS; size_t page_size = qemu_ram_pagesize(ramblock); PageSearchStatus *pss = &ram_state->pss[RAM_CHANNEL_POSTCOPY]; int ret = 0; qemu_mutex_lock(&rs->bitmap_mutex); pss_init(pss, ramblock, page_start); /* * Always use the preempt channel, and make sure it's there. It's * safe to access without lock, because when rp-thread is running * we should be the only one who operates on the qemufile */ pss->pss_channel = migrate_get_current()->postcopy_qemufile_src; assert(pss->pss_channel); /* * It must be either one or multiple of host page size. Just * assert; if something wrong we're mostly split brain anyway. */ assert(len % page_size == 0); while (len) { if (ram_save_host_page_urgent(pss)) { error_report("%s: ram_save_host_page_urgent() failed: " "ramblock=%s, start_addr=0x"RAM_ADDR_FMT, __func__, ramblock->idstr, start); ret = -1; break; } /* * NOTE: after ram_save_host_page_urgent() succeeded, pss->page * will automatically be moved and point to the next host page * we're going to send, so no need to update here. * * Normally QEMU never sends >1 host page in requests, so * logically we don't even need that as the loop should only * run once, but just to be consistent. */ len -= page_size; }; qemu_mutex_unlock(&rs->bitmap_mutex); return ret; } struct RAMSrcPageRequest *new_entry = g_new0(struct RAMSrcPageRequest, 1); new_entry->rb = ramblock; new_entry->offset = start; new_entry->len = len; memory_region_ref(ramblock->mr); qemu_mutex_lock(&rs->src_page_req_mutex); QSIMPLEQ_INSERT_TAIL(&rs->src_page_requests, new_entry, next_req); migration_make_urgent_request(); qemu_mutex_unlock(&rs->src_page_req_mutex); return 0; } static bool save_page_use_compression(RAMState *rs) { if (!migrate_compress()) { return false; } /* * If xbzrle is enabled (e.g., after first round of migration), stop * using the data compression. In theory, xbzrle can do better than * compression. */ if (rs->xbzrle_started) { return false; } return true; } /* * try to compress the page before posting it out, return true if the page * has been properly handled by compression, otherwise needs other * paths to handle it */ static bool save_compress_page(RAMState *rs, PageSearchStatus *pss, RAMBlock *block, ram_addr_t offset) { if (!save_page_use_compression(rs)) { return false; } /* * 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. * * We post the fist page as normal page as compression will take * much CPU resource. */ if (block != pss->last_sent_block) { ram_flush_compressed_data(rs); return false; } if (compress_page_with_multi_thread(block, offset, send_queued_data) > 0) { return true; } compression_counters.busy++; return false; } /** * ram_save_target_page_legacy: save one target page * * Returns the number of pages written * * @rs: current RAM state * @pss: data about the page we want to send */ static int ram_save_target_page_legacy(RAMState *rs, PageSearchStatus *pss) { RAMBlock *block = pss->block; ram_addr_t offset = ((ram_addr_t)pss->page) << TARGET_PAGE_BITS; int res; if (control_save_page(pss, block, offset, &res)) { return res; } if (save_compress_page(rs, pss, block, offset)) { return 1; } if (save_zero_page(rs, pss, block, offset)) { return 1; } /* * Do not use multifd in postcopy as one whole host page should be * placed. Meanwhile postcopy requires atomic update of pages, so even * if host page size == guest page size the dest guest during run may * still see partially copied pages which is data corruption. */ if (migrate_multifd() && !migration_in_postcopy()) { return ram_save_multifd_page(pss->pss_channel, block, offset); } return ram_save_page(rs, pss); } /* Should be called before sending a host page */ static void pss_host_page_prepare(PageSearchStatus *pss) { /* How many guest pages are there in one host page? */ size_t guest_pfns = qemu_ram_pagesize(pss->block) >> TARGET_PAGE_BITS; pss->host_page_sending = true; if (guest_pfns <= 1) { /* * This covers both when guest psize == host psize, or when guest * has larger psize than the host (guest_pfns==0). * * For the latter, we always send one whole guest page per * iteration of the host page (example: an Alpha VM on x86 host * will have guest psize 8K while host psize 4K). */ pss->host_page_start = pss->page; pss->host_page_end = pss->page + 1; } else { /* * The host page spans over multiple guest pages, we send them * within the same host page iteration. */ pss->host_page_start = ROUND_DOWN(pss->page, guest_pfns); pss->host_page_end = ROUND_UP(pss->page + 1, guest_pfns); } } /* * Whether the page pointed by PSS is within the host page being sent. * Must be called after a previous pss_host_page_prepare(). */ static bool pss_within_range(PageSearchStatus *pss) { ram_addr_t ram_addr; assert(pss->host_page_sending); /* Over host-page boundary? */ if (pss->page >= pss->host_page_end) { return false; } ram_addr = ((ram_addr_t)pss->page) << TARGET_PAGE_BITS; return offset_in_ramblock(pss->block, ram_addr); } static void pss_host_page_finish(PageSearchStatus *pss) { pss->host_page_sending = false; /* This is not needed, but just to reset it */ pss->host_page_start = pss->host_page_end = 0; } /* * Send an urgent host page specified by `pss'. Need to be called with * bitmap_mutex held. * * Returns 0 if save host page succeeded, false otherwise. */ static int ram_save_host_page_urgent(PageSearchStatus *pss) { bool page_dirty, sent = false; RAMState *rs = ram_state; int ret = 0; trace_postcopy_preempt_send_host_page(pss->block->idstr, pss->page); pss_host_page_prepare(pss); /* * If precopy is sending the same page, let it be done in precopy, or * we could send the same page in two channels and none of them will * receive the whole page. */ if (pss_overlap(pss, &ram_state->pss[RAM_CHANNEL_PRECOPY])) { trace_postcopy_preempt_hit(pss->block->idstr, pss->page << TARGET_PAGE_BITS); return 0; } do { page_dirty = migration_bitmap_clear_dirty(rs, pss->block, pss->page); if (page_dirty) { /* Be strict to return code; it must be 1, or what else? */ if (migration_ops->ram_save_target_page(rs, pss) != 1) { error_report_once("%s: ram_save_target_page failed", __func__); ret = -1; goto out; } sent = true; } pss_find_next_dirty(pss); } while (pss_within_range(pss)); out: pss_host_page_finish(pss); /* For urgent requests, flush immediately if sent */ if (sent) { qemu_fflush(pss->pss_channel); } return ret; } /** * ram_save_host_page: save a whole 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. Note that the host page size may * be a huge page for this block. * * The saving stops at the boundary of the used_length of the block * if the RAMBlock isn't a multiple of the host page size. * * The caller must be with ram_state.bitmap_mutex held to call this * function. Note that this function can temporarily release the lock, but * when the function is returned it'll make sure the lock is still held. * * Returns the number of pages written or negative on error * * @rs: current RAM state * @pss: data about the page we want to send */ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss) { bool page_dirty, preempt_active = postcopy_preempt_active(); int tmppages, pages = 0; size_t pagesize_bits = qemu_ram_pagesize(pss->block) >> TARGET_PAGE_BITS; unsigned long start_page = pss->page; int res; if (migrate_ram_is_ignored(pss->block)) { error_report("block %s should not be migrated !", pss->block->idstr); return 0; } /* Update host page boundary information */ pss_host_page_prepare(pss); do { page_dirty = migration_bitmap_clear_dirty(rs, pss->block, pss->page); /* Check the pages is dirty and if it is send it */ if (page_dirty) { /* * Properly yield the lock only in postcopy preempt mode * because both migration thread and rp-return thread can * operate on the bitmaps. */ if (preempt_active) { qemu_mutex_unlock(&rs->bitmap_mutex); } tmppages = migration_ops->ram_save_target_page(rs, pss); if (tmppages >= 0) { pages += tmppages; /* * Allow rate limiting to happen in the middle of huge pages if * something is sent in the current iteration. */ if (pagesize_bits > 1 && tmppages > 0) { migration_rate_limit(); } } if (preempt_active) { qemu_mutex_lock(&rs->bitmap_mutex); } } else { tmppages = 0; } if (tmppages < 0) { pss_host_page_finish(pss); return tmppages; } pss_find_next_dirty(pss); } while (pss_within_range(pss)); pss_host_page_finish(pss); res = ram_save_release_protection(rs, pss, start_page); return (res < 0 ? res : 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 where zero means no dirty pages, * or negative on error * * @rs: current RAM state * * 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(RAMState *rs) { PageSearchStatus *pss = &rs->pss[RAM_CHANNEL_PRECOPY]; int pages = 0; /* No dirty page as there is zero RAM */ if (!rs->ram_bytes_total) { return pages; } /* * Always keep last_seen_block/last_page valid during this procedure, * because find_dirty_block() relies on these values (e.g., we compare * last_seen_block with pss.block to see whether we searched all the * ramblocks) to detect the completion of migration. Having NULL value * of last_seen_block can conditionally cause below loop to run forever. */ if (!rs->last_seen_block) { rs->last_seen_block = QLIST_FIRST_RCU(&ram_list.blocks); rs->last_page = 0; } pss_init(pss, rs->last_seen_block, rs->last_page); while (true){ if (!get_queued_page(rs, pss)) { /* priority queue empty, so just search for something dirty */ int res = find_dirty_block(rs, pss); if (res != PAGE_DIRTY_FOUND) { if (res == PAGE_ALL_CLEAN) { break; } else if (res == PAGE_TRY_AGAIN) { continue; } else if (res < 0) { pages = res; break; } } } pages = ram_save_host_page(rs, pss); if (pages) { break; } } rs->last_seen_block = pss->block; rs->last_page = pss->page; return pages; } static uint64_t ram_bytes_total_with_ignored(void) { RAMBlock *block; uint64_t total = 0; RCU_READ_LOCK_GUARD(); RAMBLOCK_FOREACH_MIGRATABLE(block) { total += block->used_length; } return total; } uint64_t ram_bytes_total(void) { RAMBlock *block; uint64_t total = 0; RCU_READ_LOCK_GUARD(); RAMBLOCK_FOREACH_NOT_IGNORED(block) { total += block->used_length; } return total; } static void xbzrle_load_setup(void) { XBZRLE.decoded_buf = g_malloc(TARGET_PAGE_SIZE); } static void xbzrle_load_cleanup(void) { g_free(XBZRLE.decoded_buf); XBZRLE.decoded_buf = NULL; } static void ram_state_cleanup(RAMState **rsp) { if (*rsp) { migration_page_queue_free(*rsp); qemu_mutex_destroy(&(*rsp)->bitmap_mutex); qemu_mutex_destroy(&(*rsp)->src_page_req_mutex); g_free(*rsp); *rsp = NULL; } } static void xbzrle_cleanup(void) { XBZRLE_cache_lock(); if (XBZRLE.cache) { cache_fini(XBZRLE.cache); g_free(XBZRLE.encoded_buf); g_free(XBZRLE.current_buf); g_free(XBZRLE.zero_target_page); XBZRLE.cache = NULL; XBZRLE.encoded_buf = NULL; XBZRLE.current_buf = NULL; XBZRLE.zero_target_page = NULL; } XBZRLE_cache_unlock(); } static void ram_save_cleanup(void *opaque) { RAMState **rsp = opaque; RAMBlock *block; /* We don't use dirty log with background snapshots */ if (!migrate_background_snapshot()) { /* caller have hold iothread lock or is in a bh, so there is * no writing race against the migration bitmap */ if (global_dirty_tracking & GLOBAL_DIRTY_MIGRATION) { /* * do not stop dirty log without starting it, since * memory_global_dirty_log_stop will assert that * memory_global_dirty_log_start/stop used in pairs */ memory_global_dirty_log_stop(GLOBAL_DIRTY_MIGRATION); } } RAMBLOCK_FOREACH_NOT_IGNORED(block) { g_free(block->clear_bmap); block->clear_bmap = NULL; g_free(block->bmap); block->bmap = NULL; } xbzrle_cleanup(); compress_threads_save_cleanup(); ram_state_cleanup(rsp); g_free(migration_ops); migration_ops = NULL; } static void ram_state_reset(RAMState *rs) { int i; for (i = 0; i < RAM_CHANNEL_MAX; i++) { rs->pss[i].last_sent_block = NULL; } rs->last_seen_block = NULL; rs->last_page = 0; rs->last_version = ram_list.version; rs->xbzrle_started = false; } #define MAX_WAIT 50 /* ms, half buffered_file limit */ /* **** functions for postcopy ***** */ void ram_postcopy_migrated_memory_release(MigrationState *ms) { struct RAMBlock *block; RAMBLOCK_FOREACH_NOT_IGNORED(block) { unsigned long *bitmap = block->bmap; unsigned long range = block->used_length >> TARGET_PAGE_BITS; unsigned long run_start = find_next_zero_bit(bitmap, range, 0); while (run_start < range) { unsigned long run_end = find_next_bit(bitmap, range, run_start + 1); ram_discard_range(block->idstr, ((ram_addr_t)run_start) << TARGET_PAGE_BITS, ((ram_addr_t)(run_end - run_start)) << TARGET_PAGE_BITS); run_start = find_next_zero_bit(bitmap, range, run_end + 1); } } } /** * postcopy_send_discard_bm_ram: discard a RAMBlock * * Callback from postcopy_each_ram_send_discard for each RAMBlock * * @ms: current migration state * @block: RAMBlock to discard */ static void postcopy_send_discard_bm_ram(MigrationState *ms, RAMBlock *block) { unsigned long end = block->used_length >> TARGET_PAGE_BITS; unsigned long current; unsigned long *bitmap = block->bmap; for (current = 0; current < end; ) { unsigned long one = find_next_bit(bitmap, end, current); unsigned long zero, discard_length; if (one >= end) { break; } zero = find_next_zero_bit(bitmap, end, one + 1); if (zero >= end) { discard_length = end - one; } else { discard_length = zero - one; } postcopy_discard_send_range(ms, one, discard_length); current = one + discard_length; } } static void postcopy_chunk_hostpages_pass(MigrationState *ms, RAMBlock *block); /** * postcopy_each_ram_send_discard: discard all RAMBlocks * * Utility for the outgoing postcopy code. * Calls postcopy_send_discard_bm_ram for each RAMBlock * passing it bitmap indexes and name. * (qemu_ram_foreach_block ends up passing unscaled lengths * which would mean postcopy code would have to deal with target page) * * @ms: current migration state */ static void postcopy_each_ram_send_discard(MigrationState *ms) { struct RAMBlock *block; RAMBLOCK_FOREACH_NOT_IGNORED(block) { postcopy_discard_send_init(ms, block->idstr); /* * Deal with TPS != HPS and huge pages. It discard any partially sent * host-page size chunks, mark any partially dirty host-page size * chunks as all dirty. In this case the host-page is the host-page * for the particular RAMBlock, i.e. it might be a huge page. */ postcopy_chunk_hostpages_pass(ms, block); /* * Postcopy sends chunks of bitmap over the wire, but it * just needs indexes at this point, avoids it having * target page specific code. */ postcopy_send_discard_bm_ram(ms, block); postcopy_discard_send_finish(ms); } } /** * postcopy_chunk_hostpages_pass: canonicalize bitmap in hostpages * * Helper for postcopy_chunk_hostpages; it's called twice to * canonicalize the two bitmaps, that are similar, but one is * inverted. * * Postcopy requires that all target pages in a hostpage are dirty or * clean, not a mix. This function canonicalizes the bitmaps. * * @ms: current migration state * @block: block that contains the page we want to canonicalize */ static void postcopy_chunk_hostpages_pass(MigrationState *ms, RAMBlock *block) { RAMState *rs = ram_state; unsigned long *bitmap = block->bmap; unsigned int host_ratio = block->page_size / TARGET_PAGE_SIZE; unsigned long pages = block->used_length >> TARGET_PAGE_BITS; unsigned long run_start; if (block->page_size == TARGET_PAGE_SIZE) { /* Easy case - TPS==HPS for a non-huge page RAMBlock */ return; } /* Find a dirty page */ run_start = find_next_bit(bitmap, pages, 0); while (run_start < pages) { /* * If the start of this run of pages is in the middle of a host * page, then we need to fixup this host page. */ if (QEMU_IS_ALIGNED(run_start, host_ratio)) { /* Find the end of this run */ run_start = find_next_zero_bit(bitmap, pages, 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. */ } if (!QEMU_IS_ALIGNED(run_start, host_ratio)) { unsigned long page; unsigned long fixup_start_addr = QEMU_ALIGN_DOWN(run_start, host_ratio); run_start = QEMU_ALIGN_UP(run_start, host_ratio); /* Clean up the bitmap */ for (page = fixup_start_addr; page < fixup_start_addr + host_ratio; page++) { /* * Remark them as dirty, updating the count for any pages * that weren't previously dirty. */ rs->migration_dirty_pages += !test_and_set_bit(page, bitmap); } } /* Find the next dirty page for the next iteration */ run_start = find_next_bit(bitmap, pages, run_start); } } /** * ram_postcopy_send_discard_bitmap: transmit the discard bitmap * * 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 * * @ms: current migration state */ void ram_postcopy_send_discard_bitmap(MigrationState *ms) { RAMState *rs = ram_state; RCU_READ_LOCK_GUARD(); /* This should be our last sync, the src is now paused */ migration_bitmap_sync(rs, false); /* Easiest way to make sure we don't resume in the middle of a host-page */ rs->pss[RAM_CHANNEL_PRECOPY].last_sent_block = NULL; rs->last_seen_block = NULL; rs->last_page = 0; postcopy_each_ram_send_discard(ms); trace_ram_postcopy_send_discard_bitmap(); } /** * ram_discard_range: discard dirtied pages at the beginning of postcopy * * Returns zero on success * * @rbname: name of the RAMBlock of the request. NULL means the * same that last one. * @start: RAMBlock starting page * @length: RAMBlock size */ int ram_discard_range(const char *rbname, uint64_t start, size_t length) { trace_ram_discard_range(rbname, start, length); RCU_READ_LOCK_GUARD(); RAMBlock *rb = qemu_ram_block_by_name(rbname); if (!rb) { error_report("ram_discard_range: Failed to find block '%s'", rbname); return -1; } /* * On source VM, we don't need to update the received bitmap since * we don't even have one. */ if (rb->receivedmap) { bitmap_clear(rb->receivedmap, start >> qemu_target_page_bits(), length >> qemu_target_page_bits()); } return ram_block_discard_range(rb, start, length); } /* * For every allocation, we will try not to crash the VM if the * allocation failed. */ static int xbzrle_init(void) { Error *local_err = NULL; if (!migrate_xbzrle()) { return 0; } XBZRLE_cache_lock(); XBZRLE.zero_target_page = g_try_malloc0(TARGET_PAGE_SIZE); if (!XBZRLE.zero_target_page) { error_report("%s: Error allocating zero page", __func__); goto err_out; } XBZRLE.cache = cache_init(migrate_xbzrle_cache_size(), TARGET_PAGE_SIZE, &local_err); if (!XBZRLE.cache) { error_report_err(local_err); goto free_zero_page; } XBZRLE.encoded_buf = g_try_malloc0(TARGET_PAGE_SIZE); if (!XBZRLE.encoded_buf) { error_report("%s: Error allocating encoded_buf", __func__); goto free_cache; } XBZRLE.current_buf = g_try_malloc(TARGET_PAGE_SIZE); if (!XBZRLE.current_buf) { error_report("%s: Error allocating current_buf", __func__); goto free_encoded_buf; } /* We are all good */ XBZRLE_cache_unlock(); return 0; free_encoded_buf: g_free(XBZRLE.encoded_buf); XBZRLE.encoded_buf = NULL; free_cache: cache_fini(XBZRLE.cache); XBZRLE.cache = NULL; free_zero_page: g_free(XBZRLE.zero_target_page); XBZRLE.zero_target_page = NULL; err_out: XBZRLE_cache_unlock(); return -ENOMEM; } static int ram_state_init(RAMState **rsp) { *rsp = g_try_new0(RAMState, 1); if (!*rsp) { error_report("%s: Init ramstate fail", __func__); return -1; } qemu_mutex_init(&(*rsp)->bitmap_mutex); qemu_mutex_init(&(*rsp)->src_page_req_mutex); QSIMPLEQ_INIT(&(*rsp)->src_page_requests); (*rsp)->ram_bytes_total = ram_bytes_total(); /* * Count the total number of pages used by ram blocks not including any * gaps due to alignment or unplugs. * This must match with the initial values of dirty bitmap. */ (*rsp)->migration_dirty_pages = (*rsp)->ram_bytes_total >> TARGET_PAGE_BITS; ram_state_reset(*rsp); return 0; } static void ram_list_init_bitmaps(void) { MigrationState *ms = migrate_get_current(); RAMBlock *block; unsigned long pages; uint8_t shift; /* Skip setting bitmap if there is no RAM */ if (ram_bytes_total()) { shift = ms->clear_bitmap_shift; if (shift > CLEAR_BITMAP_SHIFT_MAX) { error_report("clear_bitmap_shift (%u) too big, using " "max value (%u)", shift, CLEAR_BITMAP_SHIFT_MAX); shift = CLEAR_BITMAP_SHIFT_MAX; } else if (shift < CLEAR_BITMAP_SHIFT_MIN) { error_report("clear_bitmap_shift (%u) too small, using " "min value (%u)", shift, CLEAR_BITMAP_SHIFT_MIN); shift = CLEAR_BITMAP_SHIFT_MIN; } RAMBLOCK_FOREACH_NOT_IGNORED(block) { pages = block->max_length >> TARGET_PAGE_BITS; /* * The initial dirty bitmap for migration must be set with all * ones to make sure we'll migrate every guest RAM page to * destination. * Here we set RAMBlock.bmap all to 1 because when rebegin a * new migration after a failed migration, ram_list. * dirty_memory[DIRTY_MEMORY_MIGRATION] don't include the whole * guest memory. */ block->bmap = bitmap_new(pages); bitmap_set(block->bmap, 0, pages); block->clear_bmap_shift = shift; block->clear_bmap = bitmap_new(clear_bmap_size(pages, shift)); } } } static void migration_bitmap_clear_discarded_pages(RAMState *rs) { unsigned long pages; RAMBlock *rb; RCU_READ_LOCK_GUARD(); RAMBLOCK_FOREACH_NOT_IGNORED(rb) { pages = ramblock_dirty_bitmap_clear_discarded_pages(rb); rs->migration_dirty_pages -= pages; } } static void ram_init_bitmaps(RAMState *rs) { qemu_mutex_lock_ramlist(); WITH_RCU_READ_LOCK_GUARD() { ram_list_init_bitmaps(); /* We don't use dirty log with background snapshots */ if (!migrate_background_snapshot()) { memory_global_dirty_log_start(GLOBAL_DIRTY_MIGRATION); migration_bitmap_sync_precopy(rs, false); } } qemu_mutex_unlock_ramlist(); /* * After an eventual first bitmap sync, fixup the initial bitmap * containing all 1s to exclude any discarded pages from migration. */ migration_bitmap_clear_discarded_pages(rs); } static int ram_init_all(RAMState **rsp) { if (ram_state_init(rsp)) { return -1; } if (xbzrle_init()) { ram_state_cleanup(rsp); return -1; } ram_init_bitmaps(*rsp); return 0; } static void ram_state_resume_prepare(RAMState *rs, QEMUFile *out) { RAMBlock *block; uint64_t pages = 0; /* * Postcopy is not using xbzrle/compression, so no need for that. * Also, since source are already halted, we don't need to care * about dirty page logging as well. */ RAMBLOCK_FOREACH_NOT_IGNORED(block) { pages += bitmap_count_one(block->bmap, block->used_length >> TARGET_PAGE_BITS); } /* This may not be aligned with current bitmaps. Recalculate. */ rs->migration_dirty_pages = pages; ram_state_reset(rs); /* Update RAMState cache of output QEMUFile */ rs->pss[RAM_CHANNEL_PRECOPY].pss_channel = out; trace_ram_state_resume_prepare(pages); } /* * This function clears bits of the free pages reported by the caller from the * migration dirty bitmap. @addr is the host address corresponding to the * start of the continuous guest free pages, and @len is the total bytes of * those pages. */ void qemu_guest_free_page_hint(void *addr, size_t len) { RAMBlock *block; ram_addr_t offset; size_t used_len, start, npages; MigrationState *s = migrate_get_current(); /* This function is currently expected to be used during live migration */ if (!migration_is_setup_or_active(s->state)) { return; } for (; len > 0; len -= used_len, addr += used_len) { block = qemu_ram_block_from_host(addr, false, &offset); if (unlikely(!block || offset >= block->used_length)) { /* * The implementation might not support RAMBlock resize during * live migration, but it could happen in theory with future * updates. So we add a check here to capture that case. */ error_report_once("%s unexpected error", __func__); return; } if (len <= block->used_length - offset) { used_len = len; } else { used_len = block->used_length - offset; } start = offset >> TARGET_PAGE_BITS; npages = used_len >> TARGET_PAGE_BITS; qemu_mutex_lock(&ram_state->bitmap_mutex); /* * The skipped free pages are equavalent to be sent from clear_bmap's * perspective, so clear the bits from the memory region bitmap which * are initially set. Otherwise those skipped pages will be sent in * the next round after syncing from the memory region bitmap. */ migration_clear_memory_region_dirty_bitmap_range(block, start, npages); ram_state->migration_dirty_pages -= bitmap_count_one_with_offset(block->bmap, start, npages); bitmap_clear(block->bmap, start, npages); qemu_mutex_unlock(&ram_state->bitmap_mutex); } } /* * 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. */ /** * ram_save_setup: Setup RAM for migration * * Returns zero to indicate success and negative for error * * @f: QEMUFile where to send the data * @opaque: RAMState pointer */ static int ram_save_setup(QEMUFile *f, void *opaque) { RAMState **rsp = opaque; RAMBlock *block; int ret; if (compress_threads_save_setup()) { return -1; } /* migration has already setup the bitmap, reuse it. */ if (!migration_in_colo_state()) { if (ram_init_all(rsp) != 0) { compress_threads_save_cleanup(); return -1; } } (*rsp)->pss[RAM_CHANNEL_PRECOPY].pss_channel = f; WITH_RCU_READ_LOCK_GUARD() { qemu_put_be64(f, ram_bytes_total_with_ignored() | RAM_SAVE_FLAG_MEM_SIZE); RAMBLOCK_FOREACH_MIGRATABLE(block) { 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); if (migrate_postcopy_ram() && block->page_size != qemu_host_page_size) { qemu_put_be64(f, block->page_size); } if (migrate_ignore_shared()) { qemu_put_be64(f, block->mr->addr); } } } ret = rdma_registration_start(f, RAM_CONTROL_SETUP); if (ret < 0) { qemu_file_set_error(f, ret); } ret = rdma_registration_stop(f, RAM_CONTROL_SETUP); if (ret < 0) { qemu_file_set_error(f, ret); } migration_ops = g_malloc0(sizeof(MigrationOps)); migration_ops->ram_save_target_page = ram_save_target_page_legacy; qemu_mutex_unlock_iothread(); ret = multifd_send_sync_main(f); qemu_mutex_lock_iothread(); if (ret < 0) { return ret; } if (migrate_multifd() && !migrate_multifd_flush_after_each_section()) { qemu_put_be64(f, RAM_SAVE_FLAG_MULTIFD_FLUSH); } qemu_put_be64(f, RAM_SAVE_FLAG_EOS); qemu_fflush(f); return 0; } /** * ram_save_iterate: iterative stage for migration * * Returns zero to indicate success and negative for error * * @f: QEMUFile where to send the data * @opaque: RAMState pointer */ static int ram_save_iterate(QEMUFile *f, void *opaque) { RAMState **temp = opaque; RAMState *rs = *temp; int ret = 0; int i; int64_t t0; int done = 0; if (blk_mig_bulk_active()) { /* Avoid transferring ram during bulk phase of block migration as * the bulk phase will usually take a long time and transferring * ram updates during that time is pointless. */ goto out; } /* * We'll take this lock a little bit long, but it's okay for two reasons. * Firstly, the only possible other thread to take it is who calls * qemu_guest_free_page_hint(), which should be rare; secondly, see * MAX_WAIT (if curious, further see commit 4508bd9ed8053ce) below, which * guarantees that we'll at least released it in a regular basis. */ qemu_mutex_lock(&rs->bitmap_mutex); WITH_RCU_READ_LOCK_GUARD() { if (ram_list.version != rs->last_version) { ram_state_reset(rs); } /* Read version before ram_list.blocks */ smp_rmb(); ret = rdma_registration_start(f, RAM_CONTROL_ROUND); if (ret < 0) { qemu_file_set_error(f, ret); } t0 = qemu_clock_get_ns(QEMU_CLOCK_REALTIME); i = 0; while ((ret = migration_rate_exceeded(f)) == 0 || postcopy_has_request(rs)) { int pages; if (qemu_file_get_error(f)) { break; } pages = ram_find_and_save_block(rs); /* no more pages to sent */ if (pages == 0) { done = 1; break; } if (pages < 0) { qemu_file_set_error(f, pages); break; } rs->target_page_count += pages; /* * During postcopy, it is necessary to make sure one whole host * page is sent in one chunk. */ if (migrate_postcopy_ram()) { ram_flush_compressed_data(rs); } /* * 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_clock_get_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) { trace_ram_save_iterate_big_wait(t1, i); break; } } i++; } } qemu_mutex_unlock(&rs->bitmap_mutex); /* * Must occur before EOS (or any QEMUFile operation) * because of RDMA protocol. */ ret = rdma_registration_stop(f, RAM_CONTROL_ROUND); if (ret < 0) { qemu_file_set_error(f, ret); } out: if (ret >= 0 && migration_is_setup_or_active(migrate_get_current()->state)) { if (migrate_multifd() && migrate_multifd_flush_after_each_section()) { ret = multifd_send_sync_main(rs->pss[RAM_CHANNEL_PRECOPY].pss_channel); if (ret < 0) { return ret; } } qemu_put_be64(f, RAM_SAVE_FLAG_EOS); qemu_fflush(f); ram_transferred_add(8); ret = qemu_file_get_error(f); } if (ret < 0) { return ret; } return done; } /** * ram_save_complete: function called to send the remaining amount of ram * * Returns zero to indicate success or negative on error * * Called with iothread lock * * @f: QEMUFile where to send the data * @opaque: RAMState pointer */ static int ram_save_complete(QEMUFile *f, void *opaque) { RAMState **temp = opaque; RAMState *rs = *temp; int ret = 0; rs->last_stage = !migration_in_colo_state(); WITH_RCU_READ_LOCK_GUARD() { if (!migration_in_postcopy()) { migration_bitmap_sync_precopy(rs, true); } ret = rdma_registration_start(f, RAM_CONTROL_FINISH); if (ret < 0) { qemu_file_set_error(f, ret); } /* try transferring iterative blocks of memory */ /* flush all remaining blocks regardless of rate limiting */ qemu_mutex_lock(&rs->bitmap_mutex); while (true) { int pages; pages = ram_find_and_save_block(rs); /* no more blocks to sent */ if (pages == 0) { break; } if (pages < 0) { ret = pages; break; } } qemu_mutex_unlock(&rs->bitmap_mutex); ram_flush_compressed_data(rs); int ret = rdma_registration_stop(f, RAM_CONTROL_FINISH); if (ret < 0) { qemu_file_set_error(f, ret); } } if (ret < 0) { return ret; } ret = multifd_send_sync_main(rs->pss[RAM_CHANNEL_PRECOPY].pss_channel); if (ret < 0) { return ret; } if (migrate_multifd() && !migrate_multifd_flush_after_each_section()) { qemu_put_be64(f, RAM_SAVE_FLAG_MULTIFD_FLUSH); } qemu_put_be64(f, RAM_SAVE_FLAG_EOS); qemu_fflush(f); return 0; } static void ram_state_pending_estimate(void *opaque, uint64_t *must_precopy, uint64_t *can_postcopy) { RAMState **temp = opaque; RAMState *rs = *temp; uint64_t remaining_size = rs->migration_dirty_pages * TARGET_PAGE_SIZE; if (migrate_postcopy_ram()) { /* We can do postcopy, and all the data is postcopiable */ *can_postcopy += remaining_size; } else { *must_precopy += remaining_size; } } static void ram_state_pending_exact(void *opaque, uint64_t *must_precopy, uint64_t *can_postcopy) { MigrationState *s = migrate_get_current(); RAMState **temp = opaque; RAMState *rs = *temp; uint64_t remaining_size = rs->migration_dirty_pages * TARGET_PAGE_SIZE; if (!migration_in_postcopy() && remaining_size < s->threshold_size) { qemu_mutex_lock_iothread(); WITH_RCU_READ_LOCK_GUARD() { migration_bitmap_sync_precopy(rs, false); } qemu_mutex_unlock_iothread(); remaining_size = rs->migration_dirty_pages * TARGET_PAGE_SIZE; } if (migrate_postcopy_ram()) { /* We can do postcopy, and all the data is postcopiable */ *can_postcopy += remaining_size; } else { *must_precopy += 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; /* 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; } loaded_data = XBZRLE.decoded_buf; /* load data and decode */ /* it can change loaded_data to point to an internal buffer */ 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; } /** * ram_block_from_stream: read a RAMBlock id from the migration stream * * Must be called from within a rcu critical section. * * Returns a pointer from within the RCU-protected ram_list. * * @mis: the migration incoming state pointer * @f: QEMUFile where to read the data from * @flags: Page flags (mostly to see if it's a continuation of previous block) * @channel: the channel we're using */ static inline RAMBlock *ram_block_from_stream(MigrationIncomingState *mis, QEMUFile *f, int flags, int channel) { RAMBlock *block = mis->last_recv_block[channel]; 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; } if (migrate_ram_is_ignored(block)) { error_report("block %s should not be migrated !", id); return NULL; } mis->last_recv_block[channel] = block; 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; } static void *host_page_from_ram_block_offset(RAMBlock *block, ram_addr_t offset) { /* Note: Explicitly no check against offset_in_ramblock(). */ return (void *)QEMU_ALIGN_DOWN((uintptr_t)(block->host + offset), block->page_size); } static ram_addr_t host_page_offset_from_ram_block_offset(RAMBlock *block, ram_addr_t offset) { return ((uintptr_t)block->host + offset) & (block->page_size - 1); } void colo_record_bitmap(RAMBlock *block, ram_addr_t *normal, uint32_t pages) { qemu_mutex_lock(&ram_state->bitmap_mutex); for (int i = 0; i < pages; i++) { ram_addr_t offset = normal[i]; ram_state->migration_dirty_pages += !test_and_set_bit( offset >> TARGET_PAGE_BITS, block->bmap); } qemu_mutex_unlock(&ram_state->bitmap_mutex); } static inline void *colo_cache_from_block_offset(RAMBlock *block, ram_addr_t offset, bool record_bitmap) { if (!offset_in_ramblock(block, offset)) { return NULL; } if (!block->colo_cache) { error_report("%s: colo_cache is NULL in block :%s", __func__, block->idstr); return NULL; } /* * During colo checkpoint, we need bitmap of these migrated pages. * It help us to decide which pages in ram cache should be flushed * into VM's RAM later. */ if (record_bitmap) { colo_record_bitmap(block, &offset, 1); } return block->colo_cache + offset; } /** * ram_handle_compressed: handle the zero page case * * If a page (or a whole RDMA chunk) has been * determined to be zero, then zap it. * * @host: host address for the zero page * @ch: what the page is filled from. We only support zero * @size: size of the zero page */ void ram_handle_compressed(void *host, uint8_t ch, uint64_t size) { if (ch != 0 || !buffer_is_zero(host, size)) { memset(host, ch, size); } } static void colo_init_ram_state(void) { ram_state_init(&ram_state); } /* * colo cache: this is for secondary VM, we cache the whole * memory of the secondary VM, it is need to hold the global lock * to call this helper. */ int colo_init_ram_cache(void) { RAMBlock *block; WITH_RCU_READ_LOCK_GUARD() { RAMBLOCK_FOREACH_NOT_IGNORED(block) { block->colo_cache = qemu_anon_ram_alloc(block->used_length, NULL, false, false); if (!block->colo_cache) { error_report("%s: Can't alloc memory for COLO cache of block %s," "size 0x" RAM_ADDR_FMT, __func__, block->idstr, block->used_length); RAMBLOCK_FOREACH_NOT_IGNORED(block) { if (block->colo_cache) { qemu_anon_ram_free(block->colo_cache, block->used_length); block->colo_cache = NULL; } } return -errno; } if (!machine_dump_guest_core(current_machine)) { qemu_madvise(block->colo_cache, block->used_length, QEMU_MADV_DONTDUMP); } } } /* * Record the dirty pages that sent by PVM, we use this dirty bitmap together * with to decide which page in cache should be flushed into SVM's RAM. Here * we use the same name 'ram_bitmap' as for migration. */ if (ram_bytes_total()) { RAMBLOCK_FOREACH_NOT_IGNORED(block) { unsigned long pages = block->max_length >> TARGET_PAGE_BITS; block->bmap = bitmap_new(pages); } } colo_init_ram_state(); return 0; } /* TODO: duplicated with ram_init_bitmaps */ void colo_incoming_start_dirty_log(void) { RAMBlock *block = NULL; /* For memory_global_dirty_log_start below. */ qemu_mutex_lock_iothread(); qemu_mutex_lock_ramlist(); memory_global_dirty_log_sync(false); WITH_RCU_READ_LOCK_GUARD() { RAMBLOCK_FOREACH_NOT_IGNORED(block) { ramblock_sync_dirty_bitmap(ram_state, block); /* Discard this dirty bitmap record */ bitmap_zero(block->bmap, block->max_length >> TARGET_PAGE_BITS); } memory_global_dirty_log_start(GLOBAL_DIRTY_MIGRATION); } ram_state->migration_dirty_pages = 0; qemu_mutex_unlock_ramlist(); qemu_mutex_unlock_iothread(); } /* It is need to hold the global lock to call this helper */ void colo_release_ram_cache(void) { RAMBlock *block; memory_global_dirty_log_stop(GLOBAL_DIRTY_MIGRATION); RAMBLOCK_FOREACH_NOT_IGNORED(block) { g_free(block->bmap); block->bmap = NULL; } WITH_RCU_READ_LOCK_GUARD() { RAMBLOCK_FOREACH_NOT_IGNORED(block) { if (block->colo_cache) { qemu_anon_ram_free(block->colo_cache, block->used_length); block->colo_cache = NULL; } } } ram_state_cleanup(&ram_state); } /** * ram_load_setup: Setup RAM for migration incoming side * * Returns zero to indicate success and negative for error * * @f: QEMUFile where to receive the data * @opaque: RAMState pointer */ static int ram_load_setup(QEMUFile *f, void *opaque) { xbzrle_load_setup(); ramblock_recv_map_init(); return 0; } static int ram_load_cleanup(void *opaque) { RAMBlock *rb; RAMBLOCK_FOREACH_NOT_IGNORED(rb) { qemu_ram_block_writeback(rb); } xbzrle_load_cleanup(); RAMBLOCK_FOREACH_NOT_IGNORED(rb) { g_free(rb->receivedmap); rb->receivedmap = NULL; } return 0; } /** * ram_postcopy_incoming_init: allocate postcopy data structures * * Returns 0 for success and negative if there was one error * * @mis: current migration incoming state * * 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) { return postcopy_ram_incoming_init(mis); } /** * ram_load_postcopy: load a page in postcopy case * * Returns 0 for success or -errno in case of error * * Called in postcopy mode by ram_load(). * rcu_read_lock is taken prior to this being called. * * @f: QEMUFile where to send the data * @channel: the channel to use for loading */ int ram_load_postcopy(QEMUFile *f, int channel) { int flags = 0, ret = 0; bool place_needed = false; bool matches_target_page_size = false; MigrationIncomingState *mis = migration_incoming_get_current(); PostcopyTmpPage *tmp_page = &mis->postcopy_tmp_pages[channel]; while (!ret && !(flags & RAM_SAVE_FLAG_EOS)) { ram_addr_t addr; void *page_buffer = NULL; void *place_source = NULL; RAMBlock *block = NULL; uint8_t ch; int len; addr = qemu_get_be64(f); /* * If qemu file error, we should stop here, and then "addr" * may be invalid */ ret = qemu_file_get_error(f); if (ret) { break; } flags = addr & ~TARGET_PAGE_MASK; addr &= TARGET_PAGE_MASK; trace_ram_load_postcopy_loop(channel, (uint64_t)addr, flags); if (flags & (RAM_SAVE_FLAG_ZERO | RAM_SAVE_FLAG_PAGE | RAM_SAVE_FLAG_COMPRESS_PAGE)) { block = ram_block_from_stream(mis, f, flags, channel); if (!block) { ret = -EINVAL; break; } /* * Relying on used_length is racy and can result in false positives. * We might place pages beyond used_length in case RAM was shrunk * while in postcopy, which is fine - trying to place via * UFFDIO_COPY/UFFDIO_ZEROPAGE will never segfault. */ if (!block->host || addr >= block->postcopy_length) { error_report("Illegal RAM offset " RAM_ADDR_FMT, addr); ret = -EINVAL; break; } tmp_page->target_pages++; matches_target_page_size = block->page_size == TARGET_PAGE_SIZE; /* * Postcopy requires that we place whole host pages atomically; * these may be huge pages for RAMBlocks that are backed by * hugetlbfs. * 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 one chunk. */ page_buffer = tmp_page->tmp_huge_page + host_page_offset_from_ram_block_offset(block, addr); /* If all TP are zero then we can optimise the place */ if (tmp_page->target_pages == 1) { tmp_page->host_addr = host_page_from_ram_block_offset(block, addr); } else if (tmp_page->host_addr != host_page_from_ram_block_offset(block, addr)) { /* not the 1st TP within the HP */ error_report("Non-same host page detected on channel %d: " "Target host page %p, received host page %p " "(rb %s offset 0x"RAM_ADDR_FMT" target_pages %d)", channel, tmp_page->host_addr, host_page_from_ram_block_offset(block, addr), block->idstr, addr, tmp_page->target_pages); ret = -EINVAL; break; } /* * If it's the last part of a host page then we place the host * page */ if (tmp_page->target_pages == (block->page_size / TARGET_PAGE_SIZE)) { place_needed = true; } place_source = tmp_page->tmp_huge_page; } switch (flags & ~RAM_SAVE_FLAG_CONTINUE) { case RAM_SAVE_FLAG_ZERO: ch = qemu_get_byte(f); /* * Can skip to set page_buffer when * this is a zero page and (block->page_size == TARGET_PAGE_SIZE). */ if (ch || !matches_target_page_size) { memset(page_buffer, ch, TARGET_PAGE_SIZE); } if (ch) { tmp_page->all_zero = false; } break; case RAM_SAVE_FLAG_PAGE: tmp_page->all_zero = false; if (!matches_target_page_size) { /* For huge pages, we always use temporary buffer */ qemu_get_buffer(f, page_buffer, TARGET_PAGE_SIZE); } else { /* * For small pages that matches target page size, we * avoid the qemu_file copy. Instead we directly use * the buffer of QEMUFile to place the page. Note: we * cannot do any QEMUFile operation before using that * buffer to make sure the buffer is valid when * placing the page. */ qemu_get_buffer_in_place(f, (uint8_t **)&place_source, TARGET_PAGE_SIZE); } break; case RAM_SAVE_FLAG_COMPRESS_PAGE: tmp_page->all_zero = false; 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, page_buffer, len); break; case RAM_SAVE_FLAG_MULTIFD_FLUSH: multifd_recv_sync_main(); break; case RAM_SAVE_FLAG_EOS: /* normal exit */ if (migrate_multifd() && migrate_multifd_flush_after_each_section()) { multifd_recv_sync_main(); } break; default: error_report("Unknown combination of migration flags: 0x%x" " (postcopy mode)", flags); ret = -EINVAL; break; } /* Got the whole host page, wait for decompress before placing. */ if (place_needed) { ret |= wait_for_decompress_done(); } /* Detect for any possible file errors */ if (!ret && qemu_file_get_error(f)) { ret = qemu_file_get_error(f); } if (!ret && place_needed) { if (tmp_page->all_zero) { ret = postcopy_place_page_zero(mis, tmp_page->host_addr, block); } else { ret = postcopy_place_page(mis, tmp_page->host_addr, place_source, block); } place_needed = false; postcopy_temp_page_reset(tmp_page); } } return ret; } static bool postcopy_is_running(void) { PostcopyState ps = postcopy_state_get(); return ps >= POSTCOPY_INCOMING_LISTENING && ps < POSTCOPY_INCOMING_END; } /* * Flush content of RAM cache into SVM's memory. * Only flush the pages that be dirtied by PVM or SVM or both. */ void colo_flush_ram_cache(void) { RAMBlock *block = NULL; void *dst_host; void *src_host; unsigned long offset = 0; memory_global_dirty_log_sync(false); qemu_mutex_lock(&ram_state->bitmap_mutex); WITH_RCU_READ_LOCK_GUARD() { RAMBLOCK_FOREACH_NOT_IGNORED(block) { ramblock_sync_dirty_bitmap(ram_state, block); } } trace_colo_flush_ram_cache_begin(ram_state->migration_dirty_pages); WITH_RCU_READ_LOCK_GUARD() { block = QLIST_FIRST_RCU(&ram_list.blocks); while (block) { unsigned long num = 0; offset = colo_bitmap_find_dirty(ram_state, block, offset, &num); if (!offset_in_ramblock(block, ((ram_addr_t)offset) << TARGET_PAGE_BITS)) { offset = 0; num = 0; block = QLIST_NEXT_RCU(block, next); } else { unsigned long i = 0; for (i = 0; i < num; i++) { migration_bitmap_clear_dirty(ram_state, block, offset + i); } dst_host = block->host + (((ram_addr_t)offset) << TARGET_PAGE_BITS); src_host = block->colo_cache + (((ram_addr_t)offset) << TARGET_PAGE_BITS); memcpy(dst_host, src_host, TARGET_PAGE_SIZE * num); offset += num; } } } qemu_mutex_unlock(&ram_state->bitmap_mutex); trace_colo_flush_ram_cache_end(); } static int parse_ramblock(QEMUFile *f, RAMBlock *block, ram_addr_t length) { int ret = 0; /* ADVISE is earlier, it shows the source has the postcopy capability on */ bool postcopy_advised = migration_incoming_postcopy_advised(); assert(block); if (!qemu_ram_is_migratable(block)) { error_report("block %s should not be migrated !", block->idstr); return -EINVAL; } 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); } } /* For postcopy we need to check hugepage sizes match */ if (postcopy_advised && migrate_postcopy_ram() && block->page_size != qemu_host_page_size) { uint64_t remote_page_size = qemu_get_be64(f); if (remote_page_size != block->page_size) { error_report("Mismatched RAM page size %s " "(local) %zd != %" PRId64, block->idstr, block->page_size, remote_page_size); ret = -EINVAL; } } if (migrate_ignore_shared()) { hwaddr addr = qemu_get_be64(f); if (migrate_ram_is_ignored(block) && block->mr->addr != addr) { error_report("Mismatched GPAs for block %s " "%" PRId64 "!= %" PRId64, block->idstr, (uint64_t)addr, (uint64_t)block->mr->addr); ret = -EINVAL; } } ret = rdma_block_notification_handle(f, block->idstr); if (ret < 0) { qemu_file_set_error(f, ret); } return ret; } static int parse_ramblocks(QEMUFile *f, ram_addr_t total_ram_bytes) { int ret = 0; /* Synchronize RAM block list */ while (!ret && total_ram_bytes) { RAMBlock *block; char id[256]; ram_addr_t length; int 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) { ret = parse_ramblock(f, block, length); } else { error_report("Unknown ramblock \"%s\", cannot accept " "migration", id); ret = -EINVAL; } total_ram_bytes -= length; } return ret; } /** * ram_load_precopy: load pages in precopy case * * Returns 0 for success or -errno in case of error * * Called in precopy mode by ram_load(). * rcu_read_lock is taken prior to this being called. * * @f: QEMUFile where to send the data */ static int ram_load_precopy(QEMUFile *f) { MigrationIncomingState *mis = migration_incoming_get_current(); int flags = 0, ret = 0, invalid_flags = 0, len = 0, i = 0; if (!migrate_compress()) { invalid_flags |= RAM_SAVE_FLAG_COMPRESS_PAGE; } while (!ret && !(flags & RAM_SAVE_FLAG_EOS)) { ram_addr_t addr; void *host = NULL, *host_bak = NULL; uint8_t ch; /* * Yield periodically to let main loop run, but an iteration of * the main loop is expensive, so do it each some iterations */ if ((i & 32767) == 0 && qemu_in_coroutine()) { aio_co_schedule(qemu_get_current_aio_context(), qemu_coroutine_self()); qemu_coroutine_yield(); } i++; addr = qemu_get_be64(f); flags = addr & ~TARGET_PAGE_MASK; addr &= TARGET_PAGE_MASK; if (flags & invalid_flags) { if (flags & invalid_flags & RAM_SAVE_FLAG_COMPRESS_PAGE) { error_report("Received an unexpected compressed page"); } ret = -EINVAL; break; } if (flags & (RAM_SAVE_FLAG_ZERO | RAM_SAVE_FLAG_PAGE | RAM_SAVE_FLAG_COMPRESS_PAGE | RAM_SAVE_FLAG_XBZRLE)) { RAMBlock *block = ram_block_from_stream(mis, f, flags, RAM_CHANNEL_PRECOPY); host = host_from_ram_block_offset(block, addr); /* * After going into COLO stage, we should not load the page * into SVM's memory directly, we put them into colo_cache firstly. * NOTE: We need to keep a copy of SVM's ram in colo_cache. * Previously, we copied all these memory in preparing stage of COLO * while we need to stop VM, which is a time-consuming process. * Here we optimize it by a trick, back-up every page while in * migration process while COLO is enabled, though it affects the * speed of the migration, but it obviously reduce the downtime of * back-up all SVM'S memory in COLO preparing stage. */ if (migration_incoming_colo_enabled()) { if (migration_incoming_in_colo_state()) { /* In COLO stage, put all pages into cache temporarily */ host = colo_cache_from_block_offset(block, addr, true); } else { /* * In migration stage but before COLO stage, * Put all pages into both cache and SVM's memory. */ host_bak = colo_cache_from_block_offset(block, addr, false); } } if (!host) { error_report("Illegal RAM offset " RAM_ADDR_FMT, addr); ret = -EINVAL; break; } if (!migration_incoming_in_colo_state()) { ramblock_recv_bitmap_set(block, host); } trace_ram_load_loop(block->idstr, (uint64_t)addr, flags, host); } switch (flags & ~RAM_SAVE_FLAG_CONTINUE) { case RAM_SAVE_FLAG_MEM_SIZE: ret = parse_ramblocks(f, addr); break; case RAM_SAVE_FLAG_ZERO: 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_MULTIFD_FLUSH: multifd_recv_sync_main(); break; case RAM_SAVE_FLAG_EOS: /* normal exit */ if (migrate_multifd() && migrate_multifd_flush_after_each_section()) { multifd_recv_sync_main(); } break; case RAM_SAVE_FLAG_HOOK: ret = rdma_registration_handle(f); if (ret < 0) { qemu_file_set_error(f, ret); } break; default: error_report("Unknown combination of migration flags: 0x%x", flags); ret = -EINVAL; } if (!ret) { ret = qemu_file_get_error(f); } if (!ret && host_bak) { memcpy(host_bak, host, TARGET_PAGE_SIZE); } } ret |= wait_for_decompress_done(); return ret; } static int ram_load(QEMUFile *f, void *opaque, int version_id) { int ret = 0; static uint64_t seq_iter; /* * If system is running in postcopy mode, page inserts to host memory must * be atomic */ bool postcopy_running = postcopy_is_running(); seq_iter++; if (version_id != 4) { return -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. */ WITH_RCU_READ_LOCK_GUARD() { if (postcopy_running) { /* * Note! Here RAM_CHANNEL_PRECOPY is the precopy channel of * postcopy migration, we have another RAM_CHANNEL_POSTCOPY to * service fast page faults. */ ret = ram_load_postcopy(f, RAM_CHANNEL_PRECOPY); } else { ret = ram_load_precopy(f); } } trace_ram_load_complete(ret, seq_iter); return ret; } static bool ram_has_postcopy(void *opaque) { RAMBlock *rb; RAMBLOCK_FOREACH_NOT_IGNORED(rb) { if (ramblock_is_pmem(rb)) { info_report("Block: %s, host: %p is a nvdimm memory, postcopy" "is not supported now!", rb->idstr, rb->host); return false; } } return migrate_postcopy_ram(); } /* Sync all the dirty bitmap with destination VM. */ static int ram_dirty_bitmap_sync_all(MigrationState *s, RAMState *rs) { RAMBlock *block; QEMUFile *file = s->to_dst_file; trace_ram_dirty_bitmap_sync_start(); qatomic_set(&rs->postcopy_bmap_sync_requested, 0); RAMBLOCK_FOREACH_NOT_IGNORED(block) { qemu_savevm_send_recv_bitmap(file, block->idstr); trace_ram_dirty_bitmap_request(block->idstr); qatomic_inc(&rs->postcopy_bmap_sync_requested); } trace_ram_dirty_bitmap_sync_wait(); /* Wait until all the ramblocks' dirty bitmap synced */ while (qatomic_read(&rs->postcopy_bmap_sync_requested)) { migration_rp_wait(s); } trace_ram_dirty_bitmap_sync_complete(); return 0; } /* * Read the received bitmap, revert it as the initial dirty bitmap. * This is only used when the postcopy migration is paused but wants * to resume from a middle point. */ int ram_dirty_bitmap_reload(MigrationState *s, RAMBlock *block) { int ret = -EINVAL; /* from_dst_file is always valid because we're within rp_thread */ QEMUFile *file = s->rp_state.from_dst_file; g_autofree unsigned long *le_bitmap = NULL; unsigned long nbits = block->used_length >> TARGET_PAGE_BITS; uint64_t local_size = DIV_ROUND_UP(nbits, 8); uint64_t size, end_mark; RAMState *rs = ram_state; trace_ram_dirty_bitmap_reload_begin(block->idstr); if (s->state != MIGRATION_STATUS_POSTCOPY_RECOVER) { error_report("%s: incorrect state %s", __func__, MigrationStatus_str(s->state)); return -EINVAL; } /* * Note: see comments in ramblock_recv_bitmap_send() on why we * need the endianness conversion, and the paddings. */ local_size = ROUND_UP(local_size, 8); /* Add paddings */ le_bitmap = bitmap_new(nbits + BITS_PER_LONG); size = qemu_get_be64(file); /* The size of the bitmap should match with our ramblock */ if (size != local_size) { error_report("%s: ramblock '%s' bitmap size mismatch " "(0x%"PRIx64" != 0x%"PRIx64")", __func__, block->idstr, size, local_size); return -EINVAL; } size = qemu_get_buffer(file, (uint8_t *)le_bitmap, local_size); end_mark = qemu_get_be64(file); ret = qemu_file_get_error(file); if (ret || size != local_size) { error_report("%s: read bitmap failed for ramblock '%s': %d" " (size 0x%"PRIx64", got: 0x%"PRIx64")", __func__, block->idstr, ret, local_size, size); return -EIO; } if (end_mark != RAMBLOCK_RECV_BITMAP_ENDING) { error_report("%s: ramblock '%s' end mark incorrect: 0x%"PRIx64, __func__, block->idstr, end_mark); return -EINVAL; } /* * Endianness conversion. We are during postcopy (though paused). * The dirty bitmap won't change. We can directly modify it. */ bitmap_from_le(block->bmap, le_bitmap, nbits); /* * What we received is "received bitmap". Revert it as the initial * dirty bitmap for this ramblock. */ bitmap_complement(block->bmap, block->bmap, nbits); /* Clear dirty bits of discarded ranges that we don't want to migrate. */ ramblock_dirty_bitmap_clear_discarded_pages(block); /* We'll recalculate migration_dirty_pages in ram_state_resume_prepare(). */ trace_ram_dirty_bitmap_reload_complete(block->idstr); qatomic_dec(&rs->postcopy_bmap_sync_requested); /* * We succeeded to sync bitmap for current ramblock. Always kick the * migration thread to check whether all requested bitmaps are * reloaded. NOTE: it's racy to only kick when requested==0, because * we don't know whether the migration thread may still be increasing * it. */ migration_rp_kick(s); return 0; } static int ram_resume_prepare(MigrationState *s, void *opaque) { RAMState *rs = *(RAMState **)opaque; int ret; ret = ram_dirty_bitmap_sync_all(s, rs); if (ret) { return ret; } ram_state_resume_prepare(rs, s->to_dst_file); return 0; } void postcopy_preempt_shutdown_file(MigrationState *s) { qemu_put_be64(s->postcopy_qemufile_src, RAM_SAVE_FLAG_EOS); qemu_fflush(s->postcopy_qemufile_src); } static SaveVMHandlers savevm_ram_handlers = { .save_setup = ram_save_setup, .save_live_iterate = ram_save_iterate, .save_live_complete_postcopy = ram_save_complete, .save_live_complete_precopy = ram_save_complete, .has_postcopy = ram_has_postcopy, .state_pending_exact = ram_state_pending_exact, .state_pending_estimate = ram_state_pending_estimate, .load_state = ram_load, .save_cleanup = ram_save_cleanup, .load_setup = ram_load_setup, .load_cleanup = ram_load_cleanup, .resume_prepare = ram_resume_prepare, }; static void ram_mig_ram_block_resized(RAMBlockNotifier *n, void *host, size_t old_size, size_t new_size) { PostcopyState ps = postcopy_state_get(); ram_addr_t offset; RAMBlock *rb = qemu_ram_block_from_host(host, false, &offset); Error *err = NULL; if (!rb) { error_report("RAM block not found"); return; } if (migrate_ram_is_ignored(rb)) { return; } if (!migration_is_idle()) { /* * Precopy code on the source cannot deal with the size of RAM blocks * changing at random points in time - especially after sending the * RAM block sizes in the migration stream, they must no longer change. * Abort and indicate a proper reason. */ error_setg(&err, "RAM block '%s' resized during precopy.", rb->idstr); migration_cancel(err); error_free(err); } switch (ps) { case POSTCOPY_INCOMING_ADVISE: /* * Update what ram_postcopy_incoming_init()->init_range() does at the * time postcopy was advised. Syncing RAM blocks with the source will * result in RAM resizes. */ if (old_size < new_size) { if (ram_discard_range(rb->idstr, old_size, new_size - old_size)) { error_report("RAM block '%s' discard of resized RAM failed", rb->idstr); } } rb->postcopy_length = new_size; break; case POSTCOPY_INCOMING_NONE: case POSTCOPY_INCOMING_RUNNING: case POSTCOPY_INCOMING_END: /* * Once our guest is running, postcopy does no longer care about * resizes. When growing, the new memory was not available on the * source, no handler needed. */ break; default: error_report("RAM block '%s' resized during postcopy state: %d", rb->idstr, ps); exit(-1); } } static RAMBlockNotifier ram_mig_ram_notifier = { .ram_block_resized = ram_mig_ram_block_resized, }; void ram_mig_init(void) { qemu_mutex_init(&XBZRLE.lock); register_savevm_live("ram", 0, 4, &savevm_ram_handlers, &ram_state); ram_block_notifier_add(&ram_mig_ram_notifier); }