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* QEMU live migration
* Copyright IBM, Corp. 2008
* Authors:
* Anthony Liguori <>
* This work is licensed under the terms of the GNU GPL, version 2. See
* the COPYING file in the top-level directory.
#include "exec/cpu-common.h"
#include "hw/qdev-core.h"
#include "qapi/qapi-types-migration.h"
#include "qemu/thread.h"
#include "qemu/coroutine_int.h"
#include "io/channel.h"
#include "io/channel-buffer.h"
#include "net/announce.h"
#include "qom/object.h"
#include "postcopy-ram.h"
struct PostcopyBlocktimeContext;
* 1<<6=64 pages -> 256K chunk when page size is 4K. This gives us
* the benefit that all the chunks are 64 pages aligned then the
* bitmaps are always aligned to LONG.
* 1<<18=256K pages -> 1G chunk when page size is 4K. This is the
* default value to use if no one specified.
* 1<<31=2G pages -> 8T chunk when page size is 4K. This should be
* big enough and make sure we won't overflow easily.
/* This is an abstraction of a "temp huge page" for postcopy's purpose */
typedef struct {
* This points to a temporary huge page as a buffer for UFFDIO_COPY. It's
* mmap()ed and needs to be freed when cleanup.
void *tmp_huge_page;
* This points to the host page we're going to install for this temp page.
* It tells us after we've received the whole page, where we should put it.
void *host_addr;
/* Number of small pages copied (in size of TARGET_PAGE_SIZE) */
unsigned int target_pages;
/* Whether this page contains all zeros */
bool all_zero;
} PostcopyTmpPage;
/* State for the incoming migration */
struct MigrationIncomingState {
QEMUFile *from_src_file;
/* Previously received RAM's RAMBlock pointer */
RAMBlock *last_recv_block[RAM_CHANNEL_MAX];
/* A hook to allow cleanup at the end of incoming migration */
void *transport_data;
void (*transport_cleanup)(void *data);
* Used to sync thread creations. Note that we can't create threads in
* parallel with this sem.
QemuSemaphore thread_sync_sem;
* Free at the start of the main state load, set as the main thread finishes
* loading state.
QemuEvent main_thread_load_event;
/* For network announces */
AnnounceTimer announce_timer;
size_t largest_page_size;
bool have_fault_thread;
QemuThread fault_thread;
/* Set this when we want the fault thread to quit */
bool fault_thread_quit;
bool have_listen_thread;
QemuThread listen_thread;
/* For the kernel to send us notifications */
int userfault_fd;
/* To notify the fault_thread to wake, e.g., when need to quit */
int userfault_event_fd;
QEMUFile *to_src_file;
QemuMutex rp_mutex; /* We send replies from multiple threads */
/* RAMBlock of last request sent to source */
RAMBlock *last_rb;
* Number of postcopy channels including the default precopy channel, so
* vanilla postcopy will only contain one channel which contain both
* precopy and postcopy streams.
* This is calculated when the src requests to enable postcopy but before
* it starts. Its value can depend on e.g. whether postcopy preemption is
* enabled.
unsigned int postcopy_channels;
/* QEMUFile for postcopy only; it'll be handled by a separate thread */
QEMUFile *postcopy_qemufile_dst;
/* Postcopy priority thread is used to receive postcopy requested pages */
QemuThread postcopy_prio_thread;
bool postcopy_prio_thread_created;
* Used to sync between the ram load main thread and the fast ram load
* thread. It protects postcopy_qemufile_dst, which is the postcopy
* fast channel.
* The ram fast load thread will take it mostly for the whole lifecycle
* because it needs to continuously read data from the channel, and
* it'll only release this mutex if postcopy is interrupted, so that
* the ram load main thread will take this mutex over and properly
* release the broken channel.
QemuMutex postcopy_prio_thread_mutex;
* An array of temp host huge pages to be used, one for each postcopy
* channel.
PostcopyTmpPage *postcopy_tmp_pages;
/* This is shared for all postcopy channels */
void *postcopy_tmp_zero_page;
/* PostCopyFD's for external userfaultfds & handlers of shared memory */
GArray *postcopy_remote_fds;
int state;
bool have_colo_incoming_thread;
QemuThread colo_incoming_thread;
/* The coroutine we should enter (back) after failover */
Coroutine *migration_incoming_co;
QemuSemaphore colo_incoming_sem;
* PostcopyBlocktimeContext to keep information for postcopy
* live migration, to calculate vCPU block time
* */
struct PostcopyBlocktimeContext *blocktime_ctx;
/* notify PAUSED postcopy incoming migrations to try to continue */
QemuSemaphore postcopy_pause_sem_dst;
QemuSemaphore postcopy_pause_sem_fault;
* This semaphore is used to allow the ram fast load thread (only when
* postcopy preempt is enabled) fall into sleep when there's network
* interruption detected. When the recovery is done, the main load
* thread will kick the fast ram load thread using this semaphore.
QemuSemaphore postcopy_pause_sem_fast_load;
/* List of listening socket addresses */
SocketAddressList *socket_address_list;
/* A tree of pages that we requested to the source VM */
GTree *page_requested;
/* For debugging purpose only, but would be nice to keep */
int page_requested_count;
* The mutex helps to maintain the requested pages that we sent to the
* source, IOW, to guarantee coherent between the page_requests tree and
* the per-ramblock receivedmap. Note! This does not guarantee consistency
* of the real page copy procedures (using UFFDIO_[ZERO]COPY). E.g., even
* if one bit in receivedmap is cleared, UFFDIO_COPY could have happened
* for that page already. This is intended so that the mutex won't
* serialize and blocked by slow operations like UFFDIO_* ioctls. However
* this should be enough to make sure the page_requested tree always
* contains valid information.
QemuMutex page_request_mutex;
MigrationIncomingState *migration_incoming_get_current(void);
void migration_incoming_state_destroy(void);
void migration_incoming_transport_cleanup(MigrationIncomingState *mis);
* Functions to work with blocktime context
void fill_destination_postcopy_migration_info(MigrationInfo *info);
#define TYPE_MIGRATION "migration"
typedef struct MigrationClass MigrationClass;
DECLARE_OBJ_CHECKERS(MigrationState, MigrationClass,
struct MigrationClass {
/*< private >*/
DeviceClass parent_class;
struct MigrationState {
/*< private >*/
DeviceState parent_obj;
/*< public >*/
QemuThread thread;
QEMUBH *vm_start_bh;
QEMUBH *cleanup_bh;
/* Protected by qemu_file_lock */
QEMUFile *to_dst_file;
/* Postcopy specific transfer channel */
QEMUFile *postcopy_qemufile_src;
* It is posted when the preempt channel is established. Note: this is
* used for both the start or recover of a postcopy migration. We'll
* post to this sem every time a new preempt channel is created in the
* main thread, and we keep post() and wait() in pair.
QemuSemaphore postcopy_qemufile_src_sem;
QIOChannelBuffer *bioc;
* Protects to_dst_file/from_dst_file pointers. We need to make sure we
* won't yield or hang during the critical section, since this lock will be
* used in OOB command handler.
QemuMutex qemu_file_lock;
* Used to allow urgent requests to override rate limiting.
QemuSemaphore rate_limit_sem;
/* pages already send at the beginning of current iteration */
uint64_t iteration_initial_pages;
/* pages transferred per second */
double pages_per_second;
/* bytes already send at the beginning of current iteration */
uint64_t iteration_initial_bytes;
/* time at the start of current iteration */
int64_t iteration_start_time;
* The final stage happens when the remaining data is smaller than
* this threshold; it's calculated from the requested downtime and
* measured bandwidth
int64_t threshold_size;
/* params from 'migrate-set-parameters' */
MigrationParameters parameters;
int state;
/* State related to return path */
struct {
/* Protected by qemu_file_lock */
QEMUFile *from_dst_file;
QemuThread rp_thread;
bool error;
* We can also check non-zero of rp_thread, but there's no "official"
* way to do this, so this bool makes it slightly more elegant.
* Checking from_dst_file for this is racy because from_dst_file will
* be cleared in the rp_thread!
bool rp_thread_created;
QemuSemaphore rp_sem;
} rp_state;
double mbps;
/* Timestamp when recent migration starts (ms) */
int64_t start_time;
/* Total time used by latest migration (ms) */
int64_t total_time;
/* Timestamp when VM is down (ms) to migrate the last stuff */
int64_t downtime_start;
int64_t downtime;
int64_t expected_downtime;
bool enabled_capabilities[MIGRATION_CAPABILITY__MAX];
int64_t setup_time;
* Whether guest was running when we enter the completion stage.
* If migration is interrupted by any reason, we need to continue
* running the guest on source.
bool vm_was_running;
/* Flag set once the migration has been asked to enter postcopy */
bool start_postcopy;
/* Flag set after postcopy has sent the device state */
bool postcopy_after_devices;
/* Flag set once the migration thread is running (and needs joining) */
bool migration_thread_running;
/* Flag set once the migration thread called bdrv_inactivate_all */
bool block_inactive;
/* Migration is waiting for guest to unplug device */
QemuSemaphore wait_unplug_sem;
/* Migration is paused due to pause-before-switchover */
QemuSemaphore pause_sem;
/* The semaphore is used to notify COLO thread that failover is finished */
QemuSemaphore colo_exit_sem;
/* The event is used to notify COLO thread to do checkpoint */
QemuEvent colo_checkpoint_event;
int64_t colo_checkpoint_time;
QEMUTimer *colo_delay_timer;
/* The first error that has occurred.
We used the mutex to be able to return the 1st error message */
Error *error;
/* mutex to protect errp */
QemuMutex error_mutex;
/* Do we have to clean up -b/-i from old migrate parameters */
/* This feature is deprecated and will be removed */
bool must_remove_block_options;
* Global switch on whether we need to store the global state
* during migration.
bool store_global_state;
/* Whether we send QEMU_VM_CONFIGURATION during migration */
bool send_configuration;
/* Whether we send section footer during migration */
bool send_section_footer;
* Whether we allow break sending huge pages when postcopy preempt is
* enabled. When disabled, we won't interrupt precopy within sending a
* host huge page, which is the old behavior of vanilla postcopy.
* NOTE: this parameter is ignored if postcopy preempt is not enabled.
bool postcopy_preempt_break_huge;
/* Needed by postcopy-pause state */
QemuSemaphore postcopy_pause_sem;
QemuSemaphore postcopy_pause_rp_sem;
* Whether we abort the migration if decompression errors are
* detected at the destination. It is left at false for qemu
* older than 3.0, since only newer qemu sends streams that
* do not trigger spurious decompression errors.
bool decompress_error_check;
* This decides the size of guest memory chunk that will be used
* to track dirty bitmap clearing. The size of memory chunk will
* be GUEST_PAGE_SIZE << N. Say, N=0 means we will clear dirty
* bitmap for each page to send (1<<0=1); N=10 means we will clear
* dirty bitmap only once for 1<<10=1K continuous guest pages
* (which is in 4M chunk).
uint8_t clear_bitmap_shift;
* This save hostname when out-going migration starts
char *hostname;
void migrate_set_state(int *state, int old_state, int new_state);
void migration_fd_process_incoming(QEMUFile *f, Error **errp);
void migration_ioc_process_incoming(QIOChannel *ioc, Error **errp);
void migration_incoming_process(void);
bool migration_has_all_channels(void);
uint64_t migrate_max_downtime(void);
void migrate_set_error(MigrationState *s, const Error *error);
void migrate_fd_error(MigrationState *s, const Error *error);
void migrate_fd_connect(MigrationState *s, Error *error_in);
bool migration_is_setup_or_active(int state);
bool migration_is_running(int state);
void migrate_init(MigrationState *s);
bool migration_is_blocked(Error **errp);
/* True if outgoing migration has entered postcopy phase */
bool migration_in_postcopy(void);
MigrationState *migrate_get_current(void);
bool migrate_postcopy(void);
bool migrate_release_ram(void);
bool migrate_postcopy_ram(void);
bool migrate_zero_blocks(void);
bool migrate_dirty_bitmaps(void);
bool migrate_ignore_shared(void);
bool migrate_validate_uuid(void);
bool migrate_auto_converge(void);
bool migrate_use_multifd(void);
bool migrate_pause_before_switchover(void);
int migrate_multifd_channels(void);
MultiFDCompression migrate_multifd_compression(void);
int migrate_multifd_zlib_level(void);
int migrate_multifd_zstd_level(void);
bool migrate_use_zero_copy_send(void);
#define migrate_use_zero_copy_send() (false)
int migrate_use_tls(void);
int migrate_use_xbzrle(void);
uint64_t migrate_xbzrle_cache_size(void);
bool migrate_colo_enabled(void);
bool migrate_use_block(void);
bool migrate_use_block_incremental(void);
int migrate_max_cpu_throttle(void);
bool migrate_use_return_path(void);
uint64_t ram_get_total_transferred_pages(void);
bool migrate_use_compression(void);
int migrate_compress_level(void);
int migrate_compress_threads(void);
int migrate_compress_wait_thread(void);
int migrate_decompress_threads(void);
bool migrate_use_events(void);
bool migrate_postcopy_blocktime(void);
bool migrate_background_snapshot(void);
bool migrate_postcopy_preempt(void);
/* Sending on the return path - generic and then for each message type */
void migrate_send_rp_shut(MigrationIncomingState *mis,
uint32_t value);
void migrate_send_rp_pong(MigrationIncomingState *mis,
uint32_t value);
int migrate_send_rp_req_pages(MigrationIncomingState *mis, RAMBlock *rb,
ram_addr_t start, uint64_t haddr);
int migrate_send_rp_message_req_pages(MigrationIncomingState *mis,
RAMBlock *rb, ram_addr_t start);
void migrate_send_rp_recv_bitmap(MigrationIncomingState *mis,
char *block_name);
void migrate_send_rp_resume_ack(MigrationIncomingState *mis, uint32_t value);
void dirty_bitmap_mig_before_vm_start(void);
void dirty_bitmap_mig_cancel_outgoing(void);
void dirty_bitmap_mig_cancel_incoming(void);
bool check_dirty_bitmap_mig_alias_map(const BitmapMigrationNodeAliasList *bbm,
Error **errp);
void migrate_add_address(SocketAddress *address);
int foreach_not_ignored_block(RAMBlockIterFunc func, void *opaque);
#define qemu_ram_foreach_block \
#warning "Use foreach_not_ignored_block in migration code"
void migration_make_urgent_request(void);
void migration_consume_urgent_request(void);
bool migration_rate_limit(void);
void migration_cancel(const Error *error);
void populate_vfio_info(MigrationInfo *info);
void postcopy_temp_page_reset(PostcopyTmpPage *tmp_page);
bool migrate_multi_channels_is_allowed(void);
void migrate_protocol_allow_multi_channels(bool allow);