diff options
| -rw-r--r-- | migration/migration.c | 255 | ||||
| -rw-r--r-- | migration/migration.h | 3 | ||||
| -rw-r--r-- | migration/savevm.c | 1 | ||||
| -rw-r--r-- | migration/savevm.h | 2 |
4 files changed, 258 insertions, 3 deletions
diff --git a/migration/migration.c b/migration/migration.c index 2262f348af..ecb4115d68 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -2000,6 +2000,7 @@ void migrate_init(MigrationState *s) * locks. */ s->cleanup_bh = 0; + s->vm_start_bh = 0; s->to_dst_file = NULL; s->state = MIGRATION_STATUS_NONE; s->rp_state.from_dst_file = NULL; @@ -3217,6 +3218,50 @@ fail: MIGRATION_STATUS_FAILED); } +/** + * bg_migration_completion: Used by bg_migration_thread when after all the + * RAM has been saved. The caller 'breaks' the loop when this returns. + * + * @s: Current migration state + */ +static void bg_migration_completion(MigrationState *s) +{ + int current_active_state = s->state; + + /* + * Stop tracking RAM writes - un-protect memory, un-register UFFD + * memory ranges, flush kernel wait queues and wake up threads + * waiting for write fault to be resolved. + */ + ram_write_tracking_stop(); + + if (s->state == MIGRATION_STATUS_ACTIVE) { + /* + * By this moment we have RAM content saved into the migration stream. + * The next step is to flush the non-RAM content (device state) + * right after the ram content. The device state has been stored into + * the temporary buffer before RAM saving started. + */ + qemu_put_buffer(s->to_dst_file, s->bioc->data, s->bioc->usage); + qemu_fflush(s->to_dst_file); + } else if (s->state == MIGRATION_STATUS_CANCELLING) { + goto fail; + } + + if (qemu_file_get_error(s->to_dst_file)) { + trace_migration_completion_file_err(); + goto fail; + } + + migrate_set_state(&s->state, current_active_state, + MIGRATION_STATUS_COMPLETED); + return; + +fail: + migrate_set_state(&s->state, current_active_state, + MIGRATION_STATUS_FAILED); +} + bool migrate_colo_enabled(void) { MigrationState *s = migrate_get_current(); @@ -3557,6 +3602,47 @@ static void migration_iteration_finish(MigrationState *s) qemu_mutex_unlock_iothread(); } +static void bg_migration_iteration_finish(MigrationState *s) +{ + qemu_mutex_lock_iothread(); + switch (s->state) { + case MIGRATION_STATUS_COMPLETED: + migration_calculate_complete(s); + break; + + case MIGRATION_STATUS_ACTIVE: + case MIGRATION_STATUS_FAILED: + case MIGRATION_STATUS_CANCELLED: + case MIGRATION_STATUS_CANCELLING: + break; + + default: + /* Should not reach here, but if so, forgive the VM. */ + error_report("%s: Unknown ending state %d", __func__, s->state); + break; + } + + migrate_fd_cleanup_schedule(s); + qemu_mutex_unlock_iothread(); +} + +/* + * Return true if continue to the next iteration directly, false + * otherwise. + */ +static MigIterateState bg_migration_iteration_run(MigrationState *s) +{ + int res; + + res = qemu_savevm_state_iterate(s->to_dst_file, false); + if (res > 0) { + bg_migration_completion(s); + return MIG_ITERATE_BREAK; + } + + return MIG_ITERATE_RESUME; +} + void migration_make_urgent_request(void) { qemu_sem_post(&migrate_get_current()->rate_limit_sem); @@ -3704,6 +3790,165 @@ static void *migration_thread(void *opaque) return NULL; } +static void bg_migration_vm_start_bh(void *opaque) +{ + MigrationState *s = opaque; + + qemu_bh_delete(s->vm_start_bh); + s->vm_start_bh = NULL; + + vm_start(); + s->downtime = qemu_clock_get_ms(QEMU_CLOCK_REALTIME) - s->downtime_start; +} + +/** + * Background snapshot thread, based on live migration code. + * This is an alternative implementation of live migration mechanism + * introduced specifically to support background snapshots. + * + * It takes advantage of userfault_fd write protection mechanism introduced + * in v5.7 kernel. Compared to existing dirty page logging migration much + * lesser stream traffic is produced resulting in smaller snapshot images, + * simply cause of no page duplicates can get into the stream. + * + * Another key point is that generated vmstate stream reflects machine state + * 'frozen' at the beginning of snapshot creation compared to dirty page logging + * mechanism, which effectively results in that saved snapshot is the state of VM + * at the end of the process. + */ +static void *bg_migration_thread(void *opaque) +{ + MigrationState *s = opaque; + int64_t setup_start; + MigThrError thr_error; + QEMUFile *fb; + bool early_fail = true; + + rcu_register_thread(); + object_ref(OBJECT(s)); + + qemu_file_set_rate_limit(s->to_dst_file, INT64_MAX); + + setup_start = qemu_clock_get_ms(QEMU_CLOCK_HOST); + /* + * We want to save vmstate for the moment when migration has been + * initiated but also we want to save RAM content while VM is running. + * The RAM content should appear first in the vmstate. So, we first + * stash the non-RAM part of the vmstate to the temporary buffer, + * then write RAM part of the vmstate to the migration stream + * with vCPUs running and, finally, write stashed non-RAM part of + * the vmstate from the buffer to the migration stream. + */ + s->bioc = qio_channel_buffer_new(128 * 1024); + qio_channel_set_name(QIO_CHANNEL(s->bioc), "vmstate-buffer"); + fb = qemu_fopen_channel_output(QIO_CHANNEL(s->bioc)); + object_unref(OBJECT(s->bioc)); + + update_iteration_initial_status(s); + + qemu_savevm_state_header(s->to_dst_file); + qemu_savevm_state_setup(s->to_dst_file); + + if (qemu_savevm_state_guest_unplug_pending()) { + migrate_set_state(&s->state, MIGRATION_STATUS_SETUP, + MIGRATION_STATUS_WAIT_UNPLUG); + + while (s->state == MIGRATION_STATUS_WAIT_UNPLUG && + qemu_savevm_state_guest_unplug_pending()) { + qemu_sem_timedwait(&s->wait_unplug_sem, 250); + } + + migrate_set_state(&s->state, MIGRATION_STATUS_WAIT_UNPLUG, + MIGRATION_STATUS_ACTIVE); + } else { + migrate_set_state(&s->state, MIGRATION_STATUS_SETUP, + MIGRATION_STATUS_ACTIVE); + } + s->setup_time = qemu_clock_get_ms(QEMU_CLOCK_HOST) - setup_start; + + trace_migration_thread_setup_complete(); + s->downtime_start = qemu_clock_get_ms(QEMU_CLOCK_REALTIME); + + qemu_mutex_lock_iothread(); + + /* + * If VM is currently in suspended state, then, to make a valid runstate + * transition in vm_stop_force_state() we need to wakeup it up. + */ + qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER, NULL); + s->vm_was_running = runstate_is_running(); + + if (global_state_store()) { + goto fail; + } + /* Forcibly stop VM before saving state of vCPUs and devices */ + if (vm_stop_force_state(RUN_STATE_PAUSED)) { + goto fail; + } + /* + * Put vCPUs in sync with shadow context structures, then + * save their state to channel-buffer along with devices. + */ + cpu_synchronize_all_states(); + if (qemu_savevm_state_complete_precopy_non_iterable(fb, false, false)) { + goto fail; + } + /* Now initialize UFFD context and start tracking RAM writes */ + if (ram_write_tracking_start()) { + goto fail; + } + early_fail = false; + + /* + * Start VM from BH handler to avoid write-fault lock here. + * UFFD-WP protection for the whole RAM is already enabled so + * calling VM state change notifiers from vm_start() would initiate + * writes to virtio VQs memory which is in write-protected region. + */ + s->vm_start_bh = qemu_bh_new(bg_migration_vm_start_bh, s); + qemu_bh_schedule(s->vm_start_bh); + + qemu_mutex_unlock_iothread(); + + while (migration_is_active(s)) { + MigIterateState iter_state = bg_migration_iteration_run(s); + if (iter_state == MIG_ITERATE_SKIP) { + continue; + } else if (iter_state == MIG_ITERATE_BREAK) { + break; + } + + /* + * Try to detect any kind of failures, and see whether we + * should stop the migration now. + */ + thr_error = migration_detect_error(s); + if (thr_error == MIG_THR_ERR_FATAL) { + /* Stop migration */ + break; + } + + migration_update_counters(s, qemu_clock_get_ms(QEMU_CLOCK_REALTIME)); + } + + trace_migration_thread_after_loop(); + +fail: + if (early_fail) { + migrate_set_state(&s->state, MIGRATION_STATUS_ACTIVE, + MIGRATION_STATUS_FAILED); + qemu_mutex_unlock_iothread(); + } + + bg_migration_iteration_finish(s); + + qemu_fclose(fb); + object_unref(OBJECT(s)); + rcu_unregister_thread(); + + return NULL; +} + void migrate_fd_connect(MigrationState *s, Error *error_in) { Error *local_err = NULL; @@ -3767,8 +4012,14 @@ void migrate_fd_connect(MigrationState *s, Error *error_in) migrate_fd_cleanup(s); return; } - qemu_thread_create(&s->thread, "live_migration", migration_thread, s, - QEMU_THREAD_JOINABLE); + + if (migrate_background_snapshot()) { + qemu_thread_create(&s->thread, "bg_snapshot", + bg_migration_thread, s, QEMU_THREAD_JOINABLE); + } else { + qemu_thread_create(&s->thread, "live_migration", + migration_thread, s, QEMU_THREAD_JOINABLE); + } s->migration_thread_running = true; } diff --git a/migration/migration.h b/migration/migration.h index f40338cfbf..0723955cd7 100644 --- a/migration/migration.h +++ b/migration/migration.h @@ -20,6 +20,7 @@ #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" @@ -147,8 +148,10 @@ struct MigrationState { /*< public >*/ QemuThread thread; + QEMUBH *vm_start_bh; QEMUBH *cleanup_bh; QEMUFile *to_dst_file; + QIOChannelBuffer *bioc; /* * Protects to_dst_file pointer. We need to make sure we won't * yield or hang during the critical section, since this lock will diff --git a/migration/savevm.c b/migration/savevm.c index d1e6aaed60..d5bf53388f 100644 --- a/migration/savevm.c +++ b/migration/savevm.c @@ -1378,7 +1378,6 @@ int qemu_savevm_state_complete_precopy_iterable(QEMUFile *f, bool in_postcopy) return 0; } -static int qemu_savevm_state_complete_precopy_non_iterable(QEMUFile *f, bool in_postcopy, bool inactivate_disks) diff --git a/migration/savevm.h b/migration/savevm.h index ba64a7e271..aaee2528ed 100644 --- a/migration/savevm.h +++ b/migration/savevm.h @@ -64,5 +64,7 @@ int qemu_loadvm_state(QEMUFile *f); void qemu_loadvm_state_cleanup(void); int qemu_loadvm_state_main(QEMUFile *f, MigrationIncomingState *mis); int qemu_load_device_state(QEMUFile *f); +int qemu_savevm_state_complete_precopy_non_iterable(QEMUFile *f, + bool in_postcopy, bool inactivate_disks); #endif |