Restoring a snapshot can break a suspended guest. Snapshots suffer from the same suspended-state issues that affect live migration, plus they must handle an additional problematic scenario, which is that a running vm must remain running if it loads a suspended snapshot. Currently, after loading such a snapshot, the vm_start fails. The runstate is RUNNING, but the guest is not.
To save, the vm_stop call now completely stops the suspended state, courtesy of a recent patch. Finish with vm_resume to leave the vm in the state it had prior to the save, correctly restoring the suspended state. To load, if the snapshot is not suspended, then vm_stop + vm_resume correctly handles all states, and leaves the vm in the state it had prior to the load. However, if the snapshot is suspended, restoration is trickier. First, call vm_resume to restore the state to suspended so the current state matches the saved state. Then, if the pre-load state is running, call wakeup to resume running. Prior to these changes, the vm_stop to RUN_STATE_SAVE_VM and RUN_STATE_RESTORE_VM did not change runstate if the current state was paused, suspended, or prelaunch, but now it does, so allow these transitions. Signed-off-by: Steve Sistare <steven.sist...@oracle.com> --- include/migration/snapshot.h | 7 +++++++ migration/migration-hmp-cmds.c | 8 +++++--- migration/savevm.c | 23 +++++++++++++---------- system/runstate.c | 5 +++++ system/vl.c | 2 ++ 5 files changed, 32 insertions(+), 13 deletions(-) diff --git a/include/migration/snapshot.h b/include/migration/snapshot.h index e72083b..9e4dcaa 100644 --- a/include/migration/snapshot.h +++ b/include/migration/snapshot.h @@ -16,6 +16,7 @@ #define QEMU_MIGRATION_SNAPSHOT_H #include "qapi/qapi-builtin-types.h" +#include "qapi/qapi-types-run-state.h" /** * save_snapshot: Save an internal snapshot. @@ -61,4 +62,10 @@ bool delete_snapshot(const char *name, bool has_devices, strList *devices, Error **errp); +/** + * load_snapshot_resume: Restore runstate after loading snapshot. + * @state: state to restore + */ +void load_snapshot_resume(RunState state); + #endif diff --git a/migration/migration-hmp-cmds.c b/migration/migration-hmp-cmds.c index 86ae832..c8d70bc 100644 --- a/migration/migration-hmp-cmds.c +++ b/migration/migration-hmp-cmds.c @@ -399,15 +399,17 @@ void hmp_info_migrate_parameters(Monitor *mon, const QDict *qdict) void hmp_loadvm(Monitor *mon, const QDict *qdict) { - int saved_vm_running = runstate_is_running(); + RunState saved_state = runstate_get(); + const char *name = qdict_get_str(qdict, "name"); Error *err = NULL; vm_stop(RUN_STATE_RESTORE_VM); - if (load_snapshot(name, NULL, false, NULL, &err) && saved_vm_running) { - vm_start(); + if (load_snapshot(name, NULL, false, NULL, &err)) { + load_snapshot_resume(saved_state); } + hmp_handle_error(mon, err); } diff --git a/migration/savevm.c b/migration/savevm.c index eec5503..78697c0 100644 --- a/migration/savevm.c +++ b/migration/savevm.c @@ -3046,7 +3046,7 @@ bool save_snapshot(const char *name, bool overwrite, const char *vmstate, QEMUSnapshotInfo sn1, *sn = &sn1; int ret = -1, ret2; QEMUFile *f; - int saved_vm_running; + RunState saved_state = runstate_get(); uint64_t vm_state_size; g_autoptr(GDateTime) now = g_date_time_new_now_local(); AioContext *aio_context; @@ -3094,8 +3094,6 @@ bool save_snapshot(const char *name, bool overwrite, const char *vmstate, } aio_context = bdrv_get_aio_context(bs); - saved_vm_running = runstate_is_running(); - global_state_store(); vm_stop(RUN_STATE_SAVE_VM); @@ -3163,9 +3161,7 @@ bool save_snapshot(const char *name, bool overwrite, const char *vmstate, bdrv_drain_all_end(); - if (saved_vm_running) { - vm_start(); - } + vm_resume(saved_state); return ret == 0; } @@ -3339,6 +3335,14 @@ err_drain: return false; } +void load_snapshot_resume(RunState state) +{ + vm_resume(state); + if (state == RUN_STATE_RUNNING && runstate_get() == RUN_STATE_SUSPENDED) { + qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER, NULL); + } +} + bool delete_snapshot(const char *name, bool has_devices, strList *devices, Error **errp) { @@ -3403,16 +3407,15 @@ static void snapshot_load_job_bh(void *opaque) { Job *job = opaque; SnapshotJob *s = container_of(job, SnapshotJob, common); - int orig_vm_running; + RunState orig_state = runstate_get(); job_progress_set_remaining(&s->common, 1); - orig_vm_running = runstate_is_running(); vm_stop(RUN_STATE_RESTORE_VM); s->ret = load_snapshot(s->tag, s->vmstate, true, s->devices, s->errp); - if (s->ret && orig_vm_running) { - vm_start(); + if (s->ret) { + load_snapshot_resume(orig_state); } job_progress_update(&s->common, 1); diff --git a/system/runstate.c b/system/runstate.c index e2fa204..ca9eb54 100644 --- a/system/runstate.c +++ b/system/runstate.c @@ -77,6 +77,7 @@ typedef struct { static const RunStateTransition runstate_transitions_def[] = { { RUN_STATE_PRELAUNCH, RUN_STATE_INMIGRATE }, + { RUN_STATE_PRELAUNCH, RUN_STATE_SUSPENDED }, { RUN_STATE_DEBUG, RUN_STATE_RUNNING }, { RUN_STATE_DEBUG, RUN_STATE_FINISH_MIGRATE }, @@ -132,6 +133,7 @@ static const RunStateTransition runstate_transitions_def[] = { { RUN_STATE_RESTORE_VM, RUN_STATE_RUNNING }, { RUN_STATE_RESTORE_VM, RUN_STATE_PRELAUNCH }, + { RUN_STATE_RESTORE_VM, RUN_STATE_SUSPENDED }, { RUN_STATE_COLO, RUN_STATE_RUNNING }, { RUN_STATE_COLO, RUN_STATE_PRELAUNCH }, @@ -150,6 +152,7 @@ static const RunStateTransition runstate_transitions_def[] = { { RUN_STATE_RUNNING, RUN_STATE_COLO}, { RUN_STATE_SAVE_VM, RUN_STATE_RUNNING }, + { RUN_STATE_SAVE_VM, RUN_STATE_SUSPENDED }, { RUN_STATE_SHUTDOWN, RUN_STATE_PAUSED }, { RUN_STATE_SHUTDOWN, RUN_STATE_FINISH_MIGRATE }, @@ -163,6 +166,8 @@ static const RunStateTransition runstate_transitions_def[] = { { RUN_STATE_SUSPENDED, RUN_STATE_PRELAUNCH }, { RUN_STATE_SUSPENDED, RUN_STATE_COLO}, { RUN_STATE_SUSPENDED, RUN_STATE_PAUSED}, + { RUN_STATE_SUSPENDED, RUN_STATE_SAVE_VM }, + { RUN_STATE_SUSPENDED, RUN_STATE_RESTORE_VM }, { RUN_STATE_WATCHDOG, RUN_STATE_RUNNING }, { RUN_STATE_WATCHDOG, RUN_STATE_FINISH_MIGRATE }, diff --git a/system/vl.c b/system/vl.c index 2bcd9ef..2fbbbba 100644 --- a/system/vl.c +++ b/system/vl.c @@ -2706,7 +2706,9 @@ void qmp_x_exit_preconfig(Error **errp) qemu_machine_creation_done(); if (loadvm) { + RunState state = autostart ? RUN_STATE_RUNNING : runstate_get(); load_snapshot(loadvm, NULL, false, NULL, &error_fatal); + load_snapshot_resume(state); } if (replay_mode != REPLAY_MODE_NONE) { replay_vmstate_init(); -- 1.8.3.1