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migration: preserve suspended for snapshot

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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.

To save, the existing vm_stop call now completely stops the suspended
state.  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
suspended, but now it does, so allow these transitions.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/1704312341-66640-8-git-send-email-steven.sistare@oracle.com
Signed-off-by: Peter Xu <peterx@redhat.com>
This commit is contained in:
Steve Sistare 2024-01-03 12:05:36 -08:00 • committed by Peter Xu
parent b4e9ddccd1
commit 58b105703e
5 changed files with 32 additions and 13 deletions
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8
migration/migration-hmp-cmds.c
View file

@ -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);
}