Am 15.10.2014 um 09:55 hat Juan Quintela geschrieben:
> This includes a new section that for now just stores the current qemu state.
>
> Right now, there are only one way to control what is the state of the
> target after migration.
>
> - If you run the target qemu with -S, it would start stopped.
> - If you run the target qemu without -S, it would run just after migration
> finishes.
>
> The problem here is what happens if we start the target without -S and
> there happens one error during migration that puts current state as
> -EIO. Migration would ends (notice that the error happend doing block
> IO, network IO, i.e. nothing related with migration), and when
> migration finish, we would just "continue" running on destination,
> probably hanging the guest/corruption data, whatever.
>
> Signed-off-by: Juan Quintela <quint...@redhat.com>
> ---
> include/migration/migration.h | 4 ++
> migration.c | 88
> +++++++++++++++++++++++++++++++++++++++++--
> vl.c | 1 +
> 3 files changed, 90 insertions(+), 3 deletions(-)
>
> diff --git a/include/migration/migration.h b/include/migration/migration.h
> index 3cb5ba8..bc1069b 100644
> --- a/include/migration/migration.h
> +++ b/include/migration/migration.h
> @@ -174,4 +174,8 @@ size_t ram_control_save_page(QEMUFile *f, ram_addr_t
> block_offset,
> ram_addr_t offset, size_t size,
> int *bytes_sent);
>
> +void register_global_state(void);
> +void global_state_store(void);
> +char *global_state_get_runstate(void);
> +
> #endif
> diff --git a/migration.c b/migration.c
> index 8d675b3..6f7e50e 100644
> --- a/migration.c
> +++ b/migration.c
> @@ -112,10 +112,20 @@ static void process_incoming_migration_co(void *opaque)
> exit(EXIT_FAILURE);
> }
>
> - if (autostart) {
> + /* runstate == "" means that we haven't received it through the
> + * wire, so we obey autostart. runstate == runing means that we
> + * need to run it, we need to make sure that we do it after
> + * everything else has finished. Every other state change is done
> + * at the post_load function */
> +
> + if (strcmp(global_state_get_runstate(), "running") == 0 ) {
> vm_start();
Does this mean that -S is now ignored in the common case? Wouldn't it be
better to change only the case without -S? Otherwise I guess libvirt
will get quite confused.
> - } else {
> - runstate_set(RUN_STATE_PAUSED);
> + } else if (strcmp(global_state_get_runstate(), "") == 0 ) {
> + if (autostart) {
> + vm_start();
> + } else {
> + runstate_set(RUN_STATE_PAUSED);
> + }
> }
> }
>
> @@ -608,6 +618,7 @@ static void *migration_thread(void *opaque)
> qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER);
> old_vm_running = runstate_is_running();
>
> + global_state_store();
> ret = vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);
> if (ret >= 0) {
> qemu_file_set_rate_limit(s->file, INT64_MAX);
> @@ -699,3 +710,74 @@ void migrate_fd_connect(MigrationState *s)
> qemu_thread_create(&s->thread, "migration", migration_thread, s,
> QEMU_THREAD_JOINABLE);
> }
> +
> +typedef struct {
> + int32_t size;
> + uint8_t runstate[100];
> +} GlobalState;
> +
> +static GlobalState global_state;
> +
> +void global_state_store(void)
> +{
> + if (runstate_store((char*)global_state.runstate,
> + sizeof(global_state.runstate)) == -1) {
> + printf("Runstate is too big\n");
> + exit(-1);
> + }
> +}
Not sure if the concept of a single GlobalStore that calls all the
individual handlers for each piece of global state is optimal.
Can't we use something like vmstate_register()? Perhaps even the same
function, just with dev == NULL? (Actually, you even do this below, to
register the global state. So I guess I'm only disagreeing on the
granularity of having only a single section with a single handler
function for the whole global state.)
> +char *global_state_get_runstate(void)
> +{
> + return (char *)global_state.runstate;
> +}
> +
> +static int global_state_post_load(void *opaque, int version_id)
> +{
> + GlobalState *s = opaque;
> + int ret = 0;
> + char *runstate = (char*)s->runstate;
> +
> + printf("loaded state: %s\n", runstate);
> +
> + if (strcmp(runstate, "running") != 0) {
> +
> + RunState r = runstate_index(runstate);
> +
> + if (r == -1) {
> + printf("Unknown received state %s\n", runstate);
> + return -1;
> + }
> + ret = vm_stop_force_state(r);
> + }
> +
> + return ret;
> +}
> +
> +static void global_state_pre_save(void *opaque)
> +{
> + GlobalState *s = opaque;
> +
> + s->size = strlen((char*)s->runstate) + 1;
> + printf("saved state: %s\n", s->runstate);
> +}
> +
> +static const VMStateDescription vmstate_globalstate = {
> + .name = "globalstate",
> + .version_id = 1,
> + .minimum_version_id = 1,
> + .post_load = global_state_post_load,
> + .pre_save = global_state_pre_save,
> + .fields = (VMStateField[]) {
> + VMSTATE_INT32(size, GlobalState),
> + VMSTATE_BUFFER(runstate, GlobalState),
> + VMSTATE_END_OF_LIST()
> + },
> +};
Could this be optional and suppressed for "running"? Then we should be
able to keep compatibility with older versions in the common case.
> +
> +void register_global_state(void)
> +{
> + /* We would use it independently that we receive it */
> + strcpy((char*)&global_state.runstate, "");
> + vmstate_register(NULL, 0, &vmstate_globalstate, &global_state);
> +}
> diff --git a/vl.c b/vl.c
> index 1788b6a..75e855e 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -4511,6 +4511,7 @@ int main(int argc, char **argv, char **envp)
> return 0;
> }
>
> + register_global_state();
> if (incoming) {
> Error *local_err = NULL;
> qemu_start_incoming_migration(incoming, &local_err);
> --
> 2.1.0
Kevin
