Re: [PATCH v12 rebased 1/8] preserve cpu runstate

Marcelo Tosatti
2013-02-08T01:53:43Z

On Wed, Jan 23, 2013 at 03:19:22PM +0800, Hu Tao wrote:
> This patch enables preservation of cpu runstate during save/load vm.
> So when a vm is restored from snapshot, the cpu runstate is restored,
> too.
>
> See following example:
>
> # save two vms: one is running, the other is paused
> (qemu) info status
> VM status: running
> (qemu) savevm running
> (qemu) stop
> (qemu) info status
> VM status: paused
> (qemu) savevm paused
>
> # restore the one running
> (qemu) info status
> VM status: paused
> (qemu) loadvm running
> (qemu) info status
> VM status: running
>
> # restore the one paused
> (qemu) loadvm paused
> (qemu) info status
> VM status: paused
> (qemu) cont
> (qemu)info status
> VM status: running
>
>
> Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>

Lack of pause state on guest images is annoying.

Fail to see why the panic feature depends on preservation of cpu
runstate.

> include/sysemu/sysemu.h | 2 ++
> migration.c | 6 +-----
> monitor.c | 5 ++---
> savevm.c | 1 +
> vl.c | 34 ++++++++++++++++++++++++++++++++++
> 5 files changed, 40 insertions(+), 8 deletions(-)
>
> diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
> index 337ce7d..7a69fde 100644
> --- a/include/sysemu/sysemu.h
> +++ b/include/sysemu/sysemu.h
> @@ -19,6 +19,8 @@ extern uint8_t qemu_uuid[];
> int qemu_uuid_parse(const char *str, uint8_t *uuid);
> #define UUID_FMT "%02hhx%02hhx%02hhx%02hhx-%02hhx%02hhx-%02hhx%02hhx-%02hhx%02hhx-%02hhx%02hhx%02hhx%02hhx%02hhx%02hhx"
>
> +void save_run_state(void);
> +void load_run_state(void);
> bool runstate_check(RunState state);
> void runstate_set(RunState new_state);
> int runstate_is_running(void);
> diff --git a/migration.c b/migration.c
> index 77c1971..f96cfd6 100644
> --- a/migration.c
> +++ b/migration.c
> @@ -108,11 +108,7 @@ static void process_incoming_migration_co(void *opaque)
> /* Make sure all file formats flush their mutable metadata */
> bdrv_invalidate_cache_all();
>
> - if (autostart) {
> - vm_start();
> - } else {
> - runstate_set(RUN_STATE_PAUSED);
> - }
> + load_run_state();
> }
>
> static void enter_migration_coroutine(void *opaque)
> diff --git a/monitor.c b/monitor.c
> index 20bd19b..9381ed0 100644
> --- a/monitor.c
> +++ b/monitor.c
> @@ -2059,13 +2059,12 @@ void qmp_closefd(const char *fdname, Error **errp)
>
> static void do_loadvm(Monitor *mon, const QDict *qdict)
> {
> - int saved_vm_running = runstate_is_running();
> const char *name = qdict_get_str(qdict, "name");
>
> vm_stop(RUN_STATE_RESTORE_VM);
>
> - if (load_vmstate(name) == 0 && saved_vm_running) {
> - vm_start();
> + if (load_vmstate(name) == 0) {
> + load_run_state();
> }
> }
>
> diff --git a/savevm.c b/savevm.c
> index 304d1ef..10f1d56 100644
> --- a/savevm.c
> +++ b/savevm.c
> @@ -2112,6 +2112,7 @@ void do_savevm(Monitor *mon, const QDict *qdict)
> }
>
> saved_vm_running = runstate_is_running();
> + save_run_state();
> vm_stop(RUN_STATE_SAVE_VM);
>
> memset(sn, 0, sizeof(*sn));
> diff --git a/vl.c b/vl.c
> index 4ee1302..b0bcf1e 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -520,6 +520,7 @@ static int default_driver_check(QemuOpts *opts, void *opaque)
> /* QEMU state */
>
> static RunState current_run_state = RUN_STATE_PRELAUNCH;
> +static RunState saved_run_state = RUN_STATE_PRELAUNCH;
>
> typedef struct {
> RunState from;
> @@ -543,6 +544,7 @@ static const RunStateTransition runstate_transitions_def[] = {
> { RUN_STATE_PAUSED, RUN_STATE_FINISH_MIGRATE },
>
> { RUN_STATE_POSTMIGRATE, RUN_STATE_RUNNING },
> + { RUN_STATE_POSTMIGRATE, RUN_STATE_PAUSED },
> { RUN_STATE_POSTMIGRATE, RUN_STATE_FINISH_MIGRATE },
>
> { RUN_STATE_PRELAUNCH, RUN_STATE_RUNNING },
> @@ -553,6 +555,7 @@ static const RunStateTransition runstate_transitions_def[] = {
> { RUN_STATE_FINISH_MIGRATE, RUN_STATE_POSTMIGRATE },
>
> { RUN_STATE_RESTORE_VM, RUN_STATE_RUNNING },
> + { RUN_STATE_RESTORE_VM, RUN_STATE_PAUSED },
>
> { RUN_STATE_RUNNING, RUN_STATE_DEBUG },
> { RUN_STATE_RUNNING, RUN_STATE_INTERNAL_ERROR },
> @@ -582,11 +585,39 @@ static const RunStateTransition runstate_transitions_def[] = {
>
> static bool runstate_valid_transitions[RUN_STATE_MAX][RUN_STATE_MAX];
>
> +void save_run_state(void)
> +{
> + saved_run_state = current_run_state;
> +}
> +
> +void load_run_state(void)
> +{
> + if (saved_run_state == RUN_STATE_RUNNING) {
> + vm_start();
> + } else if (!runstate_check(saved_run_state)) {
> + runstate_set(saved_run_state);
> + } else {
> + ; /* leave unchanged */
> + }
> +}
> +
> bool runstate_check(RunState state)
> {
> return current_run_state == state;
> }
>
> +static void runstate_save(QEMUFile *f, void *opaque)
> +{
> + qemu_put_byte(f, saved_run_state);
> +}
> +
> +static int runstate_load(QEMUFile *f, void *opaque, int version_id)
> +{
> + saved_run_state = qemu_get_byte(f);
> +
> + return 0;
> +}

This breaks loading images without support for runstate information.
Is it possible to overcome this limitation?

Would be happier if this patch could be debated on QEMU list.