On Thu, Nov 30, 2023 at 01:37:16PM -0800, Steve Sistare wrote:
> Currently, a vm in the suspended state is not completely stopped. The VCPUs
> have been paused, but the cpu clock still runs, and runstate notifiers for
> the transition to stopped have not been called. This causes problems for
> live migration. Stale cpu timers_state is saved to the migration stream,
> causing time errors in the guest when it wakes from suspend, and state that
> would have been modified by runstate notifiers is wrong.
>
> Modify vm_stop to completely stop the vm if the current state is suspended,
> transition to RUN_STATE_PAUSED, and remember that the machine was suspended.
> Modify vm_start to restore the suspended state.
>
> This affects all callers of vm_stop and vm_start, notably, the qapi stop and
> cont commands. For example:
>
> (qemu) info status
> VM status: paused (suspended)
>
> (qemu) stop
> (qemu) info status
> VM status: paused
>
> (qemu) cont
> (qemu) info status
> VM status: paused (suspended)
>
> (qemu) system_wakeup
> (qemu) info status
> VM status: running
So system_wakeup for a stopped (but used to be suspended) VM will fail
directly, not touching vm_was_suspended. It's not mentioned here, but that
behavior makes sense to me.
>
> Suggested-by: Peter Xu <pet...@redhat.com>
> Signed-off-by: Steve Sistare <steven.sist...@oracle.com>
Reviewed-by: Peter Xu <pet...@redhat.com>
Since you touched qapi/, please copy maintainers too. I've copied Markus
and Eric in this reply.
I also have some nitpicks which may not affect the R-b, please see below.
> ---
> include/sysemu/runstate.h | 5 +++++
> qapi/misc.json | 10 ++++++++--
> system/cpus.c | 19 ++++++++++++++-----
> system/runstate.c | 3 +++
> 4 files changed, 30 insertions(+), 7 deletions(-)
>
> diff --git a/include/sysemu/runstate.h b/include/sysemu/runstate.h
> index f6a337b..1d6828f 100644
> --- a/include/sysemu/runstate.h
> +++ b/include/sysemu/runstate.h
> @@ -40,6 +40,11 @@ static inline bool shutdown_caused_by_guest(ShutdownCause
> cause)
> return cause >= SHUTDOWN_CAUSE_GUEST_SHUTDOWN;
> }
>
> +static inline bool runstate_is_started(RunState state)
Would runstate_has_vm_running() sound better? It is a bit awkward when
saying something like "start a runstate".
> +{
> + return state == RUN_STATE_RUNNING || state == RUN_STATE_SUSPENDED;
> +}
> +
> void vm_start(void);
>
> /**
> diff --git a/qapi/misc.json b/qapi/misc.json
> index cda2eff..efb8d44 100644
> --- a/qapi/misc.json
> +++ b/qapi/misc.json
> @@ -134,7 +134,7 @@
> ##
> # @stop:
> #
> -# Stop all guest VCPU execution.
> +# Stop all guest VCPU and VM execution.
> #
> # Since: 0.14
> #
> @@ -143,6 +143,9 @@
> # the guest remains paused once migration finishes, as if the -S
> # option was passed on the command line.
> #
> +# In the "suspended" state, it will completely stop the VM and
> +# cause a transition to the "paused" state. (Since 9.0)
> +#
> # Example:
> #
> # -> { "execute": "stop" }
> @@ -153,7 +156,7 @@
> ##
> # @cont:
> #
> -# Resume guest VCPU execution.
> +# Resume guest VCPU and VM execution.
> #
> # Since: 0.14
> #
> @@ -165,6 +168,9 @@
> # guest starts once migration finishes, removing the effect of the
> # -S command line option if it was passed.
> #
> +# If the VM was previously suspended, and not been reset or woken,
> +# this command will transition back to the "suspended" state. (Since 9.0)
> +#
> # Example:
> #
> # -> { "execute": "cont" }
> diff --git a/system/cpus.c b/system/cpus.c
> index ef7a0d3..cbc6d6d 100644
> --- a/system/cpus.c
> +++ b/system/cpus.c
> @@ -277,11 +277,15 @@ bool vm_get_suspended(void)
> static int do_vm_stop(RunState state, bool send_stop)
> {
> int ret = 0;
> + RunState oldstate = runstate_get();
>
> - if (runstate_is_running()) {
> + if (runstate_is_started(oldstate)) {
> + vm_was_suspended = (oldstate == RUN_STATE_SUSPENDED);
> runstate_set(state);
> cpu_disable_ticks();
> - pause_all_vcpus();
> + if (oldstate == RUN_STATE_RUNNING) {
> + pause_all_vcpus();
> + }
> vm_state_notify(0, state);
> if (send_stop) {
> qapi_event_send_stop();
> @@ -736,8 +740,13 @@ int vm_prepare_start(bool step_pending, RunState state)
>
> void vm_start(void)
> {
> - if (!vm_prepare_start(false, RUN_STATE_RUNNING)) {
> - resume_all_vcpus();
> + RunState state = vm_was_suspended ? RUN_STATE_SUSPENDED :
> RUN_STATE_RUNNING;
> +
> + if (!vm_prepare_start(false, state)) {
> + if (state == RUN_STATE_RUNNING) {
> + resume_all_vcpus();
> + }
> + vm_was_suspended = false;
> }
> }
>
> @@ -745,7 +754,7 @@ void vm_start(void)
> current state is forgotten forever */
> int vm_stop_force_state(RunState state)
> {
> - if (runstate_is_running()) {
> + if (runstate_is_started(runstate_get())) {
> return vm_stop(state);
> } else {
> int ret;
> diff --git a/system/runstate.c b/system/runstate.c
> index ea9d6c2..e2fa204 100644
> --- a/system/runstate.c
> +++ b/system/runstate.c
> @@ -108,6 +108,7 @@ static const RunStateTransition
> runstate_transitions_def[] = {
> { RUN_STATE_PAUSED, RUN_STATE_POSTMIGRATE },
> { RUN_STATE_PAUSED, RUN_STATE_PRELAUNCH },
> { RUN_STATE_PAUSED, RUN_STATE_COLO},
> + { RUN_STATE_PAUSED, RUN_STATE_SUSPENDED},
>
> { RUN_STATE_POSTMIGRATE, RUN_STATE_RUNNING },
> { RUN_STATE_POSTMIGRATE, RUN_STATE_FINISH_MIGRATE },
> @@ -161,6 +162,7 @@ static const RunStateTransition
> runstate_transitions_def[] = {
> { RUN_STATE_SUSPENDED, RUN_STATE_FINISH_MIGRATE },
> { RUN_STATE_SUSPENDED, RUN_STATE_PRELAUNCH },
> { RUN_STATE_SUSPENDED, RUN_STATE_COLO},
> + { RUN_STATE_SUSPENDED, RUN_STATE_PAUSED},
>
> { RUN_STATE_WATCHDOG, RUN_STATE_RUNNING },
> { RUN_STATE_WATCHDOG, RUN_STATE_FINISH_MIGRATE },
> @@ -502,6 +504,7 @@ void qemu_system_reset(ShutdownCause reason)
> qapi_event_send_reset(shutdown_caused_by_guest(reason), reason);
> }
> cpu_synchronize_all_post_reset();
> + vm_set_suspended(false);
> }
>
> /*
> --
> 1.8.3.1
>
--
Peter Xu
