cpus: stop vm in suspended runstate

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:

  old behavior:
    RUN_STATE_SUSPENDED --> stop --> RUN_STATE_SUSPENDED

  new behavior:
    RUN_STATE_SUSPENDED --> stop --> RUN_STATE_PAUSED
    RUN_STATE_PAUSED    --> cont --> RUN_STATE_SUSPENDED

For example:

    (qemu) info status
    VM status: paused (suspended)

    (qemu) stop
    (qemu) info status
    VM status: paused

    (qemu) system_wakeup
    Error: Unable to wake up: guest is not in suspended state

    (qemu) cont
    (qemu) info status
    VM status: paused (suspended)

    (qemu) system_wakeup
    (qemu) info status
    VM status: running

Suggested-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/1704312341-66640-3-git-send-email-steven.sistare@oracle.com
Signed-off-by: Peter Xu <peterx@redhat.com>

diff --git a/include/sysemu/runstate.h b/include/sysemu/runstate.h
index 88a67e22b0c185bf2ecc1d05646a4d9f3026e36c..618eb491af552c4bfaa893a6ac373ecf938d0ba4 100644 (file)
--- a/include/sysemu/runstate.h
+++ b/include/sysemu/runstate.h
@@ -40,6 +40,15 @@ static inline bool shutdown_caused_by_guest(ShutdownCause cause)
     return cause >= SHUTDOWN_CAUSE_GUEST_SHUTDOWN;
 }
 
+/*
+ * In a "live" state, the vcpu clock is ticking, and the runstate notifiers
+ * think we are running.
+ */
+static inline bool runstate_is_live(RunState state)
+{
+    return state == RUN_STATE_RUNNING || state == RUN_STATE_SUSPENDED;
+}
+
 void vm_start(void);
 
 /**

diff --git a/qapi/misc.json b/qapi/misc.json
index cda2effa8155a8a6175036f678877ec2c7cdd1bf..3622d98d010a6195f78804f61fba7198c0e8b55f 100644 (file)
--- a/qapi/misc.json
+++ b/qapi/misc.json
@@ -134,7 +134,7 @@
 ##
 # @stop:
 #
-# Stop all guest VCPU execution.
+# Stop guest 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 VM execution.
 #
 # Since: 0.14
 #
@@ -165,6 +168,10 @@
 #     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/qapi/run-state.json b/qapi/run-state.json
index f216ba54ec4c16146e0f77f316be61ab42fa7f9b..ca05502e0ad574e820b7dd70ce4be0c937a3575b 100644 (file)
--- a/qapi/run-state.json
+++ b/qapi/run-state.json
@@ -102,7 +102,7 @@
 ##
 # @StatusInfo:
 #
-# Information about VCPU run state
+# Information about VM run state
 #
 # @running: true if all VCPUs are runnable, false if not runnable
 #
@@ -130,9 +130,9 @@
 ##
 # @query-status:
 #
-# Query the run status of all VCPUs
+# Query the run status of the VM
 #
-# Returns: @StatusInfo reflecting all VCPUs
+# Returns: @StatusInfo reflecting the VM
 #
 # Since: 0.14
 #

diff --git a/system/cpus.c b/system/cpus.c
index 9f631ab734c743d15fca8607d46b2824d52b003a..f162435dd4586df1b8f3ef2b3ffbb00cd7f4c07b 100644 (file)
--- 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_live(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();
@@ -694,11 +698,13 @@ int vm_stop(RunState state)
 
 /**
  * Prepare for (re)starting the VM.
- * Returns -1 if the vCPUs are not to be restarted (e.g. if they are already
- * running or in case of an error condition), 0 otherwise.
+ * Returns 0 if the vCPUs should be restarted, -1 on an error condition,
+ * and 1 otherwise.
  */
 int vm_prepare_start(bool step_pending)
 {
+    int ret = vm_was_suspended ? 1 : 0;
+    RunState state = vm_was_suspended ? RUN_STATE_SUSPENDED : RUN_STATE_RUNNING;
     RunState requested;
 
     qemu_vmstop_requested(&requested);
@@ -729,9 +735,10 @@ int vm_prepare_start(bool step_pending)
     qapi_event_send_resume();
 
     cpu_enable_ticks();
-    runstate_set(RUN_STATE_RUNNING);
-    vm_state_notify(1, RUN_STATE_RUNNING);
-    return 0;
+    runstate_set(state);
+    vm_state_notify(1, state);
+    vm_was_suspended = false;
+    return ret;
 }
 
 void vm_start(void)
@@ -745,7 +752,7 @@ void vm_start(void)
    current state is forgotten forever */
 int vm_stop_force_state(RunState state)
 {
-    if (runstate_is_running()) {
+    if (runstate_is_live(runstate_get())) {
         return vm_stop(state);
     } else {
         int ret;

diff --git a/system/runstate.c b/system/runstate.c
index ea9d6c2a32a45541a87cecaba569583f60624ea2..e2fa2040cbd4e50f6dbe8a46ecaff825634f4460 100644 (file)
--- 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);
 }
 
 /*