[Qemu-devel] [RFC] Introduce vm_stop_permanent()

[Luiz Capitulino <lcapitulino@redhat.com>]

This function should be used when the VM is not supposed to resume
execution (eg. by issuing 'cont' monitor command).

Today, we allow the user to resume execution even when:

 o the guest shuts down and -no-shutdown is used
 o there's a kvm internal error
 o loading the VM state with -loadvm or "loadvm" in the monitor fails

I think only badness can happen from the cases above.

Another possible candidate is migration, that's, when the VM is
automatically stopped following a successful migration.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
---
 cpus.c    |    7 +++++++
 kvm-all.c |    2 +-
 monitor.c |    9 +++++++--
 qerror.c  |    4 ++++
 qerror.h  |    3 +++
 sysemu.h  |    2 ++
 vl.c      |    4 +++-
 7 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/cpus.c b/cpus.c
index 6bf4e3f..5a4a480 100644
--- a/cpus.c
+++ b/cpus.c
@@ -535,6 +535,13 @@ static void qemu_tcg_init_cpu_signals(void)
 }
 #endif /* _WIN32 */
 
+void vm_stop_permanent(int reason)
+{
+    vm_stop(reason);
+    assert(!vm_permanent_stopped);
+    vm_permanent_stopped = 1;
+}
+
 #ifndef CONFIG_IOTHREAD
 int qemu_init_main_loop(void)
 {
diff --git a/kvm-all.c b/kvm-all.c
index cbc2532..4d0ceb3 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -1014,7 +1014,7 @@ int kvm_cpu_exec(CPUState *env)
 
     if (ret < 0) {
         cpu_dump_state(env, stderr, fprintf, CPU_DUMP_CODE);
-        vm_stop(VMSTOP_PANIC);
+        vm_stop_permanent(VMSTOP_PANIC);
     }
 
     env->exit_request = 0;
diff --git a/monitor.c b/monitor.c
index 718935b..86e146c 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1307,7 +1307,10 @@ static int do_cont(Monitor *mon, const QDict *qdict, QObject **ret_data)
 {
     struct bdrv_iterate_context context = { mon, 0 };
 
-    if (incoming_expected) {
+    if (vm_permanent_stopped) {
+        qerror_report(QERR_VM_PERMANENT_STOPPED);
+        return -1;
+    } else if (incoming_expected) {
         qerror_report(QERR_MIGRATION_EXPECTED);
         return -1;
     }
@@ -2814,7 +2817,9 @@ static void do_loadvm(Monitor *mon, const QDict *qdict)
 
     vm_stop(VMSTOP_LOADVM);
 
-    if (load_vmstate(name) == 0 && saved_vm_running) {
+    if (load_vmstate(name) < 0) {
+        vm_permanent_stopped = 1;
+    } else if (saved_vm_running) {
         vm_start();
     }
 }
diff --git a/qerror.c b/qerror.c
index 69c1bc9..c91f763 100644
--- a/qerror.c
+++ b/qerror.c
@@ -219,6 +219,10 @@ static const QErrorStringTable qerror_table[] = {
                      "supported by this qemu version: %(feature)",
     },
     {
+        .error_fmt = QERR_VM_PERMANENT_STOPPED,
+        .desc      = "The Virtual Machine is permanently stopped",
+    },
+    {
         .error_fmt = QERR_VNC_SERVER_FAILED,
         .desc      = "Could not start VNC server on %(target)",
     },
diff --git a/qerror.h b/qerror.h
index 8058456..c759172 100644
--- a/qerror.h
+++ b/qerror.h
@@ -181,6 +181,9 @@ QError *qobject_to_qerror(const QObject *obj);
 #define QERR_UNKNOWN_BLOCK_FORMAT_FEATURE \
     "{ 'class': 'UnknownBlockFormatFeature', 'data': { 'device': %s, 'format': %s, 'feature': %s } }"
 
+#define QERR_VM_PERMANENT_STOPPED \
+    "{ 'class': 'PermanentStopped', 'data': {} }"
+
 #define QERR_VNC_SERVER_FAILED \
     "{ 'class': 'VNCServerFailed', 'data': { 'target': %s } }"
 
diff --git a/sysemu.h b/sysemu.h
index d3013f5..af90fa3 100644
--- a/sysemu.h
+++ b/sysemu.h
@@ -12,6 +12,7 @@
 extern const char *bios_name;
 
 extern int vm_running;
+extern int vm_permanent_stopped;
 extern const char *qemu_name;
 extern uint8_t qemu_uuid[];
 int qemu_uuid_parse(const char *str, uint8_t *uuid);
@@ -39,6 +40,7 @@ void qemu_del_vm_change_state_handler(VMChangeStateEntry *e);
 
 void vm_start(void);
 void vm_stop(int reason);
+void vm_stop_permanent(int reason);
 
 void qemu_system_reset_request(void);
 void qemu_system_shutdown_request(void);
diff --git a/vl.c b/vl.c
index 4b6688b..96403ac 100644
--- a/vl.c
+++ b/vl.c
@@ -186,6 +186,7 @@ NICInfo nd_table[MAX_NICS];
 int vm_running;
 int autostart;
 int incoming_expected; /* Started with -incoming and waiting for incoming */
+int vm_permanent_stopped = 0; /* qemu will never resume if set */
 static int rtc_utc = 1;
 static int rtc_date_offset = -1; /* -1 means no change */
 QEMUClock *rtc_clock;
@@ -1397,7 +1398,7 @@ static void main_loop(void)
             qemu_kill_report();
             monitor_protocol_event(QEVENT_SHUTDOWN, NULL);
             if (no_shutdown) {
-                vm_stop(VMSTOP_SHUTDOWN);
+                vm_stop_permanent(VMSTOP_SHUTDOWN);
             } else
                 break;
         }
@@ -3315,6 +3316,7 @@ int main(int argc, char **argv, char **envp)
     qemu_system_reset(VMRESET_SILENT);
     if (loadvm) {
         if (load_vmstate(loadvm) < 0) {
+            vm_permanent_stopped = 1;
             autostart = 0;
         }
     }
-- 
1.7.6.347.g4db0d