[Qemu-devel] [RFC 4/6] CLI: add -paused option

[Igor Mammedov <imammedo@redhat.com>]

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
 include/sysemu/sysemu.h |  1 +
 qemu-options.hx         | 15 ++++++++++++++
 qmp.c                   |  5 +++++
 vl.c                    | 54 ++++++++++++++++++++++++++++++++++++++++++++++++-
 4 files changed, 74 insertions(+), 1 deletion(-)

diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
index b213696..3feb94f 100644
--- a/include/sysemu/sysemu.h
+++ b/include/sysemu/sysemu.h
@@ -66,6 +66,7 @@ typedef enum WakeupReason {
     QEMU_WAKEUP_REASON_OTHER,
 } WakeupReason;
 
+void qemu_exit_preconfig_request(void);
 void qemu_system_reset_request(ShutdownCause reason);
 void qemu_system_suspend_request(void);
 void qemu_register_suspend_notifier(Notifier *notifier);
diff --git a/qemu-options.hx b/qemu-options.hx
index 39225ae..bd44db8 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3498,6 +3498,21 @@ STEXI
 Run the emulation in single step mode.
 ETEXI
 
+DEF("paused", HAS_ARG, QEMU_OPTION_paused, \
+    "-paused [state=]postconf|preconf\n"
+    "                postconf: pause QEMU after machine is initialized\n"
+    "                preconf: pause QEMU before machine is initialized\n",
+    QEMU_ARCH_ALL)
+STEXI
+@item -paused
+@findex -paused
+if set enabled interactive configuration stages before machine emulation starts.
+'postconf' option value mimics -S option behaviour where machine is created
+but emulation isn't started. 'preconf' option value pauses QEMU before machine
+is created, which allows to query and configure properties affecting machine
+initialization. Use monitor/QMP command 'cont' to go to exit paused state.
+ETEXI
+
 DEF("S", 0, QEMU_OPTION_S, \
     "-S              freeze CPU at startup (use 'c' to start execution)\n",
     QEMU_ARCH_ALL)
diff --git a/qmp.c b/qmp.c
index e8c3031..49e9a5c 100644
--- a/qmp.c
+++ b/qmp.c
@@ -167,6 +167,11 @@ void qmp_cont(Error **errp)
     BlockBackend *blk;
     Error *local_err = NULL;
 
+    if (runstate_check(RUN_STATE_PRELAUNCH)) {
+        qemu_exit_preconfig_request();
+        return;
+    }
+
     /* if there is a dump in background, we should wait until the dump
      * finished */
     if (dump_in_progress()) {
diff --git a/vl.c b/vl.c
index 3fed457..30631fd 100644
--- a/vl.c
+++ b/vl.c
@@ -555,6 +555,20 @@ static QemuOptsList qemu_fw_cfg_opts = {
     },
 };
 
+static QemuOptsList qemu_paused_opts = {
+    .name = "paused",
+    .implied_opt_name = "state",
+    .head = QTAILQ_HEAD_INITIALIZER(qemu_paused_opts.head),
+    .desc = {
+        {
+            .name = "state",
+            .type = QEMU_OPT_STRING,
+            .help = "Pause state of QEMU on startup",
+        },
+        { /* end of list */ }
+    },
+};
+
 /**
  * Get machine options
  *
@@ -1689,6 +1703,11 @@ static pid_t shutdown_pid;
 static int powerdown_requested;
 static int debug_requested;
 static int suspend_requested;
+static enum {
+    PRECONFIG_CONT = 0,
+    PRECONFIG_PAUSE,
+    PRECONFIG_SKIP,
+} preconfig_requested;
 static WakeupReason wakeup_reason;
 static NotifierList powerdown_notifiers =
     NOTIFIER_LIST_INITIALIZER(powerdown_notifiers);
@@ -1773,6 +1792,11 @@ static int qemu_debug_requested(void)
     return r;
 }
 
+void qemu_exit_preconfig_request(void)
+{
+    preconfig_requested = PRECONFIG_CONT;
+}
+
 /*
  * Reset the VM. Issue an event unless @reason is SHUTDOWN_CAUSE_NONE.
  */
@@ -1939,6 +1963,12 @@ static bool main_loop_should_exit(void)
     RunState r;
     ShutdownCause request;
 
+    if (runstate_check(RUN_STATE_PRELAUNCH)) {
+        if (preconfig_requested == PRECONFIG_CONT) {
+            preconfig_requested = PRECONFIG_SKIP;
+            return true;
+        }
+    }
     if (qemu_debug_requested()) {
         vm_stop(RUN_STATE_DEBUG);
     }
@@ -3177,6 +3207,7 @@ int main(int argc, char **argv, char **envp)
     qemu_add_opts(&qemu_icount_opts);
     qemu_add_opts(&qemu_semihosting_config_opts);
     qemu_add_opts(&qemu_fw_cfg_opts);
+    qemu_add_opts(&qemu_paused_opts);
     module_call_init(MODULE_INIT_OPTS);
 
     runstate_init();
@@ -3845,6 +3876,26 @@ int main(int argc, char **argv, char **envp)
                     exit(1);
                 }
                 break;
+            case QEMU_OPTION_paused:
+                {
+                    const char *value;
+
+                    opts = qemu_opts_parse_noisily(qemu_find_opts("paused"),
+                                                   optarg, true);
+                    if (opts == NULL) {
+                        exit(1);
+                    }
+                    value = qemu_opt_get(opts, "state");
+                    if (!strcmp(value, "postconf")) {
+                        autostart = 0;
+                    } else if (!strcmp(value, "preconf")) {
+                        preconfig_requested = PRECONFIG_PAUSE;
+                    } else {
+                        error_report("incomplete '-paused' option\n");
+                        exit(1);
+                    }
+                    break;
+                }
             case QEMU_OPTION_enable_kvm:
                 olist = qemu_find_opts("machine");
                 qemu_opts_parse_noisily(olist, "accel=kvm", false);
@@ -4731,7 +4782,6 @@ int main(int argc, char **argv, char **envp)
     current_machine->boot_order = boot_order;
     current_machine->cpu_model = cpu_model;
 
-
     /* parse features once if machine provides default cpu_type */
     if (machine_class->default_cpu_type) {
         current_machine->cpu_type = machine_class->default_cpu_type;
@@ -4741,6 +4791,8 @@ int main(int argc, char **argv, char **envp)
         }
     }
 
+    main_loop(); /* do monitor/qmp handling at preconfig state if requested */
+
     machine_run_board_init(current_machine);
 
     realtime_init();
-- 
2.7.4