[PATCH V1 12/32] vl: pause option

[Steve Sistare]

Provide the -pause command-line parameter and the QEMU_PAUSE environment
variable to briefly pause QEMU in main and allow a developer to attach gdb.
Useful when the developer does not invoke QEMU directly, such as when using
libvirt.

Usage:
  qemu -pause <seconds>
  or
  export QEMU_PAUSE=<seconds>

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
---
 qemu-options.hx |  9 +++++++++
 softmmu/vl.c    | 15 ++++++++++++++-
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/qemu-options.hx b/qemu-options.hx
index 708583b..8505cf2 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3668,6 +3668,15 @@ SRST
     option is experimental.
 ERST
 
+DEF("pause", HAS_ARG, QEMU_OPTION_pause, \
+    "-pause secs    Pause for secs seconds on entry to main.\n", QEMU_ARCH_ALL)
+
+SRST
+``--pause secs``
+    Pause for a number of seconds on entry to main.  Useful for attaching
+    a debugger after QEMU has been launched by some other entity.
+ERST
+
 DEF("S", 0, QEMU_OPTION_S, \
     "-S              freeze CPU at startup (use 'c' to start execution)\n",
     QEMU_ARCH_ALL)
diff --git a/softmmu/vl.c b/softmmu/vl.c
index 8478778..951994f 100644
--- a/softmmu/vl.c
+++ b/softmmu/vl.c
@@ -2844,7 +2844,7 @@ static void create_default_memdev(MachineState *ms, const 
char *path)
 
 void qemu_init(int argc, char **argv, char **envp)
 {
-    int i;
+    int i, seconds;
     int snapshot, linux_boot;
     const char *initrd_filename;
     const char *kernel_filename, *kernel_cmdline;
@@ -2882,6 +2882,13 @@ void qemu_init(int argc, char **argv, char **envp)
     QemuPluginList plugin_list = QTAILQ_HEAD_INITIALIZER(plugin_list);
     int mem_prealloc = 0; /* force preallocation of physical target memory */
 
+    if (getenv("QEMU_PAUSE")) {
+        seconds = atoi(getenv("QEMU_PAUSE"));
+        printf("Pausing %d seconds for debugger. QEMU PID is %d\n",
+               seconds, getpid());
+        sleep(seconds);
+    }
+
     os_set_line_buffering();
 
     error_init(argv[0]);
@@ -3204,6 +3211,12 @@ void qemu_init(int argc, char **argv, char **envp)
             case QEMU_OPTION_gdb:
                 add_device_config(DEV_GDB, optarg);
                 break;
+            case QEMU_OPTION_pause:
+                seconds = atoi(optarg);
+                printf("Pausing %d seconds for debugger. QEMU PID is %d\n",
+                            seconds, getpid());
+                sleep(seconds);
+                break;
             case QEMU_OPTION_L:
                 if (is_help_option(optarg)) {
                     list_data_dirs = true;
-- 
1.8.3.1