[PATCH v3 1/1] util/async-teardown: wire up query-command-line-options

[Claudio Imbrenda]

The recently introduced -async-teardown commandline option was not
wired up properly and did not show up in the output of the QMP command
query-command-line-options. This means that libvirt will have no way to
discover whether the feature is supported.

This patch fixes the issue by correctly wiring up the commandline
option so that it appears in the output of query-command-line-options.

Reported-by: Boris Fiuczynski <fiuczy@linux.ibm.com>
Fixes: c891c24b1a ("os-posix: asynchronous teardown for shutdown on Linux")
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
 os-posix.c            | 14 ++++++++++++++
 qemu-options.hx       | 35 ++++++++++++++++++++++++-----------
 util/async-teardown.c | 21 +++++++++++++++++++++
 3 files changed, 59 insertions(+), 11 deletions(-)

diff --git a/os-posix.c b/os-posix.c
index 5adc69f560..48acd7acf5 100644
--- a/os-posix.c
+++ b/os-posix.c
@@ -36,6 +36,8 @@
 #include "qemu/log.h"
 #include "sysemu/runstate.h"
 #include "qemu/cutils.h"
+#include "qemu/config-file.h"
+#include "qemu/option.h"
 
 #ifdef CONFIG_LINUX
 #include <sys/prctl.h>
@@ -132,6 +134,8 @@ static bool os_parse_runas_uid_gid(const char *optarg)
  */
 int os_parse_cmd_args(int index, const char *optarg)
 {
+    QemuOpts *opts;
+
     switch (index) {
     case QEMU_OPTION_runas:
         user_pwd = getpwnam(optarg);
@@ -155,6 +159,16 @@ int os_parse_cmd_args(int index, const char *optarg)
     case QEMU_OPTION_asyncteardown:
         init_async_teardown();
         break;
+    case QEMU_OPTION_teardown:
+        opts = qemu_opts_parse_noisily(qemu_find_opts("teardown"),
+                                       optarg, false);
+        if (!opts) {
+            return -1;
+        }
+        if (qemu_opt_get_bool(opts, "async", false)) {
+            init_async_teardown();
+        }
+        break;
 #endif
     default:
         return -1;
diff --git a/qemu-options.hx b/qemu-options.hx
index d42f60fb91..8582980b12 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -4766,20 +4766,33 @@ DEF("qtest-log", HAS_ARG, QEMU_OPTION_qtest_log, "", 
QEMU_ARCH_ALL)
 DEF("async-teardown", 0, QEMU_OPTION_asyncteardown,
     "-async-teardown enable asynchronous teardown\n",
     QEMU_ARCH_ALL)
-#endif
 SRST
 ``-async-teardown``
-    Enable asynchronous teardown. A new process called "cleanup/<QEMU_PID>"
-    will be created at startup sharing the address space with the main qemu
-    process, using clone. It will wait for the main qemu process to
-    terminate completely, and then exit.
-    This allows qemu to terminate very quickly even if the guest was
-    huge, leaving the teardown of the address space to the cleanup
-    process. Since the cleanup process shares the same cgroups as the
-    main qemu process, accounting is performed correctly. This only
-    works if the cleanup process is not forcefully killed with SIGKILL
-    before the main qemu process has terminated completely.
+    Equivalent to -teardown async=on
+ERST
+
+DEF("teardown", HAS_ARG, QEMU_OPTION_teardown,
+    "-teardown async[=on|off]\n"
+    "                process teardown options\n"
+    "                async=on enables asynchronous teardown\n"
+   ,
+    QEMU_ARCH_ALL)
+SRST
+``-teardown``
+    Set process teardown options.
+
+    ``async=on`` enables asynchronous teardown.  A new process called
+    "cleanup/<QEMU_PID>" will be created at startup sharing the address
+    space with the main qemu process, using clone.  It will wait for the
+    main qemu process to terminate completely, and then exit.  This allows
+    qemu to terminate very quickly even if the guest was huge, leaving the
+    teardown of the address space to the cleanup process.  Since the cleanup
+    process shares the same cgroups as the main qemu process, accounting is
+    performed correctly.  This only works if the cleanup process is not
+    forcefully killed with SIGKILL before the main qemu process has
+    terminated completely.
 ERST
+#endif
 
 DEF("msg", HAS_ARG, QEMU_OPTION_msg,
     "-msg [timestamp[=on|off]][,guest-name=[on|off]]\n"
diff --git a/util/async-teardown.c b/util/async-teardown.c
index 62cdeb0f20..4a5dbce958 100644
--- a/util/async-teardown.c
+++ b/util/async-teardown.c
@@ -12,6 +12,9 @@
  */
 
 #include "qemu/osdep.h"
+#include "qemu/config-file.h"
+#include "qemu/option.h"
+#include "qemu/module.h"
 #include <dirent.h>
 #include <sys/prctl.h>
 #include <sched.h>
@@ -144,3 +147,21 @@ void init_async_teardown(void)
     clone(async_teardown_fn, new_stack_for_clone(), CLONE_VM, NULL);
     sigprocmask(SIG_SETMASK, &old_signals, NULL);
 }
+
+static QemuOptsList qemu_teardown_opts = {
+    .name = "teardown",
+    .head = QTAILQ_HEAD_INITIALIZER(qemu_teardown_opts.head),
+    .desc = {
+        {
+            .name = "async",
+            .type = QEMU_OPT_BOOL,
+        },
+        { /* end of list */ }
+    },
+};
+
+static void register_teardown(void)
+{
+    qemu_add_opts(&qemu_teardown_opts);
+}
+opts_init(register_teardown);
-- 
2.39.2