Re: [PATCH V5 08/25] vl: add helper to request re-exec

[Steven Sistare]

On 7/8/2021 10:31 AM, Marc-André Lureau wrote:
> Hi
> 
> On Wed, Jul 7, 2021 at 9:46 PM Steve Sistare <steven.sistare@oracle.com 
> <mailto:steven.sistare@oracle.com>> wrote:
> 
>     Add a qemu_system_exec_request() hook that causes the main loop to exit 
> and
>     re-exec qemu using the specified arguments.
> 
> 
> I assume it works ok with -sandbox on,spawn=allow ?

Yes, I tested that.

Will do for all below.

- Steve

>     Signed-off-by: Steve Sistare <steven.sistare@oracle.com 
> <mailto:steven.sistare@oracle.com>>
>     ---
>      include/sysemu/runstate.h |  1 +
>      softmmu/runstate.c        | 37 +++++++++++++++++++++++++++++++++++++
>      2 files changed, 38 insertions(+)
> 
>     diff --git a/include/sysemu/runstate.h b/include/sysemu/runstate.h
>     index ed4b735..e1ae7e5 100644
>     --- a/include/sysemu/runstate.h
>     +++ b/include/sysemu/runstate.h
>     @@ -57,6 +57,7 @@ void qemu_system_wakeup_enable(WakeupReason reason, 
> bool enabled);
>      void qemu_register_wakeup_notifier(Notifier *notifier);
>      void qemu_register_wakeup_support(void);
>      void qemu_system_shutdown_request(ShutdownCause reason);
>     +void qemu_system_exec_request(strList *args);
>      void qemu_system_powerdown_request(void);
>      void qemu_register_powerdown_notifier(Notifier *notifier);
>      void qemu_register_shutdown_notifier(Notifier *notifier);
>     diff --git a/softmmu/runstate.c b/softmmu/runstate.c
>     index 7fe4967..8474a01 100644
>     --- a/softmmu/runstate.c
>     +++ b/softmmu/runstate.c
>     @@ -355,6 +355,7 @@ static NotifierList wakeup_notifiers =
>      static NotifierList shutdown_notifiers =
>          NOTIFIER_LIST_INITIALIZER(shutdown_notifiers);
>      static uint32_t wakeup_reason_mask = ~(1 << QEMU_WAKEUP_REASON_NONE);
>     +static char **exec_argv;
> 
>      ShutdownCause qemu_shutdown_requested_get(void)
>      {
>     @@ -371,6 +372,11 @@ static int qemu_shutdown_requested(void)
>          return qatomic_xchg(&shutdown_requested, SHUTDOWN_CAUSE_NONE);
>      }
> 
>     +static int qemu_exec_requested(void)
>     +{
>     +    return exec_argv != NULL;
>     +}
>     +
>      static void qemu_kill_report(void)
>      {
>          if (!qtest_driver() && shutdown_signal) {
>     @@ -645,6 +651,32 @@ void qemu_system_shutdown_request(ShutdownCause 
> reason)
>          qemu_notify_event();
>      }
> 
>     +static char **make_argv(strList *args)
> 
> 
> I'd suggest making it a generic strv_from_strList() function. Take const as 
> argument too.
>  
> 
>     +{
>     +    strList *arg;
>     +    char **argv;
>     +    int n = 1, i = 0;
>     +
>     +    for (arg = args; arg != NULL; arg = arg->next) {
>     +        n++;
>     +    }
> 
> 
> We could use a QAPI_LIST_LENGTH() in qapi/util.h
> 
>     +
>     +    argv = g_malloc(n * sizeof(char *));
>     +    for (arg = args; arg != NULL; arg = arg->next) {
>     +        argv[i++] = g_strdup(arg->value);
>     +    }
>     +    argv[i] = NULL;
>     +
>     +    return argv;
>     +}
>     +
>     +void qemu_system_exec_request(strList *args)
> 
> 
> const args, and documentation could help.
> 
>     +{
>     +    exec_argv = make_argv(args);
>     +    shutdown_requested = 1;
>     +    qemu_notify_event();
>     +}
>     +
>      static void qemu_system_powerdown(void)
>      {
>          qapi_event_send_powerdown();
>     @@ -693,6 +725,11 @@ static bool main_loop_should_exit(void)
>          }
>          request = qemu_shutdown_requested();
>          if (request) {
>     +
>     +        if (qemu_exec_requested()) {
>     +            execvp(exec_argv[0], exec_argv);
>     +            error_setg_errno(&error_fatal, errno, "execvp failed");
> 
> 
> Can this be handled more gracefully instead?
> 
> g_strfreev the argv and report an error?
>  
> 
>     +        }
>              qemu_kill_report();
>              qemu_system_shutdown(request);
>              if (shutdown_action == SHUTDOWN_ACTION_PAUSE) {
>     -- 
>     1.8.3.1
> 
> 
> 
> 
> -- 
> Marc-André Lureau