[Qemu-devel] [PATCH] vl: don't use RUN_STATE_PRECONFIG unless --preconfig is given

["Daniel P. Berrangé" <berrange@redhat.com>]

The RUN_STATE_PRECONFIG state is not supposed to be reachable unless the
--preconfig argument is given to QEMU, but when it was introduced in:

  commit 047f7038f586d2150f16c6d9ba9cfd0479f0f6ac
  Author: Igor Mammedov <imammedo@redhat.com>
  Date:   Fri May 11 19:24:43 2018 +0200

    cli: add --preconfig option

The global 'current_run_state' variable was changed to have an initial
value of RUN_STATE_PRECONFIG regardless of whether --preconfig is given.

It then relies on the main loop to toggle it back to RUN_STATE_PRELAUNCH
when --preconfig is not given. This is racy because it means that there
is a window where QEMU is in RUN_STATE_PRECONFIG despite --preconfig not
being given. This can be seen with the failure:

  $ echo | x86_64-softmmu/qemu-system-x86_64 -monitor stdio
  QEMU 2.12.50 monitor - type 'help' for more information
  (qemu)
  HMP not available in preconfig state, use QMP instead

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 vl.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/vl.c b/vl.c
index 06031715ac..f776d65801 100644
--- a/vl.c
+++ b/vl.c
@@ -561,7 +561,7 @@ static int default_driver_check(void *opaque, QemuOpts *opts, Error **errp)
 /***********************************************************/
 /* QEMU state */
 
-static RunState current_run_state = RUN_STATE_PRECONFIG;
+static RunState current_run_state = RUN_STATE_PRELAUNCH;
 
 /* We use RUN_STATE__MAX but any invalid value will do */
 static RunState vmstop_requested = RUN_STATE__MAX;
@@ -3572,6 +3572,7 @@ int main(int argc, char **argv, char **envp)
                 }
                 break;
             case QEMU_OPTION_preconfig:
+                current_run_state = RUN_STATE_PRECONFIG;
                 preconfig_exit_requested = false;
                 break;
             case QEMU_OPTION_enable_kvm:
-- 
2.17.0