[PATCH] runstate: allow inmigrate -> debug transition on snapshot restore

[Trieu Huynh <vikingtc4@gmail.com>]

From: Trieu Huynh <vikingtc4@gmail.com>

When a VM snapshot is taken while the guest is paused by a gdbstub
(RUN_STATE_DEBUG), the saved runstate is 'debug', for instance:
  (gdb) monitor info status
  VM status: paused (debug)

On restore, the destination starts in 'inmigrate' and transitions
to the saved runstate, but the 'inmigrate -> debug' transition
was missing from the table, causing an abort:

  $ ./qemu-system-x86_64 -machine pc,accel=kvm:tcg  -m 128M
  -display none -gdb tcp::1235 -incoming "exec:cat /tmp/snap.img"
  > /tmp/qemu-restore.log 2>&1
  Aborted (core dumped)
  $ cat /tmp/qemu-restore.log
  qemu-system-x86_64: invalid runstate transition: 'inmigrate'
  -> 'debug'

Fix it by adding the missing one (Point out by the author
Dustin Spicuzza)

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1231

Signed-off-by: Trieu Huynh <vikingtc4@gmail.com>
---
 system/runstate.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/system/runstate.c b/system/runstate.c
index 2d4e95a216..97a6a1c736 100644
--- a/system/runstate.c
+++ b/system/runstate.c
@@ -94,6 +94,7 @@ static const RunStateTransition runstate_transitions_def[] = {
     { RUN_STATE_INMIGRATE, RUN_STATE_PRELAUNCH },
     { RUN_STATE_INMIGRATE, RUN_STATE_POSTMIGRATE },
     { RUN_STATE_INMIGRATE, RUN_STATE_COLO },
+    { RUN_STATE_INMIGRATE, RUN_STATE_DEBUG },
 
     { RUN_STATE_INTERNAL_ERROR, RUN_STATE_PAUSED },
     { RUN_STATE_INTERNAL_ERROR, RUN_STATE_FINISH_MIGRATE },
-- 
2.43.0