vl: Add option to avoid stopping VM upon guest panic

The current default action of pausing a guest after a panic event
is received leaves the responsibility to resume guest execution to the
management layer. The reasons for this behavior are discussed here:
https://lore.kernel.org/qemu-devel/52148F88.5000509@redhat.com/

However, in instances like the case of older guests (Linux and
Windows) using a pvpanic device but missing support for the
PVPANIC_CRASHLOADED event, and Windows guests using the hv-crash
enlightenment, it is desirable to allow the guests to continue
running after sending a PVPANIC_PANICKED event. This allows such
guests to proceed to capture a crash dump and automatically reboot
without intervention of a management layer.

Add an option to avoid stopping a VM after a panic event is received,
by passing:

-action panic=none

in the command line arguments, or during runtime by using an upcoming
QMP command.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>
Message-Id: <1607705564-26264-3-git-send-email-alejandro.j.jimenez@oracle.com>
[Do not fix panic action in the variable, instead modify -no-shutdown. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 14 insertions, 4 deletions

diff --git a/softmmu/runstate.c b/softmmu/runstate.c
index bd0522e..636aab0 100644
--- a/softmmu/runstate.c
+++ b/softmmu/runstate.c
@@ -469,13 +469,23 @@ void qemu_system_guest_panicked(GuestPanicInformation *info)
     if (current_cpu) {
         current_cpu->crash_occurred = true;
     }
-    qapi_event_send_guest_panicked(GUEST_PANIC_ACTION_PAUSE,
-                                   !!info, info);
-    vm_stop(RUN_STATE_GUEST_PANICKED);
-    if (shutdown_action == SHUTDOWN_ACTION_POWEROFF) {
+    /*
+     * TODO:  Currently the available panic actions are: none, pause, and
+     * poweroff, but in principle debug and reset could be supported as well.
+     * Investigate any potential use cases for the unimplemented actions.
+     */
+    if (panic_action == PANIC_ACTION_PAUSE) {
+        qapi_event_send_guest_panicked(GUEST_PANIC_ACTION_PAUSE,
+                                        !!info, info);
+        vm_stop(RUN_STATE_GUEST_PANICKED);
+    } else if (panic_action == PANIC_ACTION_POWEROFF) {
         qapi_event_send_guest_panicked(GUEST_PANIC_ACTION_POWEROFF,
                                        !!info, info);
+        vm_stop(RUN_STATE_GUEST_PANICKED);
         qemu_system_shutdown_request(SHUTDOWN_CAUSE_GUEST_PANIC);
+    } else {
+        qapi_event_send_guest_panicked(GUEST_PANIC_ACTION_RUN,
+                                        !!info, info);
     }
 
     if (info) {