[PATCH 1/1] vl: Add -no-panicstop option

[Alejandro Jimenez <alejandro.j.jimenez@oracle.com>]

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.

Signed-off-by: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>
Reviewed-by: Mark Kanda <mark.kanda@oracle.com>
---
 qemu-options.hx | 11 +++++++++++
 softmmu/vl.c    | 17 ++++++++++++++---
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/qemu-options.hx b/qemu-options.hx
index 3564c23..cbaf947 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3882,6 +3882,17 @@ SRST
     specified domain id (XEN only).
 ERST
 
+DEF("no-panicstop", 0, QEMU_OPTION_no_panicstop, \
+    "-no-panicstop	do not stop the VM on panic\n", QEMU_ARCH_ALL)
+SRST
+``-no-panicstop``
+    Don't stop the VM when a panic event is received. This allows older guests
+    using a pvpanic device but without support for the PVPANIC_CRASHLOADED
+    event, and Windows guests using the hv-crash enlightenment to continue
+    running and capture a crash dump or reboot without intervention of a
+    management layer.
+ERST
+
 DEF("no-reboot", 0, QEMU_OPTION_no_reboot, \
     "-no-reboot      exit instead of rebooting\n", QEMU_ARCH_ALL)
 SRST
diff --git a/softmmu/vl.c b/softmmu/vl.c
index 22bc570..a939b18 100644
--- a/softmmu/vl.c
+++ b/softmmu/vl.c
@@ -147,6 +147,7 @@ int win2k_install_hack = 0;
 int singlestep = 0;
 int no_hpet = 0;
 int fd_bootchk = 1;
+static int no_panicstop;
 static int no_reboot;
 int no_shutdown = 0;
 int graphic_rotate = 0;
@@ -1431,9 +1432,16 @@ 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 (no_panicstop) {
+        qapi_event_send_guest_panicked(GUEST_PANIC_ACTION_RUN,
+                                        !!info, info);
+    } else {
+        qapi_event_send_guest_panicked(GUEST_PANIC_ACTION_PAUSE,
+                                        !!info, info);
+        vm_stop(RUN_STATE_GUEST_PANICKED);
+    }
+
     if (!no_shutdown) {
         qapi_event_send_guest_panicked(GUEST_PANIC_ACTION_POWEROFF,
                                        !!info, info);
@@ -3558,6 +3566,9 @@ void qemu_init(int argc, char **argv, char **envp)
             case QEMU_OPTION_no_hpet:
                 no_hpet = 1;
                 break;
+            case QEMU_OPTION_no_panicstop:
+                no_panicstop = 1;
+                break;
             case QEMU_OPTION_no_reboot:
                 no_reboot = 1;
                 break;
-- 
1.8.3.1