From: Greg Kurz <groug@kaod.org>

We must not call spapr_drc_detach() on a detached DRC otherwise bad things
can happen, ie. QEMU hangs or crashes. This is easily demonstrated with
a CPU hotplug/unplug loop using QMP.

Signed-off-by: Greg Kurz <groug@kaod.org>
Message-Id: <157185826035.3073024.1664101000438499392.stgit@bahia.lan>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 hw/ppc/spapr.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index f9410d390a..94f9d27096 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -3741,9 +3741,10 @@ void spapr_core_unplug_request(HotplugHandler *hotplug_dev, DeviceState *dev,
                           spapr_vcpu_id(spapr, cc->core_id));
     g_assert(drc);
 
-    spapr_drc_detach(drc);
-
-    spapr_hotplug_req_remove_by_index(drc);
+    if (!spapr_drc_unplug_requested(drc)) {
+        spapr_drc_detach(drc);
+        spapr_hotplug_req_remove_by_index(drc);
+    }
 }
 
 int spapr_core_dt_populate(SpaprDrc *drc, SpaprMachineState *spapr,
-- 
2.21.0