spapr: Fix pre-2.10 dummy ICP hack

This hack registers dummy VMState entries of ICPs in order to
support migration of old pseries machine types that used to
create all smp.max_cpus possible ICPs at machine init.

Part of the work is to unregister the dummy entries when plugging
an actual vCPU core, and to register them back when unplugging the
core. The code that unregisters the dummy ICPs in spapr_core_plug()
is misplaced: if ppc_set_compat() fails afterwards, the hotplug
operation will be cancelled and the dummy ICPs won't be registered
back since the unplug handler isn't called.

Unregister the dummy ICPs at the end of spapr_core_plug().

Signed-off-by: Greg Kurz <groug@kaod.org>
Message-Id: <20201201113728.885700-2-groug@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index d51c55028873a8781cb389c5ad2f0d67d9f5d6d6..5fbae8addac79a172bc80af22ceb5ce68580730d 100644 (file)
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -3782,13 +3782,6 @@ static void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
 
     core_slot->cpu = OBJECT(dev);
 
-    if (smc->pre_2_10_has_unused_icps) {
-        for (i = 0; i < cc->nr_threads; i++) {
-            cs = CPU(core->threads[i]);
-            pre_2_10_vmstate_unregister_dummy_icp(cs->cpu_index);
-        }
-    }
-
     /*
      * Set compatibility mode to match the boot CPU, which was either set
      * by the machine reset code or by CAS.
@@ -3802,6 +3795,13 @@ static void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
             }
         }
     }
+
+    if (smc->pre_2_10_has_unused_icps) {
+        for (i = 0; i < cc->nr_threads; i++) {
+            cs = CPU(core->threads[i]);
+            pre_2_10_vmstate_unregister_dummy_icp(cs->cpu_index);
+        }
+    }
 }
 
 static void spapr_core_pre_plug(HotplugHandler *hotplug_dev, DeviceState *dev,