migration: Hack to maintain backwards compatibility for ppc

Current code does:
- register pre_2_10_vmstate_dummy_icp with "icp/server" and instance
  dependinfg on cpu number
- for newer machines, it register vmstate_icp with "icp/server" name
  and instance 0
- now it unregisters "icp/server" for the 1st instance.

This is wrong at many levels:
- we shouldn't have two VMSTATEDescriptions with the same name
- In case this is the only solution that we can came with, it needs to
  be:
  * register pre_2_10_vmstate_dummy_icp
  * unregister pre_2_10_vmstate_dummy_icp
  * register real vmstate_icp

Created vmstate_replace_hack_for_ppc() with warnings left and right
that it is a hack.

CC: Cedric Le Goater <clg@kaod.org>
CC: Daniel Henrique Barboza <danielhb413@gmail.com>
CC: David Gibson <david@gibson.dropbear.id.au>
CC: Greg Kurz <groug@kaod.org>

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231020090731.28701-8-quintela@redhat.com>

1 files changed, 16 insertions, 2 deletions

diff --git a/hw/intc/xics.c b/hw/intc/xics.c
index c7f8abd71e..c77e986136 100644
--- a/hw/intc/xics.c
+++ b/hw/intc/xics.c
@@ -335,8 +335,22 @@ static void icp_realize(DeviceState *dev, Error **errp)
             return;
         }
     }
-
-    vmstate_register(NULL, icp->cs->cpu_index, &vmstate_icp_server, icp);
+    /*
+     * The way that pre_2_10_icp is handling is really, really hacky.
+     * We used to have here this call:
+     *
+     * vmstate_register(NULL, icp->cs->cpu_index, &vmstate_icp_server, icp);
+     *
+     * But we were doing:
+     *     pre_2_10_vmstate_register_dummy_icp()
+     *     this vmstate_register()
+     *     pre_2_10_vmstate_unregister_dummy_icp()
+     *
+     * So for a short amount of time we had to vmstate entries with
+     * the same name.  This fixes it.
+     */
+    vmstate_replace_hack_for_ppc(NULL, icp->cs->cpu_index,
+                                 &vmstate_icp_server, icp);
 }
 
 static void icp_unrealize(DeviceState *dev)