From bfaf4b3a5bb4bc74d089d5230cdd1e83622f9239 Mon Sep 17 00:00:00 2001
Message-Id: <bfaf4b3a5bb4bc74d089d5230cdd1e83622f9239.1379597659.git.jdenemar@redhat.com>
From: Peter Krempa <pkrempa@redhat.com>
Date: Tue, 17 Sep 2013 10:19:32 +0200
Subject: [PATCH] qemu: Fix checking of ABI stability when restoring external
 checkpoints

External checkpoints have a bug in the implementation where they use the
normal definition instead of the "migratable" one. This causes errors
when the snapshot is being reverted using the workaround method via
qemuDomainRestoreFlags() with a custom XML. This issue was introduced
when commit 07966f6a8b5ccb5bb4c716b25deb8ba2e572cc67 changed the code to
compare "migratable" XMLs from the user as we should have used
migratable in the image too.

This patch adds a compatibility layer, so that fixing the snapshot code
won't make existing snapshots fail to load.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1008340
(cherry picked from commit 59898a88ce8431bd3ea249b8789edc2ef9985827)
---
 src/qemu/qemu_driver.c | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 86a1d6d..9b9732d 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -5312,14 +5312,31 @@ qemuDomainSaveImageOpen(virQEMUDriverPtr driver,
             goto error;
 
         newdef = qemuDomainDefCopy(driver, def2, VIR_DOMAIN_XML_MIGRATABLE);
-        virDomainDefFree(def2);
-        if (!newdef)
+        if (!newdef) {
+            virDomainDefFree(def2);
             goto error;
+        }
 
         if (!virDomainDefCheckABIStability(def, newdef)) {
             virDomainDefFree(newdef);
-            goto error;
+            virResetLastError();
+
+            /* Due to a bug in older version of external snapshot creation
+             * code, the XML saved in the save image was not a migratable
+             * XML. To ensure backwards compatibility with the change of the
+             * saved XML type, we need to check the ABI compatibility against
+             * the user provided XML if the check against the migratable XML
+             * fails. Snapshots created prior to v1.1.3 have this issue. */
+            if (!virDomainDefCheckABIStability(def, def2)) {
+                virDomainDefFree(def2);
+                goto error;
+            }
+
+            /* use the user provided XML */
+            newdef = def2;
+            def2 = NULL;
         }
+
         virDomainDefFree(def);
         def = newdef;
     }
-- 
1.8.3.2