qemu_snapshot: revert: always error out if VM XML is missing

The support to revert snapshots was introduced in libvirt 0.8.0 but
saving the whole VM XML was implemented later in libvirt 0.9.5.

That is more then 10 years ago so we can safely assume that nobody will
try reverting to snapshot created by that old libvirt. In the unlikely
scenario where someone would actually did it we would simply error out.

Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>

diff --git a/src/qemu/qemu_snapshot.c b/src/qemu/qemu_snapshot.c
index bd58d500ebf11f09ff886848d12bef74f6568418..827b932b6013478233404b9814d1bc01f4e100aa 100644 (file)
--- a/src/qemu/qemu_snapshot.c
+++ b/src/qemu/qemu_snapshot.c
@@ -1907,13 +1907,14 @@ qemuSnapshotRevert(virDomainObj *vm,
         goto endjob;
     }
 
+    if (!snap->def->dom) {
+        virReportError(VIR_ERR_SNAPSHOT_REVERT_RISKY,
+                       _("snapshot '%s' lacks domain '%s' rollback info"),
+                       snap->def->name, vm->def->name);
+        goto endjob;
+    }
+
     if (!(flags & VIR_DOMAIN_SNAPSHOT_REVERT_FORCE)) {
-        if (!snap->def->dom) {
-            virReportError(VIR_ERR_SNAPSHOT_REVERT_RISKY,
-                           _("snapshot '%s' lacks domain '%s' rollback info"),
-                           snap->def->name, vm->def->name);
-            goto endjob;
-        }
         if (virDomainObjIsActive(vm) &&
             !(snapdef->state == VIR_DOMAIN_SNAPSHOT_RUNNING ||
               snapdef->state == VIR_DOMAIN_SNAPSHOT_PAUSED) &&
@@ -1934,16 +1935,14 @@ qemuSnapshotRevert(virDomainObj *vm,
         }
     }
 
-    if (snap->def->dom) {
-        config = virDomainDefCopy(snap->def->dom,
-                                  driver->xmlopt, priv->qemuCaps, true);
-        if (!config)
-            goto endjob;
+    config = virDomainDefCopy(snap->def->dom,
+                              driver->xmlopt, priv->qemuCaps, true);
+    if (!config)
+        goto endjob;
 
-        if (STRNEQ(config->name, vm->def->name)) {
-            VIR_FREE(config->name);
-            config->name = g_strdup(vm->def->name);
-        }
+    if (STRNEQ(config->name, vm->def->name)) {
+        VIR_FREE(config->name);
+        config->name = g_strdup(vm->def->name);
     }
 
     if (snap->def->inactiveDom) {
@@ -1991,61 +1990,59 @@ qemuSnapshotRevert(virDomainObj *vm,
             /* Transitions 5, 6, 8, 9 */
             /* Check for ABI compatibility. We need to do this check against
              * the migratable XML or it will always fail otherwise */
-            if (config) {
-                bool compatible;
-
-                /* Replace the CPU in config and put the original one in priv
-                 * once we're done. When we have the updated CPU def in the
-                 * cookie, we don't want to replace the CPU in migratable def
-                 * when doing ABI checks to make sure the current CPU exactly
-                 * matches the one used at the time the snapshot was taken.
-                 */
-                if (cookie && cookie->cpu && config->cpu) {
-                    origCPU = config->cpu;
-                    if (!(config->cpu = virCPUDefCopy(cookie->cpu)))
-                        goto endjob;
-
-                    compatible = qemuDomainDefCheckABIStability(driver,
-                                                                priv->qemuCaps,
-                                                                vm->def,
-                                                                config);
-                } else {
-                    compatible = qemuDomainCheckABIStability(driver, vm, config);
-                }
+            bool compatible;
 
-                /* If using VM GenID, there is no way currently to change
-                 * the genid for the running guest, so set an error,
-                 * mark as incompatible, and don't allow change of genid
-                 * if the revert force flag would start the guest again. */
-                if (compatible && config->genidRequested) {
-                    virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
-                                   _("domain genid update requires restart"));
-                    compatible = false;
-                    start_flags &= ~VIR_QEMU_PROCESS_START_GEN_VMID;
-                }
+            /* Replace the CPU in config and put the original one in priv
+             * once we're done. When we have the updated CPU def in the
+             * cookie, we don't want to replace the CPU in migratable def
+             * when doing ABI checks to make sure the current CPU exactly
+             * matches the one used at the time the snapshot was taken.
+             */
+            if (cookie && cookie->cpu && config->cpu) {
+                origCPU = config->cpu;
+                if (!(config->cpu = virCPUDefCopy(cookie->cpu)))
+                    goto endjob;
 
-                if (!compatible) {
-                    virErrorPtr err = virGetLastError();
-
-                    if (!(flags & VIR_DOMAIN_SNAPSHOT_REVERT_FORCE)) {
-                        /* Re-spawn error using correct category. */
-                        if (err->code == VIR_ERR_CONFIG_UNSUPPORTED)
-                            virReportError(VIR_ERR_SNAPSHOT_REVERT_RISKY, "%s",
-                                           err->str2);
-                        goto endjob;
-                    }
-                    virResetError(err);
-                    qemuProcessStop(driver, vm,
-                                    VIR_DOMAIN_SHUTOFF_FROM_SNAPSHOT,
-                                    QEMU_ASYNC_JOB_START, 0);
-                    virDomainAuditStop(vm, "from-snapshot");
-                    detail = VIR_DOMAIN_EVENT_STOPPED_FROM_SNAPSHOT;
-                    event = virDomainEventLifecycleNewFromObj(vm,
-                                                     VIR_DOMAIN_EVENT_STOPPED,
-                                                     detail);
-                    virObjectEventStateQueue(driver->domainEventState, event);
-                    goto load;
+                compatible = qemuDomainDefCheckABIStability(driver,
+                                                            priv->qemuCaps,
+                                                            vm->def,
+                                                            config);
+            } else {
+                compatible = qemuDomainCheckABIStability(driver, vm, config);
+            }
+
+            /* If using VM GenID, there is no way currently to change
+             * the genid for the running guest, so set an error,
+             * mark as incompatible, and don't allow change of genid
+             * if the revert force flag would start the guest again. */
+            if (compatible && config->genidRequested) {
+                virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                               _("domain genid update requires restart"));
+                compatible = false;
+                start_flags &= ~VIR_QEMU_PROCESS_START_GEN_VMID;
+            }
+
+            if (!compatible) {
+                virErrorPtr err = virGetLastError();
+
+                if (!(flags & VIR_DOMAIN_SNAPSHOT_REVERT_FORCE)) {
+                    /* Re-spawn error using correct category. */
+                    if (err->code == VIR_ERR_CONFIG_UNSUPPORTED)
+                        virReportError(VIR_ERR_SNAPSHOT_REVERT_RISKY, "%s",
+                                       err->str2);
+                    goto endjob;
                 }
+                virResetError(err);
+                qemuProcessStop(driver, vm,
+                                VIR_DOMAIN_SHUTOFF_FROM_SNAPSHOT,
+                                QEMU_ASYNC_JOB_START, 0);
+                virDomainAuditStop(vm, "from-snapshot");
+                detail = VIR_DOMAIN_EVENT_STOPPED_FROM_SNAPSHOT;
+                event = virDomainEventLifecycleNewFromObj(vm,
+                                                 VIR_DOMAIN_EVENT_STOPPED,
+                                                 detail);
+                virObjectEventStateQueue(driver->domainEventState, event);
+                goto load;
             }
 
             if (virDomainObjGetState(vm, NULL) == VIR_DOMAIN_RUNNING) {
@@ -2072,10 +2069,9 @@ qemuSnapshotRevert(virDomainObj *vm,
                  * failed loadvm attempt? */
                 goto endjob;
             }
-            if (config) {
-                virCPUDefFree(priv->origCPU);
-                priv->origCPU = g_steal_pointer(&origCPU);
-            }
+
+            virCPUDefFree(priv->origCPU);
+            priv->origCPU = g_steal_pointer(&origCPU);
 
             if (cookie && !cookie->slirpHelper)
                 priv->disableSlirp = true;
@@ -2096,10 +2092,8 @@ qemuSnapshotRevert(virDomainObj *vm,
                 defined = true;
             }
 
-            if (config) {
-                virDomainObjAssignDef(vm, config, true, NULL);
-                config = NULL;
-            }
+            virDomainObjAssignDef(vm, config, true, NULL);
+            config = NULL;
 
             /* No cookie means libvirt which saved the domain was too old to
              * mess up the CPU definitions.