これなわけですけれども、結局

\--- a/src/storage/storage\_backend\_logical.c
+++ b/src/storage/storage\_backend\_logical.c
@@ -725,8 +725,10 @@ virStorageBackendLogicalCreateVol(virConnectPtr conn,
                                "--name", vol->name,
                                NULL);
     virCommandAddArg(cmd, "-L");
-    if (vol->capacity != vol->allocation) {
-        virCommandAddArgFormat(cmd, "%lluK", VIR\_DIV\_UP(vol->allocation, 1024));
+    if (vol->backingStore.path &&
+        vol->capacity != vol->allocation) {
+        virCommandAddArgFormat(cmd, "%lluK",
+                VIR\_DIV\_UP(vol->allocation ? vol->allocation : 1, 1024));
         virCommandAddArg(cmd, "--virtualsize");
     }
     virCommandAddArgFormat(cmd, "%lluK", VIR\_DIV\_UP(vol->capacity, 1024));

```こうしないと使い物にならない感。fedoraも一緒かな?