Also filter out non-migratable features out of host-passthrough

Commit de0aeafe filtered them out from the host-model features,
to allow host-model to be migratable by default.

Even though they are not passed to QEMU for host-passthrough,
(and not enabled by default) filter them out too
so the user does not think the domain has them.

https://bugzilla.redhat.com/show_bug.cgi?id=1147584

src/cpu/cpu_x86.c

@@ -2068,7 +2068,8 @@ x86UpdateCustom(virCPUDefPtr guest,
 
 static int
 x86UpdateHostModel(virCPUDefPtr guest,
-                   const virCPUDef *host)
+                   const virCPUDef *host,
+                   bool passthrough)
 {
     virCPUDefPtr oldguest = NULL;
     const struct x86_map *map;
@@ -2076,8 +2077,6 @@ x86UpdateHostModel(virCPUDefPtr guest,
     size_t i;
     int ret = -1;
 
-    guest->match = VIR_CPU_MATCH_EXACT;
-
     if (!(map = virCPUx86GetMap()))
         goto cleanup;
 
@@ -2100,8 +2099,7 @@ x86UpdateHostModel(virCPUDefPtr guest,
             }
         }
     }
-
-    for (i = 0; i < oldguest->nfeatures; i++) {
+    for (i = 0; !passthrough && i < oldguest->nfeatures; i++) {
         if (virCPUDefUpdateFeature(guest,
                                    oldguest->features[i].name,
                                    oldguest->features[i].policy) < 0)
@@ -2125,12 +2123,12 @@ x86Update(virCPUDefPtr guest,
         return x86UpdateCustom(guest, host);
 
     case VIR_CPU_MODE_HOST_MODEL:
-        return x86UpdateHostModel(guest, host);
+        guest->match = VIR_CPU_MATCH_EXACT;
+        return x86UpdateHostModel(guest, host, false);
 
     case VIR_CPU_MODE_HOST_PASSTHROUGH:
         guest->match = VIR_CPU_MATCH_MINIMUM;
-        virCPUDefFreeModel(guest);
-        return virCPUDefCopyModel(guest, host, true);
+        return x86UpdateHostModel(guest, host, true);
 
     case VIR_CPU_MODE_LAST:
         break;