virDomainMemoryDefValidate: Skip the same device on validation on memory device update

In my recent commit of v9.8.0-rc1~7 I've introduced validation
wrt other memory devices. And mostly works, except when doing
memory device update ('virsh update-memory-device') because then
@mem is just parsed <memory/> device XML and thus its pointer is
not in the vm->def->mem, yet. Thus my algorithm which skips over
the same entry fails. Fortunately, we require full device XML on
device update and thus we can use device address and aliases to
detect duplicity.

Fixes: 3fd64fb0e236fc80ffa2cc977c0d471f11fc39bf
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>

src/conf/domain_validate.c

@@ -2387,6 +2387,21 @@ virDomainMemoryDefValidate(const virDomainMemoryDef *mem,
         if (other == mem)
             continue;
 
+        /* In case we're updating an existing memory device (e.g. virtio-mem),
+         * then pointers will be different. But addresses and aliases are the
+         * same. However, STREQ_NULLABLE() returns true if both strings are
+         * NULL which is not what we want. */
+        if (virDomainDeviceInfoAddressIsEqual(&other->info,
+                                              &mem->info)) {
+            continue;
+        }
+
+        if (mem->info.alias &&
+            STREQ_NULLABLE(other->info.alias,
+                           mem->info.alias)) {
+            continue;
+        }
+
         switch (other->model) {
         case VIR_DOMAIN_MEMORY_MODEL_NONE:
         case VIR_DOMAIN_MEMORY_MODEL_DIMM: