String buildLegacyOptions() {
            String jvmOptions = null;
            if (nodesElement.hasAttribute(VespaDomBuilder.JVM_OPTIONS)) {
                jvmOptions = nodesElement.getAttribute(VespaDomBuilder.JVM_OPTIONS);
                if (! jvmOptions.isEmpty())
                    logger.logApplicationPackage(WARNING, "'jvm-options' is deprecated and will be removed in Vespa 9." +
                            " Please merge 'jvm-options' into 'options' or 'gc-options' in 'jvm' element." +
                            " See https://docs.vespa.ai/en/reference/services-container.html#jvm");
            }

            validateJvmOptions(jvmOptions);

            return jvmOptions;
        }
Validates JVM options and logs a warning or fails deployment (depending on feature flag)
if anyone of them has invalid syntax or is an option that is unsupported for the running system.
config-model/src/main/java/com/yahoo/vespa/model/container/xml/ContainerModelBuilder.java