We have caught this in some prod environments, where prctl is forbidden by the sandboxing mechanism. This fails the JVM, because we have the following code to check for SVE vector length:

int VM_Version::get_current_sve_vector_length() {
  assert(VM_Version::supports_sve(), "should not call this");
  return prctl(PR_SVE_GET_VL);
}

That code returns `-1` when `prctl` is disallowed, which JVM then blindly interprets as vector length:

  if (UseSVE > 0) {
    _initial_sve_vector_length = get_current_sve_vector_length();
  }

...leading to SIGILL.

Workaround: -XX:UseSVE=0