That's fair I suppose, the difference being that there's a lot more ways to screw up instruction backdoors and make them extremely visible than RDRAND, where th

That's fair I suppose, the difference being that there's a lot more ways to screw up instruction backdoors and make them extremely visible than RDRAND, where the output is claimed to be unpredictable. In the end it's a defense in depth approach - I simply think the original and default Linux kernel policy of demanding sufficient entropy from other means is preferable from a security perspective. Theodore Tso has some good posts on this on the kernel mailing lists. Due to the way these sources get mixed, it would only improve security to turn this option off.