The "special register buffer data sampling" hardware vulnerability

I spent a while wondering *why* there's a flag to do this on these specific instructions and the best answer I found was to allow the host to provide the same random numbers to multiple guests in order to allow "best out of three" type validation without having to rewrite code that uses rdrand. Which doesn't seem like a great answer tbf (why not just use a paravirt rng?), but it worked out fortunately for this case.