
Ask HN: Is the Mill CPU Vulnerable to Spectre? - runeks
With both x86 and ARM being vulnerable to Spectre, it would be interesting to know where the novel Mill CPU architecture stands in this space.<p>And, if Mill isn’t vulnerable, why is this the case?<p>To me, it seems like a good argument for the Mill architecture if the designers were able to avoid a bug they didn’t even know existed.
======
jecel
Note that these problems are not inherent to out of order implementations. Dan
Ingalls (who first implemented Smalltalk) said "you can cheat as long as you
don't get caught". When speculation fails, all side effects are rolled back in
x86 and ARM processors except reads to the cache since these were considered
harmless. Writes to the cache are already rolled back so not doing so for
reads just saves circuit complexity. There is no reason why this can't be
added to the next chip designs, though nothing can be done about what is
already out there.

As for the Mill, it has enough differences that these attacks wouldn't work on
it. Just the separation between protection and translation, for example, would
stop Meltdown in its tracks.

~~~
willvarfar
It is flawed to 'roll back' changes. Instead, those changes have to have never
existed. Otherwise, there is a short window of time when the cache-visible
side-effects have happened, and haven't been rolled back yet, and the attacker
can see them (due to preemption, due to hyperthreading, due to running in
another core etc).

------
willvarfar
(team Mill)

The Mill is not vulnerable to Spectre and Meltdown.

We have a paper that will go public shortly explaining how these attacks apply
to in-order architectures that do support speculation, and how the Mill avoids
them.

Watch this space :)

~~~
gravypod
Will you be sticking to the timeline mentioned in this post:
[https://millcomputing.com/topic/meltdown-and-
spectre/#post-3...](https://millcomputing.com/topic/meltdown-and-
spectre/#post-3168)

Will you be posting this paper on HN? I'm sure a large portion of the
community here would be interested in it.

------
sabauma
There has been some discussion of Meltdown and Spectre on the Mill forums:

[https://millcomputing.com/topic/meltdown-and-
spectre/](https://millcomputing.com/topic/meltdown-and-spectre/)

------
danharaj
It doesn't physically exist, so no.

