Re: [PATCH 00/11] (v2) Mitigation against unsafe data speculation (CVE-2017-5753)

[Jeff Law <law at redhat dot com>]

On 07/27/2018 01:48 PM, John David Anglin wrote:
> On 2018-07-27 5:37 AM, Richard Earnshaw wrote:
>> Port Maintainers: You need to decide what action is required for your
>> port to handle speculative execution, even if that action is to use
>> the trivial no-speculation on this architecture.  You must also
>> consider whether or not a furture implementation of your architecture
>> might need to deal with this in making that decision.
> On hppa, I think we should go with the hook that assumes there is no
> speculative execution.
> 
> Nominally, there is branch prediction and speculative execution; but the
> spectre test program
> was not able to successfully access memory on my rp3440.
> 
> As far as I know, the details of speculative execution on PA-RISC are
> not public.  Jeff would know
It's been eons.   I think there's enough building blocks on the PA to
mount a spectre v1 attack.  They've got branch prediction with varying
degress of speculative execution, caches and user accessable cycle timers.

There's varying degrees of out of order execution all the way back in
the PA7xxx processors (hit-under-miss) to full o-o-o execution in the
PA8xxx series (including the PA8900 that's in the rp3440).

I suspect that given enough time we could figure out why the test didn't
indicate spectre v1 vulnerability on your system and twiddle it, but
given it's a dead processor, I doubt it's worth the effort.

jeff