Re: [PATCH 0/7] IBRS patch series

Florian Weimer
2018-01-05T06:07:16Z

* Linus Torvalds:

> On Thu, Jan 4, 2018 at 9:56 AM, Tim Chen <tim.c.chen@linux.intel.com> wrote:
>>
>> Speculation on Skylake and later requires these patches ("dynamic IBRS")
>> be used instead of retpoline[1].
>
> Can somebody explain this part?
>
> I was assuming that retpoline would work around this issue on all uarchs.
>
> This seems to say "retpoline does nothing on Skylake+"

Retpoline also looks incompatible with CET, so future Intel CPUs will
eventually need a different approach anyway.