[RFC PATCH] powerpc/powernv: Provide a way to force a core into SMT4 mode

[Nicholas Piggin]

On Thu, 25 Jan 2018 16:05:12 +1100
Paul Mackerras <paulus at ozlabs.org> wrote:

> POWER9 processors up to and including "Nimbus" v2.2 have hardware
> bugs relating to transactional memory and thread reconfiguration.
> One of these bugs has a workaround which is to get the core into
> SMT4 state temporarily.  This workaround is only needed when
> running bare-metal.

How often will this be triggered, in practice? If it's infrequent,
then would it be better to just do a smp_call_function on siblings
and get them all spinning there? I'm looking sadly at the added
sync...

Thanks,
Nick