[PATCH v3 1/4] KVM: PPC: Book3S HV: POWER9 does not require secondary thread management

[Paul Mackerras]

On Fri, Aug 25, 2017 at 02:30:33PM +1000, Nicholas Piggin wrote:
> POWER9 CPUs have independent MMU contexts per thread, so KVM does not
> need to quiesce secondary threads, so the hwthread_req/hwthread_state
> protocol does not have to be used. So patch it away on POWER9, and patch
> away the branch from the Linux idle wakeup to kvm_start_guest that is
> never used.
> 
> Add a warning and error out of kvmppc_grab_hwthread in case it is ever
> called on POWER9.
> 
> This avoids a hwsync in the idle wakeup path on POWER9.
> 
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>

Some of the feature sections seem a little unnecessary except for
documentation purposes (e.g. the second one added after the
kvm_no_guest label), but they won't actually hurt, so:

Acked-by: Paul Mackerras <paulus at ozlabs.org>