[PATCH 21/26] KVM: PPC: Force enable nap on KVM

[Scott Wood]

On Tue, 17 Aug 2010 15:57:56 +0200
Alexander Graf <agraf at suse.de> wrote:

> There are some heuristics in the PPC power management code that try to find
> out if the particular hardware we're running on supports proper power management
> or just hangs the machine when going into nap mode.
> 
> Since we know that KVM is safe with nap, let's force enable it in the PV code
> once we're certain that we are on a KVM VM.

Could this cause the cache to be flushed unnecessarily on e500?  Where
available, doze would probably be better for signalling the hypervisor
that the guest is idle.

> 
> Signed-off-by: Alexander Graf <agraf at suse.de>
> ---
>  arch/powerpc/kernel/kvm.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/kvm.c b/arch/powerpc/kernel/kvm.c
> index 517da39..95aed6b 100644
> --- a/arch/powerpc/kernel/kvm.c
> +++ b/arch/powerpc/kernel/kvm.c
> @@ -583,6 +583,9 @@ static int __init kvm_guest_init(void)
>  	if (kvm_para_has_feature(KVM_FEATURE_MAGIC_PAGE))
>  		kvm_use_magic_page();
>  
> +	/* Enable napping */
> +	powersave_nap = 1;
> +
>  free_tmp:
>  	kvm_free_tmp();
>