Re: [PATCH 2/4] KVM: PPC: Only WARN on invalid emulation

[Scott Wood <scottwood@freescale.com>]

On 12/18/2012 06:38:41 AM, Alexander Graf wrote:
> When we hit an emulation result that we didn't expect, that is an  
> error,
> but it's nothing that warrants a BUG(), because it can be guest  
> triggered.
> 
> So instead, let's only WARN() the user that this happened.
> 
> Signed-off-by: Alexander Graf <agraf@suse.de>
> ---
>  arch/powerpc/kvm/powerpc.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index be83fca..e2225e5 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -237,7 +237,8 @@ int kvmppc_emulate_mmio(struct kvm_run *run,  
> struct kvm_vcpu *vcpu)
>  		r = RESUME_HOST;
>  		break;
>  	default:
> -		BUG();
> +		WARN_ON(1);
> +		r = RESUME_GUEST;

Do you have a specific way of a guest triggering this in mind, or is it  
just being cautious?  The guest probably shouldn't be allowed to spam  
the kernel log with WARNs either.  Is a traceback even useful here?

-Scott