Re: [kvm-ppc-devel] [PATCH 2 of 3] Add PowerPC KVM guest wait handling support

[Hollis Blanchard <hollisb@us.ibm.com>]

On Friday 25 April 2008 00:56:03 Jerone Young wrote:
> This patch handles a guest that is in a wait state. This ensures that the 
guest is not allways eating up 100% cpu when it is idle.
> 
> Signed-off-by: Jerone Young <jyoung5@us.ibm.com>
> 
> diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c
> --- a/arch/powerpc/kvm/emulate.c
> +++ b/arch/powerpc/kvm/emulate.c
> @@ -265,6 +265,11 @@ int kvmppc_emulate_instruction(struct kv
>  		case 146:                                       /* mtmsr */
>  			rs = get_rs(inst);
>  			kvmppc_set_msr(vcpu, vcpu->arch.gpr[rs]);
> +			
> +			/* handle guest vcpu that is in wait state */
> +			if (vcpu->arch.msr & MSR_WE) {
> +				kvm_vcpu_block(vcpu);
> +			}
>  			break;
> 
>  		case 163:                                       /* wrteei */

So if I apply this patch and not #3, the guest will put itself to sleep and 
never wake up? You need to combine patches 2 and 3.

Also, for completeness, you should add the same test to the rfi emulation, 
which could (theoretically) also set MSR[WE].

-- 
Hollis Blanchard
IBM Linux Technology Center

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