Re: [PATCH 3/3] KVM: SVM: enable LBRV virtualization

[Avi Kivity <avi@qumranet.com>]

Joerg Roedel wrote:
> @@ -1224,6 +1261,15 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, unsigned ecx, u64 data)
>  		if (data != 0)
>  			goto unhandled;
>  		break;
> +	case MSR_IA32_DEBUGCTLMSR:
> +		svm->vmcb->save.dbgctl = data;
> +		if (!svm_has(SVM_FEATURE_LBRV))
> +			break;
> +		if (data & (1ULL<<0))
> +			svm_enable_lbrv(svm);
> +		else
> +			svm_disable_lbrv(svm);
> +		break;
>  	default:
>  	unhandled:
>  		return kvm_set_msr_common(vcpu, ecx, data);
>   

This still has the same issue as the previous patchset:  if the guest 
enables some other bit in MSR_IA32_DEBUCTLMSR, we silently ignore it.  
We should either pr_unimpl() on such bits or not handle them (ultimately 
injecting a #GP).

Also, I'd like a simple patch for 2.6.25 to add support for Windows x86 
on AMD.  So if the first patch in the series can add support for the 
bits that Windows sets in MSR_IA32_DEBUGCTLMSR (I imagine it just writes 
zero?) then I can queue that for 2.6.25 and the rest for 2.6.26.

-- 
Any sufficiently difficult bug is indistinguishable from a feature.


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