Re: [PATCH] kvm: vmx: allow host to access guest MSR_IA32_BNDCFGS

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On 04/07/2017 04:27, Haozhong Zhang wrote:
> It's free for host applications, such as QEMU, to access guest
> MSR_IA32_BNDCFGS in VMCS, even though MPX is disabled in guest cpuid.
> 
> Signed-off-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>

Thanks, committed to kvm.git with

Cc: stable@xxxxxxxxxxxxxxx

Paolo

> ---
>  arch/x86/kvm/vmx.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index fb0471268a14..b4cfdcfdc1c1 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -3196,7 +3196,8 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  		msr_info->data = vmcs_readl(GUEST_SYSENTER_ESP);
>  		break;
>  	case MSR_IA32_BNDCFGS:
> -		if (!kvm_mpx_supported() || !guest_cpuid_has_mpx(vcpu))
> +		if (!kvm_mpx_supported() ||
> +		    (!msr_info->host_initiated && !guest_cpuid_has_mpx(vcpu)))
>  			return 1;
>  		msr_info->data = vmcs_read64(GUEST_BNDCFGS);
>  		break;
> @@ -3278,7 +3279,8 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  		vmcs_writel(GUEST_SYSENTER_ESP, data);
>  		break;
>  	case MSR_IA32_BNDCFGS:
> -		if (!kvm_mpx_supported() || !guest_cpuid_has_mpx(vcpu))
> +		if (!kvm_mpx_supported() ||
> +		    (!msr_info->host_initiated && !guest_cpuid_has_mpx(vcpu)))
>  			return 1;
>  		if (is_noncanonical_address(data & PAGE_MASK) ||
>  		    (data & MSR_IA32_BNDCFGS_RSVD))
> 



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