Re: [PATCH v3 2/3] KVM: nVMX: Validate the IA32_BNDCFGS on nested VM-entry

[Paolo Bonzini]

On 02/11/2017 09:31, Wanpeng Li wrote:
> From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
> 
> According to the SDM, if the "load IA32_BNDCFGS" VM-entry controls is 1, the
> following checks are performed on the field for the IA32_BNDCFGS MSR:
>  - Bits reserved in the IA32_BNDCFGS MSR must be 0.
>  - The linear address in bits 63:12 must be canonical.
> 
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: Radim KrÄmÃÅ <rkrcmar@xxxxxxxxxx>
> Cc: Jim Mattson <jmattson@xxxxxxxxxx>
> Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
> ---
>  arch/x86/kvm/vmx.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index e6c8ffa..f29f57d 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -10805,6 +10805,13 @@ static int check_vmentry_postreqs(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
>  			return 1;
>  	}
>  
> +	if (kvm_mpx_supported() &&
> +		(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_BNDCFGS)) {

Whenever !kvm_mpx_supported() is true, the bit is not set in
vmcs12->vm_entry_controls (see nested_vmx_setup_ctls_msrs), so the
condition can be simplified.  Please also use && instead of nested "if"s.

Thanks,

Paolo

> +		if (is_noncanonical_address(vmcs12->guest_bndcfgs & PAGE_MASK, vcpu) ||
> +		    (vmcs12->guest_bndcfgs & MSR_IA32_BNDCFGS_RSVD))
> +			return 1;
> +	}
> +
>  	return 0;
>  }
>  
>