linux-kernel - Re: [PATCH v3 2/3] KVM: nVMX: Validate the IA32

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Date:   Thu, 2 Nov 2017 18:50:08 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Wanpeng Li <kernellwp@...il.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     Radim Krčmář <rkrcmar@...hat.com>,
        Wanpeng Li <wanpeng.li@...mail.com>,
        Jim Mattson <jmattson@...gle.com>
Subject: Re: [PATCH v3 2/3] KVM: nVMX: Validate the IA32_BNDCFGS on nested
 VM-entry

On 02/11/2017 09:31, Wanpeng Li wrote:
> From: Wanpeng Li <wanpeng.li@...mail.com>
> 
> 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@...hat.com>
> Cc: Radim Krčmář <rkrcmar@...hat.com>
> Cc: Jim Mattson <jmattson@...gle.com>
> Signed-off-by: Wanpeng Li <wanpeng.li@...mail.com>
> ---
>  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;
>  }
>  
>