Re: [PATCH v3 3/4] KVM: SVM: Fix CPL updates

[Gleb Natapov <gleb@redhat.com>]

On Fri, Feb 03, 2012 at 07:29:24PM +0100, Kevin Wolf wrote:
> Keep CPL at 0 in real mode and at 3 in VM86. In protected/long mode, use
> RPL rather than DPL of the code segment.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  arch/x86/kvm/svm.c |   19 ++++++++++++++++---
>  1 files changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 6a977c1..4124a7e 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -1263,6 +1263,21 @@ static void svm_vcpu_put(struct kvm_vcpu *vcpu)
>  		wrmsrl(host_save_user_msrs[i], svm->host_user_msrs[i]);
>  }
>  
> +static void svm_update_cpl(struct kvm_vcpu *vcpu)
> +{
> +	struct vcpu_svm *svm = to_svm(vcpu);
> +	int cpl;
> +
> +	if (!is_protmode(vcpu))
> +		cpl = 0;
> +	else if (svm->vmcb->save.rflags & X86_EFLAGS_VM)
> +		cpl = 3;
> +	else
> +		cpl = svm->vmcb->save.cs.selector & 0x3;
> +
> +	svm->vmcb->save.cpl = cpl;
> +}
> +
As you probably know already I think cpl should be updated in
svm_get_rflags() too. With current patch restoring CS segment
register before rflags register after migration may cause cpl
to get wrong value for instance.

>  static unsigned long svm_get_rflags(struct kvm_vcpu *vcpu)
>  {
>  	return to_svm(vcpu)->vmcb->save.rflags;
> @@ -1538,9 +1553,7 @@ static void svm_set_segment(struct kvm_vcpu *vcpu,
>  		s->attrib |= (var->g & 1) << SVM_SELECTOR_G_SHIFT;
>  	}
>  	if (seg == VCPU_SREG_CS)
> -		svm->vmcb->save.cpl
> -			= (svm->vmcb->save.cs.attrib
> -			   >> SVM_SELECTOR_DPL_SHIFT) & 3;
> +		svm_update_cpl(vcpu);
>  
>  	mark_dirty(svm->vmcb, VMCB_SEG);
>  }
> -- 
> 1.7.6.5

--
			Gleb.