linux-kernel - Re: [PATCH v3 6/7] x86: KVM: svm: eliminate weird goto from vmrun

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Date:   Fri, 9 Aug 2019 11:46:44 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Jim Mattson <jmattson@...gle.com>
Subject: Re: [PATCH v3 6/7] x86: KVM: svm: eliminate weird goto from
 vmrun_interception()

On Thu, Aug 08, 2019 at 07:30:50PM +0200, Vitaly Kuznetsov wrote:
> Regardless of whether or not nested_svm_vmrun_msrpm() fails, we return 1
> from vmrun_interception() so there's no point in doing goto. Also,
> nested_svm_vmrun_msrpm() call can be made from nested_svm_vmrun() where
> other nested launch issues are handled.
> 
> Suggested-by: Sean Christopherson <sean.j.christopherson@...el.com>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
> ---
>  arch/x86/kvm/svm.c | 23 +++++++++--------------
>  1 file changed, 9 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 6d16d1898810..43bc4a5e4948 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -3658,6 +3658,15 @@ static bool nested_svm_vmrun(struct vcpu_svm *svm)
>  
>  	enter_svm_guest_mode(svm, vmcb_gpa, nested_vmcb, &map);
>  
> +	if (!nested_svm_vmrun_msrpm(svm)) {
> +		svm->vmcb->control.exit_code    = SVM_EXIT_ERR;
> +		svm->vmcb->control.exit_code_hi = 0;
> +		svm->vmcb->control.exit_info_1  = 0;
> +		svm->vmcb->control.exit_info_2  = 0;
> +
> +		nested_svm_vmexit(svm);
> +	}
> +
>  	return true;

nested_svm_vmrun() no longer needs a return value, it just needs to return
early.  But making it 'void' just to change it to 'int' in the next patch
is a bit gratuitous, so what about changing it to return an 'int' in this
patch?

That'd also eliminate the funky

	if (!nested_svm_vmrun(svm))
		return 1;

	return 1;

chunk in vmrun_interception() that temporarily exists until patch 7/7.

>  }
>  
> @@ -3740,20 +3749,6 @@ static int vmrun_interception(struct vcpu_svm *svm)
>  	if (!nested_svm_vmrun(svm))
>  		return 1;
>  
> -	if (!nested_svm_vmrun_msrpm(svm))
> -		goto failed;
> -
> -	return 1;
> -
> -failed:
> -
> -	svm->vmcb->control.exit_code    = SVM_EXIT_ERR;
> -	svm->vmcb->control.exit_code_hi = 0;
> -	svm->vmcb->control.exit_info_1  = 0;
> -	svm->vmcb->control.exit_info_2  = 0;
> -
> -	nested_svm_vmexit(svm);
> -
>  	return 1;
>  }
>  
> -- 
> 2.20.1
>