linux-kernel - Re: [PATCH v3 8/8] nSVM: remove unnecessary parameter in nested_vmcb_check

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Date:   Fri, 22 Oct 2021 17:51:41 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Emanuele Giuseppe Esposito <eesposit@...hat.com>,
        kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 8/8] nSVM: remove unnecessary parameter in
 nested_vmcb_check_controls

On Mon, 2021-10-11 at 10:37 -0400, Emanuele Giuseppe Esposito wrote:
> Just as in nested_vmcb_valid_sregs, we only need the vcpu param
> to perform the checks on vmcb nested state, since we always
> look at the cached fields.
> 
> Signed-off-by: Emanuele Giuseppe Esposito <eesposit@...hat.com>
> ---
>  arch/x86/kvm/svm/nested.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> index 13be1002ad1c..19bce3819cce 100644
> --- a/arch/x86/kvm/svm/nested.c
> +++ b/arch/x86/kvm/svm/nested.c
> @@ -209,9 +209,11 @@ static bool nested_svm_check_bitmap_pa(struct kvm_vcpu *vcpu, u64 pa, u32 size)
>  	    kvm_vcpu_is_legal_gpa(vcpu, addr + size - 1);
>  }
>  
> -static bool nested_vmcb_check_controls(struct kvm_vcpu *vcpu,
> -				       struct vmcb_ctrl_area_cached *control)
> +static bool nested_vmcb_check_controls(struct kvm_vcpu *vcpu)
>  {
> +	struct vcpu_svm *svm = to_svm(vcpu);
> +	struct vmcb_ctrl_area_cached *control = &svm->nested.ctl;
> +
>  	if (CC(!vmcb12_is_intercept(control, INTERCEPT_VMRUN)))
>  		return false;
>  
> @@ -651,7 +653,7 @@ int nested_svm_vmrun(struct kvm_vcpu *vcpu)
>  	nested_copy_vmcb_save_to_cache(svm, &vmcb12->save);
>  
>  	if (!nested_vmcb_valid_sregs(vcpu) ||
> -	    !nested_vmcb_check_controls(vcpu, &svm->nested.ctl)) {
> +	    !nested_vmcb_check_controls(vcpu)) {
>  		vmcb12->control.exit_code    = SVM_EXIT_ERR;
>  		vmcb12->control.exit_code_hi = 0;
>  		vmcb12->control.exit_info_1  = 0;
> @@ -1367,7 +1369,7 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
>  
>  	ret = -EINVAL;
>  	nested_copy_vmcb_control_to_cache(svm, ctl);
> -	if (!nested_vmcb_check_controls(vcpu, &svm->nested.ctl))
> +	if (!nested_vmcb_check_controls(vcpu))
>  		goto out_free_ctl;
>  
>  	/*

Because of the issue I pointed out in patch 7, you probably want:


static bool __nested_vmcb_check_controls(struct kvm_vcpu *vcpu,
                                         struct vmcb_ctrl_area_cached *control)
{
	....
}


static bool nested_vmcb_check_controls(struct kvm_vcpu *vcpu)
{
	return __nested_vmcb_check_controls(vcpu, &svm->nested.ctl);
}



Same for nested_vmcb_valid_sregs 
(maybe you even want to rename it to nested_vmcb_check_save while at it?):


static bool __nested_vmcb_check_save(struct kvm_vcpu *vcpu, struct vmcb_save_area_cached *save)
{
	...
}


static bool nested_vmcb_check_save(struct kvm_vcpu *vcpu)
{
	return __nested_vmcb_check_save(vcpu, &svm->nested.save);

}


Best regards,
	Maxim Levitsky