linux-kernel - Re: [PATCH 10/30] KVM: nSVM: extract preparation of VMCB for nested run

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Date:   Fri, 29 May 2020 11:27:55 -0700
From:   Krish Sadhukhan <krish.sadhukhan@...cle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH 10/30] KVM: nSVM: extract preparation of VMCB for nested
 run


On 5/29/20 8:39 AM, Paolo Bonzini wrote:
> Split out filling svm->vmcb.save and svm->vmcb.control before VMRUN.
> Only the latter will be useful when restoring nested SVM state.
>
> This patch introduces no semantic change, so the MMU setup is still
> done in nested_prepare_vmcb_save.  The next patch will clean up things.
>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>   arch/x86/kvm/svm/nested.c | 40 +++++++++++++++++++++++----------------
>   1 file changed, 24 insertions(+), 16 deletions(-)
>
> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> index fc0c6d1678eb..73be7af79453 100644
> --- a/arch/x86/kvm/svm/nested.c
> +++ b/arch/x86/kvm/svm/nested.c
> @@ -245,21 +245,8 @@ static void load_nested_vmcb_control(struct vcpu_svm *svm,
>   	svm->vcpu.arch.tsc_offset += control->tsc_offset;
>   }
>   
> -void enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb_gpa,
> -			  struct vmcb *nested_vmcb)
> +static void nested_prepare_vmcb_save(struct vcpu_svm *svm, struct vmcb *nested_vmcb)


Not a big deal, but I feel that it helps a lot in readability if we keep 
the names symmetric. This one could be named prepare_nested_vmcb_save to 
match load_nested_vmcb_control that you created in the previous patch. 
Or load_nested_vmcb_control could be renamed to nested_load_vmcb_control 
to match the name here.

>   {
> -	bool evaluate_pending_interrupts =
> -		is_intercept(svm, INTERCEPT_VINTR) ||
> -		is_intercept(svm, INTERCEPT_IRET);
> -
> -	svm->nested.vmcb = vmcb_gpa;
> -	if (kvm_get_rflags(&svm->vcpu) & X86_EFLAGS_IF)
> -		svm->vcpu.arch.hflags |= HF_HIF_MASK;
> -	else
> -		svm->vcpu.arch.hflags &= ~HF_HIF_MASK;
> -
> -	load_nested_vmcb_control(svm, &nested_vmcb->control);
> -
>   	if (nested_vmcb->control.nested_ctl & SVM_NESTED_CTL_NP_ENABLE)
>   		nested_svm_init_mmu_context(&svm->vcpu);
>   
> @@ -291,7 +278,10 @@ void enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb_gpa,
>   	svm->vmcb->save.dr7 = nested_vmcb->save.dr7;
>   	svm->vcpu.arch.dr6  = nested_vmcb->save.dr6;
>   	svm->vmcb->save.cpl = nested_vmcb->save.cpl;
> +}
>   
> +static void nested_prepare_vmcb_control(struct vcpu_svm *svm, struct vmcb *nested_vmcb)
> +{
>   	svm_flush_tlb(&svm->vcpu);
>   	if (nested_vmcb->control.int_ctl & V_INTR_MASKING_MASK)
>   		svm->vcpu.arch.hflags |= HF_VINTR_MASK;
> @@ -321,6 +311,26 @@ void enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb_gpa,
>   	 */
>   	recalc_intercepts(svm);
>   
> +	mark_all_dirty(svm->vmcb);
> +}
> +
> +void enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb_gpa,
> +			  struct vmcb *nested_vmcb)
> +{
> +	bool evaluate_pending_interrupts =
> +		is_intercept(svm, INTERCEPT_VINTR) ||
> +		is_intercept(svm, INTERCEPT_IRET);
> +
> +	svm->nested.vmcb = vmcb_gpa;
> +	if (kvm_get_rflags(&svm->vcpu) & X86_EFLAGS_IF)
> +		svm->vcpu.arch.hflags |= HF_HIF_MASK;
> +	else
> +		svm->vcpu.arch.hflags &= ~HF_HIF_MASK;
> +
> +	load_nested_vmcb_control(svm, &nested_vmcb->control);
> +	nested_prepare_vmcb_save(svm, nested_vmcb);
> +	nested_prepare_vmcb_control(svm, nested_vmcb);
> +
>   	/*
>   	 * If L1 had a pending IRQ/NMI before executing VMRUN,
>   	 * which wasn't delivered because it was disallowed (e.g.
> @@ -336,8 +346,6 @@ void enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb_gpa,
>   	enable_gif(svm);
>   	if (unlikely(evaluate_pending_interrupts))
>   		kvm_make_request(KVM_REQ_EVENT, &svm->vcpu);
> -
> -	mark_all_dirty(svm->vmcb);
>   }
>   
>   int nested_svm_vmrun(struct vcpu_svm *svm)