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Subject: Re: [PATCH 2/7] KVM: SVM: extract load_nested_vmcb_control
To:     Paolo Bonzini <pbonzini@redhat.com>, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org
Cc:     Cathy Avery <cavery@redhat.com>,
        Liran Alon <liran.alon@oracle.com>,
        Jim Mattson <jmattson@google.com>
References: <20200515174144.1727-1-pbonzini@redhat.com>
 <20200515174144.1727-3-pbonzini@redhat.com>
From:   Krish Sadhukhan <krish.sadhukhan@oracle.com>
Message-ID: <73188a11-8208-cac6-4d30-4cf67a5d89bc@oracle.com>
Date:   Fri, 15 May 2020 16:09:43 -0700
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On 5/15/20 10:41 AM, Paolo Bonzini wrote:
> When restoring SVM nested state, the control state will be stored already
> in svm->nested by KVM_SET_NESTED_STATE.  We will not need to fish it out of
> L1's VMCB.  Pull everything into a separate function so that it is
> documented which fields are needed.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>   arch/x86/kvm/svm/nested.c | 45 ++++++++++++++++++++++-----------------
>   1 file changed, 25 insertions(+), 20 deletions(-)
>
> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> index 22f75f66084f..e79acc852000 100644
> --- a/arch/x86/kvm/svm/nested.c
> +++ b/arch/x86/kvm/svm/nested.c
> @@ -225,6 +225,27 @@ static bool nested_vmcb_checks(struct vmcb *vmcb)
>   	return true;
>   }
>   
> +static void load_nested_vmcb_control(struct vcpu_svm *svm, struct vmcb *nested_vmcb)


This function only separates a subset of the controls. If the purpose of 
the function is to separate only the controls that are related to 
migration, should it be called something like 
load_nested_state_vmcb_control or something like that ?

> +{
> +	if (kvm_get_rflags(&svm->vcpu) & X86_EFLAGS_IF)
> +		svm->vcpu.arch.hflags |= HF_HIF_MASK;
> +	else
> +		svm->vcpu.arch.hflags &= ~HF_HIF_MASK;
> +
> +	svm->nested.nested_cr3 = nested_vmcb->control.nested_cr3;
> +
> +	svm->nested.vmcb_msrpm = nested_vmcb->control.msrpm_base_pa & ~0x0fffULL;
> +	svm->nested.vmcb_iopm  = nested_vmcb->control.iopm_base_pa  & ~0x0fffULL;
> +
> +	/* cache intercepts */
> +	svm->nested.intercept_cr         = nested_vmcb->control.intercept_cr;
> +	svm->nested.intercept_dr         = nested_vmcb->control.intercept_dr;
> +	svm->nested.intercept_exceptions = nested_vmcb->control.intercept_exceptions;
> +	svm->nested.intercept            = nested_vmcb->control.intercept;
> +
> +	svm->vcpu.arch.tsc_offset += nested_vmcb->control.tsc_offset;
> +}
> +
>   void enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb_gpa,
>   			  struct vmcb *nested_vmcb)
>   {
> @@ -232,15 +253,11 @@ void enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb_gpa,
>   		is_intercept(svm, INTERCEPT_VINTR) ||
>   		is_intercept(svm, INTERCEPT_IRET);
>   
> -	if (kvm_get_rflags(&svm->vcpu) & X86_EFLAGS_IF)
> -		svm->vcpu.arch.hflags |= HF_HIF_MASK;
> -	else
> -		svm->vcpu.arch.hflags &= ~HF_HIF_MASK;
> +	svm->nested.vmcb = vmcb_gpa;
> +	load_nested_vmcb_control(svm, nested_vmcb);
>   
> -	if (nested_vmcb->control.nested_ctl & SVM_NESTED_CTL_NP_ENABLE) {
> -		svm->nested.nested_cr3 = nested_vmcb->control.nested_cr3;
> +	if (nested_vmcb->control.nested_ctl & SVM_NESTED_CTL_NP_ENABLE)
>   		nested_svm_init_mmu_context(&svm->vcpu);
> -	}
>   
>   	/* Load the nested guest state */
>   	svm->vmcb->save.es = nested_vmcb->save.es;
> @@ -275,25 +292,15 @@ void enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb_gpa,
>   	svm->vcpu.arch.dr6  = nested_vmcb->save.dr6;
>   	svm->vmcb->save.cpl = nested_vmcb->save.cpl;
>   
> -	svm->nested.vmcb_msrpm = nested_vmcb->control.msrpm_base_pa & ~0x0fffULL;
> -	svm->nested.vmcb_iopm  = nested_vmcb->control.iopm_base_pa  & ~0x0fffULL;
> -
> -	/* cache intercepts */
> -	svm->nested.intercept_cr         = nested_vmcb->control.intercept_cr;
> -	svm->nested.intercept_dr         = nested_vmcb->control.intercept_dr;
> -	svm->nested.intercept_exceptions = nested_vmcb->control.intercept_exceptions;
> -	svm->nested.intercept            = nested_vmcb->control.intercept;
> -
>   	svm_flush_tlb(&svm->vcpu);
> -	svm->vmcb->control.int_ctl = nested_vmcb->control.int_ctl | V_INTR_MASKING_MASK;
>   	if (nested_vmcb->control.int_ctl & V_INTR_MASKING_MASK)
>   		svm->vcpu.arch.hflags |= HF_VINTR_MASK;
>   	else
>   		svm->vcpu.arch.hflags &= ~HF_VINTR_MASK;
>   
> -	svm->vcpu.arch.tsc_offset += nested_vmcb->control.tsc_offset;
>   	svm->vmcb->control.tsc_offset = svm->vcpu.arch.tsc_offset;
>   
> +	svm->vmcb->control.int_ctl = nested_vmcb->control.int_ctl | V_INTR_MASKING_MASK;
>   	svm->vmcb->control.virt_ext = nested_vmcb->control.virt_ext;
>   	svm->vmcb->control.int_vector = nested_vmcb->control.int_vector;
>   	svm->vmcb->control.int_state = nested_vmcb->control.int_state;
> @@ -314,8 +321,6 @@ void enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb_gpa,
>   	 */
>   	recalc_intercepts(svm);
>   
> -	svm->nested.vmcb = vmcb_gpa;
> -
>   	/*
>   	 * If L1 had a pending IRQ/NMI before executing VMRUN,
>   	 * which wasn't delivered because it was disallowed (e.g.