linux-kernel - Re: [PATCH 20/23] KVM: MMU: pull CPU role computation to kvm_init

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Message-ID: <YgGgRm/QNbordgqi@google.com>
Date:   Mon, 7 Feb 2022 22:42:14 +0000
From:   David Matlack <dmatlack@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        seanjc@...gle.com, vkuznets@...hat.com
Subject: Re: [PATCH 20/23] KVM: MMU: pull CPU role computation to kvm_init_mmu

On Fri, Feb 04, 2022 at 06:57:15AM -0500, Paolo Bonzini wrote:
> Do not lead init_kvm_*mmu into the temptation of poking
> into struct kvm_mmu_role_regs, by passing to it directly
> the CPU role.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  arch/x86/kvm/mmu/mmu.c | 21 +++++++++------------
>  1 file changed, 9 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 01027da82e23..6f9d876ce429 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -4721,11 +4721,9 @@ kvm_calc_tdp_mmu_root_page_role(struct kvm_vcpu *vcpu,
>  	return role;
>  }
>  
> -static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu,
> -			     const struct kvm_mmu_role_regs *regs)
> +static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu, union kvm_mmu_role cpu_role)
>  {
>  	struct kvm_mmu *context = &vcpu->arch.root_mmu;
> -	union kvm_mmu_role cpu_role = kvm_calc_cpu_role(vcpu, regs);
>  	union kvm_mmu_page_role mmu_role = kvm_calc_tdp_mmu_root_page_role(vcpu, cpu_role);
>  
>  	if (cpu_role.as_u64 == context->cpu_role.as_u64 &&
> @@ -4779,10 +4777,9 @@ static void shadow_mmu_init_context(struct kvm_vcpu *vcpu, struct kvm_mmu *conte
>  }
>  
>  static void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu,
> -				const struct kvm_mmu_role_regs *regs)
> +				union kvm_mmu_role cpu_role)
>  {
>  	struct kvm_mmu *context = &vcpu->arch.root_mmu;
> -	union kvm_mmu_role cpu_role = kvm_calc_cpu_role(vcpu, regs);
>  	union kvm_mmu_page_role mmu_role;
>  
>  	mmu_role = cpu_role.base;
> @@ -4874,20 +4871,19 @@ void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly,
>  EXPORT_SYMBOL_GPL(kvm_init_shadow_ept_mmu);
>  
>  static void init_kvm_softmmu(struct kvm_vcpu *vcpu,
> -			     const struct kvm_mmu_role_regs *regs)
> +			     union kvm_mmu_role cpu_role)
>  {
>  	struct kvm_mmu *context = &vcpu->arch.root_mmu;
>  
> -	kvm_init_shadow_mmu(vcpu, regs);
> +	kvm_init_shadow_mmu(vcpu, cpu_role);
>  
>  	context->get_guest_pgd     = get_cr3;
>  	context->get_pdptr         = kvm_pdptr_read;
>  	context->inject_page_fault = kvm_inject_page_fault;
>  }
>  
> -static void init_kvm_nested_mmu(struct kvm_vcpu *vcpu, const struct kvm_mmu_role_regs *regs)
> +static void init_kvm_nested_mmu(struct kvm_vcpu *vcpu, union kvm_mmu_role new_role)
>  {
> -	union kvm_mmu_role new_role = kvm_calc_cpu_role(vcpu, regs);
>  	struct kvm_mmu *g_context = &vcpu->arch.nested_mmu;
>  
>  	if (new_role.as_u64 == g_context->cpu_role.as_u64)
> @@ -4928,13 +4924,14 @@ static void init_kvm_nested_mmu(struct kvm_vcpu *vcpu, const struct kvm_mmu_role
>  void kvm_init_mmu(struct kvm_vcpu *vcpu)
>  {
>  	struct kvm_mmu_role_regs regs = vcpu_to_role_regs(vcpu);
> +	union kvm_mmu_role cpu_role = kvm_calc_cpu_role(vcpu, &regs);

WDYT about also inlining vcpu_to_role_regs() in kvm_calc_cpu_role()?

>  
>  	if (mmu_is_nested(vcpu))
> -		init_kvm_nested_mmu(vcpu, &regs);
> +		init_kvm_nested_mmu(vcpu, cpu_role);
>  	else if (tdp_enabled)
> -		init_kvm_tdp_mmu(vcpu, &regs);
> +		init_kvm_tdp_mmu(vcpu, cpu_role);
>  	else
> -		init_kvm_softmmu(vcpu, &regs);
> +		init_kvm_softmmu(vcpu, cpu_role);
>  }
>  EXPORT_SYMBOL_GPL(kvm_init_mmu);
>  
> -- 
> 2.31.1
> 
>