linux-kernel - Re: [PATCH 05/23] KVM: MMU: pull computation of kvm_mmu_role_regs to kvm_init

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Date:   Fri, 4 Feb 2022 18:45:37 +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 05/23] KVM: MMU: pull computation of kvm_mmu_role_regs to
 kvm_init_mmu

On Fri, Feb 04, 2022 at 06:57:00AM -0500, Paolo Bonzini wrote:
> The init_kvm_*mmu functions, with the exception of shadow NPT,
> do not need to know the full values of CR0/CR4/EFER; they only
> need to know the bits that make up the "role".  This cleanup
> however will take quite a few incremental steps.  As a start,
> pull the common computation of the struct kvm_mmu_role_regs
> into their caller: all of them extract the struct from the vcpu
> as the very first step.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  arch/x86/kvm/mmu/mmu.c | 33 +++++++++++++++++----------------
>  1 file changed, 17 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 3add9d8b0630..577e70509510 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -4736,12 +4736,12 @@ kvm_calc_tdp_mmu_root_page_role(struct kvm_vcpu *vcpu,
>  	return role;
>  }
>  
> -static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
> +static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu,
> +			     const struct kvm_mmu_role_regs *regs)
>  {
>  	struct kvm_mmu *context = &vcpu->arch.root_mmu;
> -	struct kvm_mmu_role_regs regs = vcpu_to_role_regs(vcpu);
>  	union kvm_mmu_role new_role =
> -		kvm_calc_tdp_mmu_root_page_role(vcpu, &regs, false);
> +		kvm_calc_tdp_mmu_root_page_role(vcpu, regs, false);
>  
>  	if (new_role.as_u64 == context->mmu_role.as_u64)
>  		return;
> @@ -4755,7 +4755,7 @@ static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
>  	context->get_guest_pgd = get_cr3;
>  	context->get_pdptr = kvm_pdptr_read;
>  	context->inject_page_fault = kvm_inject_page_fault;
> -	context->root_level = role_regs_to_root_level(&regs);
> +	context->root_level = role_regs_to_root_level(regs);
>  
>  	if (!is_cr0_pg(context))
>  		context->gva_to_gpa = nonpaging_gva_to_gpa;
> @@ -4803,7 +4803,7 @@ kvm_calc_shadow_mmu_root_page_role(struct kvm_vcpu *vcpu,
>  }
>  
>  static void shadow_mmu_init_context(struct kvm_vcpu *vcpu, struct kvm_mmu *context,
> -				    struct kvm_mmu_role_regs *regs,
> +				    const struct kvm_mmu_role_regs *regs,
>  				    union kvm_mmu_role new_role)
>  {
>  	if (new_role.as_u64 == context->mmu_role.as_u64)
> @@ -4824,7 +4824,7 @@ static void shadow_mmu_init_context(struct kvm_vcpu *vcpu, struct kvm_mmu *conte
>  }
>  
>  static void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu,
> -				struct kvm_mmu_role_regs *regs)
> +				const struct kvm_mmu_role_regs *regs)
>  {
>  	struct kvm_mmu *context = &vcpu->arch.root_mmu;
>  	union kvm_mmu_role new_role =
> @@ -4845,7 +4845,7 @@ static void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu,
>  
>  static union kvm_mmu_role
>  kvm_calc_shadow_npt_root_page_role(struct kvm_vcpu *vcpu,
> -				   struct kvm_mmu_role_regs *regs)
> +				   const struct kvm_mmu_role_regs *regs)

Should these go in the previous commit? Aside from that,

Reviewed-by: David Matlack <dmatlack@...gle>

>  {
>  	union kvm_mmu_role role =
>  		kvm_calc_shadow_root_page_role_common(vcpu, regs, false);
> @@ -4930,12 +4930,12 @@ 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)
> +static void init_kvm_softmmu(struct kvm_vcpu *vcpu,
> +			     const struct kvm_mmu_role_regs *regs)
>  {
>  	struct kvm_mmu *context = &vcpu->arch.root_mmu;
> -	struct kvm_mmu_role_regs regs = vcpu_to_role_regs(vcpu);
>  
> -	kvm_init_shadow_mmu(vcpu, &regs);
> +	kvm_init_shadow_mmu(vcpu, regs);
>  
>  	context->get_guest_pgd     = get_cr3;
>  	context->get_pdptr         = kvm_pdptr_read;
> @@ -4959,10 +4959,9 @@ kvm_calc_nested_mmu_role(struct kvm_vcpu *vcpu, const struct kvm_mmu_role_regs *
>  	return role;
>  }
>  
> -static void init_kvm_nested_mmu(struct kvm_vcpu *vcpu)
> +static void init_kvm_nested_mmu(struct kvm_vcpu *vcpu, const struct kvm_mmu_role_regs *regs)
>  {
> -	struct kvm_mmu_role_regs regs = vcpu_to_role_regs(vcpu);
> -	union kvm_mmu_role new_role = kvm_calc_nested_mmu_role(vcpu, &regs);
> +	union kvm_mmu_role new_role = kvm_calc_nested_mmu_role(vcpu, regs);
>  	struct kvm_mmu *g_context = &vcpu->arch.nested_mmu;
>  
>  	if (new_role.as_u64 == g_context->mmu_role.as_u64)
> @@ -5002,12 +5001,14 @@ static void init_kvm_nested_mmu(struct kvm_vcpu *vcpu)
>  
>  void kvm_init_mmu(struct kvm_vcpu *vcpu)
>  {
> +	struct kvm_mmu_role_regs regs = vcpu_to_role_regs(vcpu);
> +
>  	if (mmu_is_nested(vcpu))
> -		init_kvm_nested_mmu(vcpu);
> +		init_kvm_nested_mmu(vcpu, &regs);
>  	else if (tdp_enabled)
> -		init_kvm_tdp_mmu(vcpu);
> +		init_kvm_tdp_mmu(vcpu, &regs);
>  	else
> -		init_kvm_softmmu(vcpu);
> +		init_kvm_softmmu(vcpu, &regs);
>  }
>  EXPORT_SYMBOL_GPL(kvm_init_mmu);
>  
> -- 
> 2.31.1
> 
>