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Date:   Fri, 4 Feb 2022 18:41:59 +0000
From:   David Matlack <dmatlack@google.com>
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        seanjc@google.com, vkuznets@redhat.com
Subject: Re: [PATCH 04/23] KVM: MMU: constify uses of struct kvm_mmu_role_regs
Message-ID: <Yf1zd4urw8Jro5mi@google.com>
References: <20220204115718.14934-1-pbonzini@redhat.com>
 <20220204115718.14934-5-pbonzini@redhat.com>
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On Fri, Feb 04, 2022 at 06:56:59AM -0500, Paolo Bonzini wrote:
> struct kvm_mmu_role_regs is computed just once and then accessed.  Use
> const to enforce this.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Reviewed-by: David Matlack <dmatlack@google.com>

> ---
>  arch/x86/kvm/mmu/mmu.c | 19 +++++++++++--------
>  1 file changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 0039b2f21286..3add9d8b0630 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -208,7 +208,7 @@ struct kvm_mmu_role_regs {
>   * the single source of truth for the MMU's state.
>   */
>  #define BUILD_MMU_ROLE_REGS_ACCESSOR(reg, name, flag)			\
> -static inline bool __maybe_unused ____is_##reg##_##name(struct kvm_mmu_role_regs *regs)\
> +static inline bool __maybe_unused ____is_##reg##_##name(const struct kvm_mmu_role_regs *regs)\
>  {									\
>  	return !!(regs->reg & flag);					\
>  }
> @@ -255,7 +255,7 @@ static struct kvm_mmu_role_regs vcpu_to_role_regs(struct kvm_vcpu *vcpu)
>  	return regs;
>  }
>  
> -static int role_regs_to_root_level(struct kvm_mmu_role_regs *regs)
> +static int role_regs_to_root_level(const struct kvm_mmu_role_regs *regs)
>  {
>  	if (!____is_cr0_pg(regs))
>  		return 0;
> @@ -4666,7 +4666,7 @@ static void paging32_init_context(struct kvm_mmu *context)
>  }
>  
>  static union kvm_mmu_extended_role kvm_calc_mmu_role_ext(struct kvm_vcpu *vcpu,
> -							 struct kvm_mmu_role_regs *regs)
> +							 const struct kvm_mmu_role_regs *regs)
>  {
>  	union kvm_mmu_extended_role ext = {0};
>  
> @@ -4687,7 +4687,7 @@ static union kvm_mmu_extended_role kvm_calc_mmu_role_ext(struct kvm_vcpu *vcpu,
>  }
>  
>  static union kvm_mmu_role kvm_calc_mmu_role_common(struct kvm_vcpu *vcpu,
> -						   struct kvm_mmu_role_regs *regs,
> +						   const struct kvm_mmu_role_regs *regs,
>  						   bool base_only)
>  {
>  	union kvm_mmu_role role = {0};
> @@ -4723,7 +4723,8 @@ static inline int kvm_mmu_get_tdp_level(struct kvm_vcpu *vcpu)
>  
>  static union kvm_mmu_role
>  kvm_calc_tdp_mmu_root_page_role(struct kvm_vcpu *vcpu,
> -				struct kvm_mmu_role_regs *regs, bool base_only)
> +				const struct kvm_mmu_role_regs *regs,
> +				bool base_only)
>  {
>  	union kvm_mmu_role role = kvm_calc_mmu_role_common(vcpu, regs, base_only);
>  
> @@ -4769,7 +4770,8 @@ static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
>  
>  static union kvm_mmu_role
>  kvm_calc_shadow_root_page_role_common(struct kvm_vcpu *vcpu,
> -				      struct kvm_mmu_role_regs *regs, bool base_only)
> +				      const struct kvm_mmu_role_regs *regs,
> +				      bool base_only)
>  {
>  	union kvm_mmu_role role = kvm_calc_mmu_role_common(vcpu, regs, base_only);
>  
> @@ -4782,7 +4784,8 @@ kvm_calc_shadow_root_page_role_common(struct kvm_vcpu *vcpu,
>  
>  static union kvm_mmu_role
>  kvm_calc_shadow_mmu_root_page_role(struct kvm_vcpu *vcpu,
> -				   struct kvm_mmu_role_regs *regs, bool base_only)
> +				   const struct kvm_mmu_role_regs *regs,
> +				   bool base_only)
>  {
>  	union kvm_mmu_role role =
>  		kvm_calc_shadow_root_page_role_common(vcpu, regs, base_only);
> @@ -4940,7 +4943,7 @@ static void init_kvm_softmmu(struct kvm_vcpu *vcpu)
>  }
>  
>  static union kvm_mmu_role
> -kvm_calc_nested_mmu_role(struct kvm_vcpu *vcpu, struct kvm_mmu_role_regs *regs)
> +kvm_calc_nested_mmu_role(struct kvm_vcpu *vcpu, const struct kvm_mmu_role_regs *regs)
>  {
>  	union kvm_mmu_role role;
>  
> -- 
> 2.31.1
> 
>