linux-kernel - Re: [PATCH v2 20/25] KVM: x86/mmu: pull CPU mode computation to kvm_init

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Message-ID: <YieyS8iVwIqSK0Wb@google.com>
Date:   Tue, 8 Mar 2022 19:45:15 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        dmatlack@...gle.com
Subject: Re: [PATCH v2 20/25] KVM: x86/mmu: pull CPU mode computation to
 kvm_init_mmu

On Mon, Feb 21, 2022, 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 mode.
> 
> 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 47288643ab70..a7028c2ae5c7 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -4734,11 +4734,9 @@ 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_paging_mode cpu_mode)

Please keep the newline.  I like running over the 80 char soft limit when it
improves readability, but IMO stacking params is easier to read than a long line
unless it's over by like 3 chars or less.

>  {
>  	struct kvm_mmu *context = &vcpu->arch.root_mmu;
> -	union kvm_mmu_paging_mode cpu_mode = kvm_calc_cpu_mode(vcpu, regs);
>  	union kvm_mmu_page_role root_role = kvm_calc_tdp_mmu_root_page_role(vcpu, cpu_mode);
>  
>  	if (cpu_mode.as_u64 == context->cpu_mode.as_u64 &&

...

> -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_paging_mode new_mode)

And add one here (or retroactively add it back when @regs was constified).