linux-kernel - Re: [PATCH] KVM: x86/mmu: Stash 'kvm' in a local variable in kvm_mmu_free

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Date:   Thu, 24 Sep 2020 14:42:19 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: x86/mmu: Stash 'kvm' in a local variable in kvm_mmu_free_roots()

Sean Christopherson <sean.j.christopherson@...el.com> writes:

> To make kvm_mmu_free_roots() a bit more readable, capture 'kvm' in a
> local variable instead of doing vcpu->kvm over and over (and over).
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> ---
>  arch/x86/kvm/mmu/mmu.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 76c5826e29a2..cdc498093450 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -3603,6 +3603,7 @@ static void mmu_free_root_page(struct kvm *kvm, hpa_t *root_hpa,
>  void kvm_mmu_free_roots(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
>  			ulong roots_to_free)
>  {
> +	struct kvm *kvm = vcpu->kvm;
>  	int i;
>  	LIST_HEAD(invalid_list);
>  	bool free_active_root = roots_to_free & KVM_MMU_ROOT_CURRENT;
> @@ -3620,22 +3621,21 @@ void kvm_mmu_free_roots(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
>  			return;
>  	}
>  
> -	spin_lock(&vcpu->kvm->mmu_lock);
> +	spin_lock(&kvm->mmu_lock);
>  
>  	for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++)
>  		if (roots_to_free & KVM_MMU_ROOT_PREVIOUS(i))
> -			mmu_free_root_page(vcpu->kvm, &mmu->prev_roots[i].hpa,
> +			mmu_free_root_page(kvm, &mmu->prev_roots[i].hpa,
>  					   &invalid_list);
>  
>  	if (free_active_root) {
>  		if (mmu->shadow_root_level >= PT64_ROOT_4LEVEL &&
>  		    (mmu->root_level >= PT64_ROOT_4LEVEL || mmu->direct_map)) {
> -			mmu_free_root_page(vcpu->kvm, &mmu->root_hpa,
> -					   &invalid_list);
> +			mmu_free_root_page(kvm, &mmu->root_hpa, &invalid_list);
>  		} else {
>  			for (i = 0; i < 4; ++i)
>  				if (mmu->pae_root[i] != 0)
> -					mmu_free_root_page(vcpu->kvm,
> +					mmu_free_root_page(kvm,
>  							   &mmu->pae_root[i],
>  							   &invalid_list);
>  			mmu->root_hpa = INVALID_PAGE;
> @@ -3643,8 +3643,8 @@ void kvm_mmu_free_roots(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
>  		mmu->root_pgd = 0;
>  	}
>  
> -	kvm_mmu_commit_zap_page(vcpu->kvm, &invalid_list);
> -	spin_unlock(&vcpu->kvm->mmu_lock);
> +	kvm_mmu_commit_zap_page(kvm, &invalid_list);
> +	spin_unlock(&kvm->mmu_lock);
>  }
>  EXPORT_SYMBOL_GPL(kvm_mmu_free_roots);

What about kvm_mmu_get_page(), make_mmu_pages_available(),
mmu_alloc_root(), kvm_mmu_sync_roots(), direct_page_fault(),
kvm_mmu_pte_write() which seem to be using the same ugly pattern? :-)

Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>

-- 
Vitaly