linux-kernel - Re: [Patch v4 07/18] KVM: x86/mmu: Unconditionally count allocations from MMU page caches

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Date:   Thu, 9 Mar 2023 18:03:51 +0200
From:   Zhi Wang <zhi.wang.linux@...il.com>
To:     Vipin Sharma <vipinsh@...gle.com>
Cc:     seanjc@...gle.com, pbonzini@...hat.com, bgardon@...gle.com,
        dmatlack@...gle.com, jmattson@...gle.com, mizhang@...gle.com,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [Patch v4 07/18] KVM: x86/mmu: Unconditionally count
 allocations from MMU page caches

On Mon,  6 Mar 2023 14:41:16 -0800
Vipin Sharma <vipinsh@...gle.com> wrote:

Ah, it is removed here. :)

> Remove count_shadow_page_allocations from struct shadow_page_caches{}.
> Remove count_allocation boolean condition check from
> mmu_sp_memory_cache_alloc().
> 
> Both split_shadow_page_cache and mmu_shadow_page_cache are counted in
> global count of unused cache pages. count_shadow_page_allocations
> boolean is obsolete and can be removed.
> 
> Signed-off-by: Vipin Sharma <vipinsh@...gle.com>
> ---
>  arch/x86/kvm/mmu/mmu.c          | 11 +++--------
>  arch/x86/kvm/mmu/mmu_internal.h |  3 +--
>  arch/x86/kvm/mmu/tdp_mmu.c      |  3 +--
>  3 files changed, 5 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 73a0ac9c11ce..0a0962d8108b 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -2184,7 +2184,6 @@ struct shadow_page_caches {
>  	struct kvm_mmu_memory_cache *page_header_cache;
>  	struct kvm_mmu_memory_cache *shadow_page_cache;
>  	struct kvm_mmu_memory_cache *shadowed_info_cache;
> -	bool count_shadow_page_allocation;
>  };
>  
>  static struct kvm_mmu_page *kvm_mmu_alloc_shadow_page(struct kvm *kvm,
> @@ -2196,8 +2195,7 @@ static struct kvm_mmu_page *kvm_mmu_alloc_shadow_page(struct kvm *kvm,
>  	struct kvm_mmu_page *sp;
>  
>  	sp = kvm_mmu_memory_cache_alloc(caches->page_header_cache);
> -	sp->spt = mmu_sp_memory_cache_alloc(caches->shadow_page_cache,
> -					    caches->count_shadow_page_allocation);
> +	sp->spt = mmu_sp_memory_cache_alloc(caches->shadow_page_cache);
>  	if (!role.direct)
>  		sp->shadowed_translation = kvm_mmu_memory_cache_alloc(caches->shadowed_info_cache);
>  
> @@ -2254,7 +2252,6 @@ static struct kvm_mmu_page *kvm_mmu_get_shadow_page(struct kvm_vcpu *vcpu,
>  		.page_header_cache = &vcpu->arch.mmu_page_header_cache,
>  		.shadow_page_cache = &vcpu->arch.mmu_shadow_page_cache,
>  		.shadowed_info_cache = &vcpu->arch.mmu_shadowed_info_cache,
> -		.count_shadow_page_allocation = true,
>  	};
>  
>  	return __kvm_mmu_get_shadow_page(vcpu->kvm, vcpu, &caches, gfn, role);
> @@ -6330,7 +6327,6 @@ static struct kvm_mmu_page *shadow_mmu_get_sp_for_split(struct kvm *kvm, u64 *hu
>  	/* Direct SPs do not require a shadowed_info_cache. */
>  	caches.page_header_cache = &kvm->arch.split_page_header_cache;
>  	caches.shadow_page_cache = &kvm->arch.split_shadow_page_cache;
> -	caches.count_shadow_page_allocation = true;
>  
>  	/* Safe to pass NULL for vCPU since requesting a direct SP. */
>  	return __kvm_mmu_get_shadow_page(kvm, NULL, &caches, gfn, role);
> @@ -7101,10 +7097,9 @@ void kvm_mmu_pre_destroy_vm(struct kvm *kvm)
>  		kthread_stop(kvm->arch.nx_huge_page_recovery_thread);
>  }
>  
> -void *mmu_sp_memory_cache_alloc(struct kvm_mmu_memory_cache *shadow_page_cache,
> -				bool count_allocation)
> +void *mmu_sp_memory_cache_alloc(struct kvm_mmu_memory_cache *shadow_page_cache)
>  {
> -	if (count_allocation && shadow_page_cache->nobjs)
> +	if (shadow_page_cache->nobjs)
>  		percpu_counter_dec(&kvm_total_unused_cached_pages);
>  	return kvm_mmu_memory_cache_alloc(shadow_page_cache);
>  }
> diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
> index 798cfbf0a36b..a607314348e3 100644
> --- a/arch/x86/kvm/mmu/mmu_internal.h
> +++ b/arch/x86/kvm/mmu/mmu_internal.h
> @@ -338,7 +338,6 @@ void *mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc);
>  
>  void track_possible_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp);
>  void untrack_possible_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp);
> -void *mmu_sp_memory_cache_alloc(struct kvm_mmu_memory_cache *cache,
> -				bool count_allocation);
> +void *mmu_sp_memory_cache_alloc(struct kvm_mmu_memory_cache *cache);
>  
>  #endif /* __KVM_X86_MMU_INTERNAL_H */
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index fa6eb1e9101e..d1e85012a008 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -265,8 +265,7 @@ static struct kvm_mmu_page *tdp_mmu_alloc_sp(struct kvm_vcpu *vcpu)
>  	struct kvm_mmu_page *sp;
>  
>  	sp = kvm_mmu_memory_cache_alloc(&vcpu->arch.mmu_page_header_cache);
> -	sp->spt = mmu_sp_memory_cache_alloc(&vcpu->arch.mmu_shadow_page_cache,
> -					    true);
> +	sp->spt = mmu_sp_memory_cache_alloc(&vcpu->arch.mmu_shadow_page_cache);
>  
>  	return sp;
>  }