linux-kernel - Re: [PATCH v4 3/4] KVM: x86/mmu: count KVM mmu usage in secondary pagetable stats.

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Message-ID: <YtsPk5+hZNMEwT0c@google.com>
Date:   Fri, 22 Jul 2022 20:58:59 +0000
From:   Mingwei Zhang <mizhang@...gle.com>
To:     Yosry Ahmed <yosryahmed@...gle.com>
Cc:     Tejun Heo <tj@...nel.org>, Johannes Weiner <hannes@...xchg.org>,
        Zefan Li <lizefan.x@...edance.com>,
        Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Shakeel Butt <shakeelb@...gle.com>,
        Oliver Upton <oupton@...gle.com>, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.cs.columbia.edu, kvm@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH v4 3/4] KVM: x86/mmu: count KVM mmu usage in secondary
 pagetable stats.

On Fri, Apr 29, 2022, Yosry Ahmed wrote:
> Count the pages used by KVM mmu on x86 for in secondary pagetable stats.
> 
> For the legacy mmu, accounting pagetable stats is combined KVM's
> existing for mmu pages in newly introduced kvm_[un]account_mmu_page()
> helpers.
> 
> For tdp mmu, introduce new tdp_[un]account_mmu_page() helpers. That
> combines accounting pagetable stats with the tdp_mmu_pages counter
> accounting.
> 
> tdp_mmu_pages counter introduced in this series [1]. This patch was
> rebased on top of the first two patches in that series.
> 
> [1]https://lore.kernel.org/lkml/20220401063636.2414200-1-mizhang@google.com/
> 
> Signed-off-by: Yosry Ahmed <yosryahmed@...gle.com>
> ---

It looks like there are two metrics for mmu in x86: one for shadow mmu
and the other for TDP mmu. Is there any plan to merge them together?

>  arch/x86/kvm/mmu/mmu.c     | 16 ++++++++++++++--
>  arch/x86/kvm/mmu/tdp_mmu.c | 16 ++++++++++++++--
>  2 files changed, 28 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 78d8e1d8fb99..e5b0e826445d 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -1679,6 +1679,18 @@ static inline void kvm_mod_used_mmu_pages(struct kvm *kvm, long nr)
>  	percpu_counter_add(&kvm_total_used_mmu_pages, nr);
>  }
>  
> +static void kvm_account_mmu_page(struct kvm *kvm, struct kvm_mmu_page *sp)
> +{
> +	kvm_mod_used_mmu_pages(kvm, +1);
> +	kvm_account_pgtable_pages((void *)sp->spt, +1);
> +}
> +
> +static void kvm_unaccount_mmu_page(struct kvm *kvm, struct kvm_mmu_page *sp)
> +{
> +	kvm_mod_used_mmu_pages(kvm, -1);
> +	kvm_account_pgtable_pages((void *)sp->spt, -1);
> +}
> +
>  static void kvm_mmu_free_page(struct kvm_mmu_page *sp)
>  {
>  	MMU_WARN_ON(!is_empty_shadow_page(sp->spt));
> @@ -1734,7 +1746,7 @@ static struct kvm_mmu_page *kvm_mmu_alloc_page(struct kvm_vcpu *vcpu, int direct
>  	 */
>  	sp->mmu_valid_gen = vcpu->kvm->arch.mmu_valid_gen;
>  	list_add(&sp->link, &vcpu->kvm->arch.active_mmu_pages);
> -	kvm_mod_used_mmu_pages(vcpu->kvm, +1);
> +	kvm_account_mmu_page(vcpu->kvm, sp);
>  	return sp;
>  }
>  
> @@ -2363,7 +2375,7 @@ static bool __kvm_mmu_prepare_zap_page(struct kvm *kvm,
>  			list_add(&sp->link, invalid_list);
>  		else
>  			list_move(&sp->link, invalid_list);
> -		kvm_mod_used_mmu_pages(kvm, -1);
> +		kvm_unaccount_mmu_page(kvm, sp);
>  	} else {
>  		/*
>  		 * Remove the active root from the active page list, the root
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index 3456277ade18..6295c4da5dee 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -371,6 +371,18 @@ static void handle_changed_spte_dirty_log(struct kvm *kvm, int as_id, gfn_t gfn,
>  	}
>  }
>  
> +static void tdp_account_mmu_page(struct kvm *kvm, struct kvm_mmu_page *sp)
> +{
> +	atomic64_inc(&kvm->arch.tdp_mmu_pages);
> +	kvm_account_pgtable_pages((void *)sp->spt, +1);
> +}
> +
> +static void tdp_unaccount_mmu_page(struct kvm *kvm, struct kvm_mmu_page *sp)
> +{
> +	atomic64_dec(&kvm->arch.tdp_mmu_pages);
> +	kvm_account_pgtable_pages((void *)sp->spt, -1);
> +}
> +
>  /**
>   * tdp_mmu_unlink_sp() - Remove a shadow page from the list of used pages
>   *
> @@ -383,7 +395,7 @@ static void handle_changed_spte_dirty_log(struct kvm *kvm, int as_id, gfn_t gfn,
>  static void tdp_mmu_unlink_sp(struct kvm *kvm, struct kvm_mmu_page *sp,
>  			      bool shared)
>  {
> -	atomic64_dec(&kvm->arch.tdp_mmu_pages);
> +	tdp_unaccount_mmu_page(kvm, sp);
>  
>  	if (!sp->lpage_disallowed)
>  		return;
> @@ -1121,7 +1133,7 @@ static int tdp_mmu_link_sp(struct kvm *kvm, struct tdp_iter *iter,
>  		tdp_mmu_set_spte(kvm, iter, spte);
>  	}
>  
> -	atomic64_inc(&kvm->arch.tdp_mmu_pages);
> +	tdp_account_mmu_page(kvm, sp);
>  
>  	return 0;
>  }
> -- 
> 2.36.0.464.gb9c8b46e94-goog
>