linux-kernel - Re: [PATCH 09/21] KVM: x86/mmu: Separate the memory caches for shadow pages and gfn arrays

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Date:   Tue, 9 Jun 2020 16:56:13 -0700
From:   Ben Gardon <bgardon@...gle.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Marc Zyngier <maz@...nel.org>, Paul Mackerras <paulus@...abs.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        David Hildenbrand <david@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-mips@...r.kernel.org, kvm@...r.kernel.org,
        kvm-ppc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Peter Feiner <pfeiner@...gle.com>,
        Peter Shier <pshier@...gle.com>,
        Junaid Shahid <junaids@...gle.com>,
        Christoffer Dall <christoffer.dall@....com>
Subject: Re: [PATCH 09/21] KVM: x86/mmu: Separate the memory caches for shadow
 pages and gfn arrays

On Fri, Jun 5, 2020 at 2:39 PM Sean Christopherson
<sean.j.christopherson@...el.com> wrote:
>
> Use separate caches for allocating shadow pages versus gfn arrays.  This
> sets the stage for specifying __GFP_ZERO when allocating shadow pages
> without incurring extra cost for gfn arrays.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
Reviewed-by: Ben Gardon <bgardon@...gle.com>
> ---
>  arch/x86/include/asm/kvm_host.h |  3 ++-
>  arch/x86/kvm/mmu/mmu.c          | 15 ++++++++++-----
>  2 files changed, 12 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 16347b050754..e7a427547557 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -636,7 +636,8 @@ struct kvm_vcpu_arch {
>         struct kvm_mmu *walk_mmu;
>
>         struct kvm_mmu_memory_cache mmu_pte_list_desc_cache;
> -       struct kvm_mmu_memory_cache mmu_page_cache;
> +       struct kvm_mmu_memory_cache mmu_shadow_page_cache;
> +       struct kvm_mmu_memory_cache mmu_gfn_array_cache;
>         struct kvm_mmu_memory_cache mmu_page_header_cache;
>
>         /*
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 451e0365e5dd..d245acece3cd 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -1108,8 +1108,12 @@ static int mmu_topup_memory_caches(struct kvm_vcpu *vcpu)
>                                    1 + PT64_ROOT_MAX_LEVEL + PTE_PREFETCH_NUM);
>         if (r)
>                 return r;
> -       r = mmu_topup_memory_cache(&vcpu->arch.mmu_page_cache,
> -                                  2 * PT64_ROOT_MAX_LEVEL);
> +       r = mmu_topup_memory_cache(&vcpu->arch.mmu_shadow_page_cache,
> +                                  PT64_ROOT_MAX_LEVEL);
> +       if (r)
> +               return r;
> +       r = mmu_topup_memory_cache(&vcpu->arch.mmu_gfn_array_cache,
> +                                  PT64_ROOT_MAX_LEVEL);
>         if (r)
>                 return r;
>         return mmu_topup_memory_cache(&vcpu->arch.mmu_page_header_cache,
> @@ -1119,7 +1123,8 @@ static int mmu_topup_memory_caches(struct kvm_vcpu *vcpu)
>  static void mmu_free_memory_caches(struct kvm_vcpu *vcpu)
>  {
>         mmu_free_memory_cache(&vcpu->arch.mmu_pte_list_desc_cache);
> -       mmu_free_memory_cache(&vcpu->arch.mmu_page_cache);
> +       mmu_free_memory_cache(&vcpu->arch.mmu_shadow_page_cache);
> +       mmu_free_memory_cache(&vcpu->arch.mmu_gfn_array_cache);
>         mmu_free_memory_cache(&vcpu->arch.mmu_page_header_cache);
>  }
>
> @@ -2096,9 +2101,9 @@ static struct kvm_mmu_page *kvm_mmu_alloc_page(struct kvm_vcpu *vcpu, int direct
>         struct kvm_mmu_page *sp;
>
>         sp = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_header_cache);
> -       sp->spt = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_cache);
> +       sp->spt = mmu_memory_cache_alloc(&vcpu->arch.mmu_shadow_page_cache);
>         if (!direct)
> -               sp->gfns = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_cache);
> +               sp->gfns = mmu_memory_cache_alloc(&vcpu->arch.mmu_gfn_array_cache);
>         set_page_private(virt_to_page(sp->spt), (unsigned long)sp);
>
>         /*
> --
> 2.26.0
>