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

Ben Gardon
2020-06-09T23:56:31Z

On Fri, Jun 5, 2020 at 2:39 PM Sean Christopherson
<sean.j.christopherson@intel.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@intel.com>
Reviewed-by: Ben Gardon <bgardon@google.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
>