linux-kernel - Re: [RFC PATCH v5 047/104] KVM: x86/mmu: add a private pointer to struct kvm_mmu

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Date:   Thu, 07 Apr 2022 11:43:30 +1200
From:   Kai Huang <kai.huang@...el.com>
To:     isaku.yamahata@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     isaku.yamahata@...il.com, Paolo Bonzini <pbonzini@...hat.com>,
        Jim Mattson <jmattson@...gle.com>, erdemaktas@...gle.com,
        Connor Kuehl <ckuehl@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: Re: [RFC PATCH v5 047/104] KVM: x86/mmu: add a private pointer to
 struct kvm_mmu_page

On Fri, 2022-03-04 at 11:49 -0800, isaku.yamahata@...el.com wrote:
> From: Isaku Yamahata <isaku.yamahata@...el.com>
> 
> Add a private pointer to kvm_mmu_page for private EPT.
> 
> To resolve KVM page fault on private GPA, it will allocate additional page
> for Secure EPT in addition to private EPT.  Add memory allocator for it and
> topup its memory allocator before resolving KVM page fault similar to
> shared EPT page.  Allocation of those memory will be done for TDP MMU by
> alloc_tdp_mmu_page().  Freeing those memory will be done for TDP MMU on
> behalf of kvm_tdp_mmu_zap_all() called by kvm_mmu_zap_all().  Private EPT
> page needs to carry one more page used for Secure EPT in addition to the
> private EPT page.  Add private pointer to struct kvm_mmu_page for that
> purpose and Add helper functions to allocate/free a page for Secure EPT.
> Also add helper functions to check if a given kvm_mmu_page is private.
> 
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---
>  arch/x86/include/asm/kvm_host.h |  1 +
>  arch/x86/kvm/mmu/mmu.c          |  9 ++++
>  arch/x86/kvm/mmu/mmu_internal.h | 84 +++++++++++++++++++++++++++++++++
>  arch/x86/kvm/mmu/tdp_mmu.c      |  3 ++
>  4 files changed, 97 insertions(+)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index fcab2337819c..0c8cc7d73371 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -689,6 +689,7 @@ struct kvm_vcpu_arch {
>  	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;
> +	struct kvm_mmu_memory_cache mmu_private_sp_cache;
>  
>  	/*
>  	 * QEMU userspace and the guest each have their own FPU state.
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 6e9847b1124b..8def8b97978f 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -758,6 +758,13 @@ static int mmu_topup_shadow_page_cache(struct kvm_vcpu *vcpu)
>  	struct kvm_mmu_memory_cache *mc = &vcpu->arch.mmu_shadow_page_cache;
>  	int start, end, i, r;
>  
> +	if (kvm_gfn_stolen_mask(vcpu->kvm)) {

Please get rid of kvm_gfn_stolen_mask().

> +		r = kvm_mmu_topup_memory_cache(&vcpu->arch.mmu_private_sp_cache,
> +					       PT64_ROOT_MAX_LEVEL);
> +		if (r)
> +			return r;
> +	}
> +
>  	if (shadow_init_value)
>  		start = kvm_mmu_memory_cache_nr_free_objects(mc);
>