linux-kernel - Re: [PATCH v10 041/108] KVM: x86/tdp_mmu: refactor kvm_tdp_mmu

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Message-ID: <f9dcc09e6569b2d47c039a44bfb83c22e30365bb.camel@intel.com>
Date:   Wed, 16 Nov 2022 09:42:34 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>
CC:     "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "Shahar, Sagi" <sagis@...gle.com>,
        "Aktas, Erdem" <erdemaktas@...gle.com>,
        "isaku.yamahata@...il.com" <isaku.yamahata@...il.com>,
        "dmatlack@...gle.com" <dmatlack@...gle.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>
Subject: Re: [PATCH v10 041/108] KVM: x86/tdp_mmu: refactor kvm_tdp_mmu_map()

On Sat, 2022-10-29 at 23:22 -0700, isaku.yamahata@...el.com wrote:
> From: Isaku Yamahata <isaku.yamahata@...el.com>
> 
> Factor out non-leaf SPTE population logic from kvm_tdp_mmu_map().  MapGPA
> hypercall needs to populate non-leaf SPTE to record which GPA, private or
> shared, is allowed in the leaf EPT entry.

Is this patch still valid/needed since you have changed to use XArray to store
whether GFN is private or shared?

> 
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---
>  arch/x86/kvm/mmu/tdp_mmu.c | 26 +++++++++++++++++++-------
>  1 file changed, 19 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index 3325633b1cb5..11b0ec8aebe2 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -1157,6 +1157,24 @@ static int tdp_mmu_link_sp(struct kvm *kvm, struct tdp_iter *iter,
>  	return 0;
>  }
>  
> +static int tdp_mmu_populate_nonleaf(struct kvm_vcpu *vcpu, struct tdp_iter *iter,
> +				    bool account_nx)
> +{
> +	struct kvm_mmu_page *sp;
> +	int ret;
> +
> +	KVM_BUG_ON(is_shadow_present_pte(iter->old_spte), vcpu->kvm);
> +	KVM_BUG_ON(is_removed_spte(iter->old_spte), vcpu->kvm);
> +
> +	sp = tdp_mmu_alloc_sp(vcpu);
> +	tdp_mmu_init_child_sp(sp, iter);
> +
> +	ret = tdp_mmu_link_sp(vcpu->kvm, iter, sp, account_nx, true);
> +	if (ret)
> +		tdp_mmu_free_sp(sp);
> +	return ret;
> +}
> +
>  /*
>   * Handle a TDP page fault (NPT/EPT violation/misconfiguration) by installing
>   * page tables and SPTEs to translate the faulting guest physical address.
> @@ -1165,7 +1183,6 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
>  {
>  	struct kvm_mmu *mmu = vcpu->arch.mmu;
>  	struct tdp_iter iter;
> -	struct kvm_mmu_page *sp;
>  	int ret;
>  
>  	kvm_mmu_hugepage_adjust(vcpu, fault);
> @@ -1211,13 +1228,8 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
>  			if (is_removed_spte(iter.old_spte))
>  				break;
>  
> -			sp = tdp_mmu_alloc_sp(vcpu);
> -			tdp_mmu_init_child_sp(sp, &iter);
> -
> -			if (tdp_mmu_link_sp(vcpu->kvm, &iter, sp, account_nx, true)) {
> -				tdp_mmu_free_sp(sp);
> +			if (tdp_mmu_populate_nonleaf(vcpu, &iter, account_nx))
>  				break;
> -			}
>  		}
>  	}
>