linux-kernel - Re: [PATCH v5 2/7] KVM: x86/mmu: Rename NX huge pages fields/functions for consistency

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Date:   Mon, 10 Oct 2022 10:05:29 +0800
From:   Yan Zhao <yan.y.zhao@...el.com>
To:     Sean Christopherson <seanjc@...gle.com>
CC:     Paolo Bonzini <pbonzini@...hat.com>, <kvm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Mingwei Zhang <mizhang@...gle.com>,
        "David Matlack" <dmatlack@...gle.com>,
        Ben Gardon <bgardon@...gle.com>
Subject: Re: [PATCH v5 2/7] KVM: x86/mmu: Rename NX huge pages
 fields/functions for consistency

On Fri, Sep 30, 2022 at 11:48:49PM +0000, Sean Christopherson wrote:
<...>
> -static void kvm_recover_nx_lpages(struct kvm *kvm)
> +static void kvm_recover_nx_huge_pages(struct kvm *kvm)
>  {
>  	unsigned long nx_lpage_splits = kvm->stat.nx_lpage_splits;
>  	int rcu_idx;
> @@ -6833,23 +6834,25 @@ static void kvm_recover_nx_lpages(struct kvm *kvm)
>  	ratio = READ_ONCE(nx_huge_pages_recovery_ratio);
>  	to_zap = ratio ? DIV_ROUND_UP(nx_lpage_splits, ratio) : 0;
>  	for ( ; to_zap; --to_zap) {
> -		if (list_empty(&kvm->arch.lpage_disallowed_mmu_pages))
> +		if (list_empty(&kvm->arch.possible_nx_huge_pages))
>  			break;
>  
>  		/*
>  		 * We use a separate list instead of just using active_mmu_pages
> -		 * because the number of lpage_disallowed pages is expected to
> -		 * be relatively small compared to the total.
> +		 * because the number of shadow pages that be replaced with an
> +		 * NX huge page is expected to be relatively small compared to
> +		 * the total number of shadow pages.  And because the TDP MMU
> +		 * doesn't use active_mmu_pages.
>  		 */
> -		sp = list_first_entry(&kvm->arch.lpage_disallowed_mmu_pages,
> +		sp = list_first_entry(&kvm->arch.possible_nx_huge_pages,
>  				      struct kvm_mmu_page,
> -				      lpage_disallowed_link);
> -		WARN_ON_ONCE(!sp->lpage_disallowed);
> +				      possible_nx_huge_page_link);
> +		WARN_ON_ONCE(!sp->nx_huge_page_disallowed);
>  		if (is_tdp_mmu_page(sp)) {
>  			flush |= kvm_tdp_mmu_zap_sp(kvm, sp);
>  		} else {
>  			kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list);
> -			WARN_ON_ONCE(sp->lpage_disallowed);
> +			WARN_ON_ONCE(sp->nx_huge_page_disallowed);
Can this WARN_ON_ONCE(sp->nx_huge_page_disallowed) also be applied to
tdp mmu case as it holds write lock now?

Thanks
Yan
>  		}
>  
>  		if (need_resched() || rwlock_needbreak(&kvm->mmu_lock)) {
> @@ -6870,7 +6873,7 @@ static void kvm_recover_nx_lpages(struct kvm *kvm)
>  	srcu_read_unlock(&kvm->srcu, rcu_idx);
>  }
>