linux-kernel - Re: [PATCH 02/14] KVM: arm64: Tear down unlinked stage-2 subtree after break-before-make

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Message-ID: <YxkFrSmSKdBFEoZp@google.com>
Date:   Wed, 7 Sep 2022 13:57:17 -0700
From:   David Matlack <dmatlack@...gle.com>
To:     Oliver Upton <oliver.upton@...ux.dev>
Cc:     Marc Zyngier <maz@...nel.org>, James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Quentin Perret <qperret@...gle.com>,
        Ricardo Koller <ricarkol@...gle.com>,
        Reiji Watanabe <reijiw@...gle.com>,
        Ben Gardon <bgardon@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Gavin Shan <gshan@...hat.com>, Peter Xu <peterx@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/14] KVM: arm64: Tear down unlinked stage-2 subtree
 after break-before-make

On Tue, Aug 30, 2022 at 07:41:20PM +0000, Oliver Upton wrote:
[...]
>  
> +static int stage2_map_walk_leaf(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
> +				struct stage2_map_data *data);
> +
>  static int stage2_map_walk_table_pre(u64 addr, u64 end, u32 level,
>  				     kvm_pte_t *ptep,
>  				     struct stage2_map_data *data)
>  {
> -	if (data->anchor)

Should @anchor and @childp be removed from struct stage2_map_data? This
commit removes the only remaining references to them.

> -		return 0;
> +	struct kvm_pgtable_mm_ops *mm_ops = data->mm_ops;
> +	kvm_pte_t *childp = kvm_pte_follow(*ptep, mm_ops);
> +	struct kvm_pgtable *pgt = data->mmu->pgt;
> +	int ret;
>  
>  	if (!stage2_leaf_mapping_allowed(addr, end, level, data))
>  		return 0;
>  
> -	data->childp = kvm_pte_follow(*ptep, data->mm_ops);
>  	kvm_clear_pte(ptep);
>  
>  	/*
[...]
>  static int stage2_map_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
>  			     enum kvm_pgtable_walk_flags flag, void * const arg)
> @@ -883,11 +849,9 @@ static int stage2_map_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
>  		return stage2_map_walk_table_pre(addr, end, level, ptep, data);
>  	case KVM_PGTABLE_WALK_LEAF:
>  		return stage2_map_walk_leaf(addr, end, level, ptep, data);
> -	case KVM_PGTABLE_WALK_TABLE_POST:
> -		return stage2_map_walk_table_post(addr, end, level, ptep, data);

kvm_pgtable_stage2_set_owner() still uses stage2_map_walker() with
KVM_PGTABLE_WALK_TABLE_POST.