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

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Date:   Fri, 9 Sep 2022 11:07:59 +0100
From:   Oliver Upton <oliver.upton@...ux.dev>
To:     David Matlack <dmatlack@...gle.com>
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 Wed, Sep 07, 2022 at 01:57:17PM -0700, David Matlack wrote:
> 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.

Yup, I'll toss those in the next spin.

> > -		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.

Good catch, I'll drop the TABLE_POST flag there as well.

Appreciate the reviews on the series.

--
Thanks,
Oliver