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

Oliver Upton
2022-10-10T03:58:40Z

Hey Ricardo,

On Tue, Sep 13, 2022 at 05:20:11PM -0700, Ricardo Koller wrote:

[...]

> > diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> > index d8127c25424c..5c0c8028d71c 100644
> > --- a/arch/arm64/kvm/hyp/pgtable.c
> > +++ b/arch/arm64/kvm/hyp/pgtable.c
> > @@ -763,17 +763,21 @@ static int stage2_map_walker_try_leaf(u64 addr, u64 end, u32 level,
> > return 0;
> > }
> >
> > +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)
> > - 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);
> >
> > /*
> > @@ -782,8 +786,13 @@ static int stage2_map_walk_table_pre(u64 addr, u64 end, u32 level,
> > * individually.
> > */
> > kvm_call_hyp(__kvm_tlb_flush_vmid, data->mmu);
> > - data->anchor = ptep;
> > - return 0;
> > +
> > + ret = stage2_map_walk_leaf(addr, end, level, ptep, data);
>
> I think this always ends up calling stage2_map_walker_try_leaf() (at
> least it should). In that case, I think it might be clearer to do so, as
> the intention is to just install a block.

Yikes, I missed this in v2. I do agree with your point, it reads a bit
odd to call something that could reinstall a table.

Picked up the fix for v3. Thanks!

--
Best,
Oliver