Re: [PATCH v5 10/14] KVM: arm64: Split init and set for table PTE

[Oliver Upton <oliver.upton@linux.dev>]

On Wed, Nov 09, 2022 at 02:26:26PM -0800, Ben Gardon wrote:
> On Mon, Nov 7, 2022 at 1:58 PM Oliver Upton <oliver.upton@linux.dev> wrote:
> >
> > Create a helper to initialize a table and directly call
> > smp_store_release() to install it (for now). Prepare for a subsequent
> > change that generalizes PTE writes with a helper.
> >
> > Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
> > ---
> >  arch/arm64/kvm/hyp/pgtable.c | 20 ++++++++++----------
> >  1 file changed, 10 insertions(+), 10 deletions(-)
> >
> > diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> > index a34e2050f931..f4dd77c6c97d 100644
> > --- a/arch/arm64/kvm/hyp/pgtable.c
> > +++ b/arch/arm64/kvm/hyp/pgtable.c
> > @@ -136,16 +136,13 @@ static void kvm_clear_pte(kvm_pte_t *ptep)
> >         WRITE_ONCE(*ptep, 0);
> >  }
> >
> > -static void kvm_set_table_pte(kvm_pte_t *ptep, kvm_pte_t *childp,
> > -                             struct kvm_pgtable_mm_ops *mm_ops)
> > +static kvm_pte_t kvm_init_table_pte(kvm_pte_t *childp, struct kvm_pgtable_mm_ops *mm_ops)
> >  {
> > -       kvm_pte_t old = *ptep, pte = kvm_phys_to_pte(mm_ops->virt_to_phys(childp));
> > +       kvm_pte_t pte = kvm_phys_to_pte(mm_ops->virt_to_phys(childp));
> >
> >         pte |= FIELD_PREP(KVM_PTE_TYPE, KVM_PTE_TYPE_TABLE);
> >         pte |= KVM_PTE_VALID;
> > -
> > -       WARN_ON(kvm_pte_valid(old));
> 
> Is there any reason to drop this warning?

It is (eventually) superseded by a WARN() when a PTE isn't locked in
stage2_make_pte(), but that isn't obvious in this patch alone.

--
Thanks,
Oliver
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