Re: [PATCH v3 10/21] KVM: arm64: Add support for stage-2 page-aging in generic page-table

Will Deacon
2020-09-03T16:49:51Z

On Thu, Sep 03, 2020 at 02:33:22PM +1000, Gavin Shan wrote:
> On 8/25/20 7:39 PM, Will Deacon wrote:
> > Add stage-2 mkyoung(), mkold() and is_young() operations to the generic
> > page-table code.
> >
> > Cc: Marc Zyngier <maz@kernel.org>
> > Cc: Quentin Perret <qperret@google.com>
> > Signed-off-by: Will Deacon <will@kernel.org>
> > ---
> > arch/arm64/include/asm/kvm_pgtable.h | 38 ++++++++++++
> > arch/arm64/kvm/hyp/pgtable.c | 86 ++++++++++++++++++++++++++++
> > 2 files changed, 124 insertions(+)

[...]

> > +static int stage2_update_leaf_attrs(struct kvm_pgtable *pgt, u64 addr,
> > + u64 size, kvm_pte_t attr_set,
> > + kvm_pte_t attr_clr, kvm_pte_t *orig_pte)
> > +{
> > + int ret;
> > + kvm_pte_t attr_mask = KVM_PTE_LEAF_ATTR_LO | KVM_PTE_LEAF_ATTR_HI;
> > + struct stage2_attr_data data = {
> > + .attr_set = attr_set & attr_mask,
> > + .attr_clr = attr_clr & attr_mask,
> > + };
> > + struct kvm_pgtable_walker walker = {
> > + .cb = stage2_attr_walker,
> > + .arg = &data,
> > + .flags = KVM_PGTABLE_WALK_LEAF,
> > + };
> > +
> > + ret = kvm_pgtable_walk(pgt, addr, size, &walker);
> > + if (ret)
> > + return ret;
> > +
> > + if (orig_pte)
> > + *orig_pte = data.pte;
> > + return 0;
> > +}
> > +
>
> The @size is always 1 from the caller, which means the parameter
> can be dropped from stage2_update_leaf_attrs(). In the meanwhile,
> we don't know the page is mapped by PUD, PMD or PTE. So to have
> fixed value ("1") looks meaningless.

I add extra callers later on, for example kvm_pgtable_stage2_wrprotect(),
which pass a size, so it's needed for that.

Will