[PATCH 09/17] KVM: arm64: Move VMA-related information to kvm_s2_fault_vma_info

[Fuad Tabba]

Hi Joey,

First, thanks for the reviews and the comments on my series. You're
right about my changes wrongly editing "page". I wanted it to be as
mechanical as possible to make it easy to review, but it ended up
being too mechanical.

<snip>

> > -     /* Mark the fault->page dirty only if the fault is handled successfully */
> > -     if (fault->writable && !ret)
> > -             mark_page_dirty_in_slot(kvm, s2fd->memslot, get_canonical_gfn(s2fd, fault));
> > +     /* Mark the page dirty only if the fault is handled successfully */
> > +     if (fault->writable && !ret) {
> > +             phys_addr_t ipa = gfn_to_gpa(get_canonical_gfn(s2fd, s2vi));
> > +             ipa &= ~(mapping_size - 1);
> > +             mark_page_dirty_in_slot(kvm, s2fd->memslot, gpa_to_gfn(ipa));
>
> I don't understand this change, why do we need to mask stuff now?

Let me see if _I_ understand it (Marc, please correct me if I'm wrong).

Before this patch, fault->gfn and fault->vma_pagesize were mutable,
and transparent_hugepage_adjust() modified both directly. In addition
to this being confusing (which gfn is this: the host /canonical or the
nested one?), it made it more difficult to separate the logic.

So, to mark a dirty page, it did this:
-             mark_page_dirty_in_slot(kvm, s2fd->memslot,
get_canonical_gfn(s2fd, fault));

which relied on the old struct fault to calculate the canonical gfn
using the (magically) THP adjusted fault->vma_pagesize.

Now that fault (or s2vi, its successor in this case) isn't mutable, we
need to get the canonical gfn using the host mapping size.

Cheers,
/fuad