On Fri, Dec 9, 2022 at 3:04 PM David Matlack <dmatlack@xxxxxxxxxx> wrote:
>
> On Tue, Dec 06, 2022 at 05:35:56PM +0000, Ben Gardon wrote:
> > In continuing to factor the rmap out of mmu.c, move the rmap_iterator
> > and associated functions and macros into rmap.(c|h).
> >
> > No functional change intended.
> >
> > Signed-off-by: Ben Gardon <bgardon@xxxxxxxxxx>
> > ---
> > arch/x86/kvm/mmu/mmu.c | 76 -----------------------------------------
> > arch/x86/kvm/mmu/rmap.c | 61 +++++++++++++++++++++++++++++++++
> > arch/x86/kvm/mmu/rmap.h | 18 ++++++++++
> > 3 files changed, 79 insertions(+), 76 deletions(-)
> >
> [...]
> > diff --git a/arch/x86/kvm/mmu/rmap.h b/arch/x86/kvm/mmu/rmap.h
> > index 059765b6e066..13b265f3a95e 100644
> > --- a/arch/x86/kvm/mmu/rmap.h
> > +++ b/arch/x86/kvm/mmu/rmap.h
> > @@ -31,4 +31,22 @@ void free_pte_list_desc(struct pte_list_desc *pte_list_desc);
> > void pte_list_remove(u64 *spte, struct kvm_rmap_head *rmap_head);
> > unsigned int pte_list_count(struct kvm_rmap_head *rmap_head);
> >
> > +/*
> > + * Used by the following functions to iterate through the sptes linked by a
> > + * rmap. All fields are private and not assumed to be used outside.
> > + */
> > +struct rmap_iterator {
> > + /* private fields */
> > + struct pte_list_desc *desc; /* holds the sptep if not NULL */
> > + int pos; /* index of the sptep */
> > +};
> > +
> > +u64 *rmap_get_first(struct kvm_rmap_head *rmap_head,
> > + struct rmap_iterator *iter);
> > +u64 *rmap_get_next(struct rmap_iterator *iter);
> > +
> > +#define for_each_rmap_spte(_rmap_head_, _iter_, _spte_) \
> > + for (_spte_ = rmap_get_first(_rmap_head_, _iter_); \
> > + _spte_; _spte_ = rmap_get_next(_iter_))
> > +
>
> I always found these function names and kvm_rmap_head confusing since
> they are about iterating through the pte_list_desc data structure. The
> rmap (gfn -> list of sptes) is a specific application of the
> pte_list_desc structure, but not the only application. There's also
> parent_ptes in struct kvm_mmu_page, which is not an rmap, just a plain
> old list of ptes.
>
> While you are refactoring this code, what do you think about doing the
> following renames?
>
> struct kvm_rmap_head -> struct pte_list_head
> struct rmap_iterator -> struct pte_list_iterator
> rmap_get_first() -> pte_list_get_first()
> rmap_get_next() -> pte_list_get_next()
> for_each_rmap_spte() -> for_each_pte_list_entry()
>
> Then we can reserve the term "rmap" just for the actual rmap
> (slot->arch.rmap), and code that deals with sp->parent_ptes will become
> a lot more clear IMO (because it will not longer mention rmap).
>
> e.g. We go from this:
>
> struct rmap_iterator iter;
> u64 *sptep;
>
> for_each_rmap_spte(&sp->parent_ptes, &iter, sptep) {
> ...
> }
>
> To this:
>
> struct pte_list_iterator iter;
> u64 *sptep;
>
> for_each_pte_list_entry(&sp->parent_ptes, &iter, sptep) {
> ...
> }
I like this suggestion, and I do think it'll make things more
readable. It's going to be a huge patch to rename all the instances of
kvm_rmap_head, but it's probably worth it.
