Re: [PATCH v12 04/20] KVM: pfncache: add a mark-dirty helper

[Paul Durrant]

On 09/02/2024 15:58, Sean Christopherson wrote:
> On Mon, Jan 15, 2024, Paul Durrant wrote:
> > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> > index 7e7fd25b09b3..f3bb9e0a81fe 100644
> > --- a/include/linux/kvm_host.h
> > +++ b/include/linux/kvm_host.h
> > @@ -1399,6 +1399,17 @@ int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, unsigned long len);
> >    */
> >   void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc);
> >   
> > +/**
> > + * kvm_gpc_mark_dirty - mark a cached page as dirty.
> > + *
> > + * @gpc:	   struct gfn_to_pfn_cache object.
> > + */
> > +static inline void kvm_gpc_mark_dirty(struct gfn_to_pfn_cache *gpc)
> > +{
> > +	lockdep_assert_held(&gpc->lock);
> > +	mark_page_dirty_in_slot(gpc->kvm, gpc->memslot, gpc->gpa >> PAGE_SHIFT);
>
> Can you opportunistically have this pre-check gpc->memslot?  __kvm_gpc_refresh()
> should nullify gpc->memslot when using an hva.  That way, you don't need to
> explicitly check for the "invalid gfn" case here (or you could, but WARN_ON_ONCE()
> if the memslot is non-NULL and the gfn is invalid?).

Ok, sure.