Re: [RFC PATCH] kvm: Use huge pages for DAX-backed files

[Barret Rhoden <brho-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>]

On 2018-11-06 at 11:19 Paolo Bonzini <pbonzini-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> > void kvm_set_pfn_dirty(kvm_pfn_t pfn)
> > {
> >         if (!kvm_is_reserved_pfn(pfn)) {
> >                 struct page *page = pfn_to_page(pfn);
> > 
> >                 if (!PageReserved(page))
> >                         SetPageDirty(page);
> >         }
> > }
> > 
> > I think we want to SetPageDirty for DAX, so making PageReserved be true
> > for DAX seems like the way to go, or we'll need more KVM-specific
> > changes.  Apologies is this was discussed in the previous thread on this
> > topic and is redundant.  
> 
> Isn't it the opposite?  We want SetPageDirty, so PageReserved must _not_
> be true.

You're right on that, I had it backwards.  The other DAX work is making
it so that DAX pages are not reserved, so the only extra '!' was in my
head.  

Thanks,

Barret