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

From: Barret Rhoden
Date: Tue Nov 06 2018 - 11:22:51 EST


On 2018-11-06 at 11:19 Paolo Bonzini <pbonzini@xxxxxxxxxx> 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