Re: [PATCH v1 1/4] mm/hmm: HMM API for P2P DMA to device zone pages

[Jason Gunthorpe]

On Thu, Oct 17, 2024 at 12:58:48PM +1100, Alistair Popple wrote:

> Actually I think the rule should be don't look at the page at
> all. hmm_range_fault() is about mirroring PTEs, no assumption should
> even be made about the existence or otherwise of a struct page.

We are not there yet..
 
> > We don't need to enforce, it we don't know what else the driver will
> > want to use that P2P page for after all. It might stick it in a VMA
> > for some unrelated reason.
> 
> And wouldn't that touch the refcount and therefore be wrong?

I mean the originating driver would do that

Jason