On 24/06/21 12:17, Nicholas Piggin wrote:

quoted

If all callers were updated that is one thing, but from the changelog
it sounds like that would not happen and there would be some gfn_to_pfn
users left over.

But yes in the end you would either need to make gfn_to_pfn never return
a page found via follow_pte, or change all callers to the new way. If
the plan is for the latter then I guess that's fine.

Actually in that case anyway I don't see the need -- the existence of
gfn_to_pfn is enough to know it might be buggy. It can just as easily
be grepped for as kvm_pfn_page_unwrap.

Sure, but that would leave us with longer function names 
(gfn_to_pfn_page* instead of gfn_to_pfn*).  So the "safe" use is the one 
that looks worse and the unsafe use is the one that looks safe.

And are gfn_to_page cases also
vulernable to the same issue?

No, they're just broken for the VM_IO|VM_PFNMAP case.

Paolo

So I think it could be marked deprecated or something if not everything
will be converted in the one series, and don't need to touch all that
arch code with this patch.