Re: [PATCH v1 03/14] mm: add iomem vma selection for memory migration

On Thu, Aug 26, 2021 at 06:27:31PM -0400, Felix Kuehling wrote:

I think we're missing something here. As far as I can tell, all the work
we did first with DEVICE_GENERIC and now DEVICE_PUBLIC always used
normal pages. Are we missing something in our driver code that would
make these PTEs special? I don't understand how that can be, because
driver code is not really involved in updating the CPU mappings. Maybe
it's something we need to do in the migration helpers.

It looks like I'm totally misunderstanding what you are adding here
then.  Why do we need any special treatment at all for memory that
has normal struct pages and is part of the direct kernel map?