[RFC PATCH 3/5] mm/vma: add support for peer to peer to device vma

[Logan Gunthorpe]

On 2019-01-30 10:44 a.m., Jason Gunthorpe wrote:
> I don't see why a special case with a VMA is really that different.

Well one *really* big difference is the VMA changes necessarily expose
specialized new functionality to userspace which has to be supported
forever and may be difficult to change. The p2pdma code is largely
in-kernel and we can rework and change the interfaces all we want as we
improve our struct page infrastructure.

I'd also argue that p2pdma isn't nearly as specialized as this VMA thing
and can be used pretty generically to do other things. Though, the other
ideas we've talked about doing are pretty far off and may have other
challenges.

Logan