On Thu, Jan 12, 2017 at 10:11:29AM -0500, Jerome Glisse wrote:

On Wed, Jan 11, 2017 at 10:54:39PM -0600, Stephen Bates wrote:

quoted

quoted

What we want is for RDMA, O_DIRECT, etc to just work with special VMAs
(ie. at least those backed with ZONE_DEVICE memory). Then
GPU/NVME/DAX/whatever drivers can just hand these VMAs to userspace
(using whatever interface is most appropriate) and userspace can do what
it pleases with them. This makes _so_ much sense and actually largely
already works today (as demonstrated by iopmem).

So i say let solve the IOMMU issue first and let everyone use it in their
own way with their device. I do not think we can share much more than
that.

Solve it for the easy ZONE_DIRECT/etc case then.

Jason