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

[Christoph Hellwig]

On Wed, Jan 30, 2019 at 10:55:43AM -0500, Jerome Glisse wrote:
> Even outside GPU driver, device driver like RDMA just want to share their
> doorbell to other device and they do not want to see those doorbell page
> use in direct I/O or anything similar AFAICT.

At least Mellanox HCA support and inline data feature where you
can copy data directly into the BAR.  For something like a usrspace
NVMe target it might be very useful to do direct I/O straight into
the BAR for that.