Enabling peer to peer device transactions for PCIe devices

[Jason Gunthorpe]

On Wed, Nov 23, 2016 at 10:40:47AM -0800, Dan Williams wrote:

> I don't think that was designed for the case where the backing memory
> is a special/static physical address range rather than anonymous
> "System RAM", right?

The hardware doesn't care where the memory is. ODP is just a generic
mechanism to provide demand-fault behavior for a mirrored page table.

ODP has the same issue as everything else, it needs to translate a
page table entry into a DMA address, and we have no API to do that
when the page table points to peer-peer memory.

Jason