On 2016-11-25 02:34 PM, Jason Gunthorpe wrote: > On Fri, Nov 25, 2016 at 12:16:30PM -0500, Serguei Sagalovitch wrote: > >> b) Allocation may not have CPU address at all - only GPU one. > But you don't expect RDMA to work in the case, right? > > GPU people need to stop doing this windowed memory stuff :) GPU could perfectly access all VRAM. It is only issue for p2p without special interconnect and CPU access. Strictly speaking as long as we have "bus address" we could have RDMA but I agreed that for RDMA we could/should(?) always "request" CPU address (I hope that we could forget about 32-bit application :-)).
BTW/FYI: About CPU access: Some user-level API is mainly handle based so there is no need for CPU access by default. About "visible" / non-visible VRAM parts: I assume that going forward we will be able to get rid from it completely as soon as support for resizable PCI BAR will be implemented and/or old/current h/w will become obsolete.