On Thu, Oct 17, 2024 at 04:58:12AM -0700, Christoph Hellwig wrote: > On Wed, Oct 16, 2024 at 02:44:45PM -0300, Jason Gunthorpe wrote: > > > > FWIW, I've been expecting this series to be rebased on top of Leon's > > > > new DMA API series so it doesn't have this issue.. > > > > > > That's not going to make a difference at this level. > > > > I'm not sure what you are asking then. > > > > Patch 2 does pci_p2pdma_add_resource() and so a valid struct page with > > a P2P ZONE_DEVICE type exists, and that gets returned back to the > > hmm/odp code. > > > > Today odp calls dma_map_page() which only works by chance in limited > > cases. With Leon's revision it will call hmm_dma_map_pfn() -> > > dma_iova_link() which does call pci_p2pdma_map_type() and should do > > the right thing. > > Again none of this affects the code posted here. It reshuffles the > callers but has no direct affect on the patches posted here. I didn't realize till last night that Leon's series did not have P2P support. What I'm trying to say is that this is a multi-series project. A followup based on Leon's initial work will get the ODP DMA mapping path able to support ZONE_DEVICE P2P pages. Once that is done, this series sits on top. This series is only about hmm and effectively allows hmm_range_fault() to return a ZONE_DEVICE P2P page. Yonatan should explain this better in the cover letter and mark it as a RFC series. So, I know we are still figuring out the P2P support on the DMA API side, but my expectation for hmm is that hmm_range_fault() returing a ZONE_DEVICE P2P page is going to be what we want. > (and the current DMA series lacks P2P support, I'm trying to figure > out how to properly handle it at the moment). Yes, I see, I looked through those patches last night and there is a gap there. Broadly I think whatever flow NVMe uses for P2P will apply to ODP as well. Thanks, Jason
