Am 23.05.19 um 11:43 schrieb Christoph Hellwig: > [CAUTION: External Email] > > On Thu, May 23, 2019 at 08:12:18AM +0000, Koenig, Christian wrote: >>> Are you DMA-mapping the addresses outside the P2PDMA code? If so there's >>> a huge mismatch with the existing users of P2PDMA (nvme-fabrics). If >>> you're not dma-mapping then I can't see how it could work because the >>> IOMMU should reject any requests to access those addresses. >> Well, we are using the DMA API (dma_map_resource) for this. If the P2P >> code is not using this then I would rather say that the P2P code is >> actually broken. >> >> Adding Christoph as well, cause he is usually the one discussion stuff >> like that with me. > Heh. Actually dma_map_resource-ish APIs are the right thing to do, > but I'm not sure how you managed to be able to use it for PCIe P2P > yet, as it fails to account for any difference in the PCIe level > "physical" address with the hosts view of "physical" addresses. > > Do these offsets now how up on AMD platforms? Do you adjust for them > elsewhere? I don't adjust the address manually anywhere. I just call dma_map_resource() and use the resulting DMA address to access the other devices PCI BAR. At least on my test system (AMD CPU + AMD GPUs) this seems to work totally fine. Currently trying to find time and an Intel box to test it there as well. Regards, Christian.
