On Tue, Jun 22, 2021 at 6:28 PM Jason Gunthorpe [off-list ref] wrote:

On Tue, Jun 22, 2021 at 05:24:08PM +0200, Christian König wrote:

quoted

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I will take two GAUDI devices and use one as an exporter and one as an
importer. I want to see that the solution works end-to-end, with real
device DMA from importer to exporter.

I can tell you it doesn't. Stuffing physical addresses directly into
the sg list doesn't involve any of the IOMMU code so any configuration
that requires IOMMU page table setup will not work.

Sure it does. See amdgpu_vram_mgr_alloc_sgt:

        amdgpu_res_first(res, offset, length, &cursor);

         ^^^^^^^^^^

I'm not talking about the AMD driver, I'm talking about this patch.

+               bar_address = hdev->dram_pci_bar_start +
+                               (pages[cur_page] - prop->dram_base_address);
+               sg_dma_address(sg) = bar_address;

Jason

Yes, you are correct of course, but what will happen Jason, If I will
add a call to dma_map_resource() like Christian said ?
Won't that solve that specific issue ?
That's why I want to try it...

Oded