Re: [Linaro-mm-sig] [PATCH v3 1/2] habanalabs: define uAPI to export FD for DMA-BUF

[Jason Gunthorpe]

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

> > > 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