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Date:   Tue, 22 Jun 2021 12:28:27 -0300
From:   Jason Gunthorpe <jgg@ziepe.ca>
To:     Christian =?utf-8?B?S8O2bmln?= <christian.koenig@amd.com>
Cc:     Oded Gabbay <oded.gabbay@gmail.com>,
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Subject: Re: [Linaro-mm-sig] [PATCH v3 1/2] habanalabs: define uAPI to export
 FD for DMA-BUF
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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