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In-Reply-To: <20210622152827.GQ1096940@ziepe.ca>
From:   Oded Gabbay <oded.gabbay@gmail.com>
Date:   Tue, 22 Jun 2021 18:31:04 +0300
Message-ID: <CAFCwf132jue+0ZOEd+3U-NPQuVt+ry1hz6FB=oZ4g_8J4pAqpw@mail.gmail.com>
Subject: Re: [Linaro-mm-sig] [PATCH v3 1/2] habanalabs: define uAPI to export
 FD for DMA-BUF
To:     Jason Gunthorpe <jgg@ziepe.ca>
Cc:     =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>,
        =?UTF-8?Q?Christian_K=C3=B6nig?= <ckoenig.leichtzumerken@gmail.com>,
        Gal Pressman <galpress@amazon.com>, sleybo@amazon.com,
        linux-rdma <linux-rdma@vger.kernel.org>,
        Oded Gabbay <ogabbay@kernel.org>,
        Christoph Hellwig <hch@lst.de>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        "moderated list:DMA BUFFER SHARING FRAMEWORK" 
        <linaro-mm-sig@lists.linaro.org>,
        Doug Ledford <dledford@redhat.com>,
        Tomer Tayar <ttayar@habana.ai>,
        amd-gfx list <amd-gfx@lists.freedesktop.org>,
        Greg KH <gregkh@linuxfoundation.org>,
        Alex Deucher <alexander.deucher@amd.com>,
        Leon Romanovsky <leonro@nvidia.com>,
        "open list:DMA BUFFER SHARING FRAMEWORK" 
        <linux-media@vger.kernel.org>
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On Tue, Jun 22, 2021 at 6:28 PM Jason Gunthorpe <jgg@ziepe.ca> wrote:
>
> On Tue, Jun 22, 2021 at 05:24:08PM +0200, Christian K=C3=B6nig 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 re=
al
> > > > 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 configuratio=
n
> > > 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 =3D hdev->dram_pci_bar_start +
> +                               (pages[cur_page] - prop->dram_base_addres=
s);
> +               sg_dma_address(sg) =3D 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