linux-kernel - Re: [PATCH v4 0/2] Add p2p via dmabuf to habanalabs

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Date:   Tue, 6 Jul 2021 10:40:37 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Oded Gabbay <ogabbay@...nel.org>
Cc:     linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
        sumit.semwal@...aro.org, christian.koenig@....com,
        daniel.vetter@...ll.ch, galpress@...zon.com, sleybo@...zon.com,
        dri-devel@...ts.freedesktop.org, jgg@...pe.ca,
        linux-rdma@...r.kernel.org, linux-media@...r.kernel.org,
        dledford@...hat.com, airlied@...il.com, alexander.deucher@....com,
        leonro@...dia.com, hch@....de, amd-gfx@...ts.freedesktop.org,
        linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH v4 0/2] Add p2p via dmabuf to habanalabs

On Mon, Jul 05, 2021 at 04:03:12PM +0300, Oded Gabbay wrote:
> Hi,
> I'm sending v4 of this patch-set following the long email thread.
> I want to thank Jason for reviewing v3 and pointing out the errors, saving
> us time later to debug it :)
> 
> I consulted with Christian on how to fix patch 2 (the implementation) and
> at the end of the day I shamelessly copied the relevant content from
> amdgpu_vram_mgr_alloc_sgt() and amdgpu_dma_buf_attach(), regarding the
> usage of dma_map_resource() and pci_p2pdma_distance_many(), respectively.
> 
> I also made a few improvements after looking at the relevant code in amdgpu.
> The details are in the changelog of patch 2.
> 
> I took the time to write an import code into the driver, allowing me to
> check real P2P with two Gaudi devices, one as exporter and the other as
> importer. I'm not going to include the import code in the product, it was
> just for testing purposes (although I can share it if anyone wants).
> 
> I run it on a bare-metal environment with IOMMU enabled, on a sky-lake CPU
> with a white-listed PCIe bridge (to make the pci_p2pdma_distance_many happy).
> 
> Greg, I hope this will be good enough for you to merge this code.

So we're officially going to use dri-devel for technical details review
and then Greg for merging so we don't have to deal with other merge
criteria dri-devel folks have?

I don't expect anything less by now, but it does make the original claim
that drivers/misc will not step all over accelerators folks a complete
farce under the totally-not-a-gpu banner.

This essentially means that for any other accelerator stack that doesn't
fit the dri-devel merge criteria, even if it's acting like a gpu and uses
other gpu driver stuff, you can just send it to Greg and it's good to go.

There's quite a lot of these floating around actually (and many do have
semi-open runtimes, like habanalabs have now too, just not open enough to
be actually useful). It's going to be absolutely lovely having to explain
to these companies in background chats why habanalabs gets away with their
stack and they don't.

Or maybe we should just merge them all and give up on the idea of having
open cross-vendor driver stacks for these accelerators.

Thanks, Daniel

> 
> Thanks,
> Oded
> 
> Oded Gabbay (1):
>   habanalabs: define uAPI to export FD for DMA-BUF
> 
> Tomer Tayar (1):
>   habanalabs: add support for dma-buf exporter
> 
>  drivers/misc/habanalabs/Kconfig             |   1 +
>  drivers/misc/habanalabs/common/habanalabs.h |  26 ++
>  drivers/misc/habanalabs/common/memory.c     | 480 +++++++++++++++++++-
>  drivers/misc/habanalabs/gaudi/gaudi.c       |   1 +
>  drivers/misc/habanalabs/goya/goya.c         |   1 +
>  include/uapi/misc/habanalabs.h              |  28 +-
>  6 files changed, 532 insertions(+), 5 deletions(-)
> 
> -- 
> 2.25.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch