linux-kernel - Re: [PATCH 0/8] xen: dma-buf support for grant device

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Message-ID: <00c0eabc-3a5e-5335-5a7e-2cebce5387c9@oracle.com>
Date:   Thu, 31 May 2018 16:25:02 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Oleksandr Andrushchenko <andr2000@...il.com>,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-media@...r.kernel.org,
        jgross@...e.com, konrad.wilk@...cle.com
Cc:     daniel.vetter@...el.com, dongwon.kim@...el.com,
        matthew.d.roper@...el.com,
        Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>
Subject: Re: [PATCH 0/8] xen: dma-buf support for grant device

On 05/31/2018 10:41 AM, Oleksandr Andrushchenko wrote:
> On 05/31/2018 08:51 AM, Oleksandr Andrushchenko wrote:
>> On 05/31/2018 04:46 AM, Boris Ostrovsky wrote:
>>>
>>>
>>> On 05/25/2018 11:33 AM, Oleksandr Andrushchenko wrote:
>>>
>>>>
>>>> Oleksandr Andrushchenko (8):
>>>>    xen/grant-table: Make set/clear page private code shared
>>>>    xen/balloon: Move common memory reservation routines to a module
>>>>    xen/grant-table: Allow allocating buffers suitable for DMA
>>>>    xen/gntdev: Allow mappings for DMA buffers
>>>>    xen/gntdev: Add initial support for dma-buf UAPI
>>>>    xen/gntdev: Implement dma-buf export functionality
>>>>    xen/gntdev: Implement dma-buf import functionality
>>>>    xen/gntdev: Expose gntdev's dma-buf API for in-kernel use
>>>>
>>>>   drivers/xen/Kconfig           |   23 +
>>>>   drivers/xen/Makefile          |    1 +
>>>>   drivers/xen/balloon.c         |   71 +--
>>>>   drivers/xen/gntdev.c          | 1025
>>>> ++++++++++++++++++++++++++++++++-
>>>
>>>
>>> I think this calls for gntdev_dma.c.
>> I assume you mean as a separate file (part of gntdev driver)?
>>> I only had a quick look over gntdev changes but they very much are
>>> concentrated in dma-specific routines.
>>>
>> I tried to do that, but there are some dependencies between the
>> gntdev.c and gntdev_dma.c,
>> so finally I decided to put it all together.
>>> You essentially only share file_operations entry points with
>>> original gntdev code, right?
>>>
>> fops + mappings done by gntdev (struct grant_map) and I need to
>> release map on dma_buf .release
>> callback which makes some cross-dependencies between modules which
>> seemed to be not cute
>> (gntdev keeps its all structs and functions inside, so I cannot
>> easily access those w/o
>> helpers).
>>
>> But I'll try one more time and move all DMA specific stuff into
>> gntdev_dma.c
> Could you please take a quick look at the way I re-structured the
> sources here [1]?
> If this is what you meant.


I looked at final gntdev.c code and I think at least one of the chunks
there ("DMA buffer export support. ") can also be moved out. It still
have a bit too many ifdefs but it looks better to my eye than jamming
everything into a single file (and I think more code can be moved out,
but we can talk about it when you post the patches so that we can see
context).

BTW, I believe it won't build with !CONFIG_XEN_GNTDEV_DMABUF ---
gntdev_remove_map() is defined under this option and is referenced later
without it.


-boris


>
> Thank you,
> Oleksandr
>>> -boris
>>>
>> Thank you,
>> Oleksandr
>>>
>>>>   drivers/xen/grant-table.c     |  176 +++++-
>>>>   drivers/xen/mem-reservation.c |  134 +++++
>>>>   include/uapi/xen/gntdev.h     |  106 ++++
>>>>   include/xen/grant_dev.h       |   37 ++
>>>>   include/xen/grant_table.h     |   28 +
>>>>   include/xen/mem_reservation.h |   29 +
>>>>   10 files changed, 1527 insertions(+), 103 deletions(-)
>>>>   create mode 100644 drivers/xen/mem-reservation.c
>>>>   create mode 100644 include/xen/grant_dev.h
>>>>   create mode 100644 include/xen/mem_reservation.h
>>>>
>>
> [1]
> https://github.com/andr2000/linux/commits/xen_tip_linux_next_xen_dma_buf_v2