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Date:   Tue, 18 Oct 2022 13:34:14 +0200
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Subject: Re: [PATCH v7 00/21] Move all drivers to a common dma-buf locking
 convention
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To:     Dmitry Osipenko <dmitry.osipenko@collabora.com>,
        David Airlie <airlied@linux.ie>,
        Gerd Hoffmann <kraxel@redhat.com>,
        Gurchetan Singh <gurchetansingh@chromium.org>,
        Chia-I Wu <olvaffe@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
        Daniel Almeida <daniel.almeida@collabora.com>,
        Gert Wollny <gert.wollny@collabora.com>,
        Gustavo Padovan <gustavo.padovan@collabora.com>,
        Daniel Stone <daniel@fooishbar.org>,
        Tomeu Vizoso <tomeu.vizoso@collabora.com>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Rob Clark <robdclark@gmail.com>,
        Sumit Semwal <sumit.semwal@linaro.org>,
        "Pan, Xinhui" <Xinhui.Pan@amd.com>,
        Thierry Reding <thierry.reding@gmail.com>,
        Tomasz Figa <tfiga@chromium.org>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Alex Deucher <alexander.deucher@amd.com>,
        Jani Nikula <jani.nikula@linux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
        =?UTF-8?Q?Thomas_Hellstr=c3=b6m?= <thomas_os@shipmail.org>,
        Qiang Yu <yuq825@gmail.com>,
        Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
        Amol Maheshwari <amahesh@qti.qualcomm.com>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        Leon Romanovsky <leon@kernel.org>,
        Juergen Gross <jgross@suse.com>,
        Stefano Stabellini <sstabellini@kernel.org>,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>,
        Tomi Valkeinen <tomba@kernel.org>,
        Russell King <linux@armlinux.org.uk>,
        Lucas Stach <l.stach@pengutronix.de>,
        Christian Gmeiner <christian.gmeiner@gmail.com>,
        Ruhl Michael J <michael.j.ruhl@intel.com>
Cc:     dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        Dmitry Osipenko <digetx@gmail.com>,
        linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org,
        amd-gfx@lists.freedesktop.org, intel-gfx@lists.freedesktop.org,
        kernel@collabora.com, virtualization@lists.linux-foundation.org,
        linux-rdma@vger.kernel.org, linux-arm-msm@vger.kernel.org
References: <20221017172229.42269-1-dmitry.osipenko@collabora.com>
 <d943fec8-a1ef-faa5-4132-c7618acb891f@collabora.com>
From:   =?UTF-8?Q?Christian_K=c3=b6nig?= <christian.koenig@amd.com>
In-Reply-To: <d943fec8-a1ef-faa5-4132-c7618acb891f@collabora.com>
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Am 18.10.22 um 01:07 schrieb Dmitry Osipenko:
> On 10/17/22 20:22, Dmitry Osipenko wrote:
>> Hello,
>>
>> This series moves all drivers to a dynamic dma-buf locking specification.
>>  From now on all dma-buf importers are made responsible for holding
>> dma-buf's reservation lock around all operations performed over dma-bufs
>> in accordance to the locking specification. This allows us to utilize
>> reservation lock more broadly around kernel without fearing of a potential
>> deadlocks.
>>
>> This patchset passes all i915 selftests. It was also tested using VirtIO,
>> Panfrost, Lima, Tegra, udmabuf, AMDGPU and Nouveau drivers. I tested cases
>> of display+GPU, display+V4L and GPU+V4L dma-buf sharing (where appropriate),
>> which covers majority of kernel drivers since rest of the drivers share
>> same or similar code paths.
>>
>> Changelog:
>>
>> v7: - Rebased on top of recent drm-misc-next.
>>
>>      - Added ack from Jason Gunthorpe to the RDMA patch.
>>
>>      - Added iosys_map_clear() to dma_buf_vmap_unlocked(), making it fully
>>        consistent with dma_buf_vmap().
>>
>> v6: - Added r-b from Michael Ruhl to the i915 patch.
>>
>>      - Added acks from Sumit Semwal and updated commit message of the
>>        "Move dma_buf_vmap() to dynamic locking specification" patch like
>>        was suggested by Sumit.
>>
>>      - Added "!dmabuf" check to dma_buf_vmap_unlocked() to match the locked
>>        variant of the function, for consistency.
>>
>> v5: - Added acks and r-bs that were given to v4.
>>
>>      - Changed i915 preparation patch like was suggested by Michael Ruhl.
>>        The scope of reservation locking is smaller now.
>>
>> v4: - Added dma_buf_mmap() to the "locking convention" documentation,
>>        which was missed by accident in v3.
>>
>>      - Added acks from Christian König, Tomasz Figa and Hans Verkuil that
>>        they gave to couple v3 patches.
>>
>>      - Dropped the "_unlocked" postfix from function names that don't have
>>        the locked variant, as was requested by Christian König.
>>
>>      - Factored out the per-driver preparations into separate patches
>>        to ease reviewing of the changes, which is now doable without the
>>        global dma-buf functions renaming.
>>
>>      - Factored out the dynamic locking convention enforcements into separate
>>        patches which add the final dma_resv_assert_held(dmabuf->resv) to the
>>        dma-buf API functions.
>>
>> v3: - Factored out dma_buf_mmap_unlocked() and attachment functions
>>        into aseparate patches, like was suggested by Christian König.
>>
>>      - Corrected and factored out dma-buf locking documentation into
>>        a separate patch, like was suggested by Christian König.
>>
>>      - Intel driver dropped the reservation locking fews days ago from
>>        its BO-release code path, but we need that locking for the imported
>>        GEMs because in the end that code path unmaps the imported GEM.
>>        So I added back the locking needed by the imported GEMs, updating
>>        the "dma-buf attachment locking specification" patch appropriately.
>>
>>      - Tested Nouveau+Intel dma-buf import/export combo.
>>
>>      - Tested udmabuf import to i915/Nouveau/AMDGPU.
>>
>>      - Fixed few places in Etnaviv, Panfrost and Lima drivers that I missed
>>        to switch to locked dma-buf vmapping in the drm/gem: Take reservation
>>        lock for vmap/vunmap operations" patch. In a result invalidated the
>>        Christian's r-b that he gave to v2.
>>
>>      - Added locked dma-buf vmap/vunmap functions that are needed for fixing
>>        vmappping of Etnaviv, Panfrost and Lima drivers mentioned above.
>>        I actually had this change stashed for the drm-shmem shrinker patchset,
>>        but then realized that it's already needed by the dma-buf patches.
>>        Also improved my tests to better cover these code paths.
>>
>> v2: - Changed locking specification to avoid problems with a cross-driver
>>        ww locking, like was suggested by Christian König. Now the attach/detach
>>        callbacks are invoked without the held lock and exporter should take the
>>        lock.
>>
>>      - Added "locking convention" documentation that explains which dma-buf
>>        functions and callbacks are locked/unlocked for importers and exporters,
>>        which was requested by Christian König.
>>
>>      - Added ack from Tomasz Figa to the V4L patches that he gave to v1.
>>
>> Dmitry Osipenko (21):
>>    dma-buf: Add unlocked variant of vmapping functions
>>    dma-buf: Add unlocked variant of attachment-mapping functions
>>    drm/gem: Take reservation lock for vmap/vunmap operations
>>    drm/prime: Prepare to dynamic dma-buf locking specification
>>    drm/armada: Prepare to dynamic dma-buf locking specification
>>    drm/i915: Prepare to dynamic dma-buf locking specification
>>    drm/omapdrm: Prepare to dynamic dma-buf locking specification
>>    drm/tegra: Prepare to dynamic dma-buf locking specification
>>    drm/etnaviv: Prepare to dynamic dma-buf locking specification
>>    RDMA/umem: Prepare to dynamic dma-buf locking specification
>>    misc: fastrpc: Prepare to dynamic dma-buf locking specification
>>    xen/gntdev: Prepare to dynamic dma-buf locking specification
>>    media: videobuf2: Prepare to dynamic dma-buf locking specification
>>    media: tegra-vde: Prepare to dynamic dma-buf locking specification
>>    dma-buf: Move dma_buf_vmap() to dynamic locking specification
>>    dma-buf: Move dma_buf_attach() to dynamic locking specification
>>    dma-buf: Move dma_buf_map_attachment() to dynamic locking
>>      specification
>>    dma-buf: Move dma_buf_mmap() to dynamic locking specification
>>    dma-buf: Document dynamic locking convention
>>    media: videobuf2: Stop using internal dma-buf lock
>>    dma-buf: Remove obsoleted internal lock
>>
>>   Documentation/driver-api/dma-buf.rst          |   6 +
>>   drivers/dma-buf/dma-buf.c                     | 216 +++++++++++++++---
>>   drivers/gpu/drm/armada/armada_gem.c           |   8 +-
>>   drivers/gpu/drm/drm_client.c                  |   4 +-
>>   drivers/gpu/drm/drm_gem.c                     |  24 ++
>>   drivers/gpu/drm/drm_gem_dma_helper.c          |   6 +-
>>   drivers/gpu/drm/drm_gem_framebuffer_helper.c  |   6 +-
>>   drivers/gpu/drm/drm_gem_ttm_helper.c          |   9 +-
>>   drivers/gpu/drm/drm_prime.c                   |   6 +-
>>   drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c   |   2 +-
>>   drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c    |   2 +-
>>   drivers/gpu/drm/i915/gem/i915_gem_object.c    |  14 ++
>>   .../drm/i915/gem/selftests/i915_gem_dmabuf.c  |  16 +-
>>   drivers/gpu/drm/lima/lima_sched.c             |   4 +-
>>   drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c     |   4 +-
>>   drivers/gpu/drm/panfrost/panfrost_dump.c      |   4 +-
>>   drivers/gpu/drm/panfrost/panfrost_perfcnt.c   |   6 +-
>>   drivers/gpu/drm/qxl/qxl_object.c              |  17 +-
>>   drivers/gpu/drm/qxl/qxl_prime.c               |   4 +-
>>   drivers/gpu/drm/tegra/gem.c                   |  17 +-
>>   drivers/infiniband/core/umem_dmabuf.c         |   7 +-
>>   .../common/videobuf2/videobuf2-dma-contig.c   |  22 +-
>>   .../media/common/videobuf2/videobuf2-dma-sg.c |  19 +-
>>   .../common/videobuf2/videobuf2-vmalloc.c      |  17 +-
>>   .../platform/nvidia/tegra-vde/dmabuf-cache.c  |   6 +-
>>   drivers/misc/fastrpc.c                        |   6 +-
>>   drivers/xen/gntdev-dmabuf.c                   |   8 +-
>>   include/drm/drm_gem.h                         |   3 +
>>   include/linux/dma-buf.h                       |  17 +-
>>   29 files changed, 325 insertions(+), 155 deletions(-)
>>
> Applied to drm-misc-next

Finally! Fingers crossed that all corner cases where fixed during the 
review.

But if anything shows up feel free to loop me in to help fixing things.

Thanks a lot for doing this,
Christian.