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Date:   Wed, 24 Aug 2022 16:15:00 +0200
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Subject: Re: [PATCH v3 0/9] 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>
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,
        lima@lists.freedesktop.org
References: <20220824102248.91964-1-dmitry.osipenko@collabora.com>
From:   =?UTF-8?Q?Christian_K=c3=b6nig?= <ckoenig.leichtzumerken@gmail.com>
In-Reply-To: <20220824102248.91964-1-dmitry.osipenko@collabora.com>
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Reviewed-by: Christian König <christian.koenig@amd.com> to patches #2-#4

Am 24.08.22 um 12:22 schrieb Dmitry Osipenko:
> 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:
>
> 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 (9):
>    dma-buf: Add _unlocked postfix to function names
>    dma-buf: Add locked variant of dma_buf_vmap/vunmap()
>    drm/gem: Take reservation lock for vmap/vunmap operations
>    dma-buf: Move dma_buf_vmap/vunmap_unlocked() to dynamic locking
>      specification
>    dma-buf: Move dma_buf_mmap_unlocked() to dynamic locking specification
>    dma-buf: Move dma-buf attachment to dynamic locking specification
>    dma-buf: Document dynamic locking convention
>    media: videobuf2: Stop using internal dma-buf lock
>    dma-buf: Remove internal lock
>
>   Documentation/driver-api/dma-buf.rst          |   6 +
>   drivers/dma-buf/dma-buf.c                     | 276 ++++++++++++++----
>   drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c   |   4 +-
>   drivers/gpu/drm/armada/armada_gem.c           |  14 +-
>   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_shmem_helper.c        |   2 +-
>   drivers/gpu/drm/drm_gem_ttm_helper.c          |   9 +-
>   drivers/gpu/drm/drm_prime.c                   |  12 +-
>   drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c   |   4 +-
>   drivers/gpu/drm/exynos/exynos_drm_gem.c       |   2 +-
>   drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c    |   6 +-
>   drivers/gpu/drm/i915/gem/i915_gem_object.c    |  12 +
>   .../drm/i915/gem/selftests/i915_gem_dmabuf.c  |  20 +-
>   drivers/gpu/drm/lima/lima_sched.c             |   4 +-
>   drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c     |   8 +-
>   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                   |  27 +-
>   drivers/infiniband/core/umem_dmabuf.c         |  11 +-
>   .../common/videobuf2/videobuf2-dma-contig.c   |  26 +-
>   .../media/common/videobuf2/videobuf2-dma-sg.c |  23 +-
>   .../common/videobuf2/videobuf2-vmalloc.c      |  17 +-
>   .../platform/nvidia/tegra-vde/dmabuf-cache.c  |  12 +-
>   drivers/misc/fastrpc.c                        |  12 +-
>   drivers/xen/gntdev-dmabuf.c                   |  14 +-
>   include/drm/drm_gem.h                         |   3 +
>   include/linux/dma-buf.h                       |  57 ++--
>   32 files changed, 410 insertions(+), 242 deletions(-)
>