Re: [PATCH v3 0/9] Move all drivers to a common dma-buf locking convention

Christian König
2022-08-24T14:15:11Z

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(-)
>