Re: [PATCH v7 00/21] Move all drivers to a common dma-buf locking convention

[Christian König]

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.