[PATCH v2 0/7] drm/vram-helper: Lock GEM BOs while they are mapped

[Thomas Zimmermann]

Am 03.12.20 um 15:02 schrieb Thomas Zimmermann:
> GEM VRAM helpers used to pin the BO in their implementation of vmap, so
> that they could not be relocated. In a recent discussion, [1] it became

Grrr, [1] was again supposed to point to the discussion at

   https://patchwork.freedesktop.org/patch/400054/?series=83765&rev=1

> clear that this is incorrect and that vmap should rather repend on the
> reservation lock to prevent relocation. This patchset addresses the issue.
> 
> Version 2 of the patchset is a significant rework. In particular, the
> helper function drm_gem_vram_vmap_unlocked() is gone and importers now
> acquire the reservation locks by themselves. I took Christian's A-bs only
> for patches that were not affected.
> 
> Patches 1 and 2 prepare the ast cursor code for the later changes.
> 
> Patch 3 pushes the BO locking into callers of vmap and vunmap. Besides
> the VRAM helpers, this affects ast, vboxvideo and the generic fbdev
> emulation.
> 
> Patches 4 to 6 clean up afterwards. BO pinning is not required any longer
> and the VRAM-internal helpers are not needed.
> 
> Patch 7 adds documentation to vmap and vunmap in struct dma_buf_ops. It
> hopefully reflects the discussion on the patchset's version 1.
> 
> Tested on ast with GEM VRAM and also on mgag200 to verify that the fbdev
> change does not interfere with GEM SHMEM.
> 
> v2:
> 	* make importers acquire resv locks by themselves
> 	* document dma-buf vamp/vunmap ops
> 
> Thomas Zimmermann (7):
>    drm/ast: Don't pin cursor source BO explicitly during update
>    drm/ast: Only map cursor BOs during updates
>    drm/vram-helper: Move BO locking from vmap code into callers
>    drm/vram-helper: Remove pinning from drm_gem_vram_{vmap,vunmap}()
>    drm/vram-helper: Remove vmap reference counting
>    drm/vram-helper: Simplify vmap implementation
>    dma-buf: Write down some rules for vmap usage
> 
>   Documentation/gpu/todo.rst            | 15 +++++
>   drivers/gpu/drm/ast/ast_cursor.c      | 70 +++++++++++++---------
>   drivers/gpu/drm/ast/ast_drv.h         |  2 -
>   drivers/gpu/drm/drm_client.c          | 31 ++++++++++
>   drivers/gpu/drm/drm_fb_helper.c       | 10 +++-
>   drivers/gpu/drm/drm_gem_vram_helper.c | 85 ++++++---------------------
>   drivers/gpu/drm/vboxvideo/vbox_mode.c | 11 ++--
>   include/drm/drm_client.h              |  2 +
>   include/drm/drm_gem.h                 |  4 ++
>   include/drm/drm_gem_vram_helper.h     | 17 +-----
>   include/linux/dma-buf.h               | 45 ++++++++++++++
>   11 files changed, 175 insertions(+), 117 deletions(-)
> 
> --
> 2.29.2
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer

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