[PATCH v3 0/6] drm/gem-shmem: Track page accessed/dirty status

[Thomas Zimmermann <tzimmermann@suse.de>]

Track page access/dirty status in gem-shmem for better integration with
the overall memory management. Gem-shmem has long had two flag bits in
struct drm_gem_shmem_object, named pages_mark_accessed_on_put and
pages_mark_dirty_on_put, but never used them much; except for some odd
cases in drivers. Therefore pages in gem-shmem where never marked
correctly. (Other DRM memory managers do some course-grain tracking at
least).

Patches 1 to 4 prepare the mmap page-fault handler for tracking page
status easily. The pages are already available; only the mmap handling
needs to be adapted. The way the shmem code interacts with huge-page
support is also not optimal, hence refactor it slightly.

Patch 5 adds tracking access and dirty status in mmap. With the earlier
patches, this change simply falls into place.

Patch 6 adds tracking access and dirty status in vmap. Because there's
no fault handling here, we refer to the existing status bits in struct
drm_gem_shmem_object. Each page's status will be updated by the page
release in drm_gem_put_pages(). The imagination driver requires a small
fix to make it work correctly.

Tested with CONFIG_VM=y by running animations on DRM's bochs driver for
several hours. This uses gem-shmem's mmap and vmap extensively.

v3:
- rewrite for VM_PFNMAP
- do more preparational patches
v2:
- fix possible OOB access into page array (Matthew)
- simplify fault-handler error handling (Boris)
- simplify internal interfaces (Matthew)

Thomas Zimmermann (6):
  drm/gem-shmem: Use obj directly where appropriate in fault handler
  drm/gem-shmem: Test for existence of page in mmap fault handler
  drm/gem-shmem: Return vm_fault_t from drm_gem_shmem_try_map_pmd()
  drm/gem-shmem: Refactor drm_gem_shmem_try_map_pmd()
  drm/gem-shmem: Track folio accessed/dirty status in mmap
  drm/gem-shmem: Track folio accessed/dirty status in vmap

 drivers/gpu/drm/drm_gem_shmem_helper.c | 77 ++++++++++++++++----------
 drivers/gpu/drm/imagination/pvr_gem.c  |  6 +-
 2 files changed, 53 insertions(+), 30 deletions(-)


base-commit: 0082025812a31eda451fb14f13f52683ed375c49
-- 
2.52.0