linux-toradex.git/include/drm/drm_pagemap_util.h, branch v7.2-rc5 Linux kernel for Apalis and Colibri modules drm/pagemap_util: Add a utility to assign an owner to a set of interconnected gpus 2025-12-23T09:00:47+00:00 Thomas Hellström thomas.hellstrom@linux.intel.com 2025-12-19T11:33:06+00:00 e44f47a9bf5104c9b9efcc8fc95a858c66f2d1e6 The hmm_range_fault() and the migration helpers currently need a common "owner" to identify pagemaps and clients with fast interconnect. Add a drm_pagemap utility to setup such owners by registering drm_pagemaps, in a registry, and for each new drm_pagemap, query which existing drm_pagemaps have fast interconnects with the new drm_pagemap. The "owner" scheme is limited in that it is static at drm_pagemap creation. Ideally one would want the owner to be adjusted at run-time, but that requires changes to hmm. If the proposed scheme becomes too limited, we need to revisit. v2: - Improve documentation of DRM_PAGEMAP_OWNER_LIST_DEFINE(). (Matt Brost) Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com> Reviewed-by: Matthew Brost <matthew.brost@intel.com> Acked-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> # For merging through drm-xe. Link: https://patch.msgid.link/20251219113320.183860-11-thomas.hellstrom@linux.intel.com 
The hmm_range_fault() and the migration helpers currently need a common
"owner" to identify pagemaps and clients with fast interconnect.
Add a drm_pagemap utility to setup such owners by registering
drm_pagemaps, in a registry, and for each new drm_pagemap,
query which existing drm_pagemaps have fast interconnects with the new
drm_pagemap.

The "owner" scheme is limited in that it is static at drm_pagemap creation.
Ideally one would want the owner to be adjusted at run-time, but that
requires changes to hmm. If the proposed scheme becomes too limited,
we need to revisit.

v2:
- Improve documentation of DRM_PAGEMAP_OWNER_LIST_DEFINE(). (Matt Brost)

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Acked-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> # For merging through drm-xe.
Link: https://patch.msgid.link/20251219113320.183860-11-thomas.hellstrom@linux.intel.com
drm/pagemap: Add a drm_pagemap cache and shrinker 2025-12-23T08:37:33+00:00 Thomas Hellström thomas.hellstrom@linux.intel.com 2025-12-19T11:33:03+00:00 77f14f2f2d73f6955b856e7c91ca9fb7046da191 Pagemaps are costly to set up and tear down, and they consume a lot of system memory for the struct pages. Ideally they should be created only when needed. Add a caching mechanism to allow doing just that: Create the drm_pagemaps when needed for migration. Keep them around to avoid destruction and re-creation latencies and destroy inactive/unused drm_pagemaps on memory pressure using a shrinker. Only add the helper functions. They will be hooked up to the xe driver in the upcoming patch. v2: - Add lockdep checking for drm_pagemap_put(). (Matt Brost) - Add a copyright notice. (Matt Brost) Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com> Reviewed-by: Matthew Brost <matthew.brost@intel.com> Acked-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> # For merging through drm-xe. Link: https://patch.msgid.link/20251219113320.183860-8-thomas.hellstrom@linux.intel.com 
Pagemaps are costly to set up and tear down, and they consume a lot
of system memory for the struct pages. Ideally they should be
created only when needed.

Add a caching mechanism to allow doing just that: Create the drm_pagemaps
when needed for migration. Keep them around to avoid destruction and
re-creation latencies and destroy inactive/unused drm_pagemaps on memory
pressure using a shrinker.

Only add the helper functions. They will be hooked up to the xe driver
in the upcoming patch.

v2:
- Add lockdep checking for drm_pagemap_put(). (Matt Brost)
- Add a copyright notice. (Matt Brost)

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Acked-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> # For merging through drm-xe.
Link: https://patch.msgid.link/20251219113320.183860-8-thomas.hellstrom@linux.intel.com