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
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
