drm/xe: Strict migration policy for atomic SVM faults

Mixing GPU and CPU atomics does not work unless a strict migration
policy of GPU atomics must be device memory. Enforce a policy of must be
in VRAM with a retry loop of 3 attempts, if retry loop fails abort
fault.

Removing always_migrate_to_vram modparam as we now have real migration
policy.

v2:
 - Only retry migration on atomics
 - Drop alway migrate modparam
v3:
 - Only set vram_only on DGFX (Himal)
 - Bail on get_pages failure if vram_only and retry count exceeded (Himal)
 - s/vram_only/devmem_only
 - Update xe_svm_range_is_valid to accept devmem_only argument
v4:
 - Fix logic bug get_pages failure
v5:
 - Fix commit message (Himal)
 - Mention removing always_migrate_to_vram in commit message (Lucas)
 - Fix xe_svm_range_is_valid to check for devmem pages
 - Bail on devmem_only && !migrate_devmem (Thomas)
v6:
 - Add READ_ONCE barriers for opportunistic checks (Thomas)
 - Pair READ_ONCE with WRITE_ONCE (Thomas)
v7:
 - Adjust comments (Thomas)

Fixes: 2f118c949160 ("drm/xe: Add SVM VRAM migration")
Cc: [email protected]
Signed-off-by: Himal Prasad Ghimiray <[email protected]>
Signed-off-by: Matthew Brost <[email protected]>
Acked-by: Himal Prasad Ghimiray <[email protected]>
Reviewed-by: Thomas Hellström <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
(cherry picked from commit a9ac0fa455b050d03e3032501368048fb284d318)
Signed-off-by: Lucas De Marchi <[email protected]>

0 files changed, 0 insertions, 0 deletions