[PATCH v6 0/5] Use new dma-map IOVA alloc, link, and sync API in GPU SVM and DRM pagemap

Matthew Brost
2026-04-08T20:15:46Z

The dma-map IOVA alloc, link, and sync APIs perform significantly better
than dma-map / dma-unmap, as they avoid costly IOMMU synchronizations.
This difference is especially noticeable when mapping a 2MB region in
4KB pages.

Use dma-map IOVA alloc, link, and sync APIs for GPU SVM and DRM page,
which mappings between the CPU and GPU.

Initial results are promising.

Baseline CPU time during 2M / 64K fault with a migration (device THP disabled):
Average migrate 2M cpu time (us, percentage): 333.99665178571428571429, .61102853199282922865
Average migrate 64K cpu time (us, percentage): 18.62723214285714285714, .30127985269960467173

After this series CPU time during 2M / 64K fault with a migration (device THP disabled):
Average migrate 2M cpu time (us, percentage): 224.81808035714285714286, .51412827364772602557
Average migrate 64K cpu time (us, percentage): 14.65625000000000000000, .25659463050529524405

Matt

v2:
- Include missing basline patch for CI
v3:
- Fix memory corruption
- PoC IOVA alloc for multi-GPU
v4:
- Pack IOVA / drop dummy pages
- Drop multi-GPU IOVA alloc
v5:
- Address Thomas's comments
v6:
- Address Francois's comments

Matthew Brost (5):
drm/gpusvm: Use dma-map IOVA alloc, link, and sync API in GPU SVM
drm/pagemap: Drop source_peer_migrates flag and assume true
drm/pagemap: Split drm_pagemap_migrate_map_pages into device / system
drm/pagemap: Use dma-map IOVA alloc, link, and sync API for DRM
pagemap
drm/pagemap: Fix drm_pagemap_migrate_unmap_pages kerneldoc

drivers/gpu/drm/drm_gpusvm.c | 55 ++++++--
drivers/gpu/drm/drm_pagemap.c | 229 ++++++++++++++++++++++++----------
drivers/gpu/drm/xe/xe_svm.c | 1 -
include/drm/drm_gpusvm.h | 5 +
include/drm/drm_pagemap.h | 9 +-
5 files changed, 220 insertions(+), 79 deletions(-)

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2.34.1