[RFC 00/11] THP support for zone device pages

[Balbir Singh]

This patch series adds support for THP migration of zone device pages.
To do so, the patches implement support for folio zone device pages
by adding support for setting up larger order pages.

These patches build on the earlier posts by Ralph Campbell [1]

Two new flags are added in vma_migration to select and mark compound pages.
migrate_vma_setup(), migrate_vma_pages() and migrate_vma_finalize()
support migration of these pages when MIGRATE_VMA_SELECT_COMPOUND
is passed in as arguments.

The series also adds zone device awareness to (m)THP pages along
with fault handling of large zone device private pages. page vma walk
and the rmap code is also zone device aware. Support has also been
added for folios that might need to be split in the middle
of migration (when the src and dst do not agree on
MIGRATE_PFN_COMPOUND), that occurs when src side of the migration can
migrate large pages, but the destination has not been able to allocate
large pages. The code supported and used folio_split() when migrating
THP pages, this is used when MIGRATE_VMA_SELECT_COMPOUND is not passed
as an argument to migrate_vma_setup().

The test infrastructure lib/test_hmm.c has been enhanced to support THP
migration. A new ioctl to emulate failure of large page allocations has
been added to test the folio split code path. hmm-tests.c has new test
cases for huge page migration and to test the folio split path.

The nouveau dmem code has been enhanced to use the new THP migration
capability.

mTHP support:

The patches hard code, HPAGE_PMD_NR in a few places, but the code has
been kept generic to support various order sizes. With additional
refactoring of the code support of different order sizes should be
possible.

References:
[1] https://lore.kernel.org/linux-mm/20201106005147.20113-1-rcampbell@nvidia.com/

These patches are built on top of mm-everything-2025-03-04-05-51

Cc: Karol Herbst <kherbst at redhat.com>
Cc: Lyude Paul <lyude at redhat.com>
Cc: Danilo Krummrich <dakr at kernel.org>
Cc: David Airlie <airlied at gmail.com>
Cc: Simona Vetter <simona at ffwll.ch>
Cc: "Jérôme Glisse" <jglisse at redhat.com>
Cc: Shuah Khan <shuah at kernel.org>
Cc: David Hildenbrand <david at redhat.com>
Cc: Barry Song <baohua at kernel.org>
Cc: Baolin Wang <baolin.wang at linux.alibaba.com>
Cc: Ryan Roberts <ryan.roberts at arm.com>
Cc: Matthew Wilcox <willy at infradead.org>
Cc: Peter Xu <peterx at redhat.com>
Cc: Zi Yan <ziy at nvidia.com>
Cc: Kefeng Wang <wangkefeng.wang at huawei.com>
Cc: Jane Chu <jane.chu at oracle.com>
Cc: Alistair Popple <apopple at nvidia.com>
Cc: Donet Tom <donettom at linux.ibm.com>

Balbir Singh (11):
  mm/zone_device: support large zone device private folios
  mm/migrate_device: flags for selecting device private THP pages
  mm/thp: zone_device awareness in THP handling code
  mm/migrate_device: THP migration of zone device pages
  mm/memory/fault: Add support for zone device THP fault handling
  lib/test_hmm: test cases and support for zone device private THP
  mm/memremap: Add folio_split support
  mm/thp: add split during migration support
  lib/test_hmm: add test case for split pages
  selftests/mm/hmm-tests: new tests for zone device THP migration
  gpu/drm/nouveau: Add THP migration support

 drivers/gpu/drm/nouveau/nouveau_dmem.c | 244 +++++++++----
 drivers/gpu/drm/nouveau/nouveau_svm.c  |   6 +-
 drivers/gpu/drm/nouveau/nouveau_svm.h  |   3 +-
 include/linux/huge_mm.h                |  18 +-
 include/linux/memremap.h               |  29 +-
 include/linux/migrate.h                |   2 +
 include/linux/mm.h                     |   1 +
 lib/test_hmm.c                         | 387 ++++++++++++++++----
 lib/test_hmm_uapi.h                    |   3 +
 mm/huge_memory.c                       | 242 +++++++++---
 mm/memory.c                            |   6 +-
 mm/memremap.c                          |  50 ++-
 mm/migrate.c                           |   2 +
 mm/migrate_device.c                    | 488 +++++++++++++++++++++----
 mm/page_alloc.c                        |   1 +
 mm/page_vma_mapped.c                   |  10 +
 mm/rmap.c                              |  19 +-
 tools/testing/selftests/mm/hmm-tests.c | 407 +++++++++++++++++++++
 18 files changed, 1630 insertions(+), 288 deletions(-)

-- 
2.48.1